C172 nose gear

[GauzeGuy]

Finishing up my preflight before my 5th attempt at a long XC solo, I ran across the scene pictured in the attachment.

I ended up cancelling as I wasn't sure why the strut was so far down, and also what the source of all the oil was (some on the tire and ground as well).

In chatting with a couple people, I was told that a simple test would have been to try to rise and lower the nose via the prop to see if it would sink all of the way down, or bounce back.

With respect to the fluid, is there really any good way to identify what the source is? I wasn't entire confident with the theory that was given to me that it was just oil spilled while adding oil prior to an earlier flight.

 

[flyingmoose]

The strut itself has two things inside it. Hydraulic fluid and nitrogen. There is a seal on the strut itself that if leaking will discharge fluid on the scissor links, tires, ground etc... The test to move the strut up and down to see if it settles is a good idea, they can get dirty and stick a bit. If it settles back down then you need to get some nitrogen added. If the seal is bad then they will need to get the seal fixed and add fluid as well. The strut you have appears to be leaking a bit from the dirty fluid look on the scissor links. I would of had them look at it and get it serviced up. On the other hand, if it wasn't bottoming out on the strut, I would have flown it and just kept the pressure off the nose wheel as much as possible.

You did the right thing by having them look at it. Im sure they will service it up just like new

 

[Clark1961]

Strut heights change a lot with changes in barometric pressure out here.

A couple things you can do: see if the strut is stuck and check the POH for allowable static strut extension. There should be a line in the POH which gives the acceptable range for amount of strut showing. I don't know what the 172 requires but it's probably within the range of 2 to 4 inches.

 

[Tom-D]

Most times the stuff leaking out doesn't look like what went in.

 

[douglas393]

Have not flown a C172 since getting my PPL a year and a half ago, but that looks pretty low from what I remember. However, as others have said it could be from a number of reasons. In my 182 which when I got it had less strut showing than the 172 depending on the ground it was on it could change a number of inches. Also if someone was sitting in the plane it would be lower than if no one was in it. My present AP keeps it fairly extended, it his belief it is safer, though I have no evidence to support it. My guess would be it was safe to fly, but the better part of valor, and safety would be if unsure scrap the flight.

As far as pushing on the prop to check it, I am not sure it would prove anything, and personally I do not like doing anything to my prop unless I have to, such as turning it a half rotation to allow the plane to be towed.

Doug

 

[Dan Thomas]

That strut appears to be leaking oil. It shouldn't be wet like that, thought it can also get oil if the engine is dripping some. Low strut pressure and leaking oil go together, too; as the oil is lost, the pressure drops because the gas volume inside the strut increases.

The seal is an MS O-ring. Buna-N, the material that dates from WWII or earlier. We have modern compounds that would last far longer but can't use them because they're not in the IPC. It's silly. The Buna rings will shrink in the cold weather and grab the strut barrel, and get dragged so that they suffer spiral fracture failures. Or they just get old, take a set, and start leaking. Dirt sticks to the oil and starts abrading the ring, too.

That strut needs rebuilding. Look at the cotter pin ends all sticking out, half undone. I would bet that the steering collar and torque link bushings are all shot and loose, too.

Dan

 

[denverpilot]

Hydraulic fluid is sticky. Oil is slippery.

Stick your finger in that mess. If it grabs your finger, it's hydraulic fluid. The strut is leaking.

If its slippery, it's used motor oil and leaking from somewhere else.

It looks to me like a combo of both, but if you go up where the black stuff looks "drier" you'll feel the difference.

Or if you get rags and clean it up, so you can see what's leaking more, the rag will get stuck in hydraulic fluid and you'll have to put some elbow grease (hmm, pun intended?) to get it off.

Both are black because they've attracted dirt. Be careful grinding all that dirt into stuff... Or getting it all over the piston to get shoved up into those O-rings later.