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Switch Failures

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rv-9a-online(at)telus.net
Guest

Posted: Tue Jul 28, 2009 9:25 pm Post subject: Switch Failures

Approximately 100 hours ago, I replaced all of my Carling toggle switches 

with Honeywell/Microswitch switches in my RV-9A.   I had experienced 

multiple failures with the Carling switches in the first 150 hours due to 

loose terminals and overheating leading to charred terminals and wiring. 

There is a long thread on this topic, including some failure analysis by 

Bob.



At this point, I have had no additional switch failures after switching to 

the Honeywell switches.  At the time, Bob postulated that the lack of 

decoupling loops in the wiring may have contributed.  I was not so sure, so 

I made no other changes other than replacing the switches.



While not conclusive, I would say the root cause of failure was the loose 

riveted terminals on the Carling Switches.  The lack of decoupling loops in 

the wiring may have contributed, but it appears that a higher quality switch 

is an effective solution.



I had two failures on the Strobe circuit, one on the Landing light circuit 

and one on the progressive-transfer Master Switch in the first 150 hours 

with the Carling Switches.



So, if anyone thinks that this is just a characteristic of our OBAM aircraft 

being built with "substandard" components, look at this:



=======================



FAA Issues Airworthiness Bulletin For Cessna GA Aircraft

Tue, 28 Jul '09



SAIB Affects 100, 200, 300 Series Cessna Aircraft

 The FAA has issued a Special Airworthiness Information Bulletin (SAIB) to 

advise pilots and owners of an airworthiness concern on mandatory 

replacement intervals of Cessna Landing Light, Beacon Light, and Taxi Light 

switches on Cessna 100, 200, and 300 series airplanes, specified in Cessna 

service bulletins MEB09-3 and SEB09-6 dated May 11, 2009.



Cessna 100, 200, and 300 series airplanes utilize switches in the Landing 

Light, Beacon Light, and Taxi Light circuits that have been reported failing 

in the field causing overheating and smoke in the cockpit. There have been 

reports of burned insulation on the wiring terminals to the switch. On at

least one occasion, there was a small fire in the cockpit. The failure in 

these applications can be attributed to contact erosion leading to irregular 

arcing and eventual failure of the switch. The contact erosion has been 

shown to occur after approximately 4,000 cycles of operation.



Cessna service bulletins SEB09-6 and MEB09-3, initial release, dated May 11, 

2009, specify the following:



.An inspection to determine time-in-service for the switches.

.Replacement of switches that have been in service for four or more years 

with the month and year of the installation written on the new replacement 

switch.

.The month and year of the initial installation written on switches that 

have been in service for less than four years.

The FAA recommends that owners, operators, and maintenance technicians act 

on the above-referenced service bulletins within the next 400 hours of 

operation, 12 months, or the next annual inspection, whichever comes first.



=======

Vern Little

Vx Aviation

---

peterlaurence6(at)gmail.c
Guest

Posted: Wed Jul 29, 2009 5:43 am Post subject: Switch Failures

Vern 



Can you post the product number for the Honeywell switches?

Peter



On Wed, Jul 29, 2009 at 1:22 AM, Vern Little <rv-9a-online(at)telus.net (rv-9a-online(at)telus.net)> wrote:

 [quote]--> AeroElectric-List message posted by: "Vern Little" <rv-9a-online(at)telus.net (rv-9a-online(at)telus.net)>

  

 Approximately 100 hours ago, I replaced all of my Carling toggle switches with Honeywell/Microswitch switches in my RV-9A.   I had experienced multiple failures with the Carling switches in the first 150 hours due to loose terminals and overheating leading to charred terminals and wiring. There is a long thread on this topic, including some failure analysis by Bob.

  

 At this point, I have had no additional switch failures after switching to the Honeywell switches.  At the time, Bob postulated that the lack of decoupling loops in the wiring may have contributed.  I was not so sure, so I made no other changes other than replacing the switches.

  

 While not conclusive, I would say the root cause of failure was the loose riveted terminals on the Carling Switches.  The lack of decoupling loops in the wiring may have contributed, but it appears that a higher quality switch is an effective solution.

  

 I had two failures on the Strobe circuit, one on the Landing light circuit and one on the progressive-transfer Master Switch in the first 150 hours with the Carling Switches.

 

 So, if anyone thinks that this is just a characteristic of our OBAM aircraft being built with "substandard" components, look at this:

 

 =======================

 

 FAA Issues Airworthiness Bulletin For Cessna GA Aircraft

 Tue, 28 Jul '09

 

 SAIB Affects 100, 200, 300 Series Cessna Aircraft

 The FAA has issued a Special Airworthiness Information Bulletin (SAIB) to advise pilots and owners of an airworthiness concern on mandatory replacement intervals of Cessna Landing Light, Beacon Light, and Taxi Light switches on Cessna 100, 200, and 300 series airplanes, specified in Cessna service bulletins MEB09-3 and SEB09-6 dated May 11, 2009.

