BA 787 Nosewheel collapse @ LHR
H Peacock
Or, to bring the perspective from 1951 to 2021, if the possibility of a gear pin wrongly fitted was known about and indeed publicised, there’s not much of an excuse for it still to be physically possible to fit the pin in the wrong hole?
Humans are intriguing creatures, both under pressure and on a forum...
Or, to bring the perspective from 1951 to 2021, if the possibility of a gear pin wrongly fitted was known about and indeed publicised, there’s not much of an excuse for it still to be physically possible to fit the pin in the wrong hole?
Humans are intriguing creatures, both under pressure and on a forum...
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This should be required reading for any engineer or designer.. originally from the late 1980s, current edition is 2011 I think. Clearly still relevant and strongly recommended. Originally published as "the PSYCHOLOGY of everyday things". Covers exactly the type of design issues that allow people to misinterpret what is intended and/or should be done, such as putting a pin in the wrong hole.
Last edited by slast; 21st Jun 2021 at 13:51.
krismiler
Ansett had the same thing happen in about 2000. A Boeing 767 sitting on a Bay at Sydney Domestic Terminal. The nose gear retracted as a test by an Engineer but no locking pin was present on the NLG so it did what it was designed to do and retracted. Ansett had several incidents and seemed to have a problem with nose gear - 747-312 on arrival at Sydney in 1994 with nose gear retracted. Qantas ended up having to jack it up and tow it for them. Another incident, less well known, failure of Engineer to chock a 767 again at Sydney Domestic Ansett Terminal, aircraft rolled forward and the radome collided with the nose in guidance system box requiring replacement. People wonder why their 767 fleet was grounded a year or so before their eventual collapse following 9/11.
Ansett had the same thing happen in about 2000. A Boeing 767 sitting on a Bay at Sydney Domestic Terminal. The nose gear retracted as a test by an Engineer but no locking pin was present on the NLG so it did what it was designed to do and retracted. Ansett had several incidents and seemed to have a problem with nose gear - 747-312 on arrival at Sydney in 1994 with nose gear retracted. Qantas ended up having to jack it up and tow it for them. Another incident, less well known, failure of Engineer to chock a 767 again at Sydney Domestic Ansett Terminal, aircraft rolled forward and the radome collided with the nose in guidance system box requiring replacement. People wonder why their 767 fleet was grounded a year or so before their eventual collapse following 9/11.
H Peacock
I can imagine a number of possibilities:
Publicising the issue does not mean that everybody has read the published document. Those who signed that they had read it might NOT have read it, or they signed but did mot understand or think about the significance, or forgot about it after a month or so.
A very junior engineer might have been told to insert the pin, and got it wrong.
A non-787 engineer, helping out his mates who had a high workload, might have got it wrong.
The tug driver, or another non-engineer ramp worker might have inserted the pin and put it in the wrong hole.
An engineer, asked to check all the pins were in before the test might have seen the pin flag and thought the pin was in - they might not have gone right up to it to check the pin was actually in the correct hole.
Sadly, I don't think that in these days of reduced training and costs that we can assume that everyone - even pilots and engineers - necessarily understand simple physics, nor that everyone can see and understand by looking, how a series of undercarriage struts and levers work.
As a pilot, I was never shown where to fit the locking pins on any of the 7 commercial passenger aircraft types I have flown. Yes, it might be written in the FCOM, but you can't beat actually being shown stuff on the actual aircraft. Have all engineers and tow crews been actually shown exactly where to fit the pins?
It should not be physically possible to insert a ground-lock pin in the wrong hole. If it is, that is very poor design, because with the best will in the World, if something mechanical can be done wrong, it eventually will be.
Engineers only have mandatory duplicate inspections on certain items, such as engine oil caps.
I can imagine a number of possibilities:
Publicising the issue does not mean that everybody has read the published document. Those who signed that they had read it might NOT have read it, or they signed but did mot understand or think about the significance, or forgot about it after a month or so.
A very junior engineer might have been told to insert the pin, and got it wrong.
A non-787 engineer, helping out his mates who had a high workload, might have got it wrong.
The tug driver, or another non-engineer ramp worker might have inserted the pin and put it in the wrong hole.
