Oops, darn it...

Yes^^^but as noted (via speculation; my words) in the NTSB's Final Report ANC17FA009:

"According to the manufacturer of the VGs, the airplane's expected full flap stall speed was about 33 knots, which was 7 knots higher than the speed at which the loss of control event occurred. Based on the GPS data, the airplane reached 33 knots about 30 seconds before the loss of control and likely entered a stalled condition at that time; however, the pilot apparently failed to recognize the stall and allowed the descent to continue. It is possible that the improved aileron authority at slow airspeeds, which the VG installation provided, allowed the pilot to maintain aileron control while the airplane was in a stalled condition. Further, according to the manufacturer's test data (an 8GCBC Scout BTW; my insert), the pre-modified airplane would have had a pronounced wing drop at the onset of stall. The stall characteristics of the modified airplane likely
contributed to the pilot's failure to recognize that the airplane was stalled."

First, no two aircraft perform identically. To assume so takes a great leap into the unknown which is why a test is recommended. The pilot might have had enough experience in that aircraft to note a difference pre and post VG, but maybe not. Second, any wind at altitude would have affected the GPS derived groundspeed versus actual airspeed. The NTSB didn't include surface wind data from the nearby Blair Lakes RAWS weather station, only airports near Fairbanks which were near calm as usual during a surface temperature inversion (~-20F). The accident occurred around 10:43 am 12/07/16. Nearby Blair Lakes surface wind (it can blow there more than Fairbanks; my words and experience) ranged from 10-16 mph ENE during that period. What the winds were at altitude or whether he was monitoring airspeed or GPS groundspeed may have affected the aircraft's performance and behavior prior to the crash is...unknown.

Gary

Appeal. But what a time and money expense to Micro Aerodynamics whose gone threw all the STC hoops. If there was a latent deficiency in this product there would be the whole equipped fleet falling out of the sky. Sheeeze

That literally makes zero sense but I would expect nothing less from a dirty lawyer. One pilot in that jury and nothing would have been awarded. Of course anyone with aviation knowledge would get dismissed from jury duty immediately.

scooter7779h said:

... If there was a latent deficiency in this product there would be the whole equipped fleet falling out of the sky....

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exactly.

I was told no pilots on the jury but can't confirm. Now a small company who's goal is to provide improved safety and margin before a stall is struck hard. Once these things happen a precedence is available for others to sue STC holders. And insurance rates may rise accordingly if equipped.

Gary

I guess I'm naïve but I can't comprehend how, absent equipment malfunction or failure, avoiding a stall near the ground isn't a pilot's responsibility. Maybe advertising could be claimed to lend to the pilot an inappropriate sense of security, but still - I hope insurance shielded Micro and that their business isn't hurt badly.

Knowing the plane and pilot I doubt he would have intentionally flown into the ground. Potentially other issues besides an STC may have been involved. Spacial disorientation, reduced visibility looking into a low Sun, incapacitation, lack of power plant response, unexpected loss of relative wind, all complicated by eventually being too low to recover from any cause. Sadly we'll never know what really occurred to create this tragedy.

Gary

Loss of control and failure to maintain a safe altitude resulting in a stall spin into terrain. Vg's can make the stall worse because you're at a higher aoa when it breaks but that doesn't change the why or where of the story. It's just punishing the spoon manufacture for making someone fat. I suspect a lot of high time pilots and commercial people have flown a long time with relatively mundane results and have lost that healthy fear. Obviously he feared nothing doing stalls that close to the ground. Complacency is a human condition we all suffer from,me included.

I have to agree with akavid. When I heard this was in the trial stage I indeed dug it up out of the database and read the final report. The altitude he was flying while doing some of the testing as reported by the NTSB from data obtained from the Garmin GPS just jumped off the page. Stupid low is indeed an accurate description, very odd to be doing any testing at those altitudes on something that can alter the handling aerodynamically that much, especially on a new install, first flight, etc. Just makes me just shake my head and wonder why. Micro Aerodynamics may need to up their explanation and instructional criteria but Mr. Kelly as PIC and as much experience as he had knew better and the family should realize that. He needs to own some of that, can’t put it all on the manufacturer.
If the handling characteristics are altered so much as to cause this problem, why haven’t thousands of aircraft been falling out of the sky with tail stalls etc prior to this from Micros product?
I maintain and fly two cubs, both stock except for the Micros and they both fly exceptionally well, save for the fact that we all are familiar with….the tendency for the tail to quit flying before the wing does. Known Cub trait, no problem because it’s a given. How do I deal with it? Slow flight practice, every year, several times, learn the airplane…again. Not something a guy is going to get on a first flight on a new install. Sorry, just not buying it. Especially not doing that practice at low altitude.

