59-21-04\tBOEING: Applies to all 707-100 Series Long Body Airplanes. \n\n\tCompliance required as indicated. \n\n\tThe rudder characteristics of this airplane are such that when yaw angles in excess of approximately ten degrees are attained, the rudder effectiveness deteriorates quite rapidly with a resultant loss of aircraft directional control. Several incidents have shown that this can produce a dangerous flight condition. In order to minimize the probability of attaining these large yaw angles and to reduce the large rudder pedal forces needed for directional control, especially during flight with one outboard or both engines inoperative on the same side, the following must be accomplished at the next terminal where adequate facilities and personnel are available. \n\n\t(a)\tDeactivate the rudder feel spring installation. \n\n\t(b)\tThe emergency operating instructions section of the Airplane Flight Manual must be changed to include the following precautionary note: \n\n\tCAUTION. Therudder characteristics of this airplane are such that when side slip angles (yaw angles) in excess of approximately ten degrees are attained, the rudder effectiveness deteriorates quite rapidly with a resultant loss of directional control. In order to minimize the probability of obtaining large side slips (yaw angles) during flight with one outboard or both engines on one side inoperative, maintain directional control with the rudder and maintain this amount of rudder if turns are made. Do not use excessive aileron or bank angles to maintain directional control. Side slip angles (yaw angles) of approximately ten degrees result in nearly full aileron control to maintain heading when inadequate rudder is applied. This provides means for pilot recognition of inadequate rudder application. Therefore, if during engine-out operation, more than thirty degrees of control wheel rotation toward the operating engine are required to maintain straight flight or steady turning flight, then oneor more of the following corrective actions should be taken immediately: \n\n\t(1)\tApply additional rudder if available toward operating engines. \n\n\t(2)\tIncrease airspeed. \n\n\t(3)\tDecrease thrust on the operating engines side. \n\n\tNOTE: - There is a noticeable stiffening of rudder pedal forces during the last two or three degrees of rudder deflection; therefore, if any maneuver requires full rudder deflection; the pilot should be certain to depress the rudder pedal fully. \n\n\t(Boeing Service Bulletin No. 619 dated October 5, 1959, covers details relative to the deactivation of the subject rudder feel spring installation. Boeing Airplane Company will initiate changes to the emergency operating procedures of the Airplane Flight Manual.) \n\n\tThis airworthiness directive sent by telegram to all operators of Boeing 707-100 aircraft on October 9, 1959.