people with REAL knowledge of aerodynamics only please!?

Question

what determines the maximum airspeed of an aeroplane in straight and level flight?

Is it to do with zero lift drag? i.e. if surface friction drag, form drag and interference drag are kept to a minimum then you'd be able to accompilish a greater airspeed?

Answer 1

Obviously the maximum airspeed is a function of thrust and drag. Consider that a missile is a aerodynamic body with high thrust and low drag. What determines the maximum speed of the missile?

Drag can be dissected into many parts. Optimizing the shape of the body requires that you pick a environ to operate in, but the basic wedge rocket planes were pretty good (X15). If you are only asking about jet aircraft, then the question is efficiency at what speed. Subsonic or supersonic? Part of the drag is due to turbulent structures in the wake of the body. These can change for different velocity regimes, depending on the aircraft's shape.

If you are asking about low speed regimes, minimizing drag can be achieved by making all components of the aircraft as narrow as possible, and ensuring all surfaces remain laminar. In other words, reduce frontal area and reduce turbulence. Of course you still are required to produce lift. Hence the tendency for long thin tapered wings. Low frontal area, low drag.

Most of these criteria can only be exploited as far as the materials technology will allow. The rocket plane will burn up at speed in the lower atmosphere. The longest, thinnest wing will snap. Various other issues. So you could say the real limit of airspeed is materials technology. Hope this helps!

Answer 2

If you consider the airplane as a free body and examine all the forces acting on it you will come up with several opposed forces. If the plane is not accelerating an any direction, these forces will be equal.

thrust of the engine (prop or jet) opposed by drag (from friction of air moving over the plane and turbulence behind the plane)
lift from air moving under the wings opposed by gravity.

If you want the plane to go faster you must either increase thrust or decrease drag. Ever notice how supersonic planes tend to have very large engines, wings with relatively low surface area, and tend to come to a point in the back? It's no accident that they're designed that way.

Answer 3

OK make the plane lighter (if you can) and you will need less lift, less wing and can travel faster.

Answer 4

Lift and thrust.

Answer 5

WOW