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factsonly
5th Mar 2008, 10:31
Hello Gentlemen,

This is my first post on this particular forum so I ask for your patience. On the A320 with the V2500 engines and presumably also the CFMs, the grey background on the N2 disappears when the engine has rolled back and stabilised at idle. Having checked and trained on the aircraft for many years, I have always gone and espoused the line that the grey background disappears when FADEC is satisfied that the engine has started properly and (I assume) has gone out of what I would call a 'start mode' into a normal engine monitoring mode. To add to the confusion, the grey background is also there on a manual start and the FCOM makes it clear that start protections are not available. Unfortunately, I cannot find any reference to support this in the FCOM and I don't want to be telling people information that is incorrect so can anyone tell me when the grey background is supposed to disappear and also what it signifies? References would be useful. I am sure this has come up before and I apologise for flogging a dead horse but I would like to be able to put this one to bed.

JSF1
5th Mar 2008, 11:09
You are correct that in a manual start the FADEC does not auto-abort.

However it still passively monitors the engine.

The grey background will disappear once the engine is stabilised with : Ingition off, Start valve crossline, idle parameters normal.

Even in the manual start sequence, the FADEC still controls the above (ignition, start valve).

Ref: FCOM 1.70.20 P3, FCOM 3.04.70 P5

TQ
9th Mar 2008, 21:20
So at which point does the FADEC stop monitoring the engine start ?
Also, what would be the earliest point at which one could start the second engine ?
Never found anything in the book about this.

Dan Winterland
10th Mar 2008, 04:18
1. No idea. My FCOM 1.70.20 p3 (V2500) lists the FADEC functions, but doesn't go into that much detail.

2. FCOM 3.03.08 p2 states eng 1 should be started after the grey background disappears.

barit1
10th Mar 2008, 11:05
From a purely pneumatic standpoint, the second start should be possible as soon as the first starter has cut out. However, that could make for an interesting fire drill. :eek:

Dream Land
10th Mar 2008, 11:09
The quick way is to start both at the same time.:}

TQ
10th Mar 2008, 11:45
I agree that from a pneumatic point of view, you could technically start the second one as long as the valve on the other side is closed.
If you do so, what would happen if the FADEC would detect a start fault on the first engine that was started ? I guess it wouldn't be able to dry crank if required. Would both pneumatic valve be opened at the same time ?

downsouth
11th Mar 2008, 15:29
In my company we start ENG 1 once the start valve of ENG 2 is crossline...

Dan Winterland
12th Mar 2008, 06:55
Guys I fly with who used to fly with Ansett say they started the second when the start valve went crossline. One pilot started one, the other the second so that the first could continue to monitor his start.

Ansett did have some wacky ways of doing thing though. Thinking of FEs on 767s!

DesiPilot
12th Mar 2008, 08:27
I am not too sure about the CFM engines but in our IAE engines FADEC is monitoring till 50% and after that it is passively monitoring the engines. You can find the information in 1.70.80 page 4. Of course it does not explains why FADEC monitors it only till 50% N2 and leaves it on to us human beings after that!!!!

Also it is not written anywhere but a very wise MEA captain once told me to start the second engine only after the first one (#2 in our case) has reached peak EGT and there is a drop in the EGT. This way at least you are sure that you will not need bleed source in case of engine tail pipe fire or hot start.

barit1
12th Mar 2008, 19:57
Also it is not written anywhere but a very wise MEA captain once told me to start the second engine only after the first one (#2 in our case) has reached peak EGT and there is a drop in the EGT. This way at least you are sure that you will not need bleed source in case of engine tail pipe fire or hot start.

Very good idea! :)