Pilatus PC-12 down in Chamberlain, South Dakota, 9 dead.

[WillFlyForCheese]

https://apnews.com/0e07709d1a0a4d439c700f0fc0b4fc40


Pilatus PC-12 had 12 people on board when it crashed at about 12:30 p.m. Saturday, shortly after taking off from Chamberlain, about 140 miles (225.3 kilometers) west of Sioux Falls.

[India Four Two]

LIFR at the time (which I had to look up - Low IFR - a confusing conflation of Rules and Conditions - ceiling <= 500’ and visibility <= 0.5 miles)


https://cimg6.ibsrv.net/gimg/pprune.org-vbulletin/750x737/a34ecc72_7142_4f60_8fa6_298d154c9e11_7602fada56d3227dcd1acbf 288d76b20141ef8ca.jpeg


Snowing, 1° and no Dew Point spread. Not a good day.

[Sobelena]

A total of 12 souls on board. Not overly familiar with the PC-12 but I thought 11 was the max (incl cockpit). May have been an infant of course.

[Feathers McGraw]

A total of 12 souls on board. Not overly familiar with the PC-12 but I thought 11 was the max (incl cockpit). May have been an infant of course.

Report says youngest passenger aged 7. Does a PC-12 have a dual cockpit?

[SpaceWrangler]

Unless they had a commuter /high density the configuration the max on the PC-12 is Pilot+ Right Seat, 6 executive and 2 commuter seats, so 9 pax total.

[AviatorDave]

Does a PC-12 have a dual cockpit?

PC-12 is certified for single pilot ops.

[DaveReidUK]

All PC-12 variants are certificated for a maximum of 10 pax (including one in RHS) plus pilot. As the youngest on board was clearly not a babe-in-arms, that would suggest the pax limitation was exceeded. A/c was a 4740 kg PC-12/47E.

[Mansfield]

The conditions are nearly perfect for a failure in ground deicing. We shall see.

[421dog]

Last time I was in Chamberlain, deicing capabilities were nil, and hangar space was minimal...

[stevep001]

Had same storm here in Minneapolis, it was great snowman snow...not so great for light AC flying. Agree with other poster that there's probably not a proper FBO on the field -- it's just automated fuel. FlightAware shows it overnighting there, hopefully inside a hangar.

In METAR below, note UP precipitation code in period ending at 1515Z -- would likely be rain snow mix based on what I saw locally yesterday

K9V9 301835Z AUTO 02006KT 1/2SM SN OVC005 01/01 A2930 RMK AO2 T00080008
K9V9 301815Z AUTO 02007KT 3/4SM -SN OVC005 01/01 A2930 RMK AO2 T00080008
K9V9 301755Z AUTO 02007KT 3/4SM -SN OVC005 01/01 A2930 RMK AO2 P0003 60006 T00080008 10010 20003
K9V9 301735Z AUTO 03005KT 3/4SM -SN OVC005 01/01 A2931 RMK AO2 P0002 T00090009
K9V9 301715Z AUTO 03005KT 1SM -SN OVC005 01/01 A2932 RMK AO2 P0001 T00090009
K9V9 301655Z AUTO 04006KT 2SM -SN OVC005 01/01 A2933 RMK AO2 T00080008
K9V9 301635Z AUTO 06006KT 3SM BR OVC005 01/01 A2933 RMK AO2 T00090009
K9V9 301615Z AUTO 06006KT 2SM UP OVC005 01/01 A2933 RMK AO2 T00080008
K9V9 301555Z AUTO 07006KT 1 3/4SM UP OVC005 01/01 A2933 RMK AO2 T00090009
K9V9 301535Z AUTO 07007KT 1 3/4SM -DZ OVC005 01/01 A2933 RMK AO2 T00080008
K9V9 301515Z AUTO 07007KT 3SM UP OVC005 01/01 A2934 RMK AO2 T00080008
K9V9 301455Z AUTO 07008KT 2SM UP OVC005 01/01 A2934 RMK AO2 60003 T00070007
K9V9 301435Z AUTO 07007KT 2SM UP OVC005 01/01 A2935 RMK AO2 T00060006

[OldnGrounded]

Last time I was in Chamberlain, deicing capabilities were nil, and hangar space was minimal...

Don't know the place, but Mansfield's post led me to check and I couldn't find any online reference to deicing facilities or any mention of an aircraft being deiced there.

