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W31 switch/breaker fiasco

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nuckolls.bob(at)cox.net
Guest

Posted: Wed Jul 16, 2008 2:12 pm Post subject: W31 switch/breaker fiasco

Just got a call from folks at the American Bonanza Society

and will be meeting them for lunch tomorrow. From the

short conversations I had with them today, I perceive

them to be REALLY sharp. We're going to see if we can

craft an "AMOC", alternative method of compliance for

that "rip 'em all out and replace them" approach to

the breaker failures on the Beech products.



I've not heard whether or not similar AD's are in the

works for other OEMs. The W31 is remarked and fitted with

stylized handles for a number of folks including Cessna.

I'll know more tomorrow.



One of the most promising possibilities is to conduct

a 4-wire ohmmeter test on a partially failed breaker

to see if we can detect broken strands at some time

before the last strands break (or become vulnerable

to over-heating due to current). It occurs

to me that a voltage drop measurement in the airplane

may be sufficiently fine-grained to detect an impending

failure . . . the prop de-ice heaters certainly provide

sufficient "bias current" for a meaningful measurement . . .

more than my little 4-wire adapter does.



Shucks, who would have thought I might do more for

Beech from outside the fence than I was able to from

inside? This is going to be an INTERESTING science

project!

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

mprather(at)spro.net
Guest

Posted: Wed Jul 16, 2008 3:26 pm Post subject: W31 switch/breaker fiasco

Hey Bob,



It sounds like the AMOC might involve annual or hours checks - a breaker

that's okay this year might not be okay after another year or 500 hours? 

Or, if a breaker's good after 20 years, it won't ever go bad?  When's the

crossover as far as cost - inspect again vs. replace?

Regards,



Matt-



 	  Quote: 	
		   

 <nuckolls.bob(at)cox.net>



 Just got a call from folks at the American Bonanza Society

 and will be meeting them for lunch tomorrow. From the

 short conversations I had with them today, I perceive

 them to be REALLY sharp. We're going to see if we can

 craft an "AMOC", alternative method of compliance for

 that "rip 'em all out and replace them" approach to

 the breaker failures on the Beech products.



 I've not heard whether or not similar AD's are in the

 works for other OEMs. The W31 is remarked and fitted with

 stylized handles for a number of folks including Cessna.

 I'll know more tomorrow.



 One of the most promising possibilities is to conduct

 a 4-wire ohmmeter test on a partially failed breaker

 to see if we can detect broken strands at some time

 before the last strands break (or become vulnerable

 to over-heating due to current). It occurs

 to me that a voltage drop measurement in the airplane

 may be sufficiently fine-grained to detect an impending

 failure . . . the prop de-ice heaters certainly provide

 sufficient "bias current" for a meaningful measurement . . .

 more than my little 4-wire adapter does.



 Shucks, who would have thought I might do more for

 Beech from outside the fence than I was able to from

 inside? This is going to be an INTERESTING science

 project!

         Bob . . .



         ----------------------------------------)

         ( . . .  a long habit of not thinking   )

         ( a thing wrong, gives it a superficial )

         ( appearance of being right . . .       )

         (                                       )

         (                  -Thomas Paine 1776-  )

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

rjquillin

Joined: 13 May 2007
Posts: 123
Location: KSEE

Posted: Wed Jul 16, 2008 5:08 pm Post subject: W31 switch/breaker fiasco

Plus AMOC's are A/C specific.  That is each and every aircraft will 

have to submit and obtain approval for the specific A/C (by S/N and 

or tail number) into which it will be installed prior to implementing 

the "fix".  Not at all like a 337 that may, depending on the local 

FSDO, be used on other similar A/C with a simple sign-off.



Doable, but what a PITA.



Ron Q.



At 16:22 7/16/2008, you wrote:

 	  Quote: 	
		  It sounds like the AMOC might involve annual or hours checks - a breaker

that's okay this year might not be okay after another year or 500 hours?

