Navigation — Flight / Ground Logic — Modification
- Published
- Effective
- Deadline
- Replaces
- 2017-0201
AI-generated summary of the official EASA document. Verify against the PDF before acting.
What to do
Operators of EC 155 B and B1 helicopters must modify the Flight/Ground signal wiring to connector 11 ALPHA. Group 1 helicopters must complete the modification within 12 months after 25 October 2017, and Group 2 helicopters within 7 months after 31 March 2018, following the instructions in Airbus Helicopters service bulletins EC155-34A033 and EC155-34A037 respectively. Compliance with these modifications is mandatory unless previously accomplished.
Summary
EASA Airworthiness Directive 2018-0069 is an airworthiness directive affecting Airbus Helicopters EC 155 B and EC 155 B1 models. It addresses a safety issue related to the Flight/Ground signal logic used by the Attitude Heading and Reference Systems (AHRS) on these helicopters. The directive mandates modifications to ensure independent Flight/Ground signal supply to each AHRS to prevent erroneous flight instrument indications.
What changed
This directive supersedes EASA AD 2017-0201 and extends the required modifications to both Group 1 (post-mod 0722B51) and Group 2 (pre-mod 0722B51) helicopters. It requires modification of the connection and wiring to connector 11 ALPHA according to updated Airbus Helicopters service bulletins. The changes ensure compliance with the approved design by providing independent Flight/Ground signals to each AHRS unit.
Why it matters
The modification is critical to prevent simultaneous erroneous attitude and vertical speed indications caused by a single failure affecting both AHRS units. This reduces pilot workload and enhances flight safety, especially during instrument meteorological conditions when automatic flight control systems may not be engaged. Operators and maintenance teams must comply to maintain aircraft airworthiness and avoid potential flight control issues.
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