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Saturday 30th August 2008
Brainteasers
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Brainteasers Interactive Quiz #29:
Pressurization

As pilots move up to bigger and faster aircraft, there is a natural desire to fly at higher and higher altitudes. At first, breathing supplemental oxygen is satisfactory, but many pilots find that costly and inconvenient (as do their passengers), not to mention that breathing even pure oxygen isn't enough at very high altitudes. It is then that pilots turn to pressurized aircraft. Pressurization enables us to fly at high enough altitudes to maximize fuel efficiency, get above most inclement weather, and take advantage of strong tailwinds, all without having to be tethered to an oxygen mask. Irv Siegel’s latest interactive quiz deals with aspects of pressurization that are important to any pilot who is thinking of stepping up to a pressurized aircraft.

by Irv Siegel

NOTE: Portions of this quiz are based on the pressurization systems used in such aircraft as Beech King Air, Cessna 340/414/421, Cessna Citation, and Lear 25, and may not apply to some transport category aircraft.

1. Federal Aviation Regulations require the use of supplemental oxygen at all
a. indicated altitude
b. absolute altitude
c. true altitude
d. cabin pressure altitude
e. density altitude
times above 14,000'

2. The pressure differential between outside ambient pressure and inside
cabin pressure is measured in pounds per square inch (PSI). At a differential of
7. In pressurized piston-powered aircraft, air used for pressurization is
FL350?


a. cold, and must be heated
b. hot, and must be cooled
c. a comfortable 70 degrees Fahrenheit
d. 7000'
e. 9000'
normally

3. What window shape offers the maximum strength?
a. square
b. triangular
c. round
d. Window strength is independent of window shape.
4. In pressurized turboprop or turbojet aircraft, what is the source of the
a. engine bleed air
air used to pressurize the cabin?


b. ram air
c. static air
d. ambient air
5. In pressurized turboprop or jet aircraft, air used for pressurization is
a. cold, and must be heated
b. hot, and must be cooled
c. a comfortable 70 degrees Fahrenheit
normally

6. In pressurized piston-powered aircraft, what is the source of the air used
a. engine bleed air
as "lower deck air")


b. turbocharger compressor discharge air upstream from the throttle body
c. engine induction system air downstream from the throttle body (also known
d. ram air
e. static air
f. ambient air
to pressurize the cabin?

7. In pressurized piston-powered aircraft, air used for pressurization is
FL350?


a. cold, and must be heated
b. hot, and must be cooled
c. a comfortable 70 degrees Fahrenheit
d. 7000'
e. 9000'
normally

8. Prior to takeoff in a pressurized aircraft with a planned cruising
a. 23,000'
altitude of FL240, the cabin altitude selector knob should be adjusted so that
b. 24,000'
c. 24,500'
d. 25,000'
the aircraft altitude scale on the indicator dial indicates an altitude of

9. Pressurized aircraft are normally equipped with either a visual and/or
a. 8,000'
aural warning device that will activate if the cabin pressure altitude reaches


b. 10,000'
c. 12,000'
d. 14,000'
10. In preparation for landing on a standard day at an airport whose
a. 4500'
b. 5000'
c. 5500'
elevation is 5000' MSL, you should set the cabin altitude selector to

11. What is the purpose of the outflow valve?
a. To limit the differential pressure on the pressure vessel to the maximum
b. To enable the pressurization controller to regulate the cabin altitude to
c. To ensure that the cabin is unpressurized while the airplane is on the
d. A and B only
e. A and B and C
ground.


pressure vessel.


the desired value by allowing excess pressurization air to escape from the
value that it was designed to handle ("max diff").

12. What is the purpose of the safety valve?
a. To protect the pressure vessel from exceeding maximum design pressure
b. To allow depressurization of the cabin whenever the pressurization switch
c. To ensure that the cabin is unpressurized while the airplane is on the
d. A and B only
differential pressure ("max diff") in the event of malfunction of the
e. A and B and C
ground.


is moved to the "off" or "dump" position.


normal outflow valve.

13. After any scuba dive, the recommended waiting time before going to flight
a. No problem -- the cabin altitude will be approximately 6000'.
aircraft with a cabin differential of 5 PSI?


altitudes above 8000' is at least 24 hours to allow the body sufficient time to
b. No problem -- the cabin altitude will be approximately 3000'.
been scuba diving within the past 24 hours to fly at FL200 in a pressurized
c. Not recommended -- the cabin altitude will be approximately 9000'.
d. Not recommended due to the risk of depressurization of the aircraft during
flight.


rid itself of excess nitrogen absorbed during diving. Is it okay for a person who has