Simviation Forum

Nov 12^th, 2010 at 12:59pm

alrot Offline
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according to a friend explanation is

Quote:

When it comes to APU, the way it works is quite simple.
It's an engine, so you have to start it, and when it's finally running (needs some seconds), you can use the APU generator to make it produce electricity.
So the behavior is not so complex. Switch ON, wait 5 to 10 seconds, switch APU gen ON, you get power

is it a electrical engine ,or Piston engine ?
I found a photo on internet
http://aviationglossary.com/wp-content/uploads/Auxiliary-power-unit-APU-Airbus.j...

Quote:

A self-contained generator in an aircraft producing power for ground operation and for starting the engines

this engine looks electrical to me ,so is an electrical engine to generate electricity?¿ Shocked

to make work the engine starter of the jet engine ?¿?
and engine that works for engine that works for engine?

the thing is I need to know a little bit more there are only this variables in flightSim ,I wish I could make a gauge a light "Avail" turns on when it supposed to be on ..like in the pmdg-747

these are the variables

Edited:

APU PCT RPM Auxiliary power unit rpm, as a percentage Percent over 100 N -
APU PCT STARTER Auxiliary power unit starter, as a percentage Percent over 100 N -
APU VOLTS Auxiliary power unit voltage Volts N -
APU GENERATOR SWITCH True if APU generator switch on Bool N -
APU GENERATOR ACTIVE True if APU generator active Bool N -
APU ON FIRE DETECTED True if APU on fire Bool N -

any help I would apresiate it

Venezuela

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Reply #1 - Nov 12^th, 2010 at 1:13pm

ApplePie Offline
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alrot wrote on Nov 12^th, 2010 at 12:59pm:

according to a friend explanation is

Quote:

When it comes to APU, the way it works is quite simple.
It's an engine, so you have to start it, and when it's finally running (needs some seconds), you can use the APU generator to make it produce electricity.
So the behavior is not so complex. Switch ON, wait 5 to 10 seconds, switch APU gen ON, you get power

is it a electrical engine ,or Piston engine ?
I found a photo on internet
http://aviationglossary.com/wp-content/uploads/Auxiliary-power-unit-APU-Airbus.j...

Alex, I believe it's a turbine. Not an electrical motor or piston engine.

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Reply #2 - Nov 12^th, 2010 at 2:06pm

SeanTK Ex Member

Yep, turbine engine that requires fuel flow. Wink

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Reply #3 - Nov 12^th, 2010 at 2:14pm

OVERLORD_CHRIS Offline
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It's a small Electric start jet motor, with a generator on it that produces electricity and bleed air for the packs, so you can have AC and Heat on the ground, and start the motors with out any external hook ups.

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Reply #4 - Nov 12^th, 2010 at 2:48pm

expat Offline
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Not sure what aircraft you are doing Alex, but an APU on average takes up to 1 & 1/2 minutes before you can get electrical power and air out of it from the moment you hit the starter switch. It is a small gas turbine engine that is started by a small electric starter motor. On average they use around 200 lbs of fuel an hour. It can supply electricity, 115 volts 400 Hz. Air is bled of to supply the aircon packs and (if required depending on the aircraft) bleed air for the engine starting.

Matt

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Reply #5 - Nov 13^th, 2010 at 11:00am

westside Offline
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I believe on larger commercial aircraft it produces hydraulic power as well. Not sure if it does that with an electrically powered hydraulic powerpack. That is how the pilots of the US air flight were able to control the A320 that landed on the Hudson river.

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Reply #6 - Nov 13^th, 2010 at 11:06am

DaveSims Offline
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westside wrote on Nov 13^th, 2010 at 11:00am:

I believe on larger commercial aircraft it produces hydraulic power as well. Not sure if it does that with an electrically powered hydraulic powerpack. That is how the pilots of the US air flight were able to control the A320 that landed on the Hudson river.

I am curious where you found that information, because that is not what I have heard. From what I have read, the engines on the US Airways flight actually never shut down, they just remained at an idle setting because the computers detected the damage and reduced thrust to prevent further damage. I also heard the crew deployed the RAT (ram air turbine) for emergency power. But I did not believe they had sufficient time to start the APU before getting wet.

