Shimmy should not be tolerated. It does all sorts of damage to that expensive nosewheel strut and its parts, the airframe, the instruments, the radios, and so on. There's an old myth that "Cessnas just do that." It's wrong. I have cured numerous instances of persistent shimmy just by dynamically balancing the nosewheel/tire assembly, the same thing your car gets when you buy new tires. The common, cheapo static balance that most airplanes get, if they get anything at all, will not stop it. It can even make the shimmy worse. Dynamic and static imbalance are two very different things. We've seen extensive and common stories of much money spent on new torque links and bushings and shimmy dampers, all of which only mask the root problem, the dynamic imbalance, and the imbalance just wrecks all that new stuff and you're soon back to the old problem. Do a search on POA for nosewheel shimmy. Endless posts. I have explained it too often already.
Dan, when you do a dynamic balance, do you add small lead weights to the rim just like a car tire or do something else?
Can or should? I would add air only to get it to the ramp. Then not fly until new tube/tire is installed. If the leak is too fast, you will need the airport to help tow it to ramp. Many small airports won’t have the personnel or the equipment handy. May have to call manager to NOTAM runway closed until you can get your plane clear. Don’t let bubba and his tractor tear up your plane. Think about carrying a spare nose wheel tube in your baggage compartment. The mains will be easier to find from a local mechanic. I personally carry a spare main tube and tailwheel tube in mine.
Yup. Stick-on weights. Aviall has them, but automotive weights also work. They are installed in the wheel so that centrifugal forces can't pull them off. That wheel has to be really clean and dry. Cessna published this way back in 1984: https://support.cessna.com/custsupt/contacts/pubs/ourpdf.pdf?as_id=42329 Now, when they say that all Cessna dealers have wheel balancing equipment, they are talking about the cheap static balancers, not the expensive dynamic balancers. Aircraft shops don't have the expensive stuff. I couldn't afford one, so I built my own, based on an ancient mechanical automotive dynamic balancer principle. Motorcycle shops often have electronic dynamic balancers that can balance a nosewheel. I usually found the torque links incorrectly installed, too, leaving slop in the system. The bolts pass through the ears on the fork and strut barrel, and through bushings ("spacers") that run in bearings in the torque links. Mechanics leave those bolts a little loose, thinking that the assembly rotates on the bolt. It does not. The bearings are supposed to rotate on the bushings/spacers, which are supposed to be clamped securely between the ears so they cannot move or turn. Leaving the bolts loose lets the stuff move around and the spacers eat into the ears, the bolts wear their holes on the ears into oblong shapes, and the slop becomes crazy. The elevator and rudder control hinges, if not properly done up, with the bolts a bit loose, will also have the bolts and spacers eating into hinge brackets. That gets expensive.
A few years ago, wasn’t a hard landing at all, but on roll out the plane started shaking badly. My first, weird, thought was that “somehow the propeller is out of balance”. It was quite a lot. My CFI even took a few seconds and then said he thought it must be the nose wheel. He took over and taxied off while keeping weight off the nosewheel. After we got a board with rollers and pushed it back to the hangar. I think it deflated instead of blew.
Flying an experimental & I check the tire pressure often, at least once a month and maybe more. After ten years I replaced the tires and tubes last year. I use leak guard tubes but they still need to be checked quite often. I'm flying a tail wheel and figure it would be a bit more interesting if landing with a flat ...
We teach our student pilots to follow the preflight checklist on our trainers, which includes checking tire pressure. As an owner, I only checked pressure now and then, usually with the change of seasons, or if the tire looked like it had lost pressure.
My experience with Flat Tailwheels is that they behave almost exactly like Flat Nose Wheels. Severe shimmy, doesn't usually affect directional control until slowed down to taxi speed, just like a flat nose wheel. Then it can be difficult to get it to turn and taxi off the runway. Using the elevator to reduce the weight on the flat wheel seem to help a little but not much. Don't want to go any further than necessary as damage to the wheel can occur. Surprisingly my experience with Flat Main Wheels have been mostly non-events. Actually while have had 3 or 4 flat nose and tailwheels each, I only recall one Flat Main wheel in a taildragger. Biggest issue was trying to get it off the runway after we stopped. Brian CFIIG ASEL
@Gilbert Buettner its been on the checklist going back to my primary training in '93, but always a visual check. I've never used a tire gauge, which is the procedure with my new club. With the wheel pants on it is a bit of a workout!
Why would you put this in writing, or even say this sort of thing aloud? Have you no superstitions at all?! [;-)
My local FBO/school has a Citabria in a hangar. The back of the hangar is all shelves with LOTS of wheel pants. More than their aircraft, so not sure where they all came from. I will have to ask.
My first airplane was a 1957 Cessna 172 with wheel pants. One winter day in SW Michigan, I landed at an airport in Dowagiac, C91. The only paved runway was covered in slushy, wet snow, and the airplane started to skid after touchdown, so I immediately took off again and headed home to Kalamazoo. At AZO, the runways were plowed and dry. When I landed, there was a loud BANG and the airplane turned sharply left, and then a second BANG and it straightened out. I realized that snow or slush had frozen inside the fiberglass wheel pants, and I suspected they were ruined. However, they survived just fine, and I learned a valuable lesson. Later, I owned a Cherokee, but I never put the wheel pants on. My Bonanza was a retractable, of course.
When I was bush flying in a Cessna 206 in Africa in the 1980's the nose tire went flat after landing. The strip I was at did not have any facilities and the clients I had dropped off had been picked up. I had an aerosol which was the equivalent to fix a flat or slime. I emptied it into the valve and the tire inflated. I took off normally and landed back at base 25 minutes later. Taxiing in the tire went flat again. However the aerosol had got me home. I am not suggesting anyone else should do this.
