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"IF IT ISN'T BROKEN, DON'T FIX IT"?

True, if you're talking about the water pump on your car; but we're not in this case.

As pilots and airframe and powerplant mechanics we have a different perspective and responsibility; being pro-active.

 

Who would be proud of this?

Here is my short dissertation to encourage examination of the landing gear wiring harnesses on your Comanche. If you haven’t already addressed this issue, now is a good time to check the condition of the wiring and switches.

Function; the landing gear wiring harnesses and switches control 2 circuits, the gear motor through the landing gear solenoid, and the gear down indicator light – “the green light”. The micro switches are DPDT [double-pole; double-throw] configuration. See the “moving_switch.avi” in the various videos page.

Examination; if the wires look shabby, get them out of there and replace with FAA-friendly MS22759 wire per AC43.13. Also don’t ignore the micro switches; they’ve served the airplane well; don’t ask them to do another 50 years duty without failure – replace them too.

Photo of another example

Prolonging this issue can expose you or someone flying an airplane that you service, to a problem that they may not be properly schooled in the proper procedure to follow if the gear won’t come down, or experience a green light failure.

If a problem arises during flight, it likely will add stress to the pilot’s work load. The competency of the pilot to handle and remedy the problem will dictate the outcome. If done incorrectly the outcome can bring grief to the airplane.


More Free Advice

Instrument panel replacement.

If you are replacing an instrument panel here are some points to ponder. With a one-piece left side instrument panel installed, access behind the panel is very limited. The opportunity is at hand and not much extra labor to accomplish during panel installation, to replace those items mentioned below. After the panel is installed, if you have a problem with a component then it's a worse problem.

1) Replace the landing gear selector switch on those airframes where that switch is installed in the panel, not below the panel.

2) Replace the landing gear solenoid on those airframes where it is mounted to the aft side of the firewall.

3) Replace the landing gear and stall warning indicator lights with real Mil-Spec press-to-test indicators.

4) You might as well replace the 5-amp and 30-amp circuit breakers for the landing gear system as long as you're spending money; they're cheap and good insurance too. Semi-simple to install on the singles; a little more difficult on the twins with the CB panel in the floor.

As you would expect, I sell some of those components. The landing gear selector switch purchase comes with a dandy color-coded diagram showing wire placement on the switch. No fumbling around with a wiring diagram and a helper telling you what wire mark goes onto which location.

Ron and John's panel in 400 Comanche
I don't recall who sent this to me
400 left side panel
One-piece panel

Can you imagine how time-consuming and expensive it would be to remove the instrument panel for access to the landing gear selector switch?

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