Light aircraft down near McKinlay, Qld

[wheelyfunny]

have heard that while on a bushfire-related flight out of Toowoomba, Victorian-based Agair Logistics P/L Gulfstream American Corporation 695A Jetprop Commander 1000 VH-HPY as "Birddog 370", has been uncontactable and now vanished from radar between Cloncurry and Mount Isa…
UPDATES…
RFDS King Air “Flydoc445” is diverting towards Cloncurry to have a look.
Mount Isa based helicopter “Rescue 400” heading out to look.
Ground crew from Cloncurry heading out too.
ADF Cessna 208 Caravan “Waler 11” might also come down from Borroloola.

[Just a Grunt]

ABC article (https://www.abc.net.au/news/2023-11-04/light-plane-crashes-near-cloncurry/103065708)

”multiple occupants” 😢

[onehitwonder]

3 POB

[Cloudee]

From the AustralianThe Australian

“Transport Safety Bureau (ATSB) has launched an investigation.

A witness told Nine News they had seen a plume of smoke about 30km off the Landsborough Highway around the area the plane reportedly crashed.

Investigations into the incident are ongoing.

No aircraft has yet been found.

It’s understood the missing plane is 275 Gulfstream 695A Jetprop Commander 1000 known as a “Birddog”.

The plane disappeared of the flight radar between Mt Isa and Cloncurry after departing Toowoomba earlier in the day.”

VH-HPY matches the type and can be seen on FR 24 in the area at 28000 ft until it slows and descends and then disappears.

[43Inches]

Very odd last 3 minutes of recorded flight. 28,000ft, 220 kts then slows to 107 kts, turns left rapidly through about 240 deg left descending and accelerating rapidly to 25,000 then disappears off tracking. The last few months has been awful for GA.

[PoppaJo]

Very strange. Another one that has just dropped like a brick looking at the data with that rego above. Terrible.

Satellite looks clear and cell activity which was also building was over Georgetown way. Seemed well clear.

[KRviator]

What'd cause the descent from FL280 -> FL150 and climb back to 280 early in the piece? Do the firescan ops require that, or could it be indicative of a pressurisation issue?

-HPY was also the rego of the Twotter we lost in PNG when the students turned up the wrong valley and couldn't outclimb the terrain. :(

[HalfGreen]

Listening in on frequency this arvo and the aircraft in question didn't make any radio communications or respond to ATC when it first descended from FL280 and later dropped off ADSB coverage at FL247, reportedly in a steep descent. Last I heard the wreckage was spotted and based on my understanding it was one that you don't walk away from. Does anyone have any updates on the health of the pilot & pax??

[43Inches]

What'd cause the descent from FL280 -> FL150 and climb back to 280 early in the piece? Do the firescan ops require that, or could it be indicative of a pressurisation issue?

-HPY was also the rego of the Twotter we lost in PNG when the students turned up the wrong valley and couldn't outclimb the terrain. :(

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.

[Mr Mossberg]

Reports are saying 3 on board. AC69?

[Squawk7700]

Very odd last 3 minutes of recorded flight. 28,000ft, 220 kts then slows to 107 kts, turns left rapidly through about 240 deg left descending and accelerating rapidly to 25,000 then disappears off tracking. The last few months has been awful for GA.

Is that typical of an asymmetrical event? I was coincidentally reading about one of these recently that lost an engine and ended up in a spin.

[CIC]

If the aircraft was conducting fire spotting ops and was on task then the possibility of being caught in a 'firestorm' similar to a thunderstorm is a consideration.
The 690A Turbo Commanders has a very low Vma speed and structural failure in a firestorm is a possibility.
There was a B200 operated by xxx xxx at Essendon many years ago caught in a firestorm event and bent the wings. The pilot and crew was very lucky to survive.

[MickG0105]

Reporting in The Australian,
Wreckage was found about 40km northwest of McKinlay, 230km southeast of Mt Isa, around 5pm on Saturday.

Behind a paywall
https://www.theaustralian.com.au/nation/three-feared-dead-in-queensland-plane-crash/news-story/76e401a59cabb97015a13f4c32ad7f48 (https://www.theaustralian.com.au/nation/three-feared-dead-in-queensland-plane-crash/news-story/)

VH-HPY AC95 according to FR24

[lucille]

Was the aircraft in one piece at impact?

I have a vague recollection that Vb is quite low for a speedy aircraft.

[0ttoL]

ABC News
https://www.abc.net.au/news/2023-11-04/light-plane-crashes-near-cloncurry/103065708

[CIC]

The aircraft register shows HPY is a Turbo Commander 690A.

[ozbiggles]

What'd cause the descent from FL280 -> FL150 and climb back to 280 early in the piece? Do the firescan ops require that, or could it be indicative of a pressurisation issue?

-HPY was also the rego of the Twotter we lost in PNG when the students turned up the wrong valley and couldn't outclimb the terrain. :(

Students? Where was the instructor?

[CIC]

The Twin Otter was being flown in PNG.
The aircraft was on lease to the Australian Army
The instructor was in the cabin

[john_tullamarine]

Three similar threads merged.

[Horatio Leafblower]

A friend of mine was killed in a GAM Aerocommander at Killmore Gap when the wings clapped.
I can't help but wonder how much low level FAC/Bird-Doggin' this machine has done.
How very sad for the friends and families. So sad.

[C206driver]

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.

If by recording equipment you mean Flight Data Recorder (FDR)? This aircraft’s MTOW was 5080KG so not required as far I am aware

[PoppaJo]

What'd cause the descent from FL280 -> FL150 and climb back to 280 early in the piece? Do the firescan ops require that, or could it be indicative of a pressurisation issue?

Seems like having a look en route at the Carnarvon gorge fires.

[compressor stall]

A friend of mine was killed in a GAM Aerocommander at Killmore Gap when the wings clapped.
I can't help but wonder how much low level FAC/Bird-Doggin' this machine has done.
How very sad for the friends and families. So sad.
It may have done so, but - with the usual caveats of ADSB data - in instance it looks like they were trucking along in the cruise at FL280 then lost 100kt over 2 mins pretty much level, then turned sharply left into an increasing speed descending turn.

