Tire Problems

I like the shape of the Air Trac 500-5 tires for my application. The tread is rounded (a sectional cutaway would have the profile of an inflated inner tube) and I can closely fit my subfairings to them without any pressure points during operation. However, I have recently had two right main landing gear flat tires. The first was on 4-21-12 on the way home from the Hill Country Air Race and the second was on 7-23-12 on the way home from the AirVenture Cup Race. In both cases the middle of the tread was worn through completely in a spot an inch or more in diameter. After the first flat I went to an Air Hawk tire which has a square profile. I installed it and it didn't touch the subfairing. I was a little concerned but after safe operation with the subfairings since I made them and a successful landing I though it would be OK. I was wrong. On a subsequent landing with a little more stress the square sharp cornered flat tread caught the edge of the subfairing and caused significant damage to the subfairing. It required packing modeling clay around the tire and building it up again with new fiberglass. In some unrelated testing I found that the MLG subfairings were good for around 1 kt so I am not going to abandon them. I bought a replacement Air Trac and all seemed well again until the hot landing on 7-23-12 which instantly destroyed it and damage the sub fairing again (ground the bottom off on the concrete).

This obviously will not work for me. I looked in Aircraft Spruce's catalog to see what other tires had a rounded profile. I bought another Specialty Tires & Tubes Air Trac ($62), a Goodyear Flight Special II ($97.85) and a Goodyear Flight Custom III ($164.75) with Air Stop tubes for each (Total $531.60). All three are 6 ply rated.

I intend to come up with a good solution for myself but I thought I would share my findings. The Air Trac tires are very thin from the surface of the tread to the inside of the tire. I think that is an important parameter but I do not have an accurate way to measure it at this time.

I weighed the tires and came up with these numbers:

Air Trac = 4.5 lbs
Flight Special II = 5.4 lbs
Flight Custom III = 6.6 lbs

I photographed them and when they are grouped together the Air Trac is the one on the left and the Flight Custom III is on the right.




Note the 120 mph marking

Note the 160 mph marking

There is no speed marking on the Air Trac tire that I could see.



That is all the information I have at this time.

Bob Axsom

When I was just learning to drive...actually before I was driving, My Dad (who was a long haul trucker at the time) said "buy the best tires you can afford. Flat tires sux!"

So I'm running the oversized Wilkerson Retreads. They are stiff and wear like iron. They are heavier and I installed the pants higher for dirt/strip, so probably costing me some speed. BUT no flats. I would guess, the stiffness would allow a person to fair them much tighter and add subfairings.

remember: flats sux

Bob, You have a lot more experience with this kind of stuff then I do but a single round worn spot in the middle of the tire sounds a lot like a possible dragging brake on touchdown. The fact both were on the same side also supports the possibility. Any chance the brake calipers are not retracting or another malfunction in the parking break valve ect..? I would at least double check everything.
It also sounds a lot like the result you see with a catapult shot and the parking brake set. I think we can rule that one out in this case!

George

Bob, what are you using to Jack the aircraft when this happens away from home base?

I keep worrying about that kind of thing and not sure what I would do with my 8.

Bob Axsom said:

I think that is an important parameter but I do not have an accurate way to measure it at this time.

Click to expand...

I think your C-Frame or DRDT-2 could be used to get a pretty good measurement on this Bob! Just measure the depth the plunger goes before contacting the tread...

This is in strictest confidence

SmilingJack said:

Bob, what are you using to Jack the aircraft when this happens away from home base?

I keep worrying about that kind of thing and not sure what I would do with my 8.

Click to expand...

I do not carry anything to handle that situation. Airports with an FBO will be able to take care of your needs typically. One thing I found is helpful seriously, is a telephone of any kind to call for help. Who do you call? Well, in April I called 911.

This is just the kind of improvisation I do when faced with the problem in the worst case. Everyone else should get professional help. This is not a recommended procedure, it is the kind of irresponsible behavior you should avoid to prolong your fragile existence.

The tire is a different problem but if I have ground transportation, money or credit card and I can use available materials to build a stable platform under the wing tie down (my lift point) to a level that will allow a car jack to lift it. It is dangerous and with a tail dragger I suspect I would need to stabilize the plane with a tail tie down of some sort but what I typically do is put down a 3/4" thick piece of plywood as a base then lay two pieces of 2x4s not less than a foot long in parallel on the platform several inches apart, followed by two more such 2x4s parallel to each other on top of and perpendicular to the first two, then two more in log cabin fashion until the stack is high enough for the jack to work its magic. At that point I cap the stack with another piece of 3/4" plywood and if I have done it right I have a very stable base to put the jack on. Then I saw a notch in a short piece of 2x4 to accommodate (fit) the tiedown ring as the jack to airplane interface. I put the the jack and the interface block on the platform with careful alignment and slowly jack up the plane monitoring the alignment and the situation for any indication of instability knowing that the higher the jack is extended the greater the risk of it tipping over, puncturing the wing and injuring me.

