Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain BEECH Model 400, 400A, and MU- 300-10 airplanes. The existing AD currently requires installation of an improved adjustment mechanism on the flightcrew seats and replacement of the existing aluminum seat reinforcement assemblies with steel assemblies. This proposed AD would add airplanes to the applicability of the existing AD. This proposed AD results from reports of incomplete latching of the existing adjustment mechanism and cracked reinforcement assemblies, which could result in sudden shifting of a flightcrew seat. We are proposing this AD to prevent sudden shifting of a flightcrew seat, which could impair the flightcrew's ability to control the airplane.