[reefrat]

Google mentions several wing spar failures

[Alice Kiwican]

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?

[roundsounds]

What'd cause the descent from FL280 -> FL150 and climb back to 280 early in the piece? Do the firescan ops require that, or could it be indicative of a pressurisation issue?

It would be easy to omit resetting the cabin Alt following the intermediate descent to FL150.

[Cilba]

Would the aircraft have had an aural cabin altitude warning?

[aroa]

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.

[Horatio Leafblower]

It may have done so, but - with the usual caveats of ADSB data - in instance it looks like they were trucking along in the cruise at FL280 then lost 100kt over 2 mins pretty much level, then turned sharply left into an increasing speed descending turn.
Ja ja ja but you and I both know fatigue is cumulative. It's less about what the aircraft was doing today as what it has been doing for the last 20 years.
I probably spend too much time thinking about these things as I pole around in 1970s twins with 30,000 hours.

[VH-MLE]

"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.

[Duck Pilot]

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.

[clark y]

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.

[Xeptu]

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.

[Mr Mossberg]

Does anyone know if JO was the pilot?

[Cedrik]

Does anyone know if JO was the pilot?
No he wasn't

[Mr Mossberg]

Cedric, thanks for the advice.

[43Inches]

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.

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.

[PoppaJo]

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.

[lucille]

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?

[TBM-Legend]

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

[morno]

I wouldn’t have thought that it would have a complex pressurisation system, so I’d expect that even if they didn’t set the pressurisation to go back up to F280, all that’s going to happen is it’s going to hit max diff and open the safety valves to maintain max diff. The cabin isn’t going to magically depressurise because it wasn’t set to climb back up to F280.

[Capt Fathom]

I just find it sad the crap that is posted here after every accident. Let the authorities deal with it and stop the one-upmanship.

[Xeptu]

I just find it sad the crap that is posted here after every accident. Let the authorities deal with it and stop the one-upmanship.

It's natural to speculate. I doubt it's a forgot to reset the pressurization as previously stated it will hold sea level to max diff then climb at the aircraft climb rate, all assuming it was not turned off and did not fail. I would revisit pressurization if the aircraft had long since passed it's descent point and there was no radio transmission.
With one engine out, feathered or not at the stall it's still going to roll on its back.

[the_rookie]

I just find it sad the crap that is posted here after every accident. Let the authorities deal with it and stop the one-upmanship.
​​​​​​
Exactly. Some of the comments here are utter crap and show the inexperience of the person behind the keyboard

[illusion]

This series of aircraft have quite nasty stall characteristics. It will flick into a spin in the blink of an eye.

RIP.

[PoppaJo]

​​​​​​
Exactly. Some of the comments here are utter crap and show the inexperience of the person behind the keyboard
Right.

So let’s wait for the investigative body to do its job and report its findings. That’s how many years? I’m not saying let’s just come to our own conclusions, but it’s healthy to discuss these things post events, it will be a while before we get actual answers, the time taken by investigating bodies to provide the industry with answers, let alone reform, is unacceptable as many know, and as many training departments know.

My previous employer lodged a complaint with the body for the time it took to report on an incident, the time that passed without any information provided to the business and also the failure to disclose during the multi year wait, key findings which they advise they will release of safety is at risk during the investigation period.

Was a chap on here not that long ago that picked up an issue with his aircraft because of people actively taking about it on here.

[Dora-9]

This series of aircraft have quite nasty stall characteristics. It will flick into a spin in the blink of an eye.

Based on your own personal experience? I've only flown the admittedly much lighter 500/560 and their stalling characteristics certainly weren't "nasty".

[KRviator]

So I went back a little bit to look at some previous flights, and there's one on the 24th October, Toowoomba-Isa with a virtually identical vertical profile, in a similar geographic area. When you factor this second flight in, it does look like the descent from cruise altitude wasn't as a result of a problem or troubleshooting, but part of their normal operations. Whether such a descent could result in 'forgetting to reset' a pressurisation controller that might explain the final few minutes, I'll leave to someone actually rated on the Commander.

The accident flight.
https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/1261x545/hpy04nov_5101fdbe2a5008a7b6c81f96828b6f45ff5ce24d.jpg

And one a week earlier over the same route.
https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/1261x549/hpy24oct_c4ee86f6eb45ee8be155f15b5cf6b4f919090530.jpg

[Xeptu]

Based on your own personal experience? I've only flown the admittedly much lighter 500/560 and their stalling characteristics certainly weren't "nasty".

I understand this aircraft is a turbo commander, fitted with Garretts, TPE331's they are a beast nothing like the piston variant. I've never been a fan of Garretts negative torque sensing system (NTS) rarely are both props blade angles identical at flight idle.
Clearly there are misconceptions around these issue and I think it's healthy to discuss it from a learning perspective. People do learn things here you know.
One of my personal favorite training exercises is a flame out in the cruise at max cruising altitude and watch it unfold, usually takes about 50 seconds while the pilot is distracted with engine instruments and checklists. For sim instructors do this with motion "off "

[43Inches]

remember the Paine Stewart Lear 35 accident

Or the Kingair that depressurized Perth to Leonora in 2000. There's been more than a few depressurized events in aircraft like this. I'm in no way saying that this is the only option, it just seems to fit so far in what little information we have.

I would revisit pressurization if the aircraft had long since passed it's descent point and there was no radio transmission.

It was 80-90 NM east of Isa when it departed FL 280. That would put it on profile for a 3x if it was intending to land at Mt Isa, however it did not seem on track for Isa at the time, I would assume that descent clearance/traffic should have been passed on by then, so it will be interesting if they had responded to that.

I wouldn’t have thought that it would have a complex pressurization system, so I’d expect that even if they didn’t set the pressurization to go back up to F280, all that’s going to happen is it’s going to hit max diff and open the safety valves to maintain max diff. The cabin isn’t going to magically depressurize because it wasn’t set to climb back up to F280.

