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H-46 Sea Knight Upgrades

The H-46 Sea Knight Block Upgrade provided for installation of increased fuel capacity stub wings and an emergency helicopter flotation system. The H-46 Dynamic Component Upgrade provided for safety, engineering and electronic improvements. Modifications to improve the Sea Knight continued during 1998, with the installation of a new rotor head and upgraded transmission that improved flight and rotor controls, and eliminated current rotor head inspections. Sixty percent of the H-46 fleet had been modified by 1998, and the program completed fleet installations in FY 2000. Two additional upgrades to the H-46 include installation of the ARC-210 radio and night vision goggle heads up display, concurrently being installed with the integrated communication navigation control system modification. The communication navigation control system installations were 60 percent incorporated into fleet aircraft by 1998. These modification programs completed by the end of FY 2000. Additionally, program managers oversaw a blade-balancing modification to the H-46 during 1998. This modification reduced aircraft vibrations and increased reliability of the airframe and rotating subsystem components.

The current H-46 Engine Condition Control System (ECCS) has several failure modes, which cause engines to shut down in flight; this presents a significant safety hazard to the fleet. Three bulletins have been issued by NAVAIR to inspect for system deficiencies. A formal system safety analysis utilizing historical failure data defines this as a Category One hazard and predicts six to seven failures per year. In the three and a half years before this upgrade was initiated there were 35 hazard reports (HAZREPs) issued documenting this failure mode, and it is estimated that 20 more occurred that were not reported through the HAZREP system. The aircraft has a limited single engine-operating envelope and is vulnerable to engine failure while flying and hovering over water.

There have been five aircraft lost at sea in which pilots reported engine failure as the cause of the mishap. The aircraft were not recovered and therefore, the specific engine failure mode could not be determined, but it is likely that ECCS caused some of the engine failures and ultimately led to the loss of aircraft. The proposed solution to this safety problem is to convert to an alternative Engine Control System (ECS) utilized by the commercial varianats of the H-46. The proposed ECS will eliminate the safety failure modes, has a proven track record, needs only slight modification for military use, increases reliability, and will increase aircraft capability through increased engine responsiveness. Implementation will require configuration changes to the airframe and the engine. This is an urgent safety issue that must be resolved to eliminate future loss of crew and aircraft. This modification was installed on 65 H-46D aircraft (all active); and is being installed on 226 CH-46E aircraft (202 active + 24 reserve).

The contract for Proof of Concept, validation and verification (val/ver) kits for this Non-Development Item (NDI) was awarded May 1999, and the Engineering Change Proposal (ECP) was approved Jun 2000. Validation installation for D-model was completed 2nd quarter FY2001, followed immediately by Electromagnetic Interface (EMI) testing and Verification installation in 3rd quarter FY2001. Production installations in Navy D-models are complete. The CH-46E validation/verification installation and Electromagnetic Compatibility (EMC) testing are completing final production E-model installations are in process as of 2006.

T58-GE-16 reliability and performance trends were unacceptable prior to 2001 and were severely impacting Fleet safety, readiness and war fighting capability. Without corrective action, the T58-GE-16 Mean Time Between Repairs (MTBR) was projected to fall below 320 hours b

FY2002 and would require 309 major repairs per year. The NAVAIR System Safety Team determined that the Hazard Risk Index (HRI) for the T58-GE-16 was "IIC" (critical, occasional) and trending towards "IIB" (critical, probable). The CH-46E Helicopter must be logistically supported until at least 2015; however T58-GE-16 support costs were being driven to unaffordable levels. This program will drastically improve Fleet operating safety and readiness, while providing tremendous reductions in maintenance man-hours and Operations & Support (O&S) costs. Funds support production and procurement of a T58-GE-16 engine core or "Gas Path," depot overhaul of key engine accessories, incorporation of all approved engine Component Improvement Program (CIP) changes, and depot final assembly of manufacturer delivered "Gas Path" with accessory components. This program is projected to restore a 900-hour (MTBR), improve performance to the original power specification, and reduce the major engine repairs per year to 165 in FY2006. This modification will be installed in 223 aircraft (199 active + 24 reserve).

Congress approved $3M plus-up in FY2001 for risk mitigation, prototypes, and non-recurring engineering; the contract for these efforts awarded in Jan 2001. The prototype engine gas path modules were delivered in Apr 2002, and the engine prototypes were completed in Jul 2002. A Low Rate Initial Production (LRIP) contract was awarded in Aug 2002, and gas path module deliveries started in Oct 2003 with the first ERIP configuration units fielded to the fleet in Mar 2003. Approval for Full Rate Production (FRP) was granted and the first production was ordered March 2003. Initial Operational Capability (IOC) was reached in Dec 2003 and installations are ongoing.

The power generation system was the cause of ten hazard reports (HAZREP) in the three years before this upgrade was initiated. The causal factor has been traced back to the generators and the voltage control system. Two incidents resulted in dual generator failure, and several incidents resulted in aircraft smoking/fires. (One of those fires was caused by flammable fluid ingestion into the generator that turned a hydraulic leak into a massive fire that consumed the entire aircraft in a Class A mishap.) A formal system safety analysis utilizing historical failure data defines this hazard as a Category One hazard and predicts two to three failures per year. This is an urgent safety problem that must be alleviated to eliminate loss of life and aircraft. The proposed solution is to modify the power generation system to eliminate the safety problem, provide cleaner power to sensitive avionics components, improve performance of the generator to meet the power demand for future electrical installation in the aircraft. This modification will be installed in 226 CH-46E aircraft (202 active + 24 reserve).

