Topic Author
Posts: 287
Joined: Sat Dec 25, 1999 4:41 pm

Question Re: 737-200 Engines

Tue Jan 04, 2000 7:07 am

This is something that I have been dying to find out for ages now: is the P&W engine that powers the 737-200 a turboFAN or a turboJET?? I have had the opportunity to see the engine close up and while peering into the exhaust duct, I could see all the way to the turbine blades but could not see any bypass duct either within the main exhaust duct or surrounding it outside the nacelle. If this is a bypass engine, which I suspect it is, then where the heck does the bypass air meet the core jet exhaust stream?

Many thanks!!
May the wind be always at your back . . . except during takeoff & landing.

RE: Question Re: 737-200 Engines

Tue Jan 04, 2000 7:16 am

The 737-200 is powered by the JT8D Turbofan. It is just an old (1960s) fan with a ratio of only 3:1 (3 times as much air goes around the outside as thru the core turbojet) - whereas engines such as the PW4000 (747 etc.) have a ratio of about 11:1 (11 times as much air goes around the sides than thru the core) This is why older engines are louder and less efficient.

Hope this helps.

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Joined: Mon Dec 20, 1999 3:16 am

RE: Question Re: 737-200 Engines

Tue Jan 04, 2000 10:19 am

It's a low bypass turbofan,though I believe more air actually goes through the core than does bypass. With the 737-200's very long tailpipe,it is not easy to see the bypass duct,but's it's there.
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Joined: Thu Jul 29, 1999 8:12 am

RE: Question Re: 737-200 Engines

Wed Jan 05, 2000 1:55 am

The JT8D family is a bypass fan engine. As stated in the other posts, it is a low-bypass fan, where very little air is bypassed around the core.

The cold stream duct, where the bypass air flows around the core, is only about 4 - 5 inches wide on this engine. Compare that to the nearly two FEET width on the B777 Trent engine, and you'll understand why they are called HIGH bypass engines ;-)

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Joined: Sun Nov 21, 1999 11:44 pm

JT8D Engines

Wed Jan 05, 2000 2:24 am

Hi Everybody, Buzz here. All good answers. If you get the chance to look up an A320's tailpipe, they meet and mix just forward of the nozzle. Similar idea on the JT8D's.
Don't drop any igniter plugs when you change them, it's REALLY hard to fish out of the fan duct.
By the way...... The basic core was originally a 'disposable' engine for a 1950's cruise missle. Then Grumman, and Douglas wanted a lightweight turbojet engine. So the A4 Skyhawk and the A6 Intruder used them. Later Pratt and Whitney grafted a fan onto it, and got 14,000 lbs of thrust out of it. It took years to become reliable, but it's stood the test. g'day
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Joined: Mon Dec 20, 1999 3:16 am


Wed Jan 05, 2000 2:35 am

Hey Buzz,that igniter comment made me laugh. I still have gook all over a socket and extensions from the cargo pit tape that I use to tape the socket to the extensions and the extensions together. You didn't want to drop anything in there,much less something with your name vibro-peened on it!  

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