Some help with tyres please

[Seagul1]

Would any of the experts please tell me something about the tyres when r they bad enough to not go. What do u use as a guide line or do u just go with what the maintainence says.Any good site addresses would b a great help THANX

[Hugh De Payen]

Seagul1 ,

Refer to Airworthiness notices (CAP 455), noice #5. If in doubt, using a black marker pen, highlight the grooves on the tyre. It makes the crews think they have more rubber than they actually have :D

[Sliding member]

Sounds like you are of the kind of engineer that we need more of these days, as for the question seagull1, just go with what the engineer says, chances are he wil have rotated the wheel anyway so the exposed chords are underneath out of your beady eye, (A trick our Scottish friends often use). Just make sure your landings are smooth and you'll be fine:D :D

[Willit Run]

Don't know what kind of plane your driving, but in a previous life on the Tri-Star, we were allowed to go down 4 cords before the tires had to be removed.
Bear in mind that the tire tread is about 3.5 inchs thick,(9cm) to 4 inchs when the tire is new.
You'll have to check your maint manuel for your companies limit!

[mono]

Jeez Willit,

I don't think I'm gonna fly on your a/c.

You are allowed to go through a certain number of cords if the wheel is cut, but not as a general wear limit!!!!!!!!!!

There has to be some tread on the bloody tyre to stop it aqua-planing. Most MM's will state a limit of 1mm tread depth over at least 75% of the tyre circumference. Although this can be less if some of the other grooves have say 2mm or more.

In the end the MM is the bible!

:eek:

[Flight Detent]

Not so Mono,
Back in my military days, we used to allow wear down to the third canvass layer B4 the tyre was considered worn out, that was on the Lockheed P3.
(Unless it was going to be retreaded, then only to the second layer)
But on the B747-200 and later series Classics, as long as some grooves are evident all the way 'round, usually most critical in the centre grooves of the tyre, the tyre is good, at least as far as treadwear is concerned!
Cheers

[phd]

I was always told by engineering that there had to be no cord visible anywhere on the side wall or tread of the tyre for the aircraft to be released to service after a flight. As soon as the cord became visible due to the tread having worn away the line engineer was supposed to perform a tyre change. Not seen it in writing though.

[Jet II]

phd has got it about right - at least on a line station. If cords are showing you should change the tire although it is permisable to leave it for one flight back to base.

That is assuming that the crew see the flat spot before we have had time to spin the wheel

:D :D :D

[mono]

Military, different ball game.

Me, I go by the MM and AWN. Just as an example the tyres on the 319/320/321 have metal cords, first it is difficult to wear through them. Second if you do they have a habit of detatching from the rest of the tyre and leaving a bloody great hole in the flaps or possibly the under wing skin (read fuel tank). Believe me it is true I have seen it. And finally there have been several incidents where a/c landing on wet runways have lost breaking efficiency due to aquaplanning as a direct result of insufficient tread depth on a number of tyres and over shot.

As Hugh states AWN # 5 refers and can be seen on the UK CAA web site.

Cheers.

:cool:

[Blacksheep]

Bloody Hell!!!

With some of seemingly happy to fly on the carcasses I don't think I'd like to fly with any of you!

Please leave wheel changes to Maintenance and try to keep the legends strictly for the crew room...

**************************
Through difficulties to the cinema

[Checkboard]

This is a link to the Dunlop Aircraft tyre (http://www.dunlopaircrafttyres.com/tyrecare/dm1172/contents.htm) manual, which can answer all of your questions. You can view it either online, or download it as a pdf. (NB: The aircraft MM takes precedence, of course)

From the manual:
Non re-treadable tyres.
At the first appearance of casing ply for bias tyres, for radials - remove when the steel or nylon- belt is exposed at the fastest wearing location.

Re-treadable tyres.
Tyres which are to be re-treaded should be removed before they are worn beyond re-treadable limits. -Based on the fastest wearing location, remove tyres when wear has reached the base of any groove at any point of the tread circumference. -Remove tyres, which have fabric exposed, irrespective of how much tread groove is remaining.

Note: Tyres found to be exhibiting the above removal wear standards on an aircraft, which at the time is at an out-station, may remain in service for a further flight/s but must be removed at the next earliest opportunity.

For certain very high speed tyres; nylon fabric reinforcement may be incorporated within the tread rubber. This fabric forms part of the wearable tread pattern and will be exposed during the life of the tread. Tyre wear should still be assessed in accordance with the removal criteria in paragraph 6.3.1

Note: Where operational or climatic conditions are conducive to aquaplaning; wear limits should be advanced to 2mm i.e. where wear has reached to a groove depth of 2mm remaining at any point of the tread circumference, the tyre should be removed.

Another tyre site you may find interesting shows some technical test data for under-inflation, fast taxiing etc: Desser Tire & Rubber tire care site (http://www.desser.com/tech/tirecare.html)

(You can see that they are American, as they can't spell "tyre" :) )

[Willit Run]

Mono,

I must have had my head up my arse! your are so right, i was thinking of cuts and not wear! my apoligies, PLEASE!

God, i hate being made a fool on a public forum!! oh, well, i'm human too!

[spannersatcx]

Firstly don't be confused between tread reinforcing cords and the actual carcass plies, this is mainly for the B747, Airbus is slightly different. The first ones you see are the tread reinforcing cords which are nylon the main carcass cords are steel plies. As an Engineer I am governed by the Maintenance Manual and not the manufacturers books.

The following is from the Boeing MM.

Wear removal limits
Main Base
Centre Rib tyres
Tyres should be removed from service when either of the following conditions is noted:
(a) Either of the grooves adjacent to the center rib is worn away for a length of 3 inches (7.5 cm) at any one location, or,

(b) The first layer of reinforcing fabric is exposed at the center of the tread for a length of 3 inches
(7.5 cm) at any one location.

Center Groove Tyres
As per (a) or (b) above except use center groove for wear determination.
LINE STATIONS
Center Rib Tyres
Tyres can remain in service as long as there is some evidence of the grooves at the center of the tread remaining at various points around the tyre provided there are no obvious flat spots.

Center Groove Tyres

As per above except use the center groove for wear determination.

Note 1: If passengers compliant of vibration immediately after rotation in the door 3 and 4 area are registered, check the main landing gear tyres for even tyre tread depth around the circumference of each tyre. If the tread depth over approximately 1/4 of a tyre circumference differs from the remaining 3/4 of the tyre circumference by 0. 1 80 (3/16) inch or more, replace the tyre.

Note 2: Tyres with flat spots through skids, aquaplaning etc may continue in service until return to Base as long as the tread grooves are still visible at the part of greatest wear. Note however, that excessively uneven wear on NLG tyres can cause NLG shimmy or vibration.

Note 3: TRAINING FLIGHTS. When an aircraft is scheduled for a training detail, the Ground Engineer should establish with Operations/Movements the estimated number of landings planned for the detail.

Tyres should have sufficient tread, above operators limits, to cover A) the scheduled training detail and B) the next scheduled commercial flight if a short transit time is anticipated.

Hope that helps

:cool:

[GE 90]

For crying out loud.
As I've said many times "Are you flying or going by road?"
You are looking for damage, wear, unusual wear and whilst you're down there missing tie bolts. The guy wiping his hands on the oily rag will advise if confirmation is required.:eek: :confused:

[Checkboard]

GE 90, in some parts of the world, and PPRuNe is a worldwide forum, engineering assistance is not always available. In Australia around 60% of our destinations were outports, with no engineering - so if you notice a flat spot at an outport you would like to know if the aircraft is going to be AOG or not before you spend ten minutes on the phone to engineering during a 25 minute turn-around.