ronschreck

ronschreck

Well Known Member
Yesterday I had a tire deflate in flight. The landing was uneventful but the wheel pant was severely damaged during rollout. This is the second time this has happened to me and I'm getting tired of repairing wheel pants! I mounted the pants IAW Van's instructions. If I were to do it over again, I would mount the pants higher so there would be some clearance from the ground if the tire went flat, thereby saving the wheel pant from damage. Has anyone done this? I know the race crowd (Bob) would frown on exposing more of the tire below the wheel pant, but what do the rest of you think? Comments welcome.
 
What do you think?

First LL then you. Do the guys up in the great white north have problems with the tires losing their seal when it gets cold? It has been cold (17 degrees) for us "down south", but not really that cold. What about tire pressures? You aren't running maypops are you.:D Keep up posted. Hope you can find a cause.

David
 
ronschreck said:
Yesterday I had a tire deflate in flight. The landing was uneventful but the wheel pant was severely damaged during rollout. This is the second time this has happened to me and I'm getting tired of repairing wheel pants! I mounted the pants IAW Van's instructions. If I were to do it over again, I would mount the pants higher so there would be some clearance from the ground if the tire went flat, thereby saving the wheel pant from damage. Has anyone done this? I know the race crowd (Bob) would frown on exposing more of the tire below the wheel pant, but what do the rest of you think? Comments welcome.
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Flying off of grass, my wheel pants are always beat up even raised up a bit. I don't think you can get them high enough to avoid damage when the air is gone.

What tires and tubes are you using? The last time I changed tires, I went with some tubes that cost almost as much as the tires (from Desser) and they have held up very well. In fact they don't leak! Last year they needed service one time just before OSH.

Now that I've said that, the next flight may well end with a flat. :)
 
did you examine the tube?

were you able to determine the cause? pinched tube, rubbed a hole, if not then the pressure might have been low. what else could it have been? run over FOD? hmmmm
 
Did you put air in it just before the flight?

I have a rule of letting the airplane sit overnight after I put air in the tire. I've had a few leak down from the valve stem core or expanding the existing leak over the years.
 
It's the moon phase, Ron...

...but seriously, I don't think there's a solution. It's just like one of your valve lifters starts clicking in your brand new car.....always a mystery.

Best,
 
Ron,
I've been biasing my wheel pants up higher on the RV8's lately for better clearance, but don't know if they're up high enough to prevent damage due to a flat. When you raise them up, you have to put a blister on the pant to accomodate the brake caliper bottom edge.
I'd be inclined to raise them up even further next time around since we seem to fly around in a big gaggle at 130 knots most of the time!:D

Regards,
 
It is worth the trouble to try and nail down the reason for the deflation, because given the wrong set of circumstances, it could ruin your day and ruin the day of some other folks. There are two likely sources, the valve itself, or the tube and valve stem. I had a tire go flat in flight on another type of airplane, and it was because there was a problem with the valve. Unless you check carefully when replacing the valve after a tire change, you may leave a small leak. I made a tool many years ago to check the tightness of the valve itself. Valve caps specifically for aircraft act as a double seal for the stem, just in case there is a leak at the valve. Those of us who use a stem extension to check tire pressure can't easily put a cap on, and can't easily tell if the valve is leaking (with a little spit on the top). I like the suggestion from the guy who said that he leaves the airplane overnight after checking tire pressure. Good idea, but you can't always wait. If your problem is with the with tube or valve stem, it could be caused by low initial pressure. It is prossible for the tire to rotate on the rim. Or, it could be a design problem in the tube itself. I have a car with tire pressure monitoring, and there is a big "why not" in my mind for tire pressure monitoring in our RVs.
 
I feel for you Ron - I've had to rebuild my right pant three times - twice due to flats. The first was clearly because I had too little clearance, and the pant cut the tire. The second is still a mystery - happened during breaking, but the tire and tube looked fine - in fact, I'm still using the tube, countless tire changes later. As a member of the "sliding down th runway on the wheel pant, leaving shards of glass behind" club, I don't think you can raise them enough to avoid damage.

I am also religious about metal tire valve caps with gaskets - I take the nose of the pant off to check tires, and with Air Stop tubes, only have to do that once or twice a year, but it is the best way I have found to make sure the caps are tight.

I guess that I have always figured that the goal is to keep the tire from going flat - as Terry said, a flat tire can really ruin your day if you get surprised, or the runway is narrow. Fixing the wheel pant is a frustrating exercise reminding me to make sure I don't blow the tire in the first place.

