C-130 Broad Area Review
(January 1998)
TABLE OF CONTENTS
Tasking From The Secretary of the Air Force
The report you are about to read answers the Secretary of the Air Force’s direction to conduct a BAR of C-130 flight safety. Our goal was to make it understandable, by explaining or eliminating as much service jargon as possible. It represents our team’s review of C-130 aircraft systems, training programs, maintenance activities, and flying operations.
The Secretary of the Air Force, responding to a request from members of the United States Senate, tasked the Acting Chief of Staff of the United States Air Force to conduct a BAR of C-130 flight safety, addressing the missions and environments in which it flies, and its safety history. In addition, the Secretary directed the team to look at the King 56 incident to make certain all potential causes and contributing factors were properly considered, and to ensure that everything appropriate was being done to enhance C-130 flight safety.
Executive Summary
In response to the Secretary of the Air Force’s (SECAF) direction to form the team, the team chief selected a group of individuals with a broad background of experience in the C-130 weapon system. Representing a combined total of 45,000 flight hours and over 235 man-years experience with the aircraft, the team included operators and maintainers from the using commands (including the Air National Guard and Air Force Reserve Command), Air Force Safety Center, Air Force Materiel Command and Headquarters Air Mobility Command. There were members from logistics, operations, and the National Transportation Safety Board. Representatives of the aircraft’s manufacturer and major component suppliers (i.e., engine and propeller manufacturers) served as advisors to the team.
Our approach was simple and direct--get the right experts, get the facts (firsthand whenever possible, from the field operators and maintainers), determine safety issues within C-130 operations and maintenance (including training and aircraft systems, and aircraft safety data) identify possible scenarios for King 56, evaluate each, then report. To execute that approach, the BAR traveled to sixteen C-130 operating and maintenance locations across the country (Little Rock AFB, AR; Pope AFB, NC; Duke Field, FL; Hurlburt Field, FL, Moody AFB, GA; Keesler AFB, MS; Harrisburg ANG, PA; Warner-Robins ALC, GA; Kirtland AFB, NM; Davis-Monthan AFB, AZ; Youngstown ANG, OH; Dobbins AFB, GA; Lockheed-Martin Corporation, Marietta, GA; Moffett Field, CA; Schenectady, NY; and Portland ANG, OR), spoke with literally hundreds of crew members and maintainers, performed and analyzed tests, and read reports. The BAR also took leads from a toll free number that the BAR established to help us gather the information the BAR needed.
The team came away from this review convinced that the C-130 has been, and remains, a very safe and dependable aircraft. The team became increasingly aware of crew member suspicions that the aircraft’s synchrophaser (an electronic device used to synchronize the propellers and phase the passing of their blades as they turn so as to reduce propeller-induced noise and vibration), was to blame for King 56 and other engine power loss incidents. The team found that the internal failure of the synchrophaser was rarely the cause of the incidents examined (2 of 71). When involved, it turned out to be only a contributory factor to the problem, usually as a result of faulty signals fed from other systems, or by electromagnetic interference (EMI).
The BAR examined the C-130 fleet safety record and found that, in almost 25 million flight hours worldwide, there had not been a recorded instance before the King 56 accident where all four engines quit running in flight. The team reviewed data from multiple sources (including: contractor manuals, aircraft technical orders, safety and accident reports, and aircrew and maintenance interviews) and analyzed the information, as well as aircraft test results, at considerable length.
In the case of King 56’s uncommanded power-loss, the team believes the most likely explanation remains fuel starvation, due to one of several possible causes, each of which the BAR has evaluated in detail within the body of the report. Although the BAR believes it was fuel-related, no single specific cause could be conclusively determined. In this report, the BAR presents the scenarios that explain how this loss of fuel to the engines might have happened. The facts the BAR established, combined with test results referenced under each scenario, enabled the BAR to narrow the focus to four likely scenarios.
The Air Force published a safety supplement to change the flight manual emergency procedures for dealing with four-engine or multiple engine power-loss. Prior to publishing this report, the team drafted this bold face procedure which crews must commit to memory and use immediately in such an emergency to improve their odds of solving the problem before it becomes unrecoverable. The crews exposed to this procedure overwhelmingly approved of it and were quick to provide feedback on how to improve upon it.
The BAR’s recommendations, listed below, are divided into three categories: general, C-130 specific, and King 56 salvage.
A. General Recommendations:
1. Lead Command Operating Instruction: The Air Force should review and update the existing lead command operating instruction to:
a. Fully reflect changes which have occurred since the CONUS theater airlift fleet transferred from Air Combat Command to Air Mobility Command.
b. More fully define the lead command’s leadership role and its responsibilities, particularly with respect to configuration control (making certain that cockpit instrumentation and aircraft modifications are standardized across a fleet of like aircraft to facilitate standard operating and maintenance procedures). This leadership role should extend to cover generic operational issues as well.
c. Better define the lead command’s authority to enforce configuration control and the accountability of other commands to the lead’s direction.
d. Empower the lead command and properly resource the lead and other user/supporting commands to enable them to:
1. Update, consolidate and standardize aircraft flight manuals and operating guidance to assure crews have current procedures and performance data.
2. Do the same for maintenance manuals to assure maintainers have the up-to-date information they need to properly maintain the aircraft.
2. Air Force, Federal Aviation Administration, and National Transportation Safety Board Standardized Flight Data Recorder Parameters: DFDR performance limitations severely hampered the King 56 investigations and this review. The Air Force should consider the Federal Aviation Administration and the National Transportation Safety Board guidelines and experience in arriving at a standardized set of digital flight data recorder flight parameters. This would ensure that essential flight data is captured for evaluation in future incidents and accidents.
3. Ditching & Bailout Procedures: The Air Force should review ditching and bailout procedures. As part of this effort, the Air Force should:
a. Conduct an analysis of world-wide ditching events. That data should be used to update and standardize all flight manuals with an accurate discussion of ditching survivability and techniques.
b. Review the information concerning bailout in the flight manuals for consistency between models of the same aircraft, and revalidate the accuracy of the information provided to the crews.
c. Establish a requirement for crews to review these procedures on the first leg of each over-water mission, in order to maintain reasonable familiarity with these procedures.
d. Establish a standard life support equipment requirement, appropriate for the aircraft’s missions, for each mission design series C-130 and equip each for that requirement.
B. C-130 Specific Recommendations
The team made the following recommendations based upon its BAR of C-130 missions, operating environments, and the fleet’s flight safety record (with particular emphasis placed on the 71 incidents the BAR examined involving uncommanded power reduction):
1. C-130 Technical Orders: A total of 487 of the Air Force’s 627 C-130 technical orders currently have an inordinate number of supplemental page inserts and are in need of a complete rewrite to incorporate the new information into the body of the text. For several years there has not been sufficient funds available to complete the rewrites. This important issue is broader than just the C-130 alone and is under review Air Force-wide. It will require a significant investment, over $20 million and approximately two years to fix the C-130 alone, using current manpower levels to correct. The Air Force should fully fund this action, as well as new initiatives underway to convert USAF technical manuals from the old, expensive and time-consuming paper format to the newer digital format. New CD-ROM technology offers many benefits, including a reduction in the annual $2.5 million cost of maintaining our T.O.s. This conversion faces many obstacles, including the cost of conversion as well as training and equipping field units to handle electronic data rather than paper.
2. EC-130 Commando Solo II Mission Evaluation: Until replaced with newer, more capable C-130s, the Air Force should reevaluate and closely monitor the EC-130 Commando Solo II mission.
C. King 56 Salvage
The BAR recommends the Air Force recover selected wreckage from King 56. The components of greatest interest are: the wing section, the fuselage tanks, and the cockpit fuel quantity gauges. These items could answer many open questions and provide additional information concerning the various fuel-related scenarios. While the exact cause of the King 56 mishap may never be known with absolute certainty, this wreckage could reveal a probable cause and refute many scenarios. The most compelling reason to obtain additional wreckage is the possibility that evidence might be found which points to an unknown new scenario.
Section 1.0
C-130 Operating Environments and Missions
1.1.1 Since its introduction into the Air Force inventory in 1955, the C-130 has served in a variety of operating environments and missions. From the polar regions to the tropics, this aircraft has delivered personnel, equipment, and supplies by a variety of means to locations all over the planet. Over 2,000 aircraft support the United States and its Allies’ military operations, as well as numerous commercial operations.
1.1.2 There are few environments this aircraft has not operated in. It has served as a launch platform for remotely piloted vehicles, and as a recovery platform for both personnel and data packages. It routinely penetrates hurricanes, delivers ordnance, provides combat communications links, facilitates rescues on land or at sea, services our remote stations at the North and South Pole, refuels aircraft, and broadcasts radio and television messages when the mission requires. In the late 1950s, it provided a good deal of aerial photography for cartography used to this day in the United States. It has been an air ambulance, and a deliverer of relief supplies to refugees, and a transporter of refugees to safety around the world. It has fought forest fires from California to Indonesia. By far, it’s most often seen as a theater airlifter, either air dropping or air landing troops, equipment, and supplies to wherever they are needed.
1.1.3 The aircraft used in this theater airlift role typically operate in the low altitude regime, flying a few hundred feet above the ground with their crews navigating by a combination of pilotage, self-contained navigation systems, global positioning systems, and "dead reckoning." Flying a series of carefully developed course lines, designed to avoid known threats while ingressing to their target drop or landing zones, these aircraft typically stay low until their destination, rising only to drop their paratroops or pallets, or coming in for an "assault" (short field, i.e., 3,000 foot long airstrip) landing. They exit the same way. Equipped in some cases with Adverse Weather Aerial Delivery Systems (AWADS) or their equivalent, they may drop their loads without ever seeing their target visually, but with impressive and reliable accuracy. Traveling singly or in formation, in daylight or on night vision goggles in blacked-out configuration, they deliver the goods where needed.
1.1.4 While the low-level portion of the flight exposes them to hazards from bird strikes to small arms, anti-aircraft artillery fire, and Surface to Air Missiles (SAMs), it is the pass over the drop zone, or the time spent getting into and out of the assault strip, that is probably the most dangerous for the aircraft and crew. Relatively high in the air and slow at that point, here they are most vulnerable to ground fire. A large portion of the C-130 force trains for this kind of operation daily.
1.1.5 Not always used in the combat delivery mode, the basic airlift version of the C-130 has an intercontinental range, allowing it to carry a number of pallets of cargo, or up to 92 passengers. This range, and the aircraft’s versatility, made it a logical candidate for a number of modifications to support a variety of special missions.
1.2 C-130 Operating Environments and Missions
1.2.1 The C-130 is arguably the most versatile aircraft in the Air Force inventory. Currently 52 units in the active force, Air National Guard and the Air Force Reserve Command fly the aircraft in the combat aerial delivery mode alone.
