Main reason behind deflating a wheel
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Main reason behind deflating a wheel
Prior to removal, a wheel is deflated as a standard safety practice, whats the main reason behind this ?
Is it because of the valve core's ability to be ejected like a bullet under pressure ?
i was asked this question, my answer was that since an MLG could have around 180-200 PSI, add to that possible damage and wear + heat could increase the chances of it bursting when handled for removal. but he said no, its not the main reason, go look for the answer.
thanks.
Is it because of the valve core's ability to be ejected like a bullet under pressure ?
i was asked this question, my answer was that since an MLG could have around 180-200 PSI, add to that possible damage and wear + heat could increase the chances of it bursting when handled for removal. but he said no, its not the main reason, go look for the answer.
thanks.
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I think the reason to this is to keep the wheel rim from bursting and /or dislodging.
Have a look at this :
http://www.dpi.nsw.gov.au/__data/ass...ing-wheel1.pdf
Have a look at this :
http://www.dpi.nsw.gov.au/__data/ass...ing-wheel1.pdf
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You will find much useful aircraft tire information on these following webpages...
Aircraft tire Information
Desser Aircraft Tire & Rubber Company
However, the precise answer you seek doesn't appear to be listed. I would say that the answer your instructor is seeking, is that many aircraft wheels are of the split-wheel design.
To eliminate any chance of dangerous errors being made in the wheel/tire removal... where the fasteners holding the two halves of the split wheel assembly together, are mistaken for the fasteners securing the wheel to the axle hub... tire deflation before removal, is a necessary step.
Michelin aircraft tire information and knowledge test...
http://www.airmichelin.com/uploadedF...on_level_1.pdf
FAA Tire Advisory Circular, 4/18/05...
http://rgl.faa.gov/Regulatory_and_Gu...E/AC20-97B.pdf
Aircraft tire Information
Desser Aircraft Tire & Rubber Company
However, the precise answer you seek doesn't appear to be listed. I would say that the answer your instructor is seeking, is that many aircraft wheels are of the split-wheel design.
To eliminate any chance of dangerous errors being made in the wheel/tire removal... where the fasteners holding the two halves of the split wheel assembly together, are mistaken for the fasteners securing the wheel to the axle hub... tire deflation before removal, is a necessary step.
Michelin aircraft tire information and knowledge test...
http://www.airmichelin.com/uploadedF...on_level_1.pdf
FAA Tire Advisory Circular, 4/18/05...
http://rgl.faa.gov/Regulatory_and_Gu...E/AC20-97B.pdf
It could be worth mentioning that air does actually weigh something, so a tyre inflated to 200psi is going to be considerably heavier than a deflated one.
If a tyre is being replaced because it is damaged, it is worth bearing in mind that taking it into a warm workshop could increase the pressure and make things worse. I guess this was a contributing factor to that USAF captain getting killed by her car tyre.
U.S. Air Force captain Jenna Wilcox on holiday in Scotland dies in freak accident as sports car tyre explodes in her lap | Mail Online
Aside from risks of undoing the wrong bolts, it is better to have the wheel and tyre attached to something big, i.e. an aeroplane, if it were to fail, as the tyre and wheel wouldn't travel so far.
If a tyre is being replaced because it is damaged, it is worth bearing in mind that taking it into a warm workshop could increase the pressure and make things worse. I guess this was a contributing factor to that USAF captain getting killed by her car tyre.
U.S. Air Force captain Jenna Wilcox on holiday in Scotland dies in freak accident as sports car tyre explodes in her lap | Mail Online
Aside from risks of undoing the wrong bolts, it is better to have the wheel and tyre attached to something big, i.e. an aeroplane, if it were to fail, as the tyre and wheel wouldn't travel so far.
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The possibility of broken bolts in the wheel which can cause the wheel to split after loosening the wheelnut
part from the obvious safety reasons behind deflating a wheel before removal theres also the labour saving benefit.....
Most of the jacks I've used in the past were pneumatic and the air from the wheel as it was deflating was used to pump the jack to lift the wheels clear off the ground.....
Most of the jacks I've used in the past were pneumatic and the air from the wheel as it was deflating was used to pump the jack to lift the wheels clear off the ground.....
thanks all for the replies. more ideas and thoughts welcome!
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Put simply, an inflated tire is a pressure vessel. It is a pressure vessel with design limits... that can be easily exceeded by a combination of circumstances... some of which may not be readily observable, or known to the person within the critical range for injury or death, if that tire happens to burst.
The larger the tire, and the greater the pressure, the higher the risk of injury/fatality.
It makes sense to approach the wheel/tire removal process with the aim of reducing any potential danger. Deflating the tire on the wheel you are about to remove, means one less workplace hazard.
The larger the tire, and the greater the pressure, the higher the risk of injury/fatality.
It makes sense to approach the wheel/tire removal process with the aim of reducing any potential danger. Deflating the tire on the wheel you are about to remove, means one less workplace hazard.
