Circuit breaker switches

[Bruce Fenstermacher]

I have recently been approached by an owner who is horrified to learn that his buddy's Bonanza is subject to an expensive AD note which condemns virtually every switch/circuit breaker in the airplane.

George could you say what model of circuit breaker switch has problems and what the problem is?

[GAHorn]

The problem is of faulty design/mat'ls which lead to overheating and possible fire.

Excerpts from the AD:

AD 2008-13-17 Hawker Beechcraft Corporation (Type Certificates No. 3A15, No. 3A16, No.
A23CE, and No. A30CE previously held by Raytheon Aircraft Company) and Raytheon
Aircraft Company: Amendment 39-15580; Docket No. FAA-2007-28434; Directorate Identifier
2007-CE-053-AD.
Effective Date
(a) This AD becomes effective on August 6, 2008.
Affected ADs
(b) None.
Applicability
(c) This AD applies to the following airplane models and serial numbers that have a part number
(P/N) 35-380132-1 through 35-380132-53 circuit breaker toggle switch installed and are certificated
in any category:

Cost to comply:
From $2,001,885 to replace
one circuit breaker toggle
switch per affected airplane
up to $30,028,275 to replace
15 circuit breaker toggle
switches per airplane for the entire affected fleet.

(This estimate is based upon the official Beech price of $105 per switch and 1 hr labor at $80/hr required for each switch. Most airplane have about 15 such switches and would incur a cost of $185 per switch. I replaced my Baron's switches just for preventive reasons 10 years ago with Potter and Brumfelds for about $25 each. It took all weekend to do the dozen or so while upside down and ticked-off that I'd ever begun the job. It was hard work.)

The switches actual manufacturer and OEM PN or model are not mentioned. I do not believe they are any of the "Potter and Brumfeld" types but I have not positively confirmed that yet.

[Bruce Fenstermacher]

It would be nice to know it's not a Potter and Brumfeld type which is what I used to replace my original circuit breakers after one of them got so hot it melted solder on to my foot while commuting to work one day several years ago.

[GAHorn]

Garnered from web research:

The AD does indeed apply to certain Potter and Brumfeld (Tyco) toggle circuit breakers that have an UN-insulated wire internally such as this:

W31_1barewire.jpg

1. The old Beech TCB is provided by Tyco to Beech and isn't available directly from Tyco distributors. Tyco does not consider it to be obsolete, at least not yet. That old Beech TCB is Tyco part number W31-X1005-xx. (The last two digits "xx" represent the Amp rating.)

2. The new Beech part is provided by Tyco to Beech and isn't available directly from Tyco distributors. The Tyco part number is W31-X1017-xx. It includes the additional internal insulation that is described in the FAA AD.

3. The Tyco part number W31-X2M1G-xx, which is available from several distributors including Allied Electronics for less than $25, Newark Electronics, Mouser, and Aircraft Spruce, does include the additional internal insulation as does the W31-X1017-xx part. However, the toggle handle shape and color is different from the Beech W31-X1017-xx part. Both the W31-X1017-xx part from Beech and the Tyco W31-X2M1G-xx have the amp rating stamped into the end of the toggle.

Here's an external view of the complete C.B. and how the individual part number is usually stamped upon the side:

W31 affected.JPG

The GOOD NEWS is that if you acquired your C.B. from a supplier other than Beech, it's highly unlikely to be affected since the affected breakers were not distributed to other vendors than Beech. To be absolutely certain, confirm the PN on the side of the switch.