Tyre wear - how much is safe?
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Tyre wear - how much is safe?
I have just got off a flight and the tyres looked like this: 
Is this safe and normal practice? I asked the pilot if he was aware of the state of the tyre and he answered "Oh yes!". I didn't press him further but I did stop to take a couple of photos....
What do you guys think? It was a Havilland Dash 8-Q400 - a 72 seater turboprop.
Is this safe and normal practice? I asked the pilot if he was aware of the state of the tyre and he answered "Oh yes!". I didn't press him further but I did stop to take a couple of photos....
What do you guys think? It was a Havilland Dash 8-Q400 - a 72 seater turboprop.
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Theoretically, it's 2mm of tread left on the tyre (using the wear indicators as a reference). In reality, i.e. on the line, so long as there are no threads showing it's fine. It should be changed as soon as threads become visible. Even if there are threads showing there's a good inch or more of rubber compound, metal thread, nylon thread etc so don't worry!
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on the line, so long as there are no threads showing it's fine. It should be changed as soon as threads become visible.
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Tyre Wear
Visit the Goodyear website and download the tire data book:
http://www.goodyearaviation.com/tiredatabook.html
http://www.goodyearaviation.com/tiredatabook.html
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There were threads showing, though it's not that obvious in the picture. A few people I showed it to (not plane engineers) said they probably wouldn't have boarded the plane if they saw the tyre looking like that.
As for seeing the air in the tyre, that's what I was hoping WOULDN'T happen during takeoff/landing!
It gave me a bit of a fright at the time but it seems that aircraft tyres are quite a different construction to the car/motorbike ones I am used to!
Thanks for the insight, guys we now return you to your normal techie discussions!
As for seeing the air in the tyre, that's what I was hoping WOULDN'T happen during takeoff/landing!
It gave me a bit of a fright at the time but it seems that aircraft tyres are quite a different construction to the car/motorbike ones I am used to!
Thanks for the insight, guys we now return you to your normal techie discussions!
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Skippy xyz
How can I say this without offending you, as if I care. There is enough snot flying around this industry this week without you trying to create another drama. Scaremonger.
How did you have a camera on you under the restrictions at the time?
You are in a realm about which you have NO understanding.
You may recognise a car tyre which is suspect. Aeroplane tyres are a whole different world. Not much turning, therefore not much grip required transversely.
What is your job? Please let me question your professional ability in an open forum. I await your invitation.
Danny, this is an ongoing issue. Secure site sounds good to me. R
How did you have a camera on you under the restrictions at the time?
You are in a realm about which you have NO understanding.
You may recognise a car tyre which is suspect. Aeroplane tyres are a whole different world. Not much turning, therefore not much grip required transversely.
What is your job? Please let me question your professional ability in an open forum. I await your invitation.
Danny, this is an ongoing issue. Secure site sounds good to me. R
Last edited by silverhawk; 16th Aug 2006 at 06:04.
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Hi, Silverhawk. I really don't care what you think of me and I can assure you that I'm not offended by your ignorant manner or your rude Private Message.
My question was simple and re-reading what I wrote, I really can't see how I was professing to be knowledgeable on the subject. You obviously can't add anything constructive to my simple request for information so please go away and do something useful with yourself.
Thanks again to the folks who took the time to post useful answers.
My question was simple and re-reading what I wrote, I really can't see how I was professing to be knowledgeable on the subject. You obviously can't add anything constructive to my simple request for information so please go away and do something useful with yourself.
Thanks again to the folks who took the time to post useful answers.
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Tire Wear
Good question!!!!!
As spannersatcx stated, the tire need not be changed immediately if the cords that are showing are 'wear cords'.
sir.pratt is also correct.
With aircraft tires, there is really no decent dynamic hydroplaning tread design. (Not like car tires.) So, the hydroplaning characteristics are mainly defined by tire pressure.
It is quite normal and quite acceptable to have a bit of wear cord showing. However, the purpose of this wear cord is to alert the engineers that a tire change is necessary....perhaps at the next stop where maintenance can be performed, or on the overnight stop.
I've worked for several airlines where specific, individual policy differed. Where I work now, the tire would be considered unserviceable and must be changed immediately. But, this is company policy...not mandated by the tire engineers or FAA.
PantLoad
As spannersatcx stated, the tire need not be changed immediately if the cords that are showing are 'wear cords'.
sir.pratt is also correct.
With aircraft tires, there is really no decent dynamic hydroplaning tread design. (Not like car tires.) So, the hydroplaning characteristics are mainly defined by tire pressure.
It is quite normal and quite acceptable to have a bit of wear cord showing. However, the purpose of this wear cord is to alert the engineers that a tire change is necessary....perhaps at the next stop where maintenance can be performed, or on the overnight stop.
I've worked for several airlines where specific, individual policy differed. Where I work now, the tire would be considered unserviceable and must be changed immediately. But, this is company policy...not mandated by the tire engineers or FAA.
PantLoad
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Ive seen worse. Upon asking the Captain and engineer they say as long as there is rubber around more than x% of the circumference (sp), then it is good to go. In this case the rubber wore through the metal reinforcements and at some stages even this was worn through. (Unable to see in this pic which was worse). Engineering at the home station put a limit on how many flights could be operated before a change was required. It was something like 8.
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Another insight into tyre wear for those without engineering experience, is that aircraft tyres are usually retreads. Any one tyre can be retread upto atleast 9 times, mainly due to their cost. The science behind retreading aircraft tyres is far more advanced than motor vehicle tyres. Testing before and after retread is done on every tyre, hence the reason for having a limit on the wear before retreading. The first layer of canvas is acceptable wear but as has already been stated, usally taken as an indication of the limit.
