Summary
This document proposes to adopt a new airworthiness directive (AD) that would apply to Twin Commander Aircraft Corporation (Twin Commander) Models 500, -500-A, -500-B, -500-S, -500-U, -520, -560, - 560-A, -560-E, -560-F, -680, -680-E, -680FL(P), -680T, -680V, -680W, - 681, -685, -690, -690A, -690B, 690C, -690D, -695, -695A, -695B, and 720 airplanes. This proposal would require revising the FAA-approved Airplane Flight Manual (AFM) to specify procedures that would prohibit flight in severe icing conditions (as determined by certain visual cues), limit or prohibit the use of various flight control devices while in severe icing conditions, and provide the flight crew with recognition cues for, and procedures for exiting from, severe icing conditions. The proposed AD is prompted by the results of a review of the requirements for certification of these airplanes in icing conditions, new information on the icing environment, and icing data provided currently to the flight crew. The actions specified by the proposed AD are intended to minimize the potential hazards associated with operating these airplanes in severe icing conditions by providing more clearly defined procedures and limitations associated with such conditions.