next up previous
Next: High speed and supersonic Up: Aerodynamics Previous: Induced drag

The whole airplane

In Fig. 4.6 a schematic diagram of the entire airplane in steady level flight is shown. The lift balances the weight of the plane, while the thrust balances the drag.

Figure 4.6: Forces acting upon the entire airplane.

We see that


Modern commercial jets have tex2html_wrap_inline433 ; the precise value depends on the wing design and the specific performance criteria.

What about stability? The resultant aerodynamic force, usually denoted tex2html_wrap_inline435 , engages the plane at the center of pressure . Gravity acts at the center of gravity (or the center of mass) of the plane. The relative positions of these two points determines the stability of the plane. Having the center of pressure ahead of the center of gravity leads to stable flight, while putting the center of gravity ahead produces unstable flight.

Propellers and jets

Please read Section 7.5 of Melissinos. See also Sections 9.1-9.7 in Introduction to Flight by J. D. Anderson, which is on reserve.

Vittorio Celli
Tue Oct 21 21:23:27 EDT 1997