Passenger Jet Plane?

Question

How do they start the plane engine...(they crank it up using battery like car?) How do they maintain the electricity for the lighting , a.cond and av equipment on the plane , when the engine shut on the runway/apron tarmac. Do they maintain a generator set on board, where does it placed and where the exhaust gas go?

Answer 1

they turn the key   LOL

they use a jet of compressed air to get the turbine moving then inject fuel and start it up

Answer 2

It depends.  Usually, we start the APU first, which is a small jet engine in the tail that provides air pressure and electricity.  Some engines have electrical motors to start them like a car, and others use air driven starters.  The APU, aux power unit, generally has exhaust at the back of the tail, or perhaps the side of the rear fuselage.  If the APU is not available, they may start a main engine for electricity and air, or use external power and external air.  External power is a cart with a regular car engine in it and it generates electrical power.  An air cart makes air, either for air conditioning or engine starts.

Hope this helps you.

Answer 3

Your answer will change with the type of aircraft you are referring to, different manufactures use different systems and the specifics will vary between aircraft types. Generally transport category aircraft make use of a APU or auxiliary power unit, it is a small jet engine located in the aft section of the aircraft. The APU is used for electrical production and as a pneumatic air source(commonly referred to as bleed air as it is "bled" form the compressor section of the engine). Pneumatic air is used to run the environmental systems and to run the air turbine starters used to start the main engines. The main engines are started by directing high pressure air through the air turbine starter (ATS). The ATS is connected by gears to the shaft of the compressor section (N2) of the main engine, this gets the engine spinning once N2  rotation reaches approximately 20% the pilot introduces fuel to the engine, electricall igniters (Spark Plugs) lite the fuel and the expanding combustion gasses keep the engine spining the prosses then becomes self sustaining and the ATS is disconected. The airconditioning is provided by an air cycle machine or ACM it is also powered by the high pressure bleed air. How the ACM cools the air is a complicated prosses. If you are interested in learning more about jet aircraft systems I would recomend "The Turbine Pilot's Flight Manual" by Gregory N. Brown and Mark Holt it is a great book and explains everything you would want to know about jet airplanes.

Answer 4

Starting engines depends on the aircraft...The hawker I fly uses starter/generators (the Gulfstream is started with charged air). They are used for spinning the engine up prior to ignition...and then after are disengaged and become a generator..this is where your primary electrical source comes from...28 volts to power the respective DC Buses...then from there they go to the inverters...which produce 115 AC to power the AC bus systems....now this is only the basics....

Also depending on the airplane..when you are on the ground...if you have a plane with an APU , its generator (which is the same as the engine driven generators) will power ALL  of the DC and AC systems on the airplane. Planes without an APU can maintain power to the systems by using a GPU..(Ground Power Unit)...In your question about exhaust for the APU...it will either exit out of the rear side of the aft fuselage...or the very rear of the plane...I dont think I left anything out...good luck...hope this helps...

Jonathan S

ATP-LRJET,HS-125

CFI/AGI