-27 question puffs of smoke

[bubba070]

I need some help. The engine is a PT6-27, the problem, white puffs of smoke coming from the exhaust in cruise. It happens every 10 or 15 minutes or so. Its just a quick puff, but I would think it's allot of smoke since you can see in cruise. 
 

[Heliian]

Yikes, sounds odd to me, what kind of Aircraft? Is there any change in RPM, PSI, or ITT when this occurs?

[Go Guns]

We used to get that exact same thing out of a -42 I flew. I don't think they ever found out what caused it. I'll ask some people that may remember and if I get anything I'll let you know.

[Adam17]

You carry out soap checks on that Engine, might be an idea to take and send an oil sample off if so and see if anything is coming to the end of its days internaly!!!!

[bubba070]

It's a turbo beaver. I can't say if there is a change in the PSI, RPM or the ITT. It happens to fast, you see a white puff of smoke then look at the gauges and everything is normal.

I did hear of this happening one other time. They put new nozzles in then on the first flight were getting white puffs of smoke. They put a different pair of nozzles in and it went away. The problem with our aircraft started happening after the hot section was done.

[Troubleshot]

Just a shot in the dark...could be your fuel nozzles are coking up or the spray pattern is bad on more than one nozzle. With out running it is hard to tell....one possiblity could be oil making into the hot section through a shaft seal every now and then.

[Bulawrench]

If it is a Viking STC it incorporates a check valve that allows excess fuel back into the tank. If this check valve is stuck it will hold pressure to the FCU and possible cause trouble. White smoke on shut down could be a seal.

[Heliian]

I would have to agree with the nozzles, check to make sure you have the correct ones installed in the right locations (primary and secondary). Was it a new turbine installed or just a hot section inspection? If the discrepancy showed up after work was done then you should consult with the one who did the work. Good luck and don't forget to check the troubleshoosting guide for more ideas.

[torquey401]

White smoke on shut down = vapourized fuel not burning
White smoke in cruise = ?
Puffing black smoke in cruise = chunks of carbon forming in the combustion liner and breaking off into the airstream and smashing into the guide vanes and compressor turbine blades, looking like puffs of black smoke. Left long enough = CT leading edge erosion. It can take as little as 10 - 20 hours to render CT blades U/S. CT blade replacement = $$$$. The puffs may appear white because they occur so fast.
Check the maintenance manual and/or talk with P&WC ASAP.
Just my internet opinion.

[brownbear]

fuel nozzles is the culprit.

[kilpicki]

Is there any trace of oil in the inlet?

If so the no#1 bearing labrynth seal could be passing oil due to corrosion on the housing resulting in white smoke puffing in flt.

.

[Cranium]

Check your oil consumption rate: if it has gone up since the smoke started, you probably have a lab seal leaking.
Listen for unusual noises during start-up and shut-down (grinding, squealing, etc).
Turn the prop and listen for unusual noises.
Turn the compressor and listen for unusual noises.
Other than that, call Pratt and ask them - they have 24-hour tech support (not sure how good, been lucky enough to not have to call them so far).

[KISS_MY_TCAS]

I agree with the nozzles. Mixing primary and secondary will only effect the start, white puffs in cruise indicate unburned fuel. A HSI was just done, likely 1 or more of the nozzles was damaged in the process. Change them out, i am sure like our ramp department, you have some droolers in there. We switched overhaul shops for a similar problem, send them back for a flow check. It is possible you have a bad lab seal, but they usually provide a DC-3-esque cloud on start and shutdown. Sniff the exhaust stackson shutdown, burning jet a smells distinctly different than burnong oil.