Or, if a breaker's good after 20 years, it won't ever go bad?  When's the

crossover as far as cost - inspect again vs. replace?

Regards,



Matt-

mprather(at)spro.net
Guest

Posted: Wed Jul 16, 2008 6:16 pm Post subject: W31 switch/breaker fiasco

I didn't realize that about AMOC's.  Even so, a type club like for

Bonanzas would likely be able to help streamline the process.

Matt-

 	  Quote: 	

 Plus AMOC's are A/C specific.  That is each and every aircraft will

 have to submit and obtain approval for the specific A/C (by S/N and

 or tail number) into which it will be installed prior to implementing

 the "fix".  Not at all like a 337 that may, depending on the local

 FSDO, be used on other similar A/C with a simple sign-off.

 Doable, but what a PITA.

 Ron Q.

 At 16:22 7/16/2008, you wrote:

>It sounds like the AMOC might involve annual or hours checks - a breaker

>that's okay this year might not be okay after another year or 500 hours?

>Or, if a breaker's good after 20 years, it won't ever go bad?  When's the

>crossover as far as cost - inspect again vs. replace?

>Regards,

>

>Matt-

nuckolls.bob(at)cox.net
Guest

Posted: Thu Jul 17, 2008 5:54 am Post subject: W31 switch/breaker fiasco

At 05:22 PM 7/16/2008 -0600, you wrote:

 	  Quote: 	
		  



Hey Bob,



It sounds like the AMOC might involve annual or hours checks - a breaker

that's okay this year might not be okay after another year or 500 hours?

Or, if a breaker's good after 20 years, it won't ever go bad?  When's the

crossover as far as cost - inspect again vs. replace?


	


   Yeah, the task is to be a teacher first. Study the science

   and get folks who control the situation to understand.



   Naw, I take that back. They don't even need to understand

   the significance of their earlier decisions as long as

   someone else takes responsibility for the replacement

   procedure . . . at least the first guys can say, "I

   did my job".



   It's certainly a time-in-service issue. I'm hoping I

   can craft an in-situ test that discovers the majority

   of broken strands before the conductor fails

   completely. This would allow detection and replacement

   hundreds of flying hours before the failure.



   Bob . . .

nuckolls.bob(at)cox.net
Guest

Posted: Thu Jul 17, 2008 5:56 am Post subject: W31 switch/breaker fiasco

At 06:04 PM 7/16/2008 -0700, you wrote:

 	  Quote: 	
		  



Plus AMOC's are A/C specific.  That is each and every aircraft will have 

to submit and obtain approval for the specific A/C (by S/N and or tail 

number) into which it will be installed prior to implementing the 

"fix".  Not at all like a 337 that may, depending on the local FSDO, be 

used on other similar A/C with a simple sign-off.



Doable, but what a PITA.


	


   Yes . . . what we should really strive for is an amended

   AD that calls out the new procedure. They HAVE done such

   things in the past. Recall the diode across the starter

   switch contacts that did nothing. That AD was amended to

   move the diode to the coil.



   Bob . . .

Speedy11(at)aol.com
Guest

Posted: Thu Jul 17, 2008 9:13 am Post subject: W31 switch/breaker fiasco

Bob,

 Apparently I'm ignorant of the problem you reference.

 Have the Bonanza drivers been having problems with W31  switch-breakers?

 Stan Sutterfield

  

  	  Quote: 	
		  Just got    a call from folks at the American Bonanza Society

and will be meeting them    for lunch tomorrow. From the

short conversations I had with them today, I    perceive

them to be REALLY sharp. We're going to see if we can

craft an    "AMOC", alternative method of compliance for

that "rip 'em all out and    replace them" approach to

the breaker failures on the Beech    products.



I've not heard whether or not similar AD's are in    the

works for other OEMs. The W31 is remarked and fitted with

stylized    handles for a number of folks including Cessna. 	


