Twin Commander Aircraft LLC (Twin Commander) issued Maintenance Alert MA23001 on July 24, 2023 following two reports of cracks initiating at the radii of the lower wing skin cutouts for the main landing gear truss. These cracks were initially discovered on piston-powered aircraft conducting low-level surveys. There is a concern that such cracks might go undetected during routine maintenance, leading to continued cracking and reduction in wing residual strength. Maintenance Alert MA23001 recommends a recurring visual inspection, supplemented by either a high frequency eddy current inspection or a liquid penetrant inspection, of the skin cut-out area to detect any cracks within six months and annually thereafter. Since the issuance of MA23001, additional aircraft including turboprop models have been identified with similar lower wing skin cracking.
The FAA is interested in receiving any information on wing skin cracks at the MLG truss cut outs from owners, operators, mechanics, and maintenance personnel of the listed models of Twin Commander listed in the effectivity of this Airworthiness Concern Sheet (ACS). We recommend operators inspect these areas per Maintenance Alert MA23001 and provide information including:
- Aircraft registration and serial number
- Aircraft flight hours and flight hours at time of inspection
- Usage related to the aircraft’s industry sector and/or Public Use operations (e.g., low level survey, firefighting, medevac, agriculture, scenic flights, Department of the Interior, US Forest Service, etc.)
- Any positive or negative findings of wing skin crack length and location/orientation
- Available photos of crack findings
- Inspection methods utilized to locate the crack
