Questions about the structure of an airplane?

Question

What exactly is the thing that changes the pressure called?

What is producing the oxygen?

What exactly is using the fuel? The engine or something else?

Answer 1

THe pressure is created by the compressor section of the engine. THe air is either warmed or cooled, and routed to the cabin. In the rear of the plane there is a device that controls the pressure by allowing a sertain amount of the air to leak out. This device is simply called the Pressurization Control System. Resiprocating engines use a turbo or separate compressot for the pressurized air.

No oxygen is being produced, it is simply outside air being compressed and puped into the cabin.

The Engines use most of the fuel. The Auxilary Power Unit (APU) uses fuel when in use, but this is mstly only while the aircraft is on the ground. Piston, multi engine aircraft have a cabin heater that burns some fuel as well.

Answer 2

The engines produce the increase in air pressure inside the cabin. Hot air is bled off the engine compressor (known naturally enough as bleed air) at one or more points in the air's path through the engine (but before the combustion chamber). The hot compressed air is cooled and the pressure reduced by a series of heat exchangers and what's known as an air cycle machine, before going into a distribution system that controls the air temperature in the cabin. The cabin air pressure is controlled by outflow valves, that regulate the amount of air that's allowed to leave the cabin. There's also a safety valve (or valves) that keep the cabin pressure from exceeding safe limits (safe for the airplane, that is).

On the ground, a small turbine engine known as an auxiliary power unit (or APU) supplies compressed air for the air conditioning system, as well as electrical power for the airplane. Some airplanes have APUs that can be operated in flight.

The oxygen in the cabin air is there naturally; it's not being produced anywhere. The emergency oxygen system is supplied either by a large compressed oxygen tank, usually located in the forward cargo compartment, or by chemcial oxygen generators located in the passenger service units (PSUs), which is the name for the overhead panel that has the lights, the little air conditioning vents, the flight attendant call buttons, the oxygen masks, etc. The chemical oxygen generators contain sodium borate, which has the odd characteristic of producing oxygen gas (rather than consuming oxygen) when it burns.

Yes, it's the engines that are using the fuel. The APU also uses the same jet fuel, from the same tanks.

Answer 3

Jets are different from other airplanes. I will assume you are asking about a jet.

The pressurization system uses bleed air from the air conditioning system to pressurize the airplane. Cabin pressure is controlled by modulating the outflow valves. Modern jets have an automatic mode and a manual back-up mode.

Outside air is mostly nitrogen and 21% oxygen. This air is drawn into the engines. Some of the air is mixed with fuel and burned to create thrust. Most jets then bleed air compressed by two stages of spinning blades in the engine nacelles; a low stage bleed and a high stage bleed. These can be mixed with a valve depending on various factors, and sent to the environmental control unit. The engine bleed air is hot, on the order of 250 degrees Celsius. It is then cooled by letting in ambient air, either ram in-flight or by fan on the ground. It goes through a heat exchanger and cooled to almost freezing and then mixed with more bleed air to achieve a comfortable temperature. The outflow valve closes until the appropriate cabin altitude is attained and then modulates open and close to maintain the desired pressure. The automatic cabin altitude schedule will raise the cabin altitude during climb and usually lower it during descent. At cruise altitude, the cabin altitude might be set to between 4000 and 8000 feet, for example.

The outflow valves receive static pressure signals from static ports for overpressure relief and negative pressure relief functions, actuating pneumatic devices to inhibit airplane structural damage or injury in case of improper system operation.

The aircraft engines and the auxilary power unit (a small turbine engine used to provide air and electrical power on the ground until the engines are running), use Jet fuel from the wing tanks.

Answer 4

1) A compressor changes the cabin pressure, sort of like blowing up a baloon. That is why your ears fill up with air pressure.
2) Oxygen is pulled from the atmosphere by the cabin compressor.
3)The jet engines use the fuel, nothing else.

Answer 5

One addition to these answers, military aircraft carry liquid oxygen for the emergency O2 on board, not sure if commercial do or not.

The liquid oxygen gets heated where it turns back into a gas and then is delivered to the oxygen masks.

Answer 6

Sometimes if the generator quits, the APU (aux power unit) runs on the same fuel as the engine, as it is a small turbine engine.

Answer 7

http://www.howstuffworks.com/question258.htm

The oxygen is generated by a chemical reaction.