Today's Message Index:
----------------------
1. 05:04 AM - Re: Re: Checking out a radio installation (LarryRobertHelming)
2. 05:50 AM - Headphones "auto-loading" circuit (Robert L. Nuckolls, III)
3. 07:06 AM - Re: Why use starter contactor? (Gary Casey)
4. 08:49 AM - Re: Re: Why use starter contactor? (Robert L. Nuckolls, III)
5. 09:53 AM - Re: Why use starter contactor? (sky is falling) ()
6. 11:29 AM - Re: Why use starter contactor? (good points Bob) ()
7. 04:05 PM - Re: Air Speed Switch (Robert L. Nuckolls, III)
8. 07:43 PM - Re: Air Speed Switch (DonVS)
9. 07:46 PM - Re: Air Speed Switch (Hinde, Frank George (Corvallis))
10. 08:30 PM - Re: Air Speed Switch (Robert L. Nuckolls, III)
11. 08:50 PM - Re: Air Speed Switch (DonVS)
12. 09:45 PM - Re: Air Speed Switch (Richard Riley)
13. 09:51 PM - Re: Air Speed Switch (Jim Baker)
14. 11:16 PM - Re: Air Speed Switch (Dave Morris \)
Message 1
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| Subject: | Re: Checking out a radio installation |
--> AeroElectric-List message posted by: "LarryRobertHelming" <lhelming@sigecom.net>
----- Original Message ----- >
> I am at the stage where I want to make sure my radios and nav work before
> I
> put on the panel that makes getting at all my wiring and radio stack very
> difficult. In other words, I am at my garage and not near an airport.
There are planes flying over head -- right? You can listen in. You
should not transmit on a frequency where commercial traffic might hear and
possibly cause someone a problem. Usually there will be chatter going on
the CTAF 122.8. From the ground, anyone that would hear you would have to
be pretty much above you within a 10 mile radius but that could be more or
less depending if you are sitting in a valley or on a hill top.
>
> I want to order a hand held nav/com to test my Garmin SL 30. Is there a
> set
> procedure for this kind of thing. Can I just transmit on some obscure
> frequency and try and receive on the other?
That is how I first tested my 430 with a hand held radio, while
sitting on the ground. I did discover a wiring problem with my PTT. Glad I
figured it our before getting everything together.
I tested the NAV during flight testing Phase I.
>
Indiana Larry, RV7
>
>
>
Message 2
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| Subject: | Headphones "auto-loading" circuit |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
>
>Comments/Questions: I'm installing a PS1000II intercom in a 172M, picking
>up the phone hi line at the ship's auxiliary phone jack. This jack grounds
>the hi side through a 560 ohm resistor if a phone is not plugged in.
>What's the purpose of this resistor, and do I need to keep this peculiar
>jack for the pilot's phone jack?
>
>Thanks.
I can only guess. The the designer of the system probably
believes its a bad thing to leave the output of the
amplifier unloaded. He may have some experience that suggests
constant loading is a good thing . . . or he may have heard
a rumor about it and decided that the CYA approach to design
was more comfortable.
I suspect that the auto-loading feature is not necessary.
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 >
Message 3
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| Subject: | Re: Why use starter contactor? |
--> AeroElectric-List message posted by: Gary Casey <glcasey@adelphia.net>
Just another data point in this discussion: Many years ago (make
that many, many years...), when I was at GM and working with Delco-
Remy The subject of stuck solenoids was known. The system was
designed so that all the components were sized appropriately and the
battery would run down before any of the other devices, like the
starter or wire would fail. The idea was that the starter would
stick so the driver would turn the key off and it would revert to
cranking a dead engine. If it stuck and the driver didn't know
enough to shut the engine off then the starter would likely fail
along with the overrunning clutch. Not pleasant. On my
experiemental I used a "big fat" starter push-button switch wired
directly to the solenoid on the B+C series-wound starter solenoid.
the starter is powered through the master contactor. I admit it was
tempting to run the starter hot from the battery, but I finally
backed off from that concept. I would guess that if the starter
stuck on and the engine was shut off the battery would run down
before anything bad would happen. If it sticks with the engine
running I guess the only detection would be by looking at the battery
voltage (no ammeter installed). The good thing is that this type of
failure occurs on the ground; the bad thing is that this stuff is
very expensive.
