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TVS Failures

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bakerocb

Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

Posted: Wed Feb 27, 2008 10:52 am Post subject: TVS Failures

2/27/2008



Hello Fellow Builders, The certificated airplane community has been hit with 

a series of TVS failures. Several different manufacturer's airplanes have 

been affected.



Copied below is just one of the SAIB's that the FAA has issued on this 

subject.



If your project includes TVS' you may want to further investigate -- the 

same TVS manufacturer seems to be involved in all failures.



'OC' Says: "The best investment we can make is the effort to gather and 

understand knowledge."



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



FAA

Aircraft Certification Service

SPECIAL AIRWORTHINESS

INFORMATION BULLETIN

SUBJ: Electrical Power

SAIB: CE-08-12

Date: February 27, 2008

This is information only. Recommendations aren't mandatory.

Introduction

This Special Airworthiness Information Bulletin (SAIB) advises you of an 

airworthiness concern on

Cirrus Design Corporation (CDC) Models SR20 and SR22 airplanes where 

possible failure of a

transient voltage suppressor (TVS) may result in an increase in workload for 

the pilot.

This airworthiness action has been taken after consideration of the 

responses from CDC as well as

airplane owners/ operators through relevant associations and type clubs, 

using the procedures found

in the Small Airplane Directorate Airworthiness Directives Manual Supplement 

(Airworthiness

Concern Process Guide).

At this time, this airworthiness concern is not considered an unsafe 

condition that would warrant an

airworthiness directive (AD) action under Title 14 of the Code of Federal 

Regulations (14 CFR part

39).

Background

CDC notified the Federal Aviation Administration of the failure of a TVS on 

a CDC Model SR22

airplane, which resulted in loss of NAV/COM1 functionality and some smoke 

and fumes within the

cockpit. Since that time, 14 other TVS's have failed on CDC airplanes in the 

field.

Other airplanes equipped with TVSs from the same manufacturer have recently 

experienced failures.

Our findings thus far, show that the electronic component itself is the 

primary suspect for a cause of

the failures. To date, no specific reason has been positively identified for 

the failures although several

companies are working on the problem.

As previously mentioned, no other functionality other than the NAV/COMM 1 

has been lost on a

CDC airplane. All CDC airplanes have redundancy with a NAV/COMM 2 available. 

Also, in all

known occurrences of TVS failures, the smoke and fumes have been noted to be 

of short duration and

not sufficient to impede the pilots visibility, or toxic such that the pilot's 

ability to operate the

airplane is impaired.

Recommendations

We recommend that all CDC airplane owner/operators thoroughly read Cirrus 

service advisory SA

07-17, dated September 11, 2007. The service advisory provides good 

information on what to expect

should a TVS failure occur and what actions should be taken by the pilot.

For Further Information Contact

Wesley Rouse, Aerospace Engineer, FAA Chicago Aircraft Certification, 2300 

E. Devon, Des

Plaines, IL 60018; phone: (847) 294-8113; email: wess.rouse(at)faa.gov

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nuckolls.bob(at)cox.net
Guest

Posted: Wed Feb 27, 2008 7:09 pm Post subject: TVS Failures

At 04:49 PM 2/27/2008 -0800, you wrote:



 	  Quote: 	
		  

<henador_titzoff(at)yahoo.com>



Bob,



Without calling the FAA, you wouldn't happen to know how to get the failed 

TVS vendor's name, would you?  The CDC website of course has no bad news 

in it. I'm sure the vendor isn't advertising it, either.



Thanks,

Henador Titzof


	


  It's just a guess at this stage of the game but

  I'll bet that the "problem" has more to do with

  how the devices were incorporated into the system

  along with sizes selected than it has to do with

  quality issues for the manufacturer of the devices.



  These are legacy products now . . . i.e. 20+ years

  old. The manufacturer has made millions of these things

  for industrial and consumer applications and is now

  probably lamenting the fact that some "kind soul"

  included a part of their manufacture on the BOM

  of a T/C aircraft.



  I won't endeavor to sell to T/C aviation and it

  has nothing to do with my willingness or ability

  to deliver product that meets the data sheets.

  It's cases like this where a hand full of jelly-bean

  parts are named participants in a "official

  investigation". NOBODY wins in these things, even

  if the TVS manufacturer is found blameless.



  I'll see if I can find out more details. I'm

  involved in some development programs for the

  OEM and have some friendly contacts. In the mean

  time, don't get excited about purging your

  airframe of "bad parts" until we know the

  physics of the matter.



  Oh yeah, I'll mention in passing that my drawings

  seldom if ever show a TVS as part of ship's

  wiring. These things belong inside an appliance

  designed and tested to meed DO-160 cert levels.

  Once the appliances are pronounced golden, there's

  little if any need for the wire-slingers to add

  them to the system.

  Bob . . .

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