Saab Draken Flygmotor Turbines

Tue Sep 03, 2002 12:32 am

It is my understanding that the Volvo Flygmotor turbofans that power the Saab Draken of the Sweedish Air Force are actually modified Pratt and Whitney JT8D-22 turbofans, the same very turbines that power the 727. Obviously,it had to go through major modifications to make it suitable for the fighter mission since what it has to do in a Draken is way different than it's mission and performance in a commercial airliner such as the 727.

Anyone have any knowledge on the specific modifications done to the turbine to make it suitable for fighter ops?
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RE: Saab Draken Flygmotor Turbines

Tue Sep 03, 2002 1:15 am

No, the engines were license built Rolls-Royce Avon 300s. The afterburners are one thing that was added.

Correction: I Meant Saab Viggen Flygmotor Turbines

Tue Sep 03, 2002 1:23 am

Whoops!! , I'm bad.....I meant the Saab Viggen, not the Draken! Your on the ball about the Draken though Flight 152!
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RE: Saab Draken Flygmotor Turbines

Tue Sep 03, 2002 4:45 pm

Pratt & Whitney JT8D-22 is correct for the Viggen, only with a reheat chamber attached.
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RE: Saab Draken Flygmotor Turbines

Tue Sep 03, 2002 5:49 pm

The Viggen engine also differs from the JT-8D in having an additional stage in both the compressor and turbine sections.
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RE: Saab Draken Flygmotor Turbines

Wed Sep 04, 2002 11:15 pm

RM8B vs. JT8D
Additional fan stage giving a total of three, three LP compressor stages rather than six, new HP turbine, reheat, new quadruple fuel nozzles.

Quite an extensive mod.

I thought I was doing good trying to avoid those airport hotels... and look at me now.
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RE: Saab Draken Flygmotor Turbines

Thu Sep 05, 2002 8:11 pm

The JT8D uses titanium alloy blades throughout the compressor in its civil configuration. This is not so in the -22. At Mach 2, the compressor inlet temperature is about 250 degrees F, a typical temperature rise, at maximum engine power, for each stage of compression is about 50 degrees F. Titanium loses its strength quickly above 800 degrees F.
800-250 = 550 (temperature rise in the compressor to reach 800 F) 550/50 = 11 (maximum number of compressor stages needed to reach 800 F)
The low pressure compressor has about 8 stages (counting the fan)
The high pressure compressor has about 6 more.
The high compressor blades would have to be fabricated from steel. You would do the whole stage to give you a safety margin and to give you equal thermal expansion throughout the compressor.

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