PT-6A Holding the prop on start up?
 

I have often read that it is possible to hold the propeller of a PT-6A during start up. Has anyone actually witnessed this????

I understand why it is theoretically possible, however can it actually be done for more than a couple of seconds after air starts flowing over the power turbine?

Wouldn't it cause enormous damage to the power turbine if you were trying to prevent it turning by holding the propeller when fuel is introduced?

Is this just an OWT??

Can be done, after all other types eg ATR's and Saabs, have prop brakes as options which not only will hold a prop but stop it with the engine running.

The obvious danger aside, whether or not its possible with your own hand is debatable. Saabs will break a prop strap on start if still attached and I doubt anyone would be strong enough. If it started to move, there'd be no stopping it.

May be better asked in the Tech Log forum?

Some free turbines have a prop brake so that the engine may run without the propellor turning. This efffectively give an APU without the additional expense and weight. The ATR 72 is an example of this, having a prop brake on the right engine enabling power and air to be supplied without the danger of a spinning propellor.

Thanks for the input, but with respect, a Saab Donk is hardly a PT6A which is a tiny turbine. I have seen PT6A-20, 27 and 34's all held during start and at idle. They were bear hugged buy a normal size man, seen done many times, hundred of times actually, the management only wanted to hear the engineers who told them what they wanted to hear, although, the better engineers in my opinion, were disgusted with the practice and all insisted it would cost them massively in the long run. I quit that gong show and so did my other friends, so I don t really know if it lead to PT issues later, sorry.

How funny would it be if the bear huggers started rotating with the props :eek: ...be a helluva ride though!!

Ejector

With respect, the OP didn't mention which PT-6A. The -67F is more than a match for a Saab 340A at about 1700SHP, I believe. I dont doubt what you say about the smaller ones, you definitively answer the OP's question, but you won't catch me trying to hold on to one that size.

Yeah, OK, I will leave the Saab comment out of it. No offense intended.

On the smaller ones I have seen, when the person let go, they were in feather still and they had plenty of time to let go with out issue.

I really do wonder what damage was being done with hot spots and particularly on light up, my gut feeling is a lot of damage was being done but I am no expert of course.

Also, a dash 20, 27 or 34 on start up, if the prop tie was on, it would rip it off. Although I never saw it happen, I have seen several planes where the metal clip dented the fuse skin. I am guessing, but may be bear hugging the end of the prop gives you enough leverage?

WHY? :hmm:

In strong winds if the prop is spinning the other way, nothing wrong with someone holding it steady with one hand till its ready to turn itself.

Better you than me fella :eek:

used quite regularly in the arctic to avoid blowing the prop seals, by getting low pressure warm oil to the gearbox/prophub. I used to sit under the PC6 when the Boss would do starts and hold it with one hand, always good for fireworks:)

I very much doubt that any damage was being done. If damage was possible, then P&WC would have advised against the practice.

Yes, holding the prop until the oil has warmed (and become sufficiently viscous) means that the gearbox won't be damaged by what would otherwise be inadequate lubrication.

Not the same engine of course, but it was common practice to hold the
UH-1H rotor blade for as long as possible on start (up to about 20-30%-ish N1I think) to avoid the blade sailing too much at low rpm, and no harm was ever done by doing it as far as I know.

Wokka pilots, respect.
How they managed pullin' all them levers and switches AND holdin' on to the rotorary blades I'll never know...:hmm:
No wonder they was feared guardin' the BBQ area at Vungers. :ooh:

In strong wind with the prop spinning the other way you should have turned the aircraft into the wind to reduce the chance of a hot start.
Basic stuff for PT-6A endos.:cool:

It was a much-overused prank in my PT6 days. Somebody would hide under the starboard engine where the pilot couldn't see him (co-pilot usually still closing the door or heaving bags around) and hang on to the prop-tip while the guy was starting, the idea being to flummox him when he heard the bangers going and the turbine spooling, but saw no prop-movement. Obviously it would be a short time only until the prop would overpower the hand and would go from 0 to serious revolutions in seconds, whilst the hand would go scurrying backwards to safety, banging his head on the flaps on the way for his trouble. :)

Arm, holding the blade might have been OK for those little two-stroke helos you used to fly, but you wouldn't want to do it with a Chook...

Steady on there, DF, dodging the other blade as it came round like an intermeshing egg-beater would have been too hard for me anyway!

Tinnie, it was a bit tricky to try and do it yourself - loady normally took the role - but I know of a few people who have tried to eliminate the middleman by starting with the blade still tied to the tail boom, that always causes something of a kerfuffle. :) (not me by the way).

Yeh, cos the wind never swings over night...

Besides, PT6 drivers have no concept of hot starts, come to Garret land and see the real thing.

One fella I knew had a go at starting a Nomad with the engine bungs in.
"Right, sodding #2 wont start lets try the other one..."