Today's Message Index:
----------------------
1. 09:03 AM - Re: Z-12 contactor failure (Robert L. Nuckolls, III)
2. 10:00 AM - Z12 contactor failure (CORRECTION) (Robert L. Nuckolls, III)
3. 07:14 PM - Re: Z-12 contactor failure (FLYaDIVE)
4. 10:06 PM - Re: Z-12 contactor failure (Bob Verwey)
Message 1
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Subject: | Re: Z-12 contactor failure |
Bob:
Yup There are all sorts of 'possible' possibilities, all without
proof, but it DOES WORK!
Many of our aircraft are 40+ years old. The original lubricants in
the switches have long disappeared.
They are NOT sealed switches.
What has worked for many years are now failing. Just look Brandon's post.
And, when it comes to the Stall Warning micro switch - Replacement
with NEW is $1200+ used, about $600 to $700.
All this can be prevented with a can of WD-40!
WD40 can be useful in the maintenance of electro-whizzies
with moving parts . . . and indeed, it was not originally
designed to be a lubricant so much as a (W)ater (D)isplacer
and cleaner. As a side benefit, it does have some degree of
lubricity . . . as do many substances . . . but its service
life as a lubricant is far outpaced by other products designed
for lubrication.
https://goo.gl/sbPhXj
WD40 was major maintenance feature for the MQM107 target
we used to build at Beech.
https://goo.gl/otFkbp
The engine was a very short service life device with
minimal moving parts and INTENDED to become totally
immersed in seawater during an offshore recovery.
The first refurbishment move for the aircraft was to remove
the engine and submerge it in a barrel of WD40. When the
aircraft was ready to receive the engine, they hauled it out
with compressed air and bolted it back on the airframe.
Not needed on sealed DPST Toggle Switches. AND they are NOT 40+ years old.
Obviously, a truly sealed switch cannot benefit from
spray on remedies . . .
I can't see how applying a lubricant like WD40 can be advantageous to
the contacts on the switch...surely there will be burning volatiles
or lube which would affect the service or life of the part? On the
moving parts yes but I don't know of a way to differentiate with a spray can.
WD40 is often applied to moving part for
the purpose of loosening corrosion and flushing
out small particulates while displacing any
moisture present. The combustible VOLATILES are
just that . . .they quickly dissipate after carrying
WD40 'magic juice' to the intended surfaces.
If the Master Switch failed why reinvent the wheel?
Since this was a certified plane you are forced to work with the
design of the time.
What I have found is 99.982% of certified plane owners and A&P's,
NEVER address the Master Switch during Annual.
It should be addressed every Annual and it is very easy to do:
1 - Spray the heck out of it with Contact Cleaner.
2 - Cycle the switch a couple of dozen times.
3 - Spray it with WD-40.
My first job at Cessna extended over 5 years
in the technical publications department where,
among other things, I wrote repair and preventative
maintenance narratives in Cessna's service manuals.
Emacs!
The policy of the company was to 'replace on condition'
meaning that devices like relays and toggle switches
were considered and sometimes tested to see that
they met service life design goals. If a such a device
were to mis-behave, it was time to replace it. Hence
no maintenance or refurbishment methods were offered
or required.
Side Note: This also goes for the micro-switch in the Stall Warning System.
The basic switch used on the legacy stall warning
sensor was a Honeywell BZ series commercial off
the shelf device with very low operating force
(measured in grams). Of course, as a component
in a PMA/TSO product, the owner operator was prohibited
from replacing said switch for $20 (and I wasn't
allowed to write a procedure for it either).
These are not sealed switches and they're mounted
in one of the more hostile environments on the airplane.
Depending on the mis-behavior mode, an application
of WD40 may well free up things and restore normal
operation . . . but a switch that was not working
normally was probably pretty long in the tooth. Depending
on criticality of the device, it may well be better
to replace as opposed to refurbish the individual
switch.
On Experimental Aircraft you have a HUGE ADVANTAGE...
Use a Heavy Duty Master Switch and a Separate Heavy Duty Alternator Switch.
I use DPST switches and tie BOTH sides together. This DOUBLES the
physical as well as the electrical rating of the switch.
