TAA_Airbus From Australia, joined Nov 1999, 726 posts, RR: 0
Reply 1, posted (13 years 3 months 1 week 3 days 14 hours ago) and read 8031 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.
Planelover From United States of America, joined Dec 2001, 321 posts, RR: 0
Reply 2, posted (13 years 3 months 1 week 3 days 13 hours ago) and read 8015 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.
Bjones From United States of America, joined Feb 2002, 123 posts, RR: 0
Reply 3, posted (13 years 3 months 1 week 3 days 13 hours ago) and read 8007 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.
Rmm From Australia, joined Feb 2001, 525 posts, RR: 1
Reply 4, posted (13 years 3 months 1 week 3 days 12 hours ago) and read 7997 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?"
Prebennorholm From Denmark, joined Mar 2000, 6886 posts, RR: 54
Reply 6, posted (13 years 3 months 1 week 2 days 21 hours ago) and read 7906 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.
Metwrench From United States of America, joined Aug 2001, 750 posts, RR: 2
Reply 8, posted (13 years 3 months 1 week 2 days 13 hours ago) and read 7855 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.