Pintle Geometry

If the correct pintle geometry is not used, it is impossible to have the wheels extended and tracking straight, whilst lying at the correct angle (normally flat, parallel to the bottom surface) in the wing.  This becomes more of a problem if doors are fitted.  The pintle angle may be defined as the angle to the wing cord, in both the plan and side views, that the retract must be pivoted to give the correct geometry.

The pintle angle is calculated as follows:

  1. Measure the rake in the extended position (forward rake positive, rearwards rake negative).
  2. Measure the rake in the retracted position (forward rake negative, rearwards rake positive).
  3. Add these two figures (taking note of the signs, positive or negative)
  4. Divide by 2 (two) which gives the pintle angle

The difference between the pintle angle and rake angles give the angle that the leg has to be offset to the retract mechanism to give the correct geometry.  Other factors can come into play and these can alter the calculated figure by up to two degrees.

The main problem is finding accurate scale drawings to work to.  I have measured from nine sets of Spitfire drawings and even allowing for different marks, every set showed variations.