The Pacific: General Aviation & Questions The place for students, instructors and charter guys in Oz, NZ and the rest of Oceania.

DHC Beaver down in Hawkesbury

Old 18th Jul 2020, 11:40
  #361 (permalink)  
 
Join Date: Nov 2001
Location: Australia/India
Posts: 3,276
Question without notice, Wingnuts: Did you have any direct or indirect involvement in the maintenance of the accident aircraft (registered as VH-NOO when the accident occurred) or then or now have any direct or indirect financial interest that would be affected by the cause/s of the accident? I declare that I don't.
Lead Balloon is offline  
Old 18th Jul 2020, 23:26
  #362 (permalink)  
 
Join Date: Apr 2005
Location: Melbourne
Posts: 2,782
For those that have been in a Beaver, what’s the airflow like in there, are they nice and air tight or does the wind blow in around the doors etc being such an old aircraft?

Comparing to say a Cirrus where their only airflow is via the vents on the dash.
Squawk7700 is offline  
Old 19th Jul 2020, 01:26
  #363 (permalink)  
 
Join Date: Dec 2006
Location: Gold Coast
Posts: 21
Having over 6000 hrs in Beavers on Floats, a few years in hangers in the states maintaining them, an ex chief pilot in Sydney well before Sydney Seaplanes and then obviously been involved in the Cottage Point lunch flights many times, I am at loss to put any credence on the Carbon Monoxide theory. The construction of a Beaver has a very loose cowl fitting which gives an approximate fist size gap around approx 90% of the cowl and the airframe. All Beaver pilots I have flown with taxi with the pilot window down to keep fresh cool air circulating in the cabin. In most cases the pax window is down also. Being the time of day and the time of year I suspect both windows would have been wide open. With the take of direction the aircraft would have been taxied into wind with the occasional turn cross stream so as to avoid taxiing down wind. Down wind Taxi on water destroys propellers. There may have been a 360 turn or two involved so as not to extend the departure point too far east., but in any case there would be a very significant flow of fresh air in the cabin. A few holes in the firewall to allow CO into the cabin in sufficient volume to affect the pilot and passengers to me sounds extremely unlikely. BR
Beavers rule is offline  
Old 19th Jul 2020, 03:16
  #364 (permalink)  
 
Join Date: Sep 2002
Location: Australia
Posts: 1,025
Not ruling anything out, but I used to fly a machine that, when you hit the "smoker", it would fill the cockpit with smoke.

This was a pretty fair visible indication that whatever was leaving the RHS exhaust stack was heading in abundance into the cockpit.

That said, for anything to find its way in there must be something finding its way out.
currawong is online now  
Old 19th Jul 2020, 03:41
  #365 (permalink)  
 
Join Date: Apr 2005
Location: Melbourne
Posts: 2,782
Originally Posted by currawong View Post
Not ruling anything out, but I used to fly a machine that, when you hit the "smoker", it would fill the cockpit with smoke.

This was a pretty fair visible indication that whatever was leaving the RHS exhaust stack was heading in abundance into the cockpit.

That said, for anything to find its way in there must be something finding its way out.
I have a smoker on my aircraft and the smoke comes out the exhaust which is below the fuselage. It’s possible that some comes out the injector in to the manifold and as a result the cockpit fills with some smoke when using it. Makes you seriously wonder what else is getting in there too.
Squawk7700 is offline  
Old 19th Jul 2020, 09:49
  #366 (permalink)  
 
Join Date: Nov 2001
Location: Australia/India
Posts: 3,276
As I noted earlier, airflow through cowlings can be counter-intuitive. The APS folk put cotton tufts and a camera under the hood of a Bonanza and discovered that, on a serviceable aircraft in the cruise, the air entered the outboard sides of the cowl openings and lots did a lap of the engine bay then exited forward through the inboard sides of those openings.

That data explained why an engine oil leak results in oil on the windscreen- at least on that aircraft and ones with similar cowl airflow ‘dynamics’.

Think about that: air flow both in and out of the same cowl opening. I say ‘opening’ rather than ‘inlet’, the latter of which is the label resulting from the intuitive belief that all air comes in the ‘front’ (the ‘inlets’) of the engine cowling and flows rear wards then exits somewhere different.

When there are cracks in exhaust plumbing and holes in the engine bay that shouldn’t be there, who knows where gasses may be flowing, absent some tuft/camera data to show what’s really happening?

And as I also noted earlier, if you think that the cabin windows/cockpit doors being wide open reduces the risk of potentially hazardous levels of CO in the cabin, my experience (with a reliable CO detector) is the opposite. But it did depend on a number of factors like wind direction/speed. The CO reading went to zero once all the windows/doors were closed and the aircraft was flying. The short term on-ground exposure to CO in a serviceable aircraft was evidently not deleterious. But who knows what could happen with repeated exposure during repeated short duration ops combined with with defects in the engine bay? The science shows that CO is very ‘sticky’ in the bloodstream.