Paralleling contacts only doubles the CARRY
rating of a switch . . . it does not double
opening or closing ratings.
Want to go extra fancy? Look for switches that are Sliver Plated.
Silver plating or solid silver contacts are
rare and intended for specific applications . . .
which generally do not include switching
DC power. Cadmium Silver contacts are used in
the more robust designs favored by mil-spec
designs . . . but I suspect the Carling style
products used on hundreds of thousands of TC
aircraft are not so 'fancy' . . . yet demonstrably
adequate to task.
You can also use switches that have a built in Dust/Moisture
shield. OR... Install the dust/Moisture shield over the Toggle Lever.
Side Note: On certified planes with the standard split Master/Alt
Switch, there are four (4) failure points:
1 - The Physical snap action of the switch.
2 - The Electrical contacts of the switch.
3 - Fast-On tabs on the back of the switch.
4 - The Physical MOUNTING of the switch. There is a snap in bezel
that holds the switch into the panel.
This bezel fails as the ears either break off or loose their spring action.
Then the switch vibrates forward and shorts out to the aluminum panel.
The cure is to use two (2) sheet metal round head screws on either
side to hold the bezel in place.
If the switch vibrates out it will short out and take your Master/Alt
switch and Starter Relay out of the circuit.
If you are airborne - You loose even the ability to go to Battery Back-up.
Or do an in-flight re-start.
Scary!
Can you cite any service difficulty report
that describes such a failure of the mounting?
These switches are used by hundreds of thousands
for about 50 years. I find it curious that
anyone would find them (1) lacking in design
to intended task and/or (2) figuring significantly
on the list of probable failure that creates
a hazard to flight.
I know it is not a likely case, but I have experienced a contactor
failure on a production plane in flight. It ended up that the root
cause was a defective master switch - but the result was the
same. Because there was no endurance bus alternate feed, it was a
full electrical shutdown, in IMC no less!
Then it wasn't a contactor failure but a switch failure.
How did it manifest in flight? i.e. how did you become
aware of the failure? Did things simply go black?
I would like to know if there is a practical way to protect for
contactor failure ( other than battery only operation ) with the Z-12
design. It would be nice to have a second path to the battery from
aux alternator to ensure stable power if the master does fail.
You can move the aux alternator wiring to the
hot side of the battery contactor . . . it's
just that simple.
The appeal to me of having an aux alternator is to be able to
continue flight on one alternator. This is only possible if either a
battery connection is maintained always or it is a guarantee the
alternator will provide stable power without a battery connection.
Batteryless operation is likely but cannot
be guaranteed without testing on your airplane
with your constellation of hardware. As I've mentioned,
there are Beechcraft piston aircraft wherein battery-off
operation is described and permitted as a matter of
design and verification by flight testing. It's covered
in the POH.
For this forum cannot make configuration/operation
recommendations without conducting similar investigations
as to meeting design goals
The Z-13/8 uses a relay with the SD-8 alternator to connect directly
to battery. Is this design practical or even advisable with the
SD-20 alternator? With Z-13/8 the aux alternator will provide power
to battery bus and E-BUS if contactor fails.
Exactly. If you wish, you can certainly wire the SD20
in a manner suggested by Z13/8. There are no 'rules'
that would prohibit you from doing so.
When I took Z13/20 off the table about 10 years ago,
it was because it added a degree of complexity
over Z12 that did not materially reduce risk.
In fight contactor failure is exceedingly rare.
Smoke in the cockpit probably has a higher degree
of probability . . . in which instance you may
wish to shot the whole system down anyhow.
Any of you who have attended my weekend seminars
may remember this slide:
Emacs!
The last 200-300 hours of my flying days were
carried out with these three items in my flight
bag. Since I flew nothing but rentals, I had little
insight as to the history of electrical/electronics
systems. I was prepared to continue flight to intended
destination with the master switch OFF.
Indeed, the performance of these $100 hand-held
gps receivers so exceeded the panel mounted stuff
that those last hundreds of hours were flown with
DUAL gps receivers 'mounted' to the glare-shield
and windshield with little blobs of windshield
sealant. Never touched a VOR receiver or even
the panel mounted GPS receivers again.