And then for redundancy I simply wired two "master" relays off the
battery - one "master" to power the big stuff, including the starter,
and one "avionics" relay to power the radios. I probably should have
wired one of the radios off the master.
Gary Casey
ps: I just fired the engine for the first time and the performance
of the B+C starter was very impressive. I do have a firewall-mounted
battery, but with an IO-540 with 10:1 compression and a composite
prop, the starter spun the engine with AUTHORITY and there was not
even a hint of cogging over TDC. The starter was also very quiet,
implying that the drive gear is well-designed and all the alignments
were very well done. I was impressed.
Message 4
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| Subject: | Re: Why use starter contactor? |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 06:59 AM 4/8/2006 -0700, you wrote:
>--> AeroElectric-List message posted by: Gary Casey <glcasey@adelphia.net>
>
>
>Just another data point in this discussion: Many years ago (make
>that many, many years...), when I was at GM and working with Delco-
>Remy The subject of stuck solenoids was known. The system was
>designed so that all the components were sized appropriately and the
>battery would run down before any of the other devices, like the
>starter or wire would fail.
Sizing of components to enhance predictability and therefore
push failures off toward more acceptable ends is one of
many tools in the system designer's toolbox. The exercise
you've cited is generally applied when rudimentary
techniques are not applicable. For example, there's no
fuse or circuit breaker that might be expected to bring
a runaway starter to heel. So the FMEA drives designers
to consider limiting the ability of a system fault to
bring the whole to ruin. Limiting battery size such that
sticking contactor events would come to graceful conclusion
was a valid approach.
In the aircraft world, we might utilize this approach with
better assurance of success because we have regulatory
control over the components used. Unlike cars in the pubic
domain, we have better assurances that an airplane won't
get fitted with a bigger battery and that airplane looses
benefits of the original designed in limits.
> The idea was that the starter would
>stick so the driver would turn the key off and it would revert to
>cranking a dead engine. If it stuck and the driver didn't know
>enough to shut the engine off then the starter would likely fail
>along with the overrunning clutch. Not pleasant.
Suppose we had the task of mitigating this event today?
For under $1 I can buy a microprocessor that can be
programmed to watch start signal from the panel, compare
with power applied to the starter, watch battery voltage
for potentially damaging attempts to start with a soggy
battery, and I might even filter the start signal through
the processor so that a dirty start switch and/or tentative
operation of the switch doesn't tease the starter contactor
into welding. If any undesired condition is detected,
I at least have an opportunity to annunciate it to the
operator and in some cases terminate the start attempt
-AND- annunciate the condition.
> On my
>experiemental I used a "big fat" starter push-button switch wired
>directly to the solenoid on the B+C series-wound starter solenoid.
>the starter is powered through the master contactor. I admit it was
>tempting to run the starter hot from the battery, but I finally
>backed off from that concept. I would guess that if the starter
>stuck on and the engine was shut off the battery would run down
>before anything bad would happen.
Had a Glassair stick an always hot starter wire and the brand
new RG battery was cranking merrily away long enough for
the builder to get out, remove the cowl and disconnect
the battery. The starter survived (although no doubt
short on future service life). The builder subsequently
moved his starter feed to the downstream side of the
battery master contactor.
> If it sticks with the engine
>running I guess the only detection would be by looking at the battery
>voltage (no ammeter installed). The good thing is that this type of
>failure occurs on the ground; the bad thing is that this stuff is
>very expensive.
I was at OSH one year when a story flashed around the field
about one of the airshow performers having landed and discovering
that his starter and ring gear were all chewed up. The off-hand
diagnosis was that high g-loading during his performance caused
a tentative closure and subsequent welding of his starter
contactor. I would have given $100 to get my hands on all the
parts and to see how they were installed.
I would guess that it's far more likely that the starter
stuck on initial cranking of the engine and the pilot
was mentally concentrating on the performance task before
him. He might have made good use of the $1 processor.
>And then for redundancy I simply wired two "master" relays off the
>battery - one "master" to power the big stuff, including the starter,
>and one "avionics" relay to power the radios. I probably should have
>wired one of the radios off the master.
. . . or supplied a normal-feed diode from main bus to
the avionics bus and you could now call it an e-bus.
