LH engineer seriously injured at MAN 13th Nov
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Another tragic accident....and some very uniformed comment as to the maintenance procedures with regard to tyre inflation.
As ever on this site, speculation with regard to the causal factors is rife.
So, let's try and take a more realistic overview of the possible causes shall we.
From the information so far, it can be assumed the aircraft was not on a T/R and therefore the tyre px would be cold and were being recorded as part of an A/F. Possibly they were within the min / max px values but towards the lower end and therefore needed to be adjusted as there would be no other reason to inflate an in-situ tyre. So far, so routine..unless the wheel was being changed for whatever reason...ie a new bay serviced item was being fitted to the a/c in which case it would need to be inflated from storage and / or transportation px ....thus it would be a new assembly and would / should have been subjected to a rigourous testing and inspection procedure anyway ..and at this point we simply do not know the circumstances applicable, the point being that both scenarios offer different possibilities as to why the incident occurred.
Tyres however, do not simply "let go" at random. So far, nobody has mentiond the possible condition of the tyre....such as any one of the following:
Embedded object
Deep cut
Bulge
Tread seperation
To name but four possible other contributory factors.
The classical and invariably tragic bar / psi confusion has been mentioned of
course as has the possibility of a failure of the retaining bolts or hub.
As for a cage on a Line station, maybe, maybe not depending on the operator....however....it would be highly unlikely that even with a cage, for routine adjustment of tyre px, the wheel assy, would be removed, placed in a cage, inflated, and then re-fitted given that the adjustment px is only ever going to be a small value. Inflation from transportation / storage is another matter however.
G-SCAW....whatever you do for a living, one thing's for certain, you are not an engineer !...but thank you for your first paragraph in Post 5....most "entertaining"....
...and for your info, oxygen bottles are usually charged to around 1800psi on an aircraft.
Along with everybody else, I wish the individual concerned a full recovery....however...and has invariably been the case within aviation, the incident offers yet another safety awareness exemplification with regard to procedures and practices and from my perspective, a more than valid one.
The official report on the incident will therefore make interesting reading.
As ever on this site, speculation with regard to the causal factors is rife.
So, let's try and take a more realistic overview of the possible causes shall we.
From the information so far, it can be assumed the aircraft was not on a T/R and therefore the tyre px would be cold and were being recorded as part of an A/F. Possibly they were within the min / max px values but towards the lower end and therefore needed to be adjusted as there would be no other reason to inflate an in-situ tyre. So far, so routine..unless the wheel was being changed for whatever reason...ie a new bay serviced item was being fitted to the a/c in which case it would need to be inflated from storage and / or transportation px ....thus it would be a new assembly and would / should have been subjected to a rigourous testing and inspection procedure anyway ..and at this point we simply do not know the circumstances applicable, the point being that both scenarios offer different possibilities as to why the incident occurred.
Tyres however, do not simply "let go" at random. So far, nobody has mentiond the possible condition of the tyre....such as any one of the following:
Embedded object
Deep cut
Bulge
Tread seperation
To name but four possible other contributory factors.
The classical and invariably tragic bar / psi confusion has been mentioned of
course as has the possibility of a failure of the retaining bolts or hub.
As for a cage on a Line station, maybe, maybe not depending on the operator....however....it would be highly unlikely that even with a cage, for routine adjustment of tyre px, the wheel assy, would be removed, placed in a cage, inflated, and then re-fitted given that the adjustment px is only ever going to be a small value. Inflation from transportation / storage is another matter however.
G-SCAW....whatever you do for a living, one thing's for certain, you are not an engineer !...but thank you for your first paragraph in Post 5....most "entertaining"....
...and for your info, oxygen bottles are usually charged to around 1800psi on an aircraft.Along with everybody else, I wish the individual concerned a full recovery....however...and has invariably been the case within aviation, the incident offers yet another safety awareness exemplification with regard to procedures and practices and from my perspective, a more than valid one.
The official report on the incident will therefore make interesting reading.
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How it should be done...
In a previous life I worked as an aircraft mechanic/line maintenance supervisor in the U.S. Army...
The pros know all this stuff but amateurs are allowed to play with the tires on the airplane so:
You should deflate a tire before taking it off the axle and especially before undoing the two halves of the wheel. (This one seems so obvious but people still ignore the warnings cast right into the wheel halves and kill themselves.)
You shouldn't bang in the pressure until a dry tire bead seats itself with a bang but use some sort of (non-oily) lubricant. That bead seating in that way can cause a wheel to explode if it has a flaw and if that is your hand holding the inflation chuck...
