Where is airspeed switch? False gear unsafe alarm (Kind of new)

[willerjim273]

 

 

I am getting an "unsafe landing gear" warning in flight. A little obnoxious when you key the mic and have that squealing. Gear on jacks goes up and down just fine. And occasionally it does not squeal in flight. 

I have read as many posts as possible. I am in the process of replacing the throttle micro switch and the 628PR even though they seem to be fine. Next will be all grounds and the  AS switch. After that, from what I have read here,  we are looking at the underbelly switches.  Up for annual this month, so I will wait on that. 

I read on this blog that surgical tubing was "rolled up" to create airspeed with plane on jacks. I would like to see if it will hold air. 

Can someone tell me where, on a 1980 231, that switch is located?

The problem is I am getting a fault in the throttle switch , airspeed switch, piezo circuits. I have read everything from resistors to snapping the breakers.

BTW, if it is a dirty breaker, what is a good cleaner. ?

 

Cheers!

.

 

 

 

[Warren]

The gear alarm goes off when the throttle is retarded past the throttle switch (usually set about 16-17" MP) and the gear is in motion (Gear Unsafe indicator is lighted).

When you say that the alarm goes off in flight.  Is this normal flight or when the gear is extended in the landing pattern?

1.  Check that when the gear is down it is fully down.  Check the over center torque on the main gear and the spring pressure on the front gear.  At least this will ensure that mechanically the gear is down and locked appropriately so that it is safe to fly and not risk a gear collapse.

2.  Check that the gear down sensor is adjusted correctly so that when fully down it turns off the light.  When flying, does the Gear Safe light flicker on and off when the gear is extended?  I would guess that this sensor is triggering the alarm and should be on when the alarm sounds.  You should be able to verify that this is functioning correctly as the Gear Unsafe light will be on when the alarm sounds.  You can also test by increasing throttle past the throttle switch temporarily to see if the alarm goes off when the Gear Unsafe is still lighted - this will confirm that the throttle switch is working correctly and you can note the MP that triggers the alarm.

 

The airspeed switch is only used as a safety to prevent gear going up on the ground - it is set to sense a minimum airspeed that enables the gear up process.  If the gear will not go up on jacks without the gear override button and the gear goes up in flight this switch is working.  You may want to check this eventually to confirm the airspeed that triggers the switch is correct but it is not causing the gear alarm.

[willerjim273]

Posted 11 minutes ago

 

Sorry if I double quote. We replaced the throttle switch and gear piezo. Ready to test fly today or t'morrow. 

The gear alarm goes off when the throttle is retarded past the throttle switch (usually set about 16-17" MP) and the gear is in motion (Gear Unsafe indicator is lighted).

When you say that the alarm goes off in flight.  Is this normal flight or when the gear is extended in the landing pattern? 

No, alarm sounds regardless of throttle position

1.  Check that when the gear is down it is fully down.  Check the over center torque on the main gear and the spring pressure on the front gear.  At least this will ensure that mechanically the gear is down and locked appropriately so that it is safe to fly and not risk a gear collapse. Sounds good. I get a gear down light just fine. 

2.  Check that the gear down sensor is adjusted correctly so that when fully down it turns off the light.  When flying, does the Gear Safe light flicker on and off when the gear is extended? No

 

I would guess that this sensor is triggering the alarm and should be on when the alarm sounds.  You should be able to verify that this is functioning correctly as the Gear Unsafe light will be on when the alarm sounds.  You can also test by increasing throttle past the throttle switch temporarily to see if the alarm goes off when the Gear Unsafe is still lighted - this will confirm that the throttle switch is working correctly and you can note the MP that triggers the alarm. I tried increasing throttle. No joy

This is a 231. No squat switch, as far as I know.  It has the airspeed switch and throttle switch. 
I have done that, no joy. 

The airspeed switch is only used as a safety to prevent gear going up on the ground - it is set to sense a minimum airspeed that enables the gear up process.  If the gear will not go up on jacks without the gear override button and the gear goes up in flight this switch is working.  You may want to check this eventually to confirm the airspeed that triggers the switch is correct but it is not causing the gear alarm. Yes on all that. So I am very happy to know it is not the switch. 

 

thanks for the reply!

[Warren]

 

Not sure if this helps, but here is the description of the gear safety system from the Maintenance Manual.  A 1980 Mooney should fall in the first category and have the throttle switch adjusted to 10" MP.

[willerjim273]

Update on unsafe gear warning horn. Success, I think. Thanks to this platform and after reading all I could, it may be solved. 

We replaced the throttle micro switch (which tested OK) and the piezo. We also set and rest the breakers. Took her for a 30 min flight and no problem. HOPEFULLY that will do it. I am set to fly to El Paso this week so I will let everyone know if it is solved long term. Which of the 3 it could be, I have no idea. Again, hats off to this resource. 

[PT20J]

It doesn't sound like your problem, but since you asked, the airspeed safety switch is located either on the back of the airspeed indicator or on a bracket behind the instrument panel up high behind the airspeed indicator.

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