Prior to launch, passengers should be briefed on the use of safety belts, shoulder harnesses, and emergency procedures. If ballast is used, it must be properly secured. Organize the cockpit so items needed in flight are accessible. All other items must be securely stowed. The necessary charts and cross-country aids should be stowed within easy reach of the pilot.
If a parachute of the approved type is to be available for emergencies, Title 14 of the Code of Federal Regulations (14 CFR) part 91 requires that a certificated and appropriately rated parachute rigger repack it within the preceding 180 days if it is made of nylon. The packing date information is usually found on a card contained in a small pocket on the body of the parachute.
14 CFR part 91 also requires that the pilot in command (PIC) use supplemental oxygen for flights more than 30 minutes in duration above 12,500 feet and at all times during a flight above 14,000 feet. If supplemental oxygen is used, the system should be checked for flow, availability, and the PRICE checklist should be used:
- P = Pressure
- R = Regulator
- I = Indicator
- C = Connections
- E = Emergency bail-out bottle
The importance of understanding the need for oxygen equipment in gliders has been heightened in recent years by a considerable increase in the number of high-altitude soaring flights. The exploration of mountain waves has led to numerous flights at altitudes in excess of 30,000 feet with several record flights in excess of 40,000 feet. In some parts of the country, it is frequently possible to soar to a 16,000- to 18,000-foot cloud base in thermals. In almost all parts of the United States such altitudes are attainable in cumulonimbus clouds.
At 18,000 feet, air density is only one-half that at sea level. The purpose of breathing is to supply oxygen to the blood and remove carbon dioxide. In each breath at 18,000 feet, the pilot breathes in only half as much oxygen as at sea level. This is not enough to deliver an adequate supply of oxygen to the blood, and the situation worsens as altitude increases. The automatic reaction is to breathe twice as fast. This hyperventilation, or overbreathing, is almost worse than going up without oxygen in the first place because it results in eliminating too much carbon dioxide from the blood. The immediate effects of hyperventilation are:
- Spots before the eyes
- Dizzy feeling
- Numbing of fingers and toes, followed by possible unconsciousness
The dangers of oxygen deprivation should not be taken lightly. At around 20,000 feet MSL, pilots might have only 10 minutes of “useful consciousness.” By 30,000 feet MSL, the time frame for “useful consciousness” decreases to 1 minute or less. For planned flights above 25,000 feet MSL, an emergency oxygen backup or bailout bottle should be carried.
The U.S. Air Force in cooperation with the Federal Aviation Administration (FAA) provides a 1-day, high-altitude orientation and chamber ride for civilian pilots. The experience is invaluable for any pilot contemplating high-altitude soaring and is even required by many clubs and operations as a prerequisite.
Aviation Oxygen Systems
Aviation oxygen systems are designed for airborne aviation applications. Unlike a medical-type oxygen system, an aviation system is generally much lighter, compact, and calibrated to deliver oxygen based on extensive research in human flight physiology. Prior to purchasing any type of oxygen system, pilots should research the different options and choose an oxygen system that is appropriate for the type of flying that they do because there are many manufacturers and types of system available. Two common types of systems used today are the Continuous-Flow System and the Electronic Pulse Demand Oxygen System (EDS).
The continuous-flow system uses a high-pressure storage tank and a pressure-reducing regulating valve that reduces the pressure in the cylinder to approximately atmospheric pressure at the mask. [Figure 13-9] The oxygen flow is continuous as long as the system is turned on. In some installations, it is possible to adjust the amount of oxygen flow manually for low, intermediate, and high altitudes; automatic regulators adjust the oxygen flow by means of a bellows, which varies the flow according to altitude. When using the continuous-flow oxygen system, the pilot can use either an oxygen mask or a nasal cannula. [Figures 13-10 and 13-11]
Electronic Pulse Demand Oxygen System (EDS)
The EDS is the lightest, smallest, and most capable on-demand oxygen system available that delivers altitude-compensated pulses of oxygen only as you inhale, using as little as 1⁄8, typically 1⁄6 the amount of oxygen at 1⁄4 the weight and volume over conventional constant-flow systems that deliver one liter per minute per 10,000 feet. [Figure 13-12] The EDS has a precision micro-electronic pressure altitude barometer that automatically determines the volume for each oxygen pulse up to pressure altitudes of 32,000 feet and higher altitudes are compensated with pulses of greater volume. The EDS automatically goes to a 100 percent pulse-demand mode at pressure altitudes above 32,000 feet.
The EDS can be set to one of three D (day or delayed) modes and delays, responding with oxygen until it senses pressure altitudes of approximately 5,000 or 10,000 feet, conserving oxygen when it is not needed. It can also be set to N (night or now) mode for night flying where it responds from sea-level and up. Both modes provide the same amount of oxygen, automatically tracking pressure altitude changes. The EDS limits its response to a maximum respiration rate of about 20 breaths per minute, virtually eliminating hyperventilation usually encountered in stressful situations. There are no scales to observe or knobs to turn as you climb or descend. Adjusting (zeroing) for new barometric pressures is not needed because the EDS responds directly to pressure altitude, as do the physiological properties of your body.