Military

T700

T700 is one of the most prevalent engines in the DOD. It provides power to the AH-64, UH-60, AH-1Z and UH-1Y. It is used in the AH-1Z (H1 Helicopter upgrade) with two T700-GE-410 engines and the UH-1Y (H-1 Helicopter Upgrade) with two T700-GE-401C engines. It is a stable platform that has stable data in multiple formats. The 1500 horsepower T700 engine, which powers the the AH-64 Apache, Black Hawk, Seahawk, and Pavehawk H-60 helicopters, is organically repaired by the Army at the Corpus Christi Army Depot [CCAD]. It is similar to the CT7 commercial engine that powers the Bell 214ST and Saab 340 aircraft used in commercial aviation. Both engines are manufactured by General Electric. Approximately 70 percent of the T700 workload is performed in the depot; 30 percent is done on contract.

The gas turbine has been found to be the most effective power plant for military helicopters from a weight, reliability, and maintainability standpoint. However, because of the relatively small size of the engines used in helicopters, turbine-powered machines have suffered somewhat when it comes to fuel economy.

With the T700 engine, even this deficiency has been overcome. The T700 uses 20 to 30 percent less fuel than its predecessors. In all these applications two engines are installed to give an additional margin of safety and ability to complete a mission. The T700 engine, while producing 10 percent more horsepower than the engines used in the Huey and AH-1S Cobra-TOW, is 40 percent lighter, weighing slightly over 400 pounds.

The twin engines of the UH-60A and AH-64 provide good single engine performance, which means that the craft can get home even if it loses one engine. The widely separated engines on both choppers reduce- the chance that both engines are knocked out. The T700 engine uses suction type fuel delivery rather than fuel pumps at the fuel tanks. Thus, if the fuel line is severed, fuel is not pumped into the air creating a fire hazard; instead the fuel lines are sucked dry. The self-sealing fuel tanks can survive a hit from a 23-mm HEI round.

The T700 engine provides for greater ease of maintenance. It requires about 15 minutes to replace any of the two dozen flightline replaceable accessories, and all field maintenance can be done using only ten standard tools found in any mechanic's toolbox. The engine itself can be easily removed from the aircraft. During the YAH-64 flight test program, two men demonstrated that they could remove an engine in only 25 minutes. Since the engine is composed of only five separate modules, once it is out of the aircraft, the faulty module can be replaced and the engine reinstalled. Replacement of all five modules takes only about an hour and a half.

Airframe development contracts for the Utility Tactical Transport Aircraft System (UTTAS) were awarded to Boeing Vertol and Sikorsky Aircraft in August 1972. By the close of the fiscal year the contractors had completed design layouts, released detailed drawings, and subcontracted for long, lead time hardware. Wind tunnel testing, computer simulation Of aircraft handling qualities, and building of the static test model, ground test vehicle, and flyable prototypes had begun. Tests of the General Electric T700 engine, which will power the UTTAS, indicated that horsepower output did not meet specifications. Efforts to correct the deficiency, including the redesign of the power turbine, were undertaken.

Corpus Christi Army Depot teamed with General Electric to incorporate Lean and Six Sigma into the T700 engine product line to reduce engine turnaround time and improve work processes and shop flow. On 18 September 2000 representatives from GE, CCAD and the Aviation Missile Command formally announced the signing of the T700 Engine and Component multi-million dollar contract. As the program progresses, savings to the Army should be $8m to $10m a month. The strategic alliance between Corpus Christi Army Depot (CCAD), General Electric (GE) and the Army's Aviation Missile Command (AMCOM) was signed into effect on 14 September 2000. CCAD, GE and AMCOM are formalized this alliance to bring together the overhaul and repair expertise at CCAD with General Electric's technical expertise as the manufacturer of the T-700 family of engines. The results expected were increased production rates, reduced turn-around times (TAT), and increased time between required overhaul of all GE products overhauled at CCAD.

AMCOM facilitated the alliance in bringing about the agreement that will mean GE providing complete parts support for the GE products to CCAD production operations. The resulting contract came after a focused, three-month effort between CCAD, AMCOM and GE personnel.

The entire T700 family of engines and components were affected by this agreement. It enabled CCAD to launch into a future command engine platform. These engines are currently in use in many of the core rotary wing aircraft utilized by the American Armed Forces today--the Army Apache and the Black Hawk, the Air Force Pavehawk, and the Navy Seahawk. These aircraft and the systems that power them are remaining in service longer than original expectations. The combined experience brought into this alliance went a long way in improving the longevity of the T700 engine and the aircraft they power.

