PC-12 Crash In South Dakota, 9 dead, 3 survivors (CFIBlizzard?)

mryan75 said:
Does this look like a prop that was turning at impact to you guys?

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And per the NTSB press release, the plane sat outside on the tarmac the entire time they were on the ground: about 27 hours in a heavy snowstorm.

https://www.ntsb.gov/news/press-releases/Pages/nr20191202.aspx
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sure doesn’t to me.
 
The report mentioned the plane sat out in the weather for the 27 hours it was in the ground. Besides the usual surface contamination, snow gets blown in various places.
 
Does the PC-12 inlet have bleed air heat, or some other type of heat?
 
What would cause the turbine motor to quit? And that field looks pretty flat, you would think the pilot could have landed it when the engine quit.

The report also says it sat outside overnight and someone else said there are no services there. With that heavy snow could it have been iced up before it even took off?
 
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Jamie Kirk said:
What would cause the turbine motor to quit? And that field looks pretty flat, you would think the pilot could have landed it when the engine quit.

The report also says it sat outside overnight and someone else said there are no services there. With that heavy snow could it have been iced up before it even took off?
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500 OVC isn’t a lot of time to land under control in a cornfield. The time may be slightly off, not by much.
 
There have been fatals due to fuel contamination, but those involved waterous contaminants such as cleaning solution and diesel exhaust fluid.
 
Jamie Kirk said:
What would cause the turbine motor to quit? And that field looks pretty flat, you would think the pilot could have landed it when the engine quit.
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Full disclosure: I don't fly the NG, just the older ones.

Not having the inertial separator on could do it. Maybe he wanted the probes and prop on and didn't want pusher ice mode activated? Or maybe it was a true mechanical failure of the PT6.. we don't know yet. We won't for quite awhile. The PC12 glides well, but you're not gonna make it back to the airport taking off into 500 overcast and a half mile.
 
What rate of climb would you expect in a PC-12 at max gross weight?
 
My understanding of the PT-6 is that there is no mechanical linkage from the engine to the propeller. So, I don’t think you can connect “prop doesn’t look like it was turning” to engine problem as directly as you can on a piston engine.
 
Sam D said:
My understanding of the PT-6 is that there is no mechanical linkage from the engine to the propeller. So, I don’t think you can connect “prop doesn’t look like it was turning” to engine problem as directly as you can on a piston engine.
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Huh? So how then does the prop turn? Last time I checked the prop was connected to the turbine section via a gearbox and shaft.
 
Sam D said:
My understanding of the PT-6 is that there is no mechanical linkage from the engine to the propeller. So, I don’t think you can connect “prop doesn’t look like it was turning” to engine problem as directly as you can on a piston engine.
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it’s a free turbine but there is still direct mechanical connection between prop and engine.

inside the hot section there are multiple gas turbines that extract energy from the gas flow. On set is attached to a shaft that runs the compressor and engine accessory gear box.
The other set is attached to a different shaft that goes the opposite direction and drives the gearbox and prop. There is no mechanical connection between these two turbine sections.

if you walk up to an aircraft with a PT-6 and turn the prop the only thing you are turning is the gearbox and power section turbine wheels. The first stage turbine, compressor section and accessory gearbox do not move.

do the same thing to @Ted DuPuis MU-2 and the entire engine spins because it’s not a free turbine. Everything inside is connected.
 
Tarheelpilot said:
it’s a free turbine but there is still direct mechanical connection between prop and engine.

inside the hot section there are multiple gas turbines that extract energy from the gas flow. On set is attached to a shaft that runs the compressor and engine accessory gear box.
The other set is attached to a different shaft that goes the opposite direction and drives the gearbox and prop. There is no mechanical connection between these two turbine sections.

if you walk up to an aircraft with a PT-6 and turn the prop the only thing you are turning is the gearbox and power section turbine wheels. The first stage turbine, compressor section and accessory gearbox do not move.

do the same thing to @Ted DuPuis MU-2 and the entire engine spins because it’s not a free turbine. Everything inside is connected.
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The above is correct. On the TPE-331 you have a single shaft that connects the gearbox, compressor (2 stages) and turbine (3 stages). In fact, that's part of why you see people (like me) spinning the props on TPE-331 engines after shut down. Doing so spins the compressor, which moves air through the compressor, combustor (that's the important part) and turbine section. That airflow helps to cool off the fuel nozzles and prevent coking.

