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General Aviation Safety
ON JULY 9, 1982, A PAN AMERICAN BOEING 727 (FLIGHT 759) CRASHED INTO A RESIDENTIAL AREA IN KENNER, LOUISIANA, KILLING 145 PERSONS ON BOARD THE AIRCRAFT AND 8 PERSONS ON THE GROUND. THE SAFETY BOARD'S EXAMINATION OF THE UNITED CONTROL CORPORATION (SUNDSTRAND) V-557 COCKPIT VOICE RECORDER (CVR) FROM THE AIRCRAFT HAS DISCLOSED THAT THE RECORDING WAS OF SUCH POOR QUALITY THAT A COMPLETE READOUT MAY NOT BE POSSIBLE. THE TAPE WAS IN EXCELLENT PHYSICAL CONDITION, EXHIBITING NO APPARENT FIRE DAMAGE OR TEARING. THE SAFETY BOARD CONCLUDES THAT THE POOR QUALITY OF THE TAPE IS ENTIRELY A RESULT OF THE RECORDING PROCESS. ON SEPTEMBER 22, 1981, AN AIR FLORIDA AIRLINES, INC., DC-10 30CF SUSTAINED AN UNCONTAINED FAILURE OF ITS RIGHT UNDER WING ENGINE (NO. 3) DURING THE TAKEOFF ROLL AT MIAMI INTERNATIONAL AIRPORT, MIAMIA, FLORIDA. THE ENGINE FAILED AT 90 KNOTS INDICATED AIRSPEED; THE PILOT REJECTED THE TAKEOFF AND STOPPED THE AIRCRAFT SAFELY. DURING ITS INVESTIGATION OF THE ACCIDENT, THE SAFETY BOARD WAS NOT ABLE TO READ THE V-557 CVR FROM THE AIRCRAFT BECAUSE THE RECORDING WAS DISTORTED AND THE TAPE DRIVE EXHIBITED EXTREMELY POOR SPEED CONTROL. HENCE, NO INFORMATION AT ALL COULD BE OBTAINED FROM THE TAPE. ON FEBRUARY 16, 1982, A REEVE ALEUTIAN AIRWAYS YS-11 CRASH LANDED ON THE ICE IN THE NAKNEK RIVER AT KING SALMON, ALASKA. THE UNSTABLE TAPE SPEED OF THE MODEL V-557 CVR TAPE MADE A FREQUENCY ANALYSIS OF THE ENGINE SOUNDS AND AIR TRAFFIC CONTROL/CVR TIME CORRELATION IMPOSSIBLE. THE SAFETY BOARD IS CONCERNED THAT THE DEGRADED QUALITY OF THE RECORDINGS THAT IT HAS FOUND IN RECENT INVESTIGATIONS INDICATES THAT THE MAINTENANCE PRACTICES FOR THE MODEL V-557 CVR HAVE AGAIN DEGRADED AND THAT VALUABLE ACCIDENT INFORMATION WILL CONTINUE TO BE LOST IN ACCIDENTS INVOLVING AIRCRAFT EQUIPPED WITH THIS MODEL CVR.
