[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proposed rule is withdrawn.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