Also, there aren't a whole lot of accessible weather stations in the area, but, at around noon on Saturday, stations around the region were reporting winds (in MPH) from NNE at between 25-30, with gusts up to 40, inconsistent with the data posted above. Of course, inconsistency in weather stations is a fact of life, even when conditions are actually nearly identical. OTOH, out there on those plains, when it's windy in one place, it's probably windy in most others within a rather large distance.

[mikeh49]

NWS weather history for Chamberlain, 9V9:
30 Nov 12:35 pm 33 33 100 NNE7 0.50 Mod SnowOVC00527.55994.629.30
30 Nov 12:15 pm 33 33 100 NNE8 0.75 Lt SnowOVC00527.55994.629.30
30 Nov 11:55 am 33 33 100 NNE8 0.75 Lt SnowOVC00527.55994.629.30

Consistent with #2 above.

[OldnGrounded]

NWS weather history for Chamberlain, 9V9:
30 Nov 12:35 pm 33 33 100 NNE7 0.50 Mod SnowOVC00527.55994.629.30
30 Nov 12:15 pm 33 33 100 NNE8 0.75 Lt SnowOVC00527.55994.629.30
30 Nov 11:55 am 33 33 100 NNE8 0.75 Lt SnowOVC00527.55994.629.30

Consistent with #2 above.

Yup. Just seems like an odd outlier. But a moderately strong system was moving through there, so, depending on where any spot was in the circulation at a given time . . .

Does anyone know if deicing is actually available at 9V9?

[421dog]

Umm, as I sai above, when I was in there in a king air a few years ago, it was not.

[BlankBox]

https://thecount.com/2019/12/01/kirk-jim-hansen-killed-south-dakota-plane-crash/


...carrying some game with 'em too?

[Spooky 2]

These kind of Part 91 accidents are all to common. The passengers were made up of a closely knit LDS family, as well as a successful business group. Sounds as if they had been on a bird hunting trip in the area as it is well known for that activity. Just because you can afford this kind of aircraft does not make you immune to this kind of accident.

There was another PC12 several years ago that crashed up near Butte, Montana. (?) Same thing as it had more pax than seats. Sounds as if this might be more common than one would think?

[OldnGrounded]

Umm, as I sai above, when I was in there in a king air a few years ago, it was not.

Right. I was just wondering if that is still the case. As Mansfield said, above, the weather looks like it was perfect for icing to be a problem down to ground level.

[OldnGrounded]

These kind of Part 91 accidents are all to common. The passengers were made up of a closely knit LDS family, as well as a successful business group. Sounds as if they had been on a bird hunting trip in the area as it is well known for that activity. Just because you can afford this kind of aircraft does not make you immune to this kind of accident.

There was another PC12 several years ago that crashed up near Butte, Montana. (?) Same thing as it had more pax than seats. Sounds as if this might be more common than one would think?

Yes. I have friends who have long had a distressing habit of pushing their luck with flights like this in the family/family business plane. As seems to be the case, here, there's a pilot in the family who steps in for these flights, which lets them leave the company pilot(s) at home. It doesn't do any good to tell them that discretion is always the better part of valor.

I see, in the local story linked by BlankBox that "Maule Rossow [the state's attorney for the county] said at the time of the crash weather conditions included 'strong winds and snow.'” "Blizzard conditions" were reported around the area and Interstate 90 was closed for some time.

[AviatorDave]

These kind of Part 91 accidents are all to common. The passengers were made up of a closely knit LDS family, as well as a successful business group. Sounds as if they had been on a bird hunting trip in the area as it is well known for that activity. Just because you can afford this kind of aircraft does not make you immune to this kind of accident.

There was another PC12 several years ago that crashed up near Butte, Montana. (?) Same thing as it had more pax than seats. Sounds as if this might be more common than one would think?

Anything known about the pilot‘s experience level? With that weather report and no de-icing available, I personally would rather go on foot.

[OldnGrounded]

Anything known about the pilot‘s experience level? With that weather report and no de-icing available, I personally would rather go on foot.

It looks like it was a good day and time to stay where you were.

It appears that the pilot was 48-yr-old Kirkland Rigby Hansen. Database shows medical current and:

PILOT/PRIVATE - AIRPLANE MULTIENGINE LAND
PILOT/PRIVATE - AIRPLANE SINGLE ENGINE LAND
PILOT/PRIVATE - INSTRUMENT AIRPLANE

[Spooky 2]

Anything known about the pilot‘s experience level? With that weather report and no de-icing available, I personally would rather go on foot.


