1
$\begingroup$

enter image description here

From pic 1, I know the drag line is below the thrust line, but I am puzzled about where the drag line is in pic 2?

Secondly, what creates most of the drag in flight, is it the fuselage or the wings?

$\endgroup$
  • 1
    $\begingroup$ Unfortunate registration of the first plane. $\endgroup$ – Burhan Khalid Jun 11 '18 at 14:26
1
$\begingroup$

It's the wings. Most of the time.

Best L/D is reached when the induced drag is equal to the non-lift-related drag. Induced drag is a byproduct of lift creation, and that is predominantly done by the wings. Therefore, induced drag (physically a backward tilt of the lift vector away from the direction in which lift is defined) is produced by the wing.

For the remaining drag you can do a very rough estimation based on wetted surface and friction drag. Here the wing again produces a substantial fraction which must be added to its induced drag.

For racing aircraft like the Supermarine S.6A (which won the Schneider Cup back in 1931), the fuselage, struts and the floats did produce almost all drag at high speed. This would be a clear exception to the answer given above. However, even with this aircraft, at low speed (during take-off and landing) the wing would most likely create at least half of the drag force.

On the Dornier Seastar (your first example) the thrust line is chosen so high in order to move the propellers and turbine intakes away from possible splashes of water. The resulting pitch moment is trimmed away with proper elevator deflection. In your second example a lot of drag is created by the many bracing wires. At low speed the wing will produce most of the drag while at high speed the drag line will move down when the unfaired pilot (and wheels, engine and tank) and the many wires will create most of the drag.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.