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An airplane with 10 sq meters of wing five meters fuselage and including one person. can it fly with 50 lbs of thrust? And the max weight is 400 lbs

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    $\begingroup$ If you meant something more along the lines of "Is it possible to design a single seater airplane with 10 square meters of wing w/ fuselage 5 meters long that can fly on 50 pounds of thrust", as opposed to "pick some plane w/ these parameters, can it fly on 50 pounds of thrust"-- you might want to edit to clarify-- $\endgroup$ Apr 16 at 22:54
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A key thing you need to provide is the ratio of L/D, which is also equivalent to the ratio of Cl/Cd, where Cl and Cd are the lift and drag coefficients.

Thrust required for level flight = D/L ratio * Weight.

Without knowing more information, including L/D ratio and Weight, the answer to your question can only be "maybe".

If the L/D ratio is 10:1 or better and the total weight is 500 pounds, then the answer is "yes". Increase the weight or decrease the L/D ratio, without changing the other variables to compensate, and the answer becomes "no".

Also, naturally, we have to know the thrust available at the airspeed that we are actually going to fly at, which may, or may not, have been what you were referencing-- (I assumed it was, in the preceding paragraph.)

Edit: since you've now provided the total max weight at 400 pounds, the answer is "yes, as long as the L/D ratio is at least 8:1, and the full 50 pounds of thrust is actually available at the airspeed at which you are flying." An 8:1 L/D ratio is certainly doable. Of course there would be no excess margin to allow for climbing, if the thrust were exactly equal to drag (50 pounds in the case of an 8:1 L/D ratio) and no more. If you can get the L/D up to, say, 15:1, the performance will be a lot better. (I'll leave the actual calculation for achievable climb angle in that case up to you, but all the required information is present here.)

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    $\begingroup$ Realistically it’s not much fun to fly an aircraft that can’t climb at 200ft/min at the very least. If you want to do it once just because you can then go for it. Compare with a paramotor that can fly with (usually) at least 250N thrust, has a weight of around 220-250lb and a wing area of about 25sqm. Aerodynamics are generally awful and airspeed is quite low (20kts). To achieve the smaller wing area you’d want to fly quite a lot faster and so you’d want a lower-drag design, which would be quite easy to achieve - getting rid of the 2km of lines would be a good start. $\endgroup$
    – Frog
    Apr 17 at 1:29
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    $\begingroup$ @Frog: But in the case of a paramotor (or paraglider) the low airspeed is a feature that is very much desired. Aerodynamics aren't really all that important at low speeds. $\endgroup$
    – jamesqf
    Apr 17 at 3:06
  • $\begingroup$ @ymb1 -- um, yes, obviously-- good catch $\endgroup$ Apr 17 at 19:03
  • $\begingroup$ @jamesqf Quite so; with a similar engine I’m examining what characteristics a more conventional fixed-wing aircraft would need $\endgroup$
    – Frog
    Apr 18 at 3:47

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