jmacias34
Posts: 363
Joined: Tue Sep 05, 2000 10:50 am

Wing Mounted VS. Fuselage Mounted

Fri Oct 19, 2001 9:16 am

What are the pros and cons of having Fuselage or Wing mounted engines???
 
48v
Posts: 57
Joined: Fri Sep 14, 2001 11:04 am

RE: Wing Mounted VS. Fuselage Mounted

Fri Oct 19, 2001 9:31 am

Pros of rear mounted engines:

  • Allows a clean wing with no engines disturbing the airflow.
  • Engines have more protection from ingesting snow or foreign objects on the runway.
  • Keeps noise near the back of the plane.
  • Engines closer together give better handling in an engine-out situation.

Cons of rear mounted engines:

  • Requires more strength (= weight) in rear fuselage to carry the weight of engines - wing mounted engines are already supported by the wing, thus no extra fuselage structure is required.
  • Usually requires a T-tail or cruciform tail, which is less efficient and heavier than a conventional tail.
  • Can have truly nasty low-speed handling characteristics if engines block airflow over the tail.
  • May be more difficult to access engines for maintainence - this varies a lot by plane.
 
AV8N2
Posts: 39
Joined: Mon Feb 26, 2001 10:08 am

RE: Wing Mounted VS. Fuselage Mounted

Fri Oct 19, 2001 10:41 am

48V, pretty good, but a couple of faults, and comments:

1) Actually, rear mounted engines are just as bad, if not worse for FOD ingestion. Anything that the tires run over, or a tire itself, will immediately proceed to one or both of the rear mounted engines. This has caused a number of engine failures on takeoff.

2) Along those same lines as in #1 above, in the case of the DC-9s and MD-80s, any ice on the wings WILL go through an engine. And, yes, ice does form on the fuel tanks at temps as high as 70 degrees F - I have seen it many times! Therefore, as part of every MD or 9 preflight, you must inspect for clear ice on the top of the wings above the fuel tanks with a special stick (unless the a/c has been retrofitted with heating blankets, which many are now).

3) As far as engine out controllability, the MD-80 for instance, has it's engines closer together than say a 737, but the engines on the fuselage are actually mounted aft-down and out. This really makes it a little more squirly than the 737. I would not have thought so, untill I transitioned to the Douglas.


I will agree mostly with your last statement, that maintenance is more difficult. That is the main reason, in my eyes, that Alaska's MD-80 crashed in LA. I believe that the maintenance personnel pencil whipped the book, and didn't lube the jack screw as often as need per the manual, due to the fact that it turns into quite a project with the "T" tail.

I may be FOS, but this is my opinion!
 
Trident
Posts: 477
Joined: Sun Feb 27, 2000 4:49 am

RE: Wing Mounted VS. Fuselage Mounted

Sat Oct 20, 2001 6:23 pm

Another disadvantage of the rear engine configuration is the requirement to make the wing stiffer to counteract the upward bending tendency of a wing in flight. This, of course, makes the wing heavier. The positioning of engines on the wing is partly done to provide a downward load to cancel out the bending moment, thus allowing the wing structure to be lighter. The technique was pioneered by Boeing on the B-47 bomber way back in 1948 and has proved a sound principle. How many "brand new" designs follow the "Rear Engine - T Tail" configuration today.

The most qouted "advantage" of rear engines was that it allowed a quieter cabin for passengers. I have my doubts about that, especially for those sitting in the rear.

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