1.2.2 Combat Aerial Delivery: The most common mission is called combat aerial delivery, or "CAD" for short. This term refers to delivering cargo by landing at an airfield (called "airland") or dropping it by parachute (called "aerial delivery"). The airland mission involves operating the aircraft into airfields worldwide, from large, busy commercial airports like Chicago, O’Hare, to small, isolated, unimproved dirt landing zones bulldozed and hacked out of almost anyplace, which can be as short as 3,000 feet long. The aerial delivery element of CAD involves air dropping personnel and equipment following ingress. This can be done as a single aircraft or as part of a large formation. Airplanes get to the drop zone by making use of either visual procedures or in Instrument Meteorological Conditions (in weather, or "IMC" and flying on instruments) using Station Keeping Equipment (SKE). SKE depicts the other airplanes within a formation, and tells the pilot continuously where to fly to maintain the exact desired position, both vertically and horizontally, within the formation. The Air Force flies this mission at night as well, at a minimum altitude of 500 feet above ground level (AGL), using visual procedures and night vision goggles ("NVGs" light up the portion of the ground or sky the pilot is looking at by use of light amplification).
1.2.3 Rescue: In addition to flying typical combat aerial delivery missions, rescue units fly three other missions. The first is aerial refueling helicopters. These refuelings are conducted at altitudes as low as 1,000 feet and are done both day and night, with night missions using NVGs. The second mission involves the deployment of life rafts and other materials to survivors at sea, by conducting air drop operations from altitudes of 150 feet above the water during the day and 500 feet above the water at night. A third mission is search. Rescue crews routinely practice overwater and overland searches from altitudes as low as 500 feet. Over the years, rescue units have developed a capability to insert rescue forces long range into hostile territory. Their range and refueling capabilities enable them to ferry rescue helicopters great distances for recovery of these inserted rescue forces
1.2.4 Special Operations: Crews flying Special Operations aircraft fall into several categories. Some fly aircraft in a rescue role similar to the rescue mission discussed above. Another Special Operations mission is to fly combat aerial delivery-like operations but in a more demanding environment. These aircraft are equipped with more precise navigation equipment, allowing lower altitudes during night operations. They are also capable of landings on unlit landing zones and aerial refueling in flight (as the receiver aircraft, thus extending their range).
1.2.4.1 When operating at night, gunships use sensitive optical and electronic sensors to detect ground activities and direct a wide array of weapons to attack those targets.
1.2.4.2 "Commando Solo II" is the name for the psychological warfare mission flown by one Air National Guard unit. This mission involves orbiting near, or in some cases over, enemy territory to broadcast information or jam enemy operations. They operate at extremely high operational weights and can be refueled while airborne. These aircraft have the highest empty gross weights of the fleet, owing to the broadcast equipment they carry. When combined with their relative age, the requirement to refuel to near emergency gross weight limits for deployments on operational missions, and the high potential for Radio Frequency Interference (RFI) induced electrical problems, these factors identify this mission as one associated with marked higher risk than others.
1.2.4.3. "Senior Scout" is another variant that serves as an intelligence-collection platform. The mission is accomplished by both active and ANG units.
1.2.5 Polar Operations: One ANG unit flies C-130s equipped with skis for landing on snow and ice. This unit is principally responsible for support of Arctic and Antarctic operations. These operations expose both aircraft and crews to the environmental challenges of extreme cold, variable weather and substandard landing zones.
1.2.6 Compass Call/Airborne Command, Control and Communications (ABCCC): These two missions have different operational roles but operate in basically the same environment. The aircraft serve as a platform for communications activities. Operating in a "stand off mode" that generally places them adjacent to the battle area but not directly in or over it, their operational environment is relatively benign. The mission’s chief drawbacks are its requirement to operate in proximity to unfriendly nations, its high aircraft operational weights, and the need to remain on station for extended periods of time.
1.2.7 Weather: The weather aircraft and crews, assigned to Air Force Reserve Command (AFRC), are used for storm tracking and evaluation. By flying into hurricanes and taking atmospheric readings at various locations within the storm, they obtain data critical to improved weather forecasting. The principal dangers associated with this mission are weather related turbulence and lightning.
1.2.8 Other missions: Several units maintain a limited capability to conduct unique operations.
1.2.8.1 Aerial Spray: These AFRC crews conduct low-level operations in rural and, occasionally, urban areas to dispense pesticides, oil dispersing agents and defoliants. These operations are conducted at altitudes as low as 100 feet and speeds of 125 knots. This operation is only conducted in daylight and in good weather.
1.2.8.2 Modular Aerial Firefighting System: This mission, flown by both Air National Guard and Air Force Reserve Command crews, involves dropping fire retardant foam on forest fires. This operation is conducted at altitudes of 150 feet, 130 knots. The greatest demand on the crews and aircraft is operation in heavy smoke that reduces visibility in rugged terrain.
1.2.8.3 Space Shuttle Support: One rescue unit has the principal responsibility to support rescue efforts for every NASA Space Shuttle launch. The HC-130 serves as a command-and-control platform, a jump platform, and an air refueling platform for rescue helicopters.
Section 2.0
Aircraft Systems
2.1.1 The team reviewed all major C-130 aircraft systems with specific emphasis on safety-related issues or deficiencies that exist. This section includes a description of each system, safety issues that surfaced during the review, and the corrective actions taken or that needed to be taken to mitigate the issues or deficiencies noted.
2.1.2 Special emphasis was placed on possible causes of uncommanded power reductions. The team accelerated the Failure Modes, Effects and Criticality Analysis (FMECA) of the synchrophaser and required specific ground and flight tests to be conducted.
2.1.3 Prior to the establishment of the BAR, C-130 systems were in the process of being analyzed through the FMECA process to uncover hypothetical failure modes. It analyzes design and performance data to determine how the targeted systems perform their intended functions, as well as whether those systems have unrecognized effects or synergistic interactions with related systems. It then extrapolates the relative severity, probability, and worse-case impact of each identified failure mode. More simply put, each piece or part of the aircraft’s systems are being evaluated to determine what its function is, how many different failure modes each piece or part can have, and how each failure mode effects both the systems and the aircraft as a whole.
2.1.4 The aircraft fuel system was subjected to ground and flight tests at Edwards AFB. The test objectives used were designed to see if the system could theoretically function in ways not previously recognized. These objectives took into account both systems and aircraft design, as well as human factors. The team felt the dual approach of systems analysis and aircraft ground and flight tests was the best way to evaluate which system (or combination of systems) malfunctioning can result in a power-loss.
2.2.1 The airframe subsystem is the "skeleton" of the aircraft and supports various flight and landing "loads" (i.e., the term used for stresses put on the airplane on the ground or in flight). The airframe subsystem is comprised of four major structural elements: the wing, fuselage (i.e., the body of the aircraft which actually carries the passengers and cargo), empennage (the "tail section" of the aircraft), and the landing gear. The primary purpose of the wing is to generate the lifting force needed to hold up the fuselage in flight. The fuselage structure must also support cargo and pressurization load stresses, as well as the load stresses being transmitted from the wings and from the empennage. The empennage structure transmits and carries the same type of load stresses as the wings, except that they are smaller and serve to keep the airplane stable around the vertical and lateral axes in flight. Last, the landing gear absorb the shock and vibration load stresses that occur as a result of taxiing, takeoff, and landing. During the BAR’s review of C-130 flight safety, they noted no flight safety concerns related to the aircraft’s structure that were not being addressed by the C-130 SPO.
2.3 Propulsion (Propellers & Engines)
2.3.1 The C-130 is powered by either four T56-A-7B or T56-A-15 engines. The major components of the engine are the power section, extension shaft assembly, and the reduction gear assembly.
2.3.2 Power Section. The power section of the engine has a single entry, 14-stage axial-flow compressor, a set of 6 combustion chambers, and a 4-stage turbine. Mounted on the power section are an accessories drive assembly and components of the engine fuel, ignition, and control systems (the engine fuel system is described in detail later in this section). The ignition system is a high-voltage, condenser discharge type, consisting of an exciter, two igniters, and control components. The ignition system is powered by the essential DC bus. The system is controlled by the speed-sensitive control through the ignition relay, which turns it on anytime the engine RPM is between 16 and 65 percent. A manifold bleeds air from the compressor for airplane pneumatic systems. Anti-icing systems prevent accumulation of ice in the engine inlet air duct and the oil cooler scoop. Fuel flows into the combustion chambers and is burned, increasing the temperature and energy of the gases. The gases pass through the turbine, causing it to rotate and drive the compressor, propeller, and accessories.
2.3.3 Extension Shaft Assembly. The extension shaft assembly consists of two concentric shafts and the torquemeter components. The inner shaft transmits power from the power section to the reduction gear assembly. The outer shaft serves as a reference shaft for the torque indicating system.
2.3.4 Reduction Gear Assembly. The reduction gear assembly reduces the high speed of the engine (13,820 RPM) to the lower speed needed by the propeller (1,020 RPM). The reduction gear contains a reduction gear train, a propeller brake, an engine negative torque control system, and a safety coupling. The reduction gear train is in two stages, providing an overall reduction of 13.54 to 1 between engine speed and propeller speed.
2.3.5 Related Deficiencies and Concerns:
DEFICIENCY: In the event of total AC electrical failure or flameout of all four engines in-flight, the engine ignition system cannot be powered from the aircraft battery.
ON-GOING RESOLUTION: The BAR supports development and implementation of a C-130 modification which would allow the ignition system (essential DC bus) to be powered from the aircraft battery in-flight in the event of total AC electrical failure or flameout of all four engines.
2.3.6 Each engine is equipped with a Hamilton Standard four-blade, electro-hydromatic, full feathering, reversible-pitch propeller. The propeller operates as a controllable-pitch propeller for throttle settings below FLIGHT IDLE and as a constant-speed propeller for throttle settings of FLIGHT IDLE or above. The major components of the propeller system are the propeller assembly, the control system, the synchrophasing system, and the anti-icing and de-icing systems.
2.3.6.1 Propeller Assembly. The propeller assembly consists of the actual propeller blades, the barrel assembly (which retains the blades and also contains the pitch lock assembly), and the dome assembly (which contains the pitch changing mechanism and the low pitch stop assembly).
2.3.6.2 Control Assembly. The control assembly is mounted just behind the propeller assembly but does not rotate. It contains the oil reservoir, pumps, valves, and control components which supply the pitch changing mechanism with hydraulic pressure to change the propeller blade angle. All mechanical and electrical connections necessary for propeller operation are made through the control assembly. The mechanical connections are for the engine control system and the negative torque signal (NTS) system. The electrical connections are for oil level indications, pulse generator coil, auxiliary pump motor, synchrophasing system, NTS and feather switches, anti-icing and deicing systems and the electrical feathering system. The valve housing is the "brain" of the propeller and contains the fly weight speed sensing pilot valve, feather valve, feather solenoid valve, and feather actuating valve. The speed of the propeller is controlled by the fly weight speed sensing pilot valve. The valve is controlled by the mechanical action of the flyweights opposing the force of the speeder spring. Under normal conditions the propellers are rotating at 100% of its design speed (1,020 RPM) or "on-speed". When the propeller is in an on-speed condition, the metered hydraulic pressure equals that required to maintain the required blade angle. When an overspeed condition occurs, the fly weight force overcomes the speeder spring force, and the pilot valve moves to port hydraulic pressure to increase the blade angle which causes the propeller to slow down. If the propeller slows down below the governed speed, the force of the speeder spring overcomes the force exerted by the fly weights, and the pilot valve moves to port hydraulic pressure to decrease the blade angle, which allows the propeller to increase speed. The action of the fly weight speed sensing pilot valve is the primary means of controlling the RPM of the propeller and is always attempting to maintain 100% (1,020 RPM) in flight.