Have not heard anything regarding the pilot other than he did not survive. Have a good friend that is flying a PC12 in the Idaho region and was impressed with the factory checkout including having a PC12 check airman fly with him for awhile, including short field, mountain type work. I think the airplne is pretty capable of handling icing conditions assuming it is operated accordingly.

[JLWSanDiego]

If I recall correctly the Montana accident several years ago was related to the lack of an anti-freezing agent in the fuel ?

[20driver]

If I recall correctly the Montana accident several years ago was related to the lack of an anti-freezing agent in the fuel ?
Yes, for some reason the PIC, a professional pilot, did not take prist in the fuel. They ended up with a fuel tank imbalance issue and basically rolled in turning base to final. It was a group of families from So Cal with a few infants. Very sad.
That is a very capable airplane. I'd love to own one!
20driver

[India Four Two]

at around noon on Saturday, stations around the region were reporting winds (in MPH) from NNE at between 25-30, with gusts up to 40, inconsistent with the data posted above.

I did wonder about the reported low windspeed in the METAR I posted, given the weather we had experienced the day before (north west of SD).

Since it was an AUTO METAR, is it possible that the anemometer was stuck? Is there any BITE equipment in an automated weather station?

[Zeffy]

https://www.ntsb.gov/news/press-releases/Pages/nr20191202.aspx


Update on NTSB Investigation Into Fatal Crash of Pilatus PC-12 Airplane in South Dakota

12/2/2019

The National Transportation Safety Board released the following factual information Monday about the agency’s ongoing investigation into Saturday’s fatal crash of a Pilatus PC-12 airplane in Chamberlain, South Dakota.
The crash occurred at about 12:30 p.m. CST shortly after departure from Chamberlain Municipal Airport. Nine of the 12 occupants of the airplane suffered fatal injuries in the crash. The three survivors were injured.

The pilot and passengers arrived in Chamberlain on Friday, Nov. 29 at about 9:30 a.m. CST for an annual pheasant hunting trip. Shortly after arrival, the pilot purchased 150 gallons of Jet A fuel from an automated fuel pump. The airplane remained parked on the airport ramp until the accident flight on Nov. 30.

https://cimg9.ibsrv.net/gimg/pprune.org-vbulletin/2000x1500/vcsprasset_3567839_130406_4a37ec11_f856_4c5b_bef3_b1d6a0c1ed 0c_0_f26b598690f095aeeb39b2e8425e80bf0a436e60.jpg
NTSB
(In this photo, taken Monday in Chamberlain, South Dakota, an NTSB air safety investigator begins the initial examination of the wreckage of the Pilatus PC-12 that crashed on Nov. 30, 2019, at 12:30 p.m. CT shortly after departure from Chamberlain Municipal Airport. NTSB Photo.)

The pilot filed an instrument flight rules plan with the Federal Aviation Administration and received a clearance to fly direct from Chamberlain, a non-towered airport, to Idaho Falls, Idaho, with a planned departure time of 12:20 p.m. CST. The plane departed Chamberlain at 12:26 p.m. CST. When the pilot did not activate the flight plan after departure, the FAA issued an alert for a missing airplane.

At 12:35 p.m. CST, an AWOS-3 automated weather observation station at the Chamberlain airport recorded weather as follows: winds from 020 degrees (north/northeast) at 6 knots (7 mph), ½ mile visibility with moderate snow and icing, low-level windshear, and clear air turbulence conditions with overcast skies. The base of the cloud layer was recorded at 500 feet above the ground.

The airplane departed on runway 31 and crashed in a field about 1 mile north of the airport. The Pilatus PC-12 airplane is not required to be equipped with a cockpit voice recorder or a flight data recorder. Investigators will be looking for any avionics or engine monitoring equipment with non-volatile memory that could yield information relevant to the investigation.

The airplane was equipped with an automated dependent surveillance broadcast system (ADS-B), which records parameters that will help investigators determine the performance of the airplane by evaluating the flight track, altitude and speed from takeoff to the end of the flight.

Three NTSB investigators arrived at the accident site Monday afternoon after being delayed by inclement weather. Over the coming days they will work on documenting the airplane and wreckage pattern, examining its systems, flight controls, and engine. In addition, any witnesses to the crash will be interviewed. Interviews with the surviving passengers will also be requested.