I'm not familiar with the pressurization system on this aircraft, but one thing I do know is that there is many different systems that work in different ways. Some you just set destination elevation and it's set and forget, others you have to be more interactive with what is set and intended cruise altitudes. My angle was how does this system work, does it automatically enter descent mode and continue descent (depressurize) unless told otherwise or is it more automatic and can sense intermediate level offs and climbs, or is it more manual with a need to set cruise altitudes and set schedules, the later seems unlikely as these are post 1980s aircraft, but stranger things have been built. I'd also be interested in the fuel system, does it have aux and mains, or just a set of interconnected mains that feed tank to engine. All I can find is that the 690 had 3 tanks with a center tank, but the 695A streamlined it somehow and reduced refueling times.

I'm also still struggling to see a structural failure element in this. If a wing separated or deformed I can't see how the autopilot managed to keep it straight and level until it basically stalled, if the pilot was flying why did they not initiate a descent to keep speed up to maintain control. None of this fits with a structural failure, more a loss of power that led to speed loss and departure from controlled flight when it reached near the stall.

[Dora-9]

Xeptu;

Thanks indeed for your response. Been there/done that/seen that too!

What I was querying was if the Commander 1000's stalling characteristics are any better or worse than comparable types at similar altitudes. "illusion" states that they're worse - I was wondering just where that came from...

[Xeptu]

The autopilot will hold all the way to stall warning, albeit with significant aileron roll input and some roll towards the dead engine. It will automatically disengage at stall warning, usually followed by a rapid roll towards the dead engine.

In my experience for the ones we deliberately don't brief first action, which is initiate a drift down aiming for 150kts, and at least point towards a suitable airport, so it's altitude select, just spin it down, IAS, rudder trim, then take action. For the ones that know everything and need a fright.
The unbriefed ones it goes something like this, flame out, eyes on engine instruments, look out the window to see if there's something to see, reach for the checklist, at which point the autopilot disengages followed by a snap roll toward the dead engine.

The end result, the prop was never feathered, the maximum speed was exceeded by around 40 kts at exercise termination. SIM ONLY of course.

[Xeptu]

Xeptu;

Thanks indeed for your response. Been there/done that/seen that too!

What I was querying was if the Commander 1000's stalling characteristics are any better or worse than comparable types at similar altitudes. "illusion" states that they're worse - I was wondering just where that came from...

It's all about the Garrett engines and it's NTS system. Unless it's a real one which we would not do, the simulated failed prop can be anywhere in the beta range, which defeats the purpose of the exercise with respect to behavior.. Personally I'm not a supporter of deliberate stalling with these engine types.

P.S I didn't say that right, I meant out of the beta range, as the aircraft approaches the stall the aerodynamic assistance lets call it on the prop is reduced, which leads to higher dependency on the NTS system and it's not great. If the prop goes beta at the stall your on your back in a nano second.

[lucille]

Xeptu, correct me if I’m wrong..it’s been 40 years since I fiddled with a 331.

My memory of the NTS system is that it cycles the blade angle between feather and some other blade angle to minimise drag - where drag is the condition when the airflow is driving the engine.

The idea being that this feature buys the pilot time to recognise the failed engine and feather it.

I don’t understand how NTS, if working as intended, would flip anything on its back anymore than say stalling an aircraft with the operative engine producing power.

Is it possible that the fidelity of the simulator in question may be lacking at that extreme corner of the envelope?

[Xeptu]

Xeptu, correct me if I’m wrong..it’s been 40 years since I fiddled with a 331.

My memory of the NTS system is that it cycles the blade angle between feather and some other blade angle to minimise drag - where drag is the condition when the airflow is driving the engine.

The idea being that this feature buys the pilot time to recognise the failed engine and feather it.

I don’t understand how NTS, if working as intended, would flip anything on its back anymore than say stalling an aircraft with the operative engine producing power.

Is it possible that the fidelity of the simulator in question may be lacking at that extreme corner of the envelope?

No not at all. The Negative Torque Sensing System NTS senses negative torque that zone from full fine going into beta reverse range, there are no fine pitch stops other than mechanical locking pins used to hold the blade in fine pitch for on ground starting, min drag. you then pull reverse to to allow the locks to throw out by centrifugal force.
In flight when you reduce to flight idle thus reducing blade angle toward fine, the NTS senses if the blade angle has gone too far and directs oil pressure to the hub to coarsen the blade angle in order to keep it in the flight range. A light for each propeller illuminates to warn you that the NTS system is sensing negative torque and is doing its job.

Does that explain the system without getting too technical.

[Dora-9]

Is it possible that the fidelity of the simulator in question may be lacking at that extreme corner of the envelope?

Simulator certification/acceptance is one area I can claim some little knowledge - the answer is YES.

[ForeverFltSim]

Former RAAF fighter pilot

[Mr Mossberg]

I just find it sad the crap that is posted here after every accident. Let the authorities deal with it and stop the one-upmanship.

A couple of factors at play here, human nature being the strongest factor. Whether you like it or not, people speculate. If you don't like it, don't click on the thread, you know what will be in here.

People.....pilots want to work out what happened, for a number of reasons. So they can learn from it, so they can design training scenarios. If it happened once, it can happen again.

Another factor, let the authorities deal with it? We're talking about the ATSB here, the organisation of 3 year investigations. What do you expect pilots will do? Sit around and wait 3 years?

You've been a member of this bulletin board for quite some time. You should be able to work out which comments are worth reading and vice versa.

[Duck Pilot]

A couple of factors at play here, human nature being the strongest factor. Whether you like it or not, people speculate. If you don't like it, don't click on the thread, you know what will be in here.

People.....pilots want to work out what happened, for a number of reasons. So they can learn from it, so they can design training scenarios. If it happened once, it can happen again.

Another factor, let the authorities deal with it? We're talking about the ATSB here, the organisation of 3 year investigations. What do you expect pilots will do? Sit around and wait 3 years?

You've been a member of this bulletin board for quite some time. You should be able to work out which comments are worth reading and vice versa.

Spot on.

One great thing about pilots in general is that most want to learn from other pilot’s experiences no matter how good or bad, unfortunately in most cases the trigger is accidents or serious incidents.

