The Honeywell/ITEC F124 is a low-bypass turbofan engine derived from the civilian Honeywell TFE731. The F125 is an afterburning version of the engine. The engine began development in the late 1970s for the Republic of China (Taiwan) Air Force AIDC F-CK Indigenous Defence Fighter (IDF), and it first ran in 1979. The F124/F125 engine has since been proposed for use on other aircraft, such as the T-45 Goshawk and the SEPECAT Jaguar, and powers the Aero L-159 Alca and the Alenia Aermacchi M-346.
The F124 engine is fundamentally a low bypass, two spool engine (meaning that there are two rotational shafts, a high pressure shaft and a low pressure shaft. The fan/low pressure compressor section is made of three stages with titanium blades. The first stage has 30 un-shrouded blades, and the overall pressure ratio for the three stage fan section is 2.5:1. Some of the air is bypassed (Bypass ratio of 0.472:1), and the rest is fed to the high pressure compressor section.
The high pressure compressor (HPC) of the F124 is a fairly unique design among gas turbine engines; it employs both axial and a centrifugal compressors in a single design. There are four axial stages that lead to a fifth centrifugal stage. All the blades and the impeller are made from titanium.
The compressed air is combusted in an annular combustor and then exhausted to a single stage high pressure turbine (HPT) followed by a single stage low pressure turbine. The HPT is air-cooled. The exhaust is mixed, meaning the bypass air from the fan and the exhaust from the core exit through a common nozzle. In the F125 variant of the engine, the exhaust passes through the afterburner section. The F124 does not have an afterburner.
By 2004 at total of 460 F124 had been built with an estimated unit cost in 2006 of USD$2.5 million.
In 1978, Garrett announced joint research on the TFE1042 afterburner with Swedish company Volvo Flygmotor AB in order to provide an engine for the AIDC F-CK Indigenous Defence Fighter (IDF) being developed for the Republic of China (Taiwan) Air Force (ROCAF). The TFE731 Model 1042 was touted as a low bypass ratio “military derivative of the proven commercial TFE731 engine” and “provides efficient, reliable, cost effective propulsion for the next generation of light strike and advanced trainer aircraft”, with thrust of 4260 lbf (18.9 kN) dry and 6790 lbf (30.2 kN) with afterburner. After initial negotiation, the investment was going to be divided between Garrett, Volvo, AIDC, and Italian company Piaggio. The development would consist of the non-afterburning TFE1042-6 for light attack aircraft/advanced trainer, and TFE1042-7 for the AMX or F-5 upgrade. Garrett would be responsible for the core engine, and Volvo would be responsible for the fan section and the afterburner. The engine first ran for 3 hours at a Volvo test facility in 1979.
AIDC also suggested upgrading TFE1042-7 to 8000 lbf (31 to 36 kN) thrust as twin engine solution, in order to compete with General Electric F404 for applications such as the JAS 39 Gripen. However, the Gripen project decided to continue with a single engine F404 variant, built by Volvo, and Volvo left the project to at that point to focus on the Gripen work. Piaggio asked to participate at a later date due to financial reasons and left the program as well. Thus only Garrett and AIDC invested in the new International Turbine Engine Corporation (ITEC), with the contract signed in 1982.
In 1988, ITEC decided to invest in the 12,000 lb TFE1088-12, which was re-designated as TFE1042-70A (for political reason as well). Preliminary study had shown that IDF could supercruise with the new engine. At the same time, GE decided to enter the market with J101/SF, a smaller version of F404. However after the IDF order was cut in half due to budget concerns, the TFE1088-12 engine upgrade plan ended as well. The F-CK IDF first flew in 1989, and aircraft were delivered through 1999.
In the early 1990s, the United States Navy considered the re-engining their fleet of T-45 Goshawk trainer aircraft with the F124. In 1994, after flight testing a T-45 with the engine, the USN elected not to do that.
The possibility of a F124-powered T-45 arose again in 1996 when McDonnell Douglas offered an F124-engined T-45 to the Royal Australian Air Force as a competitor for their trainer requirement. BAe wanted to offer the F124 as an option on their entry for the RAAF trainer requirement, the BAE Hawk (which the T-45 is based on), but ITEC refused to give BAe permission to offer it. ITEC’s decision turned out to be a mistake, as the RAAF select the Hawk as their trainer. However, after the selection of the aircraft, the RAAF decided to have a separate competition between the F124 and the Rolls-Royce Turbomeca Adour (which was BAe’s selection) to power the new trainers. In 1997 the RAAF elected to used the Adour engine, effectively ending the F124’s chances of being used on Hawk or T-45 aircraft.
In 1994, the F124 engine was selected to power the Czech Aero L-159 Alca light combat aircraft. The combination first flew in 1997.
In 2000, Alenia Aermacchi announced that their new M-346 trainer/light attack aircraft would be powered by the F124 engine, choosing it over its common rival, the Adour. In 2009, the United Arab Emirates announced that their M-346 trainers would be powered by the F124-GA-200.
The F124 engine powered the Boeing X-45A unmanned combat air vehicle demonstrator in the early 2000s.
The afterburning F125 engine is being considered, as of 2009, by the Indian Air Force as a replacement for the Rolls-Royce Turbomeca Adour engines in their SEPECAT Jaguar aircraft. The new engine would be both lighter and more powerful. It was successfully demonstrated in 2007.
Variants:
F124-GA-100
This is the original variant of the engine. It powered the Boeing X-45 demonstrator.
F124-GA-200
Slightly de-rated variant of the F124-GA-100; the maximum thrust is 6250 lbf (27.80 kN) and the engine weighs 28 lb (13 kg) less. This variant utilizes an all new accessory gearbox, as well as other small upgrades. This variant is used in the Aermacchi M-346.
F124-GA-400
Variation of the F124-GA-100, modified for the T-45 Goshawk and the BAE Hawk. The engine was flight tested in the T-45, but the United States Navy decided not to re-engine the aircraft with this engine.
F125-GA-100
Also known as the TFE1042-70. This is the basic afterburning variant of the engine. Used in the AIDC F-CK-1 Ching-kuo.
F125X
Proposed advanced variant of the F125 engine, with a maximum thrust of 12,500 lbf (56 kN).
F125XX
Further advanced variant of the F125 engine, this one producing 16,400 lbf (73 kN) of thrust. If it were built, there would have been a related F124XX non-afterburning variant, producing only 10,800 lbf (48 kN) of thrust.
Applications:
F124
Alenia Aermacchi M-346 Master
Aero L-159 Alca
Boeing X-45
F125
AIDC F-CK-1 Ching-kuo
Specifications:
F124-GA-100
Type: Turbofan
Length: 67 in (170 cm)
Diameter: 36 in (91 cm)
Dry weight: 1178 lb (536 kg)
Compressor: 3 axial fan (low pressure compressor) stages, 4 axial high pressure compressor stages, 1 centrifugal high pressure compressor stage
Turbine: 1 stage high pressure turbine, 1 stage low pressure turbine
Maximum thrust: 6300 lbf (28 kN)
Overall pressure ratio: 19.4:1
Bypass ratio: 0.472:1
Specific fuel consumption: 0.81 lb/lbf-hr (82.6 kg/kN-hr)
Thrust-to-weight ratio: 5.3:1