>Gary Casey
>
>ps: I just fired the engine for the first time and the performance
>of the B+C starter was very impressive. I do have a firewall-mounted
>battery, but with an IO-540 with 10:1 compression and a composite
>prop, the starter spun the engine with AUTHORITY and there was not
>even a hint of cogging over TDC. The starter was also very quiet,
>implying that the drive gear is well-designed and all the alignments
>were very well done. I was impressed.
That starter was in development for years before it hit the market.
Early endurance issues were pretty much limited to high stress
points in the castings which were identified and fixed early on.
We were on a trip to CA to participate in Voyager support activities
at Mojave when Bill stopped by Robinson to meet their president
and discuss starter issues.
I believe to this day, the B&C starter still goes out on 100% of
Robinson products. Starters are pulled off of Robinson helicopters
when they come back for 2,000 hour overhaul. This is one of
VERY few instances where a manufacturer has an orchestrated
opportunity to track a product's field performance. Many returned
starters look like junk yard dogs having suffered the rigors
of various duties in the field. However, when opened up wear rates
indicate that the starters would easily run another 2,000
hours without further attention. Continental gave up trying
to 'kill' a B&C starter after 5,000+ starts on the test stand.
Odds of you being a satisfied user of this starter are very good
but I applaud your decision to run the starter downstream of
the battery master contactor.
Bob . . .
Message 5
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| Subject: | Re: Why use starter contactor? (sky is falling) |
--> AeroElectric-List message posted by: <gmcjetpilot@yahoo.com>
>From: "John D. Heath" <altoq@cebridge.net>
>Subject: Re: AeroElectric-List: Re: Why use starter contactor?
>-- TWIMC (Which is probaly only me),
>(1) Electrical Solenoid engaged starters, as used on Lycoming,
>Chevrolet,BMW, and Porsche, do stick.
Some people have real bad luck; My experience is the opposite and
the engineers told me the SkyTec will not sick (see their web site).
Any of your claimed occurrences happen with a SkyTec or B&C? No
>(2) Solenoid engaged starters are disengaged by a spring and an over
>running mechanism in the starter gear.
Yes A big fat spring and mechanical advantage plus back spin
.... assists in the retraction.
>(3) I have personally seen three out of the four named, stick .
You said that already, twice now. You left off all kinds of info.
Lycoming? Bendix style? SkyTec? B&C? More info please.
Lycomings usually had old Bendix style starters made by
Prestolite or Delco. Bendix does not equal SkyTec
>(4) They stick and continue to crank the engine, they stick and don't
>crank the engine, and all modes of stick in between.
Look you have an agenda, but you provided ZERO information. I
have been flying for 12,000 hours and have worked on cars for 30
years. Yes starters stall? So what? Can you tell me what that has to
do with anything. When I was flying Freight or giving flight instruction,
I was flying a fleet of over 30 planes in numbers. All the problems you
claim are hard to believe and sound sensational and emotional.
I NEVER, NEVER HAD A STARTER STICK. That does not mean
much, but lightweight car type starters on airplanes have only
been around less than 20 years. However in that 20 years the issue
of starter STICK is old news. I know it is hard to get people such as
yourself, whose mind is made up, to be convinced, but if you are
honest with yourself and look at the facts and service history of
modern starters, you will see your opinion of the past does not
represent the now or future. If it makes you happy, add extra stuff.
>(5) They stick when they are new or old, clean or dirty but mostly they
>stick because they are misaligned or have not been lubricated.
WE GET IT, THEY (what ever THEY are) Stick. I just ask you give
some examples with details. My guess they don't apply to a SkyTec
or B&C style starters.
>(6) One of these starters that fail in the "CRANK the engine mode" with
>the +12VDC wired directly to the solenoid has a great big wire as big
>around as your index finger HOT and you can't turn it off.
So what do the FEW MILLION cars and trucks do all over the world.
What is you point? Did you think of turning the ENGINE OFF?
I can see you are convinced that every car on the road is WRONG.
OK that is cool, but I think you are making a mountain out of a mole
hill. The Robinson R22 helicopter is wired w/o a FW relay.
>(7) There are many light weight relays capable of eliminating this
>problem by attaching the +12VDC first to it and then on to the starter
>solenoid. No device that controls the starter directly through its
>solenoid control circuit can do this.
