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Air Speed Switch

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dsvs(at)comcast.net
Guest

Posted: Fri Apr 07, 2006 10:30 am Post subject: Air Speed Switch

Bob and Others

I need to purchase an airspeed switch that is closed when stationary and opens at roughly 15 knots.  An adjustable unit is fine as long as the adjustment point can be set for fairly low (15-20 knot) range.  Any idea of a vendor for this device.  ACS has only one and the adjustment point is above 80 knots.  Thanks in advance.  Don

nuckollsr(at)cox.net
Guest

Posted: Sat Apr 08, 2006 3:05 pm Post subject: Air Speed Switch

At 06:25 PM 4/7/2006 +0000, you wrote:



 	  Quote: 	
		  



Bob and Others

I need to purchase an airspeed switch that is closed when stationary and 

opens at roughly 15 knots.  An adjustable unit is fine as long as the 

adjustment point can be set for fairly low (15-20 knot) range.  Any idea 

of a vendor for this device.  ACS has only one and the adjustment point is 

above 80 knots.  Thanks in advance.  Don


	


   Recall that dynamic pressure (pitot pressure, or "q") varies

   as the square of velocity. At 200 mph you get 20" of water

   pressure. So for 1/10th that velocity or 20 MPH, you get

   1/100th the pressure or 0.2" of H20. 20Kts would be 23

   MPH so .2" is right in the ballpark.



   That is an exceedingly small pressure to sense. I doubt

   that anyone has a switch that will operate directly

   from that kind of pressure.



   What are you wanting to do with it? Parhaps there's

   a more rugged and less expensive way to get at the

   functionality.



   Bob . . .



      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

dsvs(at)comcast.net
Guest

Posted: Sat Apr 08, 2006 6:43 pm Post subject: Air Speed Switch

Bob,

The switch is recomended by Avidyne for use with their TCAS systems.  It is

to take the device out of ground mode and into airborne mode.  I used to fly

a piper twin that had the same type of switch to start the "air hobbs"

meter.  BTW Avidyne does not have a source, that is why I am hoping that you

had one.  Thanks.  Don



--

frank.hinde(at)hp.com
Guest

Posted: Sat Apr 08, 2006 6:46 pm Post subject: Air Speed Switch

There are definatly industrial switches that will reliably switch on

0.2" WC...Trouble is the diaphram will be about 4 inches in diameter.

Definatly not a lightweight compact component!...



Frank 



--

nuckollsr(at)cox.net
Guest

Posted: Sat Apr 08, 2006 7:30 pm Post subject: Air Speed Switch

At 07:37 PM 4/8/2006 -0700, you wrote:



 	  Quote: 	
		  



Bob,

The switch is recomended by Avidyne for use with their TCAS systems.  It is

to take the device out of ground mode and into airborne mode.  I used to fly

a piper twin that had the same type of switch to start the "air hobbs"

meter.  BTW Avidyne does not have a source, that is why I am hoping that you

had one.  Thanks.  Don


	


   Hmmmm . . . Frank knows of some devices with that sensitivity.

   As one might expect, it's pretty big. How about an RPM switch

   set at something like 1500 rpm. You could even put a timer

   in the loop so that the air mode happens after say 30 seconds

   above 1500. This would let you do mag-chex, etc without triggering

   the air mode. Signal would come from the tach output on an ignition

   or p-lead on mag.



   Have you called Avidyne?



   Bob . . .

dsvs(at)comcast.net
Guest

Posted: Sat Apr 08, 2006 7:50 pm Post subject: Air Speed Switch

Called Avidyne, they say buy from Cirrus.  Cirrus has one but will not sell

it to home builders.  Still looking for a Cirrus repair facility that will

sell one. I,m running P-mags so I have two seperate tach hall effect sensors

built in.  Was planning on using both to run seperate tach outputs, just

because I have two instruments that will show RPM.  Where do I get an RPM

switch?  Thanks.  Don



--

richard(at)RILEY.NET
Guest

Posted: Sat Apr 08, 2006 8:45 pm Post subject: Air Speed Switch

At 07:37 PM 4/8/2006, you wrote:

 	  Quote: 	
		  



Bob,

The switch is recomended by Avidyne for use with their TCAS systems.  It is

to take the device out of ground mode and into airborne mode.  I used to fly

a piper twin that had the same type of switch to start the "air hobbs"

meter.  BTW Avidyne does not have a source, that is why I am hoping that you

had one.  Thanks.  Don


	


Velocity has one, it's pretty inexpensive but works fine.  I think 

it's an industrial part adapted from a clothes dryer.



