Light aircraft down near McKinlay, Qld
Join Date: Apr 2010
Location: AU
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Recording equipment
My first thoughts were pressurization with the altitude involved. The speed seems to indicate that perhaps there was quite a bit of headwind at 280 giving them a GS of around 220kts, then descent to 150 and they were making 250kts, possibly indicating less headwind. The track also looks like it made a slight right turn at one point and is missing Isa by some distance, which further lends to possible pressurization issues. The final part looks like possibly power loss, windmilling prop would slow it down fast at that level, left engine, slows, stall warning disconnects autopilot and it rolls and descends to the left, which is the path it would follow if the crew were not in a position to control it. I'm not familiar with the 695A but if it has multiple tanks it could have run one dry by then if the pilot was unconscious. In any case it's another bad day for GA. Does the 695A have recording equipment? if so that might be the only real clue to what has happened.
Never flown a 690 but could it have been an engine issue so pilot brings aircraft back to single engine safety speed (blue line). For some reason he loses control and aircraft stalls and enters a spin from which it never recovers? Would that be a possibilty for the aircraft losing 100kt ground speed in 2 minutes?
Would the aircraft have had an aural cabin altitude warning?
KR Av. Do those “students “ that are training in PNG get taught valley flying and techniques to escape.
A friend of mine and another acquaintance both met their demise out of the step turn having ‘dry gulched’ themselves in valleys with lids on. Trouble is all those jungle clad valleys in PNG look the same.
Thread. RIP the 695 three. Another mystery to be solved.
A friend of mine and another acquaintance both met their demise out of the step turn having ‘dry gulched’ themselves in valleys with lids on. Trouble is all those jungle clad valleys in PNG look the same.
Thread. RIP the 695 three. Another mystery to be solved.
I probably spend too much time thinking about these things as I pole around in 1970s twins with 30,000 hours.
"It would be easy to omit resetting the cabin Alt following the intermediate descent to FL150."
I've never flown this type, but if it's like most other pressurised turboprop aircraft, FL150 would be close to a sea level cabin at around max differential pressure, so even if the pressurisation controls weren't touched, the cabin should not have got higher than say 13000 to 15000ft on the subsequent climb, which gives a time of useful consciousness of > 30 mins, which means a failure to reset the pressurisation controls shouldn't be a relevant factor on its own. Just my 2 lire's worth...
A very nasty accident for sure & hopefully there'll be enough information to determine the cause & provide a report in about 10 years time... RIP to crew & condolences to friends & family.
I've never flown this type, but if it's like most other pressurised turboprop aircraft, FL150 would be close to a sea level cabin at around max differential pressure, so even if the pressurisation controls weren't touched, the cabin should not have got higher than say 13000 to 15000ft on the subsequent climb, which gives a time of useful consciousness of > 30 mins, which means a failure to reset the pressurisation controls shouldn't be a relevant factor on its own. Just my 2 lire's worth...
A very nasty accident for sure & hopefully there'll be enough information to determine the cause & provide a report in about 10 years time... RIP to crew & condolences to friends & family.
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Obviously the new CASA rules haven’t done anything to improve safety.
If CASA decided to proactively engage with industry and provide good clear advice, opposed to convoluted and difficult to interpret requirements, industry would be able to focus more on their day to day operations opposed to playing ping pong with CASA inspectors over trivial rubbish.
With regards to the cause of this accident, who knows however it’s pretty obvious that the pilot experienced some kind of upset at FL280 and lost control. Structural, pressurisation or engine related who knows just yet.
It would be interesting to know what the airspeed margin in between the normal cruise IAS and VMCA is at FL280 for the aeroplane. If it’s critical, it would be interesting to know if simulated engine failures are demonstrated and practiced during initial training on the aircraft type at high altitudes.
If CASA decided to proactively engage with industry and provide good clear advice, opposed to convoluted and difficult to interpret requirements, industry would be able to focus more on their day to day operations opposed to playing ping pong with CASA inspectors over trivial rubbish.
With regards to the cause of this accident, who knows however it’s pretty obvious that the pilot experienced some kind of upset at FL280 and lost control. Structural, pressurisation or engine related who knows just yet.
It would be interesting to know what the airspeed margin in between the normal cruise IAS and VMCA is at FL280 for the aeroplane. If it’s critical, it would be interesting to know if simulated engine failures are demonstrated and practiced during initial training on the aircraft type at high altitudes.
With respect to the first descent, you’d think there would be some communication with ATC. I’m guessing ATC would have picked up the descent and at least a “Confirm ops normal” call was made.
If it was a normal descent to try to find a better ground speed etc, there would be a communication trail.
If it was a normal descent to try to find a better ground speed etc, there would be a communication trail.
Why am I feeling like this is a training exercise that has gone wrong.
An engine out at FL280 will require a cruise descent, first action, it's well above single engine service ceiling. The sequence is consistent with Vmca stall.
An engine out at FL280 will require a cruise descent, first action, it's well above single engine service ceiling. The sequence is consistent with Vmca stall.
Does anyone know if JO was the pilot?
Cedric, thanks for the advice.
Considering they had more than enough time to react and initiate the descent it lends even more weight to the idea the pilot was not in a state to be able to handle it. Even if they did mishandle the initial failure and slowed to stall, you would think the pilot would have been able to recover if they were conscious, they had more than enough altitude to have several goes at recovery. Considering that if it was engine failure, at 28,000 feet all you have to do to recover from the yaw/roll excursion is to close the power lever on the live engine and fly straight in a descent. The ADSB data suggests it just slowed straight ahead on autopilot, as it was all straight and level until the speed was minimal, then it turned to the left and descended. I would think that given how the airspeed decayed over time, in straight and level flight, it does not fit with a structural failure. And if you knew a wing was falling off or failing and were slowing for whatever reason I'm sure they would have issued a mayday. I find it hard to move away from the idea it was pressurisation related. The last point of communication will be telling on what may have happened. Again I have no experience with AC 695(A) or it's pressurisation system, is it possible that the descent to FL 150 somehow put the pressurization in a descent mode and then the climb back to FL 280 it was not put back in a mode to accommodate for the climb back up.
Seems plausible. Would also explain the slight track deviation without correction. Would be interesting to know if ATC heard anything from them after being cleared back to the upper level.
Vmca unlikely to be an issue at FL280. The engines would only be developing a fraction of their sea level rated HP up there.
Was the aircraft in one piece at time of impact?
Was the aircraft in one piece at time of impact?
Considering they had more than enough time to react and initiate the descent it lends even more weight to the idea the pilot was not in a state to be able to handle it. Even if they did mishandle the initial failure and slowed to stall, you would think the pilot would have been able to recover if they were conscious, they had more than enough altitude to have several goes at recovery. Considering that if it was engine failure, at 28,000 feet all you have to do to recover from the yaw/roll excursion is to close the power lever on the live engine and fly straight in a descent. The ADSB data suggests it just slowed straight ahead on autopilot, as it was all straight and level until the speed was minimal, then it turned to the left and descended. I would think that given how the airspeed decayed over time, in straight and level flight, it does not fit with a structural failure. And if you knew a wing was falling off or failing and were slowing for whatever reason I'm sure they would have issued a mayday. I find it hard to move away from the idea it was pressurisation related. The last point of communication will be telling on what may have happened. Again I have no experience with AC 695(A) or it's pressurisation system, is it possible that the descent to FL 150 somehow put the pressurization in a descent mode and then the climb back to FL 280 it was not put back in a mode to accommodate for the climb back up.
remember the Paine Stewart Lear 35 accident