enter image description here

First, the photo depicts a vector diagram during a climb. L means Lift. Lv means the vertical component of lift. Lh means the horizontal component of lift. T means Thrust. D means drag. W means weight. Wh means the horizontal component of weight. Wv means the vertical component of weight. Lh perpendicular to Lv and Wv is perpendicular to Wh.

I have several questions about this.

  1. did I draw correctly?

  2. in a stabilized climb, is T=D+Wh and Lv=W?

  3. if the answer to the above question is "no", then why not. If it is "yes", then in a stabilized climb, L must be greater than when it is in straight-and-level flight(ie greater than W), so that Lv equals to W. Am I right?

  4. what about Lh. What is its role? Does is contribute to drag as well?

  • $\begingroup$ Lv=W in any stabilized situation, and in climb L is greater than when level, since L is now more slanted. Lh has no specific role, It just happens to be horizontal, but is not useful for calculations. It does contribute to drag if you wish, but as drag is measured in motion direction, it must be first broken down into components parallel to L and D. Remember there is a single force in this story (the total aerodynamic force), anything else is a (virtual) break down of this force in particular directions useful for some calculation. $\endgroup$
    – mins
    Aug 11 at 19:46
  • 1
    $\begingroup$ @mins -- re "and in climb L is greater than when level" -- I don't agree. See aviation.stackexchange.com/questions/40921/… . Re "Lv=W in any stabilized situation" -- again I don't agree. Linked answer shows L < W in steady-state climb, so Lv will also be <W. $\endgroup$ Aug 11 at 21:21
  • $\begingroup$ @quietflyer: Nice answer. Yes I see you're right, though it's a strange conclusion. However the aircraft now climbs not only on lift, but also on thrust, and with a very powerful engine it could climb on thrust only like a missile or a rocket. So yes (Hitomhi) please disregard my first comment. $\endgroup$
    – mins
    Aug 11 at 21:40
  • $\begingroup$ @Hitomhi the right angle is next to L, Lv is the hypotenuse. Note sine climb angle ${\theta}$ x T = is the vertical thrust component. $\endgroup$ Aug 15 at 21:50


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