Tyre pressures are crucial

[Bus429]

There's a lesson in this (http://www.flightglobal.com/articles/2010/04/07/340345/ntsb-industry-unaware-of-tyre-pressure-dangers.html) for us...

[MATMAX]

sorry Bus but i would say no lesson.
what is written in the checklists ?
no tyre pressure gage there ...?
you never check tyres press when it is written in the checklists ?

[muduckace]

What a cluster F@&k of an accident, immagine pulling reverse thrust the engines spool up but the reversers never deploy. Nightmare. Surprised that a 36% loss in pressure would cause a failure as I have seen tires that have lost 75% of their pressure make it to the gate w/o incident.

But then again my experience is mostly with widebodys. I would suspect a bad pressure guage, if all tires are this low, or ignorant reporting of the accident. If they were all low and the aircraft was heavy who knows.
Tires do not magically lose pressure at a controlled rate. Every tire is different. Another reason why tire pressure monitoring equipment is a nice feature.

Tires blow on big jets all the time and in my limited experience with corperate in the usa I can say with confidence for sure that there is less oversight. Most big jet operators have a program, often TP checks get doccumented every 24 hrs.

[MATMAX]

ah ... remember Concorde.

[muduckace]

Yeah, that tire blew for the same reason that many others have.. Got cut by FOD. Really with the few concorde's that ever flew it was only a matter of time, a concorde could have crashed decades ago for the same reason. Bet your bottom those tp's were checked prior to each flight.

[Dodo56]

The swiss cheese model strikes again. Design factors may be something we can do nothing about but if the aircraft had been operated with tyre pressures as designed none of this would have happened, simples. That's the lesson for us.

Tyres can and do fail as little as 30% underinflated and some designs are higher stressed than others. Experience on other types is no excuse for complacency, that's why we have manuals and specs.

How often do we check tyre pressures? How many of us know how frequently they should be checked? What would you do if you checked tyres and found they were over pressure? Tyres do lose up to 5% px in 24hrs, this is a fact and not cause for rejection. Does your AMP have the necessary checks in it?

[MATMAX]

...and everytime a tyre should be changed on Concorde , it was a brand new one and not a "retreated" one...
thats what i have been told by some Buddies who used to work on it.

[forget]

.... operator not checking the tyre pressure, which led to all four main gear tyres rupturing at just above V1 speed.

So we have four tyres destroyed, then ....

Investigators found that the Learjet's tyres, which are supposed to be inflated to 15.1bar (219lb/in2), had progressively lost about 2% of their pressure a day over a period of about three weeks before the accident, a typical leak rate for high-pressure tyres. Federal Aviation Administration certification rules allow for the tyres to lose as much as 5% a day.

........ followed by ............

Investigators determined that the tyres on the accident aircraft were inflated to about 9.66bar, 36% below the optimum pressure and well below the point at which they must be changed because of heat damage.

Eh? That's some pretty fancy accident investigation. :confused:

[Krystal n chips]

I don't know anything about the FAA regs or indeed the Bizjet world, but there is one tiny point that sort of hits you in the face here.

What, precisely, was the aircraft doing for the 3 weeks prior to the accident?

Was it flogging around the USA?......or was it sitting on a ramp somewhere?...either way, when did it last see the attention of an engineer during this period and to what depth of routine servicing was it exposed?

How long in the FAA world can an aircraft be operated ( ok in this case it's a Bizjet so the operation will be different I assume from a scheduled carrier ) before it becomes mandatory for an engineer to perform a service check of any depth on the aircraft eg a daily/ night stop.

To say however that the industry is not aware of tyre px maintenance problems would see therefore to be bolleaux given that certainly from my experience tyres are invariably checked per se

I would guess those figures in the report are extrapollated from the manufacturers examination of the carcass and thus are based on a 2% loss from what would appear to be the last time the px were checked and recorded....which brings us back to my queries above.

[TURIN]

Same old (very sad) story. Cut corners at your peril.

"If you think maintenance is expensive, try having an accident"

Don't know who first said that but it should be repeated louder and louder everyday.

[BAe146s make me cry]

Echo Turin's comments. Especially to the occasional Tits in the hangar offices, the retired Tit at Farnborough, the costly Tits at LGW and the passive Tits in Cologne..

See you at the AGM

BAe

Association of Licensed Aircraft Engineers (ALAE) - Welcome (http://www.alae.org)

[The Wheely King]

Without a complete serviceable set of wheels and tyres your clean aircraft becomes a clean statue, wheels and tyres are very overlooked and i fear to the deterement of many airlines.tyre pressures are ultra crucial and should be checked at every stop,if practicable as hot or warm tyres should not be checked for their pressures as this will be elevated by the heat held in the tyre casing and the heat in the brake cassette that slowly radiates away,it is recomended that the tyre should be tested with the back of the hand and if it is hot to the touch it is to hot to check and this would be deemed cool enough to be checked after three hours,there is a safety aspect as well 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. deflated tyres can run for long enough for the a/c to clear most if not all runways but will have to be removed as well as its axle twin once the a/c is on stand,and both wheels have to be marked for overhaul and the flat one must also have further more investigative action carried out to determine the reason for deflation and the integrity if the wheel hub also has to be checked,I can safely say that the last 8 out of 10 deflation cases I have dealt with the axle twin once checked the wheel hub had failed NDT with stress cracks due to this being the remaining inflated wheel taking all of the weight.A tyre can also burst due to the rapid build up of heat from a long taxi with a heavily loaded a/c.Not only should tyre pressure be checked but shine the torch into the wheel and check the tie bolts they do shear and this can also lead to a slow loss of pressure in a wheel and it is also a reason to remove a wheel.Above all be safe around hot wheels and tyres if they have to be removed and are not going back on DEFLATE THEM it may be a noisy pain in the arse,it may save a life or two and stop and blast damage to the a/c and anything within an easy 50-100 yard radius.