Investigators are expected to complete their work in Chamberlain by the weekend. A preliminary report, detailing the factual information developed at this early stage of the investigation, will be published in about two weeks. The entire investigation, which will result in a determination of probable cause and will list any contributing factors, is expected to be completed in 12-24 months.
###

[cappt]

If you zoom the picture up it looks like ice on the leading edge of the prop blade and the leading edge of the horizontal tail.

[OldnGrounded]

If you zoom the picture up it looks like ice on the leading edge of the prop blade and the leading edge of the horizontal tail.

It does, but that photo was shot quite some time after the crash and conditions were pretty good for icing on the ground during much of that time.

Of course, the reported conditions at time of departure were just excellent for icing, also.

[capngrog]

That one propeller blade shown on the investigator's right shows little damage and no chord-wise scratching or gouging. The other blades show spanwise deformation, but little or no chord-wise damage/marking. Was the engine producing power at impact?

Regards,
Grog

[pattern_is_full]

What I see in that picture (and feel free to critique):

- minimal leading edge damage to the prop blades, and the roots look feathered? Either engine problem (could include inlet icing), or intentionally stopped and feathered when pilot decided ground contact was inevitable?
- engine/prop ejected from airframe a substantial distance (60-70ft/20m?) - bent blades from tumbling across ground?
- left wing/flaps in middle-distance, cabin in background.
- hummocks on ground fouled up a possibly-more-survivable forced landing?

[RatherBeFlying]

Was the wing clean on the ground before takeoff?

Did anybody get up on a ladder or platform to check the tail?

The operator, West Wind Aviation, had some de-icing equipment in the terminal building (see photos) at the airport. The de-icing equipment that was available to WestWind Aviation in Fond-du-Lac consisted of two ladders, a hand-held spray bottle with electric blanket and wand, and a container of de-icing fluid. However, the aircraft was not de-iced before takeoff, and the takeoff was commenced with ice contamination on the aircraft.

Canada TSB Investigation of Fond du Lac crash (http://www.bst-tsb.gc.ca/eng/enquetes-investigations/aviation/2017/a17c0146/a17c0146.html)

[Luc Lion]

According to Pilatus, the PC-12 can have a 10+1 seating configuration.
https://www.pilatus-aircraft.com/en/fly/pc-12
If it was the configuration of the accident airplane, it still means that an adult and the child of 7 were sharing a seat.

[BlankBox]

...dunno if the intro pic is legit...

Kathryn's Report: Pilatus PC-12/47E, N56KJ: Fatal accident occurred November 30, 2019 near Chamberlain Municipal Airport (9V9), Brule County, South Dakota (http://www.kathrynsreport.com/2019/11/pilatus-pc-1247e-n56kj-accident.html)

...but if so that would'a been one hell of a load on a good day...

[OldnGrounded]

...dunno if the intro pic is legit...

Kathryn's Report: Pilatus PC-12/47E, N56KJ: Fatal accident occurred November 30, 2019 near Chamberlain Municipal Airport (9V9), Brule County, South Dakota (http://www.kathrynsreport.com/2019/11/pilatus-pc-1247e-n56kj-accident.html)

...but if so that would'a been one hell of a load on a good day...

That's the same photo their hometown newspaper is using; the logo of the Thunderstik Lodge, where they were staying, is visible in the photo; it's pheasant season in South Dakota; and the number in the photo matches the reported number of pax. The dead and injured listed in the news story all appear to have been male. Is that consistent with the people in the photo?

[atakacs]

I obviously have no idea of what happened but it would seem they were pushing the bounds in many aspects (weather, pax load). Doesn't bode well...

[Sikpilot]

Overweight
Out of cg
Ifr
Icing conditions

You could have started the accident report before they even took off. So very very sad.

[Pilot DAR]

The reported events have me thinking of this Caravan hunter's flight accident years ago:

https://aviation-safety.net/database/record.php?id=20040117-0

[20driver]

Overweight
Out of cg
Ifr
Icing conditions

You could have started the accident report before they even took off. So very very sad.

Sadly so often true with GA. I often played a game with my self heading the airport. "What would an NTSB report on my preflight activites read like if things go wrong" Had me turn around on at least one occasion.
I used to read the NTSB reports regularly and I would say that in 90% of the cases the plane should never have left the ground.

[pattern_is_full]

On what basis are we assuming "Overweight" and "Out of CG?"