An engineer, asked to check all the pins were in before the test might have seen the pin flag and thought the pin was in - they might not have gone right up to it to check the pin was actually in the correct hole.
Sadly, I don't think that in these days of reduced training and costs that we can assume that everyone - even pilots and engineers - necessarily understand simple physics, nor that everyone can see and understand by looking, how a series of undercarriage struts and levers work.
As a pilot, I was never shown where to fit the locking pins on any of the 7 commercial passenger aircraft types I have flown. Yes, it might be written in the FCOM, but you can't beat actually being shown stuff on the actual aircraft. Have all engineers and tow crews been actually shown exactly where to fit the pins?
It should not be physically possible to insert a ground-lock pin in the wrong hole. If it is, that is very poor design, because with the best will in the World, if something mechanical can be done wrong, it eventually will be.
Engineers only have mandatory duplicate inspections on certain items, such as engine oil caps.
Only half a speed-brake
I would assume, yes. All the tow crews and engineers who are responsible for towing aircraft actually have been shown where the pins go.
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Some many years ago, on one of my types, could have been an L1011, there was an incident caused by a hydraulic leak across the ports in a component which caused the NLG downlock to pressurise to unlock. Of course, for all I know the B787, could be an electrical unlock actuator, as the pin flag in the picture #29, masks the area.
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[Pax]. Looking at the photo in post #22 with the benefit of extensive hindsight, it seems a bit odd that the correct hole was not marked in any way. A red outline around it wouldn't have hurt. In fact, wonder why all such holes aren't marked in some standard way across the industry. Would also visually highlight if a pin wasn't fitted.
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We'll all know very soon if it was no pin at all, or wrong hole.
I rather hope the mistake is the former, because if it was the latter;
What a sorry tale of errors that would be.
Boeing... Presumably knew about the risk, but didn't push it out LOUD enough.
FAA..... As above, but even worse being they are the regulator.
Operator.... Well....It's troubled and disrupted times (Covid) with reduced staffing,
changing roles needed, etc, and all the holes line up in the cheese.
Bottom line, this event may well have hurt or worse, ground staff, and shows
that even ground handling threats should never be taken lightly.
I rather hope the mistake is the former, because if it was the latter;
What a sorry tale of errors that would be.
Boeing... Presumably knew about the risk, but didn't push it out LOUD enough.
FAA..... As above, but even worse being they are the regulator.
Operator.... Well....It's troubled and disrupted times (Covid) with reduced staffing,
changing roles needed, etc, and all the holes line up in the cheese.
Bottom line, this event may well have hurt or worse, ground staff, and shows
that even ground handling threats should never be taken lightly.
Last edited by Deepinsider; 22nd Jun 2021 at 12:09.
Deepinsider
"We'll all know very soon if it was no pin at all, or wrong hole."
There's a third possible scenario, alluded to in post #7. I've never heard of it happening, but it clearly has, so it might be unwise to rule it out yet.
"We'll all know very soon if it was no pin at all, or wrong hole."
There's a third possible scenario, alluded to in post #7. I've never heard of it happening, but it clearly has, so it might be unwise to rule it out yet.
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Technically the gear didn’t collapse. The gear retracted weight on wheels. The damping in the retraction actuator slows the rate that the aircraft drops. This has the unfortunate effect of generating immense forces into the NLG and retraction actuator attachment, risking punching the actuator through the NLG box before the actuator fails through over pressure.
Busbert
"Technically the gear didn’t collapse. The gear retracted weight on wheels. The damping in the retraction actuator slows the rate that the aircraft drops. This has the unfortunate effect of generating immense forces into the NLG and retraction actuator attachment, risking punching the actuator through the NLG box before the actuator fails through over pressure."
I think it's reasonable to infer from the fact that the aircraft was towed off the stand a day or two after the incident, supported on all 3 gears, that there hadn't been any significant internal structural damage.
"Technically the gear didn’t collapse. The gear retracted weight on wheels. The damping in the retraction actuator slows the rate that the aircraft drops. This has the unfortunate effect of generating immense forces into the NLG and retraction actuator attachment, risking punching the actuator through the NLG box before the actuator fails through over pressure."
I think it's reasonable to infer from the fact that the aircraft was towed off the stand a day or two after the incident, supported on all 3 gears, that there hadn't been any significant internal structural damage.
