We've been cranking out the hours on our -9A zigzagging across the country, west of the Mississippi. We blew right past a thousand hours and are well on our way to the next milestone, whatever that is. With this, I've been beating home the expectation that we're no longer maintaining a perfectly pristine "new" airplane. We should expect new unique maintenance details as we proceed. Tanya says this shouldn't be any big deal as she is no longer "new" and pristine either! She also blew right through a milestone of her own of the big four Oh! (I love you too.)
Anyway, as we were buckling in on the ramp at Hot Springs, SD, headed home from the Vetterman fly-in, I tested the firmness of my "passenger side" brakes as I always do before she hit the starter button. Woah, left pedal went to the floor! "Hold It." ... I tried that left brake pedal another time or two just in case it was my imagination. Yeah, there is nothing there. I'm just bottoming out the spring on the master cylinder. I know she does the same check of the brakes when buckling in before firing the engine. It isn't on our pre-start "checklist", but it just makes sense and we do it religiously to know if we're going to have any control once the fan starts turning.
Given that I knew she was ready to hit the button, I asked how her brakes felt. "Uh, they are fine." She said, with not quite the absolute certainty that I was hoping for. "My left if mush. Are you sure?" "Here, you try!" She immediately vacated the captain's chair, knowing there was only one way to answer the question at hand, and words just weren't going to do it. So I unbuckled and hopped out for the walk around the airplane to look at the left wheel, expecting what we all expect at this point, a puddle of fluid on the ramp under the wheel. Nope, surprise number two, no puddle, no fluid anywhere to be found. And, of course, both her brake pedals felt perfect when I tried them too
. So we launched.
In the air, we fully briefed our brake failure plan, not expecting to have to exercise it, which we didn't the whole way home. Once safe in front of the hangar back home, I stated the obvious that 22C is grounded until this is resolved. We were tired and just walked away and fell into bed for the night. I hatched a plan the next morning to get parts ordered to rebuild, not just that one, but all four brake master cylinders. The rebuild kit is "MC-4 Rebuild Kit MCRBDS4" from Matco, $4.37ea. The logistics officer had the parts on their way just as soon as I stated the general plan.
Back at the airplane, before taking everything apart, yeah the pedal didn't magically fix itself. I also found the fluid reservoir much more full than I keep it. Also, when actuating that pedal, fluid would actually percolate up through the vent cap just a little. Yep, the Stat-O-Seal in the master cylinder had failed. A stat-o-seal is a standard piece of hardware that looks like a washer with an o-ring fused to the inside diameter. We pulled all four master cylinders and brought them home to the comfy-cozy garage for rebuild which took me about an hour to do all four.
I found that the stat-o-seals are an absolutely critical part of this design and both on my side (right, "passenger", starboard, slacker...) were in very bad shape. Those on Tanya's side weren't quite as bad off. What I saw seemed quite proportional to use. So, I think I have a new condition inspection age/cycle limited replacement item on the checklist.
That is the end of the story for now. It will be a few days (weeks) before final reassembly and bleeding as we're now in the middle of an annual condition inspection that will take us some time. This is another brake failure mode that we don't talk about too much, but is just as important. No brakes is no brakes.
My Brakes, "Your Brakes!"
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