PC-12 Shutdown in Flight

[ackeight]

You're right about the EP, & I am surprised that "fuel pumps on" is not part of the procedure. I am sure that it is assumed that the fuel pumps are in auto, but I'm scratching my head over why the EP wouldn't say to turn them on.

But back to your original idea of doing a non-starter assisted airstart, when you say above that you would have to do "200kts to have auto ignite", at what Ng are you proposing to do an unassisted airstart? 200 kts to reach 10% Ng? How much more to reach 13% Ng to introduce fuel?

You would need a pretty fast airspeed to get it above 10%. 200 might be exessive, I was just throwing a number out there. You will not hot start it introducting fuel between 8%-10% with 150kts of ram air cooling it down. I beleive that is why they don't have a non-bat airstart, but who knows:dunno:. I would do a battery start if I was in VMC and an airport I could glide to as stated before just to make sure I had good NG for relight.

 

[wjmiller3]

I would just pull the chute..... Oh wait, wrong plane!!

 

[Stonefly]

You would need a pretty fast airspeed to get it above 10%. 200 might be exessive, I was just throwing a number out there. You will not hot start it introducting fuel between 8%-10% with 150kts of ram air cooling it down. I beleive that is why they don't have a non-bat airstart, but who knows:dunno:. I would do a battery start if I was in VMC and an airport I could glide to as stated before just to make sure I had good NG for relight.

With a two batt installation (speaking of the legacy models), you shouldn't lose the AP, EFIS, & AHRS anyway. In a single batt installation, yes. All the new ones have two batts, of course.

That being said, I am setting myself up for a forced landing, first & foremost. That is a bigger priority for me than relighting the engine (unless I'm doing an Atlantic crossing, for example & there is no chance of gliding to land, there are exceptions to almost any rule). I will get set up for an approach, precision preferably. Then, and only then, would I start the process of attempting an airstart. As I previously mentioned, from the flight levels you have 20 to 30 minutes of glide time, so there is some time to try a few things. If the engine relights, bully for me, & I will continue the approach anyway. If the engine does not relight, no big deal, I've already anticipated & prepared for that situation!

 

[minitour]

Just out of curiosity, how long will you hold pressurization in the FLs with the motor popped? Do you have a minimum glide icing speed?

-mini

 

[Stonefly]

Just out of curiosity, how long will you hold pressurization in the FLs with the motor popped? Do you have a minimum glide icing speed?

-mini

I don't know exactly how long the aircraft will hold pressurization. The engine failure in flight checklist in the legacy aircraft does call for an emergency descent down to 13, 500, while the NG says only to do it if the cabin altitude is above 10k.

Also, the maximum altitude (airspeed dependent) for an airstart is FL200. The service ceiling of the aircraft is FL300, so you may have to drift down to attempt an airstart.

Personally, I wouldn't be in a hurry to lose altitude. That's what they make O2 masks for.

There is not a minimum glide icing speed that I am aware of. If you are in pusher ice mode (prop heat on, inertial sep open) the pusher will "push" 8 degrees AOA sooner, so it is important to not get slow.

 

[cmill]

The only thing that drives me bat crazy about this is the lack of common sense. I know ill get flamed, but everyone is hell bent on the use of checklist and EPs.

In my mind its pretty simple. If you think you can make a field or a strip, go for it. If you're SOL and have nothing better to hope for, then go for a re-light. Just because its not in the EPs doesnt mean it isnt possible.

If i knew i had a safe spot made, then EP or not, im going for it. If things are questionable, im going for the safest spot and trying to relight on the way down.

Most of the time in the PT-6 all it comes down to is a question of using ignitors and getting the blades turning. You dont sacrifice anything by using ignitors, and the prospect of a hot start is much better than a forced landing in trees.

 

[TUCKnTRUCK]

Most of the time in the PT-6 all it comes down to is a question of using ignitors and getting the blades turning. You dont sacrifice anything by using ignitors, and the prospect of a hot start is much better than a forced landing in trees.

Thats pretty much my thoughts, either with fuel and igniters, it will run, or the thing really isn't going to run at all. So long as you have airflow through the engine, and you're not set at take off power, you won't hot start it.

Even if you do, you have a transient window thats pretty forgiving, and if you have a windmilling prop, that will be turning the power turbines, helping to extract the exhaust gases. Also, the design of the exhausts on the the pt are extractor exhausts, which will help scavenge the exhaust gases.

I am honestly surprised that for an engine failure, you don't select the CL's to start.feather or whatever your position is ( Low/High) maybe?and igniters on. Unless the PC 12 has the combined prop/CL, you can still feather it.

( I should add in quotes, Above is true, unless you have a Rouge Wookie FO that randomly decides to put the props into reverse, and then shut the engines down while you're briefing an approach... In which case you're prob. screwed.)

 

[Stonefly]

The only thing that drives me bat crazy about this is the lack of common sense. I know ill get flamed, but everyone is hell bent on the use of checklist and EPs.

In my mind its pretty simple. If you think you can make a field or a strip, go for it. If you're SOL and have nothing better to hope for, then go for a re-light. Just because its not in the EPs doesnt mean it isnt possible.

If i knew i had a safe spot made, then EP or not, im going for it. If things are questionable, im going for the safest spot and trying to relight on the way down.

Most of the time in the PT-6 all it comes down to is a question of using ignitors and getting the blades turning. You dont sacrifice anything by using ignitors, and the prospect of a hot start is much better than a forced landing in trees.

Flamed? What you're saying is what you're supposed to do. Set up best glide, secure the engine (that unfeathered propeller creates TREMENDOUS drag), and fly towards the landing spot that you've already selected ('cause you're always keeping in mind where you're going to go if...). Then, if time & circumstances permit, go for a relight.

