WN Personal 'Incident' Count

[3WE]

I quoted 'incident'...yes there's a danger of exaggeration here.

1. 3BS encounters a failure of some landing gear stabilizing strut with the plane wobbling to a stop on the runway, fire equipment being called for safety inspection and being towed in.

2. 3BS daughter encounters tire failure on takeoff with the plane stopping on the runway, fire equipment being called for safety inspection and being towed in.

3. 3BS daughter encounters weather radar failure before takeoff and returns to the gate for repair.

Compare this with Evan's harsh, judgmental comments on WN maintenance practices and his no-fly list.

Question to Flyboy: Should tires really ever fail at all on an airliner? Shouldn't there be some super strict inspection program with 100X safety factors ALONG with the ability to detect a problem during the walk around?

[flyboy2548m]

Question to Flyboy: Should tires really ever fail at all on an airliner? Shouldn't there be some super strict inspection program with 100X safety factors ALONG with the ability to detect a problem during the walk around?

At the end of the day, it's still just rubber filled with air (or Nitrogen). It can burst.

[ocelot]

How do you detect a problem during the walk around? Sure, there are some tire failures where you can tell beforehand if anyone bothers to look (gee, there's a big bubble swelling up on this tire, maybe it's having a bad air day...) but we probably already catch most of those.

Inspecting the insides of objects for embedded cracks isn't as easy as all that. It's difficult enough with things like turbine rotors that are supposed to be solid and uniform; tires (the walls/tread of tires, even) are neither.

[3WE]

How do you detect a problem during the walk around?

I dunno, I thought maybe like this:

...there are some tire failures where you can tell beforehand if anyone bothers to look (gee, there's a big bubble swelling up on this tire, maybe it's having a bad air day...).

It was a two part comment. I bet if you got new tires every flight, blow outs would be reduced. Add a fancy 3D X-ray system to check tires before each flight...

Yeah, what I just said is fantasy- BUT still, I was after some insight. I doubt tires are run till the cords show, but when are they declared worn out? What is the failure rate? What would it be if some earlier replacement criteria were used?

Same old issue- it is a cost: benefit decision, but slung rubber damages things, closes runways, takes planes out of service and causes slightly dangerous aborts and control issues.

I was just after a few details to see if the failure rate could and should be reduced. They seem a little bit common.

[ocelot]

Well, a new super-strict inspection program isn't really going to help much in the absence of a way to do useful inspections that's better than we already have.

Now, granted there are probably ways; it just needs someone with some ideas, a research budget, and a lot of patience for things that don't work out. E.g. I bet you can estimate the wear age of a tire without dismounting it by attaching a microphone, thumping it, and listening to the vibrations; the harmonics are bound to change as the rubber stiffens from age and thermal cycles and exposure to ozone and whatnot. The hard part is that every tire's likely to be different, so it'll likely take a lot of data wizardry to come up with a scheme that produces useful information -- that and converting what might work ok in a lab to a tool that a rampie can use on a hot summer day and get repeatable results from. And then after all that it might not do any better than current methods.

(note: I am talking out of my ass, in case you can't tell. but I think you'll find that x-raying tires isn't stunningly useful.)

As far as tightening replacement criteria, I don't know, but I'd guess that a substantial fraction of the failures seen arise from undetected manufacturing defects and other issues that can strike at any time, and that the failures are not mostly among tires that are due to be replaced soon. If they were, it would probably make economic sense to replace them sooner, as the operational issues caused by blown tires are expensive. But maybe not. The industry (and particularly some operators) doesn't always act rationally and nobody may have bothered to collect the statistical data needed to make such judgments.

[flyboy2548m]

Interestingly, the A320 seems to use up tires quicker than my previous types. In any event, I'm constantly seeing logbook entries to the effect "MLG #x tire wear out of limits, removed and replaced MLG #x tire". These are replaced as an assembly together with the rim, costs are around $10,000. Each.

In my nine-years as an airline pilot, I've experienced one tire failure on takeoff (on a CRJ-200) and have found one tire during a walkaround that desperately needed replacement (on an A320, a chunk was missing out of the tread).