2.3.6.3 Synchrophasing System. The propeller mechanical governor will hold a constant speed in the flight range, but throttle changes will cause the governor to overspeed or underspeed slightly while trying to compensate for the change in power. The synchrophasing system assists the mechanical action of the fly weight speed sensing pilot valve. The synchrophaser provides speed stabilization, throttle anticipation, and synchrophasing. The speed stabilization circuit stabilizes the mechanical governor when the propeller governor control switch is in the NORMAL position by sending a signal to the speed bias servo motor to change the speeder spring compression. Throttle anticipation stabilizes the propeller speed during rapid movement to the throttle when the propeller governor control switch is in the NORMAL position. Rapid throttle movement sends an amplified signal to the speed bias servo motor to change speeder spring compression. The synchrophasing system acts to keep all the propellers turning at the same speed, and it maintains a constant rotation position relationship between the blades to decrease vibration and to lower the noise level. The system uses either the number 2 or the number 3 engine as the master engine, and relates the blade position of the other three propellers to the master. The blade position of a slave propeller is changed by moving the pilot valve to increase or decrease the speed of the engine. The synchrophasing circuit determines blade position by comparing an electrical pulse generated by each slave propeller to a pulse from the master propeller. In normal governing and synchrophaser modes, the synchrophaser can only change the RPM of the propeller approximately 2.5%. Mechanical stops in the propeller valve housing prevent the RPM from decreasing more than 4% (below 96%) or increasing more than 6% (above 106%).
2.3.6.4 Anti-Icing and Deicing System. The propeller anti-icing and deicing system is made up of resistance-type heating elements which are incorporated on the leading edge and fairing of each blade and the entire spinner assembly for anti-icing. Continuous anti-icing heaters cover the front portion of the spinner assembly and the entire afterbody assembly. Cyclic deicing heaters cover the remainder of the spinner front section, the spinner rear rotating section, the spinner plateaus, and the blade leading edge and fairing. Power from the aircraft electrical system is transmitted through a brush housing assembly through rotating sliprings to the anti-icing and deicing elements.
2.3.7 Rollback. The term "rollback" has been used for several years to describe an event in which multiple engines experience a sudden, relatively small reduction in engine speed, uncommanded by the crew and with no prior indications of engine problems such as fluctuating fuel flow or turbine inlet temperature (TIT). Rollbacks have historically been associated with the synchrophaser or electrical system problems, such as low voltage or electromagnetic interference (EMI), which can affect synchrophaser operation.
2.3.7.1 During a rollback, affected engines respond essentially simultaneously. Some rollbacks are momentary, (i.e. the RPMs pull back for a few seconds) and then recover without crew intervention. Some rollbacks persist and do not recover until the corrective procedures are performed. However, in both instances, the engines exhibit relatively stable operation except for momentary torque and RPM changes. In other words, the torque and RPM changes are not accompanied by significant variations in fuel flow and TIT.
2.3.7.2 Since the synchrophaser has no direct control over the power output of the engine and has such limited RPM control authority, it cannot by itself cause large, unstable, erratic variations in fuel flow, TIT, torque, etc. These are indications that something else is affecting the power output of the engine, such as a fuel system problem. However, if the engine selected as "master" (either number 2 or number 3 engine) is experiencing problems for any reason which reduces its power enough to affect its RPM, the other three "slave" engines will be driven by the synchrophaser into small variations, as it tries to keep them in phase with the malfunctioning engine. If this should happen, the RPMs of the three remaining engines will only be driven down by a maximum of 2.5%.
2.3.7.3 Ground tests during earlier synchrophaser investigations confirmed that erroneous output signals to the propeller governors had little to no effect on actual engine power output. One possibility tested was that those electrical disturbances known to produce erroneous synchrophaser signals could also independently affect the temperature datum (TD) amplifier, causing uncommanded power reduction unrelated to synchrophaser RPM reduction. The laboratory instruments revealed these electrical disturbances did not effect actual engine power output, but did produce erroneous aircraft instrument readings.
2.3.7.4 Crew reactions to rollbacks and power fluctuations have varied considerably. Some report that the event is no more than a mild annoyance; others say it really gets their attention. However, the measurable effect of a rollback on the flying qualities of the aircraft has proven to be very small. Rollbacks have been extensively investigated, both by gathering data on actual incidents and by duplicating the events during engine test cell runs and flight tests. As a result, rollback causes have been identified and corrective actions implemented which have dramatically reduced both the frequency and the magnitude of the events.
2.3.7.5 Engine rollbacks can be caused by internal synchrophaser failure, resulting in erroneous output signals. Since the synchrophaser was redesigned (from vacuum tube to solid state technology), this is now a rare event. The new synchrophasers contain safeguards designed to limit the magnitude of erroneous signals if the unit did fail. Although reliability increased with the solid state units, they did exhibit vulnerability to electrical power disturbances and EMI, or "noise," from other aircraft electronic systems, notably the high frequency (HF) radio. Several equipment modifications have been made which have been effective in reducing the frequency and impact of these events. Some wires have been shielded, components redesigned and additional components installed to stabilize the synchrophaser system. As shown in the failure history, (see Figure 5-3), these changes have been effective in reducing rollback occurrence. A continuing problem is the susceptibility of the aging synchrophaser wiring bundles to EMI.
2.4.1 Aircraft Fuel System. The primary purpose of the fuel system is to efficiently distribute fuel to its engines. There are four main fuel tanks and two auxiliary tanks located in the wings. The main tanks are numbered 1 through 4, from left to right. The auxiliary tanks are located in the center wing. Two external tanks are installed on pylons under the wings (C-130E/H aircraft and their variants). Tanker/rescue and other special mission aircraft are also equipped with one or two internal fuselage tanks. The fuel tanks are vented and fuel is displaced by ambient air as the tanks empty (fuel is displaced by cabin air for the fuselage tanks). Fuel management is controlled by the flight engineer through the overhead fuel control panel located on the flight deck (see Figure 2-1). C-130 tanker aircraft have an additional air refueling panel which contains the controls and gauges for the fuselage tanks that is also controlled by the flight engineer (see Figure 2-2). By positioning the switches on the panel(s), the flight engineer can control how fuel is used during flight as well as manage refueling and dumping operations.
Figure 2-1: Typical Overhead Fuel Panel, located on the cockpit ceiling between the pilots
2.4.1.1 All fuel tanks are interconnected by two pipes or "manifolds". One is called the crossfeed manifold, the other is the refuel/dump manifold. These two manifolds can also be interconnected. By selectively opening or closing various valves and activating or deactivating pumps, fuel can be pumped from any tank to any engine the flight engineer requires.
2.4.1.2 When each engine is fed by its corresponding fuel tank (number 1 tank supplies fuel to the number 1 engine, etc.), it is described as "tank-to-engine" configuration. This is the normal fuel system configuration used for take-off and landing (see Figure 2-3). The "tank-to-engine" configuration requires the partitioning of the crossfeed manifold through the use of shut-off valves and the use of each tank’s boost pump to provide positive fuel pressure.
Figure 2-2: Typical HC-130N/P Auxiliary Fuel Panel
Figure 2-3: Typical HC-130N/P Fuel System in Tank-to-Engine Configuration
2.4.1.3 When the crossfeed manifold shutoff valves are opened and fuel is drawn from the external, fuselage, auxiliary, or other main fuel tanks, it is described as crossfeed operation (see Figure 2-4). This is usually used during cruise flight to utilize the fuel contained in the auxiliary, external, and fuselage tanks.
Figure 2-4: Typical HC-130N/P Fuel System in Crossfeed Configuration
2.4.1.4 The boost pumps for the external, fuselage, and auxiliary tanks have a higher output pressure (28-40 psi.) than the main tank boost pumps (15-24 psi.). This design feature allows the main tank pumps to remain on, so that in the event that fuel is not delivered from any of these tanks, the main tank boost pumps deliver the required fuel immediately. In each case, the higher pressure over-rides the weaker main tank boost pumps. When the selected tank is empty, the main tank pumps assume the task of supplying fuel to the crossfeed manifold. In an emergency, fuel can be dumped overboard by using dump pumps located in each tank and directed through the dump manifold to the dump masts located in each wing tip.
2.4.1.5 A safety improvement implemented by the Air Force has been the transitioning from JP-4 fuel to the less volatile JP-8. Some slight problems have surfaced during this fuel transition, such as small fuel leaks which have been attributed to o-ring shrinkage. The solution has been to replace o-rings with new ones on an "as required" basis. Additionally, improvements in tank sealing technology have drastically reduced the number of external fuel leaks attributed to improper fastener installations or joint sealing interfaces.
2.4.1.6 Over the years, the basic fuel system has been modified and/or enhanced, depending on the mission design series (MDS). Some C-130s have fuselage tanks to extend their range and/or allow other aircraft to be refueled in flight. Additionally, some aircraft have been modified to receive fuel in flight from an aerial tanker.
Fuselage Tanks. The fuselage tanks were added to the aircraft to enhance the fuel capacity/range. Consisting of one or two 1800 gallon cylindrical tank/s they are mounted in the cabin section of the fuselage, near the aircraft’s center of gravity. The fuselage fuel tank has either a single or dual pump configuration. The pumps are rated for 28-40 psi. The single and dual pump tank configuration is not consistent from aircraft to aircraft, since these tanks are removed and replaced for mission purposes and maintenance requirements routinely. Depending upon mission requirements, some planes will fly with zero, one, or two fuselage tanks. The fuselage tanks are plumbed into the aircraft’s refuel/dump manifold. The right external dump valve is controlled with the right external crossfeed valve switch, connecting the dump manifold to the crossfeed manifold. This allows fuel from the fuselage tanks to be routed to the crossfeed manifold for engine consumption. The fuselage fuel tanks vent system is unique to the other aircraft fuel tank vent systems. Because the fuselage tank resides in the aircraft’s pressurized cabin section, the fuselage tanks internal space is maintained at cabin pressure to prevent structural damage to the tanks. This is accomplished by a vent system that allows cabin air to enter the tank when the aircraft is pressurized or fuel is pumped from the tank. The vent system also allows pressure in the tank to be vented outside the aircraft when the aircraft is depressurized or fuel is pumped into the fuselage tank.
2.4.1.7 The C-130 basic fuel system has required no major modifications to resolve safety concerns. However, slight modifications such as the addition of the 1360 gallon external pylon tanks (installed on C-130E/H aircraft and their variants), valve relocations and operations, and plumbing routing, have been incorporated to extend the capabilities of the C-130. The C-130 fuel system experiences normal wear and tear which eventually requires individual components to be repaired/overhauled and/or replaced. For example, boost and dump pumps fail; o-rings and couplings leak; gate, and butterfly valves fail; and fuel system plumbing may become damaged. Occasionally, isolated fuel system related problems have required depot engineering assistance.
2.4.1.8 Failure of the fuel system to provide fuel to the engines centers around two conditions:
Insufficient fuel getting to the engine burner cans - Insufficient fuel could be the result of a fuel leak, inadvertent fuel dumping, fuel system or engine component failure, or allowing the tank to be emptied without other tank boost pumps on or without switching to a fueled tank. Failure to prime the fuel manifolds can result in existing air in the fuel manifolds being sent to the engines. The consequence of these conditions may be an engine flameout.