If I am on dirt or grass like off the side of a runway I can build a support platform to my lift point then dig the ground out from under the wheel.

Bob Axsom

Understood Bob! I won't tell anyone

I'm sure this is one area you wish not to be a "Pro" at!

Thanks for the advice and I'll hope not to have to use it.

Best Regards,

I believe you have the right idea

hydroguy2 said:

When I was just learning to drive...actually before I was driving, My Dad (who was a long haul trucker at the time) said "buy the best tires you can afford. Flat tires sux!"

So I'm running the oversized Wilkerson Retreads. They are stiff and wear like iron. They are heavier and I installed the pants higher for dirt/strip, so probably costing me some speed. BUT no flats. I would guess, the stiffness would allow a person to fair them much tighter and add subfairings.

remember: flats sux

Click to expand...

I plan to go with the Flight Custom III on the right MLG first and I intend to verify that it can accommodate my flying style. I do not intend to pussy foot around an incompatible situation - I am what I am. I do have to retain the drag reduction of the subfairings so there is more to it than just upgrading the tire as I learned with the Air Hawk earlier.

Bob Axsom

Flight Custom III

I'd been using retreads from Wilkerson Tires for a couple decades with pretty good results. I decided to treat my Cessna 180 to brand new Flight Custom III tires last year.

It looks like these are good for about 150 landings on my plane, then the tread's all worn off. I was very disappointed. I've never had that much tread wear so rapidly.

Dave

JAcking an RV-8

SmilingJack said:

Bob, what are you using to Jack the aircraft when this happens away from home base?

I keep worrying about that kind of thing and not sure what I would do with my 8.

Click to expand...

Sorry for the thread drift, but.....

Search the threads, there are many suggestions.
One great way is to drill the wheel pant attachment bracket for the same diameter hole that is in the middle of your stock landing gear. Then, make a short steel rod that fits in that hole and sticks out several inches, and you can jack it with a scissor jack.

I've found that I can lift a wheel off the ground by putting my back under the wing just outboard of the tie-down and lifting. Then, an assistant can slide a block of wood under the steel rod.

I have had flats on my RV-4, all three times I was at my home field, once I knew I had a flat departing from a local fuel stop so I knew I would be landing on a flat tire, it went fine. One thing I learned is keep the airplane on the runway, do not come to a stop off to the side in the grass, I did this the first time thinking I would not block the runway, big mistake, neither the airplane nor the dolly want to roll in the grass, that was a real pain. We used a piano dolly with a 2 by 6 on it, between me my Dad and a couple of boys from the FBO we used our backs to lift the wing while the remaining person put the dolly under the tire, the flat tire does not roll off the dolly/2 by 6 so we then used our tow bar, I sat in the back of the Suburban and held to tow bar and we motored slowly back to the hanger.

All my flats have been from some Good Year tubes I bought at the local FBO, three in a row I don?t know what their problem was but they would split. I use the tubes I get from Van?s before and since and have never had problems with them.

scsmith said:

Sorry for the thread drift, but.....

Search the threads, there are many suggestions.
One great way is to drill the wheel pant attachment bracket for the same diameter hole that is in the middle of your stock landing gear. Then, make a short steel rod that fits in that hole and sticks out several inches, and you can jack it with a scissor jack.

I've found that I can lift a wheel off the ground by putting my back under the wing just outboard of the tie-down and lifting. Then, an assistant can slide a block of wood under the steel rod.

Click to expand...

On page 14 of August issue of Sport Aviation Lauran Paine, Jr. talked about a RV-8 travel jack from Avery Tools.

Preventing flats

Bob,

I had a few flats in the last hundred hours - interestingly on Air Hawke tubes I bought to replace with my last set of tires. After it happened twice I found the local engineer and asked some questions. I learn't a few things.

Wet Runways - The reason the ATIS says runways wet/damp (according to my local engineer) is to tell pilots to limit breaking action to avoid cooking the tires. Apparently aviation tires have organic components in them and a lockup in the wet causes superheated steam to "cook the tire". After which failure is going to occur not long in the future. If the tire failed in the middle, as opposed to wearing out on the outside edges it may be that this was the cause of your issue. If you still have the tire I would consider taking it to an engineer. They know how to spot the signs.

Talc - Must be used during assembly. Add lots and then add a lot more! Typical failure of the tube is to rub on the side walls and puncture near the tire/wheel intersection. Once this happens and the tire slips from the wall, the tube is chewed up and it appears to have split.

Inspect - Rotate tires (with the cheap Vans ones, perhaps every 100 hours)and have a really good look at the tubes. Signs of rubbing should be apparent. Replace the tubes before they fail. Add lots more talc. Check tire pressures regularly. The RV wheel fairings make it tricky. Low pressure can cause the tire to release from the wheel while cornering and then your tube is ruined. If you have a sudden flat while manuvering on a taxiway at low speed this is to be considered the likely cause.

Never put old tubes in new tires.

Anyway, you might know all of this... but I thought I would share the info I learned. Hopefully it saves someone some pain.