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THE reason it is deflated before removing the axle nut, is that the axle nut may be the only thing holding the hub in one piece, you may not be able to see the crack in the hub, especially the inner half. When you have 200psi in a 49inch wheel it makes quite a mess when it separates.
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Spannersatcx is 100% correct. Tie bolts do fail. I've seen a wheel on a C Check input F100 that had two bolts sheared on it due to corrosion, god knows what the others were like! It should be a cardinal rule to deflate them, even if they are going to be only off for a short while.
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@Ahmed88
Spannersatcx is absolutely correct here.
A guy was killed in a company i used to work for, when the two wheel halves came apart during inflation.
I was taught to deflate the tire before removal of the main wheel nut, and to stand at a 45 degree angle to the tire during inflation in case a wheel half shot off.
Spannersatcx is absolutely correct here.
A guy was killed in a company i used to work for, when the two wheel halves came apart during inflation.
I was taught to deflate the tire before removal of the main wheel nut, and to stand at a 45 degree angle to the tire during inflation in case a wheel half shot off.
Last edited by Heliarctic; 5th Dec 2010 at 14:09.
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Spanners:
It is still in the Boeing DDG for the 747:
32-10-01 Main Gear Wheel Tiebolts - Cat A
Basically a get you home procedure if you are somewhere without a spare wheel when you read the (M) section of the DDG.
It is still in the Boeing DDG for the 747:
32-10-01 Main Gear Wheel Tiebolts - Cat A
Basically a get you home procedure if you are somewhere without a spare wheel when you read the (M) section of the DDG.
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Weirdly, the Airbus AMM says the following!
Suggesting that it's ok to remove the wheel before deflating the tyre so long as the tie bolts are ok. 
Later in the task it goes on to say
Again suggesting that its ok to remove the wheel fully inflated so long as its only for access or inspection 
Subtask 32-41-11-210-074
B. Wheel Assembly Check
NOTE : Do this check before you remove the wheel.
(1) Do a check of the wheel assembly for missing, broken or loose
tie-bolts.
CAUTION : TIRES ON WHEEL ASSEMBLIES WITH MISSING, BROKEN OR LOOSE
TIE- BOLTS MUST BE DEFLATED BEFORE AXLE NUT IS LOOSENED.
FAILURE TO DEFLATE TIRE BEFORE AXLE NUT IS REMOVED CAN
RESULT IN INJURY SHOULD WHEEL SEPARATE.
B. Wheel Assembly Check
NOTE : Do this check before you remove the wheel.
(1) Do a check of the wheel assembly for missing, broken or loose
tie-bolts.
CAUTION : TIRES ON WHEEL ASSEMBLIES WITH MISSING, BROKEN OR LOOSE
TIE- BOLTS MUST BE DEFLATED BEFORE AXLE NUT IS LOOSENED.
FAILURE TO DEFLATE TIRE BEFORE AXLE NUT IS REMOVED CAN
RESULT IN INJURY SHOULD WHEEL SEPARATE.
Later in the task it goes on to say
(3) Fully deflate the tire.
NOTE : If you must remove the wheel for access or inspections, it is
not necessary to deflate the tire if:
- The tire is in the correct condition
- The tire pressure is in the normal operating range
(Ref. TASK 32-41-00-210-003).
If you have not these two conditions, you must deflate the
tire.
NOTE : If you must remove the wheel for access or inspections, it is
not necessary to deflate the tire if:
- The tire is in the correct condition
- The tire pressure is in the normal operating range
(Ref. TASK 32-41-00-210-003).
If you have not these two conditions, you must deflate the
tire.
Another caution when deflating a tyre!
The valve may freeze during the process and not fully deflate. Make sure the tyre is fully deflated before removing the wheel nut!
Stay safe.
The valve may freeze during the process and not fully deflate. Make sure the tyre is fully deflated before removing the wheel nut!
Stay safe.
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Deflating is for above mentioned reason (axle nut being the only thing holding the 2 wheel parts together when bolts are broken).
Some AMM's state however that a visual check can go in place. For e.g. 757 it is not necessary to deflate if all bolts are ok and wheel change is for normal tyre wear reasons. I almost always do deflate as good practice though.
Some AMM's state however that a visual check can go in place. For e.g. 757 it is not necessary to deflate if all bolts are ok and wheel change is for normal tyre wear reasons. I almost always do deflate as good practice though.
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Half hub wheels .. Deflate as a matter of course before removing the axle nut..
Wheels with demountable flange joint.. Contention as taking it off the axle deflated or not deflated isn't going to make the slightest different. However if its deflated, if its damaged by something else, it will not fail!
Wheels with demountable flange joint.. Contention as taking it off the axle deflated or not deflated isn't going to make the slightest different. However if its deflated, if its damaged by something else, it will not fail!
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PERRIN
Found a wheel assy when in Saudi that had 5 hub bolts broken after wheel removed. I am now retired and have in my old tool box about 100 valve cores which I removed and kept-any buyers?
Keep them up boys
Keep them up boys