(Frank Ch. Eigler) writes:

Given the hand pump and CO2 backups for the Aztec's hydraulics, how
much benefit do you expect from a backup hydraulic pump? How
frequently do failures occur in light twins' hydraulic systems that
could have been prevented by a backup pump?

Good questions. I don't know the answers but here are some things I've
considered when thinking about another pump for my Aztec...

The CO2 is a last-ditch measure. Once it's blown, that's it. I would
be very reluctant to use it not only because it makes a mess but also
because once it's used gear retraction is not an option. What if you
blow it and one of the mains doesn't lock? It can also be misused -
blow it without the gear handle down and that's it.

The hand pump takes a lot of effort. We've had several gear problems
and I'm the one who gets to pump the gear while it's on jacks. Even
leaned over at the most comfortable pumping position, it's not fun and
it takes a lot of effort to get it to lock.

Sure, either of these methods *can* work, but in a stressful situation
(which is what it's likely to be if you're doing this), it's an
additional problem - another link in a chain. I would hate to have to
do a single-engine go-around while pumping the gear.

I have shutdown my left engine and landed. It was "just" a turbo
problem but I opted to shut the engine off. (I disabled the turbo but
still had low turbo oil pressure and I didn't want to run it even with
the wastegate open.) I was high and had plenty of time to think about
things before landing in nice flat Kansas City. Compared to not
having any heat in the middle of winter, losing the engine was a minor
problem.

However...if I had been further along my route, into the Rockies,
landing at an unfamiliar airport with high surrounding terrain, this
would have been a little trickier.

BTW, I like the idea of an electric pump for the backup. Maybe that
is getting completely ridiculous, but if both engines do die, I'd
like to still have easy flap control.

--kyler