Just cracking the valve on a high-pressure cylinder will still put full pressure into a tire because of that boring old law that says that pressure in a confined system is equal at all points in the system. (We used to lose guys to this one all the time, too idle to go find a regulator for tire inflation.)
I also had to deal there with split-rim truck tires, big 20-inch ones.
The killer with those was the locking ring coming loose after a tire change, when we were supposed to use a cage which was usually not available! I would see guys bent over inflating those things when that ring can take your head off, or so I was warned.
Basically, tires are best left to the pros to deal with since they can be surprisingly dangerous even to trained personnel, as this accident shows. An amateur can find several ways of at least causing serious damage if not personal injury just trying to save a bit of money. I know enough to just leave them alone, not having the equipment to deal with them safely.
The pros know all this stuff but amateurs are allowed to play with the tires on the airplane so:
You should deflate a tire before taking it off the axle and especially before undoing the two halves of the wheel. (This one seems so obvious but people still ignore the warnings cast right into the wheel halves and kill themselves.)
You shouldn't bang in the pressure until a dry tire bead seats itself with a bang but use some sort of (non-oily) lubricant. That bead seating in that way can cause a wheel to explode if it has a flaw and if that is your hand holding the inflation chuck...
Just cracking the valve on a high-pressure cylinder will still put full pressure into a tire because of that boring old law that says that pressure in a confined system is equal at all points in the system. (We used to lose guys to this one all the time, too idle to go find a regulator for tire inflation.)
I also had to deal there with split-rim truck tires, big 20-inch ones.
The killer with those was the locking ring coming loose after a tire change, when we were supposed to use a cage which was usually not available! I would see guys bent over inflating those things when that ring can take your head off, or so I was warned.
Basically, tires are best left to the pros to deal with since they can be surprisingly dangerous even to trained personnel, as this accident shows. An amateur can find several ways of at least causing serious damage if not personal injury just trying to save a bit of money. I know enough to just leave them alone, not having the equipment to deal with them safely.
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As for a cage on a Line station, maybe, maybe not depending on the operator....however....it would be highly unlikely that even with a cage, for routine adjustment of tyre px, the wheel assy, would be removed, placed in a cage, inflated, and then re-fitted given that the adjustment px is only ever going to be a small value. Inflation from transportation / storage is another matter however.
Ok, the wheels have been inspected in the shop, but mistakes are always possible.
Also, I noticed that manyengineers / mechanics don't deflate the wheels before removal. They usually give two reasons: Either that it takes too much time or that the noise of the escaping gas is too loud for them.
Plastic PPRuNer
Tyre blows are NOT nice. Did a boy the other week where a truck tyre let go in his face.
Lost one eye, badly damaged the other, comminuted LeFort III facial fractures.
Took a while to reassemble that one.....
Mac
Lost one eye, badly damaged the other, comminuted LeFort III facial fractures.
Took a while to reassemble that one.....
Mac
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md11engineer...
so what do you recommend if you are replacing a brake unit????????
I noticed that manyengineers / mechanics don't deflate the wheels before removal. They usually give two reasons: Either that it takes too much time or that the noise of the escaping gas is too loud for them.
so what do you recommend if you are replacing a brake unit????????
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The A320 AMM gives you the go ahead not to deflate the tyre before wheel removal if it is going to be refitted. This working practice maybe against convention but it does save a whole lot of time.
On a lighter note, many years ago a young apprentice was told to use the cage for the first inflation of a tyre after the wheel was assembled. 2 minutes later the apprentice was inside the cage with the wheel on the outside! No it wasn't me!!
On a lighter note, many years ago a young apprentice was told to use the cage for the first inflation of a tyre after the wheel was assembled. 2 minutes later the apprentice was inside the cage with the wheel on the outside! No it wasn't me!!
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md11engineer...
so what do you recommend if you are replacing a brake unit????????
:
I noticed that manyengineers / mechanics don't deflate the wheels before removal. They usually give two reasons: Either that it takes too much time or that the noise of the escaping gas is too loud for them.
I noticed that manyengineers / mechanics don't deflate the wheels before removal. They usually give two reasons: Either that it takes too much time or that the noise of the escaping gas is too loud for them.
Using a pneumatic-hydraulic jack, which is powered by nitrogen from the tyre also helps
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This might help and offer some very professional clarification for those who are interested....and probably prove equally "invaluable" for the "never been near an aircraft in their lives"..brigade of "experts".
Dunlop Aircraft Tyres Limited - Tech Support
As yet though, we still do not know why the engineer was working on the wheel concerned.....and until we do, then apart from stating the basic safety requirements and maintenance procedures, everything else is pure hypothesis is it not?.
