F-22 Raptor Other Testing
Other F-22 testing includes wind tunnel, materials, and ejection seat sled testing; the facilities sections include the Air Combat Simulator, the Vehicle System Simulator, the Fuel System Simulator, and the Avionics Integration Laboratory.
WIND TUNNEL TEST PROGRAM
The F- 22 wind tunnel test program was conducted during the period beginning with contract award in August 1991 and running through September 1996. During this period, a total of 76 wind tunnel tests were conducted, utilizing 23 models, in 15 different government and private tunnels, for a total of 17,689 test hours.
Government test facilities included NASA's large wind tunnels located at the Langley (Virginia), Ames (California), and Lewis (Ohio) Research Centers. Air Force test facilities at the Arnold Engineering Development Center (AEDC), Tullahoma, Tenn., were extensively used for transonic and supersonic testing, including weapon separation testing. Additional testing was conducted at privately owned facilities including the transonic facilities at Boeing in Washington, Calspan in New York, NTS and MicroCraft in California, Lockheed Martin Aeronautical Systems in Georgia, and LAMP in Germany.
Approximately 35 percent of the test hours were obtained in low speed facilities, 55 percent in transonic facilities, and 10 percent in supersonic facilities.
These wind tunnel tests were in addition to testing of the YF- 22 prototype configuration testing, where 19,195 test hours were conducted during the demonstration/validation (dem/val) phase. An additional 7,005 test hours were conducted during pre dem/val.
A grand total of 43,889 wind tunnel test hours have been accumulated on the YF -22 and F- 22 configurations.
All of these wind tunnel tests were conducted to support the F-22 air dominance fighter's design and flight certification processes. The tests were done to validate design requirements, verify system performance, optimize system design, validate analytical methods and models, and to reduce identified high risk areas to a moderate or low value, and preclude medium risk from becoming high risk items.
More specifically, the F-22 wind tunnel tests were used to develop and evaluate various aircraft configurations, determine engine/inlet compatibility and stability, determine inlet performance, determine nozzle characteristics, determine the F- 22 drag measurements in detail for performance predictions, provide air load data for analysis, determine stores and alternate Mission Equipment (AME) separation trajectories, determine stores compatibility, determine aeroelastic stability, and generate stability and control data for use in control law development and in the full mission flight simulator.
The F-22 Engineering and Manufacturing Development (EMD) wind tunnel test program was divided into two primary test disciplines: (A) aerodynamics and (B) propulsion.
Aerodynamics: The major objectives of the aerodynamic tests were to:
- Refine the F-22 configuration, with and without external stores), to validate the aerodynamic characteristics, develop an aerodynamic database for the full flight envelope, including performance and stability and control parameters.
- Determine aerodynamic loads/pressure distributions for the F-22.
- Determine safe launch characteristics of internal and external stores throughout the service envelope and determine jettison envelopes.
- Provide experimental data for validating analysis of F-22 flutter margins throughout the flight envelope.
- Assess aeroacoustic loading resulting from the propulsion air induction system, fuselage and wing separated flows due to high angle of attack flight, and disturbed flow due to weapons bay cavities and wing mounted external stores.
- Develop air data calibration database.
- Obtain aerodynamic loads data on the canopy during ejection sequence in support of the full scale sled model design.
Propulsion: The major objectives of the propulsion tests were to:
- Refine the F-22 propulsion system configuration for EMD and validate its performance.
- Determine inlet, inlet bleed, and inlet bypass characteristics and effects on external aerodynamics.
- Determine nozzle jet/vectoring effects on external aerodynamics.
- Evaluate ice accretion on the inlet lip and duct, and select an ice detector type and location.
The F- 22 materials testing program was one of the most thorough of any aircraft development program in history. Not only were thousands of coupons (small samples) tested, but nearly 120 subscale and full scale producibility articles were also manufactured before actual aircraft parts production began.
More than 13,000 coupon tests were conducted on six different types of the composite materials, including more than 5,600 trials of IM7/5240 (bismaleimide (BMI) material), nearly 4,300 on IM7/977-3 (epoxy), and nearly 2,000 on IM8/8320 (thermoplastic). More than 1,400 Durability and Damage Tolerance (DADT) tests were also done on the six composites.