Paul
 
Update

I may have found the cause of the flat. A tiny metal chip was found inside the tire. It was not imbeded in the rubber, just sitting there lose. The tube had a small pinhole that could have been caused by that metal chip. Who knows? The first flat was caused by a defective valve. I always try to let the plane sit overnight after changeing tires or repairing a flat. That's good practice but wasn't going to help in the two incidences I have experienced. I'm willing to accept that an occasional flat is unavoidable and would just like to know if there is a way to protect the wheel pant when it happens.

FWIW: I use Michelin AirStop tubes and Goodyear Flight Special II tires. I don't scrimp on the rubber.

(Many thanks to Tad and Terry Sargent for helping me get the plane into their hangar and taking me home to make the repair. You're the best!:))
 
Just a thought about fairing height

I studied the tire dynamics a little bit and the higher you go with the fairing the more the conflict between the tire and the fairing. This is true in the front , rear and on both sides. OK I'll shut up now.

Bob Axsom

P.S. Sorry one more piece of info. I installed new inner tubes from Michelin (Airstop) last year at annual in January. One was very unreliable and went completely flat a few times. I looked at the valve core and saw damage on the outer seal where it had apparently been run in until it was cut. I replaced it with the cheap 40 cent aircraft valve core from Aircraft Spruce and it was a little better but no good either. I bought the high pressure valve cores the long and the short. Both worked but the long one required a little playing with on inflation. The short one works very well and has stopped the slow leakage problem. Part #9914A in the catalog.

B. A.
 
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Speak up!

Bob Axsom said:
I studied the tire dynamics a little bit and the higher you go with the fairing the more the conflict between the tire and the fairing. This is true in the front , rear and on both sides. OK I'll shut up now.

Bob Axsom
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Bob,

Always good to hear from you. I figured you had already visited this issue. You seem to study anything and everything that sticks out in the airstream. If it was just a matter of speed I would drop the wheel pant down or even put smaller wheels and tires on the RV. Heck, I even made a carbon fiber wheel pant for the tailwheel, but that has never been known to go flat on me. ;)
It just burns me up to have to repair the wheel pant every time a main tire goes flat. I went for three years with no tire issues but lately the tire gremlins have found my number. Aaargh!:mad:
 
Carefully!

tinman said:
Just for education...
How do you go about moving a bird with a flat tire?
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Some FBO's have a little dolly with three or four castering wheels that you can put under the flat tire and slowly roll it to the hangar. Something like this.

In my most recent case the leak was slow enough that I pumped the tire up and moved the airplane before it went flat again.
 
Would it be possible to design an internal run flat disc on the wheel assembly to allow a tire to run flat without damaging the wheel pant?
 
DAGO said:
Would it be possible to design an internal run flat disc on the wheel assembly to allow a tire to run flat without damaging the wheel pant?
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As far as I can tell there are two designs for run-flat tires. Michelin?s PAX run-flat tire has a polyurethane ring inside. A run-flat by Bridgestone uses reinforced sidewalls so a vehicle can be driven after a flat. Both are tubeless tires. It would take some engineering to adapt the technology to our aircraft tires, but I sure hope someone takes the ball and runs with it!
 
Afrter installing mij wheelpants, I let the air out of one tire to check the clearance. The pant will not touch the ground or the tire, but that is sitting still, not rolling. Anyway, at least the wheelpant will not get damaged when the tire disinflates over night, when it is parked.

I installed the front wheel pant about 3/4" higher than Van's instructions to get max. ground clearance. This also means the wheel rim is lower than the wheel pant, so no damage to the pant, even in case of landing on a complete flat tire.

The idea of the ring inside the tire came to mind, when I was going over all the posibilities of an accident with the nose gear. You have to use a tubeles tire though,to be able to install the ring inside it and our wheels are not made for tubeless tires.

Regards, Tonny.
 
Aircraft Spruce

Doyce Graham said:
Pardon my being dense but which catalog has 9914A referenced in your discussion of tires/valve stems
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There are two small listings in the catalog mixed in with the "Axles-Brake Valves" information in the LG section. It is a little hard to find. They offer three different valve cores and the 9914A is the one that worked for me - it is the short version of the high pressure valve cores. In the 2008-2009 catalog they are near the bottom of page 245. The Aircraft Spruce Part # is 06-00396 and the cost is $1.39 (in the catalog).

Bob Axsom
 
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Look at early Cherokee's with their wheel fenders to get an idea what it might look like. Or better yet the current JACK IN THE BOX commercial with their "bowl cuts" :)
 
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