United States of America

The primary cause of this accident was due to Operator Error in that the pilot descended below minimums in such a manner that the aircraft struck trees, and subsequently became doubtful of his position to the point of being lost due to failure to use all approach and navigational aids which further compounded his emergency. Although it is primarily the responsibility of the aircraft commander for the safe conduce of flight, it is also the duty and responsibility of the co-pilot to advise the pilot in sufficient time, prior to reaching minimums or a dangerous condition to allow him to check the rate of descent so as not to descend below minimums or hit the ground or obstructions. The pilot failed to adequately brief the flight crew for the type of approach to be made and missed approach procedures for that particular approach.

It is believed that the accident was the consequence of a controlled flight into terrain.

The probable cause of this accident was the full retraction of the wing flaps at low altitude during a circling approach without necessary corrective action being taken by the crew. Considering that very little altitude was gained after the application of power it is probable that a circling approach had been decided upon when the left turn from runway 14 was made. Since the wing flaps during the circling approach would be extended 20 degrees, and since they were found in the fully retracted position, it is believed that they were retracted shortly before impact. Fully retracted wing flaps at this time would explain the feeling of experienced by the off-duty flight crew member.

It was concluded that the primary cause of the accident was pilot error in attempting a no-flap take-off. It was also concluded that the pilot and copilot did not take corrective action soon enough during take-off to successfully abort the take-off.

Loss of a propeller blade on engine number two.

The Board determines that the probable cause of this accident ins loss of power on the left engine and the drag-induced effect of the unfeathered left propeller, resulting in loss of directional control daring an attempted go-around. The following findings were reported:
- During approach to the airport serious malfunctioning of the left engine occurred,
- An improperly planned final approach resulted in runway misalignment and necessitated a go-around,
- During the attempted go-around the left engine rear master rod bearing failed resulting in loss of power on the left engine,
- The propeller was not feathered for single-engine operation,
- The lack of left engine power at low at low airspeed, and the drag resulting from the unfeathered left propeller resulted in loss of directional control,
- During the resulting left turn the aircraft was stalled and entered an "over-the-top" spin.

It was reported that weather conditions were poor at the time of the accident with thunderstorm activity around the McGuire Airbase, a horizontal visibility of 1,500 meters, clouds from 600 to 1,800 feet and wind gusting up to 30 knots with turbulences. The assumption that the aircraft encountered strong downdraft caused by a micro-burst was not ruled out.

The Board determines that the probable cause of this mid-air collision was that the pilots did not see each other in time to avoid the collision. It is not possible to determine why the pilots did not see each other, but the evidence suggests that it resulted from any one or a combination of the following factors: Intervening clouds reducing time for visual separation, visual limitations due to cockpit visibility, and preoccupation with normal cockpit duties, preoccupation with matters unrelated to cockpit duties such as attempting to provide the passengers with a more scenic view of the Grand Canyon area, physiological limits to human vision reducing the time opportunity to see and avoid the other aircraft, or insufficiency of en route air traffic advisory information due to inadequacy of facilities and lack of personnel in air traffic control. The following findings were reported:
- Approaching Daggett, TWA 2 requested its company radio to obtain 21,000 feet as an assigned altitude, or 1,000 on top,
- Company radio requested 21,000 feet IFR from ARTC. This vas denied by ARTC. Request was then made for 1,000 on top. This was approved and clearance issued. The flight climbed to and proceeded at 21,000 feet,
- As an explanation for the denial of 21,000 feet, TWA 2 was furnished pertinent information on UA718,
- The last position report by each flight indicated it was at that time at 21,000, estimating the Painted Desert line of position at 1031,
- The Salt Lake controller possessed both position reports at approximately 1013, at which time both flights were in uncontrolled airspace,
- Traffic control services are not provided in the uncontrolled airspace and according to existing Air Traffic Control policies and procedures the Salt Lake controller was not required to issue traffic information; none was issued voluntarily,
- A general overcast with some breaks existed at 15,000 feet in the Grand Canyon area,
- Several cumulus buildups extending above flight level existed; one was nearly over Grand Canyon Village and others were north and northeast in the area of the collision,
- The collision occurred at approximately 1031 in visual flight rule weather conditions at about 21,000 feet,
- The collision in space was above a position a short distance west of the TWA wreckage area, 17 miles west of or approximately 3-1/2 minutes' flying time from the Painted Desert line of position,
- Under visual flight rule weather conditions it is the pilot's responsibility to maintain separation from other aircraft,
- At impact the aircraft relative to each other converged at an angle of about 25 degrees with the DC-7 to the right of the L-1049. The DC-7 was rolled about 20 degrees right wing down and pitched about 10 degrees nose down relative to the L-1049,
- There was no evidence found to indicate that malfunction or failure of the aircraft or their components was a factor in the accident.