Page:CAB Accident Report, Delta Air Lines Flight 8715.pdf/5

- 5 - were capable of normal operation prior to impact.

Examination of the hydraulic system revealed:

Previous maintenance log pages did not indicate any pertinent system discrepancies.

The system repair at the Meletron switch location was subsequently checked and found to be free of leaks.

The hydraulic pressure regulator was functionally tested and found to operate within tolerance.

The hydraulic system by-pass lever was found in the down position. The by-pass lever installation was checked and the spring tension was within tolerance.

The capping of the hydraulic line to the Meletron switch did not adversely affect the normal operation of the aircraft's hydraulic system.

The emergency air brake pressure indicator read "O". The handle of the valve located above the left instrument panel had been pulled out of the body assembly by the left wing spar of the C-123B, thus opening the air pressure line to the bottle.

Analysis

The investigation revealed no evidence of hydraulic system, powerplant or structural failure. The aircraft and the crew were properly certificated, and weather was not a contributing factor.

Taxi instructions issued by the control tower and recorded on the tape indicate Delta 8715 was instructed to turn left at the second taxiway after passing the north-south runway. Referring to the diagram of the Memphis Airport, the air traffic control instruction to "turn left at the second taxiway" was misinterpreted by the captain. This placed the aircraft on Taxiway "D", in position for the subsequent collision with the C-123B.

The Board believes that the disconnecting of the Meletron switch was not a contributing factor in this accident inasmuch as this device was additional to, and did not interfere with, the normal operation of the basic hydraulic system.

The testimony indicated that the flight engineer in his pre-start check of the aircraft tested the emergency hydraulic pump selector valve in its three positions and then placed it in the "brakes only" position. He did not move the by-pass lever inasmuch as the positioning of this valve and lever was a part of the "before takeoff checklist". When the captain indicated an emergency the first officer reached for the by-pass lever near the floor of the aircraft to his left