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DHC Beaver down in Hawkesbury

Old 7th Aug 2020, 03:45
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How do you account then for the CO in the blood samples?
Wild guess: The people with CO in their bloodstreams had been breathing air containing CO? The differing levels were the result of differing air flows through the cabin and differing accumulated times in the cabin of the PIC compared with other POB?


I’m not ‘welded’ to CO as the cause. I’m pleasantly surprised that the ATSB is occasionally capable of entertaining the possibility that the cause of an accident is not PIC stuff up. If you look objectively at the evidence as to the weird and whacky ways in which air flows through aircraft bits and the insidious effects of CO, you don’t have to be Sherlock Holmes to join the dots between a gaping crack in an exhaust pipe and CO levels in the PIC’s bloodstream that had insidious effects on his judgment.

What’s your theory as to the cause/s of the tragedy?
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Old 7th Aug 2020, 12:37
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I've experienced two cylinder head separations on Beavers on Amphib floats. On the second occasion the sickly, sweet smell of AVGAS was very apparent in the cabin until the throttle was retarded to barometric manifold pressure. The windows were closed on both occasions - however in the Beavers that I flew you got wet in rain even with them closed.

So, yes, I do beleive that an exhaust leak could make it's way into the cabin. After reading the report I wonder how elevated my CO levels got at times - the distinctive chugging sound of a leaky exhaust gasket resulted in numerous trips to the hangar.



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Old 28th Aug 2020, 01:13
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Werbil, from your experience we can take it that high volume gas, such as from a separated cylinder at power, will enter cabin via closed windows. And low volume CO, such as from a leaking exhaust gasket (or similar volume from cracked exhaust as with VH-NOO), is not an issue. If you did not experience CO symptoms, appreciable CO did not enter cabin.



After almost 3 years, the ATSB investigation has run its course. The next agency, a fresh pair of eyes, a different angle, will look at the history of the blood samples. Despite ATSB’s through verification, something does not gel. Contamination? Tampering? It can happen. Depending on what unfolds, the circumstances and behaviour of the pax would be the focus. In that regard, the ATSB report poses many questions. For example, why did the front seat pax take 29 mainly uninspiring (from what we see in the report) pics during the 10 minute flight?
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Old 28th Aug 2020, 04:51
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Originally Posted by Wingnuts View Post
For example, why did the front seat pax take 29 mainly uninspiring (from what we see in the report) pics during the 10 minute flight?
Maybe he'd found if you take lots of photos, one sometimes turns out to be a gem?
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Old 29th Jan 2021, 01:41
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Final Report out today 29-Jan-2021
https://www.atsb.gov.au/publications...r/ao-2017-118/

Interesting video also:
https://www.atsb.gov.au/media/news-i...-danger-of-co/
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Old 29th Jan 2021, 04:34
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Video examining this accident and the final report here - youtu.be/gFTeqwxBfg0

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Old 29th Jan 2021, 06:58
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Wow, just Wow!!!!

Blind Freddy can see that the primary cause was a mis-handled escape manoeuvre from flying into a one way valley. Did the ATSB even consider poor pilot judgement and handling.

Maybe (and by a long shot) air contamination might have been a factor.

Very worrying when the ATSB go public with such rubbish!
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Old 29th Jan 2021, 07:15
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Originally Posted by hoss View Post

Blind Freddy can see that the primary cause was a mis-handled escape manoeuvre from flying into a one way valley. Did the ATSB even consider poor pilot judgement and handling.

Maybe (and by a long shot) air contamination might have been a factor.
I was thinking along the same lines earlier, but I realised this.

You're right. The ATSB did consider poor pilot judgement and given that the pilot had flown this trip more than 700+ times before, they started to look deeper as to why he used poor judgement on this occasion. He did indeed make a wrong turn and should have turned hard left at that altitude, or continued to climb and then turn west, but he didn't. Then, low and behold, they dug deeper and found something that could have directly contributed to his poor decision making on that fateful day. Then it turns out that other aircraft may also be affected and thus may save the lives of other pilots and passengers in the future.

Job well done by the ATSB you'd have to say, wouldn't you?

So yes, it was poor pilot judgement. Why? Maybe because of CM, but maybe not, but by uncovering those defects they may have saved other lives by by bringing it to other operators attention.

I was in that area shortly after the crash in my boat and considering options as to why it happened and I can certainly tell you that those valleys really do all look the same and it would be very easy to fly into the wrong one after a minor distraction or a late night out. The part of the report that makes me believe it was CM was that he did not continue to climb when he should have. It should have been a continuous climb, but it didn't happen. That being said, they do climb incredibly slowly out of the area and the takeoff is very long, but that could be SOP by the operator, so if you hadn't witnessed one, the climb-out would look very gradual, highlighted at how the passenger was taking pictures at 100 ft long after the takeoff.
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Old 29th Jan 2021, 08:53
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Imagine the AFP putting out a report saying Man Monis did the Lindt siege because he got ripped off at a 7-11 on the way to Martin Place and they are concentrating their efforts on this!.......

This report is the aviation equivalent.

“700+ times doing this flight”. Comfort and complacency spring to mind, I know what I was like after a solid decade flying in GA.I felt almost bulletproof and this reflected in the stupid things that I did. (Human Factors)

Another related and important question should be what was the motivation for the 270 degree turn? The proficienct pilot knew that flying straight ahead out of the river would be the safest course. Was it a case of extra sightseeing, a fly-by etc. Perhaps this may have been performed successfully many times before at lighter weights. The alignment on the southern side of the river, the level off and build up of airspeed, the aircraft configuration all suggest to me a coherent and deliberate manoeuvre!