THE NTSB RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION: INITIATE A PROGRAM INVOLVING ALL U.S. OPERATORS USING UNITED CONTROL CORPORATION (SUNDSTRAND) V-557 COCKPIT VOICE RECORDERS TO RANDOMLY CHECK A REPRESENTATIVE SAMPLE OF THESE RECORDERS IN OPERATIONAL USE TO ASSURE THAT THEY ARE OPERATING WITHIN DESIGN SPECIFICATIONS. IF THIS INSPECTION REVEALS SIGNIFICANT PROBLEMS WITH ACCEPTABILITY OF RECORDED DATA, REQUIRE THE NECESSARY CHANGES IN THE CARRIER'S MAINTENANCE PROGRAMS TO ASSURE CONTINUED AIRWORTHINESS OF THESE RECORDERS. (URGENT)
Original recommendation transmittal letter:
Closed - Unacceptable Action
Kenner, LA, United States
Pan American World Airways, Inc., Clipper 759, Boeing 727-235, N4737
Addressee(s) and Addressee Status:
FAA (Closed - Unacceptable Action)
Safety Recommendation History
You state in your letter that, "A teardown inspection of Pan American's V-557 CVR at the Sundstrand facility in Redmond, Washington, showed that poor quality of recorded information was attributed to an internal open circuit in the CVR erase head, which is an unusually rare type of failure." The Safety Board considers the V-557 CVR problem much more wide-ranging and serious than the FAA perceives it to be. As we have stressed in previous verbal and written communication, the poor performance of this recorder in the New Orleans accident is not an isolated case. A large percentage of the V-557 CVR recordings received in the Safety Board's laboratory are of unacceptably poor quality. In this age of the inexpensive stereo tape recorder, it is difficult to understand why FAA allows CVRs of such poor quality to be carried aboard air carrier aircraft. The technology for vastly improved recording quality is available and has been available for several years. We are not satisfied with the FAA's proposed solution to the V-557 CVR problem, especially the advisory nature of Maintenance Bulletin 23-17 ("Principal Avionic Inspectors should review the maintenance programs of all operators using V-557 CVRs and encourage them to adopt the above recommendations. The Avionics Branch, AWS- 350, should be informed of difficulties encountered with operators not willing to perform the checks and inspections at the frequencies specified.") We have no assurance that operators will adhere to the recommendations, and we do not believe that the FAA's actions will provide sufficient feedback to allow proper evaluation of the V-557 CVR's performance. Therefore, the Safety Board has classified Recommendations A-82-62 and -63 as "Closed--Unacceptable Action." Notwithstanding the foregoing, we are pleased that FAA has initiated a review program of all CVR/FDR devices. We await the results of this evaluation and details of the specific programs to be undertaken. We respectfully suggest that you employ the assistance of audio engineers who are not involved with CVR manufacturers in evaluating the present state of the art in audio recording. In reviewing the documents attached to your letter, we became aware of paragraph 23- 16 of Order 8340.1A (page 11). We believe that the contents of paragraphs (1), (2), and (4) are misleading and should be deleted or modified to reflect current technological developments. Paragraph (1) states, "There is no practical way to enhance the capability of the CVR self-test circuit." This may have been true years ago, and may still be true for the older recorders. However, continuous recording self-monitoring circuitry is now well within the state of the art and has been available in commercial systems for some time. A program of upgrading the self-test function should be undertaken Data Source: NTSB Recommendations to FAA and FAA Responses by the CVR manufacturers. The CVR involved in the Pan American accident at New Orleans, Louisiana, when put through the "self-test" cycle at the Sundstrand facility, indicated that the recording was satisfactory, even though it was unintelligible without sophisticated audio processing. Further, our audio engineer has taken a number of faulty V-557 CVRs to the facility, and all have "self tested" well. Paragraph (2) states, "The basic design of the CVR provides inherent redundancy of recorded information by means of the multichannel concept. Because of this redundancy, failure of a single "untested" component does not have a catastrophic effect on the vital usefulness of the CVR as an accident investigation tool." This paragraph is also in error. The three radio channels are redundant, but the single cockpit area microphone (CAM) channel recording cockpit conversations has no redundancy. It is the CAM channel that provides the most important CVR information in aircraft accident investigation. It is not the three redundant radio channels that concern the Safety Board, but rather the nonredundant CAM channel. Paragraph (4) states, "A 100 percent check of the installed CVR system can be made by: (a) Use of the self-test feature combined with; (b) listening to each channel by use of headset plugged into the headphone at the microphone control unit in the cockpit." This implies that a 100-percent check of the installed CVR system can be made by use of the self-test circuit and by listening to the recording. This is not, in fact, a 100-percent test of the installed equipment and should only be considered as the best economically practical way of preflight testing present equipment. If our staff can be of assistance to you in your efforts to review CVR/FDR systems and installations, we shall be more than happy to cooperate.