A seemingly daft question however.....will this be the subject of an AAIB or HSE investigation....or both ?.
Dunlop Aircraft Tyres Limited - Tech Support
As yet though, we still do not know why the engineer was working on the wheel concerned.....and until we do, then apart from stating the basic safety requirements and maintenance procedures, everything else is pure hypothesis is it not?.
A seemingly daft question however.....will this be the subject of an AAIB or HSE investigation....or both ?.
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A lot of speculation going on here chaps. No mention yet by anyone of a Nitrogen rig problem i.e incorrect regulator or regulator fault possibly putting 3000 psi straight into the tyre, if that was the case then the poor guy had no chance.
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What I've learned during my apprenticeship was to at least reduce the pressure (in jacked up condition, not with the aircraft weight resting on the tyre) to appr. storage level and to inflate it again afterwards to full operating pressure. I know, this is the theory and it takes time. And time is money.
Using a pneumatic-hydraulic jack, which is powered by nitrogen from the tyre also helps
Using a pneumatic-hydraulic jack, which is powered by nitrogen from the tyre also helps
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Ok, but you'd remove a lot of the stored energy. From 200 PSI down to 50 PSI makes a lot of difference.
As a reminder the universal gas equation:
p*V= N*R*T
p=Pressure
V=Volume
n=Number of moles of gas
R=Universal gas constant
T=Temperature
p*V is the potential energy stored in the gas
Reducing the pressure by 75% also reduces the stored energy by the same amount.
As a reminder the universal gas equation:
p*V= N*R*T
p=Pressure
V=Volume
n=Number of moles of gas
R=Universal gas constant
T=Temperature
p*V is the potential energy stored in the gas
Reducing the pressure by 75% also reduces the stored energy by the same amount.
Sexpest(!)....You obviously didn't take the time to read post #8 by me two days ago
.....Quote:
"Many incidents similar to this in the past have been caused by the use of faulty charging regulators (or no regulator at all!) Charging in Bar's instead of PSI has also caused some accidents"
Some utter tosh being posted as usual by people who clearly have never been near a live airliner in their lives!
Please leave the uniformed speculation out.....Yes, there will be a full HSE investigation without a doubt!
.....Quote:"Many incidents similar to this in the past have been caused by the use of faulty charging regulators (or no regulator at all!) Charging in Bar's instead of PSI has also caused some accidents"
Some utter tosh being posted as usual by people who clearly have never been near a live airliner in their lives!
Please leave the uniformed speculation out.....Yes, there will be a full HSE investigation without a doubt!
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Sexpest(!)....You obviously didn't take the time to read post #8 by me two days ago.....Quote:
"Many incidents similar to this in the past have been caused by the use of faulty charging regulators (or no regulator at all!) Charging in Bar's instead of PSI has also caused some accidents"
Some utter tosh being posted as usual by people who clearly have never been near a live airliner in their lives!
Please leave the uniformed speculation out.....Yes, there will be a full HSE investigation without a doubt!
"Many incidents similar to this in the past have been caused by the use of faulty charging regulators (or no regulator at all!) Charging in Bar's instead of PSI has also caused some accidents"
Some utter tosh being posted as usual by people who clearly have never been near a live airliner in their lives!
Please leave the uniformed speculation out.....Yes, there will be a full HSE investigation without a doubt!
Now we had a discussion about possible causes.
It might have been:
1) a faulty rim or tyre
2) a defective filling gauge
3) the wrong type of pressure regulator (high pressure for filling struts instead of a low pressure one for filling tyres, don't laugh, I've seen this happen) or no pressure regulator at all.
We discussed the sense or nonsense of deflating a wheel before removing it (IMO necessary, I have seen damaged wheel ties bolts).
We also discussed the practice of fully inflating uninstalled wheels on line stations without the proper safety equipment.
What I think can be discounted is the idea of somebody having confused oxygen and nitrogen cylinders.
(though it surprised me to learn that in the UK the connectors for nitrogen and oxygen cylinders are the same. This explains the reaction of our airline QA, when a nitrogen cylinder was found (though not connected to it) on an oxygen rig at an UK station a few months ago).
I've been working in aircraft maintenance now for more than a dozen years (mostly line maintenance, during which I must have changed hundreds of wheels and brakes) and I AM a licenced engineer with three transport category aircraft type ratings. I have also seen shortcuts taken by engineers and mechanics either out of convenience, because equipment was not available or as not to loose time. I have to confess that occasionally I was guilty of this as well, not involving the airworthiness of the aircraft, but breaking health and safety rules, risking my own health or life.
