BeechTalk - BT - Turbo Twin Commander Tail Cracks

Username Protected · **Posted:** 31 Aug 2025, 15:30

Not “new news” but does anybody know if this will turn into a new airworthiness directive? Is it a real issue or just firefighting commanders that have been abused?

From FAA Safety Airworthiness Concern Sheet:

• Affected aircraft:
• Model aircraft: Twin Commander 685 (serial 12000–12066), 690 (11000–11079), 690A (11100–11344), 690B (11350–11566), 690C (11600–11735), 690D (15001–15042), 695 (95000–95084), and 695A (69001–96100).

• Reason for concern:
• The original AD 95-13-02 required inspection of FS 409 and adjacent vertical stabilizer skin to prevent failure.
• SB 218 provided modifications to resolve those areas.
• Despite these measures, cracking persists—not only in the original zone—but now also in frames FS 386 and FS 429, and in locations that are visually inaccessible, even with the access panels from Service Letter 345.

• Cracking locations:
• FS 386: Shear web, horizontal brace, cable cutouts, diagonal brace
• FS 409: Horizontal stabilizer front spar, vertical stabilizer spar web, corner fillet radii, stabilizer web, frame tangs, fuselage skin
• FS 429: Frame channel and web, forward frame
• Vertical stabilizer skin: Repair doubler, mid-spar flange

It highlights that Service Letter 345’s inspection panels may not provide sufficient access, and more extensive access work is often necessary.

Username Protected · **Posted:** 31 Aug 2025, 16:01

The full document, dated May 27, 2025, notes that:

Quote:

This Airworthiness Concern Sheet (ACS) is intended as a means for FAA Aviation Safety Engineers to coordinate airworthiness concerns with aircraft owners/operators through associations and type clubs. At this time, the FAA has not made a determination on what type of corrective action (if any) should be taken. The resolution of this airworthiness concern could involve Airworthiness Directive (AD) action or a Special Airworthiness Information Bulletin (SAIB), or the FAA could determine that no action is needed at this time. The FAA’s final determination will depend in part on the information received in response to this ACS.

The FAA endorses dissemination of this technical information to all manufacturers and requests association and type club comments.

The ACS adds:

Quote:

Cracking has been reported on airplanes operating in both part 91 and 135 operations, with a broad range of airplane flight hours. Airplanes with current or previous operation within the United States Forestry Service USDA or similar firefighting support roles may be more susceptible to the development of cracks in these areas. In March of 2019 the USDA’s Office of Aviation Services released an interagency aviation safety alert with information on cracks discovered during routine inspections in the vertical fin attachment (FS 386).

Turbo Twin Commander Tail Cracks - FAA Airworthiness Concern