As I describe in Chapter 17 of the 'Connection,
system reliability has far more to do with pilot
skills and careful crafting of a Plan-B than it
does on any selection of system hardware. The
carefully crafted architecture and pilot's personal
bag of tricks strives for failure tolerance . . . not
failure proofing. The later cannot be achieved.
Bob . . .
Message 2
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Subject: | Z12 contactor failure (CORRECTION) |
<snip>
In-fight contactor failure is exceedingly rare.
Smoke in the cockpit probably has a higher degree
of probability . . . in which instance you may
wish to shot the whole system down anyhow.
Any of you who have attended my weekend seminars
may remember this slide:
Emacs!
The last 200-300 hours of my flying days were
carried out with these three items in my flight
bag. Since I flew nothing but rentals, I had little
insight as to the history of electrical/electronics
systems. I was prepared to continue flight to intended
destination with the master switch OFF.
Indeed, the performance of these $100 hand-held
gps receivers so exceeded the panel mounted stuff
that those last hundreds of hours were flown with
DUAL gps receivers 'mounted' to the glare-shield
and windshield with little blobs of windshield
sealant. Never touched a VOR receiver or even
the panel mounted GPS receivers again.
As I describe in Chapter 17 of the 'Connection,
system reliability has far more to do with pilot
skills and careful crafting of a Plan-B than it
does on any selection of system hardware. The
carefully crafted architecture and pilot's personal
bag of tricks strives for failure tolerance . . . not
failure proofing. The later cannot be achieved.
Bob . . .
Message 3
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Subject: | Re: Z-12 contactor failure |
Bob:
You are going off on tangents - - -
On Mon, Apr 23, 2018 at 12:02 PM, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> Bob:
>
> Yup There are all sorts of 'possible' possibilities, all without proof,
> but it DOES WORK!
> Many of our aircraft are 40+ years old. The original lubricants in the
> switches have long disappeared.
> They are NOT sealed switches.
> What has worked for many years are now failing. Just look Brandon's post
.
> And, when it comes to the Stall Warning micro switch - Replacement with
> NEW is $1200+ used, about $600 to $700.
> All this can be prevented with a can of WD-40!
>
> WD40 can be useful in the maintenance of electro-whizzies
> with moving parts . . . and indeed, it was not originally
> designed to be a lubricant so much as a (W)ater (D)isplacer
> and cleaner. As a side benefit, it does have some degree of
> lubricity . . . as do many substances . . . but its service
> life as a lubricant is far outpaced by other products designed
> for lubrication.
>
> =8BBarry - Nobody said it was being used as a lubricant, only you.
It will
work as a lubrcant to the contact areas of plastic switches and even the
metal pivot points. How long will it last? I don't know... As I said in
my post; A&P seldom address switches and many of these switches are 40 +
years old. So, anything that one can do to extend their life or rejuvenate
them is a good thing. Back to the WD... It is being used =8B
=8Bas a WD and as a CLEANER!
Oh wait... Can it be used as a cleaner???
DEFINITELY YES!=8B
Do you have proof that it can't be?
https://goo.gl/sbPhXj
>
> WD40 was major maintenance feature for the MQM107 target
> we used to build at Beech.
>
=8BBarry - So!!! Who cares!=8B
>
> https://goo.gl/otFkbp
>
> The engine was a very short service life device with
> minimal moving parts and INTENDED to become totally
> immersed in seawater during an offshore recovery.
>
=8BBarry - Want more info on this subject? I did salvage and artifa
ct
recovery way-way back in the 70's and 80's .
Who cares!=8B
>
> The first refurbishment move for the aircraft was to remove
> the engine and submerge it in a barrel of WD40. When the
> aircraft was ready to receive the engine, they hauled it out
> with compressed air and bolted it back on the airframe.
>
> Not needed on sealed DPST Toggle Switches. AND they are NOT 40+ years ol
d.
>
> Obviously, a truly sealed switch cannot benefit from
> spray on remedies . . .