Contamination - Contamination interferes with the engine fuel system’s ability to deliver a sufficient quantity of fuel to the engine combustion chambers which can reduce the power output of the engine. The circumstances leading to this are contaminated fuel introduced at the last refueling, fuel becoming contaminated due to in-tank debris from maintenance or internal deterioration of the tank or fire suppression foam, or water due to condensation or rain entering through filler caps. In extreme cases, such contamination may clog filters and their associated bypass valves, resulting in engine flameout.
2.4.2 Engine Fuel System
Figure 2-5: C-130 Engine Fuel System
2.4.2.1 The main components of the engine fuel system consists of the fuel pump, fuel control, temperature datum (TD) valve, and fuel nozzles, along with drain valves and two fuel filters. Fuel flow through these components is shown in Figure 2-5.
2.4.2.2 Fuel supplied from the aircraft fuel tanks is delivered to an engine-driven, two-stage, gear type fuel pump. In the event of the failure of one stage of the pump, the two-stage design ensures the engine will be supplied with sufficient fuel.
2.4.2.3 The fuel control is a hydro-mechanical metering device designed to supply a controlled fuel flow to the engine during all operating conditions. Located on the engine, the fuel control measures the RPM of the engine, the inlet air temperature, inlet air pressure, and throttle position. Fuel metered by the control is equal to engine requirements, plus an additional 20%, which is for the use of the TD valve, a part of the TD system. There are six fuel nozzles mounted in the "diffuser case" of each engine. One fuel nozzle extends into the forward end of each of the six combustion liners. Looking like large metal cans with holes punched regularly around their sides to carefully contain the flames, two of these opposing liners have igniter plugs to ignite the fuel during engine start. As the fuel nozzles disperse the fuel in a fine spray to maximize combustion efficiency within the engine, interconnecting tubes between the liners spread the flame and assure complete combustion within.
2.4.2.4 The TD valve is an electrically operated fuel-trimming device. All fuel flowing from the fuel control must pass through it before being sent to the fuel nozzles. Since the TD valve receives 120% of engine fuel flow requirement from the fuel control, some fuel must be bypassed by the valve. Fuel in excess of that required by the engine is bypassed and returned to the inlet of the fuel pump. When only that 20% surplus is bypassed, this is known as a "NULL" condition. When less than 20% is being bypassed to the fuel pump, this is known as a "PUT" condition. When more than 20% is being bypassed, this is known as a "TAKE" condition.
2.4.2.5 A small drive motor operates a piston inside the TD valve which adjusts how much fuel is ultimately passed on to the fuel nozzles. This drive motor is controlled by a signal from the TD amplifier (TD amp).
2.4.2.6 The TD system works to help keep the engine running at the temperature and power setting the pilot selects when he moves the throttles. It also allows the engines to burn several different kinds of fuel. The TD amp receives a temperature signal from 18 engine "thermocouples." These are metal probes which accurately measure high temperatures within the engine. They are mounted at the inlet of the turbine section of each engine, just behind where the fuel is burned and the resultant gases are near their hottest point. The TD amp compares an average of these 18 signals from the inlet of the turbine with the "reference signal" in the TD amp (for start temperature limiting protection), or from the temperature setting commanded by the pilot’s throttle movements. The throttle’s signal is generated through a "potentiometer" (i.e., a rheostat) in the "throttle coordinator," which is also on the side of the engine. The signal from the potentiometer corresponds to the position of the engine throttle lever. When the temperature signal from the thermocouples matches the reference signal, the TD amp sends no signal to the TD valve, and the valve remains in the "NULL" Position. If the temperature signal is greater than the reference signal, the TD amp sends a signal to the TD valve to "TAKE" fuel. If the temperature signal is less than the reference signal, the TD amp sends a "PUT" signal to the TD valve. In this fashion, through thousands of small corrections, the TD system constantly works to keep the engine operating at the desired temperature.
2.4.2.7 Related Deficiencies and Concerns
DEFICIENCY: Some fuselage tanks have only one fuel pump.
ON-GOING RESOLUTION: Continue installing pumps until all fuselage tanks have two pumps.
DEFICIENCY: In the event of a main tank failure, T.O. 1C-130(H)H-1, page 3-23 allows the use of the dump pump from the same main tank to crossfeed to its respective engine. This is an adequate procedure but its use should be discontinued before the dump pump inlet is uncovered. According to T.O. 1C-130(H)-1, page 1-47, this occurs at approximately 1,500 to 2,100 lbs, depending upon the specific type of C-130.
RECOMMENDATION: The BAR recommends that Air Force establish a fuel quantity limit for using the above procedure and revision of all affected C-130 T.O.s accordingly.
2.5.1 Four engine-driven alternating current (AC) generators and an auxiliary generator power the AC electrical system of the C-130. On aircraft prior to tail number 74-1658, an auxiliary AC generator is driven by an air turbine motor (ATM) which is operated by high-pressure air from either the gas turbine compressor (GTC), or from an operating engine. The GTC cannot be operated in-flight, but the ATM can be operated to supply AC power if the bleed air manifold is pressurized. Newer aircraft received an auxiliary power unit (APU) which can be operated in flight. The APU generator is directly splined to the APU and does not rely on bleed air to operate.
Figure 2-6: C-130 AC Bus Power Sources
2.5.2 The AC generators are connected through transfer contactors (relays) to four AC buses: the left hand AC bus, the essential AC bus, the main AC bus, and the right hand AC bus. The transfer system is automatic and operates in such a manner that any combination of two or more engine-driven AC generators will power all four AC buses. With only one AC generator supplying power, only the essential and main AC buses will be powered. In the event of complete loss of all AC generators, none of the AC buses will be powered. Operation of the APU or ATM generator will supply power only to the essential AC bus. Combinations of operating generators and the buses they power are shown on the AC bus power sources chart in Figure 2-6 above.
2.5.3 The normal source of direct current (DC) power is four transformer-rectifier (TR) units. These units change the three-phase AC power from the AC generators to 28 volt DC power. A 24-volt battery is provided as an emergency source of DC power. Two of the TR units are connected to the essential AC bus with their output supplying power to the essential DC bus. The other two TR units are connected to the main AC bus with their output supplying the main DC bus. In the event of total AC power failure, the essential DC and main DC buses will also lose power. In this case the only remaining power source is the aircraft battery which will power the battery bus and the isolated DC bus to provide basic instruments and communication for the flight crew.
2.5.4 Related Deficiencies and Concerns
DEFICIENCY: Configuration Control - Over the previous 10 years, detailed control over and knowledge of the exact configuration of each aircraft has been lost. This is the result of having many different C-130 users, several diverse missions, and no cohesive program to force compliance upon the various operators. As a result, these aircraft were modified in a less than stringently controlled environment, and by modification teams which did not always precisely follow the modification drawings. Changed under provisions which allowed the C-130 manufacturer to deliver new aircraft with prior modifications installed, their users sometimes preferred cockpit equipment arrangements different from the standard C-130 configuration, but did not fully document these changes. In addition, there are users who modified the aircraft to meet mission needs without documenting the changes, as well as test agencies who did not document their modifications.
ON-GOING RESOLUTION: The BAR supports the C-130 Systems Program Office efforts to institute a configuration management program for USAF C-130 users. Through various directives, the users are required to document all changes and process those changes through a configuration-control process that includes air-worthiness and major command concurrence. Additionally, a digital photographic record and digital location matrix for each aircraft are being gathered. These data are the core of the continued documentation of aircraft configuration as aircraft modernization progresses. Currently, C-130s are undergoing modification to upgrade the electrical system to provide clean avionics power, install defensive avionics, replace unsupportable auto-pilots and install a global positioning system (GPS). These modifications are prerequisites for future upgrade efforts, which will include the recorders, the second INU, the radar, a modernized avionics suite and flight station. Future plans include replacement of the flight data and cockpit voice recorders, replacement of the radar, and installation of a second inertial navigation unit (INU) to replace vertical gyros and compasses.
DEFICIENCY: Many aircraft have wiring that is reaching the end of its service life. Additionally, avionics wiring has been damaged during numerous modifications which install or relocate systems. This wiring degradation increases its susceptibility to EMI. Also, the structure of these aging aircraft has lost some electrical bonding properties which are essential to avionics operation. The C-130 uses the aircraft structure as ground return for the electrical equipment. Installation of the structural components must be accomplished to ensure that each structural piece is electrically the same (zero volts). Electrical systems behave erratically when the ground potential is not zero volts.
RECOMMENDATION: The modifications mentioned above serve to replace most of the electronic wiring and allow the remaining wires to be inspected and repaired or replaced. The immediate need for correcting wiring short-comings, relative to some rollback scenarios, is for the replacement of synchrophaser interface wiring bundles. Also, the aircraft can be improved by rewiring wings and wheel wells. Many maintenance procedures address bonding/grounding integrity; however, both will be assessed and improved during the modernization effort. A continuing problem is the susceptibility of the aging synchrophaser interface wiring bundles to EMI. The BAR recommends the C-130 System Program Office propose a modification to replace the synchrophaser interface wiring bundles on all C-130 aircraft.
DEFICIENCY: Digital Flight Data Recorder (DFDR) - The current DFDR is an unreliable circa-1970s magnetic tape system which has limited channels for recording data. Data recording captures only 25 hours of data. Verification that the system is functional is an arduous two-month process involving shipment of verification tapes to a remote reading site. This system and the accompanying cockpit voice recorder (CVR) are inconsistent with the needs of the safety boards and are incompatible with the projected configuration of the modernized instrument system.
ON-GOING RESOLUTION: The BAR supports the C-130 SPO efforts to modernize the DFDR/CVR in two phases. First, the current DFDR will be replaced with a form, fit, and function solid state recorder which will have additional parameters added. This system will use a solid state recording media which can be read by the using unit to verify proper function. Second, as a part of the modernization of the aircraft, a large parameter capacity system will be installed to accomplish data and voice recording. This system will be compatible with data buses to allow parameters to be recorded directly.
DEFICIENCY: The loss of the DFDR and Cockpit Voice Recorder (CVR) when the power is lost from the last engine generator is considered a deficiency because there is no available record of crew actions or aircraft performance from that point until ground or water impact.
RECOMMENDATION: This report supports C-130 SPO efforts to develop and implement a modification which would provide power to the DFDR and CVR during battery only operation.
DEFICIENCY: The exact desired parameters for DFDR recording need to be defined so as to ensure the DFDR records the essential performance data necessary for post-mishap analysis, considering FAA and NTSB guidelines and/or recommendations.
ON-GOING RESOLUTION: This report supports Air Force Safety Center efforts to provide a list of these parameters.
DEFICIENCY: Review of the aircraft configuration revealed that the ESU modification has configured the generator controls such that, on some E-model aircraft, the crew must shut down the engine when its generator has failed.
RECOMMENDATION: The BAR recommends the C-130 SPO develop and implement a modification which would install generator disconnects or bearing failure lights in all ESU aircraft.
DEFICIENCY: The crew cannot operate the fuel valves, nor can the engine igniters be powered when the aircraft is in an airborne, battery-only condition.
