dhardesthard
I only flew the B707 and the flap numbers reflected the flap angles, same for DC 9s, MD 80s and L1011s.
Makes sense.
Centaurus
My understanding from a Boeing (Seattle) instructor pilot in 1978 was that in the case of the Boeing 737 series the flap numbering you described were units of flap - not necessarily corresponding degrees of flap.
Fascinating, I never knew that.