Transport Canada has issued an airworthiness directive that requires operators to inspect all aircraft types with Honeywell's Rescu406AF and 406AFN emergency locator transmitters (ELTs) and accompanying transmitter units following an ongoing investigation of the fire that broke out on a parked Ethiopian Airlines Boeing 787-8 aircraft at London Heathrow on 12 July.
The United Kingdom Air Accidents Investigation Branch (AAIB) is conducting an ongoing investigation to determine the cause of the fire, which occurred in the rear cabin ceiling of the aircraft where the ELT resides.
The AAIB is looking into whether it could have been caused by a pinched wire between the ELT and its lithium battery, but the cause is still undetermined.
Transport Canada, which served as the certifying authority for the ELT models, has issued the directive as a "precautionary measure" to address "wiring installation discrepancies" in either the transmitter units or the ELT batteries.
The transmitter units with part numbers 1152682-1, -2 and -3 are installed on the following models: Boeing 717, 727, 737, 747, 757, 777, 787, MD-11 and MD-90 aircraft; the Airbus A300, A310, A320, A321, A330, A340 and A380; ATR42 and 72 turboprops and the Dassault Aviation Falcon 7X business jet.
The directive requires one-time inspections of the ELT transmitter units for discrepancies in the battery wiring that could cause an electrical short, as well as the necessary actions to fix any issues if found.
Following the Ethiopian 787 fire, the US Federal Aviation Administration (FAA) on 26 July issued an airworthiness directive for 787-8 models to inspect the transmitters on that aircraft type. Boeing has asked airlines to inspect the ELTs on more than 1000 aircraft types in addition to the 787, including the 717, next-generation 737s, 747-400s, 767s and 777s. At least three 787 operators found pinched wires in the transmitters during inspections.
Airbus says it has not issued any directives for operators of its aircraft types with the same model of ELTs.
"We are not aware of any incidents of overheating or fire involving Honeywell ELTs on any Airbus aircraft and have not previously issued any related recommendations to our operators," says the airframer. "Nonetheless, we have been in contact with Honeywell to ensure that any recommendations they may have regarding the ELTs are taken into account."
Dassault Aviation says it issued a service newsletter on 2 August to operators with details about performing inspections on the ELTs for the Falcon 7X.
EASA says that it accepts the airworthiness directive as-is. The FAA could not be reached for comment.
The airworthiness directive is effective 150 days from its issued date of 15 August.