There's a nice (much more expensive) one available from:

Airspeed Switch

Value Engineered Products

3541 Old Conejo Road, Ste #117

Newbury Park, CA 91320

(805) 499-1959

(805) 499-1955

email: vep1(at)pacbell.net

www.veproducts.com

Part #654A53.2

Jim Baker

Joined: 30 Mar 2006
Posts: 181
Location: Sayre, PA

Posted: Sat Apr 08, 2006 8:51 pm Post subject: Air Speed Switch

 	  Quote: 	
		   The switch is recomended by Avidyne for use with their TCAS 

systems. 
	


 	  Quote: 	
		   It is to take the device out of ground mode and into airborne mode.  


	


Sure beats me whay they didn't just use a GPS signal to run the 

system...sorta like the setting for a KLN series GPS that only starts 

timing above 30kts....say, use a $GPRMC string, and parse out the 

speed with a PIC and some code (or a BASIC stamp) and use 

that to drive a relay.

Jim Baker

580.788.2779

Elmore City, OK

BigD(at)DaveMorris.com
Guest

Posted: Sat Apr 08, 2006 10:16 pm Post subject: Air Speed Switch

Why don't you just buy a cheap microswitch and keep sticking larger 

and larger surface area on it until it triggers at the desired speed 

while it's being hung out the window of your car?



Dave Morris



At 09:45 PM 4/8/2006, you wrote:

[quote]

(Corvallis)" <frank.hinde(at)hp.com>



There are definatly industrial switches that will reliably switch on

0.2" WC...Trouble is the diaphram will be about 4 inches in diameter.

Definatly not a lightweight compact component!...



Frank



--

ivor(at)ivorphillips.flye
Guest

Posted: Sun Apr 09, 2006 1:36 am Post subject: Air Speed Switch

Try   http://rswww.com/cgi-bin/bv/rswww/subRangeAction.do?cacheID=ukie



 It works well  as a stall warner, If you reverse the Inlet pipe it will 

work as a pressure switch, And its ajustable!



Ivor phillips

ivor(at)ivorphillips.flye
Guest

Posted: Sun Apr 09, 2006 3:02 am Post subject: Air Speed Switch

http://rswww.com/cgi-bin/bv/initSession.jsp?goto=/rswww/subRangeAction.do&catoid=-1600769365&store=uk

 	  Quote: 	
		  

 It works well  as a stall warner, If you reverse the Inlet pipe it will

 work as a pressure switch, And its ajustable!

 The previous link didnt seem to work, But this one should!
	


Ivor Phillips

glastar(at)gmx.net
Guest

Posted: Sun Apr 09, 2006 3:29 am Post subject: Air Speed Switch

DonVS wrote:



[quote]



Bob,

The switch is recomended by Avidyne for use with their TCAS systems.  It is

to take the device out of ground mode and into airborne mode.  I used to fly

a piper twin that had the same type of switch to start the "air hobbs"

meter.  BTW Avidyne does not have a source, that is why I am hoping that you

had one.  Thanks.  Don



--

klehman(at)albedo.net
Guest

Posted: Sun Apr 09, 2006 4:46 am Post subject: Air Speed Switch

Wouldn't a switch on the landing gear be easier and more reliable?