As far as accident reports go, some are good and others are completely inaccurate usually due to inexperienced investigators or influence from stakeholders external to the investigation authority.

[SWMBO]

Duck Pilot....... Post of the century.

I would like to meet you one day.

[Duck Pilot]

No worries, private message me👍

[extralite]

Former RAAF fighter pilot lol first post.

[morno]

lol first post.

True, however apparently accurate information.

[megle2]

All I’m hearing is structural / left wing

[Xeptu]

All I’m hearing is structural / left wing

Are the four corners present at the crash site.

[KRviator]

Are the four corners present at the crash site.I don't recall seeing any news articles even showing photos of the crash site yet alone details that precise.

One of the victims has been named as 22YO American William Joseph Jennings. No details yet on the other two.

[PiperCameron]

I don't recall seeing any news articles even showing photos of the crash site yet alone details that precise.

Here's the ATSB Investigation link: https://www.atsb.gov.au/publications/investigation_reports/2023/report/ao-2023-053

Gulfstream 695A JetProp Commander, registered VH-HPY, about 30 NM south-east of Cloncurry

Doesn't say anything we don't know already.

[wheelyfunny]

ditto from engineers

[43Inches]

Given the altitude it departed controlled flight from, it is conceivable that it exceeded structural limits in the dive and broke up on descent, so that does not necessarily mean it broke up prior to loss of control. That's if it broke up at all. There's a lot of information still to be released as to what happened.

[TBM-Legend]

Given the altitude it departed controlled flight from, it is conceivable that it exceeded structural limits in the dive and broke up on descent, so that does not necessarily mean it broke up prior to loss of control. That's if it broke up at all. There's a lot of information still to be released as to what happened.

ftom a very reliable source it was in one piece and plenty of fuel

[43Inches]

ftom a very reliable source it was in one piece and plenty of fuel

Goes back to a question I asked earlier, does the 695A have Aux/mains setup? or just a single tank/interconnected tanks to engine with cross-feed.

[Xeptu]

Goes back to a question I asked earlier, does the 695A have Aux/mains setup? or just a single tank/interconnected tanks to engine with cross-feed.

Where are you going with that 43, what difference does it make.

[43Inches]

Where are you going with that 43, what difference does it make.

If it was running on aux tanks and depressurized then it may have exhausted that tank short of the destination, resulting in an engine out, and there would be still significant mains fuel left, as mentioned above, Pilot is unconcious, cant correct and so on. If it had single tank to engine set up it would have enough endurance to fly well passed the destination. Which makes depressurization less likely.

[Xeptu]

If it was running on aux tanks and depressurized then it may have exhausted that tank short of the destination, resulting in an engine out, and there would be still significant mains fuel left, as mentioned above, Pilot is unconcious, cant correct and so on. If it had single tank to engine set up it would have enough endurance to fly well passed the destination. Which makes depressurization less likely.

Ah! I see, I think depressurization is unlikely, but I see your theory. I think we are both on the same page with respect to engine out. It should have been indicating about 160 kts, altitude locked should take about one minute to come back to 100 kts and stall. That's why I went straight to a training exercise gone wrong, thrust reduction but a very generous zero thrust to take 2 mins.

[Duck Pilot]

Training exercise gone wrong?

Was this a training flight or a Part 138 operation? If it was a 138 op and the pilot in the left seat was doing ICUS, why would the trainer in the right seat simulate or shut down an engine with another person in the back. Might explain if it was a CASA FOI in the back.

[Xeptu]

Training exercise gone wrong?

Was this a training flight or a Part 138 operation? If it was a 138 op and the pilot in the left seat was doing ICUS, why would the trainer in the right seat simulate or shut down an engine with another person in the back. Might explain if it was a CASA FOI in the back.

I'm not suggesting it was, it's just where why mind went to account for a 2 minute speed reduction to the stall. Perhaps I should have gone with partial engine failure, loss of significant torque.

[Duck Pilot]

All good speculation based on our individual experiences. Very healthy debate on a public forum by professionals.

We don’t know the circumstantial facts yet apart from the fact that the aeroplane crashed, for what reasons we don’t know.

[Squawk7700]

All good speculation based on our individual experiences. Very healthy debate on a public forum by professionals.

We don’t know the circumstantial facts yet apart from the fact that the aeroplane crashed, for what reasons we don’t know.

You can get a full flight profile from the ADSB these days... in some cases, you could literally work out the cause of a crash before the fire is extinguished and has destroyed the evidence that remained.

[Duck Pilot]

You can get a full flight profile from the ADSB these days... in some cases, you could literally work out the cause of a crash before the fire is extinguished and has destroyed the evidence that remained.

Sincere apologies, I didn’t know this?

Maybe you should pass that information onto the federal government in order to prevent wasting taxpayers money on having the ATSB do aviation investigations.

Pprune is an absolute GREAT source of VALUABLE INFORMATION.

I now feel absolutely belittled by posting anything on this forum, I know absolutely nothing in comparison to some of the industry experts who post on this forum, particularly with me having 35 years experience in the industry as an engineer, pilot, regulator and aviation consultant…..

[Squawk7700]

I’m just saying that the landscape has changed with the technology.

Nowadays you can quickly find a potential cause and head in that direction rather than analysing the element in a halogen lightbulb in order to determine if it was illuminated at impact. You probably can’t even do that any more with these fancy new LED’s.

[compressor stall]

You can get a full flight profile from the ADSB these days... in some cases, you could literally work out the cause of a crash before the fire is extinguished and has destroyed the evidence that remained.
No you can’t.
I know of one event on ADSB that showed 500’ out from what actually occurred. Im sure that there are many others.

[Squawk7700]

No you can’t.
I know of one event on ADSB that showed 500’ out from what actually occurred. Im sure that there are many others.

... along with many others that do show the correct numbers.

The most likely reason for that would be due to the ADSB feed being based on a QNH of 1013.2.

[Xeptu]

I don't know how good ADSB data is but presumably if it's good enough to determine that there was in fact a turn to the left at event onset, then the data must be pretty good.