We know the pilot added about 1000 lbs (150 gallons) of fuel - but did that fill the tanks?

Do we know the actual passenger weights (including minors, but also winter clothing)? Do we know who was seated where (CG)? What was the non-human payload (guns + remaining ammo + game taken)?

Do we know the actual operating empty weight of this particular aircraft?

[20driver]

Looking online max payload on a 47 is 3800 lbs more or less. Given how things creep on planes it wouldn't surprise me if it was at least 200 lbs less.
They took on 150 gallons and would have had at least 75 ? on board when they landed. So I suspect before anyone stepped on board they had maybe 2,200 lbs to play with, 2500 max. 12 people with winter clothes will use that up without bags, guns , ammo or loot. I have never done a W&B on the PC but I was told it has a good envelope.
The NTSB will get a pretty good set of numbers on it but they must have been very close to max weight.
20driver

[atakacs]

The NTSB will get a pretty good set of numbers on it but they must have been very close to max weight.
And not even mentioning snow / ice on the wings / fuselage

[filejw]

Overweight
Out of cg
Ifr
Icing conditions

You could have started the accident report before they even took off. So very very sad.

I think you have missed one item , pretty sure you can add contaminated runway to that list .

[AmarokGTI]

Looking online max payload on a 47 is 3800 lbs more or less. Given how things creep on planes it wouldn't surprise me if it was at least 200 lbs less.
They took on 150 gallons and would have had at least 75 ? on board when they landed. So I suspect before anyone stepped on board they had maybe 2,200 lbs to play with, 2500 max. 12 people with winter clothes will use that up without bags, guns , ammo or loot. I have never done a W&B on the PC but I was told it has a good envelope.
The NTSB will get a pretty good set of numbers on it but they must have been very close to max weight.
20driver

For context only... I haven’t flown a PC12/47 or NG but have plenty of time on a PC12/45. Taking a full load of 9 male pax (my company didn’t want us taking a pax in right hand seat) with standard-ish bag weights, it was not uncommon to find myself limited to about 1,700lbs of fuel at MTOW.

[sandiego89]

And not even mentioning snow / ice on the wings / fuselage

And tail. That is a high tail and wonder if how thorough a check or clear of the horizontal stab especially was done at the austere site.

[Double Back]

Carrying families, or groups like here with hunters (or mountain climbers,) , puts a tremendous pressure on the pilot. In this case he was family also and part of the group. Even more difficult.
Because of all of this he probably wanted himself to take an active part in the gathering so ferrying the plane for a night stop elsewhere was not really on his options list.
Add sports gear, winter clothing, an airport with hardly any facilities given the time of Year.
Like sikpilot writes, an accident report could have been written, even days before the T/O.
Very sad though for the affected families.
Most of us professional pilots have been there one or another way. If You can read this You were lucky, or You took the right decision.

[jimtx]

Carrying families, or groups like here with hunters (or mountain climbers,) , puts a tremendous pressure on the pilot. In this case he was family also and part of the group. Even more difficult.
Because of all of this he probably wanted himself to take an active part in the gathering so ferrying the plane for a night stop elsewhere was not really on his options list.
Add sports gear, winter clothing, an airport with hardly any facilities given the time of Year.
Like sikpilot writes, an accident report could have been written, even days before the T/O.
Very sad though for the affected families.
Most of us professional pilots have been there one or another way. If You can read this You were lucky, or You took the right decision.

It appears that their company had a professional pilot under employ. Suppositions as to why he wasn't flying that trip would range from benign to nefarious.

[Airbubba]

Some suspicions confirmed in the NTSB Preliminary Accident Report, a couple of passages emphasized by me.


This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed.

National Transportation Safety Board
Aviation Accident Preliminary Report

Location: Chamberlain, SD Accident Number: CEN20FA022
Date & Time: 11/30/2019, 1233 CST Registration: N56KJ
Aircraft: Pilatus PC12 Injuries: 9 Fatal, 3 Serious
Flight Conducted Under: Part 91: General Aviation - Personal

On November 30, 2019, at 1233 central standard time, a Pilatus PC-12/47E airplane, N56KJ,
was destroyed during an impact with terrain near the Chamberlain Municipal Airport, (9V9),
Chamberlain South Dakota. The pilot and 8 passengers were fatally injured, and three
passengers were seriously injured. The airplane was registered to Conrad & Bischoff, Inc. and
operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight.
Instrument meteorological conditions prevailed, and the flight was operated on an instrument
flight rules flight plan. The flight originated from 9V9 shortly before the accident and was
destined for Idaho Falls Regional Airport (IDA), Idaho Falls, Idaho.