Ken



Dave Morris \"BigD\" wrote:



 	  Quote: 	
		  



Why don't you just buy a cheap microswitch and keep sticking larger 

and larger surface area on it until it triggers at the desired speed 

while it's being hung out the window of your car?

richard(at)RILEY.NET
Guest

Posted: Sun Apr 09, 2006 7:05 am Post subject: Air Speed Switch

At 05:38 AM 4/9/2006, you wrote:

 	  Quote: 	
		  



Wouldn't a switch on the landing gear be easier and more reliable?

Ken


	


Depending on the geometry of the landing gear it may not be possible, 

unless you're talking about dragging a feeler on the ground.  And in 

that case, no, I think an airspeed switch would be simpler and more reliable.

BobsV35B(at)aol.com
Guest

Posted: Sun Apr 09, 2006 8:46 am Post subject: Air Speed Switch

In a message dated 4/9/2006 1:18:29 A.M. Central Standard Time,  

BigD(at)DaveMorris.com writes:



Why  don't you just buy a cheap micro switch and keep sticking larger 

and  larger surface area on it until it triggers at the desired speed 

while  it's being hung out the window of your car?



Dave  Morris



Good Morning Dave,

 

That should work, but if you are going to rely on a plate that is out in  the 

breeze, it will add drag to the aircraft.  If you place a switch in the  

pitot system that reacts to the pressure, there will be no additional drag added  

to the flying machine.

 

Do Not Archive

 

Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503

Bill Denton

Joined: 10 Jan 2006
Posts: 97
Location: Chicago, IL USA

Posted: Sun Apr 09, 2006 9:42 am Post subject: Re: Air Speed Switch

You might take a look at this one:



http://www.alliedelec.com/Search/ProductDetail.asp?SKU=634-0005&SEARCH=6753%2DAEJA%2DA000&ID=&MPN=6753%2DAEJA%2DA000&DESC=6753%2DAEJA%2DA000



I believe this is the one that Microair uses with their transponders to switch them out of standby when the aircraft reaches a specific speed.



Good luck!

psychden(at)sonic.net
Guest

Posted: Sun Apr 09, 2006 11:55 am Post subject: Air Speed Switch

Take a look at the World Magnetics line available thru Digikey at www.designflexswitches.com . There's a new Goldtech line that looks promising for the application. This also looks favorable for a pitot based "squat" switch or a gear warning sensor based on airspeed. The previously available switches  were either normally open (PSF102), weren't sensitive below 2" H20 (PSF 103). This new switch appears to be able to handle switching loads for the landing gear solenoid in the application where you would prevent gear retraction for airspeeds below 70 knots (3.159" H20) with the switch in series. I've been waiting for something like this! What do you gurus think?  Larry Ford Glasair I RG N149LF

jan.de.jong(at)xs4all.nl
Guest

Posted: Sun Apr 09, 2006 12:35 pm Post subject: Air Speed Switch

World Magnetics would seem to make a useful switch?

See http://dkc3.digikey.com/PDF/T061/1703.pdf

Cheers,

Jan de Jong

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Sun Apr 09, 2006 12:39 pm Post subject: Air Speed Switch

Larry Ford wrote:

 	  Quote: 	
		   

 

 This also looks favorable for a pitot based "squat" switch or a gear warning sensor based on airspeed.

 > ...
	


 	  Quote: 	
		   What do you gurus think?  Larry Ford Glasair I RG N149LF


	


I think that I have been annoyed with every kind of landing gear warning 

system I have ever used. Piper had their automatic system that put the 

gear down when you slowed down and that just about drove everyone nuts. 

The only system I have really liked is to do my GUMP check twice: once 

on downwind to get all the stuff done and again on final to make sure I 

didn't forget anything. If on instruments putting the gear down at the 

FAF usually sets my descent rate to the runway.



I know, it's not high tech. OTOH it is KISS.



-- 

Brian Lloyd                         361 Catterline Way

brian-yak at lloyd dot com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

- Antoine de Saint-Exupery

_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery

lhelming(at)sigecom.net
Guest

Posted: Mon Apr 10, 2006 3:45 am Post subject: Air Speed Switch

Operating temperature range is a problem unless you have a stable 

environment to put it in.    Larry in Indiana



---

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