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Squat Switch Ideas

dbuds2

dbuds2

Well Known Member
I've been studying the new SkyView transponder installation and see the option for a Squat Switch. Has anyone used a Squat Switch to turn the TPX from ground to airborne operation?

I was thinking some kind of switch on the tail wheel. When on the ground and flexed up it would be open circuit and close as soon as off the ground and unloaded.
 
Interesting idea.

Give Dynon a call. They have some very smart people there who might take up that challange.
 
N395V said:
look here

http://www.aircraftspruce.com/catalog/elpages/uniswitchbattery.php
Click to expand...

Should work, but it seems silly to have to add another piece of hardware when the EFIS already has more than enough information to generate this output. You could generate a virtual squat switch to turn on the transponder on takeoff based on airspeed (as that device does), GPS speed, vertical speed, or engine RPM, any of which the EFIS already has. I don't know anything specifically about the Dynon, but talk to them. If they don't do this already (they probably do), I would think they could easily whip it up for you if there's a free I/O pin.
 
Nice suggestion Milt, but

According to the Dynon documentation: "This must be a mechanical switch that accurately reflects the aircraft?s on‐ground status. Mode‐S certification requirements state that this cannot be a simple airspeed switch."

I posted this question on the Dynon support forum too.
 
Squat Switch Required?

dbuds2 said:
According to the Dynon documentation: "This must be a mechanical switch that accurately reflects the aircraft?s on‐ground status. Mode‐S certification requirements state that this cannot be a simple airspeed switch."

I posted this question on the Dynon support forum too.
Click to expand...

Well, it seems that the folks at Garmin have figured out how to do this legally without a squat switch. My GTX330 switches from standby to Mode S automatically when I take off, and back to standby when I land. I don't recall the specifics, but I think it uses GPS ground speed to do this.

Skylor
 
Would an airspeed switch wired in series with a mercury tilt switch work for you? The airspeed switch would ensure it was deactivated above a certain airspeed, while the tilt switch would require a nose-high attitude in conjunction with no-airspeed to close the circuit...
 
mode S or C?

skylor said:
Well, it seems that the folks at Garmin have figured out how to do this legally without a squat switch. My GTX330 switches from standby to Mode S automatically when I take off, and back to standby when I land. I don't recall the specifics, but I think it uses GPS ground speed to do this.

Skylor
Click to expand...

I've seen these on G1000 systems, but they had mode C-encoders.
 
KRviator said:
Would an airspeed switch wired in series with a mercury tilt switch work for you? The airspeed switch would ensure it was deactivated above a certain airspeed, while the tilt switch would require a nose-high attitude in conjunction with no-airspeed to close the circuit...
Click to expand...

What about S&L unaccellerated flight? Mercury goes center... Mode-S turns off
 
dbuds2 said:
I've been studying the new SkyView transponder installation and see the option for a Squat Switch. Has anyone used a Squat Switch to turn the TPX from ground to airborne operation?

I was thinking some kind of switch on the tail wheel. When on the ground and flexed up it would be open circuit and close as soon as off the ground and unloaded.
Click to expand...

Check the Tx mfg's installation documentation. I suspect since the Mode-S needs a NEMA (GPS) input for position data... it may have an internal "I have groundspeed" enable/disable capability. If I built one, I'd put it in there.
 
BruceMe said:
What about S&L unaccellerated flight? Mercury goes center... Mode-S turns off
Click to expand...
Hence the airspeed switch. For Mode S to be deactivated, would require Airspeed <40KIAS (or whatever you set it at) and a nose high attitude. The only other time I can think of that occuring would be during a hammerhead.
 
dbuds2 said:
I was thinking some kind of switch on the tail wheel. When on the ground and flexed up it would be open circuit and close as soon as off the ground and unloaded.
Click to expand...

On any sort of rough ground, during landing or take-off, there's probably enough bouncing at the tailwheel to open and close the switch a few times. It would, at minimum, need a dampening or delay circuit or some sort to allow for that.
 
This may not affect MOST of us but...

How about the traffic anti collision that ground uses during low visibility that works with the transponders while on the ground. Probably a system for MAJOR airports. I can't think of the name of this system right now. You won't be able to participate without an active transponder on the ground.

correct me if I'm wrong....Just my thoughts...
 
My GTX 327 goes from standby on the ground to Mode C automatically on take off. It uses increase in altitude to trigger the switch.

