Plane Crash in Blizzard-Like Conditions Kills 9 in South Dakota.

[kent olsen]

The Hawker I think was back around 2002-2004.

[ATLcrew]

The Hawker I think was back around 2002-2004.

Still trying to find it, no luck.

[Gabriel]

https://www.flyingmag.com/story/news/nstb-pc-12-report-shows-stall/?utm_source=internal&utm_medium=email

[Evan]

https://www.flyingmag.com/story/news...m_medium=email

Not too flattering.

[ATLcrew]

ateering

Not too flattering.

But pretty flatteNing.

[3WE]

Not too flattering.

I note that they spent 3 hours working on the plane AND the temperature was 1C.

That doesn’t necessarily support icing. Need to see W&B to see if that is kosher.

[Evan]

I note that they spent 3 hours working on the plane AND the temperature was 1C.

That doesn’t necessarily support icing. Need to see W&B to see if that is kosher.

Well, time spent doesn't mean anything if it wasn't done right. Also, was it anti-iced? What was the temperature in the low pressure areas of the wing surfaces on takeoff?

[ATLcrew]

Well, time spent doesn't mean anything if it wasn't done right. Also, was it anti-iced? What was the temperature in the low pressure areas of the wing surfaces on takeoff?

I'd be particularly curious how well they deiced the tail (if at all), especially since doing so would have required at least a ladder. That said, I, too, am somewhat hesitant to ascribe this one to icing. The PC-12, unlike the C208, is somewhat overpowered and well-known to be able to carry between a "crapload" and a "boatload" of ice without too much drama, so I would expect the airplane to have made it well past 460' before anything difficulties developed, if ice were the issue.

[Evan]

I'd be particularly curious how well they deiced the tail (if at all), especially since doing so would have required at least a ladder. That said, I, too, am somewhat hesitant to ascribe this one to icing. The PC-12, unlike the C208, is somewhat overpowered and well-known to be able to carry between a "crapload" and a "boatload" of ice without too much drama, so I would expect the airplane to have made it well past 460' before anything difficulties developed, if ice were the issue.

I got the impression that the crash was ultimately the result of a pitch-induced stall, essentially a plane that wouldn't climb being pulled up relentlessly. If the tailplanes were iced, would that fit this scenario (perhaps ice/snow being jammed in the aerodynamically protected hinge areas)? I'm not confident about icing being the root cause, but it seems like the most obvious place to start here and I don't see anything that rules it out yet. Perhaps ice combined with weight/balance issues, combined with bad instincts...

[Gabriel]

Well, time spent doesn't mean anything if it wasn't done right. Also, was it anti-iced? What was the temperature in the low pressure areas of the wing surfaces on takeoff?

The pressure reduction in the low-pressure area of the wing is small, and also the temp is small. On top of that, what makes the water freeze is the temp of the surface, not the temp of the air. And note that ice in flight (that is where there exist a low-pressure zone on the wing) accumulates mostly in the leading edges of wings, tails, propellers and engine nacelles, and in the windshield, i.e. where the air "hits" the plane, which are not the low-pressure zones, rather the opposite.

A more appropriate question can be, ok, the temp was 1C (i.e. barely over freezing) but the airplane had been parked overnight at much lower temperatures, The external surface of the plane was likely still quite colder than 1C (or than 0C).

if it was not raining or snowing at the time they deiced the plane, then it is unlikely that any significant amount of ice would have developed on the wings before take-off even if the surface of the plane was under freezing conditions, so the application (or not) of anti-icing fluid would not have been a factor. And it is unlikely that any significant amount of ice accumulated in the 2 minutes that the flight lasted, most of which was likely not in the clouds since the ceiling was reported at 500 ft and the plane never climbed above 460 ft agl, and in any event the airplane's anti-ice system should have been able to cope with anything but sever icing in flight.

However, moderate snow was reported at the time of the accident.