The pilot and passengers flew from IDA to 9V9 the day before the accident, arriving at 9V9
about 0927. At 0936, the pilot purchased 150 gallons of fuel from the automated fuel pump at
9V9. The airplane remained parked outside on the ramp and the group stayed at a local lodge
for the night. The following morning, the pilot and one passenger were driven to the airport.
Witnesses reported that they worked removing the snow and ice from the airplane for
approximately 3 hours, and were joined by the remaining passengers shortly before the
accident flight. The witnesses reported the visibility was limited by snow at the time of the
accident.

The pilot contacted Minneapolis Air Route Traffic Control Center (ARTCC) at 1224 and
requested an instrument flight rules (IFR) clearance from 9V9 to IDA. The pilot advised he
planned to depart from runway 31 and would be ready in 5 minutes. At 1227, Minneapolis
ARTCC issued an IFR clearance to the pilot with a void time of 1235. No radio communications
were received from the pilot, and radar contact was never established. About 1240,
Minneapolis ARTCC contacted the airport manager at 9V9 who advised that the airplane
departed about 10 minutes earlier. Minneapolis ARTCC subsequently contacted the Brule
County emergency dispatch center and advised them of the overdue aircraft. An alert notice
(ALNOT) was issued.

A witness located about 1/2-mile northwest of the airport reported hearing the airplane takeoff.
It was cloudy and snowing at the time. He was not able to see the airplane but noted that it
entered a left turned based on the sound. He heard the airplane for about 4 or 5 seconds and
the engine seemed to be "running good" until the sound stopped.

The property owner discovered the accident site about 1357. The site was located
approximately 3/4 mile west of the airport in a dormant corn field. The debris path was
approximately 85 ft long and was oriented on a 179° heading. The engine was separated from
the firewall. The left wing was separated from the fuselage at the root. The engine and left wing
were both located in the debris path. The main wreckage consisted of the fuselage, right wing
and empennage.

Preliminary data recovered from the Lightweight Data Recorder (LDR) installed on the
airplane revealed that the accident takeoff began from runway 31 about 1231:58. The airplane
lifted off 30 seconds later and immediately entered a left turn; the airplane rolled left to about
10° during the takeoff rotation. The roll decreased to about 5° left as the airplane climbed
through about 170 ft. above ground level (agl), and then reversed to about 5° right before
rolling left again, reaching 64° left at the airplane's peak altitude of approximately 460 ft agl.
The airplane then entered a descent that continued until impact. The airspeed varied between
89 and 97 knots (kts) during the initial climb; however, it decayed to approximately 80 kts as
the airplane altitude peaked at 460 ft agl and the roll angle reached 64° left. The stall warning
and stick shaker became active approximately 1 second after liftoff. The stick pusher became
active about 15 seconds after liftoff. All three continued intermittently for the duration of the
flight. The data ended about 1233:00. In addition to parametric data, the LDR also recorded
cockpit audio and the NTSB will convene a group of technical experts to produce a transcript of
recorded sound.

At 1235, the Automated Weather Observing System (AWOS) located at 9V9 recorded overcast
clouds at 500 ft agl and 1/2-mile visibility in moderate snow, with wind from 020° at 6 kts. The
temperature and dew point were both 1°C, and the altimeter setting was 29.30 inches of
mercury. A review of the 5-minute observations recorded at 1215 and 1220 indicated light snow
with 3/4-mile visibilities. At 1225, the observation included 1/2-mile visibility in light snow.
From 1230 until 1310, the observations included 1/2-mile visibilities in moderate snow. Winds
were from the north-northeast (010° to 020°) at 7 kts or less during that entire time period.
Freezing rain and snow were observed in the vicinity of 9V9 the previous afternoon and
overnight before the accident flight.

