Hello fellow Dimona operators
Allow me to introduce myself to this group: I operate an H36 Dimona
built in 1983, serial number 3667, registration ZK-GPH, with about 1300
hours on it. I fly from Papawai which is a gliding club near
Wellington, New Zealand, and the aim is to use the motor glider to
accelerate aspects of glider flight training. I always enjoy the DOG
posts I read, especially the hints about what to look out look for . . .
and I sense it's now time for me to contribute.
I purchased this aircraft with a fresh annual, so all the fuel hoses had
been replaced. But when I had an empty fuel tank one day I thought I'd
dismantle the fuel drain tap, and the O'ring lurking inside crumbled as
I tried to flick it off the shaft. So the rubber hoses had been
replaced, but not ALL the rubber bits. For all I know the O'ring might
have dated back to 1983. I spent a few hours that night googling how
many general aviation flights had ended badly because the fuel had
drained from a leaking fuel drain during flight. Sigh. Actually, I
also had to replace the electric fuel pump because although it clacked
away it was unable to lift fuel into the carburettors. And the intake
filter at the electric pump had some white, fibrous stuff in it,
possibly from the previous GRP tank (it's now a metal tank). You might
judge that I'm paranoid about fuel (I am) and I like to check the
c=system fully from one end to the other.
But wait, there's more! Landing on a short runway means I depend on my
wheel brake occasionally, especially in calm conditions. Again, the
brake hydraulic hoses had all been replaced on schedule, but I became
curious about the other rubber bits in the brake system? First clue was
a binding park brake. Second clue was very dirty brake fluid when I
drained the left wheel calliper. The brake master cylinder was rather
difficult to access for removal, but inside it I found 6 O'ring seals,
plus a lot of gunk and corrosion product. Two of the seals were in very
poor condition, and 2 more were well worn. Fortunately I could figure
out the replacement O'ring types from the Parker-Cleveland catalogue
("master cylinder - push type with parking brake") because measuring
distorted O'rings is a tricky business. My next job is to pull the
slave cylinders apart and clean these thoroughly before reassembling
everything. And new O'ring seals. And use automotive brake fluid.
Lesson for me is to attend to entire systems, not just the big bits or
the bits that are easy to get at.
With kind regards
Martyn Cook
Pukerua Bay, New Zealand
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