smoke during start BE20

[navajo]

Hi,

When I start the right engine (PT6A-41), N1 get stuck at 22% during 1 or 2 sec, then I see smoke coming out of the exhaust pipe. What would be the cause? The chief of maintenance said it's fine as long as there is no problem with the ITT during the start. I'm a pilot and I trust our chief of maintenance but I would like a second opinion.

Thanks

[ettw]

So by saying it gets stuck at 22% Ng do you mean a hung start? I would expect a failure of the primary/secondary nozzle flow divider failure. If I remember correctly on the -41 (its been a while) the flow divider is part and parcel of the FCU rather than built into the #7 nozzle as in -27/28 etc.

If by saying it gets stuck at 22% Ng you mean very slow to accelerate onto the secondaries then I might suspect min flow or Idle Ng set too low. Back when I was working in the 200 you (the engineers) could adjust min flow but around 2000 or so P&WC took that procedure out of the maint manual. Haven't looked at a -41 manual for about 7 yrs so maybe the procedure was put back in. Regardless, we found that we had to readjust min flow in the spring and the fall when we saw large changes in OAT from winter to summer.

7-7 fuel nozzle configs also caused some funny starts but usually they were more "agresssive" starts until you changed them out to 10-4.

Cheers,

ETTW

[Ballsssssss]

And if someone tells you something different from your DOM, what are you going to do? Go up to him and say "Hey Man, these anonymous guys on this internet forum say you are wrong" ???? That may not get him to change his mind about what may or may not be wrong with the engine and it will probably hurt your relationship with maintenance. If you are seriously concerned, talk to your CP.

Also, how do you know the people that are going to give you info on here know what they are talking about? There are a lot of inexperienced know-it-alls on here mixed in with some experienced, smart people.

[navajo]

I fully trust our maintenance, they are really profesionnal and I'm not gonna tell them they are wrong because of an internet forum! They are the ones who can tell me if my airplane is safe to fly or not. Thanks anyway to warn me.

I'm just trying to understand, with the "pilot's knowledge" I have of the turbine, why there's smoke coming out of my turbine when I start it....

[bilko]

P&W Customer help desk 1 800 268 8000

or better yet call Bruno Bourdages (P&W) if he cant help you ??? 450/468-7881 email bruno.bourdages@pwc.ca

[scouty-dog]

The flow divider should be all by itself, not part of the FCU.

Smoky -41's are quite normal, and annoying to pilot's and concerned customers. We used to chase smoky starts by changing flow dividers, nozzles, and FCU rigging. $$$

Some people live with it, and some chase the problem. Maybe someone else has a definite solution.

[torquey401]

Smokey shutdown = smokey start.

White smoke at shutdown is caused by the flame being extinguished before having a chance to burn the fuel being pushed through the nozzles and fuel transfer tubes by the purge system. With the flame out, the fuel isn't burned, just vapourized, filling the combustion chamber with fuel vapour. Try moving the condition lever smoothly and slowly to ICO rather than slamming it as many pilots tend to do.

[Youngback]

What colour is the smoke on startup and what is the OAT.

Also, it's somewhat normal depending on the engine for it to sit at certain N1 and ITT ranges briefly during start. They don't follow a linear acceleration and ITT increase. I've never seen a PT-6 sit near 22% for any length of time but around 30% or so, the acceleration really drops off until it gets above 40% There could be any number of variables involved here. Condition of engine, improper rigging of the engine, type of fuel. Without actually seeing the engine start or seeing the trends, it's hard to give you any accurate idea of whats happening.

Back to the first question, if it's really cold weather outside and white smoke, its just vaporizing fuel. If it's black and its hot out, I might reconsider flying the plane.

[ame25]

i had a very similiar problem once ended up being a comp bleed valve

[wrenches and radios]

Don't know about the -41 but in the -34 it would be your start purg valve. No biggy just causes white smoke on start up. It's part of the fcu so no one wants to spend that kind of money on a little white smoke.

[SAR_YQQ]

All of our school BE9L's smoke on start and shutdown when it is -20ish out.