Metals were also extensively tested, as more than 5,300 static and DADT tests were done on six materials. More than 1,700 static tests were done on titanium fittings samples, while more than 1,900 DADT tests were run. More than 400 static tests (and 253 DADT tests) were run with aluminum berilium (Al Be) samples, and more than 430 DADT tests were run on aluminum samples for aircraft primary structural parts.
Testing was also conducted on full and subscale parts. More than 80 composite producibility articles were manufactured, including fuel doors, exterior skins, inlet duct skins, bonded assemblies, resin transfer molded (RTM) bulkheads, frames, and spars, and access panels. More than 20 metal producibility articles were built, including Hot Isostatic Pressed (HIP) castings, electron beam welded articles, titanium main frame forgings, and large aluminum bulkhead forgings. Producibility articles for Invar (a metal) tooling for composite parts were also built, as were high temperature epoxy tools.
EJECTION SEAT SLED TESTING
The F -22 Sled Test Integrated Product Team (IPT) successfully completed the safety of flight test program at the Air Force's ejection seat proving grounds at Holloman AFB, N. M., in February 1997. This test facility consists of a 50,000 foot long track and the Air Force provides the required telemetry and high speed photography to monitor and validate escape system performance.
The six month program, formally known as the Vehicle Compatibility Sled Test Program, consisted of a series of escape system tests using the McDonnell Douglas built ACES II ejection seat (see Cockpit section for a description of the ejection seat), instrumented test mannequins simulating small (130 pounds) and large (208 pounds) human occupants, and the Dynamic Engineering Inc. built simulated F- 22 forward fuselage mated to the Air Force's Multi Axis Seat Ejection (MASE) rocket sled.
These tests demonstrated successful system sequencing, canopy jettison, and pilot recovery at speeds ranging from 0 to 450 knots equivalent airspeed (KEAS). The F- 22 escape system capabilities were proven through a dynamic sled test program that consisted of:
- A canopy jettison test that verified the safe emergency jettisoning of the F- 22's canopy.
- A static, or zero speed, zero altitude (zero/zero), escape system test that demonstrated safe pilot ejection under this severe condition.
- A 275 KEAS ejection to validate escape system performance at the high end of the Mode 1 (low speed, low altitude) area of the F- 22's flight envelope.
- A 325 KEAS ejection to demonstrated escape system performance at speeds in the lower end of the Mode 2 (high speed, low altitude) area of the F- 22's flight envelope.
- A 450 KEAS ejection that demonstrated system performance in a moderately high speed environment.
- An additional sled ejection test at 600 KEAS (the maximum safe ejection speed for F- 22 pilots) is scheduled for completion before the end of 1997.
The canopies used in these tests were built up on production tooling at Lockheed Martin Aeronautics Company in Marietta, Ga. The canopy used in the jettison test and the zero/zero test were caught in a large net placed behind the MASE sled and were refurbished and reused on two of the later tests. Recovery and reuse of these units significantly reduced sled test program costs.
The Vehicle System Simulator (VSS), or 'Iron Bird,' is a unique test facility at Lockheed Martin Aeronautics Company in Fort Worth, Texas. The simulator allows the F- 22's hydraulic and electrical systems and all of their associated hardware ( such as actuators) and control software to be tested under simulated flight conditions while on the ground.
Such ground-based testing significantly lowers program risk by allowing flight critical systems to be tested thoroughly before the airplane actually flies. It also reduces the complexity and cost of the flight test program for the developmental aircraft. The VSS can also be used to conduct tests that would be too dangerous to attempt on a flying airplane, such as dual engine flameouts and flight control actuator failures.
Prior to first flight, the VSS was used as by Chief Test Pilot Paul Metz and the Mission Control Center crew to practice the flight. After the first F -22 flies, the VSS would be used to duplicate failures and anomalies found in flight test operations.
