Close Call--Over a $9 Inner Tube!
Posted: Wed Aug 28, 2013 5:02 pm
Guys:
I just had another close call last evening, saved BTGOG, for being a dufus, not willing to spend $9 for a new inner tube. Before I relate what went down, let me say by way of background, that my Sting Sport LSA runs regular 4.8 x 8, 6-ply utility trailer tires and tubes. They are pretty cheap, running about $27-$40 each, depending upon make and model (from the OEM list); the associated tube is $9. But they don't last very long on my plane--especially the way I take off and land. If I'm landing a lot, I'll get 100 landings and 50-70 hours; lots of longer trips and I may get 100 hours on a (main-gear) set. That said, yesterday I put on my 17th set (1800 landings/take-offs) of main-gear tires. But,...a few sets back, I had asked myself "why am I changing out this perfectly good inner tube every time? I'll just wait and change it every 2nd or 3rd set." So I didn't change the tubes; that was my mistake and it almost came back to bite me.
After installing the new tires and old tubes, I started taxiing to check function. WTH? It feels like a freaking wash-board! Maybe they just need to get broken in (yes, a stupid thought, I know). Maybe a wheel nut is loose and I have bearing wobble? Maybe... Well, I was running through all the 'maybes,' all to no avail. So then, I did three test take-offs and landings--and got some really nasty shuddering each time the mains lifted off. Back to the hangar for more evaluation and analysis. Then, 5 minutes after putting the plane away, I'm sitting at my desk 7 feet from the left main, when the tube explodes and the main settles to the concrete in a loud hiss, very nearly scaring the crap out of me! Holy ****! Good thing that didn't happen 15 minutes ago, when I was out there landing and taking off--or tomorrow, on the trip I was going to make up north to Indian country airport KO21.
And you know the culprit? It was that re-used inner tube. You see, last night I did some research and discovered (what most of you probably already knew--but I haven't seen elucidated here) that you are not supposed to use the old tube in a new aircraft tire. Tube use results in the tube growing up to 25% in size. Getting that expanded tube to fit correctly in the new tire--without a dangerous fold or wrinkle--is problematic. A wrinkle finally caught up with me--and almost made for a really bad day. We put new tubes in both those tires this morning and all was hunky dory again.
And here's another little factoid (if you can believe everything on the internet) I picked up during this adventure. You know how bias-ply tires often get flat-spot lumpiness from sitting under load? Well, this is exacerbated during the first 12 hours after a new tire is initially filled with air, because during that time, the tire slowly expands and fills out. So, avoiding that severe initial lumpiness is just a matter of either (1) leaving the new tires and wheels off (totally unloaded) for 12 hours; or (2) Jacking the load off (no pun intended) each main for the same amount of time.
Anyway, that's what I love about aviation: You learn something every day! And from now on I won't be trying to save a lousy 9 bucks, by not putting in a new tube, when I install a new tire on my Sting Sport.
Rich
I just had another close call last evening, saved BTGOG, for being a dufus, not willing to spend $9 for a new inner tube. Before I relate what went down, let me say by way of background, that my Sting Sport LSA runs regular 4.8 x 8, 6-ply utility trailer tires and tubes. They are pretty cheap, running about $27-$40 each, depending upon make and model (from the OEM list); the associated tube is $9. But they don't last very long on my plane--especially the way I take off and land. If I'm landing a lot, I'll get 100 landings and 50-70 hours; lots of longer trips and I may get 100 hours on a (main-gear) set. That said, yesterday I put on my 17th set (1800 landings/take-offs) of main-gear tires. But,...a few sets back, I had asked myself "why am I changing out this perfectly good inner tube every time? I'll just wait and change it every 2nd or 3rd set." So I didn't change the tubes; that was my mistake and it almost came back to bite me.
After installing the new tires and old tubes, I started taxiing to check function. WTH? It feels like a freaking wash-board! Maybe they just need to get broken in (yes, a stupid thought, I know). Maybe a wheel nut is loose and I have bearing wobble? Maybe... Well, I was running through all the 'maybes,' all to no avail. So then, I did three test take-offs and landings--and got some really nasty shuddering each time the mains lifted off. Back to the hangar for more evaluation and analysis. Then, 5 minutes after putting the plane away, I'm sitting at my desk 7 feet from the left main, when the tube explodes and the main settles to the concrete in a loud hiss, very nearly scaring the crap out of me! Holy ****! Good thing that didn't happen 15 minutes ago, when I was out there landing and taking off--or tomorrow, on the trip I was going to make up north to Indian country airport KO21.
And you know the culprit? It was that re-used inner tube. You see, last night I did some research and discovered (what most of you probably already knew--but I haven't seen elucidated here) that you are not supposed to use the old tube in a new aircraft tire. Tube use results in the tube growing up to 25% in size. Getting that expanded tube to fit correctly in the new tire--without a dangerous fold or wrinkle--is problematic. A wrinkle finally caught up with me--and almost made for a really bad day. We put new tubes in both those tires this morning and all was hunky dory again.
And here's another little factoid (if you can believe everything on the internet) I picked up during this adventure. You know how bias-ply tires often get flat-spot lumpiness from sitting under load? Well, this is exacerbated during the first 12 hours after a new tire is initially filled with air, because during that time, the tire slowly expands and fills out. So, avoiding that severe initial lumpiness is just a matter of either (1) leaving the new tires and wheels off (totally unloaded) for 12 hours; or (2) Jacking the load off (no pun intended) each main for the same amount of time.
Anyway, that's what I love about aviation: You learn something every day! And from now on I won't be trying to save a lousy 9 bucks, by not putting in a new tube, when I install a new tire on my Sting Sport.
Rich