Elect Gear Airspeed Safety Switch

[Mark942]

I have a 64 M20E with electric gear that was added a few years after it came out of the factory.  Does anyone have a photo of the Airspeed Safety Switch and some ideas as to where it might be mounted.  I am pretty sure I have located it, but would like confirmation.

Thanks,

-mark

[Ragsf15e]

Big brass thing right behind your airspeed indicator.  Pitot lines attached.

[carusoam]

12 minutes ago, Ragsf15e said:

Big brass colored, anodized aluminum Looking thing right behind your airspeed indicator.  Pitot lines attached.

Rags,

Sorry for putting words in your post... 

 

I’m only guessing, but,   If it were actually brass... it would be dark an ugly with oxidation... and weigh a lot...

 

There are a few pics around... and part numbers too...

https://mooneyspace.com/search/?q=Airspeed switch picture&updated_after=any&sortby=relevancy&search_and_or=and

Go MS!

Best regards,

-a-

[Ragsf15e]

10 hours ago, carusoam said:

Rags,

Sorry for putting words in your post... 

 

I’m only guessing, but,   If it were actually brass... it would be dark an ugly with oxidation... and weigh a lot...

 

There are a few pics around... and part numbers too...

https://mooneyspace.com/search/?q=Airspeed switch picture&updated_after=any&sortby=relevancy&search_and_or=and

Go MS!

Best regards,

-a-

Thanks!  It does look brass colored, but much better to be precise in your words!

[Mark942]

Thanks guys.  The thread to a photo does the trick.  I am looking at the right thing. Next annual, I'm going to attach a jumper wire across it so that my A/P doesn't have to blow through a rubber hose into my pitot tube to get the gear to cycle while on jacks. It makes me nervous watching the airspeed jump from 40 to 200 as he tries to maintain a steady pressure on the switch.  I think this could damage the airspeed diaphragm if not careful.

Thanks so much,

-mark

[carusoam]

Mark,

Some people have added the gear by-pass switch to the gear system...

People that have a temperature sensitive squat switch system...  where the donut dimensions and physical qualities change with temperature...

Something to consider as well...

Best regards,

-a-

[EricJ]

3 hours ago, Mark942 said:

Thanks guys.  The thread to a photo does the trick.  I am looking at the right thing. Next annual, I'm going to attach a jumper wire across it so that my A/P doesn't have to blow through a rubber hose into my pitot tube to get the gear to cycle while on jacks. It makes me nervous watching the airspeed jump from 40 to 200 as he tries to maintain a steady pressure on the switch.  I think this could damage the airspeed diaphragm if not careful.

Thanks so much,

-mark

The other air instruments can be damaged, too, if one is not careful.   As mentioned, the safety bypass switch can be added.   My airplane had the airspeed switch and bypass switch added not long after it left the factory, maybe as a warranty item or a concession or something.  

[KSMooniac]

You can also inflate a common party balloon and put it on the pitot tube. It will hold an airspeed, believe it or not.

Sent from my LG-US996 using Tapatalk

[cliffy]

Rather than blow into the pitot tube, take a rubber hose that slips snugly on to the pitot tube and clamp the outer end with vicegrip pliers and then just carefully and SLOWLY roll it toward the tube. Magically the airspeed comes alive and is controllable without over speeding the indicator. 

Also make sure your airspeed indicator goes all the way back to "0" airspeed. Its broken if it doesn't. You might think that this is a silly check but I've seen it happen and the owners never think twice about flying the airplane in this condition. DON"T DO IT!

[Yetti]

On 11/24/2019 at 11:26 AM, Mark942 said:

Thanks guys.  The thread to a photo does the trick.  I am looking at the right thing. Next annual, I'm going to attach a jumper wire across it so that my A/P doesn't have to blow through a rubber hose into my pitot tube to get the gear to cycle while on jacks. It makes me nervous watching the airspeed jump from 40 to 200 as he tries to maintain a steady pressure on the switch.  I think this could damage the airspeed diaphragm if not careful.

Thanks so much,

-mark

Nope not how you do it, unless you want to be replacing a bunch of instruments.   Roll up surgical tubing.

[EricJ]

On 11/24/2019 at 10:26 AM, Mark942 said:

Thanks guys.  The thread to a photo does the trick.  I am looking at the right thing. Next annual, I'm going to attach a jumper wire across it so that my A/P doesn't have to blow through a rubber hose into my pitot tube to get the gear to cycle while on jacks. It makes me nervous watching the airspeed jump from 40 to 200 as he tries to maintain a steady pressure on the switch.  I think this could damage the airspeed diaphragm if not careful.

Thanks so much,

-mark

There's a Service Bulletin to add a Safety Bypass switch, SBM20-196a.    Since you already have the airspeed switch, this would bring your circuit up to essentially what's in a J model.   In addition to the SB you could reference a J model circuit diagram to see the full circuit.