ON-GOING RESOLUTION: The BAR supports development and implementation of a C-130 modification which would bypass the touch-down relay to allow the DC isolated bus to power the DC essential bus, thus allowing fuel valves and igniters to function. This effort would be accomplished concurrently with the existing modification to add an additional reverse current relay. This will provide the ignition source to restart the engines if fuel is available. The BAR does not consider the APU replacement a safety issue since the above provides an alternative way to provide restart capability to an aircraft with windmilling engines. This proposal is currently being evaluated by WR-ALC and is awaiting funding. If funded, it should be complete by Dec 31, 1998. The BAR reviewed the restart capability of the C-130. This is identified as a deficiency elsewhere in this report. Those C-130 aircraft manufactured before 1974 utilized a GTC and ATM to provide limited aircraft electrical power on the ground and in certain in-flight emergencies. The ATM uses bleed air from either the GTC (ground use only) or engines to produce electricity. In the air, the GTC can not be operated so only bleed air from engines can be used to power the ATM. This design feature means that with no engines operating, the ATM can not provide any electrical power. The post-74 aircraft had an APU added to provide electrical power in the same situations as the ATM. It has the additional capability of utilizing external air flow and can provide electrical power with no engines running. The Air Force has considered a retrofit to replace the GTC/ATMs on pre-74 aircraft, with an APU. The decision process involved a risk assessment and cost considerations. The high reliability of the C-130, the absence of any four engine flame-outs in over 24 million flight hours, and the high cost ($1,200,000 per aircraft) argued against the modification. The Air Force is currently proposing a broad ranging upgrade to the C-130 that includes the APU. This modification is driven by international airways conventions, required avionics upgrades, configuration control, and maintainability issues. Including the APU in the modification program substantially reduces the cost of doing the APU upgrade independently.
2.6.1 The pneumatic system provides compressed hot air "bled" from the engine compressors to operate a number of aircraft systems, such as engine ground starting, anti-icing, air conditioning and heating, and pressurization. This air is distributed to various locations within the aircraft via metallic ducts. Over time, these ducts have exhibited a susceptibility to corrosion, resulting in a rupture of the ducting. Because of the heat associated with a bleed air leak, significant damage to the aircraft and other systems can result from a duct failure. As a result of several previously documented duct failures, a program is currently in progress to replace these bleed air ducts with ones made from a more corrosion-resistant nickel alloy. At this time, all of the flight-safety critical ducts have been replaced in all C-130 aircraft, and many other less critical ducts have been or are scheduled to be replaced by the C-130 SPO.
2.6.2 During the review of C-130 flight safety, the BAR noted no flight safety concerns related to the aircraft’s pneumatic system that had not been addressed.
2.6.3 Related Deficiencies and Concerns
DEFICIENCY: None.
2.7 Hydraulics System/Flight Controls
2.7.1 The C-130 has three separate 3,000 psi hydraulic systems: the booster, utility and auxiliary systems. These systems are used to operate flight controls, cargo ramp and door, flaps, brakes, nosewheel steering, and the landing gear. The booster and utility systems are supplied by four engine-driven pumps mounted on each engine’s reduction gearbox. The auxiliary hydraulic system is supplied by an electrically driven pump. For reasons of safety and system reliability, the flight control boost packs for the elevator, rudder, and ailerons are usually pressurized by both the booster and utility systems. Manual operation of the flight controls without any hydraulic assistance is also possible during an emergency.
2.7.2 During the review of C-130 flight safety, the BAR noted no flight safety concerns related to the aircraft’s hydraulic system that had not been addressed by the C-130 SPO.
2.7.3 Related Deficiencies and Concerns
DEFICIENCY: None.
Section 3.0
Operations and Training
3.1 C-130 Technical Manuals ("Technical Orders")
3.1.1 Technical Orders apply to both operators (primarily flight manuals) and maintenance personnel. The BAR will address the flight manual deficiencies in this section. For the aircrew, the flight manual describes the aircraft and how to operate it. It is divided into several sections, including normal operations and emergency procedures. There is a second volume called the performance manual that contains detailed charts to calculate aircraft performance for given conditions (e.g., takeoff , climb, cruise, descent, and landing). The aircrews need an accurate, easily read document for use in flight during normal, abnormal and emergency situations. The following problems were identified with the current manuals.
3.1.2 One flight manual had over 30 active operational supplements altering the basic document and requiring changes to be annotated by hand.
3.1.3 One operational supplement required over 12 hours to post, including write-in changes to critical portions of the emergency section of the manual .
3.1.4 Some charts in the performance manual contain inaccurate data. For example, torque charts in the C-130H model performance manual are known to be in error by up to 7%. In other cases, aircraft configuration changes have outpaced performance manual updates, creating problems in many aircraft variants. One example of this resultant mismatch is the drag index for the Commando Solo II aircraft. Finally, important charts are not available. For example, three- and four-engine climb gradient charts are needed for all models of the C-130.
3.1.5 Several variants of the aircraft have their own separate flight manual. This is necessary because of unique aircraft differences. However, many identical systems in these multiple variants have different procedures mandated in their flight manuals. For example, some commands require engine run-ups while some don’t; some require top of the aircraft inspection and some don’t, some require a positive fuel flow check while some do not. There are individual units where flight manuals for the various aircraft don’t match. In a special operations unit, with a mixture of specialized and basic C-130s, two separate commands manage their two flight manuals. Crews are expected to be competent in both, but even the basic operating procedures are not the same.
3.1.6 All USAF C-130s do not use AF flight manuals. Some special mission aircraft use Lockheed Technical Manuals (LTMs) for flight operations. Crewmembers assigned to these units also operate basic C-130s which use AF flight manuals. As in the above example, because the LTMs and the AF flight manuals do not always contain the same procedures or guidance, aircrew must use different procedures for identical systems depending upon which type aircraft they are flying.
3.1.7 These major operating procedure differences are a by-product of several commands having responsibilities for the flight manual content for the variants under their control. A single lead agency, responsible for conformity, would reduce this problem significantly.
3.1.8 Related Deficiencies and Concerns
DEFICIENCY: Technical Orders currently contain too many supplements that are too large and laborious to incorporate.
RECOMMENDATION: The BAR recommends that the Air Force update, consolidate and standardize technical orders, flight manuals, and published guidance, and to limit the number of write-in changes that can be introduced before a manual must be replaced.
DEFICIENCY: Non-standardized procedures among the many versions of the flight manuals.
ON-GOING RESOLUTION: The C-130 Program Office will host a meeting, tentatively scheduled for 2-13 February 1998, with all C-130 major commands to identify the non-standardized procedures and reach agreement on standard procedures.
DEFICIENCY: Performance manual charts do not match aircraft performance, nor contain needed information.
ON-GOING RESOLUTION: The C-130 Program Office plans to correct the performance manuals and will get this effort underway in the third quarter of fiscal year 1998.
3.2 Aircrew Life Support Equipment
3.2.1 The BAR reviewed the guidance directing the placement of life support equipment carried on C-130 aircraft. They found different commands had different requirements. When the CONUS CAD C-130s moved from ACC to AMC there were significant guidance changes. Currently AFI 11-302 Vol. 1 is in coordination and will provide Air Force-wide guidance standardizing required C-130 life support equipment. The BAR is comfortable that the draft AFI 11-302 addresses the significant issues and will provide adequate guidance and standardization. It is due out in early 1998.
3.3.1 A review of ditching/bailout information and procedures in various flight manuals reveals a significant variation in implied survivability of a ditching maneuver. Flight Manuals managed by AMC and Air Force Special Operations Command (AFSOC) have significantly different guidance. Specifically, T.O. 1C-130H-1 managed by AMC states:
"…ditching of transport-type airplanes can usually be accomplished with a high degree of success." Pg. 3-71 under "ditching."
3.3.2 However T.O.-1C-130(A)U-1, managed by AFSOC, states
"…ditching of the AC-130U can be accomplished with a low probability of aft crew member survivability. The flight deck may be survivable, but ditching should be considered an absolute last resort for any crewmember." Pg. 3-90 under "ditching."
3.3.3 Another apparent contradiction appears in T.O. 1C-130H-1 pg. 3-71 under "ditching characteristics"
"…Reasonably high probability that the airplane can be landed on water without major collapse of structure or a sudden rush of water into occupied compartments."
3.3.4 Compare this citation to the following language found in T.O. 1C-130(A)U-1 pg. 3-90 under "ditching characteristics"
"…reasonably high probability the aircraft structure will collapse followed by a sudden rush of water into occupied compartments."
3.3.5 These two flight manuals addressing the same subject portray vastly different projections of success for a ditching attempt. Of similar concern the diagram on page 3-76 of T.O. 1C-130(H)H-1 titled "Emergency Exits-Water" depicts a fully intact C-130 floating in the water. None of the aircraft in the three most recent C-130 ditchings survived intact. The referenced diagram gives support to the idea of a survivable ditching.
3.4.1 Categories of Training C-130 Aircrew Training falls into four major categories: Initial C-130 Qualification Training, Initial C-130 Mission Qualification Training, Continuation Flying Training, and Continuation Ground Training.
3.4.1.1 Initial C-130 Qualification Training. This is the first formal Air Force training course a prospective C-130 crew member will attend and is normally conducted at Little Rock Air Force Base in Arkansas. It consists of classroom, aircraft simulator, and flight training. The classroom phase covers the basics of aircraft systems and checklist procedures. During the simulator phase, the new pilots and engineers learn to integrate their systems knowledge and checklist use into a coordinated crew effort. They practice both normal and emergency procedures, simulate flying entire missions, and develop an understanding of crew coordination, learning to work together effectively in a crew environment. The two combined phases consist of 210 hours in the classroom, and 36 hours in the simulator. Navigators receive training in the aircraft systems navigation simulator to become familiar with how to guide the aircraft using its self contained navigation system (SCNS), and the other compass and navigational aids on board. During the flight phase, the new crewmembers will practice basic aircraft maneuvers, both on the ground (i.e., engine start, taxiing, and backing), and in the air (e.g., takeoffs and landings, en route navigation, instrument approaches, and visual traffic patterns). Flight hours logged vary by position, with new pilots accumulating the most hours (approximately 60 hours per pilot) during these courses owing to the necessity to develop their flying skills. The successful completion of this training qualifies an individual to fly "basic air-land missions," i.e., those requiring getting from one point to another while carrying passengers and/or cargo, in the C-130. Little Rock Air Force Base historically produces approximately 2,400 graduates (cumulative, all crew positions) per year.
3.4.1.2. Initial C-130 Mission Qualification Training. This training initially qualifies crewmembers in a specific operational mission of the C-130 (such as airdrop, short field landings, rescue, special operations, firefighting, electronic combat, psychological operations (PSYOP), and others. Like initial qualification, this phase also consists of classroom, simulator, and flight training. For those trained in the combat delivery mission, which comprises the largest portion of the C-130 crew force, initial airdrop and short field landing formal training (also known as "assault landing" training) is normally conducted at Little Rock Air Force Base, but class availability sometimes necessitates in-unit training at home station. Most C-130 special mission qualification training is conducted in-unit or at Kirtland Air Force Base (for special operations units and rescue).
3.4.1.3 Continuation Flying Training. Once crewmembers complete initial qualification and mission qualification, they must maintain that qualification by successfully completing certain training events on a recurring monthly, quarterly, or semi-annual basis. Referred to as "maintaining currency," accomplishing these training events assures that the individual refreshes skills and familiarity with essential maneuvers, therefore staying qualified to fly the aircraft. This training is conducted in-unit.
