Light aircraft down near McKinlay, Qld
Xeptu:
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No, PiperCameron that is incorrect. The altitude in the ADS-B message is *always* in reference to 1013.25 hPa. And the reason is exactly as you state: A falsely set QNH on the altimeter would then report the wrong altitude. This way, ALL aircraft are reporting to the same pressure level.
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We are a long way from knowing if structural failure is involved here, but smooth air doesn't rule anything out. A structure on the brink of failure is just that - a structure on the brink of failure. An aircraft in flight is sustaining loads greater than "static" when it's sitting on the ground. If the structure has been compromised, it will eventually fail under "normal" flight loads. The only thing turbulence will do is speed up the process.
Agreed JO. Old higher time airframe, cumulative fatigue + previous over stressing.
Have the other two crew names been released anywhere?
Have the other two crew names been released anywhere?
We are a long way from knowing if structural failure is involved here, but smooth air doesn't rule anything out. A structure on the brink of failure is just that - a structure on the brink of failure. An aircraft in flight is sustaining loads greater than "static" when it's sitting on the ground. If the structure has been compromised, it will eventually fail under "normal" flight loads. The only thing turbulence will do is speed up the process.
I also don't really believe an experienced pilot would not note an engine failure and let it get to stall, in a training exercise even less likely. I assume multiple bells and whistles would be sounding at various times, being a turbine powerplant. There was also at least one other aviation professional on board in the case of the engineer, who would have had some clue of what was going on had an engine stopped.
Things will fall off just sitting on the ground due to corrosion and other factors over time. However an in-service aircraft of this age will have no doubt been subject to regular inspections and NDT of the critical parts of the airframe for cracking, corrosion and anything else that will lead to break up. Previous accidents involving the type would have generated ADs for the parts most susceptible to these failures, so a failure in straight and level flight at cruise speed even in moderate turbulence is very unlikely if the aircraft was properly maintained. And once again, the ADSB data points to a gradual slow down to close to stall speed, under control, in straight and level flight, very unusual if it was a wing falling off. Excursion from cruise flight only seems to occur once minimum speed is reached and the aircraft then departs into a left spiral. This is shown in a trend in the data, not single points, so it's doubtful the ADSB plots are all in error, as all the plots prior seem relatively accurate and the departure coincides with the loss of contact with the aircraft.
I also don't really believe an experienced pilot would not note an engine failure and let it get to stall, in a training exercise even less likely. I assume multiple bells and whistles would be sounding at various times, being a turbine powerplant. There was also at least one other aviation professional on board in the case of the engineer, who would have had some clue of what was going on had an engine stopped.
I also don't really believe an experienced pilot would not note an engine failure and let it get to stall, in a training exercise even less likely. I assume multiple bells and whistles would be sounding at various times, being a turbine powerplant. There was also at least one other aviation professional on board in the case of the engineer, who would have had some clue of what was going on had an engine stopped.
FWIW, I have seen far too much inaccuracy in publicly available data to feel comfortable reaching any conclusions. If I had a dollar for every piece of bad data I've seen over my years in flight safety, I would no longer need to be working. As for how an in-service aircraft might have been maintained and inspected, that too is for the investigators to determine. I hope you are correct and that no surprises are found in the airframe. I work for an operator of a different variant of this aircraft and while I know we put a ton of time into keeping our aircraft in excellent condition, this one has surely gained our attention.
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I also don't really believe an experienced pilot would not note an engine failure and let it get to stall, in a training exercise even less likely. I assume multiple bells and whistles would be sounding at various times, being a turbine powerplant. There was also at least one other aviation professional on board in the case of the engineer, who would have had some clue of what was going on had an engine stopped.
In the case of partial failure, disbelief and uncertainty still reigns supreme. the old tapping on the torque gauge still goes on. We are trained to fly on two engines or one engine, not one and a half engines. If there is any doubt, get rid of it.
The C441 (same engines) in Renmark stalled and crashed during a training exercise with 3 professionals on board just the same.
Last edited by Xeptu; 9th Nov 2023 at 22:12.
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From the ATSB report.
The ATSB also considered the potential that the loss of control was the result of an aerodynamic stall. However, given that the final recorded indicated airspeed was about 20 kt higher than the aircraft's stall speed that was considered unlikely.
Some of the possibilities raised in this thread have the potential to be the cause of the accident but hopefully the investigation is effective at discovering the actual cause.
If just one person takes something away from the speculation that gives them food for though about how they may handle a certain situation, then surely it's a win? Even if the speculation is plain wrong relating to this accident, it might have benefit generally.
It'd be great if people could have a little more humility and keep an open mind. All the best operators I've met have that quality and Im not sure anyone could be sure about this one yet..
Ive been on these threads when the deceased has been someone I know, and I really had to limit the exposure for a bit. But that was on me and my sensitivity at the time - not the discussion. It is after all a RUMOUR network
Condolences to all involved.
If just one person takes something away from the speculation that gives them food for though about how they may handle a certain situation, then surely it's a win? Even if the speculation is plain wrong relating to this accident, it might have benefit generally.
It'd be great if people could have a little more humility and keep an open mind. All the best operators I've met have that quality and Im not sure anyone could be sure about this one yet..
