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Safety Recommendation Details

Safety Recommendation A-92-133
Details
Synopsis: ON JUNE 8, 1992, A BEECH 1900 OPERATED BY G.P. EXPRESS AIRLINES CRASHED ON ITS FINAL APPROACH TO ANNISTON METROPOLITAN AIRPORT, ANNISTON, ALABAMA. TWO CREWMEMBERS AND FOUR PASSENGERS WERE ON BOARD: THE CAPTAIN AND TWO PASSENGERS WERE KILLED; AND THE FIRST OFFICER AND THE TWO REMAINING PASSENGERS SUFFERED SERIOUS INJURIES. THE AIRCRAFT, WHICH WAS DESTROYED ON IMPACT, WAS EQUIPPED WITH A COCKPIT VOICE RECORDER (CVR) MANUFACTURED BY B+D INSTRUMENTS AND AVIONICS. ALTHOUGH THE QUALITY OF THE RECORDING WAS GENERALLY GOOD FOR THE ENTIRE FLIGHT FROM ATLANTA, GEORGIA, RECOVERY OF CRITICAL CREW CONVERSATIONS WAS HAMPERED BY THE SIMULTANEOUS RECORDING OF THE AUDIO SIGNALS FROM THE CREWMEMBERS' INTERCOM MICROPHONES AND RADIO TRANSMISSIONS ON THE SAME CVR CHANNEL. ON JUNE 7, 1992, A CONSTRUCCIONES AERONAUTICAS S.A. (CASA) 212 OPERATED BY EXECUTIVE AIR CHARTER, INC., CRASHED ON ITS FINAL APPROACH TO EUGENIO MARIA DE HOSTO AIRPORT, SAN JUAN, PUERTO RICO, KILLING THE FIVE PERSONS ON BOARD: TWO FLIGHT CREWMEMBERS AND THREE PASSENGERS. THE AIRCRAFT WAS EQUIPPED WITH A CVR MANUFACTURED BY LORAL DATA SYSTEMS-FAIRCHILD AVIATION RECORDERS. ALTHOUGH THE QUALITY OF THE RECORDING WAS GOOD, DETERMINATION OF CRITICAL CREW CONVERSATIONS WAS HAMPERED BY THE SIMULTANEOUS RECORDING OF THE CREW INTERCOM SIGNALS AND RADIO TRANSMISSIONS ON THE SAME CVR CHANNEL.
Recommendation: THE NTSB RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION: REQUIRE, FOR AIRCRAFT THAT MUST BE OPERATED BY TWO CREWMEMBERS AND BE EQUIPPED WITH A FOUR-CHANNEL COCKPIT VOICE RECORDER (CVR), THE EXCLUSIVE USE OF THE THIRD CVR RADIO CHANNEL TO RECORD ONLY AUDIO SIGNALS FROM THE COCKPIT CREW INTERCOM SYSTEM AND THE TWO "HOT" BOOM MICROPHONES.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Unacceptable Action
Mode: Aviation
Location: ANNISTON, AL, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: ATL92MA118
Accident Reports: Controlled Collision with Terrain GP Express Airlines, Inc., Flight 861 A Beechcraft C99, N118GP
Report #: AAR-93-03
Accident Date: 6/8/1992
Issue Date: 1/6/1993
Date Closed: 6/2/1997
Addressee(s) and Addressee Status: FAA (Closed - Unacceptable Action)
Keyword(s):