The Air Combat Simulator (ACS), formerly known as the Full Mission Simulator, consists of two 28 foot diameter domes that contain high-fidelity models of the F- 22's cockpit and sensor suite. The F/A-22 Air Combat Simulator (ACS), an integral part of the planned IOT&E, is intended to model the dense surface-to-air and air-to-air threat and electronic signal environment that is impractical or too costly to generate in openair trails. Development of the ACS (consisting of four actual F/A-22 cockpits installed in visual scene domes and ten other manned interactive cockpit stations) continues, but delays in integrated avionics flight test and threat modelrelated development have affected ACS verification, validation, and accreditation activities. The contractor has taken steps to improve ACS realism and has a plan to provide a dense track environment in which to model F/A-22 performance. There is a risk that ACS cannot be accredited and contingency plans for additional open air testing are called for in the IOT&E test plan. The simulator is located at Lockheed Martin Aeronautics Company in Fort Worth, Texas.
The fuel system simulator (FSS) at Fort Worth replicates the complete F- 22 fuel system, including the eight internal fuel tanks and all associated plumbing. The FSS also includes the four external fuel tanks that can be carried (see External Carriage in the Weapons section), aerial refueling equipment, and the airplane's actual on-board inert gas generating system (OBIGGS). The FSS sits on a movable base for simulating pitch and roll movements. The FSS, which has been fully operational since March 1995, has been used to test the assembly and integration of the hardware and software associated with the F-22's fuel system. It has also been used to test ground and in flight refueling characteristics of the fuel system.
The flight control software and flight control laws that underpin the VMS are tested in a specialized lab at Lockheed Martin facilities in Fort Worth. The VMS Integration Facility (VIF) consists of an F- 22 cockpit and flyable F -22 hardware and software. Like the FSS, the VIF has been fully operational since March 1995.
The F-22 Avionics Integration Laboratory (AIL) at Boeing's facilities in Seattle, Wash., would be used by the F- 22 Team to integrate and test the fighter's avionics - the most advanced fighter weapon system in the world.
The AIL includes three software-development test facilities as well as a full-up avionics system integration test facility. It would be fully fitted with F- 22 avionics; other aircraft electronics such as flight and engine controls; and mission planning and maintenance-support systems.
The lab would allow F-22 software designers and system integrators on-site and throughout the country to test extensively the plane's avionics as an integrated weapons system. Avionics functions to be tested include mission management, sensor control, sensor tasking, track fusion, fire control, integrated navigation, flight path management, diagnostics management, pilot/vehicle interface, and embedded training.
The lab would contain the integrated architecture of more than 100 computer software products representing approximately 1.6 million lines of code from 15 companies along with avionics hardware, weapons and avionics-test support systems.
The AIL would use open air test configurations as well as a real-time simulation system developed by the Lockheed Martin Boeing team that allows pilots to 'fly' the full capabilities of the F-22 against simulated threats in the lab years before the fighter enters service with the U. S. Air Force in 2004.
Some of the most critical tools for a fighter pilot are the tactical displays in the cockpit. The F- 22's highly integrated avionics would deliver tactical displays that have already demonstrated unsurpassed situational awareness for F-22 pilots during a series of Part Task Simulations (PTS).
A team led by Lockheed Martin and Boeing engineers, along with software developers, and Air Force fighter pilots, have designed these displays to ensure the F- 22 pilot can extract maximum benefit from the integrated avionics.
The design goal has been to create displays that streamline critical mission information to allow the pilot to make the best decisions with minimal information clutter or overload. This allows the F- 22 pilot to be a tactician, and not just a sensor operator. The superior awareness of the mission environment gained from this approach ultimately means the pilot has the upper hand during any engagement.
Team members met regularly to'fly' scenarios in the F-22 Cockpit Development Station at the Boeing Developmental Center in Seattle. During each evaluation, pilots from the Air Force's Air Combat Command (ACC) gave designers their suggestions and recommendations.
A series of seven PTS were held to review the cockpit displays and mechanizations with the customer pilots prior to planned software block requirement freezes. These simulations were the culmination of more than five years of F -22 cockpit display development.
In PTS-7, which was completed in early 1997 was by far the most demanding and extensive of the exercises. ACC pilots flew more than 140 sorties in 13 demanding scenarios developed by the PVI team to evaluate the cockpit design of the production F 22.
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