DHC Beaver down in Hawkesbury
Years ago I purchased a proper CO detector. I did that because my research showed that by the time those ubiquitous ‘dot’ cards stuck to the dashboard turn black, you’re likely already blacked/blacking out yourself. Further, many leaks start small - pinholes in exhaust systems that develop into cracks and other engine bay/firewall defects - and these create low CO levels in the cockpit that can nonetheless be detected by a proper CO detector before deleterious effects arise.
I was alarmed - literally - at the amount of CO that sometimes entered the aircraft during taxi, depending on wind direction and speed. And that was with windows open (in fact - that may have been the / one of the path/s of entry) and without smelling any strong exhaust smells. I’m talking levels at which protracted exposure would likely result in deleterious effects.
My eventual practise was to leave the detector switched off during taxi and take off, to avoid the distractions, and turn it on during the cruise. (The ‘off the shelf’ item did no have an on/off switch. I added that myself.) Fortunately it always read/s a big fat 0 in the cruise. I figured that the risk of a defect developing to ‘bad’ between a landing and the next taxi, take off and climb to cruise were lower than the risk arising from distractions from the alarm.
The combination of protracted exposure on the ground combined with ongoing exposure in the air due to aircraft defects? Not good. (My inexpert guess is that a pilot’s pulse rate and metabolism are running a bit faster in the initial phases of a flight than sightseeing passengers after a nice lunch...)
Modern and effective CO detectors are cheap insurance, folks.
I was alarmed - literally - at the amount of CO that sometimes entered the aircraft during taxi, depending on wind direction and speed. And that was with windows open (in fact - that may have been the / one of the path/s of entry) and without smelling any strong exhaust smells. I’m talking levels at which protracted exposure would likely result in deleterious effects.
My eventual practise was to leave the detector switched off during taxi and take off, to avoid the distractions, and turn it on during the cruise. (The ‘off the shelf’ item did no have an on/off switch. I added that myself.) Fortunately it always read/s a big fat 0 in the cruise. I figured that the risk of a defect developing to ‘bad’ between a landing and the next taxi, take off and climb to cruise were lower than the risk arising from distractions from the alarm.
The combination of protracted exposure on the ground combined with ongoing exposure in the air due to aircraft defects? Not good. (My inexpert guess is that a pilot’s pulse rate and metabolism are running a bit faster in the initial phases of a flight than sightseeing passengers after a nice lunch...)
Modern and effective CO detectors are cheap insurance, folks.
It appears that one of the contributing factors to CO ingressing the cabin on the ground is the position of the engine exhaust relative to the ingress points, typically the windows. Typically the exhaust ports are forward of cockpit windows.
I'm struck by the exhaust configuration for the Wasp Junior on the Beaver. Many are fitted with an extension that takes the expelled gases well to the rear of the forward doors. From the photos of NOO I've seen it didn't appear to be fitted with that extension so the exhaust gases appear to be expelled on the lower starboard side pretty much adjacent to the firewall.
I was also struck by what appears to be the very well ventilated engine compartment on the Beaver. The CO poisoning was meant to have been caused by exhaust gases leaking from a crack in the collector ring and then ingressing the cabin through three open bolt holes in the firewall. I would have thought that ventilation of the engine compartment would have carried leaked gases out the opening at the rear of the cowl.
Perhaps someone with time on the DHC-2 could comment.
Bonanza.
But I’m confident that that’s coincidence. I’m confident that if you put a ‘proper‘ CO detector in any ‘generic’ aircraft that’s idling on the ground, there will be a wind speed and direction that results in lots of exhaust gas circulating back into the cabin, especially if the windows are open.
But I’m confident that that’s coincidence. I’m confident that if you put a ‘proper‘ CO detector in any ‘generic’ aircraft that’s idling on the ground, there will be a wind speed and direction that results in lots of exhaust gas circulating back into the cabin, especially if the windows are open.
Bonanza.
But I’m confident that that’s coincidence. I’m confident that if you put a ‘proper‘ CO detector in any ‘generic’ aircraft that’s idling on the ground, there will be a wind speed and direction that results in lots of exhaust gas circulating back into the cabin, especially if the windows are open.
But I’m confident that that’s coincidence. I’m confident that if you put a ‘proper‘ CO detector in any ‘generic’ aircraft that’s idling on the ground, there will be a wind speed and direction that results in lots of exhaust gas circulating back into the cabin, especially if the windows are open.
I wouldn’t expect ATSB to do further investigative work across a variety of types, and would not criticise ATSB for not doing so. The ‘normal’ exposure to CO from the ‘normal’ operation of ‘average’ GA aircraft is evidently not a safety issue.
