Wolfgang,
It is a sad
day when removing a pump from the aircraft is too much effort to investigate
an anomaly.
Wolfgang wrote:<<We
would all like to get at the root cause of the problem but, as yet, that
hasn't happened. Likely because it's too much work to track down the actual
cause and fix it. …>>
As aircraft
owners we are responsible for knowing the configuration of the aircraft
systems. If something is out of the ordinary, investigate.
We know a lot about what the configuration should be and how it works and
behaves. We also know of configurations that do not
work. You may very well be holding the key to
a new, as of yet, unidentified failure mode, but we may never
know.
Wolfgang
wrote:
<<So far we only have a good plausible theory missing only
demonstratable proof.>>
If my tire has a flat and
I see a nail sticking through the side wall, I am rather confident in
assuming the nail was the source of my leak. Likewise, if
I open up a lock-up prone pump and find return springs, I will have a high
degree of confidence I have found the source of the problem.
Could there be a second cause? Possibly, but as of
yet, none have been
documented.
Wolfgang
wrote:<<…original suspicion of the spool coming off it's end point
(with the help of springs and airframe vibration) is in fact what's causing
the problem.>>
Springs
definitely - that is what they were designed to do.
Oildyne started adding springs to center the spool to the
Legacy pump in ~2003. Our system will eventually fail if
these springs are installed. Fortunately the vast majority of our
pumps do not have them. If you have springs installed,
simply remove them.
Vibration -
the evidence says otherwise. Measurements of various spool and pump
combinations required from 13 g's (9 year old 'soft' o-ring) to 70
g's (new 'stiff' o-ring) to move the spool. Aircraft vibration at
the pump was measured to be +/- 0.1 g (flying) to +/-1.3 g (engine start).
Vibration is not nearly sufficient to have any effect on the
spool.
Wolfgang
wrote:<<If it takes that much force to move the spindle against the
O-rings then those springs must be pretty darn strong. I find that dificult
to accept.>>
The springs
are very strong, 26 lb/in.
Wolfgang
wrote:<<Vibration
levels can exceed 70 G's>>
See
MIL-STD-810 for expected vibration levels in aircraft
environments.
Wolfgang
wrote:<<Yes, that would be easy . . . except . . . you can only
override one pressure switch at a time or overload the
system>>
I would
still like to know how push buttons can overload anything. And
why would anyone want to override more than one at a time?
Wolfgang
wrote:<<The items you cited are more a one-of condition
...>
I have
never had a thermal lock up, yet I use pressure gauges and the momentary
push buttons on a regular basis. They were originally installed to
deal with sticking VEP switches, but it is like getting a new tool.
After you have it, you can't imagine how you lived without out it. I
have already discussed the benefits of momentary switches not related to
hydraulic lock-up.
Wolfgang
wrote:<<In the event of a problem you have to make sure you push the
right switch.>>
One should
label the push buttons appropriately.
Wolfgang
wrote:<<Are you saying that Oildyne is putting springs in the spool to
center it when the pump is not running ?
Springs that
are not documented in the Oildyne spec sheet ?>>
Recall that
the Legacy pump configuration “CZZ” is proprietary to Lancair.
Companies generally don’t post proprietary materials
on-line.
<<You
seem to want to be "involved" in the anomalies of
flight.>>
Not
really. I avoid them by thorough examination, no matter
what it requires.
Chris
Zavatson
N91CZ
360std