My post may be redundant at this point but just thinking “out loud” here, saying what a lot more are probably thinking.
I very much feel for the Kelly family’s loss, really good man Mike was. My loss as well, he was instrumental in helping my Dad and I get through a wilderness jam in our early years here in Alaska, stayed in touch a bit, have the utmost respect for him. Rest in Peace.

Oz




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I feel sorry for Micro if they take the hit here & have to pay out a big settlement.
They're based near me at Anacortes airport,
and from what I've seen are not a big, high-dollar outfit--
just a small business trying to provide a living for the owner & any employees.

Sounds to me that either Micro didn’t take this legal action as seriously as they may have, or didn’t employ a very aviation savvy attorney to defend themselves. Unfortunately, few of things get overturned on appeal, unless the court screwed something up in process…..appeals don’t examine facts, only process.

I hope Micro has good insurance.

MTV

Sadly, it’s often not an issue of taking a legal action seriously, but rather the lawyer you can afford is simply no competition for the lawyer the other party can afford.

And, we always think that common sense will prevail. Only to be proven wrong time and time again.


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Champs were built with flat wings - no washout unless the owner modifies. Try that configuration with others Like a Cub and see if the stall behavior changes. I have and directly went back to factory settings (Edit: For my PA-18A; I left the two Citabria wings flat plus added a Crosswinds STOL kit to the 2nd one). Like it or not when an unmodified Champ stalls it does (I owned two). Edit: The STOL kit helped my Citabria stall behavior via a milder break. Never flew one with VG's.

Gary

Lawyers don’t decide or deliver verdicts, nor do they decide whether to award damages or the amount awarded, if any. In America, a jury consisting of 12 impartial members of the local community are chosen by the attorneys for both sides to do that difficult chore.

Paul Heinrich said:

Everyone who reads posts #3243 and 3247 should dismiss as hate-speech the death-threats and libelous implication that the crash victim’s attorney was somehow better off dead; “dirty” and to blame for the outcome of the trial. BULLSHxT!!!

Even the highly educated 6th grade graduate Jethro Bodine knows that lawyers don’t decide or deliver verdicts, nor do they decide whether to award damages or the amount awarded, if any. In America, a jury consisting of 12 impartial members of the local community are chosen by the attorneys for both sides to do that difficult chore.

The posters should remember that Darwin proposes a natural and effective method for dealing with ignorance.

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im not saying your right and not saying your wrong, but im very interested in how it was ever determined that the tail stalled out, and not dozen of other things that can happen with a machine??? change my mind on, "these people have some liability insurance we can go after, so lets go for it"

Folks, let’s not devolve what can be a thread to share potential life saving thoughts into a pissing contest about the law and lawyers. Nobody has won any of those contests ever.

Back to safety discussions, please.

MTV

mvivion said:

Back to safety discussions, please.

MTV

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In that spirit I'd like to hear more about tail stalls including a description of what is felt/seen and the appropriate recovery action.

Nothing in the NTSB report suggests the tail was stalled in this fatal accident. I have flown several aircraft that "ran out of elevator" but I have never experienced a tail stall. None of the aircraft I currently own stalls the tail surfaces before the wing (PA-28, FX-3, ASW-28).

Wouldn't a tail stall result in a pitch down and a recovery to unstalled speed even if back stick was held? I imagine an unpleasant ride with a series of sharp pitch downs followed by immediate recovery. What I imagine is a "ratcheting" type pitch oscillation.

Please share some details if you have experienced a "tail stall".

Remember, stall is AOA dependent, not speed dependent.

Given a sudden pitch down with elevator remaining full up and at or beyond its critical AOA, the elevator AOA would increase even more during the down-pitch transition, thereby increasing pitch down tendency. I've never experienced that, but it sounds ugly.

I'd expect that the elevator would not stall if its max deflection were within the TCDS limits. I think - - -

Elevator holds the tail down and when it stalls the angle of attack decreases ending the stall. Manufactures often set it up that way for safety reasons. Stinson is a good example with two different elevator limits depending on the flap setting. Full flap noses the plane down and can handle more up elevator.