FAA LETTER: FAA SUGGESTED THAT THIS WAS A POSSIBLE "AIRCRAFT PROBLEM" RATHER THAN A CVR PROBLEM - DEFECTIVE WIRING. A TEARDOWN INSPECTION OF THE PAN AM V-557 CVR BY THE MANUFACTURER REVEALED AN OPEN CIRCUIT IN THE CVR ERASE HEAD WHICH IS CONSIDERED AN UNUSUALLY RARE TYPE OF FAILURE. ON 10/22/82, FAA ISSUED MAINTENANCE BULLETIN NO. 23-17, AND IS CONFIDENT THAT THIS WILL RESULT IN IMPROVED PERFORMANCE. FAA CONSIDERS REPLACEMENT AFTER 2 YEARS TO BE EXTREMELY COSTLY. NOTWITHSTANDING THEIR OBJECTION OF THE TWO RECOMMENDATIONS, THEY ARE CONSIDERING A REEVALUATION OF ALL CVR/FDR DEVICES.
Your comments in response to this recommendation state, in part, that you will obtain maintenance information regarding the Pan American 727 which crashed at Kenner, Louisiana, which includes the airplane's maintenance records and a report from Sundstrand relative to the condition of that particular cockpit voice recorder (CVR). As noted in the text of the Safety Board's recommendation letter of July 13, 1982, this recommendation was made not simply as a result of the Kenner, Louisiana, accident but also because of unsatisfactory V-557 cockpit voice recorder readouts in the Air Florida DC-10 incident at Miami, Florida, on September 22, 1981, and in the Reeves Aleutian Airways YS-11 accident at King Salmon, Alaska, on February 16, 1982. Further, it is the Safety Board's belief as indicated by its 1978 Safety Recommendations A-78-21 and -22, that the condition of the recorders in service is unknown because the method of testing them is unsatisfactory. We are concerned that Data Source: NTSB Recommendations to FAA and FAA Responses an examination of V-557 CVR maintenance records will lead to erroneous conclusions as to the condition of the recorders because there is no way to determine audio quality and intelligibility short of actually listening to the recorded information, and this is not done in the course of routine maintenance. Our Audio Engineer found, when he checked the Pan American Airways (Kenner) CVR at the Sundstrand plant, that the "push to test" preflight check showed a satisfactory recording in progress -- this, in spite of the fact that quality of the Kenner tape was unacceptably poor. Moreover, the Safety Board has received yet another V-557 CVR tape of unsatisfactory quality since the Kenner, Louisiana accident. A Republic Airlines DC-9 aborted a takeoff at Boise, Idaho, on July 5, 1982. The tape from the V-557 recorder was partially unintelligible. It was examined at the Sundstrand plant in the presence of our Audio Engineer, and excessive distortion was found in the recording. The "push to test" check indicated that the recorder was operating satisfactorily. We trust your investigation into these recorders will convince you that the present method of testing them is unsatisfactory, and that their condition in the field is unknown. We are particularly concerned about the poor quality of the cockpit area microphone (CAM) channel. The CAM channel of the recorder contains critical accident data which is totally unique and which is not duplicated on any other channel. The non-redundant nature of the CAM data makes it absolutely necessary that it be intelligible and of good audio quality. Our experience has shown that an unacceptable number of unsatisfactory CVRs are in service, and we are concerned that they are not being detected and scheduled for maintenance. Pending receipt of a report reflecting more tangible efforts to study the need for, and to develop if needed, a satisfactory method of checking V-557 CVRs and the results of your current study, A-82-62 will be held in an "Open--Acceptable Action" status.
FAA LTR: IN ORDER TO CONFIRM WHETHER THE COCKPIT VOICE RECORDER'S (CVR) PERFORMANCE AS DESCRIBED BY THE NTSB IS MAINTENANCE RELATED, WE ARE OBTAINING INFORMATION WHICH INCLUDES THE AIRPLANE'S MAINTENANCE RECORDS AND A REPORT REGARDING THE CVR'S PERFORMANCE AS DETERMINED BY THE MANUFACTURER, SUNDSTRAND. IN ADDITION TO THIS EVALUATION, THE FAA IS ALSO DETERMINING THE NUMBER OF V-557 CVR'S PRESENTLY IN USE AND THE INSPECTION INTERVALS THE AIR CARRIERS ARE USING. OUR ACTION IS NECESSARY BEFORE A DECISION CAN BE MADE AS TO WHETHER OR NOT A RANDOM SAMPLING SHOULD BE INITIATED. A DECISION SHOULD BE MADE BY OCTOBER 22, 1982.
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