gear up alarm setting

[1964-M20E]

Where in the maintenance manual is the settings and procedures for the gear up alarm?

Changed throttle cable and  I've been looking for it.

 

[carusoam]

3 hours ago, 1964-M20E said:

Where in the maintenance manual is the settings and procedures for the gear up alarm?

Changed throttle cable and  I've been looking for it.

 

Sounds like a great question for @M20Doc...  (gear up / throttle sensor adjustment procedure)

I think Canada’s Memorial Day may be July 1.

Best regards,

-a-

[Vance Harral]

The Service and Maintenance Manual for our vintage of Mooney doesn't detail the adjustment procedure, see attached p. 5-11.  It just says the warning horn should be "actuated by the throttle control when the gear is not down-and-locked and the throttle is set at 10 inches or less of manifold pressure".  This statement triggers one of my pet peeves about these discussions: the microswitch that triggers the gear warning logic is a function of cable position only.  The MP reading you see at that particular cable position will vary with altitude and atmospheric conditions.  That's why those in the know talk about setting the switch to trigger at about XX inches of MP, rather than some specific MP value.

The M20J manual is a better reference, acknowledging that the switch is set to trigger "when the throttle is retarded to within 1/4 to 3/8 in. throttle position."  See attached screen shot.

While it's not official, and I'm not an A&P, my advice is to fly with a buddy and some painter's tape or a grease pencil or other temporary marking device, execute some normal final approaches, and have your buddy mark whatever throttle setting you use.  Back on the ground, set the logic switch accordingly.  On my 1976 M20F, the trigger can be easily fine-tuned via an adjustment screw, through a hole in the plastic cover surrounding the throttle quadrant.  My understanding is older airplanes with push/pull knobs are a little more trouble to adjust, but not unreasonable.

 

 

[EricJ]

The manual for my  early J model also says 10 inches, which is maybe a little low in some circumstances.    There's no perfect place for it since there's a fair amount of hysteresis in it as well, i.e., mine now comes on at about 10", but if you push the throttle back forward it won't shut back up until about 13-14".   This can get problematic for me on instrument approaches, since my power setting is often about 13-14" on approach, and if I had to temporarily pull the power back for a bit I and the alarm comes on, I may have to apply more power than I really want to to shut it back up.    So even though the 10" seems a little low to me sometimes, I don't want to turn it up since it'll get even more annoying during approaches outside of the IAF.

So, yeah, it is not a precision thing and it may take a few adjustments after flying it a few times to get it where it'll work best for you.

[PT20J]

Agree with Eric.  Many POHs refer to a MAP for the gear warning presumably because that’s an indication readily available to the pilot. It’s not a precision device. You want it set high enough so that it gives you adequate warning in time to check the gear but not so high that you get nuisance warnings during normal low power flight operations. Just fiddle with it till it works for you. 

[Hank]

In my C, the book says this:

[tony]

there is a little limit switch that rides on the throttle cable just under the instrument panel.  Adjust the switch how you want it to work.  you might need to fly it a few times until you have it how you want it.