Aircraft and Owner/Operator Information
Aircraft Make: Pilatus Registration: N56KJ
Model/Series: PC12 47E Aircraft Category: Airplane
Amateur Built: No
Operator: On file
Operating Certificate(s)
Held: None

Meteorological Information and Flight Plan
Conditions at Accident Site: Instrument Conditions Condition of Light: Day
Observation Facility, Elevation: 9V9, 1696 ft msl Observation Time: 1235 CST
Distance from Accident Site: 1 Nautical Miles Temperature/Dew Point: 1°C / 1°C
Lowest Cloud Condition: Wind Speed/Gusts, Direction: 6 knots / , 20°
Lowest Ceiling: Overcast / 500 ft agl Visibility: 0.5 Miles
Altimeter Setting: 29.3 inches Hg Type of Flight Plan Filed: IFR
Departure Point: Chamberlain, SD (9V9) Destination: Idaho Falls, ID (IDA)

Wreckage and Impact Information
Crew Injuries: 1 Fatal Aircraft Damage: Destroyed
Passenger Injuries: 8 Fatal, 3 Serious Aircraft Fire: None
Ground Injuries: N/A Aircraft Explosion: None
Total Injuries: 9 Fatal, 3 Serious Latitude, Longitude: 43.765556, -99.337222

Administrative Information
Investigator In Charge (IIC): Timothy Sorensen
Additional Participating Persons: Eric West; FAA Accident Investigation; Washington, DC
Martin Pohl; Swiss Transportation Safety Board; Payerne,
Markus Kohler; Pilatus Aircraft Ltd; Stans,
Bob Renshaw; Pilatus Aircraft (USA); Broomfield, CO
Note: The NTSB traveled to the scene of this accident.

[RatherBeFlying]

I remember arriving on a crisp winter morning to find the C-172 covered in frost and spending some two hours scraping off the frost between the rivet lines. Taking off I had a good look at the ski area in the ravine past the runway.

The wing that day wanted another twenty knots.

Subsequently I kept two cans of windshield washer fluid in the car. Not for use in icing conditions, but for frost removal, you really do have to get the wing and tail sparkling clean.

[Australopithecus]

As I mentioned earlier in this thread, I lost some friends and colleagues in an F-28 crash in 1989. After the accident a study was done to ascertain how critical contamination was on the F-28 wing. As I recall a single grain of sand in one cm2 (6 per sq inch) was enough to destroy the lift. That study was part of the body of knowledge that informed subsequent regulation and current best practice.

As someone mentioned earlier, if you attempt flight with contamination you are a test pilot. You may not like the results of your ad hoc experiment, and if not you probably won’t be around to publish your results.

[421dog]

I’m imagining that this is somewhat more arcane information than the European brethren on the site require, but, as an erstwhile visitor to Chamberlain on a yearly basis, for over a decade, on, usually the weekend after thanksgiving (end of November for the uninitiated), there is no hangar space for anything of any size, and the best deicing option is a trip to the local hardware store (Bomgaars, I think, but in any case really nice people) the night before departure to pick up 10 gallons of polyethylene glycol (“RV antifreeze” which a guy can heat-soak in the bathtub of his hotel room [I recommend The Hillside Motel,as they have pheasant cleaning facilities, a nice eatery across the parking lot, and a liquor store across the street] as well as a pushbroom and a pressure sprayer.)
On a couple of occasions, we applied the pushbroom, saw that we’d be wasting our time trying to put on enough glycol to make it off the ground, went back to the motel and availed ourselves of the local comestibles until conditions improved.

For the last few years, I’ve gone into Winner (KICR) which isn’t too far away, has heated hangars in good supply, and has both de-ice and Anti-ice capabilities.

[rak64]

Some suspicions confirmed in the NTSB Preliminary Accident Report, a couple of passages emphasized by me.

It seems they had wet snow or a mix that looks like water. One tricky fact is, that during the rotation with the generating of lift, the temperature on the upper part of the wing will drop at the same moment. Instantly That causes to freeze all water on the upper side of the wing.

[421dog]

If they had to work for three hours to get the snow and frost off of a medium/large single, I’m thinking that the weather was ahead of them when they started, but maybe things changed.

500 OVC, snowing, and a temp/dew point match is par for the course in the upper Midwest this time of year. It can be an annoyance, or it can be deadly depending on the mitigating factors. I am assuming that a guy qualified to fly an airplane of this size/capability had the wherewithal to make an appropriate decision, and we are all not privy to whatever other information played into the matter.

[cappt]

Thanks 421 for that peek behind the curtain, your a wise Captain who knows how to make it safe and when to call it. Good move heading to Winner.