Who knows what happened in this case. At least somebody’s entertaining the possibility that it’s not all the pilot’s fault.
Lead Balloon is offline  
Old 24th Jul 2020, 01:31
  #367 (permalink)  
 
Join Date: Jul 2003
Location: Yorkey's Knob
Posts: 113
Originally Posted by Lead Balloon View Post
Question without notice, Wingnuts: Did you have any direct or indirect involvement in the maintenance of the accident aircraft (registered as VH-NOO when the accident occurred) or then or now have any direct or indirect financial interest that would be affected by the cause/s of the accident? I declare that I don't.
No. Sorry I can't help you with that. My interest is simply that of an armchair amateur. But enough about me and back on topic. One of several anomalies with the CO theory is that there is no correlation between CO exposure and CO blood levels. Hopefully, the Bureau will not dig themselves a hole on this. After almost 3 years, the time must be approaching for them to clear the aircraft and its operation, and pass the investigation to the next phase, which is the examination of the non aviation aspects. I suspect that's where the answers will be found.
Wingnuts is offline  
Old 24th Jul 2020, 02:52
  #368 (permalink)  
 
Join Date: Nov 2001
Location: Australia/India
Posts: 3,276
[T]here is no correlation between CO exposure and CO blood levels.
That assertion strikes me with the force of novelty. Can you provide any links to any authoritative support for that assertion?
Lead Balloon is offline  
Old 25th Jul 2020, 21:12
  #369 (permalink)  
 
Join Date: Jul 2005
Location: Earth
Posts: 209
Getting pax onto a seaplane and slipping mooring lines requires nifty footwork and if the pilot was affected by exposure from prior flights or burning pizzas then it would have been obvious at that stage. My question to any aviation med people (or even doctors who like carbon monoxide cases) is whether or not symptoms and debilitation are in direct proportion to blood CO content, ie., can you get a 'safe amount' of blood CO beyond which things begin to fall apart ?
The Wawa Zone is offline  
Old 26th Jul 2020, 06:02
  #370 (permalink)  
 
Join Date: Mar 2008
Location: Richmond NSW
Posts: 1,288
Originally Posted by The Wawa Zone View Post
Getting pax onto a seaplane and slipping mooring lines requires nifty footwork and if the pilot was affected by exposure from prior flights or burning pizzas then it would have been obvious at that stage. My question to any aviation med people (or even doctors who like carbon monoxide cases) is whether or not symptoms and debilitation are in direct proportion to blood CO content, ie., can you get a 'safe amount' of blood CO beyond which things begin to fall apart ?
Rest assured, the menus at the Cottage Point Inn are far more posh than to offer pizza.
gerry111 is offline  
Old 27th Jul 2020, 07:31
  #371 (permalink)  
 
Join Date: May 2017
Location: melbourne australia
Posts: 20
If carbon monoxide is the cause then, If a side window was opened for the camera, that would lower cabin pressure, which would increased air flow from the engine holes.
When I flew a Beaver 50 years ago, I was told not to open cockpit side window in flight if possible. Due to possible carbon monoxide leaks.
georgetw is offline  
Old 31st Jul 2020, 00:23
  #372 (permalink)  
 
Join Date: Jul 2003
Location: Yorkey's Knob
Posts: 113
Originally Posted by Lead Balloon View Post
That assertion strikes me with the force of novelty. Can you provide any links to any authoritative support for that assertion?
Referring to the ATSB report, on the day:

- pilot exposure about 2hr 20min, resulted in CO ‘elevated level’

- pax x 2 exposure about 40min, resulted in same CO ‘elevated level’

- pax x 3 exposure same 40min, resulted in nil CO

No need for ‘authoritative support’ on this one. Even Blind Freddie can see the dots don’t join up.
Wingnuts is offline  
Old 31st Jul 2020, 08:13
  #373 (permalink)  
 
Join Date: Nov 2001
Location: Australia/India
Posts: 3,276
You're assuming that the sources, contents and volumes of airflow to which each of the POB were exposed were exactly the same. Blind Freddie wouldn't make that assumption.

Is your insurer getting nervous, Wingnuts?
Lead Balloon is offline  
Old 2nd Aug 2020, 07:28
  #374 (permalink)  
 
Join Date: May 2002
Location: GC Paradise
Posts: 1,049
Investigation number:
AO-2017-118

1. "From this, the ATSB considers the levels of CO detected were likely to have adversely affected the pilot’s ability to control the aircraft during the flight."
2. "From the above activities, the ATSB found pre‑existing cracking of the engine exhaust collector-ring, which could lead to exhaust leakage into the engine bay."
3. "Further, the ATSB found a breach in the firewall from missing bolts used to secure magneto access panels in the firewall under the instrument panel in the cabin."
(my bold text)


It seems a pretty much open and shut case?



