PC 12 down in Nevada - 5 Fatalities

dmspilot said:
The turn rate and groundspeed suggest an average bank angle of 60° during a 360° turn, with the average bank angle closer to 70° during the second half of that turn. Bank angle may have reached 80° by the last ADS-B return which would result in a load factor of 5.76. This exceeds both the limit load factor of 3.8 and ultimate load factor of 5.7 for a normal category airplane. Possibly the last ADS-B return captured the breakup in progress as there is a sudden loss of groundspeed.
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Maybe. But the vertical speed by my guesstimate is 120 kts and the horizontal speed halfway between 180 and 240 (back of the envelope figurin'). That gives a vertical pitch between 30° and 45° downward which in my opinion would more likely be caused by a structural failure, not the other way around. Time will tell.
 
kayoh190 said:
One thing's for sure, you definitely fit in over at APC. ;) But anyway. Spatial disorientation, okay. Certainly possible - and I don't think anyone has indicated otherwise. Offer up some solutions, objectionable by the industry or not. How do we fix it?

I've always thought that one thing the industry could do is focus more on being 'startled' into suddenly having to hand fly. We all do just fine when we know it's coming, but perhaps the transition our brains are forced to make from being the aircraft manager to suddenly having to rely on our scan is problematic - especially when a lot of other stuff (weather, failures, etc) is going on.
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Yeah but do we really think spatial d is a fix? You can try and mitigate but there will never be a fix for a human factors issue like this.

Two pilots? I don’t think anyone would disagree that two sets of eyes would be better than one. Of course there’s always the excuse that the Part 135 operators can’t afford two pilots. It’s not that the industry can’t afford them, they just aren’t out there. No different than the rotor side, in EMS we can barely staff an aircraft with one pilot, let alone two. We’ve got 151 fixed wing openings right now. Even more on the rotor side. Just aren’t enough qualified applicants out there.
 
dtuuri said:
Maybe. But the vertical speed by my guesstimate is 120 kts and the horizontal speed halfway between 180 and 240 (back of the envelope figurin'). That gives a vertical pitch between 30° and 45° downward which in my opinion would more likely be caused by a structural failure, not the other way around. Time will tell.
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I don't think there are many conventionally configured aircraft that would be able to stay under 75° if the tailplane failed. More like nearly 90°. Think of the horrors of mere aft-CG loading. I think he pulled the tail off.
 
Here's a quote appearing in a thread on the PPRuNe website concerning the crash:

"An "ear-witness" heard the plane overfly her house, the last few seconds of its trajectory, with a high pitch engine noise and several 'backfire' sounds, before the final thump noise.
They tried to locate it in the surrounding fields, but it was snowing and low visibility, and passed by a few times 20ft or so away, without finding it (so I presume no post impact engine fire - not implying fuel starvation)"

The "backfire" sounds could have been the sounds of a structural breakup. This is pure speculation on my part, but a possible breakup sequence could have been: loss of elevator (with resultant loss of pitch control), loss of horizontal stabilizer, causing an abrupt nose down pitch, resulting in negative G causing failure of a portion of the wing structure. This breakup sequence could have caused a flat spin ... all the way to impact. Terrible to contemplate, beyond my understanding to describe the horror of experiencing this. R.I.P.
 
dtuuri said:
vertical speed by my guesstimate is 120 kts and the horizontal speed halfway between 180 and 240
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Last ADS-B data on adsbexchange says -

174kts GS
32640 feet per min descent = 322kts
Vector addition gives (Pythagoras) 366kts

This was at about 10,000 ft and terrain is about 5,000.

I think NTSB said that the horizontal stab assembly was found 1/2 mile from the aircraft.

I think it was Blancolirio that said ATC requested that he "Ident". To see the panel where the switch is located was a head down and turn to the side movement. I understand that this can be a trigger for spatial disorientation. The flight path instability started soon after. Obviously I have no idea if any of this was related to the cause of this tragic crash. We will have to wait and see.

https://globe.adsbexchange.com/?ica...e=2023-02-25&trackLabels&timestamp=1677301999

upload_2023-2-27_19-40-31.png
 
dtuuri said:
Maybe. But the vertical speed by my guesstimate is 120 kts and the horizontal speed halfway between 180 and 240 (back of the envelope figurin'). That gives a vertical pitch between 30° and 45° downward which in my opinion would more likely be caused by a structural failure, not the other way around. Time will tell.
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What is that based on?

