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My opinion of how the LNC2 landing gear system works and how it should work.
First of all the Master has to be on and all associated CBs closed.
Note: Running the pump in either direction closes the other direction sw.
Note: open means has enough pressure. closed means the opposite.
A) How the current LNC2 landing gear system works:
1) Landing gear sw up:
a) Up sw open, Dn sw closed. All OK. Pump does not run.
b) Up sw open, Dn sw open. Not OK. Pump does not run. *** problem ***
c) Up sw closed, Dn sw closed. Not OK. Pump runs. Up sw opens.
d) Up sw closed, Dn sw open. Not OK. Pump runs. Up sw opens. Dn sw closes.
2) Landing gear sw dn:
a) Dn sw open, Up sw closed. All OK. Pump does not run.
b) Dn sw open, Up sw open. Not OK. Pump does not run. *** problem ***
c) Dn sw closed, Up sw closed. Not OK. Pump runs. Dn sw opens.
d) Dn sw closed, Up sw open. Not OK. Pump runs. Dn sw opens. Up sw closes.
B) How the LNC2 landing gear system should work:
1) Landing gear sw up:
a) Up sw open, Dn sw closed. All OK. Pump does not run.
b) Up sw open, Dn sw open. Not OK. Pump runs. Dn sw closes.
c) Up sw closed, Dn sw closed. Not OK. Pump runs. Up sw opens.
d) Up sw closed, Dn sw open. Not OK. Pump runs. Up sw opens. Dn sw closes.
2) Landing gear sw dn:
a) Dn sw open, Up sw closed. All OK. Pump does not run.
b) Dn sw open, Up sw open. Not OK. Pump runs. Up sw opens.
c) Dn sw closed, Up sw closed. Not OK. Pump runs. Dn sw opens.
d) Dn sw closed, Up sw open. Not OK. Pump runs. Dn sw opens. Up sw closes.
If the landing gear does not come down and the pilot recognizes that it has not come down, the problem can be corrected by a quick opening and closing of the dump valve.
If the gear does not come up, the plane has to be landed and pressure removed from the hydraulic system by loosening a fitting.
95% of the time my system works correctly but that last 5% has cost more than $35,000 worth of repairs and a few extra landings to relieve high pressure.
With no ICs, only relays and diodes, Wolfgang has come up with an easily installable (took me 10 minutes to install, test and tie wrap) fix for the landing gear problems that many of us have had. It solves both the landing gear not coming down and not going up problem.
I have just installed the system and will report any problems as soon as I have them. So far, testing has gone just fine.
I do not claim to have any knowledge of how Wolfgang's system works. I just know what needs to be done.
Lorn
From: "Randy" <randystuart@hotmail.com>
Date: October 19, 2009 1:37:35 PM EDT
Subject: Re: [LML] LNC2 Hydraulic Gear Operation Fix
This looks like a relay that when it senses the Hi pressure switch being open, while the gear is up, shorts and closes the Lo pressure circuit. This will bypass the Lo pressure sensor when the sensor opens from the hydraulic fluid expanding. This type of fix does not stop the hydraulic fluid from expanding more and more as it heats up. The hydraulic fluid expansion can damage the hydraulic system. I have monitored this problem and have seen the Lo side exceed 2000 psi during this heat expansion in the summer months.
If this relay sticks the Lo sensor circuit will be on all the time regardless of the pressure sensor.
The ONLY way to approach this work around for the Oildyne pump problem is to REMOVE the pressure from the Lo side. Relieving the expanding hydraulic fluid and put it back in the reservoir where it belongs!!!!
This type of "Fix" that simply bypasses the open Lo sensor and does not relieve the expanding hydraulic fluid is insane and it's a ticking time bomb for gear failure!!!
Randy Stuart
LNC-2
----- Original Message ----- From: "Lorn H Olsen" <lorn@dynacomm.us>
Sent: Monday, October 19, 2009 6:18 AM
Subject: [LML] LNC2 Hydraulic Gear Operation Fix
A module to fix the gear operation failure problem in the LNC2 using
the standard hydraulic system is now available.
The problem occurs when thermal expansion has caused both HI and LO
pressure switches to trip rendering the landing gear hydraulic pump
incapable of operating.
This module will activate the hydraulic pump motor in the direction
selected by the gear switch when both pressure switches have been
tripped by high pressure thereby relieving the pressure in the
offending side.
The module is 2.5" x 1.5" x .75", weighs 2.3 oz. and has two pairs of
leads that connect directly to each pressure switch with 1/4" spade
terminals. No other wiring is necessary. Price is $250.00 each. Simple
installation instructions included.
Contact Wolfgang at 248-471-2000 or Wolfgang@MiCom.net
--
Lorn H. 'Feathers' Olsen, MAA, ASMEL, ASES, Comm, Inst
DynaComm, Corp., 248-345-0500, mailto:lorn@dynacomm.us
LNC2, FB90/92, O-320-D1F, 1,650 hrs, N31161, Y47, SE Michigan
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