T
RAINING
M
ANUAL
–
L
ANCAIR
IV/IVP
Consider the pilots of King Air N777AJ who experienced a cracked laminate in
the pilot’s (left) windshield on February 2, 2007. The pilot’s turned off the cabin
pressurization at FL 270 and then donned the O2 masks only to find there was
no O2 flow. Both crewmembers passed out. The aircraft was not on the autopilot.
The pilot regained consciousness at a lower altitude. The aircraft was
overstressed during the event and lost most of its horizontal tail. Fortunately for
the crew they were able to land safely at Cape Girardeau Regional Airport.
TABLE 1-1. TIMES OF USEFUL CONSCIOUSNESS AT VARIOUS ALTITUDES
Standard Ascent Rate
After Rapid Decompression
Altitude (Feet) Time
Time
18,000
20 to 30 minutes 10 to 15 minutes
22,000
10 minutes
5 minutes
25,000
3 to 5 minutes
1.5 to 3.5 minutes
28,000
2.5 to 3 minutes 1.25 to 1.5 minutes
30,000
1 to 2 minutes
30 to 60 seconds
35,000
30 to 60 seconds 15 to 30 seconds
40,000
15 to 20 seconds 7 to 10 seconds
43,000
9 to 12 seconds
5 seconds
50,000
9 to 12 seconds
5 seconds
Smoking, fatigue and depressants (alcohol and other depressant drugs) reduce
the oxygen diffusion rate to the blood so higher partial pressures (lower altitudes)
are necessary for any given saturation level. A fatigued smoker with small
residuals of alcohol from the previous evening could require a 50 percent
increase in partial pressures to attain a given level of saturation. In the worst
case, this individual could be mildly hypoxic at sea level and completely
dysfunctional at 10,000 feet.
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23
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©
Copyright
2007
LOBO
May
not
be
copied
without
permission.
