A Diamond DA40 owner has a new directive to plan for this winter. AD 2026-22-06, published November 2, 2026 and effective December 7, applies to every DA 40, DA 40 F and DA 40 NG, whatever its serial number, after several reports of the passenger door separating from the airplane in flight. The work is a flight manual revision an owner-pilot can make, then an inspection of the door's latching parts, new placards and, depending on what a force measurement shows, a new gas spring.
What happened
Transport Canada, the authority for Diamond's DA40 type certificate, issued AD CF-2025-30 on June 23, 2025, and the FAA adopted the same requirements. Diamond traced some of the separations to a passenger door that wasn't properly latched and to attempts to latch it in flight. For the rest, in the FAA's words, Diamond "was unable to find a definitive root cause." Left alone, the FAA says, a door coming off could damage the airplane's structure and "lead to loss of control of the airplane and injury to persons on the ground."
The FAA calls the AD an interim action. The cause is still under investigation by Diamond, and more rulemaking may follow.
Newer airplanes are not exempt
Three people who commented on the proposal asked the FAA to leave out later serial numbers, which have a secondary safety latch. The FAA said no. Both door handle configurations have a red safety hook, it wrote, but that hook "was not designed to hold the door closed during takeoff," and the DA 40 NG, the latest model, has had several door separations of its own. The DA 40 D is covered by Transport Canada's AD but not the FAA's, because it has no FAA type certificate.
What the AD requires
All times run from December 7, 2026, and each is 100 hours time-in-service or 100 days, whichever comes first. One hundred days after December 7 is March 17, 2027.
- Paragraph (i)(1), the flight manual: add Diamond's temporary revision TR-MAM-40-1203, Door Latching and Locking (December 16, 2024, for the DA 40 and DA 40 F; TR-MAM-40-1203/a of February 18, 2025, for the DA 40 NG). It revises the operating limitations, emergency procedures and normal procedures. An owner or operator holding at least a private pilot certificate may make this revision and must record it in the maintenance records under 14 CFR 43.9(a) and 91.417(a)(2)(v). It may be done before the inspection.
- Paragraph (i)(2), airplanes with fewer than 100 hours total time on December 7: inspect the safety hook, latching bolts and front and rear door guide blocks, and add the placards.
- Paragraph (i)(3), airplanes with 100 hours or more: a longer inspection that also takes in the canopy and passenger door warning light, the carbon hinges, tension spring, retaining block, safety hook push button and mechanism, latching mechanism spring, gas spring and door frame; a measurement of the door handle's actuation force; and the placards.
- Paragraphs (i)(4) and (5), the gas spring: two force measurements decide it. If the second is under 1.8 kg (18 N) and the first was between 2 and 6 kg (20 to 60 N), the first check is repeated every 100 hours and the gas spring is replaced within 12 months of December 7. If the second is under 1.8 kg and the first was outside 2 to 6 kg, the gas spring is replaced before further flight.
- Paragraph (i)(6): anything the inspection finds is corrected before further flight.
The procedure is Diamond's Mandatory Service Bulletin MSB 40-103 / MSB F4-042 / MSB D4-114 / MSB 40NG-084, Revision 2, dated June 5, 2025, with its work instruction of the same number and date. Paragraph (k) gives credit for work already done under Revision 0 (March 20, 2025) or Revision 1 (May 15, 2025). Diamond asks for an execution report; the AD does not require one.
The cost
The FAA estimates 1 work-hour, $85, for the flight manual revision; 3 work-hours and $76 in parts, $331, for the first inspection; and $85 for each repeat inspection. If the inspection calls for parts, its figures are $659 for a gas spring, $824 for a hook assembly, $251 for a retaining block, $291 for door guide blocks and $100 for door sealant. The FAA says Diamond told it some of the cost may be covered under warranty.
What an owner can do now
Get Diamond's temporary revision and the service bulletin (the FAA lists Diamond's support at support-canada@diamondaircraft.com and 519-457-4041), make and record the flight manual revision, and book the inspection before March 17, 2027 or 100 hours, whichever comes first. An airplane whose inspection was already done to Revision 0, 1 or 2 of the bulletin should have that entry in its records; it meets the AD. Until then, the temporary revision's procedures are the ones to fly by.
On Hangar Flying: Directive Search finds airworthiness directives by part number, manufacturer or part; and MRO keeps an aircraft's maintenance records and what is coming due.
Sources
- FAA, AD 2026-22-06, Airworthiness Directives; Diamond Aircraft Industries Inc. Airplanes, final rule, Federal Register, November 2, 2026 (91 FR 68873), Amendment 39-23508, Docket No. FAA-2026-4633. Read in full November 10, 2026, in the Government Publishing Office's copy.
- Docket FAA-2026-4633 at regulations.gov, where Transport Canada AD CF-2025-30 and the comments are posted.
- Diamond Aircraft Mandatory Service Bulletin MSB 40-103 / MSB F4-042 / MSB D4-114 / MSB 40NG-084 Rev. 2, June 5, 2025, and AFM Temporary Revisions TR-MAM-40-1203 and TR-MAM-40-1203/a, as described in the AD. Diamond's documents; not reproduced here.
- 14 CFR 43.9 and 91.417, eCFR.
- FAA Aircraft Registry, N255DA, read November 10, 2026.
- Photo: Diamond DA40 NG Diamond Star (N255DA, cn 40.NC145)_(4-13-2024).jpg) by ZLEA, Wikimedia Commons, CC BY-SA 4.0, resized.