[Squawk7700]

I don't know how good ADSB data is but presumably if it's good enough to determine that there was in fact a turn to the left at event onset, then the data must be pretty good.

The ADSB feed from the recent SR22 accident was super detailed. Posters here were posting speed, altitude, graphs, heading and a graphical representation of the flight path. That’s presumably based on FR24 ADSB receivers and not the ASA ones… I presume someone may know, they may be able to provide more detailed info.

[KRviator]

IIRC, the ADS-B squit (transmission) is 2Hz, so if you can recieve it, you can build a very detailed 3D picture of the flightpath. And from that, if you have the right software, in some cases you can derive the FCU selected or commanded modes from the relevant data. Such detailed info isn't always displayed on FR24 or FA, but it is there a lot of the time. For example, from a PC-12 overflying our hacienda right now we have:
https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/479x396/fasa_capture_c8b96af7695025766eb923f146e33e547803ccee.jpg

[Alice Kiwican]

Goes back to a question I asked earlier, does the 695A have Aux/mains setup? or just a single tank/interconnected tanks to engine with cross-feed.

A reliable source tells me the 695A does have aux/mains setup and rumour has it this aircraft had pressurisation issues on a couple of previous flights before the accident.

Hopefully we’ll get some answers sooner rather than later.
RIP to the 3 crew

[lucille]

If it was a training exercise, surely the trainer would have intervened long before the stall.

TUC at 28,000 ft is 2.5 to 3 minutes… given some people can march up Everest without oxygen, that 3 minute number is probably (rightfully) on the conservative side.

I would assume the 695 has a cabin altitude alert together with a chime should the cabin altitude exceed something like 10,000 which makes it hard to believe the crew failed to recognize a surreptitious depressurisation.

Not a lot makes sense with this incident. Structural failure? But in all likelihood it was smooth air up at FL280, so that rules it out.

[Xeptu]

If it was a training exercise, surely the trainer would have intervened long before the stall.

I don't think we can rule anything out yet.

From a training perspective, because we so diligently brief our pilots about the exercise we are about to do, there's an expectation that it will unfold as planned. You can tell how often it doesn't by the finger print marks around the freeze button in the sim lol. We know it as human factors.

[India Four Two]

TUC at 28,000 ft is 2.5 to 3 minutes… given some people can march up Everest without oxygen, that 3 minute number is probably (rightfully) on the conservative side.

lucille,

There's a difference. The people who "march up" Everest spend several days, if not weeks, working up to higher altitudes and thus become acclimatized. They don't go up there at ~1000 fpm.
​​​​​​​

[compressor stall]

...

The most likely reason for that would be due to the ADSB feed being based on a QNH of 1013.2.
No. The difference was much greater than that.
Verified by other data sources.

I’m not saying it’s all wrong. But acknowledge the possible errors.

[PiperCameron]

No. The difference was much greater than that.
Verified by other data sources.

I’m not saying it’s all wrong. But acknowledge the possible errors.

Like all electronic trickery these days, Garbage In = Garbage Out. When it comes to baro readings, a faulty sender can very easily indicate something significantly different to GPS altitude with the folks on the light deck none the wiser... one reason both are sent in an ADS-B feed.

[Squawk7700]

one reason both are sent in an ADS-B feed.

If that is in fact correct, FR24 and others must be using Baro for some reason.

[physicus]

I don't know how good ADSB data is but presumably if it's good enough to determine that there was in fact a turn to the left at event onset, then the data must be pretty good.
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.

For b), you can read up on this in the standards document RTCA DO-260B that defines the ADS-B standard, and in DO-181E defining the ATCRBS/Mode S Airborne equipment standard.

ADS-B / Mode S ES (extended squitter) transmissions are taking place at a staggering rate. Some messages like state vector reports (altitude, speed, position) are broadcast up to 50 times per second, while operational status reports such as the callsign are broadcast only once per second, and additional information messages that may contain autoflight/FMC configuration information, indicated airspeed, and atmospheric parameters are broadcast only every few seconds and only when interrogated by an ATS system (i.e. a ground based radar) wanting to know that information. That's why in FlyRealTraffic.com's radar screens for example, you see data from suitably equipped aircraft flying in radar coverage in Australia and Europe showing the autopilot modes as well as current IAS, TAS, wind vector and outside temperature, while the same aircraft flying in the US will often only show the autopilot modes but no weather information - because ATS are not requesting the weather info in the US.

Flight tracking services are aggregating that information into snapshots, in the case of FR24 in 5s intervals, in the case of FlyRealTraffic.com in 2s intervals. So if you see a target in your web browser with many different parameters, those parameters are not all true at that particular point in time. They're a mish mash of parameters *around* that time. And some may be well out of date.

The most basic errors pprune users often make pertain to the basic information provided:
- Altitude is always from a barometric source, and always reported to standard pressure, i.e. it's a FL that's being reported. The resolution is bit encoding limited to 25ft.
- vertical speed has its own message that is often transmitted at an even higher rate than altitude and position. So a particular VS may be completely separate from the reported altitude.
- Position, track, and speed are always in reference to the ground and broadcast in an "Airborne position message". In normal ops they are directly fed from the GNSS systems, but in IRS equipped aircraft, the IRS is used as an automatic failover source should GNSS be U/S. The "type" subfield code in the DF (downlink format) 17 or 18 messages tells the receiver to what horizontal containment radius limit (Rc) the position is known - that's similar to an RNP parameter. So if the GNSS receiver has failed and the aircraft is using IRS navigation, that parameter will be updated with the estimated position uncertainty from the FMC. An Rc of 9 means better than 7.5 meters. An Rc of 17 means better than 20NM. You get the drift. Yet you won't find that parameter in any flight tracking website derived ADS-B feed.

So when "investigating" an accident from afar based on ADS-B data, you have to keep all these factors in mind. There may be faulty input that leads to faulty ADS-B data - garbage in, garbage out. There may be "hanging" data fields in the ADS-B data providers feed, data that is stale and no longer applicable at the particular point in time.

Use the data by all means to try and make sense of what happened, but use it with caution.