RCM analysis of Permanent Magnetic Generator (PMG) failure modes, and risk hazard analysis indicates that risk can be mitigated with a combination of replacing PMG and main generator power wiring, and inspecting to ensure proper clearances between hydraulic lines and electric power wire. This mod will be installed on 188 aircraft (164 active + 24 reserve).

Aircraft Integrated Maintenance System (AIMS) is a Commercial Off The Shelf (COTS) vibration monitoring system to be permanently installed in the aircraft. AIMS is a comprehensive set of aircraft monitoring hardware and support software. It interfaces with the cockpit crew Control Data Navigation Unit (CDNU), which has extensive software upgrades. The purpose of the system is to build support equipment functions into the aircraft as a permanent installation. Thus, AIMS will eliminate most H-46 peculiar support equipment requirements. This equipment will provide aircrews feedback on aircraft condition and engine performance, which enhances the ability to predict catastrophic failures and reduces maintenance costs. In 1997, PMA226 fielded new vibration equipment to a small sample of H-46 aircraft and implemented a 100-hour vibration monitoring check. Since implementation, vibration monitoring has been instrumental in predicting (and preventing) impending component failures. For example, vibration data was received from an aircraft that had undergone three aft transmission removals for input pinion seal leakage. Analysis of the vibration monitoring data revealed a major problem with #2 engine. Further investigation of the engine revealed impending failure of the right angle drive bearings. Failure of the engine may have resulted in damage or loss of the aircraft. Another example is an aircraft that, while performing a 100-hour vibration check, experienced aft transmission vertical vibration levels exceeded acceptable limits. Further investigation revealed impending failure of the electrical generator. Without vibration monitoring, the problem with the generator would have gone undetected until catastrophic failure. Failure of the generator may have resulted in an electrical fire and/or collateral damage to the aircraft.

This modification will be installed in 154 aircraft (130 active + 24 reserve). Contracts to integrate the COTS into the H-46 aircraft, design an installation kit, modify Control Data Navigation Unit (CDNU) software, and prepare technical data were awarded in Jun 2003. Prototype kits delivered in Feb 2004, the hardware Design Review (CDR) was held in July 2004, and the software CDR was completed in August 2004. Validation/verification completed in May 2005 and Electromagnetic Interference (EMI) testing in July 2004. The first production lot delivered in January 2005 and production installations are ongoing.

Safety Improvement Program

The Safety Improvement Program was directed by Chief of Naval Operations (CNO) letter 7100 serial N880F/7U660758 dated 10 Jan 97, and approved as an Abbreviated Acquisition Program (AAP) by the Program Executive Officer (PEO) on 24 Oct 97. This program contains the following Engineering Change Proposals (ECP):

1. HYDRAULIC SYSTEM UPGRADE and UTILITY HYDRAULIC SYSTEM REDESIGN: This ECP was completed in FY2000, but the fleet has experienced ongoing problems with the hydraulic system following installation of the modification. The Utility Hydraulic System Redesign will assess the overall configuration of the hydraulic system and correct deficiencies to improve system performance. This modification will be installed in 177 CH-46E aircraft (153 active + 24 reserve).

2. LOWER DUAL BOOST ACTUATOR (LDBA): The housing for the actuator is highly susceptible to stress corrosion cracking. The material wear and housing cracks have resulted in LDBA malfunction. The pilot cannot control the drive direction of the helicopter, a potentially life threatening situation. This program will procure a redesigned actuator housing that eliminates the failure mode in the LDBA. This modification will be installed concurrent with Fleet Exchange (FE) repairs. This modification will be installed in 177 CH-46E aircraft (153 active + 24 reserve).


4. RUNNING ENGINE WASH: This ECP is complete.


6. ALQ-157 INFRARED COUNTERMEASURES (IRCM): This ECP is an Aircraft Survivability Equipment (ASE) modification to improve aircraft operation/maintainability/survivability in combat operations. Operation Iraqi Freedom (OIF) after action reports indicated the reliability and maintainability (R&M) of the IRCM system was not sufficient to support sustained combat operations. The Original Equipment Manufacturer (OEM) designed a R&M improvement for Foreign Military Service (FMS) users that is being installed on CH-46E helicopters. This improvement will be installed in 196 CH-46E aircraft in support of OIF II.

7. AN/ALE-47 COUNTERMEASURES DISPENSING SYSTEM (CMDS): This ECP is an Aircraft Survivability Equipment (ASE) modification to improve aircraft operation/maintainability/survivability in combat operations. This safety improvement upgrades the AN/ALE-39 (CMDS). It improves the reliability, reduces fleet operational cost and enhances the ASE capabilities of the CH-46E aircraft operating in hostile environments by addressing the problems of "Things Falling Off Aircraft" (TFOA) and uncommanded dispensing of countermeasures. This improvement will be installed in 214 CH-46E aircraft in support of OIF II.

8. AN/AAR-47(V)2 MISSILE WARNING SET INSTALLATION: This ECP is an Aircraft Survivability Equipment (ASE) modification to improve aircraft operation/maintainability/survivability in combat operations. The current system has a high false alarm rate resulting in premature flare launch. The modification will improve reliability in missile protection by reducing the false alarm rate, which in turn will conserve flares. This improvement will be installed in 214 CH-46E aircraft in support of OIF II.

9. HH-46E SEARCH AND RESCUE (SAR) CONVERSION: All Navy H-46Ds have been retired leaving the Marine Corp as the sole operator of the H-46D Type-Model-Series (TMS). The high flight hours on the HH-46Ds airframes, poor engine reliability and obsolescence issues make this aircraft difficult and expensive to operate and maintain. This ECP converted 3 CH-46E helicopters to the HH-46E configuration to perform the SAR mission, and permitted retirement of the H-46D TMS.

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Page last modified: 07-07-2011 02:32:38 ZULU