Ive been on these threads when the deceased has been someone I know, and I really had to limit the exposure for a bit. But that was on me and my sensitivity at the time - not the discussion. It is after all a RUMOUR network
Condolences to all involved.
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It may be the same as Vs - which is a function of angle of attack. It may be higher or lower - that's a coincidence of a number of factors. Granted to have a Vmca event you need to be above Vs otherwise you will have an asymmetric stall event first which are equally unpleasant.
The dreaded Vmca rollover of which we've sadly seen many, is not due to an aerodynamic stall. It may be present, but not necessarily. The inner wing may still be generating lift, and likely so in the Renmark crash where Vs was 20kt lower. The Darwin Bras had the stall warning sounding off and on before it went over (but was still probably not fully stalled).
Last edited by compressor stall; 10th Nov 2023 at 03:19.
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From memory, VMCA of the C441 is 91 KIAS. However a lesson that has still not been learned after many years is that Check Pilots/Instructors should NOT retard the power lever to Flight Idle when simulating engine failures. The power lever should be set to zero thrust because these & similar performance turbo prop aircraft have NTS or Auto-Feather systems fitted to reduce drag from a windmilling propeller. I only mention this because the C441 was impossible to control any where near 91KIAS if the power lever was retarded to flight idle resulting in a VMCA departure from controlled flight at a significantly higher IAS than 91kts (more likely around 15-20 kts higher with max power on the live engine).
I only mention this because these accidents continue to happen. For what it's worth, I concur with compressor stall in that an aerodynamic stall is not always related to VMCA …
Just my 2 lire’s worth…
I only mention this because these accidents continue to happen. For what it's worth, I concur with compressor stall in that an aerodynamic stall is not always related to VMCA …
Just my 2 lire’s worth…
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Just don't do it, particularly with these engine types, your putting an awful lot of faith in a bit of oil pressure without sufficient rudder authority.
If you want to see a real one caught on camera, google "queenair stall and crash"
If you want to see a real one caught on camera, google "queenair stall and crash"
ADS-B data can tell you a lot. But you have to understand what it represents and through whose hands it went before you got a hold of it. Specifically:
a) what has been done to the data since it came from the aircraft
b) what sensor input is fed into the ADS-B output
For a), all public data sources I'm aware of are adulterating the data in some form or another. They either interpolate data between known positions/altitudes/speeds, and lead you to believe that those points in-between are true, when in fact they are estimated. FR24 is particularly guilty of that to create a smooth web browser flight tracking experience. Their internal data resolution is 5 seconds, but on the website, the positions update a couple of times per second. That means 20 positions you're following as "real" are educated guesses. Now you know.
a) what has been done to the data since it came from the aircraft
b) what sensor input is fed into the ADS-B output
For a), all public data sources I'm aware of are adulterating the data in some form or another. They either interpolate data between known positions/altitudes/speeds, and lead you to believe that those points in-between are true, when in fact they are estimated. FR24 is particularly guilty of that to create a smooth web browser flight tracking experience. Their internal data resolution is 5 seconds, but on the website, the positions update a couple of times per second. That means 20 positions you're following as "real" are educated guesses. Now you know.
Relevantly to (a), and as I've posted elsewhere on this site, I once inspected the code used by adsbexchange to provide its experience; at that time there was a fair degree of interpolation/interpretation of the raw data. To be fair this is probably necessary to produce something that provides a sensible looking output most of the time, however it should certainly not be relied upon for any serious forensic examination.
I also commend the other points raised re the originating data and associated issues with that. Well said.
FP.
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The ATSB also considered the potential that the loss of control was the result of an aerodynamic stall. However, given that the final recorded indicated airspeed was about 20 kt higher than the aircraft's stall speed that was considered unlikely.
A stall happens at a fixed angle of attack, not a fixed airspeed. There are variables that can affect the airspeed at which you reach that angle of attack.
Surely an aircraft accident investigator knows this?!
A stall happens at a fixed angle of attack, not a fixed airspeed. There are variables that can affect the airspeed at which you reach that angle of attack.
Surely an aircraft accident investigator knows this?!
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Just a comment to support physicus' view on this.
Relevantly to (a), and as I've posted elsewhere on this site, I once inspected the code used by adsbexchange to provide its experience; at that time there was a fair degree of interpolation/interpretation of the raw data. To be fair this is probably necessary to produce something that provides a sensible looking output most of the time, however it should certainly not be relied upon for any serious forensic examination.
I also commend the other points raised re the originating data and associated issues with that. Well said.
FP.
Relevantly to (a), and as I've posted elsewhere on this site, I once inspected the code used by adsbexchange to provide its experience; at that time there was a fair degree of interpolation/interpretation of the raw data. To be fair this is probably necessary to produce something that provides a sensible looking output most of the time, however it should certainly not be relied upon for any serious forensic examination.
I also commend the other points raised re the originating data and associated issues with that. Well said.
FP.
As far as my comment regarding an experienced pilot getting it wrong, I was referring to the failure being at altitude and at cruise speed. Not low altitude asymmetric training. Turbine aircraft tend to have all sorts of warnings go off when you have a failure.