How to design a near vertical take off airplane, conceptually?

Say I have an airplane, similar to a Zenith 701. Say that it has a stall speed of 50 mph and a wing area of 60 sq ft, and it weighs 500lbs.

Now I want to make it land at 20 mph with full power and my tail volume is sufficient to keep the nose up at 30 deg. I also have slats and flaps to ensure my wing stalls above 30 deg AOA.

Say my max HP is 100. I understand, as a general rule for GA aircraft, thrust is 4x100hp=400lbs. Vertical thrust would be 400 lbs x sin 30 deg x 65% prop efficiency for a prop in climb, giving me a vertical thrust component of 400 x .6 x 65% = 160lbs vertical thrust.

Now, I only need to produce 500-160=340 lbs of lift from my wings. So I increase my wing size so that I can fly at 20mph with a lift of 340 lbs.

Is this correct, at least conceptually?


1 Answer 1


Yes that is conceptually correct. You might have to mount a huge area, since lift is proportional to $V^2$.

Issues to resolve that I can see:

  • The craft would be relying upon aerodynamic forces to maintain attitude, which will be very ineffective at 20 mph. A secondary pressure relief valve system for attitude control would be advisable.
  • Landing at 30 degree nose up will be not easy from ground view perspective, and for landing gear design.
  • Ground effect will change the attitude of the craft if not carefully designed.
  • A wing that does not stall until 30° will be a tall order, and landing at the brink of stall is not advisable, you'll need some margin.
  • 1
    $\begingroup$ And if you do get to the stall AOA on a slatted wing, the stall can be quite violent, basically a LE stall across the entire wing all at once. I know a guy who was able to coax a stall from a Pegazair with the slats out, by accelerating it with hard inputs, and it flipped so violently his flight bag came out of the baggage area and ended up on his glareshield. $\endgroup$
    – John K
    Aug 4, 2019 at 4:14
  • $\begingroup$ What is a "secondary pressure relief valve system for attitude control"??? $\endgroup$
    – Fred
    Aug 4, 2019 at 11:42
  • $\begingroup$ FYI: The zeniths don't stall until past 30 deg. I've heard some of the highlander bush pilots do high alpha landings: drag the tail on the ground first, then slam the wheels down , up to 1,000ft/min with their 36" suspension......!! $\endgroup$
    – Fred
    Aug 4, 2019 at 11:47
  • $\begingroup$ Also, the lazairs stall at 18mph. I guess you could just copy their control volumes to get the right sized controls. $\endgroup$
    – Fred
    Aug 4, 2019 at 12:16
  • $\begingroup$ A separate pressure relief valve system: a couple of pipes running to front & back & wingtips, if required a valve opens and lets go of controlling airflow. Like in the Harrier. $\endgroup$
    – Koyovis
    Aug 4, 2019 at 12:21

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