>
=8BBarry - That's why I said you CYCLE the Switches a couple dozen ti
mes.=8B
=8BWhy are you going off on so many tangents?=8B
>
> I can't see how applying a lubricant like WD40 can be advantageous to the
> contacts on the switch...surely there will be burning volatiles or lube
> which would affect the service or life of the part? On the moving parts y
es
> but I don't know of a way to differentiate with a spray can.
>
> WD40 is often applied to moving part for
> the purpose of loosening corrosion and flushing
> out small particulates while displacing any
> moisture present. The combustible VOLATILES are
> just that . . .they quickly dissipate after carrying
> WD40 'magic juice' to the intended surfaces.
>
=8BBarry - You advertise yourself as an engineer. =8B
=8BIf so, why are you so closed minded to other possibilities?
=8B
There are curtain things in physics that cannot be changed, but how a
product can be used and to Great Advantages is sure out there.
>
> If the Master Switch failed why reinvent the wheel?
>
> Since this was a certified plane you are forced to work with the design o
f
> the time.
> What I have found is 99.982% of certified plane owners and A&P's, NEVER
> address the Master Switch during Annual.
>
> It should be addressed every Annual and it is very easy to do:
> 1 - Spray the heck out of it with Contact Cleaner.
> 2 - Cycle the switch a couple of dozen times.
> 3 - Spray it with WD-40.
>
> My first job at Cessna extended over 5 years
> in the technical publications department where,
> among other things, I wrote repair and preventative
> maintenance narratives in Cessna's service manuals.
>
=8BBarry - So what? Anybody can sit down behind a desk and write a ma
nual.
I have for a few dozen Environmental Test procedures. ANYTHING can be
written.
Ask the A&P and IA that is TRY to follow =8B
=8Bwhat some paper-pusher =8Bwrote IF it is possible.
Ask the plane owner who has to pay the bill why a simple thing like the
Cessna Seat Rail Tracks has to be replace and WHY it is so expensive!
=8B Or how to replace the Flap Motor on a Cessna.=8B
> [image: Emacs!]
>
> The policy of the company was to 'replace on condition'
> meaning that devices like relays and toggle switches
> were considered and sometimes tested to see that
> they met service life design goals. If a such a device
> were to mis-behave, it was time to replace it. Hence
> no maintenance or refurbishment methods were offered
> or required.
>
> Side Note: This also goes for the micro-switch in the Stall Warning
> System.
>
> The basic switch used on the legacy stall warning
> sensor was a Honeywell BZ series commercial off
> the shelf device with very low operating force
> (measured in grams). Of course, as a component
> in a PMA/TSO product, the owner operator was prohibited
> from replacing said switch for $20 (and I wasn't
> allowed to write a procedure for it either).
>
> These are not sealed switches and they're mounted
> in one of the more hostile environments on the airplane.
> Depending on the mis-behavior mode, an application
> of WD40 may well free up things and restore normal
> operation . . . but a switch that was not working
> normally was probably pretty long in the tooth. Depending
> on criticality of the device, it may well be better
> to replace as opposed to refurbish the individual
> switch.
>
>
> On Experimental Aircraft you have a HUGE ADVANTAGE...
> Use a Heavy Duty Master Switch and a Separate Heavy Duty Alternator Switc
h.
> I use DPST switches and tie BOTH sides together. This DOUBLES the
> physical as well as the electrical rating of the switch.
>
> Paralleling contacts only doubles the CARRY
> rating of a switch . . . it does not double
> opening or closing ratings.
>
> Want to go extra fancy? Look for switches that are Sliver Plated.
>
> Silver plating or solid silver contacts are
> rare and intended for specific applications . . .
> which generally do not include switching
> DC power. Cadmium Silver contacts are used in
> the more robust designs favored by mil-spec
> designs . . . but I suspect the Carling style
> products used on hundreds of thousands of TC
> aircraft are not so 'fancy' . . . yet demonstrably
> adequate to task.
>
=8BBarry - YES - They Are! But, as the fellow whom had the failure w
as
talking and as I was saying:
These switches have NOT been addressed during Annuals over MANY - MANY
YEARS! =8B
=8BThe Experimental Owner has Great Advantages over the Certified Own
er by
making small changes that GREATLY extend the life and as you are so
vigorous to report on 'Reduction of Failure Points'. So, why shouldn't they
look for the better switch.
