V2500 Engine Spool Up Time
 

Hi everyone,

This is a question for all A320 mechanics working on the V2500 engine.
Is there any documented reference as to the max. time required for the engine to stabilize at IDLE on attempting a start?

Any inputs would be much appreciated...

According AMM Task "Normal Engine Manual Start Procedure" the time between FUEL ON to idle N2 must be less than 90 seconds.
During Automatic Start the EEC is watching this.

A little known fact (amongst pilots) is that the V2500 engine's FADEC will dry motor the engine if the residual EGT before start is above 100 degrees centigrade, and only when the EGT has fallen below 100 degrees will the FADEC introduce fuel to achieve a new start.

This, they say, is to avoid rotor bow, which I guess is a problem with such a long N1 (fan) rotor shaft, and it can add significant extra time to an engine start with warm engines.

Which model of V2500 ???
There is a lot of difference between the A1 and D5..

Don't believe this is the case as I regularly see fuel flow prior to EGT falling below 100C.

It's obviously a target for the manual engine start, and the last time I did one of those the EGT wouldn't drop below 115C despite a solid minute of motoring.

While it is true that V2500 has a delayed ignition/fuel, your information quite incorrect.

The motoring for shaft problems is 30 seconds, irrespective of any other parameters. Additionally, if the EGT after the 30 seconds cranking period remains above 250°C (not 100°C), FADEC will schedule additional motoring until residual EGT drops below limit before introducing ignition and fuel.

Is this only with weight on wheels?

@FlyingStone. Thanks, you are correct. I have just checked the book and I was wrong - it is exactly as you say. Oddly though, in all the many V2500 starts I've experienced, the EGT just dips below 100 degrees before the fuel flow is started. Perhaps I was thinking of the Trents on the A330 - (but I'm not going to look that up right now), or maybe was told it during a tech refresher.

Anyway, my basic point was correct - the V2500 engine will motor for a while before introducing fuel and lighting up, so they take longer to start than a CFM for example.

I was specifically talking about the -A5....

Trents in the 330 won't introduce fuel till 100 degree or below.

Thanks, Snakecharma, that must be where I got that from.:ok:

There are two independent issues at play here - "Bowed Rotor Start" or BRS, and residual EGT.
BRS is exactly what it sounds like - differential cooling of the HP shaft causes it to bow. There is a window of between ~30 minutes and a few (up to six) hours after the previous shutdown where BRS can be a serious issue. Best case it will result in high vibes during start (which has been known to do long-term damage to engine components), worse case it will rub the compressor resulting in permanent performance loss, worst case it's been known to damage compressor blades.:eek: A period of motoring before introducing fuel helps mitigate (but not totally prevent) BRS. Most engines have some level of BRS exposure, although the newer generation 2 spool engines are noticeably worse.
High residual EGT can cause hot starts - basically the residual heat in the engine heats the incoming compressor air and effectively causes the FADEC to over-fuel during start causing a hot start. So autostart is programed to motor the engine until the residual EGT is below some (engine dependent) EGT limit before introducing fuel.
While I don't have any first hand knowledge of the V2500, BRS is not an issue for in-flight starting since the HP rotor won't stop turning (if it does you probably don't want to restart it) so it doesn't bow.
The FAA has mandated something called "Quick Windmill Relight" (QWR)capability for the newer engine installations (for Boeing, it started with the 777). QWR is for a pilot that inadvertently shuts down an engine in flight and, realizing the error, quickly turns fuel back on. The FAA has mandated it needs to start and be capable of significant thrust within (IIRC) 90 seconds, effectively prohibiting residual EGT restrictions for in-flight starting.

You are not able to find it in any documents?
I hope you are not working on aircrafts...

Pilots easy find it in FCOM:
70-80-40 Automatic Starting/Dry Cranking
70-80-40 Automatic Starting Sequence/Second Step

Maintenance easy find it in AMM:
71-00-00-710-043-A - Normal Engine Automatic Start Procedure
71-00-00-710-047-A - Normal Engine Manual Start Procedure

You wrote, that you "experienced this so no doubts" and that implicate that you are working on aircrafts.
If you are working on aircrafts then you have access to the actual documents. That you are "just not able to find it in any documents" shows that you are either a bad pilot/mechanic or a liar.
I do not have a problem when an enthusiast for aircrafts ask for details and normally i am willing to share the infos, but in this case I think you are not honest so I get sarcastic.

Time for everybody to show their cards and post the quotes, sheesh!