Break the spiral up into slices.
05:13:30 - 19,100
05:13:41 - 17,800 (7,090 fpm)
05:13:51 - 15,600 (13,200 fpm)
05:13:56 - 13,600 (24,000 fpm)

I am seeing a graveyard spiral, followed by an in-flight breakup, textbook.
 
sourdough44 said:
A 2019 airframe? No, parts didn’t fall off for no reason, likely over stress. I’m kinda going with the more simple explanation.
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The last PC12/45 was built in 2006 IIRC. Not a “new” plane, but they are built like a brick ****house. The last person to make a PC12 fall apart was doing a hair over 120 knots past Vne, and then gave the control column a good firm tug.
 
dmspilot said:
What is that based on?
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It lost one NM (6000') in a half minute = two NM/min = 120 kts.

GS readout generally showed between 180 & 240 kts, so more than three and less than four NM/min horizontal. If it was 3.5, it's 30° (sin law). Just as a reference, had GS been 120 kts, it would be a 45° descent, so less. But just crude figuring on my part — don't anybody hold me to it. :) I'm very skeptical the pilot "lost it" without some major malfunction, like an avionics failure in IMC or a door or wing tip flapping in the breeze. Maybe he hit a Canada Goose? Had a friend catch one in his tip tank on a C-310 right on the point. It turned it inside out. Could have ripped it off, imo. Lucky it didn't hit the windshield.

PC12 crash.jpg
 
Seems on the surface to be very similar to another PC-12 accident, in Florida I believe. Turbulence caused the autopilot to disengage. The pilot got disoriented while trying to figure out what was going on. Aircraft banks over and begins a graveyard spiral. Pilot in a panic pulls on the tail removal lever, aka the yoke, and that's all she wrote. Things happen quick in a turbine airplane, you can't afford to fall behind the aircraft.
 
midwestpa24 said:
Seems on the surface to be very similar to another PC-12 accident, in Florida I believe. Turbulence caused the autopilot to disengage. The pilot got disoriented while trying to figure out what was going on. Aircraft banks over and begins a graveyard spiral. Pilot in a panic pulls on the tail removal lever, aka the yoke, and that's all she wrote. Things happen quick in a turbine airplane, you can't afford to fall behind the aircraft.
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The discussion on reddit seemed indicate that the autopilot on the PC12 doesn't like turbulence, and will disconnect easily. I'm thinking either the pilot missed the disconnection warning or was already handflying and got disoriented. Of course, some kind of instrument or other equipment failure could also be at play...or a goose...but sometimes a graveyard spiral is just a graveyard spiral.
 
dtuuri said:
It lost one NM (6000') in a half minute = two NM/min = 120 kts.
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So that's the average over the entire event. I believe you miss a lot of detail when you do that. The ~10-second slices I posted above seem more enlightening.
 
dmspilot said:
The discussion on reddit seemed indicate that the autopilot on the PC12 doesn't like turbulence, and will disconnect easily. I'm thinking either the pilot missed the disconnection warning or was already handflying and got disoriented. Of course, some kind of instrument or other equipment failure could also be at play...or a goose...but sometimes a graveyard spiral is just a graveyard spiral.
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The legacy PC12 ottopilot will click off if a raccoon farts in the next county over.
 
Pretty amazing that an aircraft this expensive does not have an LVL button like Cirrus that will restore straight and level flight regardless of whether autopilot is On or OFF.

"... Cirrus required an autopilot controller that introduces a "LVL" or Level button to help address spatial disorientation.

Everyone gets confused occasionally in the air (those that have and those that will?) and the history of aviation is rife with accidents caused by disorientation. Urban lore suggests a common expression in modern automated airliners is, "What's it doing now?"

Press the LVL button - doesn't matter if the autopilot is already on or not - and the plane will roll level and hold altitude. If the world doesn't get better quickly Cirrus still offers CAPS, the parachute."

This reads eerily like what probably happened here.
 
Himayeti said:
…"... Cirrus required an autopilot controller that introduces a "LVL" or Level button to help address spatial disorientation…
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The blue button is no magic button. IIRC, it’s a crapshoot beyond 30* of pitch or 75* angle of bank…

From the AFCS AFM:

The LVL button engages the Autopilot (within the Autopilot Engagement Limits if not already engaged) and commands roll to zero bank angle and pitch to zero vertical speed. The LVL button will not engage, or will disengage, if the Stall Warning System is activated.
 
