NTSB · Safety Recommendation
Safety Recommendation A-72-116
Recommendation
TO THE FEDERAL AVIATION ADMINISTRATION: BROADEN THE APPLICABILITY OF AD 71-21-5 TO INCLUDE ALL AIRCRAFT WHICH HAVE A NICKEL-CADMIUM BATTERY IN THE PRIMARY ELECTRICAL SYSTEM.
Safety Issue and Context
THE NATIONAL TRANSPORTATION SAFETY BOARD HAS INVESTIGATED SEVERAL ACCIDENTS AND INCIDENTS INVOLVING NICKEL-CADMIUM BATTERY FIRES SINCE YOUR ISSUANCE OF ADVISORY CIRCULAR AC-00-33 AND AIRWORTHINESS DIRECTIVE AD 71-21-5. THE SAFETY BOARD IS CONCERNED OVER THE NEAR- CATASTROPHIC CIRCUMSTANCES OF SOME OF THESE OCCURRENCES. THE BOARD BELIEVES THAT ALTHOUGH THE AD WAS RESPONSIVE TO THE PROBLEM AS IT WAS KNOWN AT THE TIME, THE FACTS REVEALED IN OUR RECENT INVESTIGATIONS INDICATE A NEED FOR FURTHER CORRECTIVE ACTION.
Response History
September 10, 1973 · NTSB Correspondence · FAA
The proposal for a new ad has been discussed with representatives of air transport association, national business aircraft association, general aviation manufacturers association, and six airlines to assure that the ad as issued will be effective and practical. We are now processing ad action, applicable to all aircraft having nickel-cadmium batteries, regardless of cell construction and aircraft engine type. The ad will require comments regarding installation of temperature warning, battery disconnect, and other means of battery protection. This result is being issued in the form of a notice of proposed rulemaking rather than an adopted rule, to permit
industry development of improved methods of com- batting the problem. We believe our actions to be fully responsive to the problems covered in your safety recommendations a-72-1156 and a-72-117.
October 19, 1972 · Recipient Response · FAA
Require the removal from service of all main rotor gripe identified by part nos. 147-120-135-1 from bell helicopters equipped with the wooden main rotor blades. The 147-120-135-2 is approved for use on the bell 47g-2 helicopter, structurally, the -2 grip is the same as the -1 grip. In addition, in the failure area, the -1 and -2 gripe are identical to the -3 gripes. We do not believe that a requirement for removal of the -1 and -2 gripe is warranted. However, in view of the findings in mandatory 1200 hour inspection to highlight the failure area which is in the threads. We are attempting to trace the service history of the branchville part to
deter- mine the time and whether it was exposed to a blade strike.
August 10, 1972 · Recipient Response · FAA
The proposal for a new ad has been discussed with representatives of air transport association, national business aircraft association, general aviation manufacturers association, and six airlines to assure that the ad as issued will be effective and practical. We are now processing ad action, applicable to all aircraft having nickel-cadmium batteries, regardless of cell construction and aircraft engine type. The ad will require comments regarding installation of temperature warning, battery disconnect, and other means of battery protection. This result is being issued in the form of a notice of proposed rulemaking rather than an adopted rule, to permit
industry development of improved methods of com- batting the problem. We believe our actions to be fully responsive to the problems covered in your safety recommendations a-72-1156 and a-72-117.