[Federal Register Volume 59, Number 140 (Friday, July 22, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-17859]


[[Page Unknown]]

[Federal Register: July 22, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 93-NM-19-AD]

 

Airworthiness Directives; Cessna Citation Model 500/501, 550/551, 
S550, 552, and 560 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Proposed rule; withdrawal.

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SUMMARY: This action withdraws a notice of proposed rulemaking (NPRM) 
that proposed a new airworthiness directive (AD), applicable to certain 
Cessna Citation Model 500/501, 550/551, S550, 552, and 560 series 
airplanes. That action would have required modification of the landing 
light electrical circuit to eliminate failures of the left and right 
landing light switches due to heavy current at the switch contacts. 
Since the issuance of the NPRM, the Federal Aviation Administration 
(FAA) has received additional data that confirm that failure of the 
subject switches does not pose an unsafe condition. Accordingly, the 
proposed rule is withdrawn.

FOR FURTHER INFORMATION CONTACT: C. Dale Bleakney, Aerospace Engineer, 
Systems and Equipment Branch, ACE-130W, FAA, Wichita Aircraft 
Certification Office (ACO), 1801 Airport Road, room 100, Mid-Continent 
Airport, Wichita, Kansas 67209; telephone (316) 946-4135; fax (316) 
946-4407.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to add a new airworthiness 
directive (AD), applicable to certain Cessna Citation Model 500/501, 
550/551, S550, 552, and 560 series airplanes, was published in the 
Federal Register on April 12, 1993 (58 FR 19069). That action was 
prompted by a report of failures of the left and right landing light 
switches due to heavy current at the switch contacts.
    The proposed rule would have required modification of the landing 
light electrical circuit. The intent of the modification was to 
preclude the possibility of failure of the landing light switches, 
which could lead to smoke and an electrical fire in the cockpit.
    Since the issuance of that NPRM, the FAA has received additional 
data gathered from an analysis that was conducted of the switch failure 
scenarios and the landing light switch design itself. These data 
indicate that the switch can adequately carry the current associated 
with either incandescent or halogen landing light installations. 
Apparently, the landing light switches that were involved in the 
reported incidents were of poor quality and were produced in only a 
small limited batch. The failure scenario analysis indicates that the 
switches shorted internally, allowing an odor and a trace of smoke to 
be released in the cockpit. In each case, however, the amount of smoke 
that was produced neither created a hazard nor interfered in any way 
with the safe operation of the aircraft. Further, contrary to what was 
previously reported, no fire occurred during any of the incidents as a 
result of the switch failure; the only identified discrepancy in some 
of the incidents was the discoloration of the switch cases.
    Additionally, further investigation of one of the reported 
incidents revealed that a wire connected to one of the failed switches 
had discolored due to overheating caused by an undersized wire splice. 
(The undersized wire splice may have been installed as a result of 
questionable maintenance.) This parictular problem is considered to be 
an isolated incident and independent of the switch problem.
    There have been no further failures of these switches since the 
original incidents that were reported (in 1992). As the limited number 
of suspect switches have appeared to have been purged from aircraft 
service by attrition, no recent failures have occurred. In addition, 
the FAA has not received any recent Malfunction or Defect Reports 
concerning these switches. This reduction in such reports supports the 
premise that poor quality switches are no longer found in the 
operators' inventories.
    Based on the recent analysis data and other evidence presented, the 
FAA concludes that the switch failures are internal to the switch 
itself and do not cause sufficient smoke or arcing in the cockpit to 
create a hazardous condition. The FAA has determined that failure of 
the subject switches does not present an unsafe condition. Accordingly, 
the proposed rule is hereby withdrawn.
    Withdrawal of this notice of proposed rulemaking constitutes only 
such action, and does not preclude the agency from issuing another 
notice in the future, nor does it commit the agency to any course of 
action in the future.
    Since this action only withdraws a notice of proposed rulemaking, 
it is neither a proposed nor a final rule and therefore, is not covered 
under Executive Order 12866, the Regulatory Flexibility Act, or DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979).

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Withdrawal

    Accordingly, the notice of proposed rulemaking, Docket 93-NM-19-AD, 
published in the Federal Register on April 12, 1993 (58 FR 19069), is 
withdrawn.

    Issued in Renton, Washington, on July 18, 1994.
S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-17859 Filed 7-21-94; 8:45 am]
BILLING CODE 4910-13-U