3.4.1.4 Continuation Ground Training. Staying qualified to fly requires completion of other recurring monthly, quarterly, semi-annual, or annual ground training events. These events cover a broad spectrum of flying-related activities to include physiological training, annual flight simulator refresher training (in normal and emergency procedures), life support training, and cockpit resource management training (CRM). CRM training focuses on enhancing crew synergy, coordinating on mission accomplishment and handling unusual emergency situations. Continuation classroom and simulator training is usually more advanced and tailored to the experience of the crew. This training is usually conducted at home station, or at a remote satellite simulator location. The focus of this training is on more in-depth systems knowledge and handling of more complex emergency procedures. This simulator refresher training normally lasts three days with four hours of academics and four hours in the simulator each day.
3.4.1.5 Initial Water Survival Training. Currently course number SV-90-A, Non-parachuting Water Survival, is the required course for large aircraft (non-ejection seat) crewmembers. The course focuses on ditching procedures to the exclusion of bailout. The BAR is concerned about two issues. First, it leaves the crew deficient in techniques of over-water bailout. Second, it encourages the belief that ditching is the preferred option. AMC/DOT is working an initiative to restore overwater bailout to the curriculum of SV-90-A.
3.4.2 Contractor Aircrew Training System The Little Rock Air Force Base C-130 classroom and simulator training (both formal school and continuation training) are normally conducted by a civilian contractor (Hughes). Their instructor corps consists mostly of retired military C-130 crewmembers with many years of C-130 flying experience. Additionally, the aircrew training system (ATS) contract requires the syllabus and instructors to be responsive to the latest changes and safety issues in the C-130. Specifically, the contractor is required to include information from safety supplements in their classroom training within 48 hours of safety supplement release. The contractor will also update the simulator scenarios to include these safety issues. The intent is to expeditiously raise crew awareness and train the force on the latest operational and safety issues affecting the C-130.
3.4.3 Comments on Continuation Training Overall, the team found C-130 initial and continuation training to be a thorough, effective and responsive process. When a new safety issue is addressed in a safety supplement, incorporating it into the simulator refresher classroom training within 48 hours, and ultimately incorporating it into training scenarios, is an effective training tool. However, the BAR found several issues that warrant comment, and which may have possible impact on C-130 training and operations:
3.4.3.1 Wide Variety of C-130 Missions and Models. Formal school training is conducted on C-130E models. While these E-models have served as a good training platform for many years, modifications (EC, HC, WC, etc.) and modernization (H-1, H-2, and H-3 aircraft) necessitate that many students undergo differences training in their particular aircraft upon arrival at home station. The burden of teaching the operation of C-130 aircraft other than E-models has been delegated to the individual unit. The number of units and personnel needing differences training grows with each new modification and modernization to the C-130. This philosophy is not consistent with an integrated training program that strives for economy of instruction and assurance of effective, standardized instruction. The team is concerned that procedures and techniques taught in-unit may not be standardized, nor receive the degree of review and scrutiny normally associated with "formal" C-130 training.
3.4.3.2 Formal School Challenges. In the past few years, the formal school at Little Rock has had difficulty keeping up with the rising training demands (i.e., the number of students to be trained). This increase in training demand has been due to a number of factors, to include: increased crew ratios for pilots and loadmasters, the "banked pilot" program (pilots trained through Undergraduate Pilot Training but delayed in being assigned to an operational aircraft due to previous surpluses in the pilot force), increased numbers of first assignment instructor pilots (or "FAIPs") assigned to C-130s, and a shortage of available C-130 instructor pilots. The result is a heavily worked training system where most training is accomplished at Little Rock. However, some students’ assignments are delayed while they await training, or they must accomplish the training at home station with in-unit waivers. The goal should remain to train all initial qualification training students at the formal school to promote standardization in operating the C-130 worldwide.
3.4.3.3 Training Video. The team viewed a training video that was developed following a Colombian Air Force ditching of a C-130. The BAR was in general agreement that this video was an effective training tool. An updated training video would incorporate the lessons learned from King 56, the Colombian ditching, the gunship mishap in Africa, and other ditching events, and would be a valuable training tool.
3.4.3.4 Ditching vs. Bailout Training. The BAR reviewed flight manual guidance for ditching and bailout. T.O. 1C-130H-1 pg. 3-64, in "Bailout Over-water" states:
"Consideration of various unfavorable factors involved in an overwater bailout limits the decision recommending overwater bailout to several specific instances: namely, when visual contact is made with land, or adequate surface help; when wind and sea conditions are such as to preclude ditching; when fire or loss of control makes ditching impossible."
3.4.3.5 This discussion clearly favors ditching over bailout in over-water situations. The BAR believes this priority needs to be reviewed and revalidated in light of available ditching information and anticipated life support / survival equipment availability. The BAR further found that there is currently no requirement to review ditching or bailout drills.
3.4.3.6 In our visits with crew members around the country, the BAR found them to be familiar with ditching procedures outlined in their respective dash ones. The overwhelming majority were familiar with the general details of the Colombian aircraft ditching. There was an awareness among the crews that ditching, even under the best of circumstances, carried the probability of extensive damage to, and immediate flooding of, the aircraft shortly after initial impact. They acknowledged a strong tendency to want to stay with the aircraft, rather than bailout and be strung out across the water--away from the majority of the available survival gear stowed aboard the airplane. The BAR believes the flight manuals should be updated for the best information available on ditching and how to prepare for and successfully execute the maneuver. An expanded discussion of the merits of ditching versus bailout in the dash one would be helpful as well. Clearly, the crews understand ditching to be an emergency procedure--the probability of success is directly proportional to conditions at the time of ditching: daylight, calm sea state, lightweight, powered flight, & favorable wind direction. Under any other conditions, the probability of success becomes marginal at best.
3.4.3.7 Related Deficiencies and Concerns
DEFICIENCY: Periodic review of ditching and bailout procedures by aircrews is not currently required.
RECOMMENDATION: The BAR recommends that the Air Force establish a requirement for all crews to review ditching and bailout procedures on the first leg of overwater missions.
DEFICIENCY: Ditching information in flight manuals is inconsistent and inaccurate.
RECOMMENDATION: The BAR recommends that Air Force work to standardize this information between models of the same aircraft and reverify the accuracy of the information contained in the flight manuals on bailout and ditching, including the advisability of each, considerations involved in the decision, and the probability of survival in each case.
DEFICIENCY: Bailout over water information in the flight manuals needs to be reviewed. By favoring ditching over bailout, flight manuals are endorsing a recognized procedure with a low probability of survival. While this may be appropriate, the BAR believes a review is warranted to include proposed survival equipment changes. Clearly, with passengers on board (depending upon their number, ages, experience, sea state, and availability of parachutes and life support equipment), ditching may well be the only option.
RECOMMENDATION: The BAR recommends that Air Force work to standardize this information between models of the same aircraft and reverify the accuracy of the information contained in the flight manuals on bailout and ditching, including the advisability of each, considerations involved in the decision, and the probability of survival in each case.
3.4.3.8 Systems Training. The BAR discovered an inaccurate belief within the crew force that the synchrophaser is responsible for most, if not all, power anomalies in this aircraft. This "synchrophaser psychosis" results in both the crew force and maintainers being spring loaded to blaming synchrophasers when other systems such as aircraft fuel, electrical, or bleed air might be involved. The BAR identified several incidents where focusing on the synchrophaser delayed identifying fuel problems.
3.4.3.8.1 A critical action "bold face" procedure was developed to address the serious situation of multiple engine power loss/RPM rollback emergencies. Results of BAR initiated flight tests have confirmed the inability of the engines to sustain combustion due to fuel starvation in certain situations. These situations can result in power losses that can be recovered by turning on the main fuel tank boost pumps and closing the crossfeed valves. If no corrective action is taken all four engines may flameout.
3.4.3.8.2 The flight manual has contained a four-engine rollback procedure for a number of years. While not a bold face item, most, if not all units, expected crew members to commit this procedure to memory, just as they would a bold face procedure.
3.4.3.8.3 This newly issued Multiple Engine Power Loss/RPM Rollback procedure has four steps that are "bold face" (critical actions which must be committed to memory). The first two addresses fuel and ensures the fuel pumps are on and the fuel system is in "tank to engine" configuration. The third directs placing all propeller governor control switches to "mechanical governing" This should remove all electrical inputs from the synchrophaser to the propeller control assembly. The final "bold face" step directs placing all temperature datum control switches to "null". This removes any electrical corrections from the TD system and returns the TD valve to a 20% bypass position. The first four steps of the procedure will allow the crew to recover from either a possible fuel starvation situation or electrically induced synchrophaser or TD system malfunction. Once the situation is stabilized, and the aircraft is in its most basic operational mode, the crew will have time to analyze the specific situation/malfunction.
3.4.3.8.4 The implications of the flight test results impact several procedures in the flight manual. For example, before the generators are turned off in the case of an electrical fire, the flight manual should be updated to address closing the crossfeed valves. This is only one example of impacts on the flight manual.
3.4.3.9 Cockpit Resource Management: Cockpit Resource Management has been an element of aircrew training for several years. Despite this training both in the class room and in the simulator, there continues to be mishaps where CRM is clearly a significant factor. Currently, annual ground training is focused on improving crew synergy and coordination to enhance safe, efficient mission accomplishment in handling aircraft emergencies. The classroom portion of the training addresses human interaction, communications and group dynamics. Simulator training includes only those crew members who have positions in the simulators and is not done by all commands. The concept is to apply classroom lessons in scenarios in the cockpit. CRM training is conceptually good and professionally presented; however, anecdotal evidence suggests that the lessons are not fully incorporated into crew behavior. It is clear to the BAR that the CRM program needs to be reviewed. If the data is available, review a random subset of pre and post CRM training mishaps. Has the training improved the mishap rate? Is CRM properly focused, or could modifications to the program improve the crews performance without adding to the training burden
3.4.3.10 Multiple Aircraft Configuration: There is considerable discussion within this document concerning various aspects of configuration control. This issue has operational impacts. During their unit visits, the BAR found that several units had more than one configuration of the same series of aircraft. This creates situations in which instrument locations, procedures and systems details are different.
3.4.3.11 Techniques vs. Procedures: A core principle in flying, both commercial and military, is the strict adherence to established procedures. It appears that small, isolated flying communities have the potential to develop, intentionally or accidentally, techniques masquerading as procedures that have not been evaluated and approved by appropriate authority. One specific example, discussed in detail elsewhere, is the technique of turning off the main tank fuel boost pumps when feeding all four engines from the fuselage tank. The BAR discussed at length mechanisms to re-establish the sanctity of the flight manual, but that requires the repair of the flight manual system and the unification of the flight manuals under a single manager.
3.4.3.12 Aircrew Experience Level: Each command designates their standards for aircrew experience. The BAR reviewed crew force experience levels and found most operating commands met or exceeded those standards. Overseas, Special Operations, and both Guard and Reserve units generally exceeded experience objectives by a large margin. These commands also exceeded the experience levels generally found in active duty CONUS combat aerial delivery units. While important to monitor, the current crew force has a realistic capability to meet current taskings safely.
