I can't make sense of this crash

MassPilot

MassPilot

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MassPilot said:
I'm having trouble understanding how a C172 had an in-flight breakup like this in visual conditions.
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From the report:

"Witnesses reported that the airplane was in a steep dive toward terrain and then they subsequently observed the wings departing the airplane at the same time."

Sounds like a simple Vne violation.
 
That steep dive report is bizarre.. a 172 will actively fight you as you start approaching 140 IAS and past. It naturally wants to pitch up at those speeds requiring a lot of nose down force.. unless you are actively pushing on that yoke it's hard to imagine that you could get the thing that far beyond Vne to tear off the wings

Isn't Vne based on 90% of Vd? They reach Vd during testing, it has to do with flutter, and is technically the maximum "never ever fly past this speed or the wings come off" The 90% Vne speed is a flutter margin.. this would suggest that for a 172 you would need to fly at a minimum of 178 knots to pull the wings off. I can't imagine making that plane do that. wow
 
Tantalum said:
True. But how did they get into a situation to pull the wings off a 172? Yikes
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People get (overly) aggressive on pull outs from dives.

Especially dives they don’t expect, like the resulting dive after recovery from a spin, and low so the window is full of ground.

Panic at the disco. “Nose is down and I’m scared... puuuuuuullll hasaaaard...” and some aluminum plays pop goes the weasel.

The other “typical” way is just horsing the airplane around doing stuff it wasn’t designed for.
 
Tantalum said:
That steep dive report is bizarre.. a 172 will actively fight you as you start approaching 140 IAS and past. It naturally wants to pitch up at those speeds requiring a lot of nose down force.. unless you are actively pushing on that yoke it's hard to imagine that you could get the thing that far beyond Vne to tear off the wings

Isn't Vne based on 90% of Vd? They reach Vd during testing, it has to do with flutter, and is technically the maximum "never ever fly past this speed or the wings come off" The 90% Vne speed is a flutter margin.. this would suggest that for a 172 you would need to fly at a minimum of 178 knots to pull the wings off. I can't imagine making that plane do that. wow
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Slow down professor. We're conflating aeroelastic terms here. Divergence speed is dynamic pressure dependent, ergo V-speed. Solving the differential equation for torsional rigidity = 0 will yield a single and real value of free-stream velocity.

Flutter otoh is not. Flutter is an aeroelastic effect that is affected by the dampening of the system (thus a realm of system dynamics, not statics). In this case the air, which is of variable density (most dramatically as a function of altitude). As such, it is a true airspeed dependent criteria. Therefore it [flutter] occurs through a range of dynamic pressures (aka indicated airspeeds) as a function of altitude and cannot be placarded accurately without an altitude compensating barber pole airspeed indicator.

Lastly, diverenge and flutter are different phenomena, though they are both aeroelastic in nature. Vne usually encompasses the earliest occurring of the structurally compromising effects. These can be aeroelastic or non-aeroelastic. In small spam cans it's usually simple ultimate overload when gust is accounted for. But it can be aeroelastic in nature, as I'm sure folks have seen the video of the comanche with the wobble tail.

Thanks for the trip down graduate school memory lane!
 
Can’t comprehend how an instructor,could let a 172 get into a situation,that could pull the wings off.
 
denverpilot said:
The other “typical” way is just horsing the airplane around doing stuff it wasn’t designed for.
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I thought that only happens in Archers. Jk. I'll duck and cover now

hindsight2020 said:
Thanks for the trip down graduate school memory lane!
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Anytime! I come from a family of engineers.. I'm the one who went to computers
 
Gravity always wins in the end. One thing for certain, absent convective activity the pilot really screwed the pooch. Sorry if it offends, but Skyhawks are stout things.
 
hindsight2020 said:
Slow down professor. We're conflating aeroelastic terms here. Divergence speed is dynamic pressure dependent, ergo V-speed. Solving the differential equation for torsional rigidity = 0 will yield a single and real value of free-stream velocity.

Flutter otoh is not. Flutter is an aeroelastic effect that is affected by the dampening of the system (thus a realm of system dynamics, not statics). In this case the air, which is of variable density (most dramatically as a function of altitude). As such, it is a true airspeed dependent criteria. Therefore it [flutter] occurs through a range of dynamic pressures (aka indicated airspeeds) as a function of altitude and cannot be placarded accurately without an altitude compensating barber pole airspeed indicator.

Lastly, diverenge and flutter are different phenomena, though they are both aeroelastic in nature. Vne usually encompasses the earliest occurring of the structurally compromising effects. These can be aeroelastic or non-aeroelastic. In small spam cans it's usually simple ultimate overload when gust is accounted for. But it can be aeroelastic in nature, as I'm sure folks have seen the video of the comanche with the wobble tail.

Thanks for the trip down graduate school memory lane!
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Dafuq did he just say? o_O
 
timwinters said:
From the report:

"Witnesses reported that the airplane was in a steep dive toward terrain and then they subsequently observed the wings departing the airplane at the same time."

Sounds like a simple Vne violation.
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My guess is they were pulling out of an intentional spin, in an airplane that was already compromised (corrosion, prior maneuvering speed violations).
 
sarangan said:
My guess is they were pulling out of an intentional spin, in an airplane that was already compromised (corrosion, prior maneuvering speed violations).
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First time at the controls for the student pilot. They weren’t doing anything more than heading and altitude changes. Or shouldn’t have been.

