AW109: identify the gearbox covered by AD 2026-0168

Since 7 September 2026, EASA AD 2026-0168 has required repeated maintenance actions on certain tail gearboxes in the A109/AW109 family. To establish the work needed, first identify the installed case assembly’s part number, manufacturer and serial number. The helicopter model alone, or the serial number prefix alone, is not enough.

An AD, or Airworthiness Directive, is mandatory for the aircraft to which it applies. This one was issued on 24 August 2026 after reports of abnormal oil darkening, sometimes accompanied by early metallic contamination. Internal wear or gearbox failure could reduce yaw authority, the ability to control the helicopter’s heading, and overall control. Source: EASA record and PDF, pages 1 and 2.

Aircraft applicability comes first, the installed part determines the group

The AD covers all serial numbers of A109A, A109AII, A109C, A109E, A109K2, A109LUH, A109S, including those with a Trekker kit, and AW109SP helicopters.

TGB means tail gear box, which transmits drive to the tail rotor. The affected-part definition combines three criteria for its case assembly:

• Part number, or P/N: 109-0442-01, all dashes.
• Manufacturer: Turbomecanica.
• Serial number, or S/N: TURXXXXX, where the five X characters represent serial number digits.

A part number identifies a part type; a serial number identifies an individual item. Helicopters with a TGB meeting this definition installed are Group 1. Those without one are Group 2, but remain within the AD’s applicability. Source: PDF definitions, pages 1 and 2.

Initial timing and repetitive intervals use different rules

For Group 1, paragraph 1 requires the first actions during the first reference maintenance action defined by the AD, or within 30 days after the effective date, whichever occurs later. It is therefore not a universal requirement to act within 30 days regardless of reference maintenance.

The reference maintenance action is tail rotor gearbox oil replacement under Maintenance Planning Manual section 05-70 for A109A, A109AII, A109C, A109E and A109K2. For A109LUH, the AD identifies AMPI task 12-07; for A109S and AW109SP, AMPI task 65-01. AMPI means Aircraft Maintenance Planning Information.

Actions then repeat at intervals no longer than 100 flight hours or six months, whichever occurs first. Note 1 permits a noncumulative tolerance of 10 flight hours or 30 days, whichever occurs first, only to synchronise this work with other tasks already granted such a tolerance in the applicable maintenance manual. It is not an automatic allowance to add to the schedule. Source: PDF, paragraph 1 and Note 1, pages 2 and 3.

Four actions, followed by any required response

The required actions are checking oil colour through the oil level indicator, detailed inspection of the chip detector, cleaning it and testing its operation. The chip detector helps identify metallic debris.

If a discrepancy defined in the manufacturer’s bulletin is found during any of these actions, paragraph 2 requires the applicable corrective work before the next flight. The specific reporting duty in paragraph 5 concerns findings during the oil colour check or operational test: report to Leonardo within 30 days after that action or after the effective date, whichever is later. This distinction does not remove any other applicable occurrence reporting duties.

Under paragraph 3, replacing the affected TGB with one outside the affected definition terminates paragraph 1’s repetitive actions for that helicopter, which becomes Group 2. Paragraph 4 also permits installation of an affected TGB, provided Group 1 requirements are met after installation. Source: PDF, paragraphs 1 to 5.

Prepare the instructions and supporting records

ASB means the manufacturer’s Alert Service Bulletin. The AD refers to six Leonardo bulletins, all dated 13 April 2026: 109-168 at original issue for A109A/A109AII/A109C; 109EP-198 Revision A for A109E; 109K-087 Revision A for A109K2; 109L-136 Revision A for A109LUH; 109S-143 Revision A for A109S; and 109SP-178 Revision A for AW109SP. Later approved revisions are accepted. Source: PDF, pages 1 and 3.

Our recommendation is to link the part’s identification to installation evidence, then retain the completed tasks, their hours and dates, results and any follow-up work. Discrepancy criteria and working methods must come from the applicable bulletin, which this article does not reproduce. The actual records allow authorised personnel to establish the helicopter’s group and deadlines.