RangerM20 Posted October 5, 2021 Report Posted October 5, 2021 I'm working on an early J model, when we put it on jacks and try to retract the gear, I don't get a horn nor a light in the alternate retraction button. The horn works once the gear is up and the throttle retarded. Does anyone know if the early J models had this feature, and if they did, what could the problem be? Quote
N201MKTurbo Posted October 5, 2021 Report Posted October 5, 2021 They changed things quite often back then, so it depends which serial number you have. Yours probably has a squat switch on the left gear leg, I would check there. Quote
N201MKTurbo Posted October 5, 2021 Report Posted October 5, 2021 24 minutes ago, RangerM20 said: I'm working on an early J model, when we put it on jacks and try to retract the gear, I don't get a horn nor a light in the alternate retraction button. The horn works once the gear is up and the throttle retarded. Does anyone know if the early J models had this feature, and if they did, what could the problem be? BTW the the horn working with the gear up and the throttle retarded sounds like normal operation. What exactly is your problem? Quote
KSMooniac Posted October 5, 2021 Report Posted October 5, 2021 That sounds normal to me for my 77 J. Sent from my LM-V405 using Tapatalk Quote
PT20J Posted October 5, 2021 Report Posted October 5, 2021 You need to know whether you have a squat switch or an airspeed safety switch. M20Js up through S/N 24-0237 came with squat switches and no bypass button. S/N 24-0238 and above have an airspeed safety switch and bypass button. SBM20-196A modifies earlier models with squat switches to install the bypass button. With a squat switch, the normal operation is as you describe. To actually test the warning and bypass feature, you need to use the procedure in the service bulletin. It’s not a bad idea anyway because it ensures that the squat switch is readjusted properly after the test. These switches can require adjustment as the pucks age. Skip Quote
RangerM20 Posted October 5, 2021 Author Report Posted October 5, 2021 It has the airspeed safety switch. My understanding is that when there is no airspeed and the gear is selected UP, the warning horn sounds and the light in the bypass switch comes on. Quote
PT20J Posted October 5, 2021 Report Posted October 5, 2021 22 minutes ago, RangerM20 said: It has the airspeed safety switch. My understanding is that when there is no airspeed and the gear is selected UP, the warning horn sounds and the light in the bypass switch comes on. That is correct. Quote
carusoam Posted October 5, 2021 Report Posted October 5, 2021 Summary… All Mooneys have two alert systems… 1) Stall warning… initiated by the single stall vane… 2) Gear up while attempting to land… initiated by two inputs… Throttle position, and one of the following (airspeed or squat switch) In the more recent Mooneys with airspeed switches… there is a safety By-pass button… to skip the airspeed switch… if you push this button… the system thinks it is now flying… no warnings are going to be sounded… Very often, a mechanic wants to test the whole system including the airspeed switch… do NOT blow air in the pitot tube… use the rolled rubber hose method to apply pressure gently into the pitot… blowing air into the pitot system is a known way to damage expensive instruments… PP thoughts only, not a mechanic… Best regards, -a- Quote
RangerM20 Posted October 5, 2021 Author Report Posted October 5, 2021 Right, and when the airplane is on jacks and I select the switch to UP, with no airspeed indication, nothing happens. When I push the button in, the gear then comes up with the horn on. Quote
carusoam Posted October 5, 2021 Report Posted October 5, 2021 Time to use the rolled rubber tube method… to satisfy the AS switch… Check the date of manufacture for the M20J… If it says made sometime in the 70s… expect this is before the digital evolution… The primary systems should work perfectly… But the maintenance system may be a bit funky compared to what a younger mechanic is expecting… Expect the safety by-pass button to allow the gear to go up… It would be nice if it did so quietly… If it is supposed to do so quietly… expect a wiring issue between the by-pass and the airspeed switch… In the end…. No airspeed = expect AS warning, by-pass or not…, with the gear switch in the up position… The plane is trying to save itself from the next il-advised move… PP thoughts only, not a mechanic… Best regards, -a- Quote
PT20J Posted October 5, 2021 Report Posted October 5, 2021 12 minutes ago, RangerM20 said: Right, and when the airplane is on jacks and I select the switch to UP, with no airspeed indication, nothing happens. When I push the button in, the gear then comes up with the horn on. I would get out the schematic for your serial number and trace out the circuitry to see what failure could cause this. There are a bunch of switches and relays in the gear circuitry. 1 Quote
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