3M Airplane Systems - Environmental Systems Flashcards
- How does the pilot control temperature in the cabin?
Temperature is controlled by mixing outside air (cabin air control) with heated air (cabin heat control) in a manifold near the cabin firewall. This air is then ducted to vents located on the cabin floor.
- How does the aircraft cabin heat work?
Fresh air, heated by an exhaust shroud, is directed to the cabin through a series of ducts.
- What are several types of oxygen systems in use? (FAA-H-8083-25)
Diluter-demand, pressure-demand, and continuous-flow.
- Can any kind of oxygen be used for aviator’s breathing oxygen? (FAA-H-8083-31)
No, oxygen used for medical purposes or welding normally should not be used because it may contain too much water. The excess water could condense and freeze in the oxygen lines when flying at high altitudes. Specifications for “aviator’s breathing oxygen” are 99.5% pure oxygen with not more than two milliliters of water per liter of oxygen.
- How does a continuous-flow oxygen system operate? (FAA-H-8083-25)
Continuous flow oxygen systems are usually provided for passengers. The passenger mask typically has a reservoir bag that collects oxygen from the continuous flow oxygen system during the time when the mask user is exhaling. The oxygen collected in the bag allows a higher inspiratory flow rate during the inhalation cycle, which reduces the amount of air dilution. Ambient air is added to the supplied oxygen during inhalation after the reservoir bag oxygen supply is depleted. The exhaled air is released to the cabin.
- How does a pressure demand oxygen system operate? (FAA-H-8083-25)
Pressure demand oxygen systems are similar to diluter demand oxygen equipment, except that oxygen is supplied to the mask under pressure at cabin altitudes above 34,000 feet. Pressure demand regulators create airtight and oxygen-tight seals, but they also provide a positive pressure application of oxygen to the mask face piece that allows the user’s lungs to be pressurized with oxygen; this makes them safe at altitudes above 40,000 feet. Some systems may have a pressure demand mask with the regulator attached directly to the mask, rather than mounted on the instrument panel or other area within the flight deck.
- What is a “pressurized” aircraft? (FAA-H-8083-25)
In a “pressurized” aircraft, the cabin, flight compartment, and baggage compartments are incorporated into a sealed unit which is capable of containing air under a pressure higher than outside atmospheric pressure. Pressurized air is pumped into this sealed fuselage by cabin superchargers which deliver a relatively constant volume of air at all altitudes up to a designed maximum. Air is released from the fuselage by a device called an outflow valve. Since the superchargers provide a constant inflow of air to the pressurized area, the outflow valve, by regulating the air exit, is the major controlling element in the pressurization system.
- What operational advantages are there in flying pressurized aircraft? (FAA-H-8083-25)
A cabin pressurization system performs several functions:
a. It allows an aircraft to fly higher which can result in better fuel economy, higher speeds, and the capability to avoid bad weather and turbulence.
b. It will typically maintain a cabin pressure altitude of 8,000 feet at the maximum designed cruising altitude of the airplane.
c. It prevents rapid changes of cabin altitude which may be uncomfortable or injurious to passengers and crew.
d. It permits a reasonably fast exchange of air from inside to outside of the cabin. This is necessary to eliminate odors and to remove stale air.
- Describe a typical cabin pressure control system. (FAA-H-8083-25)
The cabin pressure control system provides cabin pressure regulation, pressure relief, vacuum relief, and the means for selecting the desired cabin altitude in the isobaric and differential range. In addition, dumping of the cabin pressure is a function of the pressure control system. A cabin pressure regulator, an outflow valve, and a safety valve are used to accomplish these functions.
- What are the components of a cabin pressure control system? (FAA-H-8083-25)
a. Cabin pressure regulator—Controls cabin pressure to a selected value in the isobaric range and limits cabin pressure to a preset differential value in the differential range.
b. Cabin air pressure safety valve—A combination pressure relief, vacuum relief, and dump valve.
• Pressure relief valve: prevents cabin pressure from exceeding a predetermined differential pressure above ambient pressure.
• Vacuum relief valve: prevents ambient pressure from exceeding cabin pressure by allowing external air to enter the cabin when the ambient pressure exceeds cabin pressure.
• Dump valve: actuated by a cockpit control which will cause the cabin air to be dumped to the atmosphere.
c. Instrumentation—Several instruments used in conjunction with the pressurization controller are:
• Cabin differential pressure gauge—Indicates difference between inside and outside pressure; should be monitored to ensure that the cabin does not exceed maximum allowable differential pressure.
• Cabin altimeter—This is a check on system performance.
Sometimes differential pressure and cabin altimeter combined into one:
• Cabin rate-of-climb—Indicates cabin rate-of-climb or descent.