However, cracked exhausts and other defects will create CO risks in any GA aircraft. The questions in the case of this tragedy include:
1. Why were the defects in the engine bay not detected during any of the required inspections?
2. Why don’t the mandatory equipment requirements for a ‘standard’ GA aircraft require a reliable CO detector (and engine monitor) rather than pointless crap (from a safety perspective) like ADSB?
However, cracked exhausts and other defects will create CO risks in any GA aircraft. The questions in the case of this tragedy include:
1. Why were the defects in the engine bay not detected during any of the required inspections?
2. Why don’t the mandatory equipment requirements for a ‘standard’ GA aircraft require a reliable CO detector (and engine monitor) rather than pointless crap (from a safety perspective) like ADSB?
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Hopefully, final report will detail a more credible path of CO into cabin.
A few points apparent in Interim report:
- Coroner did not test for CO
- Post crash engine inspection did not flag CO leak issue.
- 2 years after crash, having drawn a blank on cause, ATSB tested for CO and found elevated levels in 3 of the 6 cabin occupants, zero in other 3.
- Subsequent engine examination identified cracked exhaust flange at cylinder as CO source. (Leak is into free air, that is propwash, slipstream and would be very much diluted.)
- CO path through fwd firewall into engine bay is not mentioned.
- Path from engine bay into cabin is said to be via missing bolts of magneto access panel. I am not familiar with Beaver, but typically we’re talking 3 x 3/16 bolt holes.
Question then is, is it possible for something nothing CO via broken path to cause elevated levels of CO in such a short, about 7 or 8 minutes, period of engine operation?
A few points apparent in Interim report:
- Coroner did not test for CO
- Post crash engine inspection did not flag CO leak issue.
- 2 years after crash, having drawn a blank on cause, ATSB tested for CO and found elevated levels in 3 of the 6 cabin occupants, zero in other 3.
- Subsequent engine examination identified cracked exhaust flange at cylinder as CO source. (Leak is into free air, that is propwash, slipstream and would be very much diluted.)
- CO path through fwd firewall into engine bay is not mentioned.
- Path from engine bay into cabin is said to be via missing bolts of magneto access panel. I am not familiar with Beaver, but typically we’re talking 3 x 3/16 bolt holes.
Question then is, is it possible for something nothing CO via broken path to cause elevated levels of CO in such a short, about 7 or 8 minutes, period of engine operation?
- 2 years after crash, having drawn a blank on cause, ATSB tested for CO and found elevated levels in 3 of the 6 cabin occupants, zero in other 3.
No, it was a bit more than that.
“During the draft investigation report review process, the aviation medical specialist engaged by the ATSB recommended that carbon monoxide (CO) toxicology testing be undertaken on blood samples of the aircraft occupants that had been taken and suitably stored by the New South Wales State Coroner. This required testing at a specialised laboratory. With results pending, the ATSB draft report was submitted to Directly Involved Parties (DIPs) in December 2019 for comment.
The results of the testing were provided to the ATSB in March 2020, indicating that the pilot and two of the passengers had elevated levels of CO. The ATSB notes that post-mortem examinations established that the pilot and passengers received fatal injuries sustained as a result of the impact sequence.
Since receiving the toxicology results, the ATSB has:
“During the draft investigation report review process, the aviation medical specialist engaged by the ATSB recommended that carbon monoxide (CO) toxicology testing be undertaken on blood samples of the aircraft occupants that had been taken and suitably stored by the New South Wales State Coroner. This required testing at a specialised laboratory. With results pending, the ATSB draft report was submitted to Directly Involved Parties (DIPs) in December 2019 for comment.
The results of the testing were provided to the ATSB in March 2020, indicating that the pilot and two of the passengers had elevated levels of CO. The ATSB notes that post-mortem examinations established that the pilot and passengers received fatal injuries sustained as a result of the impact sequence.
Since receiving the toxicology results, the ATSB has:
- consulted with New South Wales Health pathology to confirm the integrity of the samples given the preservation method, storage temperature and duration
- consulted with NSW Health forensic toxicology to confirm the accuracy of testing given the technique used and sample preparation
- received independent advice from a forensic pharmacologist, and engaged an experienced independent forensic pathologist to advise on the testing and effects of the CO levels found in the occupants
- undertaken research on CO poisoning and detectors relating to aircraft operations.
Hopefully, final report will detail a more credible path of CO into cabin.