Safety Recommendation History
From: NTSB
To: FAA
Date: 6/2/1997
Response: ON 3/8/93, THE FAA RESPONDED TO THE BOARD'S RECOMMENDATION STATING THAT IT DID NOT AGREE WITH BOARD'S RECOMMENDATION & CITED EUROCAE WORKING GROUP 18 'S (WG18) REVISIONS TO ED-56 AS RELEVANT TO THE RECOMMENDATION. THE BOARD NOTED IN ITS RESPONSE OF 4/23/93, THAT THE BOARD STAFF HAD PARTICIPATED IN WG18'S EFFORTS & THAT ISSUANCE OF ED-56A WOULD NOT SATISFY THE INTENT OF THE BOARD'S RECOMMENDATION. MORE THAT 4 YEARS HAVE ELAPSED SINCE THE BOARD'S LETTER, & BOARD STAFF IS AWARE THAT NO ACTION HAS BEEN TAKEN OR IS BEING CONTEMPLATED WITH RESPECT TO IMPLEMENTATION OF THE RECOMMENDATION. FURTHER DIALOGUE ON THIS ISSUE AT THIS TIME APPEARS FUTILE. CONSEQUENTLY, A-92-133 IS CLASSIFIED "CLOSED--UNACCEPTABLE ACTION."

From: FAA
To: NTSB
Date: 4/23/1997
Response: NO INCOMING LETTER. THIS IS A FOLLOWUP TO A LETTER ON WHICH THERE HAS BEEN NO CORRESPONDENCE FOR MORE THAN 1 YEAR.

From: NTSB
To: FAA
Date: 4/23/1993
Response: THE BOARD BELIEVES THAT THE PRELIMINARY ACTION TAKEN BY THE FAA FAILS TO MEET THE INTENT OF RECOMMENDATION A-92-133. THE RECOMMENDATION IS CLASSIFIED "OPEN--UNACCEPTABLE RESPONSE" PENDING FURTHER RESPONSE FROM THE FAA.

From: FAA
To: NTSB
Date: 3/8/1993
Response: (The FAA does not agree with this recommendation to rewire the third crewmember channel of a CVR directly to the interphone system. Currently, the European Organization for Civil Aviation Electronics (EUROCAE) Working Group 18 is revising the ED-56 Minimum Operational Standards (MOPS) for CVR's referenced in Technical Standard Order C-123. The working group is considering the following areas that appear to be relevant to Safety Recommendation A-92-133: Basically, two mixed or superimposed voice conversations can be distinguished as separate information when listening to audio signals. This ability to recognize either conversation can be demonstrated with the introduction of the hot-boom microphones. This is also possible where the lower level voice is the one of importance. The ability of separating two conversations, even at considerable level differences, is greatly reduced if (1) either one of the audio signals is driven into saturation or (2) the unlinear recording range of the equipment CVR, audio panel, or summing amplifier is reached (due to high levels). During the high amplitudes of one (or both) signals, the audio signal is amplitude limited (clipped) and the information of the other signal is "clipped" or discontinued during the clipping time interval and information is lost. These clipping types of distortions can be measured as intermodulation distortions and need to be understood and controlled. The new EUROCAE MOPS will require a much higher audio quality whereby multiple frequencies are being used during the test of the Speech Transfer Index. Also, the signal-to-noise ratio has been increased from 35 decibels (56 to 1 ratio) to 48 decibels (250 to 1 ratio). This should ensure considerably better performance over large audio level variations. The FAA believes that further analysis of the cited aircraft audio systems is needed to ensure that there is no clipping or intermodulation of the audio signals before it reaches the CVR input. The audio panel and the summing amplifier feeding the CVR input need to be evaluated. Actual peak input levels need to be either measured or reconstituted. The EUROCAE Working Group plans to examine these areas in the near future. The FAA believes that the suggested safety recommendation solution of recording two intercom channels on a separate CVR track together with two hot-boom microphones will lead to the same type of interference and suppression of one signal by a stronger one if the above requirements are not met. In conclusion, the FAA contacted a major CVR manufacturer and two major aircraft audio system manufacturers for their comments on this recommendation. The consensus was that the FAA should not require another untested aircraft audio change until a detailed technical analysis has been completed. Therefore, the FAA believes that the consideration of Recommendation A-92-133 should be delayed until the EUROCAE Working Group has completed its analyses. I will keep the Board apprised of the progress of the EUROCAE Working Group's effort.