Summary
This document proposes to adopt a new airworthiness directive (AD) that would apply to certain Twin Commander Aircraft Corporation (Twin Commander) 680, 681, 690, and 695 series airplanes. The proposed action would require installing a placard warning the pilot to observe turbulent air penetration speeds. Two accidents involving Model 690 airplanes where the affected airplanes encountered turbulence while descending at high speeds prompted the proposed action. The actions specified by the proposed AD are intended to prevent structural damage to the airplane caused by excessive turbulence, which could result in loss of the airplane.