I hope someone catches the full write-up. Some sort of control system failure? Student lock-up? I imagine it’s really difficult to literally fly the wings off of a mechanically sound 172, in good VFR conditions.
 
Total speculation: the student was climbing to an assigned altitude, possibly in a turn, and inadvertently stalled, panicked and wouldn’t release the controls.

That’s about the only scenario where I could see this happening outside of a control system failure or suicide.

What’s the plausibility on that? It’s late and I’m bored. I really hope to see the case study on this. OP is right, it’s a strange one. A 172 will fight to keep you alive. This is .... bizarre.
 
1RTK1 said:
If so, why would a CFI allow that to take place???
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I ended with dives like that because we were doing upset recovery under the hood. My 1st step was to normalize AI and T&B. By the time I got it under control, the airplane was typically diving into yellow arc even with throttle cut. Then I pulled out gingerly and yes, speed was alarming. Good thing I was under the hood, so I didn't know how much ground was in the windscreen.
 
Clip4 said:
Structural failure not a result of maneuvers on that flight.
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I remember reading years ago that there has never been a C172 structural failure when flown within airspeed and G limits. I'm not sure if this is true or just an urban legend.
 
MassPilot said:
I remember reading years ago that there has never been a C172 structural failure when flown within airspeed and G limits. I'm not sure if this is true or just an urban legend.
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I would wager that should be true for most airplanes. As long as an aircraft is always kept within its flight envelope, and is properly maintained, there should not be much chance of a structural failure.
 
woodchucker said:
Total speculation: the student was climbing to an assigned altitude, possibly in a turn, and inadvertently stalled, panicked and wouldn’t release the controls.

That’s about the only scenario where I could see this happening outside of a control system failure or suicide.

What’s the plausibility on that? It’s late and I’m bored. I really hope to see the case study on this. OP is right, it’s a strange one. A 172 will fight to keep you alive. This is .... bizarre.
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172 is hard to spin, and hard to maintain the spin. You need to have full yoke back, and full left rudder (hard to spin to the right), and also maintain power to make it spin. I suppose it is possible for a student to freeze on all three of those controls, but not very likely.
 
In my professional opinion it sounds like badness.
172’s love to fly. And fight against anything else really.
Is spin training part of a ppl?? I never did that and while was curious if it was an omission or just not required. While it sounds like it’s important on how to get out of a spin, I like to think it’s more important to not get into one!!
 
benyflyguy said:
In my professional opinion it sounds like badness.
172’s love to fly. And fight against anything else really.
Is spin training part of a ppl?? I never did that and while was curious if it was an omission or just not required. While it sounds like it’s important on how to get out of a spin, I like to think it’s more important to not get into one!!
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Spin training isn't required for anything but the CFI rating. It used to be required but the FAA decided it wasn't worth the risk. It's also horrible for the gyro instruments in the airplane. The newer G1000 C172's aren't even spin certified.
 
The R and S models are outside the utility category even with the rear seat unoccupied. The heavier empty weight and the massive rear seat structure do that. There were three on board, making it even farther out of utility, so any intentional spin would be foolhardy indeed, and I know Moody is a very good, FAA-compliant school that woud not sanction anything like that. I'd consider a spin unlikely.
 
MassPilot said:
The newer G1000 C172's aren't even spin certified.
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Yes they are. We had one and spun it, but the rear seat had to be out of it to get it into utility category.
 
Buzzing? At one point the ntsb notes some 3000’ and change (wasn’t very clear to me), but if buzzing that would be consistent with a dive and subsequent wings departing from the fuselage
 
sarangan said:
My guess is they were pulling out of an intentional spin, in an airplane that was already compromised (corrosion, prior maneuvering speed violations).
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With due apologies for sidelining the conversation, I have a question regarding @sarangan 's observation.

As renters, how do we know that the airplanes we are flying are not compromised by corrosion, prior Va violations, etc? These failures may be discovered during annual inspections, but this may be too long. Can they be caught during the 100-hour inspection?
 
Dan Thomas said:
The R and S models are outside the utility category even with the rear seat unoccupied. The heavier empty weight and the massive rear seat structure do that. There were three on board, making it even farther out of utility, so any intentional spin would be foolhardy indeed, and I know Moody is a very good, FAA-compliant school that woud not sanction anything like that. I'd consider a spin unlikely.
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Thanks for posting that info. I was wondering about that but was feeling too lazy to research.
 
GreatLakesFlying said:
With due apologies for sidelining the conversation, I have a question regarding @sarangan 's observation.

As renters, how do we know that the airplanes we are flying are not compromised by corrosion, prior Va violations, etc? These failures may be discovered during annual inspections, but this may be too long. Can they be caught during the 100-hour inspection?
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Regulatory wise, what is the difference between an annual and a 100 hr?
 
GreatLakesFlying said:
With due apologies for sidelining the conversation, I have a question regarding @sarangan 's observation.

As renters, how do we know that the airplanes we are flying are not compromised by corrosion, prior Va violations, etc? These failures may be discovered during annual inspections, but this may be too long. Can they be caught during the 100-hour inspection?
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I grab each wing and move it up and down looking for play, not sure what else you can do with a rental except look for obvious signs of corrosion.
 
It would be interesting to know if the airplane had its wings removed for any reason in the past, like say, an off field landing. May be it wasn't put back together properly.
 
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