NavList:

Geoffrey,

In the early 1970s I joined the US Air Force to prevent me being drafted into the Army.  As part of the intro physical the eye Doc said I was red-green color dificent.  After about a year as an enlisted airman a friend at the Flight Medicne clinic said a new color test was being used - a Farnsworth Lantern test.  Shine a light in your face and you say what color.  I passed ( just ) and became a pilot.

For the rest of my flying career I never passed the normal ( poka dot ) test, in fact the FarLan test was only in use for a few years.  No problem with depth preception, only hard to see the " tan patch of ground near the green trees ...."  Luckly for all I flew cargo, not drop bombs.

All the airplanes I flew ( out of training ) had a radar altimiter.  What a great tool - flying into a small island over water you had no idea how high you were without it.  I can relate to what Frank said about estimating distance on a fractal world.

John H.   41N  100W