So, for the icing part, that leaves snow/ice accumulation between deicing and take-off or some very sever icing in the tail that was not cleared (perhaps due to the lack of a ladder) as ATL mentioned.

The plane might have been somehow overweight, but that alone would also hardly explain the accident. A plane that is horrible overweight (say 20% which is A LOT since that would mean about 50% more useful load) would have a stall speed of less than 10% above the normal one (rotation speed is already more than that). The airport elevation is 1700 ft and with a temperature of 1C that would give you about 500 ft of density altitude (that is, nothing: in those conditions the air density is about 98.5% of the standard sea level density). With a runway 4300 ft long, the plane should not have had any problem to achieve a safe climb speed on the runway, and then safely climb even if the climb rate was a bit compromised. And, probably the plane was not THAT overweight anyway.

Now, the plane did achieve between 89 and 97 knots during the initial climb. The stall speed at MTOW and flaps 15 is 76 kts (83 if 20% overweight) and the take-off distance over a 50ft obstacle is 3500 ft. A more normal take-off position would be 30 degrees, which would lower the stall speed and ground roll and increase just a bit the distance to 50 ft.

One interesting part is that the stall warning and stick pusher activated 15 seconds after after liftoff and continued intermittently until the crash. So why was that? We don't know at what speed they lifted off, of they lifted off at 89 kts and were very overweight, the stall warning might have activated at that speed since it activates about 10% faster than the stall warning. If the wing was producing less lift than normal due to icing, then you would need a larger AoA at a given speed to achieve the needed lift and hence the stall speed may go off faster than normal. Perhaps a combination of overweight and icing. Perhaps the ceiling/visibility during the loft off was much worse than reported and the pilot got disoriented and pulled up too much. Perhaps for some reason the engine was not delivering full power and the pilot did actually a great job keeping the speed/AoA around the onset of the stickshaker but the plane would not climb and, after fighting for 2 minutes, the pilot lost it (2 minutes is quite a bit to be "fighting"). Perhaps, perhaps, perhaps...

The bottom line is that we don't have enough information to know, and even to speculate in one specific direction. There are still many ways how this accident may have happened. I will not say "wait until the final report" but we will need more factual information to narrow the possibilities.

Icing may have been a big causal factor, or the plane may have been perfectly clean of any ice or snow, or anything in between. We just don't know yet.

[ATLcrew]

The pressure reduction in the low-pressure area of the wing is small, and also the temp is small. On top of that, what makes the water freeze is the temp of the surface, not the temp of the air. And note that ice in flight (that is where there exist a low-pressure zone on the wing) accumulates mostly in the trailing edges of wings, tails, propellers and engine nacelles, and in the windshield, i.e. where the air "hits" the plane, which are not the low-pressure zones, rather the opposite.

You mean the leading edges, right? I've never seen ice on a trailing edge, but that might be just my credentials talking...

[3WE]

A more appropriate question can be, ok, the temp was 1C (i.e. barely over freezing) but the airplane had been parked overnight at much lower temperatures, The external surface of the plane was likely still quite colder than 1C (or than 0C).

Wings made from thin aluminum with relatively low specific heat...Doesn’t mean there couldn’t be but again, very shaky to assume inadequate efforts or cowboy unflattering deicingmanship.

We just don't know yet.

Did I say we knew? I said I wanted to see some W&B estimates, and long ago said it might be a combo of the two, or perhaps a meteor.

[Evan]

Did I say we knew? I said I wanted to see some W&B estimates, and long ago said it might be a combo of the two, or perhaps a meteor.

Exhibit A: Ice acretion on the trailing edge of a meteor.

[Gabriel]

You mean the leading edges, right? I've never seen ice on a trailing edge.

Correct, I meant leading edges. My mistake (now corrected in the original post). Thanks for catching it.

[Gabriel]

Wings made from thin aluminum with relatively low specific heat.

And full of fuel at sub-zero temperature.

Did I say we knew?

Did I say you did? I wasn't even replying to you but to Evan.