[physicus]

If that is in fact correct, FR24 and others must be using Baro for some reason.
As I just posted, ADS-B altitudes are *always* barometric. The GNSS derived height may or may not be present, it's optional.

[PiperCameron]

If that is in fact correct, FR24 and others must be using Baro for some reason.

Probably, because that's what we use to fly our airyplanes. :)

(And, yes.. what he said above)

[Xeptu]

Thankyou PHYSICUS a very informative post. I reminisce when IRS came out and remember thinking how good is this. I date all the way back to VLF OMEGA..

[PiperCameron]

The most basic errors pprune users often make pertain to the basic information provided:
- Altitude is always from a barometric source, and always reported to standard pressure, i.e. it's a FL that's being reported. The resolution is bit encoding limited to 25ft.

Ahh.. No. Altitude is not "always reported to standard pressure" - it's reported to the pressure the pilot enters into his altimeter as the QNH. In the flight levels that'll be standard pressure, but below these it will be referenced to whatever he selected, right or wrong. To do otherwise would be to imply a level of sophistication not found in most GA aircraft (and be just plain wrong at ground level anyways).

I'd say that's pretty basic error from a pprune user right there!!

[physicus]

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.

Here a screenshot from RTCA DO-260B defining what altitude shall be reported:
https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/700x234/screen_shot_2023_11_09_at_17_30_36__8b194cb8ec15c752fcb1eede a22c64fc8fb57c9c.png

[Xeptu]

I remember when the first mode charlie transponders where being offered to unpressurized bug smashers were self contained units, most altimeters weren't capable of providing that information, so the unit had its own pressure referencing output. It makes sense that it would be referencing standard pressure. In any case we are only talking 300 feet.

[Squawk7700]

That’s a big mistake PC and you need to get your head around that for future discussion.

The QNH that you are entering into your altimeter via the dial is in no way linked to the transponder.

The reason the transponder reports based on 1013.2 (as noted in the post above) is so that ATC knows exactly what your altitude is, as the ATC system does the conversion at their end based on the current area QNH. Therefore if you have incorrectly set the QNH or not set it at all on your dial, or you’re on a long flight and have moved into a different pressure system, then they will still know pretty much your exact height.

This explains why if you’re watching your ADSB-IN feed from your EFB you may notice someone zipping along at 200 ft across an area where the buildings are bigger than that, because their OUT is in Barometric pressure and Flight Radar 24 isn’t smart enough to know the area QNH for the conversion.

My EFB shows me traffic with a +003 next to it for example so that the QNH is never an issue as I simply know that the other aircraft is 300ft above me. That’s a clever way to do it as if it said 3,500 and you thought you were at 3,200 but your QNH was wrong you’ll be in the poo.

This safety measure assumes that you’re diligently getting your transponder serviced every 2 years and it’s maintained it’s calibration between servicing.

[Dora-9]

Xeptu:
PM sent.

[PiperCameron]

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.

Well.. there you go. Despite what some may say, there's always something to learn on pprune.. :uhoh:

[J.O.]

Not a lot makes sense with this incident. Structural failure? But in all likelihood it was smooth air up at FL280, so that rules it out.

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.

[Cedrik]

Agreed JO. Old higher time airframe, cumulative fatigue + previous over stressing.
Have the other two crew names been released anywhere?

[43Inches]

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.

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.

[J.O.]

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.

You will note I wasn't commenting on the specifics of this accident, but responding to a claim that an airframe couldn't fail in "smooth air".

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.

[Xeptu]

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.

Partial engine failure (loss of significant torque) and the rejected takeoff at V1 remain the most common mismanaged events.
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.

[compressor stall]

The C441 (same engines) in Renmark stalled and crashed during a training exercise with 3 professionals on board just the same.

Without being overly pedantic, it didn’t stall.

[Xeptu]

Without being overly pedantic, it didn’t stall.

How do you figure that. Do Tell

[compressor stall]

How do you figure that. Do Tell

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.

[Xeptu]

From the ATSB report.

You said not to be too pedantic. A Vmca event is still a stall, is it not

[heretolearn]

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.

[compressor stall]

You said not to be too pedantic. A Vmca event is still a stall, is it not

Vmc for the 441 (it's different for newer types) is the minimum calibrated airspeed at which, when the critical engine is suddenly made inoperative, it is possible to maintain control of the airplane with that engine still inoperative, and thereafter maintain straight flight at the same speed with an angle of bank of not more than 5 degrees. It's the rudder moment being weaker than the asymmetric thrust moment.

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).

[VH-MLE]

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…

[Xeptu]

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"

[Captain Darkwing]

The Commanders have pronounced washout on the wing tips preventing tip stall.

[First_Principal]

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.


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.

[Clare Prop]

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?!

[43Inches]

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.

That's why you follow the trend data, interpolated data will continue doing what it's doing, if the trend is changing then that's not extrapolating/interpolating it's new data. The trend on this aircraft is quite marked towards the end and shows a gradual slow down to almost stall and then left turn and descent. As far as how accurate the data is, and what source, it does not matter in this case, the actual aircraft could be +-2000 feet and +-20 kts GS and the trend would still show the same information, it slowed down straight and level and then entered a left spiral motion before leaving coverage. Unless somebody for arguments sake altered the data intentionally then the ADSB plot would not make that scenario up. There's nothing to suggest in the plots leading up to the incident that there was any accuracy issue.

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.

[megan]

A Vmca event is still a stall, is it notXeptu, be interested to know how you relate a Vmca event to being a stall.

[compressor stall]

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?!
You’re exactly right Clare. However the accident aircraft was on a steady climb after departure, and highly improbable that other factors were at play marking the stall happen at a higher IAS.

I agree that paragraph could be better worded but I doubt it would change much.

[lucille]

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 agree. Structural failure cannot be ruled out.

But I suspect you’ve taken me too literally, next time I will couch my language with more nuance. My ill chosen words “ruled out” were never intended to be absolute. But rather to suggest the likelihood of a structural failure in smooth air is slight.
Like many others here who have endured years of single pilot night freight work in unpressurized, geriatric, non radar equipped aircraft, we can attest to their sturdiness.

[J.O.]

