Engine Fuel and Control — Hydro-Mechanical Unit — Replacement / Modification
- Published
- Effective
- Replaces
- 2022-0040
AI-generated summary of the official EASA document. Verify against the PDF before acting.
What to do
Operators of Airbus A350-1041 aeroplanes with affected HMUs must replace these parts before they exceed 7,500 engine hours or within 48 months from 14 May 2025, whichever comes first. Installation of affected parts is prohibited after replacement with improved parts or from the effective date for Group 2 aeroplanes. Compliance must follow the instructions in Airbus Alert Operators Transmission A73P002-21 and Rolls-Royce service bulletins.
Summary
EASA Airworthiness Directive 2025-0100 is an airworthiness directive affecting Airbus A350-1041 aeroplanes equipped with Rolls-Royce Trent XWB-97 engines. It addresses the replacement and modification of hydro-mechanical units (HMU) with specific part numbers to prevent engine transient N1 shaft speed exceedance caused by worn Combining Spill Valve (CSV) pistons. The directive mandates compliance with Airbus and Rolls-Royce service instructions to ensure continued safe operation.
What changed
EASA Airworthiness Directive 2025-0100 supersedes the previous AD 2022-0040 and introduces the requirement to replace affected HMUs with improved parts having updated part numbers. It prohibits the installation of affected parts after replacement with improved parts and mandates replacement within specified engine hour limits or within 48 months of the AD's effective date. The directive also recognizes a new HMU developed and embodied in production through Airbus modification 120423 as terminating action.
Why it matters
This directive is critical for aviation professionals because it addresses a safety risk related to engine thrust loss and potential control issues during rejected take-offs due to HMU piston wear. Operators and maintenance organizations must ensure timely replacement of affected parts to avoid engine transient overspeed events and maintain regulatory compliance. Failure to comply could lead to operational restrictions or safety incidents.
More for Airbus A350
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