Light aircraft down near McKinlay, Qld
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?!
I agree that paragraph could be better worded but I doubt it would change much.
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.
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.
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.
"all major aircraft components were accounted for at the point of impact"
Interim report is out and makes for...interesting....reading.
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.
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.
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.
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!
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.)
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.)
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.
The statements regarding speech rate slowing and multiple goes at getting a place name correct are fairly ominous signs though.
You mean you haven't solved this one yet, 43? You're slipping...
Odd that the pilot should choose to advise ATC that the aircraft oxygen system was working normally. Why would anyone ever do that?
Perhaps they were actually running on oxygen?
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.
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.
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…
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…
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.
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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.
Even large airliner crew can stuff it up, as with the Helios airlines 737.
Last edited by 43Inches; 9th Feb 2024 at 04:29. Reason: Reference to Helios airlines.
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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.
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.
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.
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.
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.
Fire surveillance at such levels isn’t unusual.
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?