 

  



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  [quote][b]

BobsV35B(at)aol.com
Guest

Posted: Thu Jul 17, 2008 9:44 am Post subject: W31 switch/breaker fiasco

Good Afternoon Stan,

  

 That depends on what you mean!

  

 We Bonanza and the Baron pilots have had almost no problems at all with any  of the W31 series switches, but the FAA has perceived (falsely most of us  believe) that there is a problem with a very few of the switches. 

  

 It is not a problem that occurs due to use, but one that is a result of  thousands of hours of vibration. When (IF) the failure does occur, an  electrical load can be shunted to ground which will cause a bit of smoke. If  something ignitable is located in the way, I suppose a fire could ensue.

  

 Most of us feel that the AD that has been issued by the FAA is not at all  needed. A simple service letter outlining the potential problem should be more  than sufficient. I haven't talked to Bob N. about it, but from what he has  written, I think he agrees with the assessment made by most of us who are  affected by the recently issued AD..

  

 Any help at all?

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

628 West  86th Street

Downers Grove, IL 60516

630 985-8502 

Stearman  N3977A

Brookeridge Air Park LL22

  

  In a message dated 7/17/2008 12:19:03 P.M. Central Daylight Time,  Speedy11(at)aol.com writes:

  	  Quote: 	
		     Bob,

   Apparently I'm ignorant of the problem you reference.

   Have the Bonanza drivers been having problems with W31    switch-breakers?

   Stan  Sutterfield

	






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retasker(at)optonline.net
Guest

Posted: Thu Jul 17, 2008 2:07 pm Post subject: W31 switch/breaker fiasco

Actually, if it fails it does NOT short anything to ground, although 

that is what the FAA dissertation says.  What happens if the device 

fails is that the current normally carried by large copper wires within 

the breaker takes an alternate, higher resistance path to wherever it 

would normally go.  For relatively lower currents this really does 

pretty much nothing.  For high current loads, the parts in the path it 

goes through heat up significantly and may generate some smoke - easily 

remedied by switching the breaker off and then replacing it (on the ground).



While this is not to be construed to be a trivial problem, it is a 

problem only if the part fails and then only in a few applications.  

What is needed, rather than a wholesale replacement of all the 

potentially affected breakers in all the affected airplanes is a simple 

way to test them - which it seems that Bob is working on.



Dick Tasker



BobsV35B(at)aol.com wrote:

 	  Quote: 	
		   Good Afternoon Stan,

  

 That depends on what you mean!

  

 We Bonanza and the Baron pilots have had almost no problems at all 

 with any of the W31 series switches, but the FAA has perceived 

 (falsely most of us believe) that there is a problem with a very few 

 of the switches.

  

 It is not a problem that occurs due to use, but one that is a result 

 of thousands of hours of vibration. When (IF) the failure does occur, 

 an electrical load can be shunted to ground which will cause a bit of 

 smoke. If something ignitable is located in the way, I suppose a fire 

 could ensue.

  

 Most of us feel that the AD that has been issued by the FAA is not at 

 all needed. A simple service letter outlining the potential problem 

 should be more than sufficient. I haven't talked to Bob N. about it, 

 but from what he has written, I think he agrees with the assessment 

 made by most of us who are affected by the recently issued AD..

  

 Any help at all?

  

 Happy Skies,



 Old Bob

 AKA

 Bob Siegfried

BobsV35B(at)aol.com
Guest

Posted: Thu Jul 17, 2008 6:27 pm Post subject: W31 switch/breaker fiasco

Good Evening Dick.

  

 I have no argument with your explanation other than it is my understanding  that it is possible that once the little spring has been fried, there will be no  way to positively shut off the power. 

  

 I doubt if either you or I know for sure, but it has been explained to me  that such is a possibility.  

