[5] In 1972, Lycoming and NASA published a study describing the ALF504, a 12.5 bypass ratio engine producing 8,370 lbf (3,800 kgf; 37.2 kN) of sea-level thrust at a specific fuel consumption of 0.302 lb/(lbf⋅h) (8.6 g/(kN⋅s)) and a fan tip diameter of 48.0 in (1,220 mm).

[6] 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.

[1]: 198  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 248 °F (120 °C) in the turbine.

[7] 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.

[1]: 198, 199, 200  A turboprop version also was planned for the European Future Large Aircraft military transport (which would eventually become the Airbus A400M).

[9] After losing the competition to power the de Havilland Dash 8-400 regional turboprop, AlliedSignal abandoned the common core effort in July 1995.