|
|
G'day George,
My LNC2 kit is a similar vintage to yours.
VH-LPD
Yours is not an uncommon problem experienced by Lancair
320 owners. I purchased my LNC2 pre loved (am not a builder, just a flyer)
and was aware of a leak in the hydraulic system which the mechanics who
inspected the aircraft prior to purchase assuered me was internal and by
upgrading to the outback gear would surely be solved. The symptom was a
quick cycle of the gear motor every 30 secs or so on the ground.
So I
upgraded the gear and had the flap mod performed. Guess what..still burped
frequently when in the down and locked position (every 10-15
seconds) and less frequently in flight (every 15 mins or so).
Next
step, order seal kits and replace all the seals. Still no solution. I also
replaced the low pressure switch (not Lancair issue). This provided a
temporary solution but the problem returned, only worse. This time it
sounded like popcorn going off in the back!
I also then encountered
the "select gear down and nothing happens" problem (also quite
common)..moving the dump lever slightly causes the motor to cycle and the
gear comes down. The diagnosis was a possible leak from high to low pressure
across the dump valve. I then replaced the dump valve. Still no solution.
Adjusted pressure setting to <550psi in low pressure switch. Cycling
stopped but then gear unsafe light came on when taxying. That wasn't such a
good idea.
I also replaced the valve assembly (under the trim motor)
as there was an internal leak here which was causing pressure in the down
side during gear retraction..the symptom was a nose gear door which closed
in three jerky movements as pressure gradually bled back into the reservoir
from the low side.
Finally I had the electrical circuits re-wired in
accordance with original Lancair wiring diagram (someone had stuffed with
it) and replaced both pressure switches with Lancair parts (the
previous mechanic used automotive switches which were not compatible with
aircraft hydraulic oil and thus providied only a temporary fix).
Guess
what--problem solved--no more cycling except intermittent when up and
locked--I can live with that.
An additional problem I had while
resolving the hydraulic issues was a strange "buzzing" and mild vibration
above 140kts IAS..this appears to have been related to a nose gear door not
fully closing. This is also solved (I think).
Hope this information
is of some value..am sure you don't have all of the problems I had
!
Regards
Gerard
--------- Original Message -------- From:
"Lancair Mailing List" <lml@lancaironline.net> To: "Lancair Mailing
List" <lml@lancaironline.net> Subject: [LML] 320 hydraulics - 1989
kit Date: 20/07/04 00:10
To
anyone who has had this problem or knows of the solution:
A couple
months ago my hydraulic pump began cycling often, like every 15 to
20
seconds for a brief half second burst, in cruise at altitude, i.e. 85
or
9500 ft. It seemed to be altitude related, that is, the pump would
begin
cycling as I climbed above about 6000 ft. Previously, it would
never cycle
even over an hour or more leg.
1. I ordered from
Lancair, and installed, a new dump/bypass valve. The
symptoms/cycling
continued.
2. I ordered and installed a new high pressure hydraulic
switch. The pump
cycling continued.
There are no leaks, the
reservoir is full. There has never been any cycling
on the down
side.
Today, on another flight to get it to do something, it did
something. At
9500 ft. in cruise, the short bursts of pump cycling got
more frequent, then
the pump started running for longer periods of time,
then it came on and
just continued running. I listened and watched and
after about 20 to 30
seconds pulled the circuit breakers (pump and
relays). The gear did not
drop out of the wheelwells. I descended and
prior to landing, put the gear
switch down then pushed in the relay and
pump CB's. The gear came down
normally, three green, the pump turned off
and did not cycle at all all the
way in to shutdown.
I'll get it
up on jacks and try to sort it out. But in the meantime, can a
hydraulic
guru tell me if this problem is internal to the pump maybe? Do I
need to
replace the pump? If one of the actuator seals is shot the pump
would
cycle on the down side, right? Also, if an actuator seal is blown,
the
gear would fall out of the wheelwells with the CB's pulled,
right?
So, what is going on here?
George
Shattuck
N320GS
--
For archives and
unsub http://mail.lancaironline.net/lists/lml/
________________________________________________
Message sent using Dodo Internet Webmail Server
|
|