Hot Start Question on PT-6

[The Sizzler]

Yet another PT-6 Question from me since the POH is no help.



Lets say you recognize the hot start and immediately move the condition lever to "off" then would you have to complete a dry motor run or would the motor continue to run in the auto start sequence thereby cooling the ITT down for you?



BTW I know the auto start sequence on this aircraft (P46T) stops at 65%Ng so I guess I’m wondering if Ng ever goes over 65% on a hot start? Thanks again.

 

[enigma]

I don't know the answer, but I'd like to add a related comment.

A start is not "hot" unless it actually goes over the temp limit. Up until then, it's an impending hot start, or an abnormal start. If you train yourself to avoid the term, hot start, you will save yourself grief with the mechanics and the CP because a true hot start requires special inspections, etc before you can fly the airplane. If it was only impending, then they can return it to service with much less paperwork. Obviously, a true hot start must be properly dealt with, just be careful to not cause unnecessary work.

regards,
enigma

 

[T-Gates]

Yet another PT-6 Question from me since the POH is no help.



Lets say you recognize the hot start and immediately move the condition lever to "off" then would you have to complete a dry motor run or would the motor continue to run in the auto start sequence thereby cooling the ITT down for you?



BTW I know the auto start sequence on this aircraft (P46T) stops at 65%Ng so I guess I’m wondering if Ng ever goes over 65% on a hot start? Thanks again.

Unless Ng reaches the 65% you specified, the starter will continue to motor indefinately. You must manually stop the start.

 

[Kingairrick]

What is an "auto start sequence" And what is a P46T?

 

[mattpilot]

I'd like to add a question.

Helicopter turbines can be "cooked". Can the same happen to airplane turbines?

 

[DAS at 10/250]

A P46T is either a factory Piper Malibu Meridian or a Meridian converted with a PT-6 to become a JetProp. Either way they are a piece of crap.

 

[KeroseneSnorter]

Unless Ng reaches the 65% you specified, the starter will continue to motor indefinately. You must manually stop the start.

Depends on the installation. Some of the PT-6 Variants also have a time limit. I have flown a couple that had a 2 min limit before starter shut down in addition to the NG % trigger. (2 min from beginning of start cycle)

Generally the older certified stuff (King air etc..) does not have this but many of the newer planes (PC-12 etc..) does as part of the auto start sequence.

So it is really a crap shoot as to the procedure for each plane. I have flown ones that required that you hold the start button or switch to motor the engine after an aborted start, and others that you simply monitor the time to make sure the sequence does not shut down early, or run too long.

 

[The Sizzler]

A P46T is either a factory Piper Malibu Meridian or a Meridian converted with a PT-6 to become a JetProp. Either way they are a piece of crap.

Piece of Crap? As if. Maybe the jet prop conversion Mirage but the Meridian is a decent airplane. Sure the useful load sucks but its good for a single pilot operation who is also working their way up to a PC-12. Id take it over an old piston any day.

 

[mmmdonut]

Piece of Crap? As if. Maybe the jet prop conversion Mirage but the Meridian is a decent airplane. Sure the useful load sucks but its good for a single pilot operation who is also working their way up to a PC-12. Id take it over an old piston any day.

I vote for piece of crap.

 

[KeroseneSnorter]

What is an "auto start sequence" And what is a P46T?

Auto Start= One button starting. Push button, monitor the engine, dump fuel in at appropriate time and thats it. Starter cutout and ignition function is automatically taken care of as well as power distribution. Basically all switches stay in the "normal" position during the start. Generators automatically kick on at the appropriate time, etc etc.....

A far cry from the old JT-8-D ay Rick!

On the other hand, once a JT-8-D was running it was hard to kill it! If you had a Fuel control problem that meant some piece of metal broke, nowadays it probably means that a computer chip lost its mind!!

 

[Daveman]

I vote for piece of crap.

Well we all know you're votin' for Kerry, but you can't vote till Nov.2. Dimwit!!!

 

[Airpiraterob]

back to the topic...

and just something to add and be cautious about.

dont forget. if its an "impending" hot start..(close but didnt go into the red)...your temp needle is running quickly TO the redline.....thats the gauge attached to the thermocouple measuring the heat.....i will GUARANTEE YOU its much hotter than what its telling you...its getting hotter faster than that guage is telling you..it has to catch up to the actual heat. it migth be a digital instrument but its still an analog measurement device attached to it. so if you aborted the start close to but not in the red, it probably saw the temp inside somewhere....

just be very careful that you catch it as early as possible. noone wants fire and brimstone.

 

[The Sizzler]

Thanks for the relevant replies, makes sense now.

 

[T-Gates]

Depends on the installation. Some of the PT-6 Variants also have a time limit. I have flown a couple that had a 2 min limit before starter shut down in addition to the NG % trigger. (2 min from beginning of start cycle)

Generally the older certified stuff (King air etc..) does not have this but many of the newer planes (PC-12 etc..) does as part of the auto start sequence.

So it is really a crap shoot as to the procedure for each plane. I have flown ones that required that you hold the start button or switch to motor the engine after an aborted start, and others that you simply monitor the time to make sure the sequence does not shut down early, or run too long.

Well you can tell where my experience has been lately....