Interestingly, the King Air B100 is the only TPE-331 powered aircraft to not recommend that, apparently because Beechcraft found it undignified to tell the pilots to spin their propellers.
 
Referencing the above picture the prop would be bolted to left hand side of engine and accessory gearbox lives on the right side.

starting from the intake on right side there are 5 stages of compression then three stages of turbine.

Continue from right to left the first turbine wheel is driving all the stuff to the right side. There is a small space to make room for bearings and then two wheels driving the gear box/prop to the left.

if you turn the prop the only thing turning inside would be the gear box and the two turbine wheels on far left of picture. Everything else would be stationary.
 
Ted DuPuis said:
which moves air through the compressor, combustor (that's the important part) and turbine section. That airflow helps to cool off the fuel nozzles and prevent coking
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Cool note, thanks! Question though.. do the free turbine planes not have this cooling / coking problem? What about regular turbofan engines? Is this a "problem" unique to the Garrett?

Ted DuPuis said:
because Beechcraft found it undignified to tell the pilots to spin their propellers
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:rofl:
 
Tantalum said:
Cool note, thanks! Question though.. do the free turbine planes not have this cooling / coking problem? What about regular turbofan engines? Is this a "problem" unique to the Garrett?
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To be honest I'm not even sure how much of an issue it truly is on the Garrets, but it's cheap insurance, doesn't hurt anything, and might help. I know that every... I think it's 400 hours I'm supposed to have the fuel nozzles cleaned. Last inspection I had it done on one engine, this coming inspection I'll have it done on the other. Basically what happens is the fuel spray becomes less atomized if they coke up (more of a stream than a spray) and that can produce localized hot spots which can burn through expensive parts like combustors, turbine wheels, stators, etc.

However to answer your question, yes, every other turbine engine has the potential for this to occur. When I worked at Meatball Aircraft Engines, we did see issues with oil coking up, most notably when airlines did not observe the required cool-down period on the engine. And a lot of them didn't. Land, get off runway, shutdown one engine, taxi in on the other to save fuel. However I don't recall any fuel nozzle coking issues coming up.
 
Ted DuPuis said:
In fact, that's part of why you see people (like me) spinning the props on TPE-331 engines after shut down.
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That might be one reason. But the MAIN reason you do it is because it looks cool...
 
benyflyguy said:
That might be one reason. But the MAIN reason you do it is because it looks cool...
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The main reason I do it is because all the instructors I had on TPE-331s have said to do it. I have enough other things to do after landing besides spend time answering "What're you doing, rewinding the rubber band in the engines?"

The MU-2 is what looks cool. ;)
 
sourdough44 said:
Word is they couldn’t fly Sunday, ‘Latter Day Saints’ faith prohibited, then had an event he/they ‘NEEDED’ to be back for Monday. That sort of stuff can upset someone, me.
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This would be, if a true statement by the deceased, a personal interpretation of the Church doctrine. The Church of Jesus Christ of Latter Day Saints has no such formal doctrine. People are quite free to interpret how they honor the Sabbath day, with only very loose guidelines. They may have wished to be back in time for Church, and may have had responsibilities that they felt they needed to honor. But no restriction on flying or traveling. Very sad event, and a very generous and charitable family devastated.
 
AKBill said:
What rate of climb would you expect in a PC-12 at max gross weight?
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Off the cuff, initially north of 1200

I see DZ and near zero C, wonder if that turned into some freezing precip, heavy, and with all the area those flaps add at 15 for takeoff to the wing, if your wing wasn’t doing all the work it could do due to contamination, maxed out weight going to flaps 0 shortly after takeoff, thus shrinking your wing, and what lift it is making to counter the weight
 
Omalley1537 said:
sure doesn’t to me.
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Yes it does look like it hit under power. 2 of the 4 blades are bent, and that is a solid metal prop. It will stop the engine when it hits something hard.

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Like this Meridian that flew into the ground short of the runway under power in low IFR conditions with 3 bent and one perfect blade. These solid metal Hartzell paddle props are nearly indestructible.

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Given what has been said about the height of the T-tail and the lack of deicing at the airport, I'm guessing tailplane stall....not engine related in any way.

Bob
 
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