Aircraft down at Braidwood, NSW
Read the ATSB report. The dangers and illusions of low level flight and associated illusions that likely lead to LOC-I are covered in detail.
oh, wait,
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oh, wait,
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Have read the ATSB report and have studied Human Factors, Threat and Error Management, discussed illusions, read lots about that as well. The nature of this accident can't 100% 'rule in' illusion causing it, it can't 100% rule it out either. But it's real.
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that other post mentioned ‘defined minimum manoeuvring speed’ which is a totally different concept
Indeed, Dave. However, when I ran a search for DMMS (a term which I had never encountered before) the hit provided both Va and Vs related considerations. I get the impression that DMMS is a term coined by the lightie fraternity in the US ? The DMMS, being a simple load factor increment to Vs still is a bit silly without any margins being applied. I note that a similar idea is used on heavies for manoeuvring margins, but with a sensible stall pad.
Indeed, Dave. However, when I ran a search for DMMS (a term which I had never encountered before) the hit provided both Va and Vs related considerations. I get the impression that DMMS is a term coined by the lightie fraternity in the US ? The DMMS, being a simple load factor increment to Vs still is a bit silly without any margins being applied. I note that a similar idea is used on heavies for manoeuvring margins, but with a sensible stall pad.
Bodie - I don't need convincing that it's real. Read my 2nd post above.
In this report, the ATSB has completely ignored the issues and illusions in turns at low level. Instead they've just given a vacuous paragraph saying that training is involved for low level flights and shouldn't otherwise be done and simply given an aeronautical outline of what a stall is under the "Additional Information" Chapter.
Now there is no 100% proof that any of the low levels illusions caught out this pilot. That can, sadly for obvious reasons, never be proven. But look at what he was doing and where he stalled. If it walks like a duck, and talks like a duck it should be at least discussed as a possible causal factor, not just swept under the carpet to ignore. And look at the temporary airspeed decrease during the turn from downwind to upwind. More evidence of being affected by the illusions in the turn.
Further to my FAA link above - have a good read of a similar accident from the Canadian TSB in nil wind. Look at the issues in 1.18. https://www.tsb.gc.ca/eng/rapports-r...0/a15q0120.htm Compare and contrast the thoroughness of the report to the ATSB one.
Transport Canada devote 4 pages of its Flight Instructor Manual to the illusions of low level flight, including diagrams and lesson plans. It's the lesson before Prec Searches.
CASA's FIM, by contrast, has 1 paragraph on briefing the student on optical illusions in turns during a precautionary search and landing.
Finally, has anyone worked out how the additional risk in the accident was the overdue oil change?
In this report, the ATSB has completely ignored the issues and illusions in turns at low level. Instead they've just given a vacuous paragraph saying that training is involved for low level flights and shouldn't otherwise be done and simply given an aeronautical outline of what a stall is under the "Additional Information" Chapter.
Now there is no 100% proof that any of the low levels illusions caught out this pilot. That can, sadly for obvious reasons, never be proven. But look at what he was doing and where he stalled. If it walks like a duck, and talks like a duck it should be at least discussed as a possible causal factor, not just swept under the carpet to ignore. And look at the temporary airspeed decrease during the turn from downwind to upwind. More evidence of being affected by the illusions in the turn.
Further to my FAA link above - have a good read of a similar accident from the Canadian TSB in nil wind. Look at the issues in 1.18. https://www.tsb.gc.ca/eng/rapports-r...0/a15q0120.htm Compare and contrast the thoroughness of the report to the ATSB one.
Transport Canada devote 4 pages of its Flight Instructor Manual to the illusions of low level flight, including diagrams and lesson plans. It's the lesson before Prec Searches.
CASA's FIM, by contrast, has 1 paragraph on briefing the student on optical illusions in turns during a precautionary search and landing.
Finally, has anyone worked out how the additional risk in the accident was the overdue oil change?
Last edited by compressor stall; 29th Nov 2020 at 01:25.
[H]as anyone worked out how the additional risk in the accident was the overdue oil change?
Man Bilong Balus long PNG
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The stall speed of a piston-engined aircraft increases by 1 knot for each hour the engine is overdue for an oil change
At least the pilot doesn’t appear to have been show-boating. Just a fun day out with mates that ended badly. If he was showing off, it would have been closer to 50 knots faster. Sad considering a fairly high number of hours on type and a lot of recent hours.
My point being, it sounds like his mate had landed prior, phoned him up and cautiously said not to land. Pilot continues on and circles overhead waiting for his mate to take off again. We’ve all done that before haven’t we? Continues to fly overhead, probably looking at the ground with only 15-20 degrees angle of bank.
Lack of some concentration and the speed gets a bit low and down he goes down in the turn.
He wasn’t hitting a power line at the back of the pub at Bourke doing 140 knots at 30 feet....
I used to own a Libety XL2, same aircraft exactly and it runs a very thin wing profile that takes a solid amount of airspeed to get it flying. When it lets go, it doesn’t mess about and it drops hard onto the runway at the stall.
Lack of some concentration and the speed gets a bit low and down he goes down in the turn.
He wasn’t hitting a power line at the back of the pub at Bourke doing 140 knots at 30 feet....
I used to own a Libety XL2, same aircraft exactly and it runs a very thin wing profile that takes a solid amount of airspeed to get it flying. When it lets go, it doesn’t mess about and it drops hard onto the runway at the stall.
It's the lesson before Prec Searches.
CASA's FIM, by contrast, has 1 paragraph on briefing the student on optical illusions in turns during a precautionary search and landing.
CASA's FIM, by contrast, has 1 paragraph on briefing the student on optical illusions in turns during a precautionary search and landing.
Man Bilong Balus long PNG
Join Date: Apr 2002
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there was a specific low flying illusion lesson before prec search.
And when I commenced the training required for the low level endorsement to carry out bird scaring ops at the end of '90, the lesson quoted above was really hammered into me! (Thanks DD, if you read this.)
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When I was instructing back in 1988, there was a specific low flying illusion lesson before prec search.
I still have the notes from my original rating, covered extensively and part of a flight lesson.
