Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Learjet Model 35, 35A, 36, 36A, 55, 55B, and 55C airplanes. This proposal would require installation of a placard on the instrument panel in the cockpit to advise the flightcrew that the Omega navigation system may be inoperative at certain engine speeds. This proposal is prompted by reports of loss of certain navigation signals during extended over water operation. The actions specified by the proposed AD are intended to prevent excessive deviation from the intended flight path due to loss of navigation signals, which could result in a potentially low- fuel condition or a traffic conflict.