WHAT! Dude I could not disagree more. Prove it :-) The reason for
those 3/4 Lb solenoids on airplanes is they had BENDIX starters with
no integrated solenoid or contactor (relay). First they did not need a
solenoid because they where SPUN out when the starter was spun.
They where the only kind found on most GA planes up to 20 years
ago. They are notorious for sticking. The Bendix starters NEEDED
a firewall relay/contactor; that is why we still have them today.
Big firewall solenoids are also problematic.
The reason for using the firewall solenoid like Bob calls out and
Vans aircraft calls for is standardization with old starters. BOB
and Van's aircraft do not control the type of starter the builder uses,
and so the OLD WAY works with everything, old and new. CLEARLY
you don't believe me, CALL SKY TEC starters. They will calm you
down and straighten you out. Things have changed.
It is OK, many people like the security blanket of the extra switch.
>(8) I have had multiple experiences with these type failures. Allow me
>to pass these experiences on to you and eliminate the time and
>aggravation it would take for you to accumulate them yourself. Use the
>information as you will.
OH MY GOSH, you have repeated yourself 5 times. You think THEY
stick. OK,
How about some specific info: Starter model, Aircraft and what the
problem was (starter, firewall solenoid). You don't give any more info
than you have seen a starter stick. A SkyTec? B&C? Doubt it.
Sorry I hear no facts and really doubt it applies to SkyTec.
No offense but I think you exaggerate a lot in your mind. However I
respect your fear of starters. I have researched this and you are
living in the old days of starters.
Your comments give no basis in facts. First a firewall solenoid is
another thing to fail. Second the solenoid and contactor on the starter
is very capable with out help. You are adding a device that can stick
on its own, more than the starter itself.
Also if a starter sticks on start, SHUT DOWN the engine. There is
no need to panic and make this a big deal. Does a black cloud follow
you and it rains on all you vacations? I mean your story of impending
disaster is really over stated when it comes to starters.
My opinion from experience is starters rarely stick and modern non
Bendix ones less then never. From taking engineers at the biggest
starter maker (SkyTec) and by their web site, QUOTE:
"Since Sky-Tec starters do not use mechanical Bendix drives to actuate
the starter, this is actually nearly impossible for a Sky-Tec starter to keep
itself engaged with the aircraft ring gear."
Also Robinson R44 helicopter is certified with NO firewall starter
Solenoid. (Good enough for the FAA)
>(9) (Even you did not want to keep it in the records)
Boy I guess you told me. Please reply with real information. I just
don't believe anything you said has to do with a SkyTec, B&C,
NOT: Prestolite; Electrosystems; Lamar; Delco.
Again Murphy's law but I think with your luck you better stay on the
Ground. Lol :-)
Cheers George.
---------------------------------
Message 6
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| Subject: | Re: Why use starter contactor? (good points Bob) |
--> AeroElectric-List message posted by: <gmcjetpilot@yahoo.com>
Bob:
Very good points about PM starters spin down and engagement. I
knew this and even SkyTec addresses this in their documentation.
You say 2 to 5 seconds?
>From http://www.skytecair.com/Troubleshooting.htm
Complaint: After start button is released, the starter stays engaged
for nearly a second before releasing?
Question: Does it stay engaged only for 1/2 to 2 seconds?
Answer: This is NORMAL operation for a permanent magnet
starter (Sky-Tec LS, PM, CST2, & FST1 models). Although
power is removed by releasing the key/start button, a permanent
magnet motor will actually provide power to itself as it winds-
down and will keep the starter drive engaged for about a half-
second until it loses sufficient RPM to fully disengage.
I never thought about it, so good point.
I personally have a SkyTec HT model (wire wound) Hi-torque
starter. It does not have the run-on characteristic or idiosyncrasy
like the PM model. I guess the PM is OK with it, but agree it is
not the way I would prefer, so a FW contactor may be a good
idea for this application.
SkyTec also has a NEW in-line unit which they claim is the #1
selling starter. http://www.skytecair.com/
PM starters have the advantage in lower cost and lower weight. I
had a Skytec PM on my RV-4 for 900 hours before I sold the plane,
however I ran it with a secondary contactor in the firewall, with no
problems. Besides the 1/2 to 1 second run on they use more current
than wire wound starters. The Pro is they are cheaper and lighter.
There are Pros and Cons to everything, however with the point you
make about PM starters, the FW contactor is probably more of a plus.
Also you have piece of mind of not having a big gauge wire HOT
all the time, which is a concern to many.
The Pro of leaving the solenoid off is less weight, wiring and cost,
albeit small. With a wire wound starter the spin down is not an issue.
Nothing works in all situations and there is rarely an absolute
perfect solution. As I said before the FW solenoid works in most
cases and has advantages, however leaving it off is an alternative
option that the individual should explore and consider.
For me with a wire wound starter, the extra PARTS did not make it
into my design, and since my starter is not permanent magnet (PM)
I can GET AWAY with it with little down side. However I do it with
eyes wide open, knowing the Pros and Cons.
Good debate and points. I understand your position Bob.
Cheers George
---------------------------------
Message 7
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| Subject: | Re: Air Speed Switch |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 06:25 PM 4/7/2006 +0000, you wrote:
>--> AeroElectric-List message posted by: dsvs@comcast.net
>
>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 >
Message 8
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| Subject: | Air Speed Switch |
--> AeroElectric-List message posted by: "DonVS" <dsvs@comcast.net>
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
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of Robert
L. Nuckolls, III
Sent: Saturday, April 08, 2006 3:52 PM
Subject: Re: AeroElectric-List: Air Speed Switch
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<nuckollsr@cox.net>
At 06:25 PM 4/7/2006 +0000, you wrote:
>--> AeroElectric-List message posted by: dsvs@comcast.net
>
>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 >
Message 9
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| Subject: | Air Speed Switch |
--> AeroElectric-List message posted by: "Hinde, Frank George (Corvallis)" <frank.hinde@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
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Robert L. Nuckolls, III
Sent: Saturday, April 08, 2006 3:52 PM
Subject: Re: AeroElectric-List: Air Speed Switch
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
--> <nuckollsr@cox.net>
At 06:25 PM 4/7/2006 +0000, you wrote:
>--> AeroElectric-List message posted by: dsvs@comcast.net
>
>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 >
Message 10
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| Subject: | Air Speed Switch |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 07:37 PM 4/8/2006 -0700, you wrote:
>--> AeroElectric-List message posted by: "DonVS" <dsvs@comcast.net>
>
>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 . . .
Message 11
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| Subject: | Air Speed Switch |
--> AeroElectric-List message posted by: "DonVS" <dsvs@comcast.net>
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
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of Robert
L. Nuckolls, III
Sent: Saturday, April 08, 2006 8:29 PM
Subject: RE: AeroElectric-List: Air Speed Switch
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<nuckollsr@cox.net>
At 07:37 PM 4/8/2006 -0700, you wrote:
>--> AeroElectric-List message posted by: "DonVS" <dsvs@comcast.net>
>
>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 . . .
Message 12
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| Subject: | Air Speed Switch |
--> AeroElectric-List message posted by: Richard Riley <richard@riley.net>
At 07:37 PM 4/8/2006, you wrote:
>--> AeroElectric-List message posted by: "DonVS" <dsvs@comcast.net>
>
>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@pacbell.net
www.veproducts.com
Part #654A53.2
Message 13
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| Subject: | Air Speed Switch |
--> AeroElectric-List message posted by: "Jim Baker" <jlbaker@msbit.net>
> 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.
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
Message 14
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| Subject: | Air Speed Switch |
--> AeroElectric-List message posted by: "Dave Morris \"BigD\"" <BigD@DaveMorris.com>
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:
>--> AeroElectric-List message posted by: "Hinde, Frank George
>(Corvallis)" <frank.hinde@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
>
>-----Original Message-----
>From: owner-aeroelectric-list-server@matronics.com
>[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
>Robert L. Nuckolls, III
>Sent: Saturday, April 08, 2006 3:52 PM
>To: aeroelectric-list@matronics.com
>Subject: Re: AeroElectric-List: Air Speed Switch
>
>--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
>--> <nuckollsr@cox.net>
>
>At 06:25 PM 4/7/2006 +0000, you wrote:
>
> >--> AeroElectric-List message posted by: dsvs@comcast.net
> >
> >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 >
>
>
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