Considering the lift equation

$$L = C_L \frac{1}{2}\rho v^2 s$$

Given $P$ is 1,000 ft, $\rho$ is 0.002308, and $V$ is the cruise speed of a Piper Archer or 126 knots, we get

$$L = (0.4) (0.002308) (\frac{1}{2}) (126)^2 (160)$$

or 1,172.5 Newtons.

What are the pencil-and-paper formulae for calculating the best-climb and best-glide rates?

  • $\begingroup$ Without a complex aerodynamic model, I'm not sure it can be calculated. Just read the POH for this info? $\endgroup$
    – abelenky
    Commented Sep 25, 2017 at 18:02
  • 3
    $\begingroup$ Are you asking about the airspeed that provides the best climb rate and glide rate, or are you asking for a way to calculate the actual vertical feet per minute, or feet per mile? $\endgroup$
    – Devil07
    Commented Sep 25, 2017 at 19:50
  • $\begingroup$ What's the actual problem you're trying to solve? Are you curious about how the figures in the POH are calculated? Are you a student pilot wanting to know how to get this information from the table in your POH? $\endgroup$
    – Dan Hulme
    Commented Sep 26, 2017 at 12:53
  • $\begingroup$ Does this answer your question? $\endgroup$ Commented Sep 26, 2017 at 18:45

1 Answer 1


Did you ever consider to look at the units in your calculation?

You can't just throw together some numbers and expect a correct result. Start by converting all input to the much more sane SI units and see how it goes from there. If you plug in the units instead of the numbers on the right side of the equation, you can check for correctness by comparing to the intended unit on the left side.

Hint: 1 Newton = 1 kg·m/s².

  • $\begingroup$ So they can be converted all in the same SI units? even the surface area? $\endgroup$ Commented Sep 27, 2017 at 17:42
  • $\begingroup$ @AishveTorah: In the proper SI units, yes. Surface area in m², density in kg/m³ and so on. $\endgroup$ Commented Sep 27, 2017 at 17:59

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