  

 Cessna 100, 200, and 300 series airplanes utilize switches in the Landing Light, Beacon Light, and Taxi Light circuits that have been reported failing in the field causing overheating and smoke in the cockpit. There have been reports of burned insulation on the wiring terminals to the switch. On at

  least one occasion, there was a small fire in the cockpit. The failure in these applications can be attributed to contact erosion leading to irregular arcing and eventual failure of the switch. The contact erosion has been shown to occur after approximately 4,000 cycles of operation.

  

 Cessna service bulletins SEB09-6 and MEB09-3, initial release, dated May 11, 2009, specify the following:

 

 .An inspection to determine time-in-service for the switches.

 .Replacement of switches that have been in service for four or more years with the month and year of the installation written on the new replacement switch.

 .The month and year of the initial installation written on switches that have been in service for less than four years.

 The FAA recommends that owners, operators, and maintenance technicians act on the above-referenced service bulletins within the next 400 hours of operation, 12 months, or the next annual inspection, whichever comes first.

  

 =======

 Vern Little

 Vx Aviation

 

 

 ---

nuckollsr

Joined: 24 Mar 2009
Posts: 95
Location: Medicine Lodge, KS

Posted: Wed Jul 29, 2009 7:24 am Post subject: Re: Switch Failures

"The failure in these applications can be attributed to contact erosion leading to irregular arcing and eventual failure of the switch. The contact erosion has been shown to occur after approximately 4,000 cycles of operation."



I'm away from my office for a couple of days. I'll have a more extensive response when I get back "to the hills".



It would be interesting/enlightening to see the failed switches. For all of the Carling failures I examined, there was no evidence of contact erosion. In fact, all failure examples displayed evidence of heating effects that began away from the contacts . . . most notably at the riveted joins for the fast-on tabs. It would also be interesting to know how the problem aircraft were flown. I've flown dozens of Cessna aircraft fitted with switches where the factory original switches were 40+ years old. I also recall testing the the lab at Cessna East (single engine) on the Carling rocker switches were tens of thousands of cycles were impressed on the switches before they were deemed suited to the task.



I suspect that root cause for this rash of failures is yet to be deduced and understood. Action taken by the regulators was predictable. Write an $AD$ that demands replacing a $2 switch with the one that's been re-labeled with Cessna's $Standard-Part$ number.



I don't know if any of the gray-beards are still working out there. I'll have to call around and see what I can discover.



Bob . . .

jlisler(at)windstream.net
Guest

Posted: Fri Jul 31, 2009 8:15 am Post subject: Switch Failures

Bob,



While on the subject of switches, what's up with the AD on Beechcraft 

switches? My local FBO has 3 or 4 Bonanzas and a couple of Barons in the 

shop to replace all the switches on the panels. They told me the switches 

were about $130 each (cost!!!!) plus several hours labor to install. I 

cannot imagine charging that much for a switch.



Jerry Isler

RV4 N455J

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jul 31, 2009 10:09 am Post subject: Switch Failures

At 11:13 AM 7/31/2009, you wrote:

 	  Quote: 	
		  

<jlisler(at)windstream.net>



Bob,



While on the subject of switches, what's up with the AD on 

Beechcraft switches? My local FBO has 3 or 4 Bonanzas and a couple 

of Barons in the shop to replace all the switches on the panels. 

They told me the switches were about $130 each (cost!!!!) plus 

several hours labor to install. I cannot imagine charging that much 

for a switch.


	


   Gee . . . ONLY $130? It has to be because the

   volume in sales is up. While I was still at HBC,

   I seem to recall a price of $175 each.

   The device in question is a breaker-switch . . .



http://aeroelectric.com/Pictures/Breakers/W31_3.jpg



   . . . where robustness of the braided copper jumper

   wire is not meeting design goals. If the "added

   insulator" is not present, jumper failure causes

   load current to flow through the contact-spreading

   spring. IF the switch is used in a high current

   application (prop de-ice, pitot heat) then the spring

   smokes and folks get upset.



   Problem is similar to the AD being discussed on the

   Cessna switches. The Bonanzas and Barons total about

   80,000 switches in the field. The Cessna situation

   is probably much larger.



   This is a great example of what happens when one

   discovers a failure to meet design goals in a

   legacy product with huge numbers. The only folks

   upset about it are the aircraft owners. The FBO

   can sympathize but he cannot do anything practical.

