Landing gear micro switchs

[lardsoup]

Preflighting the Arrow I was taught to check the landing gear micro
switches. OK great. There they are. I even work the switch to feel that
it's making contact inside. I was Master Mechanic in the Air Force and
repaired the Autopilot systems on the SR-71 and U-2 so I know about
airplane systems and parts and all, but what exactly am I supposed to be
checking? That they aren't caked in mud? That they are there? I can't see
if the lights are working while I manipulate the switch so what's the deal?
None of the CFIs can give me an answer besides, "check the landing gear
switches". I'll keep "checking the switches" on every pre-flight but can
someone provide a more detailed explanation on what I should be checking
for?

Thanks.

Lsoup

[john smith]

lardsoup wrote:
> Preflighting the Arrow I was taught to check the landing gear micro
> switches. OK great. There they are. I even work the switch to feel that
> it's making contact inside. I was Master Mechanic in the Air Force and
> repaired the Autopilot systems on the SR-71 and U-2 so I know about
> airplane systems and parts and all, but what exactly am I supposed to be
> checking? That they aren't caked in mud? That they are there? I can't see
> if the lights are working while I manipulate the switch so what's the deal?
> None of the CFIs can give me an answer besides, "check the landing gear
> switches". I'll keep "checking the switches" on every pre-flight but can
> someone provide a more detailed explanation on what I should be checking
> for?

That's pretty much it.
Check that they are not stuck and that that lights/horn sound when you
open/close the contact.

[Mike Granby]

For the lights/horn to sound, you'll need to have the master on. Not
sure I'd want to be playing with the landing gear and its switches with
power to the system. Imagine there's a problem with the gear control
circuit, and you "test" the squat switch, causing the gear to start to
retract. Could spoil your day...........

[Seth Masia]

I don't know how to check the electrical operation of the microswitches, but
they're critical. It's not just the squat switches, but if your Arrow, like
my Comanche, has gear-up switches (to turn off the gear motor once the
wheels are stowed), they'd better work. If these gear-up switches don't turn
off the juice to the motor, it keeps drawing power -- which can burn out the
motor and/or discharge the battery in flight. I had this problem and it was
expensive: I replaced two gear motors and experienced two inflight
electrical system failures before we finally traced the problem to a single
bad microswitch. Talk to your mechanic about this and do a continuity test
at annual time.

Seth
N8100R





"Mike Granby" > wrote in message
ps.com...
>
> For the lights/horn to sound, you'll need to have the master on. Not
> sure I'd want to be playing with the landing gear and its switches with
> power to the system. Imagine there's a problem with the gear control
> circuit, and you "test" the squat switch, causing the gear to start to
> retract. Could spoil your day...........
>

[Mike Granby]

Pipers terminate the gear-up cycle by means of a pressure switch. The
gear-up switches are for indication only.

[William Snow]

"lardsoup" > wrote in message
...
> Preflighting the Arrow I was taught to check the landing gear micro
> switches. OK great. There they are. I even work the switch to feel that
> it's making contact inside. I was Master Mechanic in the Air Force and
> repaired the Autopilot systems on the SR-71 and U-2 so I know about
> airplane systems and parts and all, but what exactly am I supposed to be
> checking? That they aren't caked in mud? That they are there? I can't
> see
> if the lights are working while I manipulate the switch so what's the
> deal?
> None of the CFIs can give me an answer besides, "check the landing gear
> switches". I'll keep "checking the switches" on every pre-flight but can
> someone provide a more detailed explanation on what I should be checking
> for?
>

There ARE a couple of things that need to be checked.

First you need to make sure that the switches are aligned with the J hooks
on the main gear. Make sure the wires are not disconnected, and that there
is no corrosion in the vicinity of the connections. This is to prevent
uneven wear of the switch and possible early malfunction.

Second ,there are about nine switches total in the Arrow system. A check of
all of them is impossible since a few are out of sight.

The main squat switch is in left gear wheel well, mostly hidden but visible
in a couple of positions. Make sure it is free of corrosion, has wires
attached and is in the open position while on the ground, gear down.

Principle checks are alignment, wires connected, no corrosion, mounted
tightly.

Hope that helps

W. L. Snow CP, IA, ASEL
N5381F

[Paul kgyy]

If it's an older model Arrow, check the wiring at the switch attach
point. The plastic wire housing gets brittle with age, and I
encountered a "2-green" situation in flight a while back when the
inability to flex caused a wire to break off at the switch.

[lardsoup]

Thanks again to all who posted.

Lsoup