Hard to imagine ANY stall being a problem if the CG was in the envelope.

when it stalls the angle of attack decreases ending the stall

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No. If the tail stalls, the nose drops because the tail isn't being held down, thus the tail rises. Therefor the relative wind vector at the tail becomes more vertical (closer to normal to the tailplane surface), increasing the tail's AOA.

Typically what's available and discussed are Ice Contaminated Tailplane Stalls (ICTS). Do a search and there's quite a bit of NASA research been done plus pictures and videos explaining the phenomenon and suggested recovery techniques. A local FAA rep and I discussed this a few weeks back.

That ICTS deal was not likely the case of the 7GCBC during deep winter cold in clear air. However, I read in the newspaper that a "tail stall" was reportedly part of the plaintiff's initial filing. That was with an altered aircraft configuration - the VG's - which they claimed contributed to the accident in some manner. The NTSB Final Report in this case asserted the plane was stalled but the pilot was unaware of the degree, hence the controlled flight into terrain:

"Based on the GPS data, the airplane reached 33 knots about 30 seconds before the loss of control and likely entered a stalled condition at that time; however, the pilot apparently failed to recognize the stall and allowed the descent to continue" (estimated at 500 FPM). Was that pilot error or the inability to recover for some reason from a stall?

I can see a situation at high AOA whereby the leading edge of the airfoil behind but near the wing's VG's could maintain air flow (but somewhat turbulent) and lift while the airflow detaches further back. Weight at the CG in front of the center of lift out plays the reduced lift and the nose drops. Some aileron and tail effectiveness may remain. If the stabilizer and elevator lack sufficient downward pressure nothing will alter the descent until either wing lift or tail down load are restored. Airspeed and/or power can help. Nothing new there.

My question is did Micro during their various certification programs, or later after some experience with field installs, detect a lack of desirable elevator effectiveness with some aircraft? Recall that the under tail VG's were added after that kit was first introduced, at least for the PA-12 and 18 series. Mine installed on a PA-18A in 1993 lacked them on the under tail as well as those in front of the fuel tanks. Later in 1998 they offered a revised kit that included full span VG's plus those under the tail for my PA-12.

Gary

The ground gets closer and the airplane doesn’t respond…. VGs don’t cause that.

Yes, that - both Gary and Stewart. Thinking about Gary's remarks - - With the addition of wing devices that would increase its critical AOA, folks could be tempted to increase the elevator max up angle in order to achieve that high wing AOA. In doing so, I can imagine that the tail could exceed its critical AOA. Just thinking out loud here, and not suggesting anything about the accident airplane.

I can accept that with VG's (and LE slots or slats) the aircraft may not drop nose down as far as it would without them. Any problem with the possibility of that? So, if the pilot is used to a normal stall and resulting visual angle during a descent, the aircraft is actually stalled (wing aft only now) but in a flatter angle (LE lift retained) via the VG's. That's the reason Micro recommends the testing for STC compatibility...to convince the operator things may have changed. But...only at a safe altitude that will allow for a safe recovery, but certainly not 500-1000' AGL. The test was required; the safe recovery floor was busted for some reason.

Edit: Have a look at the Cl/AOA curve for a NACA 4412 airfoil (the Champ's). Note hoe after the lift peak is reached and the AOA increased some lift remains. The flapped wing section would stall at a lower AOA than outboard. Settling in a stall need not be nose down if there's residual lift available via added devices.

Gary

Micros don’t change the stall AOA, they change the AOA-speed relationship. Everything is the same, just a little slower. This judgement makes no sense. I doubt it was arrived at based on aerodynamics. It sounds like it was about the user instructions.

AOA and speed are independent variables. Please explain the relationship you're referring to.

stewartb said:

Micros don’t change the stall AOA, they change the AOA-speed relationship. Everything is the same, just a little slower. This judgement makes no sense. I doubt it was arrived at based on aerodynamics. It sounds like it was about the user instructions.

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Respectfully I disagree. VG's, just like slats and slots, can increase the ultimate AOA where the sufficient lift is lost and a stall occurs.

https://www.boldmethod.com/learn-to-fly/aerodynamics/vortex-generators/
https://www.nar-associates.com/technical-flying/vortex/Vgs_stall_wide_screen.pdf

Edit: Read the latter link then think about the potential behavior of the 7GCBC that crashed.

Gary

Vgs keep airflow attached to a surface. To a pilot nothing about the AOA picture changes. The only change is the speed at which that AOA occurs.

No.