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Shape Of Engine Nacelle  
User currently offlineDavid B. From United States of America, joined Jun 2001, 3148 posts, RR: 5
Posted (13 years 11 months 3 days 13 hours ago) and read 9039 times:

Why is the nacelle on this engine shaped like an oval? The one on the lower right hand side.

Something do do with aerodynamics or is the camera?

Teenage-know-it-alls should be shot on sight
8 replies: All unread, jump to last
User currently offlineTAA_Airbus From Australia, joined Nov 1999, 726 posts, RR: 0
Reply 1, posted (13 years 11 months 3 days 13 hours ago) and read 9025 times:

Well thats a 737 engine, and all post 200 series have that shape of engine.
I think its just simply due to the low sitting of the 737, and thus the wing to ground clearance is so small that they need to have the engine nacelle flatter at the bottom to keep clearance from the bottom of the engine to the ground.

Sure, they could of wacked the CFM 56 in a round engine nacelle, but then I doubt it would fit under the wing. So, Im pretty sure thats all it is.

User currently offlinePlanelover From United States of America, joined Dec 2001, 321 posts, RR: 0
Reply 2, posted (13 years 11 months 3 days 12 hours ago) and read 9009 times:

Nothing wrong with the picture. That's the shape of the engine on the 737-300 to 500 aircrafts. The 737NG have a more rounded engine nacelles, but is still a little "flattened out" on the bottom.
Have fun.  Smile/happy/getting dizzy

User currently offlineBjones From United States of America, joined Feb 2002, 123 posts, RR: 0
Reply 3, posted (13 years 11 months 3 days 12 hours ago) and read 9001 times:

I was told that the flat bottom on those nacelles was due to the placing of the accessory gear box on the side of the engine instead of the bottom. Was this to give more clearance? All NG 737's have round nacelles. The KC-135R also has round nacelles with the same CFM-56 engine. It was a mechanic on the KC-135 that told me that the placement of the gear box was the reason for the flat bottom on the 737 and that it was on the bottom on the KC-135 and that was why it had the round nacelle.

User currently offlineRmm From Australia, joined Feb 2001, 527 posts, RR: 1
Reply 4, posted (13 years 11 months 3 days 11 hours ago) and read 8991 times:

The oval shape you speak of is where the accessory gearbox sits. The CFM56 flatened inlet is purely for ground clearance, although I once had a pilot ask me on a preflight, "how are the blades made shorter at the bottom?"


User currently offlineZionstrat From United States of America, joined Apr 2001, 226 posts, RR: 0
Reply 5, posted (13 years 11 months 3 days 1 hour ago) and read 8919 times:

Rmm, I hope you are joking!

User currently offlinePrebennorholm From Denmark, joined Mar 2000, 7141 posts, RR: 53
Reply 6, posted (13 years 11 months 2 days 20 hours ago) and read 8900 times:

Dear Bjones, the CFM56's on the 737 classic and KC-135R are not anywhere near the same engines. The CFM56-2 on the KC-135R has a 68 inch diameter fan and would never fit on a 737. The CFM56-3 on the 737 classic is only 60 inches.

The different versions of the CFM56, the -2, -3, -5 and -7, have four different fan diameters. Only the -2 and the -5A and 5B have identical fan diameters at 68 inches. The -3 is 60, the -5C is 72 and the -7 is 61 inches.

And there is a load of sub-variants with quite substantial differences including varying number of compressor and turbine stages. The largest CFM56, the -5C4, is almost twice as powerful as the smallest CFM56.

CFM56 is rather an engine family than an engine type. Have a look at http://www.cfm56.com

Always keep your number of landings equal to your number of take-offs
User currently offlineBjones From United States of America, joined Feb 2002, 123 posts, RR: 0
Reply 7, posted (13 years 11 months 2 days 16 hours ago) and read 8859 times:


Thanks for the info. I knew the engines were somewhat different as they had different rated thrusts. But did not realize that they were that different in fan size.


User currently offlineMetwrench From United States of America, joined Aug 2001, 750 posts, RR: 2
Reply 8, posted (13 years 11 months 2 days 12 hours ago) and read 8849 times:

Bjones is mostly correct. I've never worked on Boeings, but went to GE's Line MX Training for the GE CT-7 in Cincinnati. Training for every engine that GE builds is there. Our Instructor explained to us that when Boeing selected that engine there was concern for ground clearance. So GE redesigned the accessory gear case to "flatten' out the bottom.

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