Angier,
Sometimes solenoid type relay placement is over thought.
Consider that aircraft are in a state of continuous vibration and
subject to + G's in turbulence. The Master (continuous relay, weaker
pull in) is positioned upright to utilize the weight of the contact to
remain or return to the "on" state under certain
flight conditions. The pump relays (intermittent, stronger pull in)
may be placed upside down so that the same forces might assist in opening the
contacts in case the relay is "sluggish." Now, if you ask about the
starter relay .....
The most frequent cause of intermittent relay failure is from
holding it "in" too long causing overheating, coil wire coatings to melt or
otherwise fail. In wee Lancairs this happens because the
standard wiring diagram separately "fuses" the pump power and the relay coil
power. If one has the master on and pulls the pump breaker while a
pressure switch can activate a selected relay (lo pressure, up or down sw
position), it will eventually fail without any panel indication (transit light
is powered by pump power). One solution is to fuse the relays after the
pump breaker so that pulling the pump breaker removes all electricity from the
gear system.
In building, as in life, it's your choice.
Grayhawk
Consider why it is aviation practice to put bolt heads
forward.................
In a message dated 7/26/2012 10:22:22 A.M. Central Daylight Time,
N4ZQ@VERIZON.NET writes:
Figure
14-4 in the install manual shows the hydraulic powerpack, relays, etc. on the
back of the baggage bulkhead.
In this figure, the gear relays are shown
positioned 'up side down' as compared to the master relay. But nowhere in the
install manual is there any discussion about how to position these
relays...right side up, up side down, etc...., or WHY.
Apparently there is
a history of these relays failing and I'm wondering if it's best to just swap
them out for solid state relays.
Angier Ames
N4ZQ
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