NTSB · Safety Recommendation
Safety Recommendation A-85-130
Recommendation
THE NTSB RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION: REVIEW THE DESIGN OF THE LOCKHEED L-1011 PASSENGER OXYGEN SYSTEM, AND REQUIRE CHANGES AS NEEDED SO THAT THERE IS NO POTENTIAL FOR FAULTS WHICH CAN DISABLE THE SYSTEM AND REMAIN UNDETECTED.
Safety Issue and Context
THE NTSB IS CONTINUING TO PARTICIPATE IN THE INVESTIGATION OF THE CIRCUMSTANCES OF THE IN-FLIGHT FIRE WHICH WAS DETECTED ONBOARD A ROYAL JORDANIAN AIRLINES LOCKHEED L-1011 AIRPLANE WHILE THE AIRPLANE WAS DESCENDING TO LAND AT SINGAPORE ON OCTOBER 18, 1985. THE EXAMINATION OF THE AIRPLANE WAS CONDUCTED IN SINGAPORE BY AN INVESTIGATION TEAM THAT INCLUDED REPRESENTATIVES OF THE SAFETY BOARD. THE PRELIMINARY INVESTIGATION DISCLOSED THAT THE FIRE ORIGINATED IN THE LEFT AFT UNDERFLOOR AREA OF THE AIRPLANE'S FUSELAGE, AFT OF THE C-3 CARGO COMPARTMENT AND FORWARD OF THE REAR PRESSURE BULKHEAD.
THE SAFETY BOARD'S CONCERN THAT THE FIRE IGNITED AS A RESULT OF ELECTRICAL ARCING BETWEEN A FRAYED GENERATOR FEEDER CABLE AND A THIN WALL TITANIUM DUCT CONTAINING HIGH-PRESSURE BLEED AIR AND THE FIRE'S SUBSEQUENT PROPAGATION TO OTHER FUEL SOURCES WAS DESCRIBED IN A LETTER TO THE FEDERAL AVIATION ADMINISTRATION (FAA) DATED OCTOBER 25, 1985. THE SAFETY RECOMMENDATIONS CONTAINED IN THAT LETTER, A-85-91 AND -92, ADDRESS ACTIONS NEEDED TO PREVENT FUTURE OCCURRENCES OF A SIMILAR NATURE.
THE INVESTIGATION OF THE ACCIDENT DISCLOSED OTHER DISCREPANCIES IN THE L-1011 AIRPLANE WHICH WERE NOT CAUSAL TO THE EMERGENCY BUT WHICH COULD ADVERSELY AFFECT THE SAFETY OF PASSENGERS DURING AN EMERGENCY SITUATION.
Response History
August 3, 1987 · NTSB Correspondence · FAA
The FAA's final rule (Docket No. 86-NM-94-AD; Amendment 39-5594) adopting a new Airworthiness Directive requiring modification of the passenger oxygen system initiator sequencer timer switches in the Lockheed Model L-1011 series airplanes fulfills this recommendation, which is classified as "Closed--Acceptable Action."
May 29, 1987 · Recipient Response · FAA
ON MARCH 24, 1987, THE FAA ISSUED AN AD, DOCKET NO. 86-NM-94-AD; AMENDMENT 39-5594, WHICH REQUIRES MODIFICATION OF THE PASSENGER OXYGEN INITIAL SEQUENCER TIMER SWITCHES (SEQUENCERS).
March 10, 1987 · NTSB Correspondence · FAA
The Safety Board appreciates the need to modify the original Notice Of Proposed Rulemaking in order to provide service instructions that will ensure that faults with the Lockheed L-1011 passenger oxygen system are corrected. Pending the Board's review of the final action taken by the FAA on this issue, Safety Recommendation A- 85-130 has been classified as "Open--Acceptable Action."
January 27, 1987 · Recipient Response · FAA
THE FAA ISSUED A NPRM, DOCKET NO. 86-NM-94-AD, ON MAY 6, 1986 WITH A COMMENT PERIOD ENDING JULY 7, 1986, THE PROPOSED AD WOULD HAVE REQUIRED MODIFICATION OF THE L-1011 OXYGEN SYSTEM IN ACCORDANCE WITH THE MANUFACTURER'S INSTRUCTIONS. SUBSEQUENTLY, IT WAS DISCOVERED THAT PROBLEMS COULD OCCUR ON SOME SEQUENCERS WHEN ACCOMPLISHING THE MODIFICATION IN ACCORDANCE WITH THE SERVICE INSTRUCTIONS REFERENCED IN THE NPRM. THE MANUFACTURER IS NOW REVISING THE SERVICE INSTRUCTIONS TO INCORPORATE A REVISED MODIFICATION. DUE TO THE CHANGES IN THE PROPOSED MODIFICATION, THE FAA AMENDED THE NPRM ON OCTOBER 24, 1986, TO INCORPORATE THE REVISED MODIFICATIONS.
A COPY OF THE REVISED NPRM IS ENCLOSED FOR THE BOARD'S INFORMATION. ONCE THE COMMENTS HAVE BEEN REVIEWED AND ANALYZED, I WILL ADVISE THE BOARD OF FAA'S FINAL ACTION.
June 27, 1986 · Recipient Response · FAA
Enclosed for the Board's information is a copy of a Notice of Proposed Rulemaking (NPRM), Docket No. 86-NM-94-AD. The NPRM proposes an Airworthiness Directive that would require modification of oxygen initiator sequence timer switches (sequencers) on Lockheed Model L-1011-385 series airplanes. The adoption of this AD should vastly improve the reliability of the passenger oxygen system in the event of sudden loss of pressurization.
The public comment period for this NPRM ends July 7, 1986. Following a review of the comments, the FAA will advise the Board of its further actions.
May 13, 1986 · NTSB Correspondence · FAA
We are pleased that the manufacturer of the sequencer, Dynamic Controls, is redesigning the sequencer to ensure that no undetected fault will disable the system, and that upon approval of an acceptable design, Dynamic Controls plans to issue a service bulletin which will be the basis of an FAA Notice Of Proposed Rulemaking. However, the FAA's response appears to be focused on the fault in the sequence timers. In addition to the problem with the sequence timers, the oxygen system test circuit needs to be fully evaluated to ensure that the test circuit is capable of identifying latent electrical faults in the entire passenger oxygen
system, such as the one that occurred with the shorted transient suppression capacitators. Pending the FAA's further response, this recommendation is classified "Open--Acceptable Action."
February 20, 1986 · Recipient Response · FAA
"THE FAA CONCURS WITH THE BOARD'S RECOMMENDATION. THE MANUFACTURER OF THE SEQUENCER, DYNAMIC CONTROLS, IS REDESIGNING THE SEQUENCER TO ENSURE THAT NO UNDETECTED FAULT WILL DISABLE THE SYSTEM. UPON FAA APPROVAL OF AN ACCEPTABLE DESIGN, DYNAMIC CONTROLS PLANS TO ISSUE A SERVICE BULLETIN. THE FAA WILL THEN ISSUE A NOTICE OF PROPOSED RULEMAKING (NPRM) AD WHICH WILL PROPOSE REQUIRING THE INCORPORATION OF THE MODIFICATION SPECIFIED IN THE SERVICE BULLETIN. I ANTICIPATE THAT A FINAL DECISION ON THE NPRM WILL BE MADE BEFORE JULY 1, 1986---".