A lollipop stuck to my wing???

[Glen Davis]

My buddy is looking at a 1980 M20K.  I have a 1984 J.  On the K he is looking at, there is a device that looks like a lollipop under the wing.  The seller says it is a "squat switch".  My J doesn't have it.  What is it and what is it for?  Also, his electric trim works at cruise but seems to show down during the final approach phase.  Mine works the same at all times.  Next, when you push the electric trim switch forward (toward the engine) should that make the nose go up or down? Finally, my stock instrument cluster (above the six pack) has fuel pressure but the K he is looking at does not.  Should the fuel pressure be in that cluster on all J's and K's?  Thanks.  Glen

 

[carusoam]

Glenn,

Your friend is probably sorta right…

The lollipop switch is an airspeed switch… no squatting involved…. These types of switches have shown up for a couple of reasons often measuring  engine hours after reaching a certain speed…

Chances are… he still has a squat switch because this aftermarket lollipop airspeed device didn’t remove the existing squat switch…. Too flimsy.

A real airspeed switch is hidden behind the instrument panel attached to the real source of air data… the pitot system…

The trim seems to be a bit out of touch as well…. They are constant speed and often match the speed of the flap system…. Raising and lower flaps and increasing or decreasing trim to match the change in the Center of Lift…. Click both switches together… trim and flaps… hold the trim switch for as long as the flaps are moving….  A Transition Training nugget of gold….   

 

Direction of trim switch travel….  I expect mine to be wired so that when the nose is pushing up… I push up on the switch, to trim down…. I push back on the switch to raise the nose….  A full flap go-around requires a long wait for the trim to come back to the T/O position… pushing the thumb against the switch can easily be over done…. The click of the tiny switch can’t be felt under ideal conditions…  there isn’t much ideal doing a full go-around with your thumb fighting and your arms fighting the nose…. (Practice makes this ideal, smooth, and easy….  )
 

The trim switch should be clearly marked and be meaningful…

My trim system is a BK KAP system… probably identical to all using KFC and KAP APs…

PP thoughts only, not a CFI.. or mechanic…

Best regards,

-a-

 

[Will.iam]

A picture of said lollipop would be helpful in identifying what it is as a picture is worth a thousand words etc. pressing the trim forward puts nose down trim. I have a K and do not have a fuel pressure gauge. I do how ever have a fuel flow meter which he should hVe also. 

[carusoam]

Continental engines often don’t get a fuel pressure gauge…

The M20R uses FF instead…

It would be nice to have FuelP for maintenance and problem solving reasons… 

Some Mooneys didn’t get vac gauges either….

Best regards,

-a-

[PT20J]

My 1978 M20J had a short metal strip with a perhaps 3/4” diameter disk at the end protruding from an inspection cover under the left wing that was an air switch for the flight time function in the factory-installed Davtron clock.

Manual Electric Trim (MET) switch forward trims nose down.

Trim issue should be investigated. Mooney trim systems that are not well maintained can get stiff. If MET is always used, this can go unnoticed until the trim gets so stiff that the trim motor does not have enough torque to overcome it or the clutch slips.

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[KLudwick]

A few notes - not all K's have fuel pressure as others have noted.  Pushing the trim switch forward towards the panel should result in 'down' trim and the nose going down.

Regarding trim speed, while BK systems run the trim servo at the same speed all the time, the Garmin GFC 500 (and other Garmin APs) features speed-scheduled trim.  What's speed-scheduled trim you ask?  The faster you're going, the more sensitive the trim and less is needed, so the trim servo does not run as fast.  On approach at slower speed you need more trim to counteract the speed/flap changes, therefore our speed-scheduled trim runs faster.  Another advantage of the Garmin GFC 500 over all others! 

[carusoam]

Great detail KL!

The non-speed sensitive trim of the aged BK system… is old style funky…

was that one click or two?   

Best regards,

-a-

[PT20J]

The OP didn’t mention what autopilot is in the airplane, but did say that the manual electric trim seems SLOW at approach speeds compared to cruise. According to Garmin documentation, the GSA 28 servos run FASTER at low speeds, so that can’t be the issue.

 

It makes sense to run the servo slower as speed increases as the trim becomes more sensitive at higher airspeeds since aerodynamic forces are proportional to dynamic pressure which increases as the square of TAS.

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[Yetti]

What flavor lollipop?