Some G-Switches Showing Signs Of Deterioration Or Complete Failure
The FAA has issued a Special Airworthiness Information Bulletin (SAIB) to alert aircraft owners and operators with installations of certain ACR Electronics, Inc. (ACR)(formerly Artex Aircraft Supplies, Inc. and Chelton Avionics, Inc. and doing business as Wulfsberg Electronics) emergency locator transmitters that the ELT may not transmit alert and location signals in case of an accident due to an inoperative or a deteriorated G-switch.
ELTs located in high vibration environments, for example in the tail of a helicopter, could have its acceleration sensor deteriorate after having been subjected to high levels of shock and vibration for five (5) years or more. This SAIB recommends best practices for the inspection, modification and replacement of these ELTs located in high vibration environments.
The FAA has received reports of ACR ELT model C406 failures. Investigation and testing indicated that in some cases the main longitudinal G-switch was inoperative. Further investigations revealed that the performance of the ELT acceleration sensor could deteriorate after having been subjected to high levels of shock and vibration for five (5) years or more. This condition, if not detected and corrected, could result in the ELT not transmitting alert and location signals in case of an accident, which could result in delayed deployment of rescue crews and possibly preventing timely medical assistance to injured crew members or passengers.
To address this condition, ACR Electronics has published Service Bulletin (SB) 1000, identifying those ELTs fitted with the original G-switch, prescribing testing, replacement of the G-switch at five (5) years, or alternatively, reducing the normal inspection intervals after five (5) years service to assure continued reliability.
The FAA recommends the following:
Always follow the Instructions for Continued Airworthiness applicable to the ELT installed in the aircraft. Pay particular attention to recurring inspection intervals and instructions, which include recurrent testing of the G-switch.
If your aircraft is equipped with an ELT listed in Table 1 (see FMI link below), and the ELT is installed in a high vibration environment, for example in the tail of a helicopter, and the ELT has been in service for more than five (5) years, replace the G-switch in accordance with ACR SB1000. As an alternative to replacement, accelerated inspections may be performed in accordance with ACR SB1000 during the period from five (5) to ten (10) years in service, after which the G-switch should be replaced
An ELT that has been previously modified to include a new hermetically-sealed longitudinal G-switch P/N A1-12-0135, as indicated by ACR SB1000, would include marking on the label stating “G-Switch Replaced in Accordance with Service Bulletin 1000 G-Switch Replacement Date ________”. This modification is sufficient to address the concerns of this SAIB.
(Source: FAA)
ANN's Daily Aero-Linx (06.29.25)
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