At C-GDSI's last annual in November, we (Chris, my mechanic and I) noticed a slight weep of hydraulic fluid a the top of the right hand gear leg, right where it enters the fuselage. It wasn't a lot, but as I've written before, any sign of hydraulic fluid in an airplane is not good and needs to be investigated immediately. This is particularly important for hydraulically actuated retractable gear aircraft--for obvious reasons.
A quick look at the gear actuator inside the belly revealed that all was well--everything was dry. So were all the components of the gear system that I could see. That was the good news. The bad news was the leak must be coming from the brake system as that was the only other system in that area that ran on hydraulics (with the exception of the nose wheel oleo which used air/oil for damping.).
Both Chris and I agreed that it wasn't a big leak (Chris called it "moisture on the gear leg") and that no action was needed right away, but we would keep an eye on it.
Unfortunately, I forgot about it.
Until three months later, I noticed a small puddle of hydraulic fluid on the hangar floor beside the right tire. It was about the size of a quarter. Oh, oh. A quick inspection revealed that it was dripping from the hollow gear leg where the axle assembly is attached. There was also some fluid on the area we looked at previously where the gear leg attaches to the pivot assembly in the belly.
The diagnosis was pretty obvious. Since the brake lines run inside the gear leg, and since the upper pivot assembly was dry and bottom was wet, there had to be a leak somewhere inside the gear leg.
Crap. That meant the leg had to come off and that appeared to be no small task.
Both the leg and the pivot assembly (aka., trunion) that it's attached to are huge steel forgings designed to carry half the load of the airplane when it lands. A quick check of the log books showed no entry for the gear leg being removed since it left the factory in 1980. So they had been bolted together for some 45 years. Who knew how much rust had developed in there? Were they effectively welded together? How on earth were we ever going to get them apart?
Before I spoke to Chris, my mechanic, I did a little homework which consisted of referencing the Cessna Service Manual as well as the Cessna Parts Manual.
As an aside, I'm a firm believer that all pilot/owners of small aircraft should have a copy of both manuals and know how to read them. As our planes age, components inevitably break, leak or wear out. Simply taking your plane to a mechanic and saying "fix this" is fine, but it will cost you. Often big time. The mechanic has to diagnose the problem, possibly research it on the Internet, identify if any parts need to be ordered, wait for them to be delivered and then schedule your plane to install them. That takes time and time is money.
On the other hand, if the owner shows up with a reasonable diagnosis of the problem, hands the mechanic a list of Cessna part no's (or supplies the parts himself) and doesn't bring in his aircraft until the parts are in and the a block of time has been scheduled, the mechanic is happy. And so will be the owner when he sees the bill.
In my case, the exploded parts diagram in the Parts Manual came to the rescue. It clearly showed how the gear leg was attached to the trunion and most importantly, how the Cessna engineers had cleverly designed the hydraulic brake fluid to flow through a rotating part, past the gear attach point bolt and ended up at the disk brake caliper.
Here's the diagram.
As you can see, the key component was the "plug", no, 41, that fit between the leg and the pivot assy. Notice that there are not one, not two, but FOUR O-rings that are installed on that fitting. Dollars to donuts, at least one of those O-rings was leaking.
So armed with this diagram (and the part no's for the O-rings), I had a chat with Chris. He agreed with my diagnosis and put an order in for the parts. We scheduled to bring the plane in the following week.
I won't bore you with all the details involved in the repair, but I will mention a couple of things. First, the plane has to be jacked up off the ground--a long way off the ground--in order to swing the gear. It's a nerve wracking process. Large jacks are placed at key points under each wing and pump, pump, pump, up it goes seemingly into the stratosphere. The Cessna Cutlass is a big plane, well over 2 tons, and to see it suspended in space, creaking on two posts (plus a tail tie down) is unsettling to say the least.
Chris moved the gear lever to the down position and the wheels swung freely so we could access the single bolt that secured the leg to the trunion. He tapped out the bolt and then--miracles of miracles--the leg pulled right off!!! Hurray! I think the leaking fluid helped to lubricate the connection and prevent any rust from forming!
The old O-rings were quickly removed (two were badly deformed), the new ones installed, the gear leg reattached, the brakes bled and the plane--slowly--let down off the jacks.
Total time for the repair: 2.6 hours (at $110/hr,)
Total cost for parts: $8.00 (O-rings are cheap!)
I was back in business!
I'm so thankful for Chris and his expertise. Plus it's such a bonus to have a mechanic located on your home field. I've managed to earn his trust over the years and am super grateful he lets me work with him. He bills fairly for his work and I have complete confidence in his knowledge and ability to maintain and repair my plane.
Also, I like to think I'm not that guy. You know, the one in the old adage: Question: "What's the most dangerous thing in aviation?" Answer: "A pilot with a tool box."
