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In a message dated 8/20/2003 10:40:44 PM Central Daylight Time, Rob@Logan.com writes:
There is nothing wrong
with the LNC2 or Legacy hyd gear system.
Rob,
There is something wrong with the wiring for the 320/360 series and maybe the Legacy if it is wired the same way.
The first wiring problem is as follows. Suppose that you have wired the relay coil power (to the landing gear switch) from a fuse or breaker (either sole source or containing several other items) per the directions. Suppose that you have a "leaky" system that you will someday fix. Suppose that you are irritated by the frequent running of the pump (either in flight or on the ground) and you pull the 50 A motor power breaker until you feel the need for hydro pressure but you fail to pull the relay coil breaker/fuse because of mental deterioration or there are other needed items on that circuit. This means that one of the "intermittent" relays (up or down) will be picked when the pressure drops because of the "leak" -- and it will stay picked until you engage the motor breaker. This will lead to the eventual failure of that relay or at least significant damage to it.
This failure has frequently been misdiagnosed. Here is how to fix it in a very straight forward way. Take the power for the gear switch (thus the relay coil) from the motor side of the 50A breaker and go thru either a 5A breaker or an inline fuse. This minor rewiring will ensure that when the motor breaker is pulled, all power to the entire hydraulic system is removed, including that to the coils. By the way, fix the leak.
The second problem involves the wiring to the "pump is active" indicator light. The power for that light is from a tap on the massive relay plate that connects the high current circuit (50A) to the motor when the relay is picked. This means that if the 20/22 gauge wire is shorted, it will burn before the 50A breaker pops. One solution is to use an inline fuse at the single indicator wire after it leaves the "I" terminals of the relays. In any event, diodes should be used to make sure one "I" terminal doesn't back feed the other. I believe the Legacy diagram includes the diodes. Perhaps an EE type could tell us if the diodes provide enough high current protection so that the fuse would not be necessary to protect the indicator wire - that is, the diode would disintegrate leaving an open circuit. I have both the fuse and diodes.
I have never heard of an indicator wire short in our flying insulators (non-carbon), but have heard of many relay failures. I had one from electrical system testing (cooked down relay) which lead to the rewiring of the gear switch power. Arnie had one (cooked up relay), along with a pressure switch failure, on our return from the 2001 Reno Races and he has since rewired the circuit. Others have had failures also.
Scott Krueger
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