Summary
We propose to adopt a new airworthiness directive (AD) for all Robert E. Rust, Jr. Model DeHavilland DH.C1 Chipmunk 21, DH.C1 Chipmunk 22, and DH.C1 Chipmunk 22A airplanes. This proposed AD would require a one-time inspection of the flap operating system for an unauthorized latch plate design installation. This proposed AD results from a report of a latch plate failing in service that was not made in accordance with the applicable de Havilland drawing. We are proposing this AD to detect and correct unauthorized latch plate design installation, which could result in an un-commanded retraction of the flaps. This failure could lead to a stall during a landing approach.