View Full Version : Fuselage producing lift

2nd Dec 2009, 06:28
Hello everyone,
Sorry if this is the wrong place to ask.
My question is what is the percentage, of the total lift, produced by the fuselage of a typical jet airliner e.g 737, 757. Couldn't find anything on the web :(

2nd Dec 2009, 11:01
The short answer is "as little as possible". Why? Because the "span" of the fuselage is small, so any lift it does produce has a significant penalty in induced drag.

A slightly longer answer is that it depends on the aircraft's angle of attack, which in turn depends on airspeed, flap setting, and manoevring load ("g"). In the cruise, those types fly typically at around 2 or 3 degrees nose-up, so that is the angle of attack of the fuselage, and fuselage lift will be small. In the initial climb, the body angle can reach 20 deg nose-up, and the angle of attack perhaps 10 degrees, but IAS is relatively low.

Figures? Too difficult, not enough data available.

2nd Dec 2009, 11:05
I recall from my days working on this sort of thing that about 10% of the lift was produced from the fuselage in cruise. As Ken says though many factors will alter that.

By George
2nd Dec 2009, 12:18
When they stretched the 747 upper deck the aircraft went faster. Even today the pax 744 cruises at .86 and the Freighter (with the shorter top) .85 ( I am talking LRC at mid-weights above 330).

2nd Dec 2009, 13:38
Right, thanks all for the contribution especially kenparry. IF anyone wants to add more feel free :ok:

2nd Dec 2009, 13:46
By George: Is that due to more lift, by having longer top deck? Wouldn't there be another reason as kenparry said lift from the fuselage is not a good thing as the induced drag created from that body will overcome the effect of the bigger lift force?

2nd Dec 2009, 13:48
Thanks all for the contribution.

2nd Dec 2009, 14:06
Not entirely sure, but I guess the designer optimises the wing incidence angle based on several considerations, one of which should be good fuel economy in cruise, or low drag. So the 2 to 3 deg fuselage AoA of the B737 in cruise probably minimises overall drag by aligning the fuselage to the overall airflow direction; which should be a little downwards due to the action of the wings.

2nd Dec 2009, 17:36
The 747 top deck mod smoothed out some area ruling issues which is one of the reasons it could go faster.

Lift is always carried on the body. A fuselage in longitudinal cross-section has camber so it will create lift at zero angle of incidence. If you think of a spanwise loading distribution graph, the best one as we all know is elliptical for minimum induced drag. If there is no lift on the body it can't be elliptical. It is optimised for the primary cruise design point with (amongst other things) wing-body rigging angle and wing twist distribution.

2nd Dec 2009, 18:45
Look at the shape of the old Shorts 330/360 fuselage from the side. Looks just like a wing section. Whether any, or how much lift it produced I do not know , but I always thought the wings were too small for the aircraft!!

FE Hoppy
2nd Dec 2009, 22:35
Look at the shape of the old Shorts 330/360 fuselage from the side.

You can't make me. That's just cruel!

Pugilistic Animus
2nd Dec 2009, 23:42
YouTube - Extra300 knifeedge (http://www.youtube.com/watch?v=ELMX1tuyzBY) :)

By George
3rd Dec 2009, 02:01
Slav, Sinbad has answered your question better than I could. I havn't thought of 'area rule' before, but it makes sense.

3rd Dec 2009, 08:40
As well as the Shorts 330 / 360 fuselage producing lift so did the Shorts Skyvan SC7.


3rd Dec 2009, 10:35
the airships/dirigibles at a nose up attitude in flight produced dynamic lift.

3rd Dec 2009, 13:22
Note the B-2 has no fuselage, hence no fuselage lift. :ooh:

3rd Dec 2009, 21:52
Shorts 330/360.

I recall being told by Shorts test pilot that 60% of lift came from the wings and 40% from the fuselage, landing gear sponsons and wing struts.

I suppose it's some sort of Bi-Plane.

3rd Dec 2009, 22:41
What about the piaggio avanti. That thing looks like an aerofoil with wings (if that makes sense)