[page 27 of original]
parachute jumper loses all sense of the time which has elapsed since his
jump, as was shown in all experiments, so that it is impossible for him,
with failing eyesight, to estimate his altitude.
On the other hand it is desirable, on the basis of the reason adduced
under number 3 above, that the opening of the parachute at altitudes
above 7 km. [23,000 ft.] be prevented, since very often the parachute
jumper would pull the rip cord immediately after recovering from his
altitude sickness, which may be too soon and at too high an altitude.
The best conditions for explosive decompression itself and for the
seconds elapsing until the appearance of altitude sickness are provided
if flying is done at a cabin pressure corresponding to 8 km. [26,300
ft.] and with oxygen breathing.
Since it may become necessary to abandon the aircraft for reasons other
than damage to the pressure cabin, the pressure equalization at a
predetermined rate must be made possible by means of a valve.
In case abandonment does not appear necessary in spite of the loss of
cabin pressure the danger of oxygen lack is still less with the
automatic diving control mechanism than in a parachute jump, since the
dive may be made with considerably greater rate of descent.