Airworthiness Directives; McDonnell Douglas Model DC-8 Airplanes

The FAA is adopting a new airworthiness directive (AD) for all McDonnell Douglas Model DC-8 airplanes. This AD requires an inspection of the pushrod assemblies for the left and right elevator control tabs to determine if the pushrod assemblies are made of aluminum or steel, replacing any assembly made of aluminum with an assembly made of steel or modifying existing steel assemblies, and other specified actions. This AD also requires an inspection of the crank assemblies for the inboard and outboard geared tabs of the elevator to determine if the crank assemblies are made of aluminum or steel, replacing any assembly made of aluminum with an assembly made of steel, and other specified actions. This AD is prompted by an accident involving a DC-8 airplane. The probable cause of the accident was a loss of pitch control resulting from the disconnection of the pushrod for the right elevator control tab. The pushrod dropped down and jammed in front of the control tab crank, causing a large deflection of the control tab. We are issuing this AD to minimize the possibility of a control tab offset. A control tab offset could cause elevator deflection, an elevator airplane-nose-up condition, and reduced controllability of the airplane. This AD is also prompted by a report that the elevator on a McDonnell Douglas Model DC-8 airplane did not respond to command inputs from the flightcrew. We are also issuing this AD to minimize the possibility of crank assembly failure when the assembly is exposed to abnormal load conditions. Failure of a crank assembly could result in a jammed elevator and consequent reduced controllability of the airplane.