A few points apparent in Interim report:
- Coroner did not test for CO
- Post crash engine inspection did not flag CO leak issue.
- 2 years after crash, having drawn a blank on cause, ATSB tested for CO and found elevated levels in 3 of the 6 cabin occupants, zero in other 3.
- Subsequent engine examination identified cracked exhaust flange at cylinder as CO source. (Leak is into free air, that is propwash, slipstream and would be very much diluted.)
- CO path through fwd firewall into engine bay is not mentioned.
- Path from engine bay into cabin is said to be via missing bolts of magneto access panel. I am not familiar with Beaver, but typically we’re talking 3 x 3/16 bolt holes.
Question then is, is it possible for something nothing CO via broken path to cause elevated levels of CO in such a short, about 7 or 8 minutes, period of engine operation?
A few points apparent in Interim report:
- Coroner did not test for CO
- Post crash engine inspection did not flag CO leak issue.
- 2 years after crash, having drawn a blank on cause, ATSB tested for CO and found elevated levels in 3 of the 6 cabin occupants, zero in other 3.
- Subsequent engine examination identified cracked exhaust flange at cylinder as CO source. (Leak is into free air, that is propwash, slipstream and would be very much diluted.)
- CO path through fwd firewall into engine bay is not mentioned.
- Path from engine bay into cabin is said to be via missing bolts of magneto access panel. I am not familiar with Beaver, but typically we’re talking 3 x 3/16 bolt holes.
Question then is, is it possible for something nothing CO via broken path to cause elevated levels of CO in such a short, about 7 or 8 minutes, period of engine operation?
Air flow through cowlings is sometimes counter-intuitive.
Presumably that was the second flight for the passengers.
Were the passengers inhaling exhaust fumes from passing boats whilst having lunch? Or from the pizza oven?
Just as plausible as the other theories going around!
Just as plausible as the other theories going around!
If (big "IF") the crack in the exhaust that ATSB says was there prior to the accident, was in fact there prior to the accident, the potential for CO respiration would seem as plausible as a passenger knocking the pilot out or Angel Flight-related pressure. But if (big "IF") a crack of that size was, in fact, in the exhaust prior to the accident, what maintenance inspections were done and certified by whom in the previous year or so?
As with the Essendon tragedy, it will probably be the legal action commenced by the NOK etc of the deceased that will be the only effective avenue for the discovery and exposure of the truth.
As with the Essendon tragedy, it will probably be the legal action commenced by the NOK etc of the deceased that will be the only effective avenue for the discovery and exposure of the truth.
" Were the passengers inhaling exhaust fumes from passing boats whilst having lunch? Or from the pizza oven?
Just as plausible as the other theories going around! "
In my new career teaching RPL, PPL, CPL and ATPL theory we do make students very aware of the dangers of Carbon Monoxide poisoning:
CO is very insidious and not easily detected -
"The affinity between hemoglobin and carbon monoxide is approximately 230 times stronger than the affinity between hemoglobin and oxygen so hemoglobin binds to carbon monoxide in preference to oxygen."
If anyone is exposed to CO the most obvious telltale is that lips and fingernails turn bright red.
Smoking, fireplaces, badly maintained gas heaters and FW190s all produce large amounts of CO. (that's apparently why FW190 pilots always wear an oxygen mask)
I have a niece that works at 000 and every winter they process several calls for families suffering from the problem.
Even 100% oxygen for several hours does not always end well for victims. The best solution apparently is to place them in oxygen hyperbaric chambers for many hours.
These are becoming more common in Australia these days as high level athletes and their teams use them to speed recovery from injuries.
Just as plausible as the other theories going around! "
In my new career teaching RPL, PPL, CPL and ATPL theory we do make students very aware of the dangers of Carbon Monoxide poisoning:
CO is very insidious and not easily detected -
"The affinity between hemoglobin and carbon monoxide is approximately 230 times stronger than the affinity between hemoglobin and oxygen so hemoglobin binds to carbon monoxide in preference to oxygen."
If anyone is exposed to CO the most obvious telltale is that lips and fingernails turn bright red.
Smoking, fireplaces, badly maintained gas heaters and FW190s all produce large amounts of CO. (that's apparently why FW190 pilots always wear an oxygen mask)
I have a niece that works at 000 and every winter they process several calls for families suffering from the problem.
Even 100% oxygen for several hours does not always end well for victims. The best solution apparently is to place them in oxygen hyperbaric chambers for many hours.
These are becoming more common in Australia these days as high level athletes and their teams use them to speed recovery from injuries.
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Good to see that investigators are still occasionally able to entertain the possibility that the pilot is not at fault.