New technologies and combined process re-engineering within the CCAD-GE-AMCOM alliance will help increase CCAD T700 overhaul production, a vital step to improving Apache and Black Hawk readiness. Bringing GE into the CCAD/AMCOM team secured a direct link to the corporation that designed the engines for process and technical improvements. CCAD eliminated a continuing problem of parts availability shortages by ensuring GE is responsible for total parts support for their products. The depot will supply them with depot workload requirements and they project, manufacture and deliver all parts needed to ensure these engines are built to the specifications necessary to reduce the TAT's and produce a reliable product for the field.

Thanks to its use of Six Sigma and Lean Thinking process improvements and partnerships with industry, AMC's Corpus Christi Army Depot dramatically increased its T700 engine production turnaround time and efficiency, according to CCAD officials. The T700 engine turnaround has increased its efficiency by 83 percent -workers are now producing 1.6 units, instead of 1.2 units -and in less time. In fact, it now takes workers about 100 days to produce engines, a decrease of 161 days since the year 2000. This produced 900+ hours MTBR (mean time between replacement) (vs. ~309 hour engine life before Lean and Six Sigma).

CCAD signed the partnership with General Electric in September 2000 to reduce engine turnaround time, increase engine time on wing, implement commercial best practices, and improve processes and shop flow. This partnership has led to the creation of material kits for engines and modules; a depot overhaul process that has reduced the amount of parts on the "critical list," while advancing the material release of parts during a surge; has decreased engine turnaround times; and has increased the number of engines, cold section modules and power turbine modules shipped to customers.

Low power is the major cause for engine removal in the Navy's H-60 fleet. For SH-60B, SH-60F and HH-60H aircraft, powered by two T700-GE-401C turboshaft engines, if you spend time on preventive maintenance (such as engine washing), aircraft readiness and engine performance will improve. The T700 engine is unique in that it has a built-in integrated particle separator (IPS) blower as part of the engine's accessory gearbox. It was designed to separate sand and dirt from inlet air and blow the particles out before entering the compressor inlet. However, operating in desert environments has posed a major problem: Too much debris makes it past the IPS and enters the compressor. These tiny particles erode compressor blades and coat hot section (gas generator turbine) parts, which plugs cooling air holes, therefore decreasing hot-section efficiency.

NAVAIR and the T700 engine team have been working to improve engine life in this environment. They found that preventive-maintenance washing procedures are critically important. Based on lessons learned during Desert Storm and Desert Shield, a hot-section wash-sprayer nozzle was developed to perform hot-section cleaning in the T700 engine. Hot-section cleaning is done by installing a wash nozzle into one of the engine's igniter plug ports and spraying soap solution (engine gas path cleaner) on the hot-section parts, while the engine is motored. During 2003 for the H-60, and 2004 for the Marine's AH-1W Super Cobra (T700-GE-401 engine), the T700 fleet support team (FST) at the Naval Aviation Depot, Cherry Point, N.C., investigated the engine-wash procedures, clarified the procedures, and updated locally manufactured tools and support equipment needed to support wash requirements.

A conditional requirement was established to perform hot-section cleaning after the last flight of the day if flying in a desert environment. The timeframe allowed some flexibility so there was no interference with the aircraft's schedule during the day. Making it a requirement to perform the hot-section wash in a desert environment is one of the steps the T700-engine team has taken to preserve the fleet's T700 -engine life and improve readiness.

Several Navy H-60 squadrons that consistently followed these procedures didn't have to remove a single engine because of low power during their six-month deployment. Results also revealed that, in some cases, engine performance was increased. While this was not always the case, there have been fewer engines removed for low power, compared to previous years, and we expect to see more improvement in the future. Based on the positive results from the Navy's H-60 fleet, the same cleaning cycle has been applied to the Marine's AH-1W Super Cobra.

Maintaining engine readiness by preventive maintenance increases engine availability and allows the aircraft to be available for mission accomplishment. Navy and Marine Corps aircraft continue to battle harsh flying environments, but hot-section washes have proven to be successful by improving engine life. Hot-section washing after operating in a desert environment has become an effective aircraft-readiness tool for the T700-engine program.




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