3.4.3.13 Related Deficiencies and Concerns
DEFICIENCY: The BAR directed flight test identified flight manual discrepancies with respect to the fuel management in certain situations.
RECOMMENDATION: The flight manual should be reviewed to incorporate the lessons of the flight tests in relevant areas of the flight manual.
Section 4.0
Maintenance
4.1 C-130 Maintenance Training
4.1.1 The BAR sought to determine whether maintenance personnel receive adequate training to enable them to safely maintain C-130 aircraft. They examined the safety aspects of the issue by: visiting sixteen different C-130 units, interviewing maintenance and operations personnel and soliciting their views on maintenance training issues, reviewing incident reports looking for trends, listening to inputs from a toll-free hot line, and talking to depot technicians to get their views on the condition of hardware returned to the depot for repair. As a result of our investigations, two areas were selected for special consideration:
4.1.2 On-the-Job Training (OJT): Since assuming lead command responsibilities for C-130s, Air Mobility Command has continued to monitor and improve training programs. C-130 maintenance training had previously adopted a structured training program, called OJT. This approach enables highly skilled craftsmen and supervisory-level Air Force maintainers, or their civilian counterparts, to train and certify new Air Force personnel in the hundreds of maintenance actions required to maintain Air Force aircraft. As a result of this one-on-one approach, entering technicians learned their skills under the watchful eyes of experienced veterans in their respective fields. The Maintenance Qualification Training Program (MQTP) standardizes OJT for each type aircraft throughout the command. The priority for implementing the MQTP concept was to first optimize the program on the C-141, C-5, KC-135 and C-17, before tackling the more difficult C-130 with its multiple mission design series (MDS) and configurations. This program has been successful and the C-130 MQTP classes will begin in March 1998.
4.1.3 Training Program Improvements: AMC has also continued efforts to upgrade training center mock-ups and trainers, and to develop computer based training (CBT). The BAR found several areas that were noteworthy and other areas where the command was working to improve maintenance training.
4.1.4 Summary: Inputs were received from AMC, ACC, AFSOC, AFRC, and the ANG. The team did not find any maintenance training issues which have flight safety implications.
4.2 Maintenance Experience Levels
4.2.1 The BAR reviewed maintenance personnel experience levels in all of the operating commands. As expected because of their generally longer periods of service, individuals in the Guard and Reserve units generally exceeded the experience objectives, and exceeded the experience levels found in the active duty units. Although there has been a decrease in experience levels as the forces have been downsized, the team found no evidence that the decreased experience level is having an adverse affect on flight safety.
4.3 C-130 Maintenance Inspections
4.3.1 All Air Force aircraft are inspected before flight. For the C-130, aircraft inspections range in detail from the most common flightline inspections performed by aircrews immediately before flight, through all the maintenance inspections to ready the aircraft for the aircrew, all the way to a full programmed depot maintenance, or "PDM" inspection at the depot. Basic preflight and postflight inspections, home station checks, and the isochronal (calendar-based) inspection processes are usually done at the aircraft’s home base of assignment and are performed by the Air Force maintenance personnel assigned to that unit. The PDM inspection process goes on at the larger depot facilities which are set up to handle the major maintenance associated with this level of inspection effort. Each inspection is designed to look at only certain items, which cuts down on duplication of effort between inspections. Items inspected during a home station check may not be looked at during the Isochronal inspections (called "ISO" for short) or might be inspected to a different level.
4.3.2 All of these inspection efforts are directed and governed by USAF technical orders, or T.O.s, which will be explained in Section 4.6. The total number of inspection tasks that are performed on each aircraft in the fleet on a periodic basis is very large, consuming a large amount of man-hours, in order to provide aircrews with aircraft that are safe to fly. It is common practice for some minor inspections to become overdue and completed at the next scheduled maintenance event. This is authorized to allow flexibility in managing the flying schedule plus increasing aircraft availability. The BAR did not find any safety deficiencies or problems with the C-130 inspection process.
4.4 Depot Level Maintenance Impact On Flight Safety
4.4.1 The team posed the following questions: 1. Are there any flight safety concerns about depot level maintenance activities? 2. Are aircraft PDM and individual item depot overhaul activities producing aircraft and equipment that are safe to operate and maintain? The team answered these questions on PDM by looking directly at the C-130 fleet’s PDM, and its propeller system component overhaul processes, materials, and workmanship, to identify any safety concerns or problems which might make the airplane less safe to fly. They went directly to the depot facilities at Warner Robins Air Logistics Center in Robins, Georgia (WR-ALC) where the airplanes undergo major repair and their records are kept. The BAR looked especially hard at the C-130 aircraft fuel system, engine, and propeller systems. They found no significant safety issues with either aircraft or repaired parts coming out of depot level maintenance.
4.4.2 Aircraft PDM visits are based on calendar months since the last visit. C-130 aircraft are scheduled for PDMs at specific intervals, depending on their mission. During each visit to a PDM facility, the depot workers perform certain specific inspections, repairs, or refurbishment operations in accordance with a detailed PDM work package. The depot work package of repairs and inspections is agreed upon with the operational commands (e.g., Air Mobility Command, Air Force Reserve Command, and others) during the Maintenance Requirements Review Board (MRRB) meeting held annually.
4.4.3 The depot also performs any "over and above repairs" (more than what was called for in the agreement) on specific tail numbers as requested by the operational unit owning the aircraft. This might range from paint touchup work to prevent corrosion to repairs carried over as important but not critical enough to prevent safe flight. Depot-level tasks are those "heavy maintenance" tasks that call for more expertise, tools, and special heavy equipment than local flying units normally have. In addition, PDM involves inspections generated under the aircraft structural integrity program (ASIP). The ASIP is an extremely rigorous process, usually involving the original aircraft manufacturer, to ensure that the model of aircraft in question does not suffer a catastrophic structural failure. This is accomplished by performing specific structural inspections, repairs, and replacements developed by engineering analysis, individual aircraft usage monitoring, and in some cases, data obtained by full-scale fatigue testing (i.e., bending and vibrating a part over and over to simulate thousands of hours of operational service to see what happens in the laboratory instead of in flight.) This arrangement is beneficial because the equipment for large-scale repairs and fatigue testing is costly and does not need to exist at every location.
4.4.4 From the safety perspective, the key questions relating to the PDM process are: 1. Are the right inspections and repairs being accomplished, i.e., is the MRRB process correctly identifying the work that needs to be done, and 2. Is the agreed upon work being performed correctly during PDM? The Air Force’s experience with this process over the last several decades has proven the MRRB process to be effective in ensuring that the necessary safety-related depot level maintenance is identified and being performed.
4.4.5 The primary measures of success for PDM quality from the safety perspective is the number and significance of deficiencies reported by operational units upon receipt of the aircraft after its PDM visit. Team members reviewed the past two years of this data and found no safety-related problems. Although field units have expressed some concern from time to time over such issues as the quality of paint application on PDM aircraft and various minor workmanship defects, the overall quality levels are satisfactory. Reported defects were corrected or resolved to the satisfaction of the operational units flying the airplanes.
4.4.6 Component Overhaul. The Air Force has overhauled aircraft parts for many years. C-130 parts are overhauled under the Management of Items Subject to Repair, or MISTR, program. MISTR overhauls items "on-condition," i.e. when the item no longer performs satisfactorily.
4.4.7 The team visited the propeller and the synchrophaser overhaul facilities, interviewed workers, and reviewed production quality records. The BAR looked at the results of investigations into quality deficiencies as well. A review of records reveal that over 90% of all synchrophasers returned for repair had no deficiencies. A sample review of 48 synchrophasers returned for repair revealed no "repeat" offenders. The BAR found no safety related deficiencies and judged these overhaul processes to be sound and effective in producing safe, quality items. The BAR did find that five aircraft tail numbers had repeat synchrophaser problems. When these synchrophasers were tested, there was nothing wrong with them. This points to other systems on the aircraft adversely affecting the synchrophaser.
4.4.8 Related Deficiencies and Concerns
DEFICIENCY: The depot was previously unable to properly track propulsion system components.
ON-GOING RESOLUTION: The depot at Warner-Robins has initiated a serially numbered tracking program to obtain the necessary data in an effort to explain what other aircraft systems affect the synchrophaser.
4.5.1 The BAR found concerned, qualified personnel who found and fixed the problems reported by the flight crews, or who discovered and fixed problems themselves during routine inspections. However, the team saw two instances that are cause for concern. First, virtually no one in the field appeared to be sampling the fuel in aircraft fuel tanks (referred to as "pogoing" the tank, based on the use of a long hollow pole ["pogo stick"] with a collector jar at the end for visual inspection of the fuel sample). Uniform use of this procedure would more readily identify the presence of water and other impurities in aircraft fuel tanks. Second, a core principle of aircraft maintenance is being overlooked in some cases. The BAR found that some maintainers were not consistent in their use of technical order trouble-shooting procedures and the associated required follow-through maintenance actions. In particular, the team noticed the same "synchrophaser psychosis" previously mentioned had a tendency to cause maintainers to immediately assume the synchrophaser was at fault, rather than to thoroughly test it using the appropriate test equipment and procedures. There were also indications that many maintainers were unfamiliar with how to properly test the synchrophaser. This may well contribute to the trend, noted in Section 4.4 of this report, of 90% of synchrophasers sent to depot for repair showing no need for such repair.
4.5.2 Related Deficiencies and Concerns
DEFICIENCY: Maintainers are not sampling aircraft fuel as required by the T.O.
RECOMMENDATION: The BAR recommends renewed Air Force-wide emphasis on fuel sampling as part of standard maintenance operations to help identify the presence of water or other contaminants in the fuel.
DEFICIENCY: Maintainers are not always properly trouble-shooting reported synchrophaser malfunctions and may not be thoroughly familiar with the procedures required for testing the synchrophaser.
RECOMMENDATION: The BAR recommends renewed Air Force-wide emphasis on proper testing of the C-130 synchrophaser following reported malfunctions, and on more thorough training for maintenance personnel in the performance of those tests.
4.6.1 The team addressed the following questions on technical orders: 1. Are there any safety concerns in the USAF Technical Order System? 2. Are all of the books, manuals, and checklists used by personnel to maintain C-130 aircraft accurate and effective to ensure that safety is being maintained?
4.6.2 There are detailed procedures to ensure that all of these T.O.s are kept up to date and that any deficiencies discovered are corrected. Any crewmember or maintenance person can identify a deficiency by writing it up on the proper form--Form 847 for flight manuals and an AFTO Form 22 for maintenance manuals. These forms are submitted through channels to the System Program Office (SPO) who is charged with the responsibility for managing these T.O.s.
4.6.3 The BAR looked very closely at this process to ensure that all such deficiencies were being addressed in a timely manner to preserve flight safety. They found no unresolved deficiencies in this process, both for flight manuals and maintenance manuals. However, the same issues that exist with aircrew flight manuals exist with maintenance technical orders as well: a large backlog of changes to produce and post, multiple change pages to search through to accomplish even relatively simple maintenance actions, and scarce funding to solve the problem. The BAR is concerned that, while the veteran line craftsman may know where to look for all the changes when completing a repair, the less experienced maintainer may miss a critical step that is buried in a series of supplements, with potentially serious consequences. It will require a significant investment in resources and time, over $20 million and approximately two years, to fix the C-130 alone using current manpower levels to correct.
