Straight and level flight means when an aircraft is flying at a constant speed without changing its attitude. Its lift is equal to the weight of the aircraft. It is flying at a constant altitude. Then I don't know what happens to thrust and drag? Plz explain me


1 Answer 1


I assume here that the velocity is held constant. For this, both thrust and drag must have forces of equal magnitude and opposite direction. In short, they just balance each other out.

  • $\begingroup$ Actually not really - all 4 forces lift, weight, drag, and thrust in a sum balance out. Unfortunately, they are not always orthogonal, as the plane will quite certainly not fly with the axis of thrust 100% in line with the flight path = drag. But this is only a minute difference. $\endgroup$
    – tsg
    Aug 18, 2019 at 4:49
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    $\begingroup$ You got a proper answer. What do you not understand? (Please don't write in text speak.) $\endgroup$
    – Transistor
    Aug 18, 2019 at 8:33
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    $\begingroup$ @Santhosh Welcome to Stack Exchange. I think it's rude to say "please give me proper answers" without explaining what additional information you're looking for. If you don't like this answer, please explain what you don't like about it. $\endgroup$ Aug 18, 2019 at 13:28
  • $\begingroup$ If thrust is greater than drag, the aircraft accelerates. If thrust is less than drag, the aircraft decelerates. If thrust equals drag, then the aircraft remains at constant velocity. As commented by tsg, this ignores the fact that lift and drag are defined relative to the aircraft's path, while thrust is defined relative to the aircraft's orientation (pitch). $\endgroup$
    – rcgldr
    Aug 18, 2019 at 20:30

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