AD/Cessna 400/113 Avionics Bus Circuit Breaker Switch (Cth)

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.001(1) of CASR 1998.  The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Cessna 400 Series Aeroplanes

AD/CESSNA 400/113 Avionics Bus Circuit Breaker Switch 13/2005

Applicability:	Cessna Model 400 aeroplanes as follows equipped with an avionics bus circuit breaker switch, part number (P/N) CM3589-50, 593-250-101, 593-250-102, W31-X2M5A-50 or W31-X1000-50:
Model	Serial Numbers
401	655 and 401-0001 through 401-0322
401A	655 and 401A0001 through 401A0132
401B	401B0001 through 401B0221
402	402-0001 through 402-0322
402A	402A0001 through 402A0129
402B	402B0001 through 402B0122, 402B0201 through 402B0249, 402B0301 through 402B0455, 402B0501 through 402B0640, 402B0801 through 402B0935, 402B1001 through 402B1100, 402B1201 through 402B1250 and 402B1301 through 402B1384
402C	689, 402C0001 through 402C0125, 402C0201 through 402C0355, 402C0401 through 402C0528, 402C0601 through 402C0653, 402C0801 through 402C0807 and 402C0808 through 402C1020
404	682, 404-0001 through 404-0136, 404-0201 through 404-0246, 404-0401 through 404-0460, 404-0601 through 404-0695 and 404-0801 through 404-0859
411	642 and 411-0001 through 411-0250
411A	411-0251 through 411-0300
414	667, 414-0001 through 414-0099, 414-0151 through 414-0175, 414-0251 through 414-0280, 414-0351 through 414-0437, 414-0451 through 414-0550, 414-0601 through 414-0655, 414-0801 through 414-0855 and 414-0901 through 414-0965

414A	414A0001 through 414A0121, 414A0201 through 414A0340, 414A0401 through 414A0535, 414A0601 through 414A0680, 414A0801 through 414A0858 and 414A1001 through 414A1212
421	693 and 421-0001 through 421-0200
421A	421A0001 through 421A0158
421B	421B0001 through 421B0056, 421B0101 through 421B0147, 421B0201 through 421B0275, 421B0301 through 421B0486, 421B0501 through 421B0665 and 421B0801 through 421B0970
421C	421C0001 through 421C0171, 421C0201 through 421C0350, 421C0401 through 421C0525, 421C0601 through 421C0715, 421C0801 through 421C0910, 421C1001 through 421C1115, 421C1201 through 421C1257, 421C1401 through 421C1413 and 421C1801 through 421C1807
425	425-0001 through 425-0236
441	698 and 441-0001 through 441-0362
Requirement:	1.    Inspect the avionics bus circuit breaker switch to determine the P/N and date code in accordance with the following:
a.     For Models 425 and 441 aeroplanes - Cessna Conquest Service Bulletin (SB) CQB05-2, dated 21 February 2005 and the applicable maintenance manual.
b.    For all other affected aeroplane models - Cessna Multi-engine SB MEB05-1 dated21 February 2005 and the applicable maintenance manual.
If the P/N is CM3589-50, 593-250-101, 593-250-102, W31-X2M5A-50 or W31-X1000-50 and the date code is 0434 or later; then no further action is required.
2.    If the P/N is CM3589-50, 593-250-101, 593-250-102, W31-X2M5A-50 or W31-X1000-50 and there is no date code, replace the avionics bus circuit breaker switch with a P/N CM3589-50 that has a date code of 0434 or later in accordance with the following:
a.     For Models 425 and 441 aeroplanes - SB CQB05-2, dated 21 February 2005 and the applicable maintenance manual.
b.    For all other affected aeroplane models - SB MEB05-1 dated21 February 2005 and the applicable maintenance manual.

3.    If the P/N is CM3589-50, 593-250-101, 593-250-102, W31-X2M5A-50 or W31-X1000-50 and the date code is earlier than 0434, the part has a safe life limit of 1,000 hours time in service (TIS) and must be replaced within the 1,000 hour time limit with a P/N CM3589-50 that has a date code of 0434 or later in accordance with the following:
a.     For Models 425 and 441 aeroplanes - SB CQB05-2, dated 21 February 2005 and the applicable maintenance manual.
b.    For all other affected aeroplane models - SB MEB05-1 dated21 February 2005 and the applicable maintenance manual.
4.    Avionics bus circuit breaker switches P/N CM3589-50, 593-250-101, 593-250-102, W31-X2M5A-50 or W31-X1000-50 that do not have a date code or have a date code earlier than 0434 may not be installed as a replacement spare.
Later revisions of the above SB(s), approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2005-20-25, are considered acceptable for compliance with the equivalent Requirements of this Directive.
Note:  FAA AD 2005-20-25 Amdt 39-14321 refers.
Compliance:	For Requirement 1 - Within the next 200 hours TIS, the next 12 months or at the next scheduled inspection, after the effective date of this Directive, whichever occurs first.
For Requirement 2 - Before further flight after the Requirement 1 inspection.
For Requirement 3 - Within the 1,000-hour TIS safe life limit.
For Requirement 4 - As of the effective date of this Directive.
This Airworthiness Directive becomes effective on 22 December 2005.
Background:	The FAA has received failure reports of certain Tyco Electronics circuit breaker switches installed on the master avionics bus of Cessna Model 400 aeroplanes.
Analysis of the circuit breaker switch revealed the copper braid inside the switch had frayed.  Continued use causes an internal short.  The internal short could result in the internal switch components or external wiring melting because it is no longer protected by the circuit breaker.  The affected circuit breaker switches have a date code earlier than 0434 or do not have a date code on them.  The date code consists of four digits, the first two represent the year and the last two represent the week of the year the part was made.

Failure of these circuit breaker switches causes smoke and a burning smell in the cockpit.  If not prevented failure could lead to reduced ability to control the aeroplane.  This Directive requires the inspection of the circuit breaker switches and, if necessary, their replacement.

James Coyne
Delegate of the Civil Aviation Safety Authority

10 November 2005