And even modern fighters such as the F-22:
https://www.adn.com/bush-pilot/artic...gs/2011/07/22/
https://www.adn.com/bush-pilot/artic...gs/2011/07/22/
Interesting fact - CO has a half life of 5 hours and his was 13% 5 hours after the crash. Broken heat exchanger/exhaust was the culprit
Be careful out there:
https://www.abc.net.au/radio/newsrad...arbon/12452576
https://www.abc.net.au/news/2019-07-...hower/11341744
https://www.abc.net.au/news/2018-10-...eaths/10334098
(On a less serious front, I note a 2008 Cessna 182T advertised in the latest edition of the Aviation Trader has “CO2 detection”. Hopefully it reads a constant 0.04% or thereabouts!)
https://www.abc.net.au/radio/newsrad...arbon/12452576
https://www.abc.net.au/news/2019-07-...hower/11341744
https://www.abc.net.au/news/2018-10-...eaths/10334098
(On a less serious front, I note a 2008 Cessna 182T advertised in the latest edition of the Aviation Trader has “CO2 detection”. Hopefully it reads a constant 0.04% or thereabouts!)
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Ok.
If pax were experiencing CO symptoms on arrival at Cottage Point, it certainly would have dampened their appetite (Bank card statement might show this) and been a topic of conversation. Symptoms of low/moderate CO are headache, dizziness and nausea.
While pax were having lunch, pilot flew 4 x 20 to 30 minutes flights between Rose Bay and the Point. If pilot was flying under the influence of CO, signs would have obvious and a concern to pax. There is no record of pax on these flights suffering any ill effects.
Pilot considered himself fit for flight.
From the above, I think we can reasonably assume CO was not an issue prior to takeoff of fatal flight.
Given the short duration of flight, CO quantity into cabin would need to be substantial to result in ‘elevated levels’ in blood. Elevated level is such that it ‘affected pilot’s ability to control the aircraft’. To put the amount into perspective, it is the equivalent of a car’s undiluted exhaust into the cabin. All 6 people would have similar CO levels, not just 3 of them. They would have become drowsy and then in quick time, unconscious. The pilot would have been subtly incapacitated and unable to put the aircraft into a sudden, steep dive. Similarly for the pax.
Further, the pax in the right front seat, besides feeling the desire to take pics, was able to orient camera normally. This is inconsistent for someone with elevated levels of CO.
So to back up a little:
- Coroner did not suspect or test for CO
- Initial post crash inspection of exhaust did not note any pre-existing defect
- Exhaust path into cabin has not been established
- CO detector showed nil indication.
Many questions.
If pax were experiencing CO symptoms on arrival at Cottage Point, it certainly would have dampened their appetite (Bank card statement might show this) and been a topic of conversation. Symptoms of low/moderate CO are headache, dizziness and nausea.
While pax were having lunch, pilot flew 4 x 20 to 30 minutes flights between Rose Bay and the Point. If pilot was flying under the influence of CO, signs would have obvious and a concern to pax. There is no record of pax on these flights suffering any ill effects.
Pilot considered himself fit for flight.
From the above, I think we can reasonably assume CO was not an issue prior to takeoff of fatal flight.
Given the short duration of flight, CO quantity into cabin would need to be substantial to result in ‘elevated levels’ in blood. Elevated level is such that it ‘affected pilot’s ability to control the aircraft’. To put the amount into perspective, it is the equivalent of a car’s undiluted exhaust into the cabin. All 6 people would have similar CO levels, not just 3 of them. They would have become drowsy and then in quick time, unconscious. The pilot would have been subtly incapacitated and unable to put the aircraft into a sudden, steep dive. Similarly for the pax.
Further, the pax in the right front seat, besides feeling the desire to take pics, was able to orient camera normally. This is inconsistent for someone with elevated levels of CO.
So to back up a little:
- Coroner did not suspect or test for CO
- Initial post crash inspection of exhaust did not note any pre-existing defect
- Exhaust path into cabin has not been established
- CO detector showed nil indication.
Many questions.
Pilot considered himself fit for flight.
The effects of CO are not linear and include impaired decision-making. Non-expert PAX wouldn't notice subtle behavioral telltales of a pilot's deteriorating competence.
- CO detector showed nil indication.
From the above, I think we can reasonably assume CO was not an issue prior to takeoff of fatal flight.
And I note I'm no fan of ATSB, given the frequency with which it produces works of fiction and unhelpful mush.
Last edited by Lead Balloon; 17th Jul 2020 at 11:08.