AD FAA-2007-28016

The FAA is adopting a new airworthiness directive (AD) for certain Learjet Model 31, 31A, 35, 35A (C-21A), 36, 36A, 55, 55B, and 55C airplanes, and Model 45 airplanes. This AD requires inspecting for unsealed gaps on the pylon side of the engine firewall and cleaning/ sealing any unsealed gap; and, for certain airplanes, inspecting for unsealed gaps of the pylon trailing edge and cleaning/sealing any gap. This AD results from a report that unsealed gaps (penetration points) of the engine firewall were discovered during production. We are issuing this AD to prevent penetration of flammable liquids or fire through the engine firewall into the engine pylon, which could lead to fire inside the airplane.