Evidence of the gas leak provided by Australian Transport Safety Bureau. Credit: Australian Transport Safety Bureau
(From 7news report)



FlexibleResponse is offline  
Old 3rd Aug 2020, 10:02
  #375 (permalink)  
 
Join Date: Sep 2007
Location: nz
Posts: 132
Originally Posted by FlexibleResponse View Post
Investigation number:
AO-2017-118

1. "From this, the ATSB considers the levels of CO detected were likely to have adversely affected the pilot’s ability to control the aircraft during the flight."
2. "From the above activities, the ATSB found pre‑existing cracking of the engine exhaust collector-ring, which could lead to exhaust leakage into the engine bay."
3. "Further, the ATSB found a breach in the firewall from missing bolts used to secure magneto access panels in the firewall under the instrument panel in the cabin."
(my bold text)


It seems a pretty much open and shut case?



Evidence of the gas leak provided by Australian Transport Safety Bureau. Credit: Australian Transport Safety Bureau
(From 7news report)
Could you possibly show us a photo of the "breach in the firewall from missing bolts used to secure magneto access panels in the firewall". In particular, what sized "bolts" they are referring to?
Far from an open and shut case I would have thought?
Weheka is offline  
Old 4th Aug 2020, 10:25
  #376 (permalink)  
 
Join Date: Jan 2009
Location: Cab of a Freight Train
Age: 37
Posts: 613
Originally Posted by Weheka View Post
Could you possibly show us a photo of the "breach in the firewall from missing bolts used to secure magneto access panels in the firewall". In particular, what sized "bolts" they are referring to?
Far from an open and shut case I would have thought?
Took me a while to find the photo used, but it's from this Safety Advisory Notice (*.PDF format). I have't found any images of the firewall or similar the only reference being:
Originally Posted by The ATSB
In addition, three out of eight bolts used to secure the magneto access panels in the firewall under the instrument panel in the cabin were also found to be missing. Any breach in the firewall can allow gases to enter the cabin from the engine bay.
KRviator is offline  
Old 7th Aug 2020, 00:50
  #377 (permalink)  
 
Join Date: Jul 2003
Location: Yorkey's Knob
Posts: 113
[QUOTE=FlexibleResponse;10851324]Investigation number:
AO-2017-118

1. "From this, the ATSB considers the levels of CO detected were likely to have adversely affected the pilot’s ability to control the aircraft during the flight."
2. "From the above activities, the ATSB found pre‑existing cracking of the engine exhaust collector-ring, which could lead to exhaust leakage into the engine bay."
3. "Further, the ATSB found a breach in the firewall from missing bolts used to secure magneto access panels in the firewall under the instrument panel in the cabin."
(my bold text)


It seems a pretty much open and shut case?"

Open and shut case? Your faith in investigative agencies is somewhat stronger than mine. A claim made by a report is not koran.

1. The pilot’s ability to takeoff and manoeuvre at low altitude is not consistent with being ‘adversely affected’.

- The sudden, nose dive is not consistent with elevated levels of CO. Relaxation, unconsciousness are usual.

2. The initial post crash exhaust examination did not detect a preexisting crack. That became apparent 2 years later when the CO theory was put forward.

3. The 3 hole breach in the firewall, also not noted in initial inspection, is insignificant. Besides, flow through holes would be forward from cabin into engine bay due to the low pressure induced by airflow over engine bay cowling.

What appears to have happened here is that a cause of crash has been latched onto and then reverse engineered the evidence to support. Normally, the evidence is gathered and then a deduction is made.


Wingnuts is offline  
Old 7th Aug 2020, 00:54
  #378 (permalink)  
 
Join Date: Jul 2003
Location: Yorkey's Knob
Posts: 113
Originally Posted by Lead Balloon View Post
You're assuming that the sources, contents and volumes of airflow to which each of the POB were exposed were exactly the same. Blind Freddie wouldn't make that assumption.

Is your insurer getting nervous, Wingnuts?
‘Insurer nervous?’ Not sure what you are assuming here. A more relevant question would be, ‘How do you account then for the CO in the blood samples?’ After all, that’s the report’s smoking gun and the basis of the CO assertion you are welded to.
Wingnuts is offline  
Old 7th Aug 2020, 03:45
  #379 (permalink)  
 
Join Date: Nov 2001
Location: Australia/India
Posts: 3,276
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?
Lead Balloon is offline  
Old 7th Aug 2020, 12:37
  #380 (permalink)  
 
Join Date: Feb 2007
Location: Darwin, Australia
Age: 50
Posts: 398
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.



werbil is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.