[lordofthewings]

Learjet requires the tyre pressures to be checked prior to the first flight of each day..This should be either done by maintenance staff or crew should have an authority to do so. Biz jets can often be away from the regular organisation that maintains them, this is where it becomes a problem...Unlike airlines they do not fly regular routes....
I have recently moved into the corporate world from the airlines and it is very different...Some good , some not so...

[Edgar Jessop]

Wheely King I agree with most of what you say, but not this bit:

I can safely say that the last 8 out of 10 deflation cases I have dealt with the axle twin once checked the wheel hub had failed NDT with stress cracks due to this being the remaining inflated wheel taking all of the weight.

Yes it is possible that loss of tire px can be caused by a cracked hub but I have never in 15 years seen any cases where the axle mate hub has been cracked by running with an underinflated partner. The tire carcass itself may well be overstressed in such cases and the tire companies will automatically scrap any tire marked "deflated" or "partner", however the wheel hub should still be OK.

Your comments about tiebolts are also worth note, as a single tiebolt failure can be tolerated for a short time with no apparent symptoms. In time however the bolt either side of the failed one will itself fail in overstress and then the deformation from landing stresses will allow the center packing to extrude out between the half hubs resulting in instant deflation. This is a real issue that can affect aircraft like 737s with outboard hub fairings.

[TinyTim2]

We have just had a B737 on an emergency air turnback due to a thrown tread , the tyre pressure was checked and topped up the night previous but was known to be leaking ...........No time / inclination to change a wheel so just top it up again , It'll be OK , Oh yeah !!!!!!!!!!!!!!!!!

[The Wheely King]

I have miss written slightly concerning the deflation of an axle twin , the 8 out of 10 I have seen has been the result of a burst (747-200F) and we have found that in the twin that remained at operating px the o/b hub has cracks to the spokes but this was probably from turning of the a/c (so I have since been informed).

The loss of one tie-bolt(wheel on a/c ) this wheel must be removed (32-45-03) then I agree the bolts either side of the missing one have to be replaced,although there has been a s/b about time life programme where all the bolts are replaced for a new set and are then replaced after 4000 cycles and carry out dvi for every 4 tyre changes and mpi at 5 or o/h

[Northbeach]

http://aviation-safety.net/database/record.php?id=19910711-0 (http://aviation-safety.net/database/record.php?id=19910711-0)

July 11, 1991 Jeddah Saudi Arabia a DC-8 was lost killing everybody on the jet. For me this accident crystallized the importance of proper tire inflation. If you haven’t read the accident analysis it is worth your time as it makes absolutely clear the terrible hazards of improper tire servicing/conditions.

[johns7022]

Some thoughts:

Very few biz pilots own calibrated tire pressure guages sufficient to check jet tires...fewer still check everyday prior to flight...fewer still would have checked prior to a flight at midnight, as such was the Lear 60 departure time. Few pilots would have actualy given more then a cursory look at thier tires in the dark, with a flashlight, much less gotten on their hands and knees to check tire pressures.....

Fewer still are pilots that actualy know what the rated tire pressure is for thier aircraft..fewer still are the pilots that check, know the number, and will scrub a flight at midnight because no nitrogen is available at that time to pump them up...

If I sound like a broken record, my apologies...just another rant about professional responsibility....

[TURIN]

The loss of one tie-bolt(wheel on a/c ) this wheel must be removed (32-45-03)

Not necessarily.

A320 for one and I believe B767 with some operators allow one tie bolt missing for a limited period.

Still got to get the wheel off and check that the other end hasn't trashed the brake unit or inside of the wheel but hey-ho. :hmm:

[Edgar Jessop]

Wheelyking someone's been reading his CMM LOL :8

The time life program you refer to is an alternative to doing MPI on the bolts, on the logic that what you lose in hardware scrappage costs you save on reduced labor costs. That works fine as long as you know the fitment date of the original bolts!

A little story for you. An airline I used to know some years back operated 747-100 and 737-4/500. Their workshop practice was to clean and NDT tiebolts then throw them all in a tray together and pick out the required number when they built a wheel. What they failed to realise is those 2 aircraft types, of some 20 years age difference, used the same P/N tiebolt and they couldn't understand why on their new 737s they had a rash of age related tiebolt failures! At least one was a multiple bolt failure causing tire deflation because the first broken bolt was hidden by the wheel fairing. And as Turin says the migrating bolts mullered the brake.

So it's not only flight crew where complacency and sloppy practice can have serious consequences!

[leewan]

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.

Fully concur ! Take a look at this video from 4:40 onwards. Don't ever go near a wheel if the flight crew advises u upon arrival to gate that the wheels are hot.
YouTube - Airbus A340-600 Rejected Take-Off test (subtitles) (http://www.youtube.com/watch?v=hRzWp67PIMw)

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.

[HAWK21M]

A 24hrs check on the tires is a sign of good Maintenance.

[The Wheely King]

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.

[Edgar Jessop]

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.

[muduckace]

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.

[Edgar Jessop]

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

[The Wheely King]

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 )

[C-46]

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):8 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.