Flight International has for the first time compiled a directory of gas turbine auxiliary power units (APUs) used in commercial airliners, and regional and business aircraft, worldwide. An APU is a dedicated unit which provides electrical and pneumatic power for main engine starting, ground operations and inflight back-up systems. The directory includes APUs that are currently in production or under development, and those that are no longer in production but fitted to aircraft that remain in service in significant numbers. APUs produced in the CIS are listed separately (see entry).


AlliedSignal Engines manufactures auxiliary power units in 20 basic models, with over 40 variants. Its new-generation RE100 and RE220 units were certificated in 1996, and are designed to cover the entire range of regional and corporate requirements.

It was revealed in 1996 that the Rolls-Royce RB.211-powered version of the Tupolev Tu-204, to be marketed by Sirocco Aerospace International, will be offered with an AlliedSignal 331-200[ER] APU.


36 series

The 36 series is fitted to a wide range of narrowbody airliners, regional jets and turboprops. Current production models include the -280[B] for the current-generation Boeing 737-300/400/500 family, -280[D] for the McDonnell Douglas (MDC) MD-80, and the -300 for the Airbus A319/320/321.

AlliedSignal has begun offering an upgraded version of the latter, the -300-4, which incorporates a dual-alloy radial turbine wheel. This will be replaced in 1998 by a new version of the 131 series, designated -9[A] (see separate entry).

The 36-100 is used on the Fokker 50, Bombardier Canadair Challenger, Gulfstream III/IV and British Aerospace 146 aircraft, while the -150 equips the Embraer EMB-145, Fairchild Dornier 328, Dassault Falcon 900 and 2000, Bombardier Canadair Regional Jet, Fokker 100 and some versions of the 146. The -150 has also been selected as standard for the Raytheon Hawker 800XPmid-sized business jet, and will be included on production aircraft from early this year. The -150RJand -150RRhave full-authority digital engine-controls (FADEC), replacing the analogue unit used on earlier -150 models.


85 series

Initial versions of the 85 series were certificated in 1961, and applications have included a wide range of narrowbody airliners, including the Boeing 707, 727 and 737, British Aerospace One-Eleven and MDC DC-8, DC-9 and MD-80. The latest production models include the 85-98DHF for the MD-80, and the 85-129H and -129J/Kfor the current generation 737-300/400/500. Versions of the more-powerful 36 series are also available for these types (see separate entry).



The 131-9 is manufactured in two versions: the -9[D] for the MD-90 and -9[B] for the new-generation 737-600/700/800. A new derivative, the -9[A], is scheduled to replace the 36-300-4 in 1998, on the A319/320/321.

AlliedSignal says that the high-pressure ratio, single-shaft -9[D] offers 30% lower fuel consumption, compared with the similarly sized 85 series. The unit entered revenue service on the MD-90 in April 1995.

The 131-9[B] is the world's first APU to incorporate a starter-generator, which eliminates the traditional DC starter-motor, and the associated clutch and gearbox. The unit is scheduled to have its first flight in February on the 737-700.


331 series

AlliedSignal's 331-500 APU was the first to receive 180min extended-range twin-engine operations (ETOPS)clearance at service-entry, onboard the Boeing 777 in June 1995.

Over 20,000h of testing and 22,000 starts were completed before the start of airline operations with the unit. The -500 has eductor oil cooling, eliminating the need for a dedicated cooling fan.

Earlier versions of the 331 include the -200[ER] for the Boeing 757/767, -250[H] for the Airbus A300 and A310, and -350 for the Airbus A330/340. The latter was developed in partnership with ASA-Raunheim, Auxilec, BGT, Turboméca and ZF.



The 660 is fitted to the Boeing 747-100/200/300, and production ended in 1991 after 904 units had been produced.


700 series

The 700-4E, fitted to the MDC MD-11, remains in production. Earlier versions are installed on the MDC DC-10 (-4B)and the A300B2/B4 (-5).



The new-generation RE100 is basically an 80%-scale version of the 36-150, and was selected late in 1996 by Cessna as an option for its Excel business jet. It is also offered for the Bombardier Learjet 45. AlliedSignal says other potential applications for the RE100 include Raytheon Hawker business jets, and as an upgrade for Dassault Falcon 20s. The company offers to supply the entire APU installation for the RE100.

The 100kW (135hp) unit is claimed to require 10% less volume to install than earlier-generation business jet APUs, and, at 36kg, is around 30% lighter. The RE100 is equipped with a FADEC, and was certificated in 1996. Production deliveries are expected to begin early this year.



The RE220 has been developed for the 100- to 130 passenger regional and long-range business-jet markets. The 260kW unit has already been selected for the Gulfstream Vand Bombardier Global Express, the latter including the entire APU installation. Other potential applications include the Aviation Industries of China-led AirExpress AE100 and Indonesian IPTN2130 regional-jet projects.

Fokker Services' plans to launch a re-engined version of the Fokker F28 include replacing the type's existing 36-4A APU with the more advanced RE220.

The RE220 was developed in partnership with Italy's Alfa Romeo Avio (assisting with combustor development), Germany's BMW Rolls-Royce (compressor section), Japan's Kawasaki Heavy Industries (accessory gearbox) and Singapore Precision Technologies (inlet and turbine plenums). The unit was certificated in 1996, and is fitted with a FADEC.

Source: Flight International