Tyre pressures are crucial
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an aircraft wheel inflated to 200psi is a bomb waiting to go off and many ground engineers have been seriously injured and some have been killed by hot tyres suddenly exploding for no reason,research has been carried out by the US navy on the destructive force in an exploding aircraft tyre and it has the equivalent force as the detonation of two and a half sticks of dynamite.
YouTube - Airbus A340-600 Rejected Take-Off test (subtitles)
Tyre pressure are one of the most overlooked aspects in a/c mx. I think most are in the false belief that since it's only used on ground, than there's not much importance. The Saudi incident that Northbeach highlighted is a good example of tyre pressure's importance. Most modern commercial jets with TPIS will have an advisory message in the cockpit highlighting a low tyre pressure to the flight crew if it detects low tyre pressure in any of the wheels.
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Edgar,
I had a good one a while back,we had an a/c set of wheels that were "as removed" every wheel came to us completely flat (as they should/must if they are to be transported via road) and whilst doing first inspection I noticed to my joy a new in/bd hub and at huge cost new I took great interest,but the alarm bells started screaming,there was something badly wrong with this set up,I ordered one tie-bolt to be removed and to my astonishment we had a complete miss-match of hubs,the o/b was a very old item that uses small diameter tie-bolt and the in/bd was the latest type hub that uses a large diameter tie-bolt and the whole assy was held together with a set of small diameter tie-bolts and what was worse this had been in service like this as the tyre was worn to limits! both hubs were immediately marked for removal from service and defaced and scrapped.I had a audit from the CAA and they made a comment that they liked the fact that all of the tie-bolt from wheels in for service/overhaul are kept in purpose made wooden blocks to stop any further damage.We have now also had to make soft cases for the bearings whilst they are out of the wheel as these are also very easily damaged.
I had a good one a while back,we had an a/c set of wheels that were "as removed" every wheel came to us completely flat (as they should/must if they are to be transported via road) and whilst doing first inspection I noticed to my joy a new in/bd hub and at huge cost new I took great interest,but the alarm bells started screaming,there was something badly wrong with this set up,I ordered one tie-bolt to be removed and to my astonishment we had a complete miss-match of hubs,the o/b was a very old item that uses small diameter tie-bolt and the in/bd was the latest type hub that uses a large diameter tie-bolt and the whole assy was held together with a set of small diameter tie-bolts and what was worse this had been in service like this as the tyre was worn to limits! both hubs were immediately marked for removal from service and defaced and scrapped.I had a audit from the CAA and they made a comment that they liked the fact that all of the tie-bolt from wheels in for service/overhaul are kept in purpose made wooden blocks to stop any further damage.We have now also had to make soft cases for the bearings whilst they are out of the wheel as these are also very easily damaged.
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Comparing wheel stories, how sad is that? 
I've lost count of the number of wheels I've seen received on pallets, worn to limits and then some, with gaping cuts in the tread, fully inflated and stacked 2 high. Via air transport! So much for proper handling of dangerous freight....
Regarding care of parts while WIP, you can go completely overboard but as long as a few sensible precautions are taken you're generally all right. Segregate everything into the same wheel set and keep it together is #1 fairly obviously. Bearings are sensitive and the easy way to prevent damage and corrosion is to put each cone into a thick plastic bag. Other parts are fairly robust and can be placed together in a plastic parts tray to keep them together. Common sense is an essential factor in handling wheels being serviced, though wheel cleaners are not always the intellectual elite of the maintenance world and a lot rests on the shoulders of the parts inspector to ensure everything is not only satisfactory to the manual, but as you found, the right part in the first place! It's not always as obvious as incorrect tiebolts either. I'm aware of at least one lost ATR42 mainwheel due to the incorrect P/N outer race being fitted (there are 2 standards with different cone angles, visually almost identical and only identifiable by P/N).
As with so many things in this business accuracy can be the difference between life and death, even in a supposedly simple and unglamorous area.
I've lost count of the number of wheels I've seen received on pallets, worn to limits and then some, with gaping cuts in the tread, fully inflated and stacked 2 high. Via air transport! So much for proper handling of dangerous freight....
Regarding care of parts while WIP, you can go completely overboard but as long as a few sensible precautions are taken you're generally all right. Segregate everything into the same wheel set and keep it together is #1 fairly obviously. Bearings are sensitive and the easy way to prevent damage and corrosion is to put each cone into a thick plastic bag. Other parts are fairly robust and can be placed together in a plastic parts tray to keep them together. Common sense is an essential factor in handling wheels being serviced, though wheel cleaners are not always the intellectual elite of the maintenance world and a lot rests on the shoulders of the parts inspector to ensure everything is not only satisfactory to the manual, but as you found, the right part in the first place! It's not always as obvious as incorrect tiebolts either. I'm aware of at least one lost ATR42 mainwheel due to the incorrect P/N outer race being fitted (there are 2 standards with different cone angles, visually almost identical and only identifiable by P/N).
