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windshearDK

APU bleed valve fault

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Yesterday I had a fault in my APU bleed valve fault, which I had to cancel in order to start my engines... Since I didn't activate it myself, what could I have done to my plane that made my APU bleed valve to break?

 

 

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Yes I do have this feature activated, that's why I am curious if I misused my APU?

 

Usually I keep it on the least possible as per real world ops

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Service based failures are generated using mean time to failure information. Other than a few items such as brakes and nose wheel balance, failures won't occur because you abused the plane. At least this is my understanding.

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Things break. They do so in real life, and they do so in PMDG's 777.

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Since I didn't activate it myself, what could I have done to my plane that made my APU bleed valve to break?

 

As the others have mentioned, service based failures will make things break occasionally.  Since this one's a lot more automatic than the NGX, I don't think you would've caused it through something like advancing throttles past idle with DUAL BLEED illuminated (something that could cause damage on the NGX - the indication is not on the 777 obviously).

 

The correct course of action next time - in order to avoid delaying your flight or unrealistically just clearing the failure - is to tell your push crew to stop the push and pull you back in.  From there "call maintenance" and have them "defer" the APU (not something you'd actually do, obviously).  Finally, hook up the air start unit using FS Actions.  Start one engine.  Push back.  Start the second engine using the cross bleed procedure.  How you do that, though, is beyond me (in the 777 anyway).  Have a look at the manuals to see if it's in there.  Heck, it might even be in the ECLs.

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That's very interesting... I wouldn't think there would be a random fault already, I mean I've only flown a couple of hundred hours or so.

 

I quickly looked under APU in the ECL, but I couldn't find it, I thought about the airstart unit, but I decided to just reset the fault.

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On the real thing no matter what make, faults can occur at any time, doesn't matter how old the aircraft is I've seen brand new aircraft with add's  only a day or so after delivery

I might be wrong on this but I think one of BA's 787 was delivered a day late because of a faulty component.

As for your fault being an apu bleed valve, that's quite common in real life

rgds

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I quickly looked under APU in the ECL

 

Crossbleed would be more of an engine thing - not APU.  While the APU being INOP would force you to use the procedure, it's not an APU thing.

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Start the second engine using the cross bleed procedure.  How you do that, though, is beyond me (in the 777 anyway).  Have a look at the manuals to see if it's in there.  Heck, it might even be in the ECLs.

 

It's in the FCOM under suplimentary procedures.

 

Engine start requires at least 25psi at sea level (subtract 1 psi for every 1,000ft decrease in pressure altitude), so advance the thrust lever on the operating engine to achieve this then start the other engine as normal. IIRC anyways!

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That's very interesting... I wouldn't think there would be a random fault already, I mean I've only flown a couple of hundred hours or so.

 

I quickly looked under APU in the ECL, but I couldn't find it, I thought about the airstart unit, but I decided to just reset the fault.

Like Flamin-Squrirel said.

 

FCOM_v1 Supplimentary Srocedures page S.P.7.2 (about 1/3 down the PDF)

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Thanks next time I will try my best to do that! 

Any ideas on why it failed? Would an APU restart help?

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In the real world you might try it a couple of times depending on the conditions and if the valve has been cold soaked, as they do occasionally stick but in this I'm guessing it would be a failed part

On ETOPS aircraft it may need repaired immediately but short haul depending on the operator it can go for 10 days, much to the dismay of the crews as they can't get their tea and coffee until the engines are running  (brings a tear to the eye lol)

rgds

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Thanks next time I will try my best to do that! 

 

Any ideas on why it failed? Would an APU restart help?

As said before, things fail. It is then the pilots job to press the "Checklist" button. You should have had an EICAS message so the corresponding ECL will open when you press that button. In there it will tell you exactly what to do.

 

There is no such thing as having a failure and just trying again or not checking the ECL!

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Thanks next time I will try my best to do that!

Any ideas on why it failed? Would an APU restart help?

It's under pneumatics iirc.

 

APU restart won't help. As I said earlier, failures are not condition based and won't occur more often if you abuse the plane.

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As said before, things fail. It is then the pilots job to press the "Checklist" button. You should have had an EICAS message so the corresponding ECL will open when you press that button. In there it will tell you exactly what to do.

 

There is no such thing as having a failure and just trying again or not checking the ECL!

 

Yes I know I tried that, but there was no checklist available, as people said here it simply means that there is no air pressure and I can't operate any function to regain the failed bleed valve.

 

I didn't know that things could fail like this, so I thought it was something I had done, but next time I will handle it like RW... But before you blow a vain, just remember this is a computer simulation, I can do what ever I want...

It's under pneumatics iirc.

 

APU restart won't help. As I said earlier, failures are not condition based and won't occur more often if you abuse the plane.

 

So it was a random fault? Ok I get it I thought this failure feature worked in a different way

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It is random in the sence that condition and use isn't taken into account, but I avoided using the word random because that wouldn't be doing justice to what PMDG provided.

 

They aquired information on mean time to failure for all these parts. That is, they worked out how reliable they are and used this as part of the service based failure simulation. So while a failure, be it engine failure or APU bleed valve failure, will occur 'randomly', the mean time to failure of an engine is much longer than the APU bleed valve, so the engine is much less likely to fail even with the randomness.

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.

 

I didn't know that things could fail like this, so I thought it was something I had done, but next time I will handle it like RW... But before you blow a vain, just remember this is a computer simulation, I can do what ever I want...

 

 

Of cource you can do what you want. I have posted many times that in FSX the user should do as he pleases.

 

But my responses will be explaining how it is handled in real life.

 

Oh....and next time you should phrase that a little different. I and others are helping you in our free time!

And just like you can do what you want, I can choose who I help next time and who not!

 

Anyway, a failed APU bleed valve comes with EICAS "BLEED OFF APU" message.

Forgetting to turn the switch on (normally, per default it should be on) results in the same message.

This is simulated by PMDG but I have not checked if it is simulated correctly.

 

For the above EICAS message there is no checklist itmes to do.

So When you press the checklist button is does not open with a non normal checklist.

However you can still find it in the ECL (and QRH) if you look for it.

And it will tell you what the problem is.

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