  

 As you state, it is NOT a problem of the primary current carrying device  getting grounded. The trouble comes after the wire designed to carry the current  within the switch gets old, corroded, and weak which causes it to fall off it's  contacts. Then, when the switch is activated, the current travels through the  switch actuation spring and that little spring is what fails. Chances are  that no real damage will occur because the spring will fail long before very  much current is able to be run through it, but there is the possibility that the  pilot will not be able to deactivate the circuit by any method short of turning  off the master switch.

  

 In any case, I think we can all agree that the FAA has once again fixed a  problem that is not at all likely to occur.

  

 Chances are that the invasion of the wiring loom on the subject aircraft  will cause more problems than would the very unlikely occurrence of a failure of  the switch in question. 

  

 What a shame!

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

628 West  86th Street

Downers Grove, IL 60516

630 985-8502 

Stearman  N3977A

Brookeridge Air Park LL22

  

  In a message dated 7/17/2008 5:09:21 P.M. Central Daylight Time,  retasker(at)optonline.net writes:

  	  Quote: 	
		  Actually, if it fails it does NOT short anything to ground, although    

that is what the FAA dissertation says.  What happens if the device    

fails is that the current normally carried by large copper wires within    

the breaker takes an alternate, higher resistance path to wherever it    

would normally go.  For relatively lower currents this really does    

pretty much nothing.  For high current loads, the parts in the path    it 

goes through heat up significantly and may generate some smoke - easily    

remedied by switching the breaker off and then replacing it (on the    ground).

	






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nuckolls.bob(at)cox.net
Guest

Posted: Fri Jul 18, 2008 7:30 am Post subject: W31 switch/breaker fiasco

At 06:02 PM 7/17/2008 -0400, you wrote:

 	  Quote: 	
		  

<retasker(at)optonline.net>



Actually, if it fails it does NOT short anything to ground, although that 

is what the FAA dissertation says.  What happens if the device fails is 

that the current normally carried by large copper wires within the breaker 

takes an alternate, higher resistance path to wherever it would normally 

go.  For relatively lower currents this really does pretty much 

nothing.  For high current loads, the parts in the path it goes through 

heat up significantly and may generate some smoke - easily remedied by 

switching the breaker off and then replacing it (on the ground).



While this is not to be construed to be a trivial problem, it is a problem 

only if the part fails and then only in a few applications.

What is needed, rather than a wholesale replacement of all the potentially 

affected breakers in all the affected airplanes is a simple way to test 

them - which it seems that Bob is working on.



Dick Tasker



BobsV35B(at)aol.com wrote:

>Good Afternoon Stan,

>

>That depends on what you mean!

>

>We Bonanza and the Baron pilots have had almost no problems at all with 

>any of the W31 series switches, but the FAA has perceived (falsely most 

>of us believe) that there is a problem with a very few of the switches.

>

>It is not a problem that occurs due to use, but one that is a result of 

>thousands of hours of vibration. When (IF) the failure does occur, an 

>electrical load can be shunted to ground which will cause a bit of smoke. 

>If something ignitable is located in the way, I suppose a fire could ensue.

>

>Most of us feel that the AD that has been issued by the FAA is not at all 

>needed. A simple service letter outlining the potential problem should be 

>more than sufficient. I haven't talked to Bob N. about it, but from what 

>he has written, I think he agrees with the assessment made by most of us 

>who are affected by the recently issued AD..


	


     Correct. I'm also discovering that this situation has

     deeper roots in political and regulatory bureaucracy

     than it does in science and safety. But the AD is what

     it is and once issued, it's not going to go away.



     I've not been able to look at real failed parts. We're

     still trying to do that. If one considers the internal

     construction of this device . . .



http://aeroelectric.com/Pictures/Breakers/W31_1.jpg



     and . . .



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



     we see that a current path through the closed switch

     comes in the top terminal, through closed contacts,

     through the soft-copper jumper fabricated from

     a bizillion strands of copper cat hair, around

     the corner of the frame to the anchor point of

     a bi-metal strut (heater for circuit breaker),

     and through another soft-copper jumper out to

     the lower terminal.



