How To Servicing Cessna 172 Nose Strut

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When I bought my 1970 Piper Cherokee 180 and the pre-purchase and almanac were completed, it was time to innovate my married woman to our new bird with a curt flight around our surface area. I was hoping to make a good impression.

The airplane stance was wrong as nosotros approached our plane on the ramp. The nose was sitting way too low. Ouch. The front strut was collapsed.

Considering it was a Sunday afternoon, the Augusta Aviation maintenance store was empty. I contacted the manager and was told that nothing could exist washed until the next 24-hour interval. I told my wife that our start flight would be another twenty-four hours, and we went out to eat.

The joys of airplane buying.

The side by side morning, I arrived to find my strut serviced with nitrogen by the maintenance crew. It was worth a try, since crumbling seals will sometimes leak in cold weather. Unfortunately, the strut collapsed in less than an hour.

DIY

An owner tin can participate in the maintenance of their personal airplane, only y'all've got to exist under the direction and observation of a document holder, as authorized past FAR 43.iii (d). The Document holder will watch yous work and approve your work when completed to their satisfaction. My shop assigned a mechanic to piece of work with me while I performed most of the required repairs. Working on your aeroplane can be educational, and information technology can save yous money.

The Oleo strut is a mutual shipping pause component found on many of our airplanes. Although like in appearance to a motorcycle front intermission, they are significantly unlike. The biggest difference is that at that place's no bodily spring, just gas under pressure. The shock absorber is hydraulic fluid flowing through pocket-sized openings. These struts are elementary, sturdy and provide years of trouble-complimentary service, and repairs to them crave only basic mitt tools. The rebuild took a few hours and required some new seals, a little hydraulic fluid and some compressed nitrogen. The seals are easily obtained every bit a kit for your specific airplane from most aircraft parts vendors. I completed the repairs for less than $200.

We began troubleshooting by replacing the Schrader valve core, located on the tiptop of the strut. This valve allows you to recharge the gas, like the fill stalk on your tires. The core is removed and replaced using a common tool. The rubber seals can go bad, and it is an easy ready, if you are lucky. Unfortunately, after I fabricated that repair, the strut proceeded to collapse in less than an hour.

Luckily, disassembling the strut for rebuilding is piece of cake. You drag the leaking strut enough to pull the strut shaft out of the housing. Sand bags on the tail of my Piper provided the required clearance. You've got to get rid of whatever remaining gas pressure and then remove the cycle and the tire. Y'all disassemble the strut torque linkage past removing a few fasteners. Then, if y'all look up into the strut from the bottom, y'all'll see a lock ring that must be removed. After that, you lot simply pull the shaft out of the housing.

When y'all pull out the strut, a lot of brilliant ruddy hydraulic fluid volition come with it, and then a grab pan is a necessity. The principal housing remains installed in the aircraft.

Once the strut is on the work bench, y'all remove heavy duty lock ring to permit removal of the seal bearing sleeve from the fork tube. A few minutes at the parts washer will remove years of dingy sediment from inside the fork tube. Removing and replacing the seals comes next.

A disassembled front strut. — The forepart strut inner cylinder is disassembled on the demote. Photo by Denny Katz

You lot reassemble the unit in the contrary order that you lot disassembled it. The strut must then exist refilled. This sounded complicated in the repair manual. In practise, it was simple. Yous push a hose on to the Schrader valve stem after removing the valve core. The other finish of the hose is inserted into a can of hydraulic fluid. The strut is and so expanded and compressed by hand. By using a clear hose, you can watch hydraulic fluid from the tin go in and the air bubbles come out with each stroke. Finally, you reinstall the valve cadre using a nitrogen tank, with regulator, to add sufficient gas pressure level to establish the correct ride height. If no leaks are detected, the job should be done.

Unfortunately, once more, the strut complanate in less than an 60 minutes. At that point, I was afraid that I might be facing something expensive. We pressurized the strut and poured some soapy water over it to await for leaks. It was immediately obvious from the bubbles around the base of the Schrader

A reassembled strut — The reassembled strut. Photo by Denny Katz

valve stem that we found the leak. The valve stalk torso threads into the top of the strut. I removed the stem, and when I did, I discovered that, some time in the past, a rubber o-ring was added to the metallic sealing gasket that was intended to seal the stem to the housing. I advisedly cleaned the machined surfaces to remove all prophylactic residue and installed a new metal gasket. We pressurized the strut, and it remained extended. My strut was now stock-still.

My supervising mechanic inspected and properly documented the work in the airframe log books, in accordance with FAR 43. I filed away the cognition for the next time downwardly the road I needed to fix a strut and save hundreds of dollars in the process.

Ane more quick annotation: you can rest easy if yous are worried about a strut plummet during taxi or landing. Your airplane was designed to avoid a prop-strike in the unlikely consequence of both a collapsed forepart strut and a olfactory organ wheel with a apartment tire.