Silver Plated or CadSilver?
GAUD! Which way did you part the gnat's hairs on that one?
Walking into a electronics store, the Simple question: Do you have any
Silver Plated Contact Switch? Will result in the SAME results! When I
order Manure I don't care if it is horse or cow. Either one will work!
>
> You can also use switches that have a built in Dust/Moisture shield.
> OR... Install the dust/Moisture shield over the Toggle Lever.
>
> Side Note: On certified planes with the standard split Master/Alt Switch
,
> there are four (4) failure points:
> 1 - The Physical snap action of the switch.
> 2 - The Electrical contacts of the switch.
> 3 - Fast-On tabs on the back of the switch.
> 4 - The Physical MOUNTING of the switch. There is a snap in bezel that
> holds the switch into the panel.
> This bezel fails as the ears either break off or loose their spring actio
n.
> Then the switch vibrates forward and shorts out to the aluminum panel.
> The cure is to use two (2) sheet metal round head screws on either side
> to hold the bezel in place.
> If the switch vibrates out it will short out and take your Master/Alt
> switch and Starter Relay out of the circuit.
> If you are airborne - You loose even the ability to go to Battery Back-up
.
> Or do an in-flight re-start.
> Scary!
>
> Can you cite any service difficulty report
> that describes such a failure of the mounting?
>
=8BBarry - You must LOVE AD's!
I found the problem twice. I fixed the problem twice.=8B
=8BYES! The switches have lasted for many years. Does that mean the
y cannot
fail? And, as I said: It was not the switch. It was the mounting bezel.
Just because a FAA 8070-1 report not exist AND I do not know if one does or
does not exist, does not mean the problem does not exist.
=8BJust look at the design of the retaining bezel and even you should
be able
to see there is a potential failure point.
ESPECIALLY! When the switch is removed in tracking down a wiring issue.
There are more things in Heaven and Earth Horatio than even Bob has
knowledge on.
Barry
These switches are used by hundreds of thousands
> for about 50 years. I find it curious that
> anyone would find them (1) lacking in design
> to intended task and/or (2) figuring significantly
> on the list of probable failure that creates
> a hazard to flight.
>
Message 4
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Subject: | Re: Z-12 contactor failure |
Gee Wizz Barry,
Many have taken on Bob N, and many have failed....
In all the 15 + years I have been a member of this forum, the thing that
has impressed me most is the decorum of the participants....just sayin!
Best...
Bob Verwey
082 331 2727
On 24 April 2018 at 04:12, FLYaDIVE <flyadive@gmail.com> wrote:
> Bob:
>
> You are going off on tangents - - -
>
> On Mon, Apr 23, 2018 at 12:02 PM, Robert L. Nuckolls, III <
> nuckolls.bob@aeroelectric.com> wrote:
>
>> Bob:
>>
>> Yup There are all sorts of 'possible' possibilities, all without proof,
>> but it DOES WORK!
>> Many of our aircraft are 40+ years old. The original lubricants in the
>> switches have long disappeared.
>> They are NOT sealed switches.
>> What has worked for many years are now failing. Just look Brandon's pos
t.
>> And, when it comes to the Stall Warning micro switch - Replacement with
>> NEW is $1200+ used, about $600 to $700.
>> All this can be prevented with a can of WD-40!
>>
>> WD40 can be useful in the maintenance of electro-whizzies
>> with moving parts . . . and indeed, it was not originally
>> designed to be a lubricant so much as a (W)ater (D)isplacer
>> and cleaner. As a side benefit, it does have some degree of
>> lubricity . . . as do many substances . . . but its service
>> life as a lubricant is far outpaced by other products designed
>> for lubrication.
>>
>> =8BBarry - Nobody said it was being used as a lubricant, only you.
It will
> work as a lubrcant to the contact areas of plastic switches and even the
> metal pivot points. How long will it last? I don't know... As I said
in
> my post; A&P seldom address switches and many of these switches are 40 +
> years old. So, anything that one can do to extend their life or rejuvena
te
> them is a good thing. Back to the WD... It is being used =8B
>
> =8Bas a WD and as a CLEANER!
