pilotyoung
Well Known Member
I am posting this situation to keep someone else from making the same mistake I did. I am a new owner, I bought my RV-12 in February 2018. I have been a pilot for many years, but am new to maintenance.
Saturday I flew from KEET to KBGF to attend a fly-in breakfast. I took a friend with me so we could enjoy the fly-in together.
When I landed at KBGF I could not steer the aircraft. It started going left and nothing I could do would stop it. I was able to miss a taxi light by using the left brake. The aircraft ran off the runway into the grass and did a 180 before it stopped. So we were sitting in the aircraft, facing the way we flew in, and not knowing for sure what happened. I thought the left tire had blown.
We got out of the aircraft and the left tire was flat. The aircraft has slid on the wheel pants on the runway before it exited to the left. The airport manager and a couple other people came out to see if we were OK and we were. They help me jack the aircraft up, get the wheel pant off, and then we were able to pull it onto the runway, put a dolly under the left wheel, and tow it to the ramp. We then had breakfast and after eating I went to work taking the left wheel off. When I got it off, I was surprised that there was not a bad spot on the tire and it appeared normal. I put air into it to see what would happen. It was holding air except it was leaking through the valve stem. After tightening the valve stem, it held air. I reinstalled the wheel, and flew back to KEET. I went to the airport today and the tire was still holding air.
I was thinking about what happened to cause this. Several months ago I purchased a tool that came with new valve caps so I could check the tire pressure and add air with the wheel pants on. There is a hole in each wheel pant, and by inserting the tool into the hole (after aligning the value stem with the hole) you can take the valve cap off. I also bought an air chuck with a straight stem so I can add air through the hole. The tool is then used to put the cap back on.
Shortly after getting those new caps and installing them, I went to the hangar one day and the left tire was flat. I went through the procedure and added air. For several months the air pressure has remained good.
Last Thursday I decided to check the pressure in the tires and I added a couple of pounds of air to both main tires. Saturday morning I looked at all the tires and they all appeared to be normal.
After winding up in the grass and taking the wheel pant off, I realized the cap on the left valve stem was on crooked and therefore it was not tight. I realized that it had cross threaded when using the tool blind through the hole. The cap has a rubber seal in it so that when it is tight, it will seal the valve stem.
So after thinking about this entire situation, I realized that for the last several months the cap has been sealing the tire and keeping the air from escaping. When I didn't get it on tight, and flew up to 5,500 feet for the trip, the outside air pressure was lower and allowed all the air to escape and therefore I landed on a flat tire. I was fortunate that the only damage was to the wheel pant.
The moral to this story, and the reason I am sharing it, is that if you think there is a problem (tire losing pressure), there probably is. I had wondered for a few months why that tire was flat that day, and why it held air pressure for several months after I filled it. I now know, the valve stem was leaking and I did not check it. I should have investigated further and found the problem initially and before flying the aircraft.
I now have all the wheel pants off, and will have them off until I repair the left wheel pant. I like them off so I can see the whole tire and add air easily. I am wondering how much speed you really gain by having the wheel pants on.
I am going to Triple Tree this week so I will see what my cruise speed is without the wheel pants.
The people at KBGF were wonderful. The airport manager, a couple of mechanics, etc. helped get the aircraft to the ramp and then loaned me tools so I could get the aircraft flying. A friend who is an RV-12 owner and lives fairly close flew over and brought me a tire and tube, which I ended up not needing. But the friendless and helpfulness of aircraft owners, mechanics, etc, was wonderful.
I look forward to going back to the breakfast there again, and arriving in a less eventful way and getting to enjoy the breakfast and the company.
Thanks again to those people who helped me. I hope by sharing this story, my mistake, that someone will be able to avoid a similar situation.
Saturday I flew from KEET to KBGF to attend a fly-in breakfast. I took a friend with me so we could enjoy the fly-in together.
When I landed at KBGF I could not steer the aircraft. It started going left and nothing I could do would stop it. I was able to miss a taxi light by using the left brake. The aircraft ran off the runway into the grass and did a 180 before it stopped. So we were sitting in the aircraft, facing the way we flew in, and not knowing for sure what happened. I thought the left tire had blown.
We got out of the aircraft and the left tire was flat. The aircraft has slid on the wheel pants on the runway before it exited to the left. The airport manager and a couple other people came out to see if we were OK and we were. They help me jack the aircraft up, get the wheel pant off, and then we were able to pull it onto the runway, put a dolly under the left wheel, and tow it to the ramp. We then had breakfast and after eating I went to work taking the left wheel off. When I got it off, I was surprised that there was not a bad spot on the tire and it appeared normal. I put air into it to see what would happen. It was holding air except it was leaking through the valve stem. After tightening the valve stem, it held air. I reinstalled the wheel, and flew back to KEET. I went to the airport today and the tire was still holding air.
I was thinking about what happened to cause this. Several months ago I purchased a tool that came with new valve caps so I could check the tire pressure and add air with the wheel pants on. There is a hole in each wheel pant, and by inserting the tool into the hole (after aligning the value stem with the hole) you can take the valve cap off. I also bought an air chuck with a straight stem so I can add air through the hole. The tool is then used to put the cap back on.
Shortly after getting those new caps and installing them, I went to the hangar one day and the left tire was flat. I went through the procedure and added air. For several months the air pressure has remained good.
Last Thursday I decided to check the pressure in the tires and I added a couple of pounds of air to both main tires. Saturday morning I looked at all the tires and they all appeared to be normal.
After winding up in the grass and taking the wheel pant off, I realized the cap on the left valve stem was on crooked and therefore it was not tight. I realized that it had cross threaded when using the tool blind through the hole. The cap has a rubber seal in it so that when it is tight, it will seal the valve stem.
So after thinking about this entire situation, I realized that for the last several months the cap has been sealing the tire and keeping the air from escaping. When I didn't get it on tight, and flew up to 5,500 feet for the trip, the outside air pressure was lower and allowed all the air to escape and therefore I landed on a flat tire. I was fortunate that the only damage was to the wheel pant.
The moral to this story, and the reason I am sharing it, is that if you think there is a problem (tire losing pressure), there probably is. I had wondered for a few months why that tire was flat that day, and why it held air pressure for several months after I filled it. I now know, the valve stem was leaking and I did not check it. I should have investigated further and found the problem initially and before flying the aircraft.
I now have all the wheel pants off, and will have them off until I repair the left wheel pant. I like them off so I can see the whole tire and add air easily. I am wondering how much speed you really gain by having the wheel pants on.
I am going to Triple Tree this week so I will see what my cruise speed is without the wheel pants.
The people at KBGF were wonderful. The airport manager, a couple of mechanics, etc. helped get the aircraft to the ramp and then loaned me tools so I could get the aircraft flying. A friend who is an RV-12 owner and lives fairly close flew over and brought me a tire and tube, which I ended up not needing. But the friendless and helpfulness of aircraft owners, mechanics, etc, was wonderful.
I look forward to going back to the breakfast there again, and arriving in a less eventful way and getting to enjoy the breakfast and the company.
Thanks again to those people who helped me. I hope by sharing this story, my mistake, that someone will be able to avoid a similar situation.