[Federal Register Volume 60, Number 74 (Tuesday, April 18, 1995)]
[Notices]
[Pages 19443-19444]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-9501]



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DEPARTMENT OF TRANSPORTATION

Aircraft Flight Recorder and Cockpit Voice Recorder

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of Cancellation of Technical Standard Orders (TSO's) 
C51a and C84.

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SUMMARY: This notice cancels TSO-C51a, Aircraft Flight Recorder and 
TSO-C84, Cockpit Voice Recorder. TSO-C51a prescribes the minimum 
performance standards that aircraft flight recorders were required to 
be identified with marking ``TSO-C51a,'' dated January 6, 1966. TSO-C84 
prescribes the minimum performance standards that cockpit voice 
recorders (CVR) were required to be identified with marking ``TSO-
C84.'' This cancellation will ensure that future flight recorders and 
cockpit voice recorders are produced under TSO-C123a, Cockpit Voice 
Recorder System, and TSO-C124a, Flight Data Recorder Systems.

EFFECTIVE DATE: May 18, 1995.

FOR FURTHER INFORMATION CONTACT:
Ms. Bobbie J. Smith, Technical Programs and Continued Airworthiness 
Branch, AIR-120, Aircraft Engineering Division, Aircraft Certification 
Service, Federal Aviation Administration, 800 Independence Avenue, SW., 
Washington, DC 20591, Telephone (202) 267-9546.

SUPPLEMENTARY INFORMATION:

Background

    The National Transportation Safety Board reported that seven flight 
recorder media destroyed by postimpact fire in [[Page 19444]] six 
accidents prompted concern about the adequacy of the performance 
standards for flight recorders. Minimum performance standards for 
impact and fire protection are outlined in four Technical Standard 
Orders (TSO's): TSO-C84 and TSO-C123 address CVR's and TSO-C51a and 
TSO-C124 address FDR's. TSO-C51a and TSO-C84 have essentially the same 
fire protection requirements; the fire test protocol requirements 
outlined in these TSO's are less stringent than the requirements 
outlined in the recently issued TSO-C123 and C124. Further, the fire 
test protocol in TSO-C51a and C84 is so vague that a recorder could be 
subjected to temperatures much lower than 1,100  deg.C due to 
inadequate burner heat release and still pass the test. The FAA 
recognized this deficiency in its 1970 report, ``Fire Test Criteria for 
Recorders.'' The report states:

    ``This requirement [TSO-C51a/C84] specifies the temperature, but 
not the source or the BTU rate of the flame. The temperature at the 
recorder flame impingement area must be 1,100  deg.C (2,012  deg.F). 
Thus, a recorder could meet the TSO requirements by passing a test 
in which the recorder is exposed to low heat output flames producing 
a temperature of 1,100  deg.C at a point of a few inches in front of 
the recorder while the temperature at the recorder case could be 
much less than 1,100  deg.C.''

    The temperature and duration for the fire test required by TSO's 
C51a, C84, C123, and C124 are the same. However, only the more exacting 
test protocol prescribed by TSO-C124 is likely to determine if a 
recorder will actually survive a high intensity, short duration fire.
    Based on the findings of the NTSB, TSO-C54a and TSO-C81 are 
canceled May 18, 1995. Because of the need to ensure that the data, 
cockpit voice described above, is preserved, good cause exists to 
cancel TSO's C51a and C84 without prior notice and opportunity to 
comment.

    Issued in Washington, DC, on April 12, 1995.
John K. McGrath,
Manager, Aircraft Engineering Division, Aircraft Certification Service.
[FR Doc. 95-9501 Filed 4-17-95; 8:45 am]
BILLING CODE 4910-13-M