Why is it that when an airplane accelerates, it doesn't go upwards as well as forwards?

Question

If I understand correctly, an airplane stays up in the air because the air is flowing faster over the top of the wing than under the bottom. Since P is inversely proportional to velocity, the pressure on top of the wing is less than on the bottom, and this provides lift. Fair enough. What I want to know is, if velocity increases, why shouldn't lift increase as well?

Answer 1

Offset by rudder and ailerons.

Answer 2

Put real simple, if a given fixed-wing aircraft is accelerated and nothing else is changed, it will climb. At faster speeds the pilot trims the aircraft more nose down to keep the flight level. Someone else here will probably explain it a lot better but there is my $0.02 worth.

Answer 3

Simply put, you decrease the angle of attack (lower the nose) to offset the increase in lift gained by more airspeed.  Conversely, if you decrease airspeed, you will need to increase the angle of attack (raise the nose) to maintain altitude, unless you decrease airspeed to the point where you cannot maintain altitude.

Answer 4

There is not enough momentum or speed.  

Answer 5

Actually it is not excess lift that makes a plane go up. It is excess thrust. therefore, when you let go of the yoke then put full throttle on, considering the attitude is nuetral before you throttle up, the plane will pitch up quite a bit. So actually a plane does go up with more power.

Answer 6

Lift does indeed increase with speed.  However, unless and until the lifting force exceeds the weight of the aircraft, it won't go upwards.

This is the reason for take-off.  During take-off, the aircraft accelerates until the lift from the wings is sufficient to support its weight, at which point it leaves the ground.  Lift is generated even at 1 mph, but it's not enough to support the aircraft's weight.

Small and light aircraft can often take off very quickly (I think the record is about 30 feet), as they don't require much lift to support their modest weights, but airliners usually have to maintain a speed of at least 120 mph or so to stay aloft.

It's not a pressure difference that provides lift, by the way, it's the tendency of the wing to divert air downwards.  The force required to produce a downwash behind the wings engenders an equal and opposite force that is lift.

Answer 7

flaps change direction if the flap is in one spot you stay in that level... push the flap up and you go up push the flap down and you go down.

Answer 8

Well I'm not an expert but my cousin's a pilot, the acceleration basically just makes them go forward but to get the plane up, as well as forward, the pilot needs to pull a leaver, lifting the plane into the air.

Answer 9

I'm not sure.  I looked it up and found this website called Why War?

Answer 10

You are correct good sir. As airspeed over a wing increases the lift increases as well. For wings and all other airfoils there are a few more factors involved. Most notable is the angle-of-attack. An increased angle-of-attack produces more lift at the same airspeed by providing a greater pressure difference (Delta). There is also a slight deflection of buffered air against the underside of the wing surface that increases lift. With this increased lift there also increased drag as well. As a pilot, when I climb I set a pitch nose-up that will increase my angle-of-attack and maintain a constant airspeed. When leveling off at cruse altitude, the nose is pitched down and AOA is decreased. Airspeed naturally increases due to reduced drag. The AOA will be further reduced until lift is equal to weight for level flight. We use pitch trim tabs to achieve this and reduce the pilot's workload of pitch adjustment. NASA has on excelent web site on this topic under aircraft forces:

http://www.grc.nasa.gov/WWW/K-12/airplan...

Any other question feel free to ask.

Cheers,

Ray

Answer 11

The air flows faster under the wing than over the top due to the airfoil first of all.  Thus creating low pressure on top of the wing creating lift.  The weight of the plane must be offset by the velocity of the craft.  The more it weighs the faster the plane must move in order to create the lift needed to raise it into the sky.  Once enough velocity is created to lift the weight of the plane up, the pressure on top of the wing doesnt change.  If I remember correctly.  Hope that helps    

Answer 12

Lift is created by a combination of the speed of the wing traveling through the air, the angle of attack (angle of the wing relative to the direction the wing is moving through the air), the density of the air, and the shape and surface area of the wing.

The only things that a pilot has control over during flight are the speed of the wing (by varying the speed of the aircraft), the angle of attack, and (to a limited degree by the use of flaps) the surface area of the wing. The shape and size of the wing are fixed (on the vast majority of aircraft), and the air density is whatever it happens to be that day.

Both speed and angle of attack are directly proportional to lift. If you increase either speed or angle of attack, you will also increase lift and the aircraft will rise. However, if you increase speed and decrease angle of attack, the amount of lift will remain the same. The same is true if you decrease speed and increase angle of attack.

So to answer your question, if the only change made is an increase in speed, then the aircraft will begin to rise. However, if a proportional decrease is made to the angle of attack at the same time, then the aircraft's altitude will remain the same.

Answer 13

Yep, it does. But what I really wanted to say is, it's spelled "yoke" not "yolk." Yolk is in an egg.

Answer 14

Combine Vincent G and agcatav8r's answers and you have a complete and correct answer.

Answer 15

It does. However, to remain at the same altitude while going faster, the pilot will adjust the angle of attack, so that the lift coefficient will be reduced just enough to compensate for the increased dynamic pressure, and the overall lift remains equal to the aircraft weight.

It is the product of the lift coefficient (which essentially depends on the angle of attack) times the dynamic pressure (times the wing area, but that value is not changing in cruise) that has to remain constant.

Answer 16

Because of the direction of the flaps?