I'll toss this out as a goofy idea - one of the last US airline accidents was related to icing. I believe one of the recommendations or notes from that was to not fly on autopilot when you have icing. So perhaps hand flying on purpose, because ice, and then ran into loss of SA? No idea if that's a valid series of events.
 
12881_3.jpg
So what I gather some are saying here is that the Cirrus LVL button is as useful as this?
 
By the time that B-Roll was produced, the airframe had already been extensively cut up, presumably under NTSB supervision. The final descent rate must have been off the charts, even though it was probably in a flat spin.
 
Here's a discussion of various possible causes of the crash:

 
Albany Tom said:
I'll toss this out as a goofy idea - one of the last US airline accidents was related to icing. I believe one of the recommendations or notes from that was to not fly on autopilot when you have icing. So perhaps hand flying on purpose, because ice, and then ran into loss of SA? No idea if that's a valid series of events.
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Nothing goofy about this. Yes, autopilots can mask icing issues, so hand flying is a good way to keep tabs on how the aircraft is actually handling. Or, if flying with autopilot and it kicks off due to trimming or control force issues (in icing conditions or turbulence) or instrument failures and the pilot is caught off guard, things can go bad fast.
 
Capngrog said:
By the time that B-Roll was produced, the airframe had already been extensively cut up, presumably under NTSB supervision. The final descent rate must have been off the charts, even though it was probably in a flat spin.
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Honestly though compared to let's say USAir 427 that airframe is relatively intact for a breakup, spiral, and slam into the Earth.
 
Todd82 said:
Honestly though compared to let's say USAir 427 that airframe is relatively intact for a breakup, spiral, and slam into the Earth.
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USAir did not break up in flight.
 
dmspilot said:
USAir did not break up in flight.
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That's what I'm getting at. This one even had a breakup and hit far "softer" than 427. It couldn't have been a straight in lawn dart.
 
Todd 82;

You are correct. This was not, in my opinion, a "lawn dart" impact, but an impact from a flat spin. Again, in my opinion, an in flight breakup due to exceeding Vne, resulted in a flat spin, which usually results in a "softer" (less destructive) impact. Note here that even though I have experience in the investigation of aircraft accidents, my opinion could be as wrong as snow in July (in the northern hemisphere). It's just too early to tell what the causal FACTORS were in this accident.

Some folks believe this forum is too heavily based on speculative posts; however, speculation or otherwise, it gets us thinking about the cause of an accident and how we,as individuals, could avoid duplicating the circumstances leading to the accident. The official "word" on an accident (the NTSB report) can be a year or more before it is released.
 
This is a photo of a PC-12 that crashed in Florida in June 2012. The instrument rated pilot literally had zero turboprop time when he purchased it weeks earlier, and hadn't flown in simulated or actual IMC in years.

The autopilot kicked off while the plane was at altitude in IMC, and it wasn't long before the plane broke up, killing the pilot and his family.

Compare the photo to that of the subject aircraft below it. Look familiar?


ghows-LK-e4f5a259-4a0b-4011-99bb-61da54762276-2601b5c3.jpeg


124973-screen_shot_2023-02-25_at_10.30.04_am.png
 
Salty said:
It seems to me you are implying that two pilots is the antidote.
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Two pilots solve a lot of things as long as both are proficient with CRM and the PIC is clear. But I don't think it should be required.
 
Capngrog said:
This was not, in my opinion, a "lawn dart" impact, but an impact from a flat spin.
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Then the plane didn't make one big turn as it descended, but instead came down spinning like a maple seed while traveling a 360° arc to the right?
 
hindsight2020 said:
Not on POA. Occam is persona non grata around these parts. :D
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Yeah, but Occam also has a funny way of disappearing for a lot of these.

Ol' Mr. Occam was jumping up and down screaming "fuel contamination" in this one:

https://www.pilotsofamerica.com/community/threads/v-twin-down-janesville.130835/page-3#post-3373510

Occam would have never said "broken oil pressure wire causes pilots to shut down a good engine, and then ALSO have the misfortune of the gear door blowing off and hitting the remaining running engine, thereby failing that one as well."
 
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