Pressurization & O2 Requirements

Question 1

Why do we need pressurized systems for operation at higher altitudes?

Answer 1

• The human lungs would need enough pressure to intake oxygen at higher altitudes
• Lungs wouldn’t be able to expand and contract to bring in O2 and exhale CO2

Question 2

What is the service ceiling of your a/c and what would be the oxygen requirements if operating at the service ceiling?

Answer 2

12,000’

Question 3

What’s the benefits of flying at higher altitudes where pressurization would be required?

Answer 3

• Avoid weather systems
• Faster airspeed/favorable winds

Question 4

What are the oxygen requirements for operating a pressurized cabin aircraft above FL250?

Answer 4

91.211
- At least a 10 minute supply of supplemental O2 in addition to the O2 requirements for non-pressurized a/c

• For each occupant of the a/c for use in the event that a descent is necessitated by the loss of cabin pressurization

Question 5

What are the oxygen requirements for operating an a/c above FL350?

Answer 5

91.211
- In addition to the O2 requirements for operation above FL250:

• Unless one pilot is at the controls of the a/c that pilot must wear an O2 mask that’s sealed and supplies O2 at all times or whenever cabin PA reaches 14,000’ MSL

or

• If below FL410 when there are 2 pilots at the controls and there is a quick donning mask that can be put on with one hand from the ready position in 5 seconds supplying O2 and properly secured and sealed, wearing the O2 mask isn’t required

however:

• If above FL350 and one pilot leaves the controls for any reason, the remaining pilot must put on and use O2 mask until the other pilot has returned to their respective station

Question 6

What are the O2 requirements for operations not in cabin pressurized settings?

Answer 6

91.211

Above 12,500’ MSL
- Required minimum flight crew is provided and must use supplemental O2 for flights longer than 30 minutes

Above 14,000’ MSL
- Required minimum crew is provided with and uses supplemental O2 during the entire flight time

Above 15,000’ MSL
- Each occupant of the a/c is provided with supplemental O2

Question 7

What are the 3 different configurations for O2 systems?

Answer 7

1. Continuous Flow Diluter
2. Diluter Demand
3. Pressure Demand

Question 8

Describe the Continuous Flow Diluter O2 system:

Answer 8

3 Types:

• Typically used for flight below 25,000’ MSL
  1. Constant flow: Continus O2 at constant rate (costly)
  2. Adjusted flow: Offer O2 delivery with varying altitudes and O2 supply pressures
  3. Altitude compensated flow: Uses a barometric control regulator that automatically adjusts the rate of O2 in response to pressures and O2 supply pressures

Question 9

Describe the Diluter Demand O2 system:

Answer 9

• O2 is provided on demand during inhalation to the user
• O2 flow is stopped when the demand ceases (pauses or exhalation
• Conserves O2
• Mask has a special regulator as compared to the “continuous flow” type masks
• Associated with quick donning masks that puts a tighter seal around the nose and mouth

Question 10

Describe the Pressure Demand O2 system:

Answer 10

• Forces positive pressure O2 into lungs and USER must force the air from the lungs in order to exhale
• Special training required to use these masks
• Uses a regulator and quick donning masks

Question 11

What can happen if you use a medical grade or welding type O2 in flight?

Answer 11

• These O2 tanks contain more water which could freeze in the O2 line at higher altitude
• Aviation breathers O2 contain 99.5% O2 and contains no more than 2milliliters of water per liter of O2

Question 12

What is a pressurized aircraft?

Answer 12

• An aircraft that can pressurize the interior of an aircraft to a higher pressure than the outside pressure

Question 13

What is required training to act as PIC in a pressurized aircraft?

Answer 13

Ground Training

and

Flight Training

Question 14

What are some of the ground training knowledge areas to get the pressurized aircraft endorsement?

Answer 14

1. High alt. aerodynamics & meteorology
2. Effects, symptoms, and causes of hypoxia and any other high-altitude sickness
3. Respiration
4. Duration of consciousness w/out supplemental O2
5. Effects of prolonged usage of supplemental O2
6. Causes and effects of gas expansion and gas bubble formation
7. Preventative measures for eliminating gas expansion, gas bubble formation, and high-altitude sickness
8. Physical phenomena and incidents of decompression and
9. Any other physiological effects of high-altitude flight

Question 15

Describe the cabin pressure relief system:

Answer 15

Provides:
- Cabin pressure regulation
- Pressure relief
- Vacuum relief
- Dumping cabin pressure

This is done using the:
- Cabin Pressure Regulator
- Outflow Valve
- Safety Valve

Question 16

What should be inspected with the O2 tanks prior to flight if equipped?

Answer 16

PRICE
Pressure: Ensure enough pressure and O2 are available for the flight
Regulator: Inspect O2 regulator for proper function. if using continuous flow system ensure the outlet assembly and plug-in coupling are compatible
Indicator: Check flow indicators on the regulator or within the O2 delivery tube. Don the mask and check the flow for steady flow
Connections: Ensure all connections are secured
Emergency: Have O2 equip. in a/c ready for use in case of emergency. This step includes briefing pax on location and use of O2

Question 17

What does the outflow valve do in a pressure control system?

Answer 17

• It helps keep a constant pressure in the cabin while bleed air is brought in via the engine driven pneumatic pump
• A gauge monitors the pressure difference between cabin and ambient altitudes, and the pilot can then manage the cabin altitude

Question 18

What is maximum pressure differential?

Answer 18

• This refers to the max pressure differential between the cabin and ambient altitude that the a/c pressurized section can support

Question 19

At what altitudes should you avoid flying above with no pressurized magnetos?

Answer 19

• 14,000’ MSL because it’s susceptible to arcing

Question 20

What are factors that dictate how fast an a/c will decompress?

Answer 20

With all factors equal:
- Size of opening: Larger opening means faster the pressure will leave
- Size of cabin: Smaller cabin, the faster the air will depart
- Pressure differential: Greater pressure diff. means slower decompression
- Pressure ratio: Compressors will continue to work when pressurization is lost. The rate the compressed air comes in dictates how fast pressure is lost
- Altitude: Faster decompression due to less resistance to the air leaving the a/c

Question 21

What’s the most dangerous type of decompression? and why?

Answer 21

Slow Decompression
- Because of the gradual nature of hypoxia and depression of mental focus to recognize emergencies make slow decompressions the most dangerous

Question 22

How does nitrogen affect the human body with ascending in flight?

Answer 22

• We breathe in Nox through our respiratory system, then distributed through the body via the circulatory system
• If pressure changes occur too quickly, Nox bubbles may form

Question 23

How does Nitrogen leave the body when pressure changes quickly?

Answer 23

2 Types of Expanding Gas
- Trapped Gas: Expanding/contracting gas in certain body cavities causing abdominal pain, tooth aches, pain in ear/sinus if a person is unable to equalize the pressure changes
- Evolved Gas: Because Nitrogen comes out in the form of bubbles, it can affect the body tissues differently. Fatty tissues contain more nitrogen gas more than other tissue. This making overweight people more susceptible to evolved gas.

Question 24

How many different ways can O2 be stored on an a/c?

Answer 24

It can be stored as a solid, liquid or gas

Question 25

What are the different types of O2 storage systems used for aircrafts?

Answer 25

• Gaseous aviator’s breathing oxygen (ABO):
• Liquid aviators breathing oxygen (LOX):
• Sodium chlorate candles (solid state oxygen):
• Molecular sieve oxygen generators: