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tim2542(at)sbcglobal.net
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 Posted: Sat Dec 26, 2009 2:28 pm Post subject: Switches |
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I’m looking for a nice switch to use in a speed brake/landing gear control panel I want to make. I could of course just use toggle switches but I wanted something little nicer. I found these rotary lever switches https://www.mouser.com/catalog/640/2375.PDF from electro switch, there very nice, smooth and just what I want
but they don’t have the rating I need (10 amps). I’m trying to avoid using a relay. I’m open to suggestions; I have been all over the internet without any luck.
Thanks, Tim Andres
[quote][b]
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racerjerry
Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY
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| Posted: Sun Dec 27, 2009 7:24 am Post subject: Re: Switches |
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“Nice“ switches are for non-critical applications far away from airplanes. If you value reliability and/or your life, pick a snap action switch with proper rating that has been tested and qualified with a MS (Military Specification) number attached to it.
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nuckolls.bob(at)aeroelect
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| Posted: Sun Dec 27, 2009 8:38 am Post subject: Switches |
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At 09:24 AM 12/27/2009, you wrote:
| Quote: |
"Nice" switches are for non-critical applications far away from
airplanes. If you value reliability and/or your life, pick a snap
action switch with proper rating that has been tested and qualified
with a MS (Military Specification) number attached to.
|
Perceived reliability of individual parts does not
directly contribute to reliability of whole systems.
As I explained in chapter 17, one may craft very reliable
systems from components that are not selected just
for their exemplary service life. Super-parts are not
offered as "failure free" . . . just longer service life
between failures. System reliability is a byproduct of
crafting alternatives for the failure of any system useful
for comfortable termination of flight.
This is an important concept that accounts for the
failure of any system component, poor craftsmanship,
accident, etc. In other words, the sources for in-flight
misery go far beyond the selection of specific components.
The failure tolerant flight system can suffer from an
extra-ordinary frequency of events that drive up maintenance
time and expense . . . without degrading reliability.
Here I'll suggest that system reliability is judged by
one's ability to suffer the failure of any component
and proceed to original airport of intended destination
without breaking a sweat.
I'm not suggesting that "super-parts" should not be
considered. I do suggest that placing one's faith
in their ability to ward off sweaty cockpits is misplaced.
All the super-testing in the world does nothing for
you when the landing light burns out, the terminal
breaks or the radio decides to quit (as all radios
eventually do).
Failure tolerance flows out of an analysis of failure
mode effects for equipment YOU have installed for use
in the environment YOU intend to fly and is dependent
upon YOUR understanding of system functionality.
Remember that decades of dark-n-stormy night stories
have demonstrated the inadequacy of 'certified' aviation
products operated by pilots who were lead to believe
that getting their ticket from an approved school was
the golden shield against sweaty experiences in the cockpit.
Those of us who buck rivets, turn wrenches and string
wires in the garage have already accepted the need
for extra ordinary skill and knowledge. Shopping
for the Mil-Spec part doesn't cut it.
Bob . . .
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nuckolls.bob(at)aeroelect
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| Posted: Sun Dec 27, 2009 8:47 am Post subject: Switches |
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At 04:25 PM 12/26/2009, you wrote:
| Quote: | Im looking for a nice switch to use in a speed brake/landing gear control panel I want to make. I could of course just use toggle switches but I wanted something little nicer. I found these rotary lever switches https://www.mouser.com/catalog/640/2375.PDF from electro switch, there very nice, smooth and just what I want
but they dont have the rating I need (10 amps). Im trying to avoid using a relay. Im open to suggestions; I have been all over the internet without any luck.
Thanks, Tim Andres |
These are open frame, wafer switches fitted with
long throw handles as opposed to rotary shafts.
These switches have been around for decades and
are widely used in communications. Their open
construction makes them unattractive for harsh
industrial or aviation environments.
In the TC aircraft world, this style of switch
has been considered and rejected many times.
Consider emulating the approach taken by Beech
and others illustrated here:
http://aeroelectric.com/Pictures/Switches/FLAPS3.JPG
http://aeroelectric.com/Pictures/Switches/FLAPS2.JPG
http://aeroelectric.com/Pictures/Switches/FLAPS1.JPG
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
[quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Sun Dec 27, 2009 2:19 pm Post subject: Switches |
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| Quote: | The circuit that I don't understand is in Z-19. It's the ENG BAT,
OFF/ON/Auto circuit using a 700-2-10 switch. When switched to the
3rd position, contacting pin 4, what happens? Pin 4 goes to the
'Relay' pin of the LoVo monitor.
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Okay. THAT drawing shows the AEC9005 Aux Battery
Management/LV Warning module . . .
http://www.aeroelectric.com/Catalog/AEC/9005/LV_Warn_Fab_and_Install.pdf
The 3-position Aux Battery switch in question offers an
OFF function at full down, a manual ON function at
the mid position and an AUTOMATIC management function
at the full up position. This functionality is described
in the document cited above.
The 9005 is being replaced by versions of the 9024 reviewed
at . . .
http://www.aeroelectric.com/Catalog/AEC/9024/
with applications illustrated at . . .
http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z09A.pdf
P.S. Figure Z-09 for the Corvair engine only illustrates
three of the four features offered by the 9024. The fourth
function just happens to be the Aux Battery Management Module.
Nonetheless, there are 4 possible functions for this
product.
Bob . . .
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tim2542(at)sbcglobal.net
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| Posted: Sun Dec 27, 2009 4:03 pm Post subject: Switches |
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Thanks Bob; I guess I knew but forgot the points you made, should have known
better. I see what I want around but it's made for heavy iron and cost like
it also.
Tim
________________________________________
From: owner-aeroelectric-list-server(at)matronics.com
[mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Sunday, December 27, 2009 8:46 AM
To: aeroelectric-list(at)matronics.com
Subject: Re: Switches
At 04:25 PM 12/26/2009, you wrote:
Im looking for a nice switch to use in a speed brake/landing gear control
panel I want to make. I could of course just use toggle switches but I
wanted something little nicer. I found these rotary lever switches
https://www.mouser.com/catalog/640/2375.PDF from electro switch, there very
nice, smooth and just what I want
but they dont have the rating I need (10 amps). Im trying to avoid using a
relay. Im open to suggestions; I have been all over the internet without
any luck.
Thanks, Tim Andres
These are open frame, wafer switches fitted with
long throw handles as opposed to rotary shafts.
These switches have been around for decades and
are widely used in communications. Their open
construction makes them unattractive for harsh
industrial or aviation environments.
In the TC aircraft world, this style of switch
has been considered and rejected many times.
Consider emulating the approach taken by Beech
and others illustrated here:
http://aeroelectric.com/Pictures/Switches/FLAPS3.JPG
http://aeroelectric.com/Pictures/Switches/FLAPS2.JPG
http://aeroelectric.com/Pictures/Switches/FLAPS1.JPG
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
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racerjerry
Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY
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| Posted: Sun Dec 27, 2009 4:57 pm Post subject: Re: Switches |
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OK! Shot down by the master – I respect Bob’s arguments; however, I do not consider a $20 Mil-Spec switch to be a super-part. Certainly we can use commercial grade switches in our homebuilt aircraft, but it is still prudent to insure that the switches have undergone some reliability testing and have current and voltage ratings appropriate for their intended use. Certification by a nationally recognized testing agency such as Underwriters Laboratories may add to the switches cost a bit, but the rating confirms that required overload and endurance testing have been successfully completed.
The lever actuated open frame rotary type switch that Tim proposed to use was almost a guaranteed failure point. Besides susceptibility to contamination of the open switch contacts by dirt and dust, arc characteristics of direct current require a switch that rapidly breaks the circuit in order to prevent excessive arcing damage to the switch contacts; most especially when 10 ampere loads are contemplated. A snap-action type switch has much greater survivability chances under heavy DC loads.
I see that Bob has suggested a possible alternative, a bolt on extension to the switch bat handle. Keep in mind that Bob’s addition ENHANCES safety. This extension allows the pilot to quickly and positively locate the flap switch by feel without the necessity of removing eyes from the windshield; kinda’ important when you are close to the ground. If you are tempted to add such extensions willy-nilly just because they look pretty, keep in mind that these extensions can possibly do a lot of damage during a survivable crash when body parts are violently thrown about to the limits of the restraint system (and then some). Everything has its price, including “cutesy.”
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Jerry King |
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Mon Dec 28, 2009 9:10 am Post subject: Switches |
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At 06:01 PM 12/27/2009, you wrote:
| Quote: |
Thanks Bob; I guess I knew but forgot the points you made, should have known
better. I see what I want around but it's made for heavy iron and cost like
it also.
|
Yeah. I've participated in the design of a number
of specialized cockpit controls for things like
gear, flaps, spoilers, etc. In addition to their
unique form and fit requirements to comply with
design goals for cockpit decorum, they often
included a variety of position sensors with redundancy
to preclude un-commanded motions, etc.
I think the last flap control handle project I
saw produced a device that sold to the OEM for
about $2,000!
Here in the OBAM aircraft world, we can do a lot
to dress up plain vanilla controls. But the
Big Guys do it too. The gear and flap switches
in a Bonanza are Honeywell toggle switches with
added window dressing.
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Mon Dec 28, 2009 9:35 am Post subject: Switches |
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At 06:57 PM 12/27/2009, you wrote:
OK! Shot down by the master! I respect Bob's arguments; however, I
do not consider a $20 Mil-Spec switch to be a super-part. Certainly
we can use commercial grade switches in our homebuilt aircraft, but
it is still prudent to insure that the switches have undergone some
reliability testing and have current and voltage ratings appropriate
for their intended use. Certification by a nationally recognized
testing agency such as Underwriters Laboratories may add to the
switches cost a bit, but the rating confirms that required overload
and endurance testing have been successfully completed.
Are we shooting at each other or trying to achieve a
shared understanding? How does one conduct such
pre-purchase studies? I'm fairly certain that
every manufacturer did some pre-production proof
of design testing to insure compliance with their
own design goals. But few if any have published
reports on such studies unless they're attempting
to compete with other manufacturers where the
rules of the game call out Mil-Spec, SAE, ISO,
UL, etc. etc. I'll suggest that there are many
sources of switches suited to our tasks that offer
no published test data. Further, when data is
available, it was not gathered by the same test
protocols as competing products. I went through
this exercise 20+ years ago on the GP-180 program
at Gates-Learjet. Attempts to evaluate 6 different
brands of interchangeable basic switches based on
their published data proved impossible. But in
fact, every device being considered would have
been just fine for our application.
I would invite you to review a paper I wrote some
years ago about switch ratings at:
http://www.aeroelectric.com/articles/Switch_Ratings.pdf
Switch "ratings" are not a common language among
all manufacturers of switches . . . else there
would not be so many ratings standards by which
the folks who write rules for aforementioned games
can choose. Further, the ratings games are crafted
with the revenue generating applications (down time
on a $high$ machine costs many times more than the
value of the switch), safety issues in both industrial
and military hardware (switch failure increases risk
of injury or death).
In the OBAM aircraft environment, we assume risks
of for lack of knowledge and craftsmanship that are
generally considered to be very low numbers in the
commercial, industrial and military worlds. Hence
my vociferous suggestions that we place failure
tolerance above all other considerations for the
design, operation and maintenance of our airplanes.
A search of the accident archives reveals that
failures of electrical system components in light
aircraft account for a tiny proportion of causation
for the accident. In those situations where electrical
failures were prominent players, it was easy to deduce
in hindsight how that stack-up of events could have
been comfortably managed by the failure tolerant
aircraft flown by a knowledgeable pilot. I don't
recall reading ANY accident analysis where failure
of a component to perform as advertised was a
contributing factor. No doubt there are SOME such
reports but I've not found one yet.
It's been my suggestion for years of participation
first on Compuserve AVSIG and later here on the
Matronics Lists that we can design, fabricate
and operate airplanes using the most ordinary components
and still enjoy very low risk use of the airplane's
electrical system. This is especially true of machines
that get on average, 50 hours of service per year
as opposed to machines that run 1000's of hours
per year.
Bob . . .
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