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13th of April 1989

On this day in aviation history, the 578-DX made its first flight. 578-DX ?? May be Pratt & Whitney / Alison prop-fan 578-DX engine rings a bell? Still not ringing a bell?

Let's have a look at it:

Pratt & Whitney / Alison prop-fan 578-DX engine

In the mid-'80s of the previous century, Allison Engine Company unveiled the 578-DX engine at the Paris Airshow. It was based on the Allison T701 engine, in use in heavy helicopters. Two variants were envisaged, a 10.000 shp and a 16.000 shp variant. In 1986 further development o the engine was undertaken by the specially formed joint venture between Pratt & Whitney and Allison, PW-Allison. Competing with the GE36 UDF (unducted Fan Engine)

Claims from PW-Allison about the engine in comparison with jet engines were promising; - 30% fuel saving - Quieter (because of lower rpm of the prop-fan)

- Better take-off and landing performance

PW-Allison aimed for certification of the engine in the early '90s.


PW-Allison pitched the engine as the power source for the

- Boeing 7J7 (a proposed B727 replacement)

- MD-91X/MD-92X (Competitor of the Boeing 7J7)

- FIMA (Future International Military/Civil Airlifter - a proposed replacement for the Hercules and the Transall)


Some interesting facts on the 578-D engine:

- 6 bladed propfan (Hamilton Standard) 11.6 ft (3.5 meters) diameter

- Proposed Mmo 0.80-082

- 3 or 4 stage Low Pressure Compressor (depending on thrust varient)

- 13 stage High Pressure Compressor

- 2 stage HPT

- 3 or 4 stage LPT (depending on thrust varient) The engine was only flown for just 20 hours in May 1989. With the cost of the engine ~40% higher than its competitor on the MD90 airframe, the IAE V2500, and the dropping fuel prices there were no orders and the program came to an end.

More info and details here and a promotional video here.


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