If wear becomes too excessive then the tyre cannot be retread, and airlines are displeased hence their own limits.
Most aircraft have an anti skid protection system and longtidudinal stability on the ground is maintained at high speeds by the Rudder, so you could say that the aircraft is flying even before it leaves the ground.
I always give a higher priority to the nose wheels for wear and condition, especially when their is only one.
If wear becomes too excessive then the tyre cannot be retread, and airlines are displeased hence their own limits.
Most aircraft have an anti skid protection system and longtidudinal stability on the ground is maintained at high speeds by the Rudder, so you could say that the aircraft is flying even before it leaves the ground.
I always give a higher priority to the nose wheels for wear and condition, especially when their is only one.
Last edited by sport; 16th Aug 2006 at 01:31.
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As I always like to explain to tech crew when questioning tyre wear
...Do you go by road ?
or
Tech Log write up?
Defect:- Tyre almost worn out
Rectification:- Tyre almost changed
I too prefer to change wheels when I can see the air inside but rest assured "Skippy123" all pilots and engineers know the tyre wear limits of the aircraft they operate like the back of their hand due to the extra work load required when a tyre fails at takeoff/landing speeds.
...Do you go by road ?
or
Tech Log write up?
Defect:- Tyre almost worn out
Rectification:- Tyre almost changed
I too prefer to change wheels when I can see the air inside but rest assured "Skippy123" all pilots and engineers know the tyre wear limits of the aircraft they operate like the back of their hand due to the extra work load required when a tyre fails at takeoff/landing speeds.
How about these? They look a bit flat on the bottom but im sure if you jack them up and spin them they will be good for a trip.....
http://www.airliners.net/open.file/1050502/M/
http://www.airliners.net/open.file/1050502/M/
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Although I'd want to run my hands over them for a close look for cuts, the ones in Skippy's photo do look OK. There's no shoulder wear and the outer treads are complete around the visible circumference. To quote a well known phrase or saying, they have at least three landings left in them. One for the destination, one for the return flight and one spare in case of a diversion.
In some companies - especially those aiming for nine retreads - policy would be to change them; in others that only go for three they'll stay on until the outer grooves have almost disappeared. That's a cost decision though. The tyres are safe until well beyond the economic limits.
I notice that Skippy123 didn't get a photo of the much more important brake wear indicators. Perhaps next time, eh?
That one from vs69 was lucky. If he'd gone on any further he'd have been grinding his expensive sports rims down as well...
In some companies - especially those aiming for nine retreads - policy would be to change them; in others that only go for three they'll stay on until the outer grooves have almost disappeared. That's a cost decision though. The tyres are safe until well beyond the economic limits.
I notice that Skippy123 didn't get a photo of the much more important brake wear indicators. Perhaps next time, eh?
That one from vs69 was lucky. If he'd gone on any further he'd have been grinding his expensive sports rims down as well...
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Perrin
OK I know you have been waiting for me to write in, 40 some years in the line game and there is plenty of time left in that tyre. the makeup of a A/C tyre as I have seen at the manufacture will allow it to go right to no thread all the way around and still be safe, I have never let a tyre go like that and more wear than that and had a failure. I rest my case.
Keep they flying I will try and keep out of the wild bits of the golf course.
Peter
Keep they flying I will try and keep out of the wild bits of the golf course.
Peter
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The picture is lacking in definition; it's too fuzzy to get much idea of tire condition. However, the tire on the left side of the picture shows visible tread depth on the shoulder and centerline of the tire, and the tire on the right has good shoulder appearance.
Tires, even retreads, are very expensive. Relatively few landings come out of a set of tires. Dividing the cost among the tires by as few landings as are had, means every landing is expensive on a tire by tire basis. No one wants to let a tire get to a dangerous condition, but changing out a tire early is also not cost effective, and doesn't enhance safety either. Further, when the tire is removed from the wheel assembly, it's not like changing a car tire. The process is long and expensive, and requires nondestructive testing and certification on each component of the wheel assembly...all for a simple tire change.
For aircraft operating on a scheduled basis, such work is routine, and is done when the aircraft reaches a point in it's operation when the downtime can be had, and when it occurs at a base where the work can be done.
I don't see anything in the photograph, fuzzy though it may be, that might lead one to believe it's unsafe.
Tires, even retreads, are very expensive. Relatively few landings come out of a set of tires. Dividing the cost among the tires by as few landings as are had, means every landing is expensive on a tire by tire basis. No one wants to let a tire get to a dangerous condition, but changing out a tire early is also not cost effective, and doesn't enhance safety either. Further, when the tire is removed from the wheel assembly, it's not like changing a car tire. The process is long and expensive, and requires nondestructive testing and certification on each component of the wheel assembly...all for a simple tire change.
For aircraft operating on a scheduled basis, such work is routine, and is done when the aircraft reaches a point in it's operation when the downtime can be had, and when it occurs at a base where the work can be done.
I don't see anything in the photograph, fuzzy though it may be, that might lead one to believe it's unsafe.
Actually, giving the focus some credit, they don't look too bad at all!
On a Puddle Jumper these could possibly be useful for another day, or so, depending on where it lands next.
Of course - if it doesn't go anywhere else they will last quite a while!!
On a Puddle Jumper these could possibly be useful for another day, or so, depending on where it lands next.
Of course - if it doesn't go anywhere else they will last quite a while!!