[Water pilot]

Hypothermia could be the ultimate culprit here, it often is when you see people make unfathomable decisions. If the pilot was working for three hours in nearly freezing weather clearing sloppy wet snow, he would have likely been hypothermic without realizing it. Long before you have any of the obvious symptoms, your reasoning power is impaired. It has happened to me and people around me; after foolishly deciding to snorkel in cold ocean water I caught myself towing my kayak back 1/2 mile to the boat rather than either going ashore to warm up or simply getting in the kayak and paddling. There are many, many examples up here in the Pacific Northwest of poor decision making that led to tragedies or near-tragedies that come down to slightly hypothermic people making poor decisions that were obviously wrong even to them in retrospect.

[what next]

Hello!

If the pilot was working for three hours in nearly freezing weather clearing sloppy wet snow, he would have likely been hypothermic without realizing it.

I have had to remove snow and ice from aircraft in similar conditions for hours on several occasions. The last thing you need to worry about is hypothermia. This is heavy workout whilst wearing winter clothes. If anything, he will have suffered from hyperthermia, dehydration and general exhaustion after three hours of this, depending on his state of fitness. And of course at some point it gets so tiresome - and also pointless and frustrating as the continuosly falling snow will spoil most of your previous effort - that one can easily make the wrong deciction just to get out of that situation.
But of course we do not know if the de-icing state of the aircraft did play a role in this accident.

[Water pilot]

That is actually a common misconception and it can be deadly. Swimmers think that by swimming to shore they can keep themselves warm. Kayakers often take off gear when they are hypothermic, because they are working hard. I'm not a doctor so I can't explain in scientific terms but my understanding of it is that apparent heat that you feel is being generated by your internal fuel supply which is limited and the same fuel supply that powers your brain. The sweating that you do in such a situation makes it worse (one reason that we call cotton "death cloth".) Many people in the later stages of hypothermia have been found in the snow with their clothes off.

Stay warm! (https://www.medicalnewstoday.com/articles/182197.php#stages)

[golfyankeesierra]

I think by now it is clear that this subject has nothing to to on a professional pilot forum. The general aviation forum is a better place. If only for the awareness of other private pilots to learn from this tragic accident.

[Capi_Cafre']

So much of safety lies in asking the right questions. A professional in this situation would have been looking for proof that it was safe to go, preferring to deal with ambiguous information by erring on the side of caution. The poor folks in the back trusted their lives to an amateur who insisted upon proof that it wasn't safe to go.

[RatherBeFlying]

We tend to focus solely on air temperature and many tend to believe that if it's above 0°C, we won't have icing.

But that presupposes that the airframe and precipitation, if any, are also above 0°C.

In this case the airframe was sitting overnight in freezing precip and was cold soaked, including the fuel in the tanks which had been fueled the night before.

​​​​Possibly any precip with liquid content would freeze to the wing skins on contact.

Precip well below freezing will not adhere to a wing well below freezing.

But it has to be remembered that precip in a narrow zone above and below 0°C can have a mixture of solid and liquid content.

On a sunny breezy day well above 0°C, the wing will likely remain clean after de-icing, provided that the wing temperature is well above the dewpoint.

With wing skin temperature below the dewpoint, condensation can occur, especially in the absence of wind and sunshine. That's how frost happens overnight.

[Uplinker]

Jet airliners always apply engine intake anti-icing at air temperatures of +10°C or below, in moisture such as cloud, fog, mist. We apply engine and wing anti-ice whenever ice starts to form at whatever outside air temperature.

Icing can occur at Plus 10°C OAT.

[megan]

Icing can occur at Plus 10°C OATThat may be so for your aircraft Sir, the aircraft I flew used +5°C as the switch on point.For any aircraft type which is certificated for flight in icing conditions, the AFM or POH will contain a manufacturer’s definition of the threshold for ‘Icing Conditions’ for the purposes of the selection or activation of ice protection equipment (https://www.skybrary.aero/index.php/Ice_Protection_Systems). This is usually given as the presence of visible moisture and an Outside Air Temperature (OAT), Static Air Temperature (SAT) or Total Air Temperature (TAT) reading of less than a figure between +3°C and +10°C. Operation of anti icing systems is never based upon the appearance of visible ice or on the flight deck annunciation of external ice detector activation, although de icing systems may be. Visible moisture can be defined in flight as clouds, fog with visibility of 1500m or less, and precipitation. On the ground this can include standing water, slush or snow present on the taxiways or runways.https://www.skybrary.aero/index.php/Aircraft_and_In_Flight_Icing_Risks