If it doesn't seem right, it probably isn't

[donkaye]

I arrived at the airport (KSJC) today to give a Wings Program Flight Review.  My student had recently gotten a hangar at the airport and by chance it was located right next to mine.  It took all of 2 seconds to notice that the nose wheel tire seemed deflated down to about half full.  I asked the student when he last flew and he said it had been about 6 weeks.  I had previously had tires that lost air over a period of time, but never that much.  Still, I thought maybe it was possible, but I still had that "feeling".  It turns out I have a compressor so we moved his airplane out and moved my compressor to a place where we inflated his tire.  It seemed to hold pressure so we proceeded to do the flight review.  We did the air work and came back to San Jose to do the required landings.  After the Tower had us circle for about 15 minutes, they informed us that there were 8 planes on final and it would be quite awhile before they could accommodate us.  We decided to fly over the hill to Livermore.  The Wings Program requires a long runway for some of the landings.  We did 4 different kinds of landings and a simulated emergency to a full stop.  We were about to take off to go back to San Jose when I asked him about fuel.  We had plenty, but he was planning a long cross country over the week end and fuel at KSJC is over $11/gallon.  So we went to the fuel island and loaded up.  I looked at the front tire and it seemed to me that it had gone down some.  Once again I was thinking that something just wasn't quite right, but the tire was nearly new and maybe it was my imagination.

We flew back to San Jose and were cleared to land on 30R, the runway used for takeoff for the Commercial Airliners--and there were 3 waiting to takeoff.  We touched down smoothly and within a second or 2 the nose wheel started shaking violently.   Yes, I knew what had happened.  The tire had failed.  Luckily, we were close to a turnoff and we were able to roll onto an intersection and clear the runway. Still, the Airport ran a FOD check that delayed the Airliners a few minutes.  It could have been sooo much worse if we hadn't cleared the runway, (or it had happened in Livermore away from home base and we had to deal with both a plane AOG and transportation back to San Jose).  The runway would have had to have been shut down.  As it was, it took about an hour for a tug from Atlantic to tow the plane from the intersection.

While there were no violations involved, commercial traffic wasn't impacted more than a few minutes, and we were lucky enough to have facilities that could easily handle the situation, the fact remains that in hindsight I should have listened to that voice in the back of my head that said "something doesn't seem right" and postponed the flight review until the student had the tire checked.

[Shadrach]

3 hours ago, donkaye said:

I arrived at the airport (KSJC) today to give a Wings Program Flight Review.  My student had recently gotten a hangar at the airport and by chance it was located right next to mine.  It took all of 2 seconds to notice that the nose wheel tire seemed deflated down to about half full.  I asked the student when he last flew and he said it had been about 6 weeks.  I had previously had tires that lost air over a period of time, but never that much.  Still, I thought maybe it was possible, but I still had that "feeling".  It turns out I have a compressor so we moved his airplane out and moved my compressor to a place where we inflated his tire.  It seemed to hold pressure so we proceeded to do the flight review.  We did the air work and came back to San Jose to do the required landings.  After the Tower had us circle for about 15 minutes, they informed us that there were 8 planes on final and it would be quite awhile before they could accommodate us.  We decided to fly over the hill to Livermore.  The Wings Program requires a long runway for some of the landings.  We did 4 different kinds of landings and a simulated emergency to a full stop.  We were about to take off to go back to San Jose when I asked him about fuel.  We had plenty, but he was planning a long cross country over the week end and fuel at KSJC is over $11/gallon.  So we went to the fuel island and loaded up.  I looked at the front tire and it seemed to me that it had gone down some.  Once again I was thinking that something just wasn't quite right, but the tire was nearly new and maybe it was my imagination.

We flew back to San Jose and were cleared to land on 30R, the runway used for takeoff for the Commercial Airliners--and there were 3 waiting to takeoff.  We touched down smoothly and within a second or 2 the nose wheel started shaking violently.   Yes, I knew what had happened.  The tire had failed.  Luckily, we were close to a turnoff and we were able to roll onto an intersection and clear the runway. Still, the Airport ran a FOD check that delayed the Airliners a few minutes.  It could have been sooo much worse if we hadn't cleared the runway, (or it had happened in Livermore away from home base and we had to deal with both a plane AOG and transportation back to San Jose).  The runway would have had to have been shut down.  As it was, it took about an hour for a tug from Atlantic to tow the plane from the intersection.

While there were no violations involved, commercial traffic wasn't impacted more than a few minutes, and we were lucky enough to have facilities that could easily handle the situation, the fact remains that in hindsight I should have listened to that voice in the back of my head that said "something doesn't seem right" and postponed the flight review until the student had the tire checked.

Just to be clear, did the tube fail due to the slow leak becoming a major leak or did the tire fail from being operated below specified pressure?

[skykrawler]

I'm sure there will be a lot of opposite responses.....but don't think I've ever seen a tire that doesn't loose air.    I just had to top up all four tires on my wife's Honda Pilot.

[M20F]

47 minutes ago, skykrawler said:

I'm sure there will be a lot of opposite responses.....but don't think I've ever seen a tire that doesn't loose air.    I just had to top up all four tires on my wife's Honda Pilot.

I am really going to get the ball rolling and suggest the reason is because you didn’t use nitrogen in the tires.  

[N201MKTurbo]

I have found these kind of leaks happen when you get a fold in the tube. It causes tiny little cracks at the crease in the fold. If you reuse the tubes for a long time this gets easier to do because the tubes expand over time while pressurized. 
 

