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Saab Draken Flygmotor Turbines  
User currently offlineCO 757 200 From , joined Dec 1969, posts, RR:
Posted (13 years 2 months 3 weeks 5 days 12 hours ago) and read 3336 times:

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?

6 replies: All unread, jump to last
User currently offlineFlight152 From United States of America, joined Nov 2000, 3472 posts, RR: 6
Reply 1, posted (13 years 2 months 3 weeks 5 days 11 hours ago) and read 3262 times:

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

User currently offlineCO 757 200 From , joined Dec 1969, posts, RR:
Reply 2, posted (13 years 2 months 3 weeks 5 days 11 hours ago) and read 3274 times:

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

User currently offlineContact_tower From Norway, joined Sep 2001, 536 posts, RR: 1
Reply 3, posted (13 years 2 months 3 weeks 4 days 20 hours ago) and read 2993 times:

Pratt & Whitney JT8D-22 is correct for the Viggen, only with a reheat chamber attached.

User currently offlineFBU 4EVER! From Norway, joined Jan 2001, 998 posts, RR: 7
Reply 4, posted (13 years 2 months 3 weeks 4 days 19 hours ago) and read 2998 times:

The Viggen engine also differs from the JT-8D in having an additional stage in both the compressor and turbine sections.

"Luck and superstition wins all the time"!
User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 25
Reply 5, posted (13 years 2 months 3 weeks 3 days 13 hours ago) and read 2978 times:

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.
User currently offlineBroke From United States of America, joined Apr 2002, 1322 posts, RR: 3
Reply 6, posted (13 years 2 months 3 weeks 2 days 16 hours ago) and read 2977 times:

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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