I have no horse in this race, it just sucks to see the ATSB and news outlets trying to go after the operator and maintenance organisations. That’s all.

Last edited by hoss; 29th Jan 2021 at 21:18.
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Old 29th Jan 2021, 09:43
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So I guess what you’re saying is that if it was directly blaming the pilot, case closed?

If it was CM poisoning, then I’m assuming you hit the operator and maintenance guy.

Wouldn’t the operator still be liable if the pilot was proven to have done what you suggest? Genuine question...

I have sat under that flight path and area for days on end as the kids swim at the beaches and they always do the same thing and seem to follow the exact same route. Not saying it didn’t happen, but you’d hope that someone would have mentioned this as it’s a high profile area.

Your scenario certainly does have logic with it and aligns 100% at my comments around the valleys all looking the same. Very hard to distinguish.
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Old 29th Jan 2021, 10:38
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I find it difficult to believe that with all the old Beavers flying throughout the world, that the stars suddenly aligned on this one day for VH-NOO?
Never happened to any other Beaver anywhere that we know of. ATSB would have checked that?


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Old 29th Jan 2021, 13:27
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I find it difficult to believe that with all the old Beavers flying throughout the world, that the stars suddenly aligned on this one day for VH-NOO?
It may not happen for years that all the holes line up.
But when they do accidents happens....




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Old 5th Feb 2021, 00:07
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Old 5th Feb 2021, 00:26
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I see they have made the blame game public.

It would be interesting to see how it affects pilots in reality in a simulation, although it could harm your health.

I remember early in my training the CPL students went up together in a 182 where the pilot had oxygen and the pax didn’t and they had them performing a series of simple and complex mathematical equations above 10,000ft. The results were worse that expected and they were all surprised at the cognitive degradation at altitudes not considered to be able to affect you.

I’m not sure if they do that type of thing these days, too many safety management systems blocking the old school learning techniques!
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Old 5th Feb 2021, 03:19
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Beavers are an unforgiving aircraft when stalled with a heavy load.
A climb out with flap being retracted after take off which would have been considerable to get out of the water at that load. Leaving the flap movement lever in the up position is a bad habit after retracting flap.
If the aircraft still had climb flap or more out and a steep turn attempted then if flap was pumped to tighten the turn radius (Common practice in a Beaver) with the flap movement lever in the up position then the aircraft would have departed from controlled flight abruptly.
The Beaver in normal configuration has two levers, one controlled the direction of movement, the other pumps the hydraulic pump for flap movement either being up or down depending on where the smaller lever is positioned.
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Old 5th Feb 2021, 21:15
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Great information, now we’re getting closer to the truth.
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Old 12th Feb 2021, 03:41
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One of half a dozen or so contributing factors in the report was:

• A 27 minute taxi before the passengers boarded, with the pilot’s door ajar likely exacerbated the pilot’s elevated carboxyhaemoglobin level.

Not in previous reports, it is a new factor. Does its inclusion indicate an acceptance that the CO in cabin via 3×3/16 holes factor will not stand alone?

Is it credible?

The report states it is not a Beaver cabin cooling technique to taxi with door ajar and there are no witness (operator, fellow pilots, pax on earlier flts) statements to verify it was peculiar to NOO’s pilot.

When the pilot opened his door and smelt exhaust fumes, would he not have shut the door? He’d be thinking CO, maybe a cracked cylinder head, do I go ahead with take off at near max weight?

From the report:

Operator observations of pilot’s approach to safety

The operator’s Chief Pilot stated that the pilot had good aircraft handling skills and was conservative with his decision-making. A previous Chief Pilot for the operator also indicated that, while he had not flown with the pilot, he was a reliable, steady operator who did not take risks, and had a very strong attitude to safety. The pilot was described by his work colleagues as being:
  • very diligent and methodical
  • very meticulous, always correcting small things
  • a safe pilot who had all the experience behind him; he had no issues with grounding an aircraft and was safety ‘conscientious’.

It would have been uncharacteristic for him to risk it, flown, and not contact the company to let them know there was a problem as he did earlier in the day re a 150 mag drop. (limit 100)

There are no eyewitnesses to confirm door ajar but there are three pics that claim to show the door open as such. (Figure 16)

The top and bottom pics are from a distance, unclear, and at best are inconclusive. The middle pic is taken from inside showing a top edge gap between door and frame. The gap is even along its whole length, not at a widening angle from hinge line aft as you would expect. The gap is parallel as in another internal pic (Fig 6) where door is closed.

An open and shut case.




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Old 12th Feb 2021, 06:58
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When the pilot opened his door and smelt exhaust fumes, would he not have shut the door? He’d be thinking CO, maybe a cracked cylinder head, do I go ahead with take off at near max weight?
Co2, otherwise known as the silent killer, colourless, odourless and tasteless.
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Old 12th Feb 2021, 07:55
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Originally Posted by Squawk7700 View Post
Co2, otherwise known as the silent killer, colourless, odourless and tasteless.
CO not Co2
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Old 12th Feb 2021, 23:22
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Engine exhaust is not odourless or necessarily colourless. It contains numerous gasses including both odourless, the carbons, and pungent, the nitrides and sulphides. The latter are the tell-tale smell for the odourless. Exhaust might also have dark smoke due too rich and/or blue smoke due oil burn. Fume smell is more noticeable in old tech engines compared to modern engines due more efficient burning and catalyst converter. Exhaust gas only becomes dangerous if characteristic smell is not acted on.
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