White Diamond DA40 NG registered SP-FAB parked on a wet apron, seen from the side, with the front canopy and the rear passenger door both raised open

Diamond DA40 Door Separations: What the New FAA Airworthiness Directive Means for Pilots

10 November 2026 · Pilot Sanchez

Passenger doors have come off DA40s in flight. What the new FAA AD requires, why the Canadian AD already applies in Europe and what to check before you fly.

The Diamond DA40 is a widely used training and touring aircraft in Europe, and it has a door problem that regulators have been trying to fix for years. On 2 November 2026 the US Federal Aviation Administration (FAA) published Airworthiness Directive (AD) 2026-22-06, which applies to every DA 40, DA 40 F and DA 40 NG. It was prompted by "several reports of passenger door separation during flight", and it requires a flight manual revision, inspections of the door and its latching hardware, new placards and, in some cases, replacement parts.

This post explains what the AD says, why it matters to pilots in Europe as well as in the United States, and what you can do on your next flight. It is a summary, not a substitute for the AD, the manufacturer's documents or your maintenance organisation.

What Has Been Happening

The DA40 has a large forward canopy over the front seats and a separate rear passenger door. The problem is the rear door coming away from the aircraft in flight.

This is not new. In October 2024 the FAA published an Airworthiness Concern Sheet on in-flight passenger door separations covering the DA 40 and DA 42 families. It explained that earlier ADs from 2010 and 2011 had already required an improved door retaining bracket and a change to the flight manual's open-door emergency procedure. Even so, since those ADs the FAA had received at least 20 reports of passenger doors separating in flight and more than 30 reports of aborted flights due to door malfunctions on the DA 40 and DA 42 fleets. In August 2024 Diamond issued Service Information Letters on correctly closing and latching the passenger door.

Transport Canada then issued its own AD, CF-2025-30, dated 23 June 2025. According to the FAA, Diamond attributed some of the separations to the passenger door not being properly latched, followed by attempts to latch it in flight. For the remaining cases Diamond could not find a definitive root cause. The FAA describes the risk as follows: a door separation "could result in damage to the airplane structure and lead to loss of control of the airplane and injury to persons on the ground".

What AD 2026-22-06 Requires

The AD takes effect on 7 December 2026. Within 100 hours time in service or 100 days after that date, whichever comes first, owners and operators must:

Revise the flight manual. Diamond's temporary revision "Door Latching and Locking" (TR-MAM-40-1203 for the DA 40 and DA 40 F, TR-MAM-40-1203/a for the DA 40 NG) changes the operating limitations, emergency procedures and normal procedures. Under US rules, an owner or operator holding at least a private pilot certificate may insert it and record it in the maintenance records.
Inspect the door. Aircraft with fewer than 100 hours total time in service on the effective date require a shorter inspection of the safety hook, latching bolts and front and rear door guide blocks. Those with 100 hours or more require the full inspection: the canopy and passenger door warning light, carbon hinges, safety hook and its mechanism, tension spring, retaining block, safety hook push button, latching mechanism spring, gas spring, latching bolts, door guide blocks and door frame, plus a measurement of the force needed to operate the door handle.
Install placards in line with Diamond's work instruction.
Fix what the inspection finds. Any findings listed in the work instruction must be corrected before further flight. If the door handle force reading is below 18 N (1.8 kg), the gas spring must either be replaced before further flight or, depending on a second reading, be re-checked every 100 hours and replaced within 12 months of the AD's effective date.

The work is defined in Diamond Mandatory Service Bulletin MSB 40-103 / MSB F4-042 / MSB D4-114 / MSB 40NG-084, Revision 2, of 5 June 2025, and its work instruction. Work done under Revision 0 or 1 of that bulletin before the effective date counts towards compliance. The FAA estimates the cost at US$85 per aircraft for the manual revision and US$331 per aircraft for the initial inspection, with replacement parts ranging from US$100 per aircraft for door sealant to US$824 per aircraft for a hook assembly. It notes that some costs may be covered under warranty. The FAA estimates that the AD affects 987 US-registered aircraft.

Newer Aircraft Are Not Exempt

Three of the four commenters asked the FAA to exclude newer serial numbers, arguing that a secondary safety latch on later aircraft had solved the problem. The FAA disagreed. Citing Diamond, it explained that both door handle configurations have a red safety hook, but that the hook "was not designed to hold the door closed during takeoff". The FAA added that the DA 40 NG, the latest model, "has experienced several occurrences of door separation".

The practical meaning for pilots is clear. The safety hook is a back-up, not a substitute for a properly closed and latched door.

The FAA also calls the AD an "interim action". Diamond is still investigating, and further rulemaking may follow depending on what it finds.

Does This Apply in Europe?

Yes. In substance, the same requirements were already in force in Europe before this FAA rule. The DA 40 is certified in Europe as an imported product under EASA type certificate data sheet EASA.IM.A.022, whose holder is Diamond Aircraft Industries Inc. of London, Ontario. That makes Transport Canada the authority of the State of Design. EASA explains that an AD issued by the State of Design for a product becomes valid in Europe on the day it takes effect, unless EASA issues a different decision, and that this applies to all State of Design ADs, not only FAA ones. In other words, the FAA rule is how the United States adopts the Canadian AD. In Europe, the Canadian AD itself is the one that counts.

There is one difference worth knowing. The Canadian AD also covers the diesel DA 40 D, which the FAA's version leaves out because that model has no FAA type certificate. In Europe, the compliance times are those of CF-2025-30, which became effective on 7 July 2025: within 100 hours air time or 100 days after that date, whichever came first, not the FAA's window that starts on 7 December 2026. If you fly a DA40 in Spain or anywhere else in Europe, your CAMO or maintenance organisation should be able to show you that CF-2025-30 is in the aircraft's AD status and when it was done. If you want the background on why a Canadian document applies to a European-registered aircraft, our post on who makes the rules of the air explains how the layers fit together.

What Pilots Can Do Now

Most of the AD is maintenance work, but Diamond linked several of the separations to how the door was closed. Most of these points come straight from the documents:

Read the new flight manual pages. Once the temporary revision "Door Latching and Locking" is in your aircraft's AFM, its limitations and procedures are the ones that apply. Fly the aircraft by the AFM, not by habit or by how you were shown years ago.
Treat the door as a checklist item you verify, not one you assume. The FAA's concern sheet points to Diamond's guidance on correctly closing and latching the passenger door. Check it yourself before takeoff, and check the door warning light. That light is one of the items the AD requires to be inspected. Use our VFR preflight briefing checklist to make the door, and who closes it, part of your routine.
Do not try to close the door in flight. The FAA's concern sheet reminds owners and operators that they "should not try to close the passenger door in flight", because the safety latch may disengage, the door may open and it may separate. Diamond itself linked some of the separations to attempts to latch the door in flight.
If the door is found unlatched, land. The same document says that when the passenger door is found unlatched, the pilot should "land as soon as practicable". That is easier to do if you have decided it before you go. The pull to carry on with the plan is real, and our post on plan continuation bias looks at why.
Brief your passengers. Tell anyone in the back not to touch the door handle in flight. The AD adds new placards, but a clear briefing before engine start still helps.

For owners and operators, the message is simpler still: make sure the applicable inspection is done within the compliance time that applies to the aircraft — the FAA's in the United States, those of CF-2025-30 in Europe — and that it is recorded in the aircraft's maintenance records.

Cover: Diamond DA40 NG SP-FAB at Friedrichshafen, Germany, with the canopy and the rear passenger door open. Photo: Alan Wilson, Wikimedia Commons, CC BY-SA 4.0, cropped.

Sources

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