If operating over very high terrain (Afghanistan?) then the baro-time
release unit can be adjusted to give a higher seat separation altitude.

This baro-time release unit is responsible for doing a check of seat
altitude post ejection and, if above the set altitude, it will delay
pilot-seat separation until the set altitude is reached. If ejection occurs
below the set altitude then pilot-seat separation occurs almost instantly.
The pilot still retains the facility to initiate seat separation early by
use of a lever on the seat (MB seats).


"Alan Minyard" wrote in message
...

If, for whatever reason, the crew need to leave the ac at high altitude
then
the crew need to be protected as much as possible from the effects of the
low oxygen/cold environment. The seat supplies supplemental oxygen, but
because the pilot needs to get down to thicker/warmer air as rapidly as
possible, the main chute doesn't open right away. Instead, a smaller
chute
called a drogue deploys to stabilize the seat so it doesn't tumble and to
slow the pilot's horizontal velocity. In a near free-fall, he plummets
(still in his seat) until he hits an altitude of, typically, 15-10k feet
at
which point he separates from his seat and his main parachute
automatically
deploys. If I recall correctly, the time taken to freefall from 55k to
15k
is about 2 mins.



Just hope that you are not flying over an 11,000 ft mountain :-)

Al Minyard