     The bottom jumper is needed to allow the strut

     move away from the trip latch as the part

     flexes due to heating under electrical load.



     The upper jumper gets flexed each time the switch

     operates. This arrangement has been laboratory

     tested many times and found suitable for use

     in aircraft . . . but is an excellent example

     of how laboratory testing CAN overlook (or

     simply cannot duplicate ALL) effects in the field

     not the least of which are subtle levels of

     vibration in normal service over LONG periods

     of time.



     In the article on wire joining as it relates

     to terminals . . .



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



     we considered the effects of mashing a collection

     of fine copper strands (fine for resistance to

     breaking due to flexing along the run) into essentially

     solid conductors at the attach point. This effect

     is a constant whether crimped, soldered or spot

     welded.



     The simple-idea here is that when stranded

     wire becomes solid at the electrical joint,

     there are stress-risers at the transition

     from joint-to-strands. If the wire is going

     to break due to flexing (vibration is micro-

     flexing), it will break at the transition.

     The obvious and elegant solution is SUPPORT to the wire

     immediately adjacent to the transition

     zone. Hence the DUAL crimp of a PIDG termnal,

     one for the connection, the second for

     support that prevents flexing at the transition.



     Take this idea back to the W31 breaker and we

     see that where the soft copper jumpers join

     struts and frames, there is a spot weld but

     NO SUPPORT.



     Magnitude of problem? Obviously no big deal in

     the lab . . . and in reality, no big deal in the

     airplanes either. None-the-less, a very few of these

     switches (compared to over 100,000 parts in service

     for 20+ years) have failed.



     Now, when the jumper finally fails completely, the

     ALTERNATE path for current is through the spring

     over the pin in the upper left corner of the pictures.

     In the photos, you see the UPGRADED design that includes

     a fiberglas sheet that insulates the spring from the

     frame. The jumper is still going to fail . . . but

     the result is a passive failure that simply causes

     the downstream device to stop functioning.



     Before the upgrade, current through the spring causes

     it to warm up. In the smaller circuits (5 and 10A

     switches) one would probably never be aware of the

     failure. On the larger circuits (30A prop deice) the

     spring heats up like the coils in your toaster and

     causes the adjacent plastic of the case to char and

     put out some smoke.



     The really interesting thing about the AD is that it

     seems to be reacting to the smoke . . . and not to

     the specific failure and subsequent situation that

     is presented to the pilot because that particular system

     isn't working. This is especially interesting in view

     of the fact that failure of a 30A de-ice breaker is

     a whole lot more tense situation than loss of the 10A

     nav lights! But when it comes to smoke, the rules are

     really hard-over. It matters not that the failure will

     not generate a propagating combustion event. I.e., no

     fire. This idea is not without foundation in the study

     of human factors. From the whole population of airplane

     drivers, how many are likely to become !(at)#$(at)#-for-brains

     pilots when presented with smoke in the cockpit? The

     number is small . . . but no doubt significant.

     So the result of compliance with the AD doesn't raise

     the relative reliability of the overall system, the

     failure rate of breaker-switches will remain the same.

     it only  avoids the potential for panic driven accident

     due to smoke.



     I've ordered switches and intend to explore ways that

     an impending failure might be spotted without removing

     the breaker from the airplane. Certainly failed

     devices in the lower current ratings can be spotted too.

     The road to Nirvana does not take us down the path

     of getting the AD rescinded. These are carved in granite

     and simply don't go away. However, wording in the AD

     does leave a door open for alternate method of compliance

     which is the goal of the moment.



     Bob . . .

Speedy11(at)aol.com
Guest

Posted: Fri Jul 18, 2008 1:55 pm Post subject: W31 switch/breaker fiasco

 	  Quote: 	
		  Any help    at all? 	


 

 Yes.  Thanks Old Bob!

  

 Stan

 Do not archive



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  [quote][b]

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