> Oh wait... Can it be used as a cleaner???
> DEFINITELY YES!=8B
> Do you have proof that it can't be?
>
> https://goo.gl/sbPhXj
>>
>> WD40 was major maintenance feature for the MQM107 target
>> we used to build at Beech.
>>
> =8BBarry - So!!! Who cares!=8B
>
>
>>
>> https://goo.gl/otFkbp
>>
>> The engine was a very short service life device with
>> minimal moving parts and INTENDED to become totally
>> immersed in seawater during an offshore recovery.
>>
> =8BBarry - Want more info on this subject? I did salvage and arti
fact
> recovery way-way back in the 70's and 80's .
> Who cares!=8B
>
>
>>
>> The first refurbishment move for the aircraft was to remove
>> the engine and submerge it in a barrel of WD40. When the
>> aircraft was ready to receive the engine, they hauled it out
>> with compressed air and bolted it back on the airframe.
>>
>> Not needed on sealed DPST Toggle Switches. AND they are NOT 40+ years
>> old.
>>
>> Obviously, a truly sealed switch cannot benefit from
>> spray on remedies . . .
>>
> =8BBarry - That's why I said you CYCLE the Switches a couple dozen
times.=8B
>
> =8BWhy are you going off on so many tangents?=8B
>
>>
>> I can't see how applying a lubricant like WD40 can be advantageous to th
e
>> contacts on the switch...surely there will be burning volatiles or lube
>> which would affect the service or life of the part? On the moving parts
yes
>> but I don't know of a way to differentiate with a spray can.
>>
>> WD40 is often applied to moving part for
>> the purpose of loosening corrosion and flushing
>> out small particulates while displacing any
>> moisture present. The combustible VOLATILES are
>> just that . . .they quickly dissipate after carrying
>> WD40 'magic juice' to the intended surfaces.
>>
> =8BBarry - You advertise yourself as an engineer. =8B
>
> =8BIf so, why are you so closed minded to other possibilities?
=8B
> There are curtain things in physics that cannot be changed, but how a
> product can be used and to Great Advantages is sure out there.
>
>>
>> If the Master Switch failed why reinvent the wheel?
>>
>> Since this was a certified plane you are forced to work with the design
>> of the time.
>> What I have found is 99.982% of certified plane owners and A&P's, NEVER
>> address the Master Switch during Annual.
>>
>> It should be addressed every Annual and it is very easy to do:
>> 1 - Spray the heck out of it with Contact Cleaner.
>> 2 - Cycle the switch a couple of dozen times.
>> 3 - Spray it with WD-40.
>>
>> My first job at Cessna extended over 5 years
>> in the technical publications department where,
>> among other things, I wrote repair and preventative
>> maintenance narratives in Cessna's service manuals.
>>
> =8BBarry - So what? Anybody can sit down behind a desk and write a
manual.
> I have for a few dozen Environmental Test procedures. ANYTHING can be
> written.
> Ask the A&P and IA that is TRY to follow =8B
>
> =8Bwhat some paper-pusher =8Bwrote IF it is possible.
> Ask the plane owner who has to pay the bill why a simple thing like the
> Cessna Seat Rail Tracks has to be replace and WHY it is so expensive!
> =8B Or how to replace the Flap Motor on a Cessna.=8B
>
>
>> [image: Emacs!]
>>
>> The policy of the company was to 'replace on condition'
>> meaning that devices like relays and toggle switches
>> were considered and sometimes tested to see that
>> they met service life design goals. If a such a device
>> were to mis-behave, it was time to replace it. Hence
>> no maintenance or refurbishment methods were offered
>> or required.
>>
>> Side Note: This also goes for the micro-switch in the Stall Warning
>> System.
>>
>> The basic switch used on the legacy stall warning
>> sensor was a Honeywell BZ series commercial off
>> the shelf device with very low operating force
>> (measured in grams). Of course, as a component
>> in a PMA/TSO product, the owner operator was prohibited
>> from replacing said switch for $20 (and I wasn't
>> allowed to write a procedure for it either).