If you talc them well, inflate them , then let all the air out to let them move into place before the final inflation, this doesn’t happen. Installing them without talc greatly increases the chance because the tube will stick to the inside of the tire. 

[N201MKTurbo]

52 minutes ago, M20F said:

I am really going to get the ball rolling and suggest the reason is because you didn’t use nitrogen in the tires.  

Inflating them with nitrogen means you only have to inflate once a year instead of every few months. It has nothing to do with leaking down over the course of a flight.

[N201MKTurbo]

I have also seen this kind of leak when the valve stem isn’t correctly lined up with the hole. It will cause stress on the stem and it will crack around the stem. 

[donkaye]

4 hours ago, Shadrach said:

Just to be clear, did the tube fail due to the slow leak becoming a major leak or did the tire fail from being operated below specified pressure?

The tire looked almost new.  We'll find out on Monday, when a new tire and tube arrive, what caused the problem.

[MikeOH]

3 hours ago, N201MKTurbo said:

Inflating them with nitrogen means you only have to inflate once a year instead of every few months. It has nothing to do with leaking down over the course of a flight.

I guess we must have well over 78% nitrogen air here in southern California since I only top-off my tires with AIR once a year!  You'd think I'd have more trouble breathing  And here I've always thought it was because I use Air-Stop tubes.

 

@M20F  You trouble maker!!

[PT20J]

Air is mostly nitrogen and the idea as I understand it is that the other substances in the air leak out faster than the nitrogen. But, every time you add air you'd be increasing the nitrogen concentration and it seems that eventually you'd have all nitrogen anyway.

[EricJ]

O2 molecules are only slightly smaller than N2 molecules, and they can both migrate out through the tread of a tubeless tire over time.  The N2 is inert, but the O2 will react with the rubber and harden it.   Racers leave stored tires deflated for this reason, so that the rubber stays as soft as possible by mitigating the O2 migration.   I don't know how much having an inner tube makes a difference, and we don't really care as much about the migration or rubber hardness on an airplane tire.   Harder rubber will last longer.   I've no idea what advantage an N2 tire fill might have on a small airplane.   Not enough for most people to care, anyway.    

[PT20J]

Fill with helium and get a useful load increase  (Wonder if landings bounce more, though)

[MikeOH]

46 minutes ago, PT20J said:

Fill with helium and get a useful load increase  (Wonder if landings bounce more, though)

Hydrogen would be better for that

[hais]

1 hour ago, MikeOH said:

Hydrogen would be better for that

And with the lighter airplane, I can slam the brakes harder, right?

[EricJ]

14 hours ago, MikeOH said:

Hydrogen would be better for that

Kaboom!

[PT20J]

15 hours ago, MikeOH said:

Hydrogen would be better for that

Yes, but it will ignite when I lock the brakes trying to make the first turnoff and wear through the tire.

[Kelpro999]

 Well, Did your student complete his flight review successfully?

[MooneyMitch]

Remember the Hindenburg !!!! 

[donkaye]

18 minutes ago, Kelpro999 said:

 Well, Did your student complete his flight review successfully?

Since the issue occurred on the last landing and it was a "slip to a landing" he passed his Wings Program, which qualified him for a flight review.

[wombat]

On 10/19/2024 at 8:14 AM, donkaye said:

The tire looked almost new.  We'll find out on Monday, when a new tire and tube arrive, what caused the problem.

What is the result after the new tire and tube?

[M20E for me]

Over $11/gallon!  I filled up last Saturday and, for the first time in a very long time, I paid under $5.00/gallon ($4.95).

 

[Will.iam]

On 10/19/2024 at 1:54 PM, PT20J said:

Air is mostly nitrogen and the idea as I understand it is that the other substances in the air leak out faster than the nitrogen. But, every time you add air you'd be increasing the nitrogen concentration and it seems that eventually you'd have all nitrogen anyway.

Damn never thought of it that way. Who knew i have 3 nitrogen concentrators on my plane!

[MikeOH]

6 hours ago, Will.iam said:

Damn never thought of it that way. Who knew i have 3 nitrogen concentrators on my plane!

No wonder aircraft tires are so expensive

[A64Pilot]

I had to go pick up someone in the C-210 years ago, pulled it out and the front tire was low so I had someone fill it up and cranked up and left after he did, when I landed the nose went down so far I was sure the nose gear had collapsed, but it was just a flat tire. I taxied off the runway, filled it up and it held air?

It continued to hold air too, I figure the valve stem must have gotten cocked to the side after being filled the first time, and the person who filled it being in a hurry didn’t reinstall the valve cap. Just a guess but nothing else made sense.

If you look at an aircraft valve cap, first it’s metal, but if you look inside of it you will see an O-ring, this O-ring would most probably have kept me from landing with a flat.

Nitrogen in tires is silly, maybe some justification in Oleo struts, but tires it’s just a profit for someone selling you something you have no need of.

 

Edited November 2, 2024 by A64Pilot

[Pinecone]

On 10/19/2024 at 7:54 PM, EricJ said:

Racers leave stored tires deflated for this reason, so that the rubber stays as soft as possible by mitigating the O2 migration.   I don't know how much having an inner tube makes a difference, and we don't really care as much about the migration or rubber hardness on an airplane tire. 

Race tires harden due to heat cycles.

Rarely do they last long enough to be effected by O2.  

No racers I know store their tires deflated.   Hard to do when they are on the car.