It's troubling that no factual information update has been provided for this one. Usually when multiple fatalities occur, they'll provide a preliminary report within 30 days. Surely they could share what they have (or haven't) found thus far.

[nomess]

Christmas Break mid Dec to mid Jan. Skeleton staff.

[KRviator]

Interim report (https://www.atsb.gov.au/sites/default/files/2024-02/AO-2023-053%20Preliminary_0.pdf) is out and makes for...interesting....reading.

[Lead Balloon]

"all major aircraft components were accounted for at the point of impact"

[lucille]

Interim report (https://www.atsb.gov.au/sites/default/files/2024-02/AO-2023-053%20Preliminary_0.pdf) is out and makes for...interesting....reading.

It does make interesting reading. It’s implied the pilot was ex military and thus well trained, which makes this incident all the more mysterious.

Odd that the pilot should choose to advise ATC that the aircraft oxygen system was working normally. Why would anyone ever do that? Looks like the ATSB is looking at the hypoxia theory.

Does the AC695 not have a Cabin Alt annunciator? Does it have auto mask drop?

I have the same question regarding BE200s.. Another thread about Pelair BE200 aircraft having to return to base after the rubber jungle drops. Surely the Cabin Alt warning would light up at +/- 8000ft, long before the jungle drops.

[KRviator]

Does the AC695 not have a Cabin Alt annunciator? Does it have auto mask drop?

I have the same question regarding BE200s.. Another thread about Pelair BE200 aircraft having to return to base after the rubber jungle drops. Surely the Cabin Alt warning would light up at +/- 8000ft, long before the jungle drops.ISTR it (the KingAir one) illuminates at a cabin altitude of 12,500, but that's just the relevant annunciator & the MASTER WARNING lamp, I don't remember the King Airs having an aural horn.

[Capt Fathom]

Odd that the pilot should choose to advise ATC that the aircraft oxygen system was working normally. Why would anyone ever do that?


I suspect after 1 hour of radio silence, and the subsequent interaction with the pilot, ATC encouraged the pilot to check the pressurization! Bloody smart those ATCers!

[Lead Balloon]

If that's true - and I would be completely unsurprised if it is, because ATCers are indeed bloody smart - why doesn't the ATSB quote, verbatim, the terms of the ATC transmissions and the terms of the PICs transmissions? They are facts. The words used are whatever words were used.

What's the point of paraphrasing and summarising the communications? (My long-held view is that excerpts of the actual recordings should be published as part of ATSB reports.)

[43Inches]

I'd be interested at what the statement that "both engines were running" means. Does that mean delivering power or the propeller and associated turbine was rotating. Noting that turbines will easily windmill with little effort as there is no real compression stopping it, unless it was feathered. From the limited picture contained in the prelim it looks like the right blade is definitely bent/curled back, but the left ones don't look anywhere near as deformed. It's also possible if the crew were incapacitated by hypoxia that as they slumped they could bring the power levers back unintentionally.

The statements regarding speech rate slowing and multiple goes at getting a place name correct are fairly ominous signs though.

[Lead Balloon]

You mean you haven't solved this one yet, 43? You're slipping...

[Squawk7700]

Odd that the pilot should choose to advise ATC that the aircraft oxygen system was working normally. Why would anyone ever do that?

Rookie question... the aircraft is pressurised, but yet the pilot referred to the oxygen system. Is it normal to refer to the cabin pressurisation system as the oxygen system?

​​​​​​​Perhaps they were actually running on oxygen?

[lucille]

Pressurisation systems and O2 systems are two different independent systems and are, for want of a better word, “unrelated”.

Its a fair assumption that one would only be aware that the O2 system was functioning normally is if one was actually using it at that time. I could argue that a preflight test of masks and flow some 3 hours earlier would not give one the confidence to say it is working now.

Muffled comms from the pilot may be due to a dodgy mask mic.

But then, who in their right mind would continue on at FL290 breathing oxygen. Also, there would be three of them sucking off the one bottle. Someone typed on the aircraft could tell us how many minutes of oxygen at 29,000 ft with three adults sucking off it. My guess would be 15 minutes max.

[VH-MLE]

A few thoughts on what seems to be the direction the investigation is taking…

At the time of the accident, I was certainly not thinking it was a hypoxia related accident, however the ATSB’s preliminary report certainly has me thinking it was hypoxia related now.

I agree in part with the statement by Lucille: “It’s implied the pilot was ex military and thus well trained, which makes this incident all the more mysterious.” However, as we all know, hypoxia is a very insidious condition & pilots of all levels of experience & training, have succumbed to it in years gone by (e.g. Helios 522 – a multi-crew B737 & VH-OYA – a B200 Kingair operated by an RAAF pilot (who had had several previous hyperbaric chamber hypoxia training sessions). The message is no matter how good we think we are, how well we’re trained etc, none of us are exempt from being caught out, or nearly caught out, in some catastrophic event

Here is an extract from another hypoxia/pressurisation event that occurred in WA back in 2009 & involved VH-TAM – a Kingair C90 aircraft. In that incident, the squat switch, which was supposed to “tell” the pressurisation system that the aircraft was airborne & could start pressurising the aircraft, did not work as expected & the aircraft did not pressurise. Compounding this, the cabin altitude alerting system had been wired up incorrectly & as such, did not display a “CABIN ALTITUDE” warning to the pilot.

Extract from ATSB report: “Sometime after becoming established at flight level (FL) 210, the pilot became affected by hypoxia, which resulted in him becoming fixated on the ‘distance-to-run’ figures on the aircraft’s Global Positioning System equipment display and incorrectly interpreting those figures as the aircraft’s ‘groundspeed’. That confusion resulted in the pilot interpreting the lower-than-expected figures as a significant headwind and in him descending the aircraft to escape the winds. Once established at FL150 for a significant period of time, he realised that that he had been affected by hypoxia. The pilot descended further before landing at his destination. The investigation identified problems with the aircraft’s left landing gear squat switch that prevented the aircraft from pressurising in flight. In addition, the cabin altitude warning system was non-operational due to the incorrect connection of the switch wiring during previous maintenance.”

