Part-ML compliance for owner-pilots — what you actually have to do.

Not legal or operational guidance. This guide is a practical orientation written for owner-pilots, not a substitute for the regulatory texts (Commission Regulation (EU) No 1321/2014, Annex Vb / Part-ML), AESA / EASA / CAMO advice, or the judgment of your aircraft’s responsible engineer.

Part-ML is the EASA continuing-airworthiness regime for the simpler end of general aviation: light aircraft, balloons, sailplanes — the stuff you fly yourself. It exists because the previous regime (Part-M) was sized for commercial operations and gave private owners a paperwork burden that didn’t fit the actual risk profile. Part-ML is the lighter alternative. This guide walks the four things you actually have to keep current under it.

What Part-ML is and which aircraft it covers

Part-ML applies to ELA1 and ELA2 aircraft that are not used for commercial operations (with limited exceptions). In practice, for a piston single owner-pilot in Europe, that means: most piston-single aeroplanes ≤2730 kg MTOM, including most C172, PA-28, SR22, DA40, A36, TB20, and the typical owner-flown spectrum.

If you operate under FAR Part 91 (an N-registered aircraft), you are not subject to Part-ML; the equivalent regime is the FAA’s. If you operate an EU-registered aircraft commercially, you may be subject to Part-CAO/Part-CAMO instead. The boundary matters: assume Part-ML, then verify against your aircraft’s actual registration and use category before relying on this guide for any specific decision.

The four documents you must keep current

Day-to-day, four artifacts carry the regime:

The Aircraft Maintenance Programme (AMP) — what you do, when, against the aircraft’s actual hours and calendar.
The Airworthiness Review Certificate (ARC) — your annual proof of continuing airworthiness.
The maintenance records — what was done, when, by whom, with what parts, signed.
AD compliance records — applicability and compliance evidence per AD that touches your tail.

Hangar’s data model wraps these four. You can run them on paper or in a spreadsheet (most owners do, somewhere); the question is whether you can produce them on demand for an inspector and whether your timeline survives an audit.

AMP (Aircraft Maintenance Programme): self-declared vs approved

Under Part-ML you can have a self-declared AMP (a “Pilot-owner declared AMP”) for ELA1 aircraft used non-commercially. You declare the AMP to the National Aviation Authority (in Spain, AESA) — you don’t get it approved. The authority can audit it; until they do, the declaration is valid.

Alternatively, you can have an approved AMP prepared by a CAMO/CAO. That route makes sense if your operations are more complex, if you fly with a club whose insurance requires it, or if you simply prefer a third party owning the document.

A Part-ML self-declared AMP must reference: the aircraft type design data (TCDS, manufacturer’s maintenance documentation), the operating environment (saltwater coastal vs continental, e.g.), the actual usage profile (hours/year, type of flying), and applicable ADs. Most owner-pilots use a manufacturer-provided template (Cirrus, Diamond, Cessna all publish guidance) and adapt it.

ARC: who issues it, when it expires, how renewal works

The Airworthiness Review Certificate is your annual proof that the aircraft remains continuously airworthy. Under Part-ML for self-managed aircraft, the ARC can be issued or extended by an authorised person — typically a CAMO/CAO, sometimes the National Aviation Authority directly, occasionally an Independent Certifying Staff member depending on national rules.

The ARC is valid for one year. Some renewals are full reviews (physical inspection plus document audit); others are extensions based on a satisfactory in-service review. The 90-day window before expiry is when you need to be moving — booking the inspector, gathering the documents, planning around availability.

For the full step-by-step, see our ARC renewal checklist for EASA piston aircraft.

The 100-hour vs annual question for piston singles

A common confusion: under Part-ML, the “100-hour inspection” of FAA folklore is not a Part-ML construct. Part-ML inspections follow the AMP, which references the manufacturer’s maintenance data — typically annual, with intermediate tasks at intervals appropriate to the airframe and engine.