   Cessna and Beech can't do anything practical either.

   First, it's unlikely that they have anyone on their

   staff that truly understands root causes for

   the problems. Second, practical fixes require

   properly approved kits with staggering costs and

   time-to-market issues driven by bureaucracy and

   corporate policy/procedure albatrosses.



   So, what's the easy fix? AD the critters, spread

   the costs around the fleet owners. But make sure

   the work is accomplished only by qualified technicians

   at FBO standard rates.



   The type certificated light airplane market

   is sinking ever lower in the FAA/ISO tarpits.

   While at Cessna in 1965 or so, we broke 10,000

   airplanes per year production. It's never

   been that high since and the trends are going

   down.

        Bob . . .



         ---------------------------------------

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------

frank.hinde(at)hp.com
Guest

Posted: Fri Jul 31, 2009 10:24 am Post subject: Switch Failures

Buy one switch then search heavan and earth to find the supplier and buy direct from them..then hand them to the A&P..Got to be worth a shot..Gee!



Frank...Thankfully experimental! 



Bob,



While on the subject of switches, what's up with the AD on Beechcraft switches? My local FBO has 3 or 4 Bonanzas and a couple of Barons in the shop to replace all the switches on the panels. They told me the switches were about $130 each (cost!!!!) plus several hours labor to install. I cannot imagine charging that much for a switch.



Jerry Isler

RV4 N455J

dave.gribble(at)mchsi.com
Guest

Posted: Fri Jul 31, 2009 5:19 pm Post subject: Switch Failures

The cost isn't that high - I paid only $98-$105 each for my six switch / 

breakers.  Its the miracle of certified aviation.



BTW - there was a vendor at Oshkosh who claims that the new switches are 

also defective (with a somewhat different failure mode - the breakage of the 

braided wire inside).  He claimed to have "just yesterday" received a PMA 

for his replacement switch/breaker.   It was only $130.... taking orders but 

not yet available. 

---

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jul 31, 2009 5:57 pm Post subject: Switch Failures

At 08:08 PM 7/31/2009, you wrote:

 	  Quote: 	
		  

<dave.gribble(at)mchsi.com>



The cost isn't that high - I paid only $98-$105 each for my six 

switch / breakers.  Its the miracle of certified aviation.



BTW - there was a vendor at Oshkosh who claims that the new switches 

are also defective (with a somewhat different failure mode - the 

breakage of the braided wire inside).


	


   That was the ORIGINAL failure with a secondary event

   (smoking spring) caused by current flowing through

   the spring between the contact strut and the frame.



   The "FIX" didn't stop the wire from breaking, it only

   kept the secondary event from occurring. So instead

   of getting a broken wire followed by smoke, you only

   get a dead accessory. Now, I suppose the next shoe to

   drop will insist that some light or warning be included.

   Yeah, put a paragraph in the flight manual asking the

   pilot to keep an eye on the ammeter lest a broken wire

   sneak past without notice . . . but at least we don't

   put smoke in the cockpit.



 	  Quote: 	
		     He claimed to have "just yesterday" received a PMA for his 

 replacement switch/breaker.   It was only $130.... taking orders 

 but not yet available. 


	


   Do you have his contact data?

        Bob . . .



         ---------------------------------------

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------

dave.gribble(at)mchsi.com
Guest

Posted: Fri Jul 31, 2009 8:20 pm Post subject: Switch Failures

His handout reads:



"MAJOR PROBLEM!  If you install the NEW Beech Circuit Breaker for the AD, be 

prepared for smoke, sparks, or fire in the cockpit.



THE Braided Wire BREAKS..."



You can read the rest of it with photos here: 

http://www.williamsairpower.com/pdf/switches.pdf



Contact info as requested:

Daniel J. Williams

Williams Air Power

730 Lincoln Lake Ave Lowell MI 49331

616-897-5785

www.williamsairpower.com

BTW Bob - in all the recent thread about regular (non-breaker) toggle 

switches failing there was talk of Carling and Honeywell.... do you know 

whose parts B&C sells?  I want to buy the switches for my RV.



dave

---

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Aug 01, 2009 5:41 am Post subject: Switch Failures

At 11:17 PM 7/31/2009, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Dave Gribble" <dave.gribble(at)mchsi.com>



 His handout reads:



 "MAJOR PROBLEM!  If you install the NEW Beech Circuit Breaker for the AD, be prepared for smoke, sparks, or fire in the cockpit.



 THE Braided Wire BREAKS..."



 You can read the rest of it with photos here:  http://www.williamsairpower.com/pdf/switches.pdf

 	


   Good grief! A one page .pdf file of over 12 megabytes!

   Here's the meat of the text . . .



