Summary
This document proposes to rescind an existing airworthiness directive (AD), applicable to certain Learjet Model 35, 35A, 36, 36A, 55, 55B, and 55C airplanes. That AD currently requires 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. That AD also provides for an optional installation of certain band reject filters, which eliminates the need for the placard. The actions specified by that 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. Since the issuance of that AD, use of the Omega navigation system has been permanently discontinued; therefore, the original unsafe condition no longer exists.