A320 Autocrank
 

Scenario:Engine 2 start with external pneumatic power due to APU bleed fail.During start ground engineer disconects the air supply before than expected and then we have a start fault,hung start.being an automatic start fadec takes charge of it and we get the message on ECAM autocrank in progress.My question is,how on earth is it going to crank it if there is zero bleed press?

No bleed to run the starter obviously.

So Engine master switch off. ( unless the Engine can stabilize at idle )

By this point there should be more than enough N2 ( or N3 for RR ) rotor RPM to clear the Engine sufficiently after you cut off the fuel.

Tell the engineer to put the air back in anyway.

Then when below 30% N2 ( or N3 for RR ) crank the engine if it's required to clear it. ( basically as per the tail pipe fire checklist ) but I don't think you'd need to, just monitor the EGT decrease....


4/ if all else fails run...:ok:

Well that's what I'd do anyway.....

It's something you should think about anyway as it could happen to you starting using the APU anytime....

That engine would definitely be stabilised.

True it would if above 30% N1 ( my bad )

I was simply trying to give the max N2 ( N3 for RR ) for a running engagement of the starter motor.
But you are correct. :ok:

Hi Chiquitete,
The Fadec is simply signalling the start valve to open and ECAM is stupidly reporting "Autocrank in progress" despite the fact that nothing is happening since there is no bleed air pressure to do the work.

Hi ACMS
The starter motor doesn't physically turn the LP section.
You seem to be getting mixed up between N1 and N2.

GoldenrivettAgreed. Where did ACMS learn his fan engine fundamentals? :ugh:

Oops gentleman, my bad :p. Where's the shame icon?

Yes I should have said N3......( RR Trent )

I feel suitably chastised...:ok:

N3 on a Trent, but not on a A320.

Now we see how surgeons amputate the wrong foot. :ugh:

Apart from the silly part of saying N1 my post was still correct.

Engine Master off
Establish Air connection again
Use the Tail Pipe fire checklist to dry motor the Engine. ( as FADEC wants to do )
Otherwise if you cannot establish ground air quickly you will have enough rotation to clear the Engine or partly clear it.

Either way you will obviously need the Air before the next start attempt.

Monitor the EGT closely to ensure it decreases.

Suffice to say that apart from the silly mistake of quoting max starter re-engagement in N1 value the advice to the question was correct.

ACMS I would love to see this RR Trent powered A320 you keep talking about. :rolleyes:

Another smartass.

Seems the site is full of them.:mad:

ACMS,


"Otherwise if you cannot establish ground air quickly you will have enough rotation to clear the Engine or partly clear it."


Errm, I beg to differ. No ground air and your engine is spooling down and definitely not enough air to clear a tailpipe. I was always taught to spin the engine (no matter what make or model) at max motoring for no less than 1 minute and get EGT below 100C before even thinking of reintroducing fuel. This procedure has NEVER failed me for the next start attempt in over 35yrs in the game. Also, a partly cleared tailpipe could lead to a surprise for the unsuspecting on the next engine start.


McHale.

Oh yes agreed.

Definitely need to clear the Engine of any un-burnt fuel during the next start, possibly consider a manual start to run at max motoring before introducing the fuel?

On the 330, 744 and 777 you always need EGT below 100 c before introducing the fuel anyway. ( well my experience on RR and GE anyway ) this should suffice as the EGT would be quite warm after the first failed attempt and it would motor for a while anyway during the auto start.