Why do planes fly nose up?

Question

I recently flew on 3 A.A. s80's and when in level flight the nose was up, the stewardess had to walk uphill. Why can't the wings and motors be rotated on the fuselage?

Answer 1

That happens alot with the DC-9 family including the MD-80's... the engines are so far back that the center of gravity is far to the rear of center on the fuselage... therefore they try to fill the foreward cargo compartments first, if they cant fill it, there is a pretty good imballance and the result is a nose-up cruise... Think about it thought, there is alot of "slippage" going on with the engines that far back, even though the engines are mounted at a slight incline, they are pushing the airplane and its sort of slipping in front... with engines on the wings, its pushing AND pulling so you get more ballance... If you get what I'm trying to say... to put it simpler, with the angle of attack necessary, the airplane is obviously not flying on a flat plane through nose and tail... its more through the center of the fuselage with a 5 or so degree angle formed from the intersection...

Answer 2

An airplane has its wing solidly attached to the fuselage at a set angle (the only exception I can think of was the F8U Crusader, which could had actuators to change the set angle in order to allow pilot a better view of the aircraft carrier when landing).
An airplane's ability to fly is dependent on the lift it has, and that is essentially controlled by:
- the speed of the airplane
- the angle of attack of the wing
- the deployment of additional high lift devices, like slats and flaps

Since an airplane must be able to perform in a relatively wide flight enveloppe, the angle of attack required to stay in the air will also change. For a given speed, if the airplane is heavy, it will need to fly at a higher angle of attack than when it is lighter (in cruise, the high lift devices are stowed because the additional lift comes with a heavy drag penality). Therefore, an airplane will have to fly with the fuselage pointing nose up at the beginning, and that angle will progressively reduce as the plane gest lighter using fuel.
Also, if the plane is not flying fast, it has to make up for the reduced speed by increasing the angle of attack.
So, in short, the nose up thing is just a specific condition that is not necessarily indicative of other phases of the flight, or other missions. The angle of the wing is thus some average that is close to the average condition expected during all type of missions, a compromize that is not always perfect but minimizes the performance lost over the whole flight enveloppe.

If you meant "rotating wings and motors" on the fuselage as meaning to have this adjustable, as opposed to have them set at a different angle during design and construction, the problems with having such vital components being mobile is just plain scary. Just the certification issues linked with a possible jam would be enough to ensure no airframer would ever dream of examining this seriously.

Answer 3

Its engines, not motors!

It could be done, but the machinery needed to provide such a facility would cost considerable amount of $s and the weight of the same would mean a few dozen seats might have to be sacrificed. So after extensive debating, the aviation industry decided that it is best the stewardess walk uphill.

What you see in an airplane (structure and shape) is a prime example of ingenuity and practicality. Any design you see is a result of engineering efficiency or metallurgical limitations.

Answer 4

Airplanes do not all fly nose up - it s depends on the designer & usually the true flying attitude is only known after first flight - in general - t this is generally a less desireable / actually a poor design because it adds drag - the DC-10 has a horrible angle of attack & has suffered in the market place because of it. The B52 does not fly with any andle of attack and it even takes off & lands with a flat deck angle .. The 777 has a very flat cruise deck angle to save fuel - and its landing attitude was disconcerning to pilots because it gave the sensation that the airplane was driving into the runway threshold on landing ..

Answer 5

Civilian aircraft are designed with 6 degrees positive angle of attack built into the wing/fuselage mating area for the very reason you site. At design cruise speed, the plane's fuselage is supposed to be level. If it was not, I suggest the pilot was flying slower than design cruise for some reason.

Answer 6

Because a big part of the lift comes from the plane body it self. in fact the wings are already tilted up on most planes, yet this has a limit and the plane body will need to do its part of the work
but for accuracy I didn't realize that when I was traveling. usually the plane is only slightly tilted

Answer 7

Airplane will typically fly with a positive angle of attack. The slower the plane flies the higher the angle of attack required to maintain altitude. So u were either flying slow or it seemed like the nose was up high to from inside (more than it actually was)

Answer 8

Your argument would be better served to ask why the floor of the plane is not designed to be built in relationship to the planes flight.There would still be a slight uphill or downhill depending on the MAC. But still better

Answer 9

The same reason a bird glides with it's wings tilted up. It has to do with lift forces required to fly and counteracting gravity. I'm sure someone will write a much more detailed version.

Answer 10

Sometimes the plane needs to nose up while cruising because it is running at a low speed.