Pretty straight forward stuff.

 

[cmill]

well, my point was, why is it considered hazardous to try a non starter restart? If you have the altitude, go for it, if not, then do your best.

I might have not been clear enough when i said relight. I meant restart with no starter. A few drinks will do that.

 

[minitour]

well, my point was, why is it considered hazardous to try a non starter restart? If you have the altitude, go for it, if not, then do your best.

I might have not been clear enough when i said relight. I meant restart with no starter. A few drinks will do that.

I agree. And if I'm hanging out at FL300 with an airport right below me, I'd probably shove the nose over with the prop feathered and REALLY let that turbine start windmilling while spiraling over the field.

....then land right away and let mx figure out why it crapped out on me to begin with.

-mini

 

[Stonefly]

well, my point was, why is it considered hazardous to try a non starter restart? If you have the altitude, go for it, if not, then do your best.

I might have not been clear enough when i said relight. I meant restart with no starter. A few drinks will do that.

Why do a non-starter assisted start? Unless you are in a legacy aircraft with a single batt, then there is no advantage in attempting a non-starter assisted start. The discussion here has not been about whether it's "hazardous".

Common sense should prevail. As I mentioned, the legacy aircraft EP says to do an emergency descent down to 13, 500. Why? As I said, that's what O2 masks are for.

 

[Itchy]

What about a failure at glideslope intercept? How about just as you turn inbound on the procedure turn? How about when you are 30 miles west of TEB at 2000'? Just playing devil's advocate. There are times when you won't make it to an airport after an engine failure. But considering the reliability of the -67B/P, I'm not going to lay awake tonight worrying about it.

Never fully trust a PT6, or any engine. And all this talk of relights is great, but when they let go with great gobs of groan, no relight is going to happen.

We used to do relights in a cheyenne II on 6 month rides, with no starter. I would never do that these days, but back then it was "normal" for us to do that. Not smart perhaps but hey, it was the 80's.

It was funny when they did that with a garrett, could not get it to come out of feather. Bring it in on one!

 

[Stonefly]

I agree. And if I'm hanging out at FL300 with an airport right below me, I'd probably shove the nose over with the prop feathered and REALLY let that turbine start windmilling while spiraling over the field.

....then land right away and let mx figure out why it crapped out on me to begin with.

-mini

OK, but what will you do at FL300 in IMC with solid IMC below you?

Your statement sounds cool, until you think it through...

 

[Itchy]

OK, but what will you do at FL300 in IMC with solid IMC below you?

Your statement sounds cool, until you think it through...

?? You're going down. Make the best of it.

 

[cmill]

OK, but what will you do at FL300 in IMC with solid IMC below you?

Your statement sounds cool, until you think it through...

What are your other options at any altitude in a single engine in solid IMC?

 

[Bandit_Driver]

What are your other options at any altitude in a single engine in solid IMC?

Our Father who art in heaven.....

 

[ackeight]

Our Father who art in heaven.....

:yeahthat: I'll go back to my previous statement. If you make it out alive you made the right choice. If you didn't then it doesn't matter anyways now does it?

 

[Stonefly]

?? You're going down. Make the best of it.

My point was referring to: "And if I'm hanging out at FL300 with an airport right below me, I'd probably shove the nose over with the prop feathered and REALLY let that turbine start windmilling while spiraling over the field."

Make the best of it? That's my point. He neglected to mention the liquor in the catering drawer.

Seriously though, an engine failure at cruise in the PC-12 is not a shove the nose over, build the airspeed excessively, spiraling, so I can get on the ground maneuver.

You've got plenty of time to work the problem, as I said up to about 30 minutes (and SoonerAv8r mentioned 48,312 square miles). Regardless of IMC/VMC, set your self up for a precision approach. Utilizing the autopilot to reduce your workload, hold airspeed, and basically set up a hold at the final approach fix, not over the field.

Now you have time, possibly, to try for an airstart. Perhaps you had time to attempt a restart as you navigated to your intended landing site, but if not, now's a great time to try it.

At approx. 1000-2000' above the final appraoch fix altitude on the inbound course, now lower pitch to gain airspeed, to intercept the glideslope, and shoot the approach and land.

That's how I'd make the best of it.

 

[minitour]

OK, but what will you do at FL300 in IMC with solid IMC below you?

Your statement sounds cool, until you think it through...

Am I still right over the airport?

Shove the nose over and try to get it started. If not, then you set up for your glide and start praying.

If I'm not still right over the airport, then it's a completely different scenario than the one I posted.

What if you were on fire?

What if you had the fish?

How long can we play "what if"?

If you've got 20 minutes from FL300, then how long do you have from FL200? 12 minutes? Plenty long enough to glide out to the FAF, do a turn or two and hope you have it figured out juuuuuuuuuuust right.

Why wouldn't you sacrifice 10,000' for some airflow to turn the motor when you're at FL300? Hell, even sacrifice 15,000' from FL300? Seems pretty straight forward to me...assuming the plane really glides as well as everyone says it does.

If you can make the 180 back to the runway from 700' AGL, you can certainly go out to the marker, turn around and come back in from 15,000' and definitely from FL200.

-mini

 

[Callador]

The Pt-6 will start below 10% ng...

I know different applications have different procedures, but underneath it all, they are the same... and I've seen one started at 8% accidentally. Warm, yes, but it started ok.

Dang, how warm did that get? I think the lowest I have seen is 12% and that was pushing 850C T5. I think we get 1080 for 2 secs on a start for our PT6's, not sure what other aircraft or other pt6 engine models get... I bet that was a hot start at 8%!!!