4.6.4 Initiatives are also underway to convert USAF technical manuals from the old, expensive and time-consuming paper format to the newer digital format. New CD-ROM technology offers many benefits, including a reduction in the annual $2.5 million cost of maintaining our T.O.s. This conversion faces many obstacles, including the cost of conversion as well as training and equipping field units to handle electronic data rather than paper.
4.6.5 Related Deficiencies and Concerns
DEFICIENCY: Maintenance units do not sump fuselage tanks on a regular basis leading to the possibility that water and contamination could collect within these tanks.
ON-GOING RESOLUTION: The BAR supports amendment of the T.O.s as necessary so that fuselage tank sumping is required at regular intervals.
Section 5.0
C-130 Mishap Review
5.1.1 The USAF C-130 has a very strong safety record. Introduced into the Air Force inventory in 1955, the C-130 has amassed over 14,400,000 flying hours. During this time, the Air Force experienced 142 Class A mishaps (aircraft destroyed or damaged beyond $1 million or economical repair, or where permanent disabling injury or loss of life occurs) resulting in 613 fatalities and the loss of 83 aircraft. An additional 45 aircraft were lost to combat. Since 1971, the Air Force has experienced 63 C-130 Class A mishaps resulting in the loss of 54 aircraft.
5.1.2 The C-130 has followed the USAF trend of fewer mishaps per flying hour over the years. The BAR attributes this to a number of factors including, but not limited to, increased systems reliability, improved components, improved training, and the USAF safety program.
5.1.3 The C-130 program implements the USAF safety program in two ways. The System Safety Group consists of all C-130 users and is focused on mishap prevention. The Material Safety Task Group tracks the status of all appropriate USAF C-130 mishap recommendations and ensures the appropriate resources are applied and progress is being made on the corrective actions resulting from these recommendations. Safety is also integral to C-130 training and the content of the technical orders.
Figure 5-1
USAF Historical Mishap Vs. C-130 Mishap Rates:
1957-1997
5.1.4 The cumulative class A mishap rate for the C-130 is 0.99 (class A mishaps per 100,000 flying hours). This safety record is noteworthy when considering the missions and environments in which the USAF flies the C-130 (see Section I, Operating Environments and Missions). The C-130 rate is well below the Air Force rate of 1.37 and comparable to the C-5 rate of 0.91.
5.2.1 The U.S. Navy and U.S. Coast Guard also fly C-130 aircraft. The Navy has flown C-130s since 1961. Their lifetime class A mishap rate (1961-1998) is 0.87 mishaps per 100,000 flying hours, but they’ve had zero class A mishaps since 1977. The Coast Guard only has flying hours available back to 1983. From 1983 to 1997, their class A mishap rate is 0.30 (only one mishap). Between 1961 and 1982 they experienced three other class A mishaps.
5.2.2 With almost 25 million C-130 flying hours world wide, there have been 284 aircraft lost to mishaps: 194 Class A mishaps, 14 ground mishaps, four other mishaps, and 72 lost in combat. Data on the causes of these mishaps (not including combat losses) is depicted in Figure 5-2. Of the approximately 2,100 aircraft built in the last 44 years, approximately 1,800 are still in service.
Figure 5-2
5.3 Uncommanded Power Reductions
5.3.1 Analysis of Reported Uncommanded Power Reductions. Table 5-1 shows the known reported incidents of uncommanded power reduction since the Air Force began keeping these records in 1983. Note that none of these are Class A mishaps, and that the list does not include the Portland King 56 mishap.
Table 5-1
Breakdown of 71 Reported Incidents:
Electromagnetic Interference (EMI) 03
Fuel Starvation 03
Synchrophaser 07
Aircraft Electrical System 24
Unknown 34
5.3.1.1 Electromagnetic Interference (EMI): EMI from the HF radio antenna accounted for three of 71, or 4% of the reported incidents. One incident resulted from an improperly connected HF antenna. Shielding has worked in keeping the number of electromagnetic interference incidents down.
5.3.1.2 Fuel Starvation: During the course of reviewing the reported C-130 power-loss incidents, three events were of special interest due to their apparent similarity to the Portland mishap. These events were clearly sequential engine power-loss events, not the traditional simultaneous engine power-losses historically associated with synchrophaser or electrically related power-loss events. It was postulated that these events were really fuel starvation events and an effort was made to learn more about them. Additionally, none of these events resulted in a mishap so the corrective actions taken by the crews were also of interest since the actions may help improve existing procedures. To learn more about each of these incidents, the team contacted the flight crews for each incident. In the process of examining the details surrounding these three events, another unreported event was discovered which also exhibited the symptoms of fuel starvation. This event was also examined, bringing the total looked at to four. A discussion of each of these incidents is contained in Section 5.4.
5.3.1.3 Synchrophaser: The synchrophaser accounted for only seven of 71 or 10% of the reported incidents. Of these seven incidents, three were due to water getting into the synchrophaser unit, two were due to interface wiring bundle problems, and two were due to internal synchrophaser problems. This is consistent with the fact that 90% of the synchrophasers returned to the depot from the field for deficiencies under the product quality deficiency report (PQDR) system tested within operational limits.
5.3.1.4 The PQDR is the unit’s way to get feedback from depot when they send a defective part in for repair. The unit requests PQDR action on a specific part by providing the specifics of the malfunction to the depot. The depot analyzes and repairs the part, then identifies in writing to the sending unit what they found. The synchrophasers examined by the depot were found to be within acceptable tolerance and adjusted back to centerline, then returned to the field. The small percentage of defective synchrophasers caused the team to look more toward other potential causes for engine rollback and other uncommanded power reduction phenomenon.
5.3.1.5 Aircraft electrical system - This system may have contributed to 24 of 71 or 34% of the reported incidents. The electrical system’s components may have fed faulty or fluctuating power, or data signals, to the synchrophaser or to the electrical controls within the propellers themselves. Possible problem sources include the failure of generators, generator control panels, and the essential AC bus. Faulty electrical system components may have also played a part in the majority of the 34 incidents with unknown causes, making it a category of considerable interest. The ongoing FMECA should reveal additional information on what part the aircraft electrical system plays as a potential cause of problems.
5.3.1.6 Unknown - Thirty-four of 71, or 48% of the reported incidents are classified as caused by unknown reasons. Most of these are strongly suspected to be caused by the aircraft electrical system (old synchrophaser interface wiring bundles, bad grounds, old power system powering newer components, etc.).
Figure 5-3
5.3.1.7 Since completing the installation of the solid state synchrophaser in June 1992, there have been no reported rollbacks attributed to internal failure of the synchrophaser and only four rollbacks with unknown causes. This indicates that efforts to clean up the electrical power and improve synchrophaser performance have been beneficial. Modifications include the constant voltage transformer (Dec 88 - Dec 93), solid state synchrophaser (Jan 90 - Jun 92), and HF antenna lead shielding (Mar 92 - Mar 98 [est.]). The ongoing FMECA should identify any additional potential problem areas with the aircraft electrical system.
Table 5-2
Breakdown of 71 Reported Incidents by Tail Number (Year of Manufacture):
55 - 01
56 - 03
57 - 02
58 - 00
59 - 00
60 - 00
61 - 05
62 - 03
63 - 08
64 - 12
65 - 07
66 - 02
68 - 05
69 - 05
70 - 01
72 - 00
73 - 03
74 - 12
78 - 00
79 - 00
80 - 00
81 - 00
82 - 00
83 - 00
84 - 00
85 - 01
86 - 00
87 - 00
88 - 00
89 - 00
90 - 00
91 - 00
92 - 01
93 - 00
94 - 00
95 - 00
96 - 00
(Note: Intervals between years reported [e.g. 75-77] reflect no C-130 purchases by USAF)
5.3.1.8 Only two of the incidents reported thus far occurred on aircraft built after 1974 (see Table 5-2). The majority of the reported incidents (63 of 71 or 89%) occurred on aircraft built and fielded between 1961 and 1974. The lack of incidents associated with newer aircraft, coupled with the fact that there have been only two incidents caused by internal failure of the solid state synchrophaser, combined to discount the solid state synchrophaser as a likely cause of the problems experienced.
Table 5-3
Breakdown of 71 Reported Incidents by C-130 Mission Design Series:
C-130A 04
C-130B 03
C-130E 26
C-130E (ESU) 01
C-130H-1 12
C-130H-2 01
C-130H-3 01
AC-130A 01
AC-130H 02
DC-130A 01
EC-130H 04
HC-130H 04
HC-130N 02
HC-130P 04
MC-130E 03
WC-130H 02
5.3.1.9 Basic C-130 aircraft (A, B, E and H models) accounted for 68% or 48 of the 71 incidents (see Table 5-3). These aircraft, however, comprise the overwhelming majority of the C-130 fleet (75.8% of the Air Force’s fleet, or 526 of 694 as of April 1, 1997). Our modified aircraft, with their additional systems installed, tend to have a higher percentage of reported incidents of RPM rollback (see Figure 5-4).
Figure 5-4
Fleet Composition vs. Incidents
5.4 Possible Fuel Starvation Incidents
5.4.1 Three of these 71 incidents, although initially reported as RPM rollbacks, were determined by the BAR to have occurred due to fuel starvation. Additionally, one other unreported incident was also determined to be caused by fuel starvation. In each case, this determination was made based upon the incident report (if reported), crew testimony, and system analysis. Each of these incidents is discussed below.
5.4.2 Spring 1991 Incident, HC-130N. This aircraft departed home station in the morning and refueled three helicopters. It landed at a second air field, refueled, and prepared to refuel helicopters again. In the afternoon, it refueled three helicopters in a short amount of time. During this swift refueling operation, the aircraft ended up in a "secondary fuel management" condition. The flight engineer accepted this position as a cost of being able to offload fuel to receivers rapidly. However, when refueling operations were complete, the flight engineer worked to get back into a primary fuel management position. This was accomplished by "scavenging" small amounts of fuel remaining in the auxiliary and external tanks, using the remaining fuel in the fuselage tank, and balancing main tank fuel with two main tank pumps on and the other two off. According to testimony, primary fuel management was achieved, all main tank pumps turned on, and the aircraft fuel panel in tank-to-engine configuration prior to the aircraft entering a low-level route for its return to home station.
5.4.2.1 After a short period of flight in the low-level route with light turbulence, one of the torque gauges began to fluctuate slightly. After confirming that this engine was not the master engine for the synchrophaser, the torque on number 3 engine gauge was observed to drop significantly. The remaining engines also began to lose power as well. Nearly simultaneously with the power-loss, the aircraft commander took control of the aircraft, initiated a climb, and the flight engineer began to execute the four-engine power-loss procedure.
5.4.2.2 While the flight engineer was executing the four-engine power-loss procedure, the load master stated, over the intercom, that the number 1 engine had flamed out. The aircraft commander visually scanned the number 1 engine and confirmed its condition. The flight engineer, while on the floor by the pilot’s seat preparing to pull the synchrophaser’s AC circuit breaker, also confirmed the condition of the number 1 engine. The copilot, reacting to the load master’s observation and the pilot’s verification was ready to feather the number 1 engine and was awaiting confirmation from the flight engineer before doing so.