 The Braided Wire BREAKS

 This one was 90% failed when opened. ALL Beech

 and Tyco circuit breaker switches have the braided

 wire.



     Yes, that basic design has existed in this

   product since the early 60's. That series

   of breaker-switches has been manufactured

   in the hundreds of thousands with about

   80K used in Beech products and perhaps

   the same amount in some Cessna models.



   Commercially, that design has a market footprint

   probably in the millions.  Now, there is

   a fundamental flaw in the design for this

   product. You'll all no doubt recall numerous

   discussions about "gas-tight" for reliable

   connectivity and "support at the stress risers"

   for robustness. This is a common theme throughout

   the universe of wire connection. It was discussed

   at length in . . .



  http://aeroelectric.com/articles/terminal.pdf



   As you can see in this photo . . .



 [url=http://aeroelectric.com/Pictures/Breakers/W31_w_\'Failed\'_jumper_wires.jpg] http://aeroelectric.com/Pictures/Breakers/W31_w_%27Failed%27_jumper_wires.jpg[/url] 



   . . . the braid is SPOT WELDED to the

   forward corner of the frame. Yeah, let's hear

   it for gas-tight. But were is the support at the

   stress-risers for robustness? It isn't there.

   Now, in the photo above, the "failed" wires are

   some that I cut to see if I could detect a delta-R

   in the breaker's closed position for the purposes

   of detecting an impending failure. It wasn't possible

   with ordinary tools. However, when wires break in the

   fielded products, they fail right at the edge of

   the spotweld. Predictable.



 

  When the braided wire fails it either fails open or

 closed. If it fails open, the current then goes through

 the arm, through the spring and onto the load bar.



   The FAA used the word "shorted" in some of their

   descriptions of failure modes. I objected but

   the document was already published and in the

   field. It's a rare bureaucrat that will

   step up to do the right thing when caught with

   his pants down. I don't think there were EVER

   instances of shorting, only of broken wires

   that transferred the major current path to

   an uninsulated spring.

     

  By insulating the spring it solved this problem. However

 many Tyco circuit breaker switches have failed

 closed or shorted ( in all types of aircraft). When the

 braid breaks off and closes the buss input to the load

 bar, it renders the switch ineffective and uncontrolled

 electricity goes through that circuit. After that it is

 smoke, sparks, and ultimately fire unless God

 intervenes.



   A classic example of seizing on a few

   facts, a few off the wall assumptions,

   some mis-interpreted drivel from the 

   bureaucrats, an scare the pants off the

   uninformed by alluding to enhanced risk

   of joining their maker . . .

     



 What is needed is a circuit breaker switch that

 does not have a braided wire.

 Simplify the current path.



    Without a doubt, the new design is superior

    with regard to the elimination of the poorly

    implemented spot-welds for wire bonding. However,

    this product doesn't have the field history

    of the existing part. It's not known if 20

    years and 100,000 parts from now, some new

    AD won't be issued against this part as well.

    What we DO know is that the failures are rare,

    and relatively benign and is only a risk for

    the breakers above 10A continuous loads.



    If it were my airplane, I'd replace the pitot

    heat and prop heat switch breakers with the

    new design, leave the rest alone.



    Just like the guy who got an STC for replacing

    Piper's aluminum cables with copper cables

    and made a bundle selling holy-watered hunks

    of wire, this guy is going to make some bux

    selling a $30 device at a huge mark-up . . . 

    made possible because he was willing to run

    the traps with the folks who holy-watered

    his product.



    Hey, how about a "cash for breakers" program?

    Talk to the right folks in Congress and I'll

    bet we can soak our grandchildren for a

    few $millions$ to help this guy get well quicker

    and alleviate the need for prayers in the cockpit.



 

        Bob . . .



         ---------------------------------------

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------

     [quote][b]

lrsecaldwell(at)earthlink
Guest

Posted: Sat Aug 01, 2009 1:20 pm Post subject: Switch failures

Does anyone have a cross reference from B & C part numbers to Honeywell's part numbers?

  

 Roger

    [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Aug 01, 2009 5:02 pm Post subject: Switch failures

At 04:13 PM 8/1/2009, you wrote:

  	  Quote: 	
		   Does anyone have a cross reference from B & C part numbers to Honeywell's part numbers?

  	


   The last two digits of B&C's numbers carry over

   to the Honeywell part numbers shown in 



  http://www.aeroelectric.com/Mfgr_Data/Switches/Microswitch/Microswitch_TL-Series.pdf 



   For example, the S700-2-3 is a Honeywell 2TL1-3

                         | |                |    |

                         | |                |    \--Function

                         | |                \-- # of poles

                         | \---- Function

                         \----- # of poles



 

        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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