>>
>> These are not sealed switches and they're mounted
>> in one of the more hostile environments on the airplane.
>> Depending on the mis-behavior mode, an application
>> of WD40 may well free up things and restore normal
>> operation . . . but a switch that was not working
>> normally was probably pretty long in the tooth. Depending
>> on criticality of the device, it may well be better
>> to replace as opposed to refurbish the individual
>> switch.
>>
>>
>> On Experimental Aircraft you have a HUGE ADVANTAGE...
>> Use a Heavy Duty Master Switch and a Separate Heavy Duty Alternator
>> Switch.
>> I use DPST switches and tie BOTH sides together. This DOUBLES the
>> physical as well as the electrical rating of the switch.
>>
>> Paralleling contacts only doubles the CARRY
>> rating of a switch . . . it does not double
>> opening or closing ratings.
>>
>> Want to go extra fancy? Look for switches that are Sliver Plated.
>>
>> Silver plating or solid silver contacts are
>> rare and intended for specific applications . . .
>> which generally do not include switching
>> DC power. Cadmium Silver contacts are used in
>> the more robust designs favored by mil-spec
>> designs . . . but I suspect the Carling style
>> products used on hundreds of thousands of TC
>> aircraft are not so 'fancy' . . . yet demonstrably
>> adequate to task.
>>
> =8BBarry - YES - They Are! But, as the fellow whom had the failure
was
> talking and as I was saying:
> These switches have NOT been addressed during Annuals over MANY - MANY
> YEARS! =8B
>
> =8BThe Experimental Owner has Great Advantages over the Certified O
wner by
> making small changes that GREATLY extend the life and as you are so
> vigorous to report on 'Reduction of Failure Points'. So, why shouldn't th
ey
> look for the better switch.
> Silver Plated or CadSilver?
> GAUD! Which way did you part the gnat's hairs on that one?
> Walking into a electronics store, the Simple question: Do you have any
> Silver Plated Contact Switch? Will result in the SAME results! When I
> order Manure I don't care if it is horse or cow. Either one will work!
>
>
>>
>> You can also use switches that have a built in Dust/Moisture shield.
>> OR... Install the dust/Moisture shield over the Toggle Lever.
>>
>> Side Note: On certified planes with the standard split Master/Alt
>> Switch, there are four (4) failure points:
>> 1 - The Physical snap action of the switch.
>> 2 - The Electrical contacts of the switch.
>> 3 - Fast-On tabs on the back of the switch.
>> 4 - The Physical MOUNTING of the switch. There is a snap in bezel that
>> holds the switch into the panel.
>> This bezel fails as the ears either break off or loose their spring
>> action.
>> Then the switch vibrates forward and shorts out to the aluminum panel.
>> The cure is to use two (2) sheet metal round head screws on either side
>> to hold the bezel in place.
>> If the switch vibrates out it will short out and take your Master/Alt
>> switch and Starter Relay out of the circuit.
>> If you are airborne - You loose even the ability to go to Battery Back-u
p.
>> Or do an in-flight re-start.
>> Scary!
>>
>> Can you cite any service difficulty report
>> that describes such a failure of the mounting?
>>
> =8BBarry - You must LOVE AD's!
> I found the problem twice. I fixed the problem twice.=8B
>
> =8BYES! The switches have lasted for many years. Does that mean t
hey
> cannot fail? And, as I said: It was not the switch. It was the mounting
> bezel.
>
> Just because a FAA 8070-1 report not exist AND I do not know if one does
> or does not exist, does not mean the problem does not exist.
> =8BJust look at the design of the retaining bezel and even you shou
ld be
> able to see there is a potential failure point.
> ESPECIALLY! When the switch is removed in tracking down a wiring issue.
>
> There are more things in Heaven and Earth Horatio than even Bob has
> knowledge on.
>
> Barry
>
> These switches are used by hundreds of thousands
>> for about 50 years. I find it curious that
>> anyone would find them (1) lacking in design
>> to intended task and/or (2) figuring significantly
>> on the list of probable failure that creates
>> a hazard to flight.
>>
>
>
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