EASA AD 2026-0168: the TGB serial number decides

EASA AD 2026-0168, issued on 24 August 2026 and effective on 7 September 2026, sorts the A109/AW109 fleet into two groups by the part installed: any helicopter with a Turbomecanica-made tail gearbox (TGB) case assembly P/N 109-0442-01, serial number TURXXXXX, falls under a repetitive inspection regime every 100 flight hours or 6 months, with reporting to Leonardo within 30 days if a discrepancy is found during the oil colour inspection or the operational test, and a terminating action by replacement. For an operator or a CAMO, neither the airframe's hours nor its age sets the maintenance burden: the serial number engraved on the tail gearbox installed today does.

This article works from the AD text, not from press coverage. Every quotation is drawn from the official AD 2026-0168 page and its reference PDF, verified line by line on 31 August 2026.

What the AD requires, text in hand

The status, first. AD 2026-0168 is issued by EASA under Part 21.A.3B of Regulation (EU) 748/2012, on type certificate EASA.R.005, with no supersedure and no corresponding foreign AD ("Foreign AD: Not applicable"). Its issue date is 24 August 2026; its effective date is 7 September 2026: as of 31 August, it is not yet applicable, and its compliance times run from that effective date. The draft was posted on 23 July 2026 as PAD 26-088, in consultation until 20 August 2026; the AD records: "No comments were received during the consultation period."

The unsafe condition. Several in-service events have been reported: "Several in-service events have been reported of abnormal darkening of the TGB oil during routine maintenance. The oil darkening may be accompanied by incipient metallic contamination, suggesting abnormal wear mechanisms within the TGB assembly." The AD concludes: "This condition, if not detected and corrected, could lead to abnormal internal wear or failure of the TGB, possibly resulting in loss of yaw authority and reduced control of the helicopter." Abnormal internal wear of the tail gearbox, detectable through oil darkening and incipient metallic contamination, up to the risk of loss of yaw authority.

The scope. The applicability covers Leonardo (formerly Finmeccanica, AgustaWestland, Agusta) A109A, A109AII, A109C, A109E, A109K2, A109LUH, A109S "(including helicopters equipped with Trekker kit)" and AW109SP helicopters, "all serial number(s)", ATA chapter 65 (tail rotor drive). On 13 April 2026 Leonardo published six Alert Service Bulletins, one per model: 109-168 (original issue) for A109A/AII/C, 109EP-198 Revision A for the A109E, 109K-087 Revision A for the A109K2, 109L-136 Revision A for the A109LUH, 109S-143 Revision A for the A109S and 109SP-178 Revision A for the AW109SP. "The ASB", as defined in the AD, provides the inspection, cleaning and operational test instructions.

The identity card of AD 2026-0168, per the official EASA PDF.

The serial-number sort at the heart of the AD

The decisive passage is a definition, not a presumption: "Affected TGB: Any tail gear box (TGB) case assembly having Part Number (P/N) 109-0442-01 (all dashes), manufactured by Turbomecanica, and s/n TURXXXXX, where 'XXXXX' refers to the digits of the TGB case s/n." Three cumulative criteria, all readable on the part's dataplate: P/N 109-0442-01 in all dashes, Turbomecanica as manufacturer, a TUR-prefixed serial number. The AD bounds no serial range: "XXXXX" refers to the digits of the case serial, meaning every Turbomecanica case assembly of that P/N with a TUR-prefixed serial is affected.

The two-group sort is just as literal: "Group 1 helicopters are those equipped with an affected TGB installed. Group 2 helicopters are those which do not have an affected TGB installed." Every helicopter serial number sits in the applicability, but the regime only attaches to the installed part. Two practical consequences. First, identification is both physical and documentary: you must know which gearbox is installed on which aircraft today, not at factory delivery. Second, a helicopter's group can change over installations and removals, because the AD explicitly allows installing an affected TGB (paragraph 4), provided the Group 1 regime is applied: a standard exchange, a loaner gearbox or a shop return can move an aircraft from one group to the other.

The contrast with FAA AD 2026-17-10 on Lycoming piston pins is instructive: that AD presumes the part "affected" when the 8130-3 form is missing; this one presumes nothing, it asks you to read the dataplate and keep the configuration current. In both cases, the records do the sorting.

The repetitive regime and its compliance times

The exact sequence, paragraphs (1) to (5):

First accomplishment, paragraph (1). For Group 1: "During accomplishment of the first reference maintenance action (as defined in this AD), or within 30 days after the effective date of this AD, whichever occurs later": at the first reference maintenance action, or within 30 days after the effective date, whichever comes later. The "whichever occurs later" is counter-intuitive but literal: if the next tail gearbox oil change is far out, it, not the 30 days, sets the first inspection. The reference maintenance action is the tail gearbox oil replacement: MPM task 05-70 "Tail Rotor 90° gearbox oil replacement" for the A109A, A109AII, A109C, A109E and A109K2, AMPI task 12-07 for the A109LUH, AMPI task 65-01 for the A109S and AW109SP.

Repetition. Thereafter, "at intervals not to exceed 100 flight hours (FH) or 6 months (see Note 1 of this AD), whichever occurs first": every 100 flight hours or 6 months, whichever comes first. Note 1 grants a tolerance: "A noncumulative tolerance of 10 FH or 30 days, whichever occurs first, may be applied to the intervals specified in paragraph (1) of this AD", to allow synchronization with other maintenance tasks for which a noncumulative tolerance is already granted in the applicable Maintenance Manual.

The four actions, paragraphs (1.1) to (1.4). At each occurrence: inspect the oil colour through the oil level indicator; accomplish a detailed inspection of the TGB chip detector; clean the chip detector; accomplish an operational test of the chip detector, per the ASB instructions.