Jim Sharkey
RV-6
 
KRviator said:
Would an airspeed switch wired in series with a mercury tilt switch work for you? The airspeed switch would ensure it was deactivated above a certain airspeed, while the tilt switch would require a nose-high attitude in conjunction with no-airspeed to close the circuit...
Click to expand...

So your transponder would turn off every time you did a hammerhead turn? ;)
 
If I was doing a hammerhead turn in my -9A I've got bigger problems than worrying about what my transponder is doing. ;)

But, yes, using an airspeed & tilt switch in series probably would put the transponder to standby during such a manevoure.
 
Manny said:
This may not affect MOST of us but...

How about the traffic anti collision that ground uses during low visibility that works with the transponders while on the ground. Probably a system for MAJOR airports. I can't think of the name of this system right now. You won't be able to participate without an active transponder on the ground.

correct me if I'm wrong....Just my thoughts...
Click to expand...


Most major airports require the transponder to be on from pushback. I suspect however that very few RV's will operate out of airports with ground radar. The system is very expensive and is not likely to be in place at any airports other then the largest. A simple call to ground to tell them the transponder will not be on for taxi would be fine at those airports as long as the vis was not below a 1/2 mile or so. Again this would be rare I hope for a RV.

George
 
Ground Mode

sailvi767 said:
Most major airports require the transponder to be on from pushback. I suspect however that very few RV's will operate out of airports with ground radar. The system is very expensive and is not likely to be in place at any airports other then the largest. A simple call to ground to tell them the transponder will not be on for taxi would be fine at those airports as long as the vis was not below a 1/2 mile or so. Again this would be rare I hope for a RV.

George
Click to expand...

Dynon's Skyview Mode S Transponder allready has a "Ground" Mode.:D
 
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Strain gauge

We have heard of simple strain gauges on undercarriage to successfully and reliably indicate airborne status for tracking systems - does not seem to be a reason why this would not be equally useful for txpnder.
 
Okay, perhaps I'm just a little slow, but can someone explain to me why so much discussion about a squat switch for a transponder? It seems so simple to me... turn it on just prior to takeoff. Turn it to standby after landing. My old KT-76A works pretty well that way.

What am I missing?
 
Since I rent a variety of planes, I manually control the Garmin (mode-C's) that try to do it automatically.

Anyway...there are some very simple (and tiny) IR and Ultrasonic distance measuring devices used in robotics and such. I wonder what they detect in a cloud? If either they were usable enough in IMC to avoid false detection, they could be a very simple solution to detect the ground without any moving parts. (For example, I've been working with this little bugger on another project and its easy and accurate enough.)
 
About 25 years ago I built an ultrasonic ranging device for ground proximity detection for a proposed gear-up warning system. I tested it by mounting on the bumper of my car and pointing it up. I detected the bridges I drove under just fine, but also discovered there is a lot of ultrasonic frequencies in wind noise. Too many false alarms.
 
jbDC9 said:
Okay, perhaps I'm just a little slow, but can someone explain to me why so much discussion about a squat switch for a transponder? It seems so simple to me... turn it on just prior to takeoff. Turn it to standby after landing. My old KT-76A works pretty well that way.
What am I missing?
Click to expand...
Mode S uses ground radar at major airports. However, the mode S transponder has a "ground" position on the switch that does the same thing as the squat switch, (albeit manually).
 
All of the postings seem to imply that the squat switch is a required item.

The Trig TT21 TSO'd installation instructions do not say it is a required input -

http://www.trig-avionics.com/library/TT2x-00560-00-AI.pdf - page 29

They recommend manual switching with no squat switch -

When airborne, the transponder should always be set to ALT unless otherwise directed by Air Traffic Control. When you are taxiing on the ground, the transponder should be set to GND unless your installation includes a gear squat switch. Aircraft installations that include a gear squat switch will automatically select GND on landing.
 
Mel said:
Mode S uses ground radar at major airports. However, the mode S transponder has a "ground" position on the switch that does the same thing as the squat switch, (albeit manually).
Click to expand...

Ah, gotcha. I guess I'm just not into all this hi-tech stuff.
 
Transponders should be left on

I believe the new guidance is that transponders should be left "on", even when on the ground. That is the way I have my G327 set.

Ron
 
The issue is with mode SES transponders being used to satisfy the coming ADSB-out requirements. The new rules require the transponder to switch automatically to ground mode when on the ground, and vice versa.
 
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