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Of the 12 compines that submitted preposels for the AX-project why was the YA-9 and YA-10 choosen over the other 10 designs?
While researching my book I sat down and read MR. (Don) logans A-10 book I'd pick-up a few weeks ago. He make a very interesting statment which I have never hear and one which I would like your insight on. He states the reason Northrop's YA-9 and Fairchild's YA-10 were choosen was because they were the only two designs which had/has turbo-fan engines. Of couse we all know the A-10s TF-34s are high-bypass turbo-fans but were the engines in the YA-9 turbo-fans? If so they had to be (from the looks of the outside) low-bypass engines...anyone know anything about this?

HMFIC

low-bypass fans would make very little sense to me for the A-10s mission....but who knows.

I think a few of the submissions were prop jobs weren't they?

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Of couse we all know the A-10s TF-34s are high-bypass turbo-fans but were the engines in the YA-9 turbo-fans? If so they had to be (from the looks of the outside) low-bypass engines...anyone know anything about this?

HMFIC
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The YA-9 engines were the AVCO/Lycoming (now Honeywell) ALF-502 of about 6000 lbs SLS thrust (way too small). I think they were proposing a production growth version at 7500 lbs. That is what is selling now. They are used in the original Bombardier Challenger 600 bizjet and the BAE-146 airliner. They were high bypass too. I'll look it up but I think the bypass ratio was in the area of 6, like the TF-34.

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<i>I found some stuff. It says the by-pass ratio is only 5. It is interesting the it has a geared fan, and a centrifugal compressor stage, unlike the TF-34. That probably comes from its turboprop evolution.</i>

LYCOMING (ALLIEDSIGNAL) ALF 502: In 1969, Avco Lycoming began a program to develop the "ALF 502", a turbofan to power large business jets and small airliners, based on the company's T55 turboshaft for the Boeing Chinook helicopter.
The initial production series, the "ALF 502L", was certificated in 1980. It is a two-shaft geared front-fan engine, featuring a fan with two LP booster stages; an HP compressor with seven axial stages, followed by a single centrifugal stage; an annular combustion chamber; a two-stage aircooled HP turbine; and a two-stage LP turbine. A thrust reverser can be mounted, and the fan inlet is de-iced by engine bleed air. The initial version had a maximum takeoff thrust of 33.36 kN (3,400 kgp / 7,500 lbf). ALF 502L series engines power the Canadair Challenger 600 twin-engine business jet.

A derated series, the "ALF 502R", was certificated in 1981. It is externally very similar to the ALF 502L, but it has only one LP booster stage instead of two. The initial version had a max thrust of 29.8 kN (3,040 kgp / 6,700 lbf). The ALF 502R series powers the British Aerospace BAe 146 series of small four-jet airliners.

Avco Lycoming was bought out in 1986 by Textron, resulting in "Textron Lycoming". Textron then sold off the Lycoming division to AlliedSignal in 1995, which produced the Lycoming turbine engines under its own name. The Lycoming name lingers on in terms of its presence in the civil aviation piston engine market, where it once all but ruled the world. AlliedSignal merged with Honeywell in 1999, but for the moment the turbofans retain the "AlliedSignal" name.

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ALLIEDSIGNAL ALF 502 SMALL TURBOFAN VARIANTS:
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relative
variant max thrust aircraft notes
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ALF 502L 1.00 Challenger 600 initial variant, 2 boost stages
ALF 502L-2 1.00 Challenger 600
ALF 502L-2A 1.00 Challenger 600
ALF 502L-3 1.04 Challenger 600

ALF 502R-3 0.89 BAe 146 derated variant, 1 boost stage
ALF 502R-3A 0.93 BAe 146
ALF 502R-5 0.93 BAe 146
ALF 502R-5 1.00 BAe 146
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ALLIEDSIGNAL ALF 502L SMALL TURBOFAN SPECIFICATIONS:
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spec metric english
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diameter 105.9 centimeters 3 feet 5.7 inches
length 1.487 meters 4 feet 11 inches
dry weight 589 kilograms 1,298 pounds

max thrust 33.36 kN / 3,400 kgp 7,500 lbf
pressure ratio 13.6
bypass ratio 5.0
TSFC (max thrust) 12.1 mg / N-s 0.428 lb / lb-h
TWR (max thrust) 5.78

fan 1 stage, 2 LP booster stages
HP compressor 7 stage axial + 1 stage centrifugal
combustor annular
HP turbine 2 stage, air cooled
LP turbine 2 stage
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Edited by - a10stress on Mar 30 2004 11:41 AM

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Thanks for the info a10stress, I can always count on you for answers!!
I never heard or knew the YA-9 had turbofans...learned something again today!

HMFIC

ITS A GOOD BOOK ISNT DICE? I KINDA GOT LOST ON THE POLITICAL PARTS BUT IN ALL IT IS REALLY A GOOD REFERANCE BOOK ALONG WITH A-10 STRESS.

PRESS TO TEST

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ITS A GOOD BOOK ISNT DICE? I KINDA GOT LOST ON THE POLITICAL PARTS BUT IN ALL IT IS REALLY A GOOD REFERANCE BOOK ALONG WITH A-10 STRESS.

PRESS TO TEST
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Last night was the first time I read it and not just looked at the picture and you're right, it is a good referance!

In fact he used a lot of info I had for my first chapter so now I have to go back and rewrite chapter I from another angle or using different data. No big deal I desided to start on chapter II "life after Desert Storm" and will go back and redo chapter I when I feel like it.

HMFIC