Tail Rotor Drive — Titanium Bolts — Identification / Replacement
- Published
- Effective
- Deadline
AI-generated summary of the official EASA document. Verify against the PDF before acting.
What to do
Operators of EC135 and EC635 helicopters must inspect all titanium bolts with Part Number L535M3001201 on the forward and aft tail rotor drive shafts within 50 flight hours or 2 months from 16 May 2020, whichever occurs first. If any affected bolts are found, they must be replaced with serviceable parts before the next flight. From the effective date, only serviceable titanium bolts may be installed on these helicopters.
Summary
EASA Airworthiness Directive 2020-0099 is an airworthiness directive addressing Airbus Helicopters Deutschland GmbH EC135 and EC635 helicopter models. It concerns the identification and replacement of certain titanium bolts (Part Number L535M3001201) used in the tail rotor drive, which may have been improperly heat treated, leading to potential hydrogen embrittlement. This directive mandates inspection and, if necessary, replacement of affected titanium bolts to ensure continued safe operation.
What changed
EASA Airworthiness Directive 2020-0099 introduces a new mandatory inspection requirement for titanium bolts installed on the forward and aft tail rotor drive shafts of EC135 and EC635 helicopters. It requires operators to identify affected bolts marked with the manufacturer monogram 'D' or those with unidentified markings and replace any found defective before further flight. The directive also prohibits the installation of affected titanium bolts from the effective date onward.
Why it matters
This directive is critical for aviation professionals because it addresses a potential safety risk due to hydrogen embrittlement in titanium bolts, which could lead to bolt rupture and reduced helicopter control. Operators and maintenance organizations must ensure compliance to prevent in-flight failures and maintain airworthiness. Compliance teams need to track inspections and replacements within the specified deadlines to avoid regulatory violations and ensure flight safety.
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