Rolls-Royce T406

The Rolls-Royce T406 (company designation AE 1107C-Liberty) is a turboshaft engine that powers the Bell-Boeing V-22 Osprey tiltrotor. The Osprey is in service with the United States Marine Corps and United States Air Force. The engine delivers 6,000 shp (4,470 kW).

T406 / AE 1107C-Liberty
A T406 engine Nacelle on a V-22
Type Turboshaft
National origin United States
Manufacturer Allison Engine Company
Rolls-Royce plc
First run late 1986[1]
Major applications V-22 Osprey
Number built 860 (2018)[2]
Developed from Allison T56/T701
Developed into AE 2100, AE3007

Development

On December 24, 1985, the U.S. Navy selected Allison's engine for full-scale engine development and production on the U.S. Marine Corps's V-22 Osprey.[3] The Navy and Allison signed a formal contract on May 2, 1986, and the first engine to test ran six months after.[4] The T406 is based on the T56 turboprop from the P-3 or the C-130, with the free power turbine of the Allison T701 turboshaft from the defunct Heavy Lift Helicopter program. It was selected over the Pratt & Whitney PW3000 and General Electric GE27 competing for the US Army's Modern Technology Demonstrator Engine program.[5] The T406, which was originally known as the Model 501-M80C,[6] began flight testing on March 19, 1989.[7]

In 2009 the Government Accountability Office (GAO) found that the engines failed after less than 400 hours of service, as compared to the estimated life of 500–600 hours.[8] Multiple updates to the engine platform in 2012-2013 have increased the lifespan significantly.

In April 2012, the United States Department of Defense (DoD) ordered 70 AE 1107C engines for the Osprey, with options for up to 268 engines.[9]

Engines with a future block 4 upgrade are expected to deliver 10,000 horsepower (7,500 kilowatts).[10]

The MT7 gas turbines that will be used to power the Ship-to-Shore Connector are a derived design of the T406.[11]

An ongoing problem with the engines was their propensity for surging or stalling with 68 incidents reported between 2003 and October 2016 though this rate had reduced after the introduction of the Block 3 engine version. The US Naval Air Systems Command intends to award Rolls Royce two contracts to examine the effectiveness of proposed reliability improvements, the first is a software tweak to the engine management software for the compressor guide vanes that internal testing showed could improve surge margin by 0.8% at sea level and 3% at altitude. The second is the discovery that a temperature sensor at the inlet of the compressor sends incorrect readings leading to 2.5% out of 4% steady power shortfall at the compressors correct rotational speed again correctable with a software fix. In addition Bell-Boeing are developing an inlet barrier system to reduce the power loss from the engine ingesting dust and sand particles to supplement the engines existing centrifugal based particle separators as they can only do so much to improve the quality of air they receive.[12]

Design

The T406/AE1107C Liberty shares a common core with the AE 3007 and AE 2100 series of engines.

The V-22's T406 powerplants are housed in wing-tip tilting nacelles, allowing the distinctive flight characteristics of the V-22. For take off and landing the nacelles are directed vertically (90° to fuselage), while for forward flight they are rotated parallel to fuselage. The engine has been considered as a cost-effective upgrade for existing heavylift helicopters such as the CH-47 Chinook and the CH-53.[13]

Applications
  • V-22 Osprey

Specifications (T406)

General characteristics

  • Type: Turboshaft
  • Length: 78.1 in (1,980 mm)
  • Diameter: 34.2 in (890 mm)
  • Dry weight: 971 lb (440 kg)

Components

  • Compressor: 14-stage high pressure axial compressor, variable geometry vanes in the inlet and the first 5 stages[7]
  • Combustors: Diffuser annular combustor with 16 air-blast fuel nozzles and 2 igniters[7]
  • Turbine: 2-stage high pressure turbine with air-cooling in the first and second-stage vanes and the first-stage blade; 2-stage shrouded power turbine with uncooled vanes and blades[7]

Performance

See also

Related development

Related lists

References
  1. "Taking the turboshaft honours". Flight International. 11 April 1987.
  2. Howard, Sam (1 June 2018). "Rolls-Royce to deliver V-22 Osprey engines for U.S. military". Defense News. United Press International (UPI).
  3. Korn, Jim (13 November 1987). Gas turbine engine development partnerships. International Pacific Air and Space Technology Conference and Exposition. SAE Technical Papers. Melbourne, Australia: SAE International. pp. 119–132. doi:10.4271/872410. ISSN 0148-7191. OCLC 5817974566.
  4. Arvin, John R.; Bowman, Mark E. (11–14 June 1990). T406 engine development program (PDF). Gas Turbine and Aeroengine Congress and Exposition. Brussels, Belgium: American Society of Mechanical Engineers (ASME). doi:10.1115/90-GT-245.
  5. "Power derived". Flight International. 29 July 1989.
  6. Competition Advocate General, Department of the Navy. Long range acquisition estimates (FY 88 base year projections) (Report). p. 154. hdl:2027/uiug.30112104099186. Retrieved 1 August 2020.
  7. Chambers, Howard A. (1991). "Turboshaft engine development for commercial tiltrotor aircraft". SAE Transactions Journal of Aerospace. 100: 140–151. doi:10.4271/911017. ISSN 0148-7191. JSTOR 44547587. OCLC 7851143859.
  8. Sanborn, James K. (13 August 2013). "Pentagon watchdog to release classified audit on V-22 Osprey". Marine Corp Times. Archived from the original on 17 August 2013.
  9. "Rolls-Royce Awarded $598 M V-22 Engine Contract" AeroNews, 24 April 2012. Retrieved 24 April 2012.
  10. Mehta, Aaron (16 September 2013). "Rolls-Royce boosts power for V-22 engines". Defense News.
  11. Benbow, Dana Hunsinger. "Rolls-Royce to produce engines for Navy's new hovercraft fleet." Indianapolis Star, 22 October 2012.
  12. Trimble, Stephen (18 January 2017). "Rolls-Royce studies two new stall fixes for V-22 engines". Flightglobal.
  13. "Taking tilt-rotor operations to new heights". Rolls-Royce plc. Retrieved 21 June 2020.

Further reading
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