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Aerodynamics & Flight Mechanics Troubleshooting Guide

This page helps you to cure the most common problems that you may encounter when flying your precious model airplanes.

The model airplane depicted below has some problems.


Photo taken during an F3A-X contest in Tübingen, 1983.

  1. inappropriate flight attitude:
    most planes are designed for flight with the wings in a level position. The fuselage is poorly shaped and does not create enough lift to counteract the weight of the model.
    Remedy: use a better fuselage shape and increase the fuselage height.
  2. center of gravity too far aft:
    removing the engine during flight shifts the center of gravity too far aft. This results in reduced longitudinal stability.
    Remedy: move the wing back towards the tail plane until the center of gravity reaches the 25% chord line of the wing.
  3. front end of tuned pipe open:
    The conical end of the tuned pipe should be connected to the exhaust of the engine (where the oily, hot mess comes out).
    Remedy: add a fuel injection and ignition system to use the pipe as a ramjet engine when the piston engine drops off.
  4. asymmetric horizontal tail plane with pointed wing tip:
    cutting away part of the tail does not improve handling capabilities. Pointed wing tips may be a means to reduce induced drag, if there is any.
    Remedy: To compensate for the asymmetric drag, offset the engine to the port side.
  5. reduced aileron area:
    chopping off half of the aileron reduces roll rates. The drag reduction due to a smaller wing surface is quite small.
    Remedy: increase aileron deflection and add a wing warping servo.
  6. flying close to neighbors:
    the trees and houses are dangerously close to the model airplane.
    Remedy: cut the trees and demolish the house.

last modification of this page: 21.08.01

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Copyright 1986-2001 Martin Hepperle
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