If you came from FAR Part 91, the mental model that needs to change is “the 100-hour or annual, whichever comes first.” Under Part-ML, the inspection cadence is what your AMP says it is, with the manufacturer’s intervals as the baseline.

Component time tracking — why off-spreadsheet matters

Component times — engine TBO, propeller overhaul interval, vacuum-pump life, ELT battery, transponder check — drive the airworthiness clock. They run on flight hours, calendar, or sometimes cycles.

Off-spreadsheet, the failure mode is straightforward: a co-owner logs a flight in their own log, you don’t see it for two weeks, the engine TBO calculation in your head is two weeks behind, and a maintenance window quietly closes. The solution is shared, append-only state — every flight logged once, components recompute automatically, the dashboard tells you what’s overdue, what’s critical, what’s upcoming, and what’s OK.

This is exactly the workflow Airworth Hangar was built around: every flight you log recomputes the hour-based triggers, calendar-based triggers run on date arithmetic, and the categorised dashboard tells you what needs attention. Shared-aircraft co-owner invite is in early access; full role-scoped multi-user is coming, not yet shipped.

Pilot-owner maintenance under Part-ML — what you can and cannot do

Part-ML formalises pilot-owner maintenance: a defined list of simple tasks the pilot-owner can perform and certify themselves, without holding a Part-66 licence. The list is in the regulation (Appendix III to Part-ML); examples include changing the oil, replacing a tire, replacing a wheel bearing, replacing a battery, removing/installing the wheel pant, and similar tasks.

What you cannot do as pilot-owner: anything that requires Part-66 certifying staff. That includes most engine work beyond servicing, anything that touches structural or electrical certification, AD compliance that requires a certifying release, and the airworthiness review itself.

The administrative cost of pilot-owner maintenance is the recordkeeping. Each task, even an oil change, must be recorded in the aircraft logbook with date, hours, what was done, and your signature. Hangar’s flight-log entry includes a maintenance-event hook that lets you record pilot-owner work alongside the flight that triggered it; the hash-chained PDF export keeps the trail intact.

AD applicability — finding what applies to your tail

EASA ADs are published on the EASA AD-Tool. FAA ADs (relevant if you operate an N-registered aircraft) are on the FAA Dynamic Regulatory System (DRS). The hard part is not finding ADs — there are thousands. The hard part is matching them against your actual aircraft: serial range, model variant, equipment installed, sometimes installation date.

Hangar ships a 727-document service-document catalog with an applicability engine that does this matching against the aircraft you’ve configured. You enter the tail once; the system pulls the ADs that apply, recurring versus one-time, date-based versus landing-based. The monthly Cowork catalog-update workflow surfaces new documents in the Today feed.

For a deeper walkthrough of AD-tracking workflow, see AD compliance tracking for owner-pilots.

A 30-day onboarding checklist

If you’re standing up Part-ML compliance for a new (to-you) aircraft, here is a credible 30-day path. None of this is regulatory novelty; the value is the order.

Week 1 — inventory. Pull the current AMP (or last-known one). Pull the aircraft logbook. Pull engine and propeller logbooks. Pull the most recent ARC. Pull the AD compliance status as last recorded. Photograph the data plate and all installed equipment placards.

Week 2 — reconcile. Compare logged hours against the Hobbs and the tachometer. Reconcile component times. Identify gaps in AD recordkeeping; cross-check against EASA AD-Tool by serial. Identify any pilot-owner work that wasn’t recorded.

Week 3 — declare or get approved. If you’re going self-declared AMP, prepare the document and file it with your NAA. If you’re going CAMO/CAO, contract one; the AMP gets approved on their timeline.

Week 4 — set up the system of record. Whether that’s Hangar, a competitor, or a well-disciplined spreadsheet, set up the ledger that will hold flight hours, component times, maintenance events, AD compliance entries, and ARC date. Test the workflow by logging the next flight through it.

After day 30, the discipline is one or two minutes per flight to log it, an hour per quarter to verify the dashboard against reality, and the ARC cycle once a year.