As with so many things in this business accuracy can be the difference between life and death, even in a supposedly simple and unglamorous area.
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Many operators transport servicable tires at full operating pressure, wear limitations are designed for operational purposes, static and worn or cut in the tread I don't know. There is not really much literature on the subject and not saying it is right to transport worn tires fully charged but I can not say it is wrong either.
I dump most pressure during removal for 2 reasons 1- broken tie bolts 2-much easier to handle. There are no brainers like a light post shaft sticking out of one, if I can not determine if the carcass ply has been damaged by measuring cut depth, I would consider the tire to have dangerous potential.
I dump most pressure during removal for 2 reasons 1- broken tie bolts 2-much easier to handle. There are no brainers like a light post shaft sticking out of one, if I can not determine if the carcass ply has been damaged by measuring cut depth, I would consider the tire to have dangerous potential.
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Unless things have changed since I was involved in it transporting fully inflated tires in cargo holds was a big no-no in Europe. It is becoming more common to store tires fully inflated for line use to save time and nitrogen though. The trouble with transporting fully inflated tires (aside from the danger of tread cuts and weak tiebolts on worn ones) is the rounded inflated profile on new tires makes them more likely to topple, and if being rolled off tailboards they have a near-100% bounce
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I have recently been involved with the goods inwards side of my works stores as we now inform any of the coureir drivers to refuse to take a wheel that is still inflated to operating px, there are regulations about road transport ,serviceable wheels with fresh rubber can be transported by road and air.We carry 2 serviceable wheels in bulk cargo at operating px but as Edgar said inflated wheels at high px is a big no no not only in europe we made the mistake of loading a worn to limits wheel back into bulk cargo as we had used both serviceable wheels and this wheel was just worn with no canvas showing simply because the next stop was at a station in africa that held no wheels for us a , a simple paper excercise cost the airline a days on the floor while the s aussie caa checked around ,the flying spanner wrote out the wrong labell,a defect one instead of a hold one , once this was explained and the caa watched the wheel being deflated all was good.The bounce thing Iam with Edgar on this one if the wheel is at operating px and just rolled off a tailgate of a truck it will bounce uncontrollably and a 747 wheel assy is 475lbs in weight and will cause some nasty injuries if it lands on you ,there is also the fact that the impact on a defective tyre may make it suddenly explode (check this website out to see what an exploding wheel is capable of www.alberthaviation.com and look at the videos of testing safety inflation cages )
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Aircraft Tires Have Vent Holes Punched in them, They Leak
What most pilots don't know, or want to know and some mechanics don't know either is that aircraft tires are made to leak inflation gas. A series of small pin holes are punched into them above the bead at manufacture covered by green dots in the cast of tubeless tires and white dots in the cast of tube type tires. This allows the inflation gas that seeps through the natural rubber liner (natural rubber leaks)
to wick out through the tire casing and not cause separation in the casing. Some tires leak 1% some leak 5%. If you don't service them daily or prior to first flight and it been 2-3 weeks you got a potenial problem.
Throw in the fact that you have basically the same size tire on a Lear 23 @ 12,500 pounds and a Lear 60 at twice that weight even at double the higher pressure you got a big problem. Also, even if you gave a pilot a pressure gauge, he/she isn't going to crawl inder there and get their white shirt dirty, and even if they did, where are they going to find nitrogen at that time a night, how much and what about the delay imposed on the rock star or air head hollywood type. Pleanty of info out the Goodyear, Michelin, Dunlop websites.
to wick out through the tire casing and not cause separation in the casing. Some tires leak 1% some leak 5%. If you don't service them daily or prior to first flight and it been 2-3 weeks you got a potenial problem.Throw in the fact that you have basically the same size tire on a Lear 23 @ 12,500 pounds and a Lear 60 at twice that weight even at double the higher pressure you got a big problem. Also, even if you gave a pilot a pressure gauge, he/she isn't going to crawl inder there and get their white shirt dirty, and even if they did, where are they going to find nitrogen at that time a night, how much and what about the delay imposed on the rock star or air head hollywood type. Pleanty of info out the Goodyear, Michelin, Dunlop websites.
