Airspeed safety switch question on M20K

[Houman]

Hi,

 

I have 2 issues with my Airspeed safety switch, my mechanic is telling me that usually it is adjustable, but Mooney Tech support is telling me that it is not field adjustable and needs to be charged, and costs about 1300$ US.

 

I'm just wondering if anyone has any experience with the Airspeed safety switch and  how much labor would it usually take to change it.

 

Thanks !

 

 

[N231BN]

Can you elaborate on your issues? There is a procedure for adjusting the switch in the SMM and I have done it once. It takes a few tries due to "hysteresis" in the switch but it is possible to adjust it in the airplane using a pitot/static test set or a calibrated mouth. The switch is supposed to activate the landing gear at an increasing airspeed of 75 +/- 5mph or 65 +/- 5kts.

 

When I first picked up my 231 it would beep at me until 85kts on takeoff and was really annoying. It is a '79 as well so we probably have the same style switch. It is possible that the diaphragm is damaged though so if you could describe your issues it would help in diagnosing the issue.

[Houman]

Can you elaborate on your issues? There is a procedure for adjusting the switch in the SMM and I have done it once. It takes a few tries due to "hysteresis" in the switch but it is possible to adjust it in the airplane using a pitot/static test set or a calibrated mouth. The switch is supposed to activate the landing gear at an increasing airspeed of 75 +/- 5mph or 65 +/- 5kts.

 

When I first picked up my 231 it would beep at me until 85kts on takeoff and was really annoying. It is a '79 as well so we probably have the same style switch. It is possible that the diaphragm is damaged though so if you could describe your issues it would help in diagnosing the issue.

Thanks for your reply, here are my 2 issues and according to Mooney Tech support, it is the airspeed saftey switch.

The 1st issue is when trying to bring the landing gear up after takeoff, it would not come up unless I'm near 100 kts, I have to push the bypass bouton and same thing for low speed alarm, it only stops at 100 kts, so I guess it is out of adujstement, but Mooney tech support telling me that there is no way to do a field adjustement to the switch and that it needs to be replaced at a cost of 1500$.

When I bought 50% of the plane last year, my co-owner told me that this was normal, after diginig a bit, I see that it is not normal to have to push the bypass or the alarm up to 100 Kts, so going trough an owner assisted annual with my mecanic in 3 weeks, I want to understand the problem and solve it.

Since Mooney tells me that they will not take the switch back if that is not my issue, I have decided to do a test while the plane is on the jacks and see if it is really not adjustable or does it really need to be replaced.

Can you let me know how did you adjust it, since you have the same model and year, we most probably have the same switch, do you have pictures of it, if it was done by your mecanic, is there a way I or my mecanic can talk to him for 5 min...

Thanks !!!

[MB65E]

If it's a VEP switch with the gold alumnium casting, it's marked with torque seal to indicate tampering if the stripe it broken. Get with your A&p, put the A/C on Jacks, hook up a pitot static test box and try to retract the landing gear. This way you can dial up the A/s as needed. If you are good you don't need the box, sergical tubing will work. Then discuss with your IA if he is comfortable adjusting the switch. A flat blade screwdriver, common sense, and a watchful eye on the ASI you will be able to dial in the switch pressure. The switch is adjustable, but the manufacture of the aircraft and switch need to limit their liability.

Finally,

There could also just be some debris in the metered orifice. It might just need to be cleaned.

-Matt

[N231BN]

It's chapter 32-60-03 in the M20K Service and maintenance manual. The older style(silver aluminum housing) has a set screw on the side that you loosen then the knurled nut around the wiring connector is turned to adjust the switch. The setting changes when you tighten the screw again so it takes a little time to get it right. I had to rotate the instrument to access the set screw on mine, yours may be in a more accessable location.

 

PM me if you or your mechanic would like to talk.

[Smokin_Joe]

I had the exact same problem last year:  having to push the red over ride button to get the gear up and the airspeed warning sonalert going off when it should not have when I was in the circuit. 

 

Had to replace the airspeed  safety unit that sits behind the airspeed indicator.  Luckily the Mooney agent had a serviceable unit in a wreck that has worked well ever since.

 

Joe Luxford

Brisbane

Australia

[Houman]

I had the exact same problem last year:  having to push the red over ride button to get the gear up and the airspeed warning sonalert going off when it should not have when I was in the circuit. 

 

Had to replace the airspeed  safety unit that sits behind the airspeed indicator.  Luckily the Mooney agent had a serviceable unit in a wreck that has worked well ever since.

 

Joe Luxford

Brisbane

Australia

Thanks for your reply Joe, did you try adjusting it or was there no adjustement possible ?

I will have my annual in a month and I will try to adjust till, for now, I takeoff, level off at 400 feet to gain speed, at 90 kts, I bring the gear up without passing the button, and as I gain speed at 100 kts the gear comes up and alarm stops, once that is done, I start again my climb and remove takeoff flaps. It's not a problem with the Rocket 305 engine, but different from the usual takeoff

This is somewhat a new takeoff process some usually I would just ignored alarm and push the bypass button and wait for the gear to come up at 100 kts.