Page:CAB Accident Report, Eastern Air Lines Flight 663.pdf/23

Rh Since EAL 663 was turning away from the background lights of the Long Island shore into a black area, there was no horizon available to assist in the determination of the relative altitude of the target airplane. The single light source represented by PAA 212 provided an insufficient stimulus for the determination of depth and distance perception so that an intelligent decision as to vertical separation could not be made. Under these circumstances, it is likely that a descent was started, initially as a precautionary measure, which would give him a longer time to observe the other aircraft, and provide him with a measure of vertical separation. In this regard, it is noted that other pilots have testified that if they believed a collision course existed they would initiate a descent. The reasons given were that in climb the aircraft is limited in its maneuverability, and that the descent configuration would help keep the opposing traffic in sight. If a pilot does undertake an avoidance maneuver with inadequate information, he cannot tell what effect it will have on the probability of collision. Once he has begun the maneuver, he no longer has the fixity criterion, nor can he knows when to end the maneuver. This was the situation confronting the EAL pilot which would remain until approximately ten seconds prior to passage It is likely that initially the descent would appear to have EAL 663 proceed underneath PAA 212 and that there may have been a sight-line rate which would indicate that EAL 663 would pass to the east of PAA 212. However, at about ten seconds prior to passage, or some ten seconds after EAL 663 had started its descent, PAA 212 rolled rapidly to the right and also initiated a descent. That this maneuver might appear to the EAL pilot to again create an immediate collision hazard is evident in that it also appeared to do just that to the first officer of PAA 212. When this action took place and as it continued, the EAL captain, was left with no course of action other than a maximum effort right turn of his own, and possibly a pullup since the continued straight descent, or a left turn would further degrade the collision avoidance possibility. It is believed that this is the reason for the vertical right bank observed by the PAA 212 crew as EAL 663 passed. During the extreme right turn, the EAL captain would have no manner of knowing the actual attitude of his aircraft, or the degree of bank involved, since there were no visual clues available to him outside the cockpit In order to achieve spatial orientation after the two aircraft had passed, it would be necessary for him to again refer to his instruments, determine his attitude by reference to them, and apply the necessary recovery control pressures However, he would be operating in an unusual environment since 60 degrees is the maximum bank practiced in the DC-7 by EAL pilots in the course of their training. The maximum roll rate of the DC-7 is 26 degrees per second. At 2,600 feet in a vertical bank immediate and appropriate corrective action would be necessary in order to effect recovery. However, this action would have to wait upon the EAL captain's evaluation if his instruments in order for him to apply control pressures of the proper magnitude and in the proper direction In this context, an Air Force Study using highly qualified instrument pilots, disclosed that as much as 36 seconds were required for a pilot to establish full control by instrument