When the final report comes out, there will be some important messages, however as they say, there aren’t really any new accidents anymore – just similar ones reoccurring. This is not helped by the age of some of the aircraft involved. I thought VH-HPY was reasonably “new” having been manufactured in 1982, however on reflection, that is 40+ years ago now…

Just my 2 lire’s worth & RIP once again to those that perished…

[nomess]

Here is a good but disturbing video on the hypoxia subject that is used by many training providers. Watch 6 mins onwards. It’s incredibly hard to rectify once time passes. Note the male below just sat there and would have died without assistance.

https://youtu.be/kUfF2MTnqAw?feature=shared

[43Inches]

The VH-TAM accident highlights why you should have a transition altitude checklist that includes a pressurisation check. There should also be a cruise altitude checklist for once you have leveled off. Both checks should involve ensuring the pressurisation is not only on, but working as intended.

Even large airliner crew can stuff it up, as with the Helios airlines 737.

[PiperCameron]

Pressurisation systems and O2 systems are two different independent systems and are, for want of a better word, “unrelated”.

Its a fair assumption that one would only be aware that the O2 system was functioning normally is if one was actually using it at that time. I could argue that a preflight test of masks and flow some 3 hours earlier would not give one the confidence to say it is working now.

Could the early descent and climb have anything to do with it? Maybe the pilot had a gut feeling of a problem and wanted a descent to check pressurisation was working properly but then satisfied himself (incorrectly) that it was and never looked at it again??

It may not mean anything at all, but with no reported weather reason to do so and FL150 being still too high for sightseeing, a significant descent and climb back up like that is going to chew quite a bit of his fuel load so he must have had a good reason to do it.

[nomess]

Could the early descent and climb have anything to do with it? Maybe the pilot had a gut feeling of a problem and wanted a descent to check pressurisation was working properly but then satisfied himself (incorrectly) that it was and never looked at it again??

It may not mean anything at all, but with no reported weather reason to do so and FL150 being still too high for sightseeing, a significant descent and climb back up like that is going to chew quite a bit of his fuel load so he must have had a good reason to do it.
The area in which they conducted that descent had bushfires raging across the ranges. I would assume something to do with that as soon as they had passed the fires end, they commenced the climb essentially right away.

Fire surveillance at such levels isn’t unusual.

[dejapoo]

I always thought after the Bourketown king air ghost flight, if someone's garbling on the wireless everyone should be yelling put your oxygen on now. Reckon it'd help?

[megan]

a B200 Kingair operated by an RAAF pilot (who had had several previous hyperbaric chamber hypoxia training sessions)Not to forget F-18 A21-41 that flew from the Tindal area and crashed 100k NE of Weipa, crash site found after three years.RIP FLGOFF Cameron Conroy

[growahead]

43inches
The 737 crash you allude to was actually Helios Airways, based in Cyprus, with a German captain in command. The aircraft had German registration. Small point, I agree, but necessary clarification.

[VH-MLE]

"I always thought after the Bourketown king air ghost flight, if someone's garbling on the wireless everyone should be yelling put your oxygen on now. Reckon it'd help?" It certainly couldn't hurt in my opinion & to a small degree, I'm a little surprised ATC don't have procedures for something like that following the "Ghost Flight" accident in 2000 & the VH-TAM incident where both pilots were making unusual statements (including garbling or slurred speech).

When I first flew the C441 Conquest back in 1989, the guy that did my training said the two new things that will "bite" for flight above 10000ft are ice & hypoxia. Unfortunately he is/was 100% correct...

ps yes, Helios 522 was the B737 pressurisation accident...

[Runaway Gun]

During all of my hypoxia chamber runs, despite expecting it, I never once decided it was time to mask up. Despite being told to - and I have no memory of that.
Once I even tried to stop the doctor from putting my mask on for me.

My experience has alerted me to my initial symptoms whilst flying twice. The training is worthwhile.

[Noeyedear]

I flew a couple of models of Turbo Commander. It was SOP to turn off the O2 bottle (in the rear compartment) after each day or night of flying to prevent loss through system leakage. Easy enough to forget to turn back on.

Not implying that this is what occurred.

The pressurisation in a few that I flew was woeful. A combination of tired air cycle machines and issues with the underfloor tubing that delivered the air would often mean a 17,000' cabin at 25,000'. And that was with Hot Air temp on full. It was worse with cold temps selected.

[Clinton McKenzie]

17,000' cabin altitude. Wot cood possiblie go rong?

[Capt Fathom]

A combination of tired air cycle machines and issues with the underfloor tubing that delivered the air would often mean a 17,000' cabin at 25,000'.

So No Idea. How did that work out for the passengers and crew?

[Mach E Avelli]

I flew a couple of models of Turbo Commander. It was SOP to turn off the O2 bottle (in the rear compartment) after each day or night of flying to prevent loss through system leakage. Easy enough to forget to turn back on.

Not implying that this is what occurred.

The pressurisation in a few that I flew was woeful. A combination of tired air cycle machines and issues with the underfloor tubing that delivered the air would often mean a 17,000' cabin at 25,000'. And that was with Hot Air temp on full. It was worse with cold temps selected.
If the 695 pressurisation system is anything like the C441, there is a real trap when cold air is selected. The ducting can slowly become blocked with ice in one of the filters. Pressurisation is normal in the climb, but at altitude there is a subtle loss of cabin pressure as inflow reduces.
This nearly killed me on a long distance ferry flight. It was only from experience in the dreaded hypoxia chamber many years before that I recognised my symptoms in time to get the oxygen mask on. Another 20 or 30 seconds and it would have been lights out.
I wrote an article on this many years ago. In the analysis, an expert explained my failure to spot the warning light (no aural alert) as tunnel vision which is also a symptom of hypoxia. I remembered blue fingernails and dizziness, inability to concentrate, euphoria etc, but not the vision impairment effect.
A visit to the hypoxia chamber is no longer necessary for civilian pilots before flying pressurised aircraft; maybe it was never mandatory? It should be, particularly for single pilot operations - it’s more relevant than some of the other stuff we now have to do.