Cheers
Richard

I am curious for those that have landed in any of the taildragger models how direction control works out with one tire flat. My home strip is only 38 feet wide and I have thought about what to do if I do get a flat. There are some options within a 30 minute drive where I can get a nice 100 foot wide runway. Is directional control a issue with a flat or is is fairly easy to hold the runway center line on roll out. My plan now is to go for the wide runways but it sounds like perhaps that is a bit conservative and a return to home field would not be a big issue. Comments?

George

sailvi767 said:

I am curious for those that have landed in any of the taildragger models how direction control works out with one tire flat. My home strip is only 38 feet wide and I have thought about what to do if I do get a flat. There are some options within a 30 minute drive where I can get a nice 100 foot wide runway. Is directional control a issue with a flat or is is fairly easy to hold the runway center line on roll out. My plan now is to go for the wide runways but it sounds like perhaps that is a bit conservative and a return to home field would not be a big issue. Comments?

George

Click to expand...

Directional control has not been a problem with the flats I have had, all affecting the landing phase.

sailvi767 said:

I am curious for those that have landed in any of the taildragger models how direction control works out with one tire flat. My home strip is only 38 feet wide and I have thought about what to do if I do get a flat. There are some options within a 30 minute drive where I can get a nice 100 foot wide runway. Is directional control a issue with a flat or is is fairly easy to hold the runway center line on roll out. My plan now is to go for the wide runways but it sounds like perhaps that is a bit conservative and a return to home field would not be a big issue. Comments?

George

Click to expand...

I landed with a flat on a grass strip and it was pretty much a non-event. Just felt like one of the brakes was dragging a bit. Scratched the wheel fairings but no structural damage.

I checked my log tonight for landing numbers

The tire failed on it's 25th landing, the pavement was dry, the air temperature was around 100 degrees F, the tube was a new Michelin AIRSTOP, as always tire talc was liberally used at the time of the change, the tread looked fine except the area of concentrated abrasion failure, the tube looks like new except the tiny abrasion failure in line with the tire failure. The manufacturer name has changed from McCreary to Specialty Tires & Tubes. My examination indicates that the failure mode is concentrated wear due to a single aggressive brake action (lock up) and has nothing to do with the installation.

I changed to the Goodyear Flight Custom III this evening and it looks more robust. Time will tell how good it really is.

Bob Axsom

Lockup, side drift or big yaw. All 3 will give you what looks like a belt sander spot. If there are melted edges its a hydroplane. Ragged area is usually FOD. Also this tidbit from 43.13:

NOTE: Mechanics should be aware
that retread tires can be diametrically
bigger than a ?new? tire. While this
does not pose a problem on fixed
landing gear aircraft, it may pose a
problem on retractable gear aircraft.
Due to a 5 to 8 percent expansion of
the tire caused by the ambient temperature,
if a retread tire is installed
on a retractable gear aircraft, it is
strongly recommended that a retraction
test be performed. This is to ensure
the tire will not become wedged
in the wheel well during take-off and
landing operation.

Click to expand...

Meaning a bulging tire during a firm landing in cool weather may clear your fairing, but maybe not on a hunnerd degree day.

In an "A" you are along for the ride

Russ McCutcheon said:

I have had flats on my RV-4, all three times I was at my home field, once I knew I had a flat departing from a local fuel stop so I knew I would be landing on a flat tire, it went fine. One thing I learned is keep the airplane on the runway, do not come to a stop off to the side in the grass, I did this the first time thinking I would not block the runway, big mistake, neither the airplane nor the dolly want to roll in the grass, that was a real pain. We used a piano dolly with a 2 by 6 on it, between me my Dad and a couple of boys from the FBO we used our backs to lift the wing while the remaining person put the dolly under the tire, the flat tire does not roll off the dolly/2 by 6 so we then used our tow bar, I sat in the back of the Suburban and held to tow bar and we motored slowly back to the hanger.

All my flats have been from some Good Year tubes I bought at the local FBO, three in a row I don?t know what their problem was but they would split. I use the tubes I get from Van?s before and since and have never had problems with them.

Click to expand...

When an "A" model MLG goes flat you are turning to that side like you are standing on the brake.

Bob Axsom

I've been thinking ...(Oh God here it comes)

As I came to make this post I read Aerhed's post and that confirms some of my thoughts. I've been flying for over 30 years and more than 5000 PIC hours all in my little single engine land airplanes. For a stretch of 15 years I flew to work every day in Los Angeles so I have my own opinions about what is normal and acceptable to me. Prior to this year I have never had a flat tire on an airplane. In a few months I have had two with the the exact same visual characteristics. They were the same specific tire design and to the casual observer at least they were identical. The design of the tires with the rounded cross section that I liked reduces the surface contact to a smaller area of the tire concentrating the force and friction there. In both cases I was landing fast which increases both so, since I am not about to change my flying technique, I need to move to the more expensive and more substantial tire with heavier and broader contact surface that I think will accommodate it.

Bob Axsom