Dave

www.flymcw.com

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Reply #7 - Nov 13^th, 2010 at 11:45am

alrot Offline
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So Its a electricity generator instead the one we knows that uses gasoline the one we use when we go camping this one has a turbine engine Shocked

I'm fascinated by these APU I saw some in videos like this

http://www.youtube.com/watch?v=qa97Oh5R0Rk

http://www.youtube.com/watch?v=QRYj3VQqxNU

What does make the main engines start ,I mean a normal starter like the one we use in our cars? "Electrical"

Venezuela

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Reply #8 - Nov 13^th, 2010 at 1:28pm

DaveSims Offline
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Clear Lake, Iowa

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alrot wrote on Nov 13^th, 2010 at 11:45am:

What does make the main engines start ,I mean a normal starter like the one we use in our cars? "Electrical"

Typically the bleed air from the APU is used to get the engine spinning. The APU is started electrically, then bleed air is used for the main engines. The reason is the APU is small enough that an electrical starter will work. It would be impractical to use an electric starter on a large turbine due to the required power and speed to get the turbine spinning fast enough for ignition.

Dave

www.flymcw.com

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Reply #9 - Nov 13^th, 2010 at 3:26pm

OVERLORD_CHRIS Offline
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westside wrote on Nov 13^th, 2010 at 11:00am:

I believe on larger commercial aircraft it produces hydraulic power as well. Not sure if it does that with an electrically powered hydraulic powerpack. That is how the pilots of the US air flight were able to control the A320 that landed on the Hudson river.

-On C-17A the APU's Generator power the Electric Hydraulic pumps, and burns 500lbs an hour.
-On C-5A/B/C The APU's (2x) power the Air Turbine motors that provide Hydraulic power, with there own Eletric Generators. Burn about 500lbs an hour.(not sure about the M they have new APU's)
-747-2/3 Does the same as the C-5
-747-400 do the same but burn about 800lbs an hour
-C-130A-through-H, has GTC that powers the Air turbine Motors for Hydraulic power and Eletrical
-C-130J has Normal APU.

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Reply #10 - Nov 16^th, 2010 at 3:48am

patchz Offline
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http://en.wikipedia.org/wiki/Auxiliary_power_unit

When my Dad was at Pine Belt with Southern and later Republic, the Hobart APU was piston. He used to put his lunch on the engine to warm it. Roll Eyes

If God intended aircraft engines to have horizontally opposed engines, Pratt and Whitney would have made them that way.

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Reply #11 - Nov 20^th, 2010 at 5:34am

Meck Offline
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patchz wrote on Nov 16^th, 2010 at 3:48am:

When my Dad was at Pine Belt with Southern and later Republic, the Hobart APU was piston. He used to put his lunch on the engine to warm it.

Add an AB to the APU nowadays and you can have BBQ for lunch instead of a tepid sandwich! Grin

excuse bad grammar; "I' bin Bayer..." - German Airforce Private First Class (war reserve)

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Reply #12 - Dec 29^th, 2010 at 11:21am

Ivan Offline
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Modern APUs are jet engines...
Usually they are custom built and only run the generator, but some can be used as a real jet engine (RU-19's from the An-24 are used in the super rare Yak-30 trainer)

Basically... its a jet engine that can be started with electricity without draining the battery amps. After you get the APU started, you have more amps (and pressurized air) to start the main engines

Russian planes: IL-76 (all standard length ones), Tu-154 and Il-62, Tu-134 and An-24RV&&&&AI flightplans and repaints can be found here

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Reply #13 - Dec 30^th, 2010 at 2:09am

patchz Offline
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Meck wrote on Nov 20^th, 2010 at 5:34am:

patchz wrote on Nov 16^th, 2010 at 3:48am:

When my Dad was at Pine Belt with Southern and later Republic, the Hobart APU was piston. He used to put his lunch on the engine to warm it.

Add an AB to the APU nowadays and you can have BBQ for lunch instead of a tepid sandwich! Grin

How do you like your steak?
Charred.
I've got just the thing for you. Roll Eyes

If God intended aircraft engines to have horizontally opposed engines, Pratt and Whitney would have made them that way.

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