High Altitude Operations

Question 1

What is cabin differential pressure?

Answer 1

The difference between the cabin pressure altitude and the ambient air pressure outside the aircraft.

Question 2

What are the authorization requirements for operating a pressurized aircraft (service ceiling or max operating altitude of 25000ft, whichever is lower)?

Answer 2

Must have received and logged ground training from an authorized instructor and have an endorsement in the person’s logbook or training record from an authorized instructor.

Question 3

What are the oxygen requirements above FL250?
a. Above FL350?

Answer 3

Must have a 10 minute supply of supplemental oxygen, in addition to any oxygen required from 12500 feet and above, is available for each occupant in the event that a descent is necessitated by loss of cabin pressurization.

a. “At flight altitudes above flight level 350 unless one pilot at the controls of the airplane is wearing and using an oxygen mask that is secured and sealed and that either supplies oxygen at all times or automatically supplies oxygen whenever the cabin pressure altitude of the airplane exceeds 14,000 feet (MSL), except that the one pilot need not wear and use an oxygen mask while at or below flight level 410 if there are two pilots at the controls and each pilot has a quick-donning type of oxygen mask that can be placed on the face with one hand from the ready position within 5 seconds, supplying oxygen and properly secured and sealed.”

In other words:
- Above FL350, when only 1 pilot is at the controls, he/she must wear an oxygen mask. If 2 pilots are at the controls, they must have quick donning masks within reach.
- If above FL410, both pilots must wear oxygen masks continuously.

Question 4

What are the two types of depressurization?
a. Explain each type.

Answer 4

Rapid and explosive
a. Rapid
- More common in large aircraft
- Depressurization rate that is slower than the lungs can decompress
- Can be caused by a faulty dump valve, faulty pressurization system, or some sort of hole in the cabin
Explosive
- Complete depressurization of the cabin in less than half of a second
- More common on smaller GA aircraft
- At a rate faster than the lungs can decompress
- Can cause lung damage and violent buffeting or being sucked out of the aircraft

Question 5

What are some different types of storage containers of supplemental oxygen?

Answer 5

• Bottles of gaseous aviator’s breathing oxygen (AVO)
• Liquid AVO
• Sodium chlorate candle
• Molecular sieve oxygen generator

Question 6

What are the delivery systems of supplemental oxygen?

Answer 6

• Continuous flow
• Diluter demand
• Pressure demand

Question 7

What are the types of masks for supplemental oxygen?

Answer 7

• Nasal canula
• Oral nasal re-breather
• Quick-don diluter demand
• Airline drop down units (dixie cups)