Corrective actions, paragraph (2). If a "discrepancy" as defined in the ASB is detected during any of these actions: accomplish the applicable corrective actions "before next flight", per the ASB instructions.

Reporting, paragraph (5). If a discrepancy is detected during the oil colour inspection (1.1) or the operational test (1.4): "within 30 days after that maintenance action, or after the effective date of this AD, whichever occurs later, report those findings to Leonardo S.p.A." The Inspection Report Form attached to the ASB is an acceptable method. Three clarifications: the reporting obligation only covers discrepancies detected during those two checks (a discrepancy found at the detailed inspection or the cleaning requires corrective actions before next flight, not reporting); nothing is due without a discrepancy; the 30-day window runs from the maintenance action (or from the effective date, whichever occurs later).

Terminating action, paragraph (3). "Replacing the affected TGB of a helicopter with a TGB, which is not an affected TGB, constitutes terminating action for the repetitive maintenance actions as required by paragraph (1) of this AD for that helicopter. After that replacement, the helicopter is effectively considered to be a Group 2 helicopter." Replacement with a non-affected gearbox ends the repetitive regime, for that helicopter.

The Group 1 repetitive regime, paragraphs (1) to (5) of AD 2026-0168.

What this changes for a CAMO: the configuration records decide the group

The affected fleet is ours: corporate, EMS and utility A109s and AW109s across Europe, aircraft that accumulate gearbox installations and removals over repairs and exchanges. The method this AD imposes comes down to six reflexes:

1. Inventory the actual configuration. For every A109/AW109 in the fleet, identify the tail gearbox installed today: P/N, manufacturer, s/n, read from the case dataplate or the latest shop records, not only from factory delivery data.
2. Qualify every aircraft. Group 1 if an affected TGB is installed, Group 2 otherwise. Paper applicability by model is not enough: today's part is what counts, and an aircraft can change groups with every gearbox movement.
3. Program the repetitive task in the AMP. 100 flight hours or 6 months, whichever occurs first, noncumulative tolerance of 10 FH or 30 days, reserved for synchronization with a task already granted such a tolerance; first due date anchored to the first gearbox oil change or 30 days after 7 September 2026, whichever occurs later. The planning mechanics are the same as for FAA AD 2026-17-10, on the EASA side this time.
4. Keep proof of the qualification. Dataplate photo, verification date, source: in an authority inspection or a dispute, that trace is what proves the group, as with the airworthiness review report.
5. Control part movements. Every TGB installation or removal, loan, standard exchange, shop return, becomes a group-control point: paragraph (4) allows installing an affected TGB, but the aircraft immediately falls back under the Group 1 regime, inspections and reporting included.
6. Prepare the exit from the regime. The terminating action is a replacement: weigh, per aircraft, the cost of a non-affected gearbox against the perpetuity of 100 FH / 6-month inspections, and keep the ASB Inspection Report Form ready for 30-day reporting in case of a discrepancy within the meaning of paragraph (5).

What this article cannot establish

• No quantified fleet size. Unlike FAA ADs, the EASA AD publishes no estimate of the affected population; the number of Turbomecanica gearboxes in service is not public. Do not extrapolate.
• The AD is not yet in force. Issued 24 August 2026, it takes effect on 7 September 2026, and its compliance times run from that date. It is not an immediate-effect measure, and draft PAD 26-088 went through consultation without receiving a single comment.
• The ASB content is not public. The exact definition of "discrepancy", the acceptance criteria and the Inspection Report Form sit in the six Leonardo bulletins of 13 April 2026, distributed to operators; this article only reproduces what the AD quotes from them.
• No bounded serial range. "TURXXXXX" covers every Turbomecanica case assembly of P/N 109-0442-01 with a TUR-prefixed serial; the AD lists neither a range nor individual serials, so qualification happens part by part.
• The triggering events are not quantified. The AD refers to "several in-service events" of abnormal oil darkening, without stating their number or the fleets involved.

Kepler's take: when one registry line sets the regime

Kepler's take: AD 2026-0168 sums up our conviction in a single case: your helicopter's group, and therefore its maintenance burden for years to come, rests on three data points in your records, the P/N, the manufacturer and the s/n of the tail gearbox installed today. A current configuration register, one that knows which part is installed where, since when and where it came from, turns the AD's sort into a query of a few minutes, and a group change into an alert instead of a surprise at the next review. Kepler Aviation builds traceability and documentation-automation tooling for maintenance and continuing airworthiness management, within the Kepler Digitals ecosystem. To assess how well your configuration records can answer this type of sort, contact us.

Sources

• EASA, Airworthiness Directive 2026-0168, 24 August 2026 and official PDF: primary source for every quotation (applicability, definitions, required actions (1) to (5), Note 1, ref. publications, remarks), verified line by line on 31 August 2026. PAD 26-088 consultation from 23 July to 20 August 2026, no comments received (remark 2).
• Leonardo S.p.A. Helicopters, Alert Service Bulletins 109-168 (original issue), 109EP-198, 109K-087, 109L-136, 109S-143 and 109SP-178 (Revision A), all dated 13 April 2026: inspection, cleaning and operational test instructions, reporting form; documents cited in the AD's "Ref. Publications", distributed to operators.
• Regulation (EU) 1321/2014, Annex I (Part-M), points M.A.301 and M.A.303 (EUR-Lex): mandatory accomplishment of applicable ADs, recalled in the AD header.
• World Air News, "Two directives, one day, two different judgements about urgency", 25 August 2026: dated secondary coverage; its "two judgements about urgency" framing is not adopted here, this article's angle is the documentary sort by P/N and s/n.