In mid-1970,
Avco Lycoming was advertising two
Lycoming T55-derived engines, an LTC4B-12 turboprop and an ALF 502A turbofan, as possible powerplants for the
U.S. Air Force's
A-X close air support aircraft program.
Northrop Corporation signed a contract with Avco Lycoming to use the ALF 502A for its entry into the A-X competition, the
Northrop YA-9, in January 1971. The engine was given a
United States military aircraft engine designation of YF102-LD-100. Six YF102 engines were built for the YA-9. The thrust engines powered the A-9A prototypes for seven months of
flight tests in 1972, recording 238 flights and 652 flight hours. In 2020, Honeywell sold the type certificate to CFS Aeroproducts Inc. (Arizona), a subsidiary of
MRO provider CFS Aeroproducts Ltd (UK), then transferred in January 2021.
Proposed variants In 1972, Lycoming and
NASA published a study describing the ALF504, a 12.5 bypass ratio engine producing of sea-level thrust at a
specific fuel consumption of and a fan tip diameter of . Lycoming announced its LF500 family of turbofans in September 1988, starting with the LF507-1H and LF507-1F, which were certificated in October 1991 and March 1992, respectively. In June 1992, the company outlined improvements to the LF500 family's core, which included a wide-chord fan to move more air, uprated fan
gearbox, three-stage power
turbine (an increase from two stages), more lighter-weight
composite materials, increased diameter in the first three stages of the
axial compressor to increase airflow by 17 percent, an improved
impeller (centrifugal compressor) with lean-back vanes, a 16-lobe forced
exhaust mixer to reduce noise and specific fuel consumption (SFC), an advanced
combustor, and a temperature margin increase of in the turbine. Lycoming introduced the 500 Series of common core engines of
turboprops and turbofans in February 1994 as a derivative of the LF507 to power regional aircraft in the late 1990s. A turboprop version also was planned for the European
Future Large Aircraft military transport (which would eventually become the
Airbus A400M). AlliedSignal, which took over Lycoming in October 1994, demonstration tested the common core in December; the core was capable of producing of
thrust. After losing the competition to power the
de Havilland Dash 8-400 regional turboprop, AlliedSignal abandoned the common core effort in July 1995. ==Design==