APU ON but engines OFF!

[AF330 0]

Yes, I agree with you.

 

But you need the APU to start. So there is an electric starter which will turn the APU's compressor/turbine.

When It will turn, the APU's compressor will give APU BLEED AIR. When the APU's turbine will turn, the generator will produce elec.

 

Do you agree?

[KriVa 307]

 

 

When It will turn...

When the APU runs, yes, it is indeed possible to use it as a bleed air source. Not when the starter runs. (Just making sure the "it" in your sentence is not confusing anybody.)

[Mariopilot 9]

You got it! APU turns fuel into electricity and bleed air!

- The APU is elecrtically started!

- Main engines are pneumatically started!

 

Jet aircraft without an APU (common, generally smaller bizjets) just have electrically started main engines (made exeption for a few ancient machines like the Canberra that ran the pneumatic starter with an explosive charge...)

[Lorby_SI 2,038]

Hi AF,

 

You turn an engine to start it. After that it just runs. OK? Makes things less confusing to read.

 

Rephrased: You need the small electrical starter (battery power!) to turn the APU. When it runs, its compressor provides bleed air and the APUs own generator produces electrical power. Both are needed to turn and start the main engines. You can do this with ground power too, but as the APU has to be running until after takeoff in case something goes wrong with the generators, it runs anyway. The old airliners didn't have that option, a 707 needs ground power and air.

 

So I agree.

[AF330 0]

Thanks,

 

So I come back to the A380:

 

The APU was ON. So APU's compressor/turbine turning but bleed air to engines (the big ones) not going.

 

So I would like to know when does compressed air go to the engines?

[WarpD 824]

When the pilot chooses to start said engine.

[mebull 27]

AF330 in training? Yeah sure. In training for what? I'm a very patient person, for the most part, but, . . . . . . . . . .as multiple people have said,"here we go again", I get the feeling this person wants Astrophysics explained so as to work backwards to basic math. I have never been closer to a aircraft that had an APU than 50 feet. It is however very easy to figure out what, when, and why they do what they do and how it fits into the scheme of things. "Auxiliary" is kind of self explaining is it not? It is a ground power or battery started turbine used as a back up to provide electricity and compressed air on the ground and in emergency situations. Duh!!!! No I am not an expert but I did fly a simulator once! I do however admire the patience of everyone who keeps answering AF330. Apparently they have not seen the other posts or they wouldn't bother. I want to start my car, whats is this key for? Oh well, is there a face palm icon? Gee, it could not possibly be just to get attention could it? On the other hand, . . . . . . . . . I'm in training to fly a A330 myself, so, could someone kindly tell me what a A330 is and what it does and why?

[cmpbellsjc 2,960]

Here we go again...

Yep, episode #10

 

Isn't this the teen that keeps asking how things do this or that for only Airbus aircraft?

Yes

 

I do however admire the patience of everyone who keeps answering AF330.

As do I. At first I thought this guy was just trolling or doing this on purpose to get people ticked off. Frankly, I'm still not sure if this is the case or his interest is genuine.

[AF330 0]

Just type: " stage en entreprise - 3e".....

----> Stage découverte.

You will be able to find the training we all have to do at this age.

 

I know what an APU is doing. But you are thinking that I am talking about the "big" engine.

 

Ok. WarpD: I am talking about APU's starter. Not the big engine's starter....

 

If you start the APU's starter, you will turn APU's compressor/turbine.

When does the APU's compressed air go to the engines'starter? When you want to start them.

 

You said that APU BLEED AIR valve should be OFF to supply air to the "big engine".

So when the pilots will press on APU (APU MASTER & APU), the starter will start, the electric pump and the isolation valve, the flap inlet will open and the comprssor/turbine will start turning and finally ignation will start.

So if APU BLEED AIR Valve is open, you will get A/C. If the APU GEN is ON, you will get Elec.

So now you want to start "big engines". What do you do now?

[Spam3d 54]

Right, so your APU is now running in what you just described. Giving bleed air to the pneumatic system. The Main engine start valve is closed and the "big engines are stopped" The pilot opens the start valve and the air goes from the apu to the main engine starter spooling the HP system of the big engine for start!

 

Oh and NOT the APU bleed air thats off, just the Air conditioning valves.

[Lorby_SI 2,038]

"What do you do now?"

 

In the Airbus? Easy. Below the throttle quadrant there are 2-4 switches for engine start. Flick up the one you want to start. Yet another computer kicks in, isolates the APU bleed air flow so that it goes to that engine to turn it. At the right moment (maximum turn) the computer switches on the ignition, starts the fuel flow and the engine fires up. In "normal" planes you do all this yourself.

 

The isolation is necessary, because the bleed air from the APU (usually) is not sufficient to operate the packs and turn the engine (or more than one) at the same time. After one engine is running it can add it's own bleed air to the process, so the other engines start more easily.

 

And again the friendly advice: try to be more precise about what you actually want to know. Trying to figure this out reading half sentences with strange phrasing is a little like an uphill struggle.

[JRBarrett 3,070]

So now you want to start "big engines". What do you do now?

Once the APU is running, the bleed air switch needs to be "on". The bleed air will automatically be sent to the air conditioning packs, until it is time to start the main engines.

 

When the pilot turns the engine start switch to "on" a valve will automatically redirect the APU bleed air away from the air conditioning packs, and will instead send the bleed air to the main engine starter.

 

Once all 4 main engines have been started, and are running, the APU can be turned off, since it is no longer needed. The main engines now supply electric power from their own generators, and bleed air for the air conditioning.

[SierraHotel 976]

Search You Tube, Angle Of Attack, APU Preview

[Dave Morgan 68]

At first I thought this guy was just trolling or doing this on purpose to get people ticked off. Frankly, I'm still not sure if this is the case or his interest is genuine.

 

Anyone here remember the lovely Scarlett Jake?

 

To be fair though, I don't think English is AF330's first language.

[n4gix 4,947]

Anyone here remember the lovely Scarlett Jake?

 

To be fair though, I don't think English is AF330's first language.

No it is not. Keep in mind he's in ninth grade, so do the math to figure out his approximate age.

 

I thank everyone for their patience, and would caution a few to keep the above two points in mind before reaching for their 'troll hammers...' ^_^