High Altitude

Objective:

Understand all the factors relating to high altitude operations for general aviation.

Attention:

Have you ever seen the movies where there is a hole blown into a pressurized airplane and everything gets sucked out? How much of that is actually true?

Motivation:

Understanding the things that can happen to the body at high altitude will help you make better decisions concerning the flight as well as recognizing symptoms than can be corrected if noticed early enough.

Overview:

The effects of high altitude, oxygen regulation requirements, oxygen systems, decompression emergencies.

Development:

Oxygen requirements: 91.211

12,500-14,000 feet MSL

Crew required to use O2 +30 min.

Above 14,000 MSL

Crew must use O2

Above 15,000 feet MSL

Passengers must be provided O2
  • Physiological hazards with high altitude
  • See Middle ear and sinus problems above
  • See Hypoxia above
  • Pressurized aircraft
    • Cabin pressurized for comfort, performance, and safety
    • Pressurization Control
    • You can buy or rent Oxygen systems for aircraft or flights
    • See Jepp Instr/Comm 11-33

Types of supplemental Oxygen systems

Jepp Instr/Comm 11-22

Continuous flow

  • Continuous delivery of Oxygen
  • Decreased duration of Oxygen supply
  • Diluter demand, Pressure demand
    • Supplied only when you inhale
    • Increased duration of Oxygen supply
    • Regulations permit flight at higher altitude with this system

Adjustable flow

  • Allows oxygen level to be adjusted for different altitudes
  • Altitude-compensated system uses barometric control regulator that automatically adjusts the rate of flow
  • Aviator’s breathing oxygen
    • 99.5% pure oxygen
    • Not more than .005 milligrams of water per liter
  • Have systems serviced by a reputable distributor
    • Care and storage
    • Stored in high-pressure oxygen cylinders
    • Made of steel or aluminum, or composite material (reduced weight)
    • Painted green
    • Request “Aviator’s breathing oxygen”

Decompression and corresponding solutions

  • Slow decompression is hazardous because it can often happen undetected
  • Rapid decompression happens in 1-10 seconds
  • Explosive decompression can happen under 1 second
  • Hypoxia, euphoria, hypothermia, decompression sickness
  • Cabin can fill with fog due to immediate condensation of water vapor in the cabin
  • Time of useful consciousness ranges from seconds to mere minutes
  • Emergency descent to breathable altitude, retard throttles, high rpm, props to high rpm to create drag to slow the aircraft
  • Land at nearest usable airport
  • Seek medical attention for decompression sickness

Conclusion and Evaluation:

Remember the extra risks of high altitudes, and take extra precautions as well as complying with regulations.