Concerning tyre explosions, a few years ago, while driving to work, I witnessed the explosion of a lorry tyre on an Autobahn (I was driving about 50 meters behind the lorry). A BMW, which was right beside the exploding tyre, had it's R/H rear fender and rear bumper torn off. Since then I'm a bit carefull concerning wheels and tyres.
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Apologies boeing eng, missed that one! couldn't agree more, a lot of very uninformed speculation going on. As you say the in the fullness of time exactly what happened will come to life and hopefully lessons will be learnt.
MD11 Eng....I don't think anyone is questioning your credentials
I think it’s fair to say the cause of this accident will have been mentioned somewhere in this thread by now!
Those of us involved in line maintenance should know the risks of working with wheels and the correct procedures to follow (all this talk of deflating a wheel before removing it is pure egg-sucking!!) There are obviously variations between companies but some comments/observations that have been made are frankly ridiculous!
Let this poor Guy make his hopefully good recovery and then await the findings of the Enquiry.
I think it’s fair to say the cause of this accident will have been mentioned somewhere in this thread by now!
Those of us involved in line maintenance should know the risks of working with wheels and the correct procedures to follow (all this talk of deflating a wheel before removing it is pure egg-sucking!!) There are obviously variations between companies but some comments/observations that have been made are frankly ridiculous!
Let this poor Guy make his hopefully good recovery and then await the findings of the Enquiry.
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This nearly happened to me. Servicing a low tire on a B737-700. Had pressure cranked up and servicing adaptor on hose. Did a double check to make sure I had close to the required 200psi dialed in to ensure a positive flow. That is when I realized someone had swapped the low pressure regulator with a high pressure one and had it set up for tire servcing. I had nearly 1800 psi dialed up for the serivce...
Informed Management and their attitude was "oh well"
Not the response I expected from two seconds from being blown to bits. Needless to say I was NOT a happy camper but no one would own up to the swapped regulator.
Informed Management and their attitude was "oh well"
Not the response I expected from two seconds from being blown to bits. Needless to say I was NOT a happy camper but no one would own up to the swapped regulator.
Very dangerous things inflated tyres, if a heavy truck is passing me on the motorway I always wind the window up just in case,
Would prob blow the window in but you can only try.
Nick.
Would prob blow the window in but you can only try.
Nick.
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The Alternative Way
There is an alternative way of inflating Aircraft Tyres.
The equipment we supply stores Liquid Nitrogen at 350 psi and then converts it to gas, at room temperature, then supplies it to the Tyre through standard hose end fittings. This means that it is impossible to provide gas at a pressure greater than 350 psi which is too low to cause rupture of the Tyre. By law aircraft tyres must have a min burst pressure of 4 times their operating pressure so this system is much safer.
The tank holds the equivalent of 20 cylinders of gas and is filled once a week by BOC. There is therefore no cylinder handling or reconnection, also no empty or full cylinders have to be transported.
Visit | McNaughton Dynamics UK | Nitrogen, Oxygen and Cryogenic Pressurisation Servicing Units | for further information.
The equipment we supply stores Liquid Nitrogen at 350 psi and then converts it to gas, at room temperature, then supplies it to the Tyre through standard hose end fittings. This means that it is impossible to provide gas at a pressure greater than 350 psi which is too low to cause rupture of the Tyre. By law aircraft tyres must have a min burst pressure of 4 times their operating pressure so this system is much safer.
The tank holds the equivalent of 20 cylinders of gas and is filled once a week by BOC. There is therefore no cylinder handling or reconnection, also no empty or full cylinders have to be transported.
Visit | McNaughton Dynamics UK | Nitrogen, Oxygen and Cryogenic Pressurisation Servicing Units | for further information.
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md11
what would have been the pressure in a lorry tyre then??? . as you stated in your own post a lot of damage was done to the car beside it.
because of such a large volume in a large main/nose wheel there will always be a risk of serious damage even at low storage psi (50).
Concerning tyre explosions, a few years ago, while driving to work, I witnessed the explosion of a lorry tyre on an Autobahn (I was driving about 50 meters behind the lorry). A BMW, which was right beside the exploding tyre, had it's R/H rear fender and rear bumper torn off. Since then I'm a bit carefull concerning wheels and tyres.
what would have been the pressure in a lorry tyre then??? . as you stated in your own post a lot of damage was done to the car beside it.
because of such a large volume in a large main/nose wheel there will always be a risk of serious damage even at low storage psi (50).