What Does Airspeed Switch Look Like?

[MBDiagMan]

Yes, rags picture looks like mine.

[Guest]

1 hour ago, Ragsf15e said:

Got pictures of one in my ia shop today... this on a 76 F.

That attitude gyro won’t last long without a filter on the air inlet.

Clarence

[MBDiagMan]

It is in the shop so maybe the filter is not connected due to the stage of repair.

[Ragsf15e]

Thankfully it’s not mine.  That poor airplane is a bit rough.  Came in running rough too.  Took some work, but finally they turned over the engine while watching the valves with a borescope. The exhaust valves barely open.  Cam is worn way down.  Shot.  But hey, now it’s all opened up and I can get pictures of all kinds of parts.  No 201 windshield, so great access to the avionics too!  I’m almost jealous!  

[Ragsf15e]

3 hours ago, larryb said:

My plane is in the shop right now for this. Last year at annual they replaced the airspeed safety switch. Ever since it has been off on its calibration. Sometimes it works fine. But most of the time I have to press the override button because the switch does not activate at the calibrated airspeed. The shop tried to adjust it once but it is just flaky. This time it is a warranty issue.

I guess I want mine to work just right too, but better it fails to allow retraction than always allowing it.  You have the bypass so you can still get the gear up.  I don’t, but my asss seems to work pretty good   .  I wouldn’t want to get in the habit of using the bypass every time.  

Whole point of asss or squat switches is to prevent gear retraction on the ground, it is weird that they kept switching back and forth between methods.

[MBDiagMan]

Okay, I got some Tygon tubing and connected to the pitot tube.  I closed the hangar door, closed the aircraft door and pressured the tube several times up to as much as about 140 MPH and could never HEAR the switch click.   

So... my next thing is checking it electrically.  I can’t reach the switch very easily.  In fact it is very difficult to access.  I have the wiring schematic and I am wondering where the up relay is located.  I can check the switch more easily at the relay if it is easily accessible.

I am learning thanks to all you guys.

[MBDiagMan]

Okay I FINALLY got it on jacks and flipping the gear switch results in no change.  No noise, no gear movement and green light remains on.  I pressured the pitot use to about 120 and still nothing.  I had to leave before I got any further.  Tomorrow I will pull the seat so I can get to the switch.  I plan on shorting the switch and see if it works.  Assuming this proves the switch faulty, where can I get a switch or parts to repair it?

Thanks

[carusoam]

MBD,

Are you looking for a new airspeed switch?

Or a new Landing gear switch?

Sounds like Either one could be hassling you.

Expect removal and cleaning to be the order of the day.

Should be pretty easy to bench test, and very expensive to replace...

Best regards,

-a-

[MBDiagMan]

Thanks carusoam.  I was asking the question last night to try to get ahead of it.  I am headed to the airport this morning with no idea what I will get into. I may very well discover a loose wire in the circuit or who knows what.  In case it does need parts I was trying to get an idea about sourcing.

Thanks

[Guest]

The relays are under the floor beside the gear actuator.  Accessible by removing  the belly panels.

Clarence

[MBDiagMan]

Thanks for all the replies.  Paul Maxwell came over Saturday and found the problem.  The problem was at the Up limit switch.  All is now good.  Maxwell Aviation rocks!

[carusoam]

Two thumbs up for the follow-up and details!

Go PMax!

Best regards,

-a-

[ArtVandelay]

I have the brass switch, I also have this rather large rectangular box, with adjustments and D connector...anyone know what this is? :

[Guest]

14 minutes ago, ArtVandelay said:

I have the brass switch, I also have this rather large rectangular box, with adjustments and D connector...anyone know what this is? :

Looks like a Narco altitude encoder.

Clarence

[ArtVandelay]

Looks like a Narco altitude encoder.

Clarence

Thanks, I didn’t think I needed one, I thought my KT74 did that. I’ll try to see if the wires are still connected to anything.

Edit:

After further investigation it has:

Built-in altitude repeater instead of a second altitude encoder

 

Not sure who is using the first altitude encoder?

[xcrmckenna]

Does anyone have the part number and the company that makes the airspeed switch? I replaced mine a few years ago but can’t get to the logbooks. Thanks

[Raymond J1]

2 hours ago, xcrmckenna said:

Quelqu'un a-t-il le numéro de pièce et la société qui fabrique le commutateur de vitesse? J'ai remplacé le mien il y a quelques années mais je n'arrive pas à accéder aux journaux de bord. Merci

[DCarlton]

I purchased a new one years ago from VEP Pressure Switches (Value Engineered Products).  I still have the brochure in the files if anyone needs it.  Works great. 

[FastTex]

4 hours ago, DCarlton said:

I purchased a new one years ago from VEP Pressure Switches (Value Engineered Products).  I still have the brochure in the files if anyone needs it.  Works great. 

Hello @DCarlton, would you mind sharing it? Mine was cleaned up a few years ago but I was told the membrane was at its last leg.

[carusoam]

8 hours ago, FastTex said:

Hello @DCarlton, would you mind sharing it? Mine was cleaned up a few years ago but I was told the membrane was at its last leg.

Often, these switches get OH’d… Something to consider…

Best regards,

-a-

[xcrmckenna]

17 hours ago, Raymond J said:

Awesome, thank you!

[Raymond J1]

pressostat.pdf

https://www.worldmagnetics.com/userfiles/filemanager/dhxcu7xkqkp3ac9l8rnj

[xcrmckenna]

15 hours ago, DCarlton said:

I purchased a new one years ago from VEP Pressure Switches (Value Engineered Products).  I still have the brochure in the files if anyone needs it.  Works great. 

@irishpilot