Douglas DC-6AB accident at Agana Navel Air Station, Guam, 19 Sept 1960

Accident narrative

On September 19, 1960, at approximately 0602 local time, a World Airways Douglas DC-6AB operating as Military Air Transport Flight 830/18 crashed into Mt. Barrigada shortly after takeoff from Agana Naval Air Station in Guam. The aircraft struck the mountain about two nautical miles from the departure end of runway 6L. Of the 94 occupants on board, seven crew members and 73 passengers received fatal injuries; one crew member and 13 passengers survived.

**The flight** Flight 830 was a passenger flight contracted by the Military Air Transport Service. It originated at Clark Air Force Base in the Philippines and arrived at Guam at 0150. The outgoing crew, commanded by Captain Rudy J. Holman, took over for the continuation to Wake Island, Honolulu, and California. Captain Holman had 15,681 pilot hours, including 2,548 in the DC-6. The crew consisted of eight people, including a Federal Aviation Agency employee.

During the turnaround, a hole and an "L" shaped fatigue crack were found in the aluminum skin of the vertical stabilizer. Pan American World Airways employees repaired it with a temporary fabric patch. The repairmen objected, stating a metal patch was proper, but completed the work at the insistence of the outgoing flight engineer. Captain Holman was present and, as far as could be determined, satisfied with the repair.

The aircraft's takeoff weight was 99,005 pounds, below the maximum allowable 103,000 pounds, and its center of gravity was within limits. Weather at 0600 was scattered clouds at 1,400 and 14,000 feet, a high overcast, and 15 miles visibility. It was a predawn takeoff; civil twilight did not begin until 0619.

**The sequence of events** The flight received its route clearance from Air Route Traffic Control (ARTC). The tower transmitted the climbout instructions: "right turn after takeoff, climb one zero zero degrees." The crew acknowledged the clearance and began the takeoff roll at 0600.

Witnesses observed a normal takeoff. The aircraft became airborne approximately 5,000 feet down the 7,986-foot runway. As it passed over a lighted construction area at the end of the runway, it was seen making an immediate shallow right turn and taking up a climb heading.

Approximately 50 seconds after takeoff, the aircraft struck trees on Mt. Barrigada at an elevation of 580 feet mean sea level, 300 feet higher than the runway. It cut a swath 975 feet long before coming to rest. Survivors reported that the initial impact was slight, but forces increased in severity before fire broke out. The sole surviving crew member, the navigator, recalled that all checklists were followed and nothing in the cockpit indicated an abnormal condition.

**What the investigation found** Investigators found that all wreckage was confined to the impact area. The landing gear and wing flaps were fully retracted. There was no evidence of structural failure, flight control malfunction, or in-flight fire prior to impact. The aircraft struck the trees in a slight right turn with an almost level longitudinal attitude.

The vertical stabilizer was relatively intact, though the fabric patch was missing. A search by helicopter and ground vehicles failed to locate it. The manufacturer reported that the repair would not have significantly affected the aircraft's flight characteristics or strength.

Engine teardowns and propeller governor tests revealed no pre-impact malfunctions. The Board believed the engines were delivering approximately 1,900 brake horsepower each at impact. Because of slight RPM variances, it is believed the crew had just completed the first power reduction to maximum except takeoff (METO) power. However, the cowl flaps were found in the full open position (22 degrees) rather than the required four-degree trail position. The Board noted this would have reduced the aircraft's rate of acceleration and climb, but not enough in itself to prevent clearing the terrain.

Investigators used a Navy helicopter and a U.S. Air Force C-54 to recreate the flightpath. By simulating the DC-6's V2 speed, they determined the flight time envelope was 50 seconds. A right turn with a 15-degree bank from the departure end aligned the C-54 exactly with the crash swath.

The investigation focused on the departure path. Published procedures for runway 6L required aircraft to climb straight ahead to a minimum of 1,000 feet before making a right turn. This restriction was printed in flight information manuals required to be on the airplane, and a large poster on the dispatch counter warned pilots of the rule. However, the ARTC clearance issued to the crew did not include this restriction.

Because the takeoff was made in darkness, the Board assumed the mountain's outline was not visible to the captain. A flashing red acetylene beacon on the summit was operating, but the Board questioned whether its low intensity would have alerted the crew in time to take evasive action. Following the accident, the Agana tower began advising pilots to climb straight ahead to 1,000 feet, ARTC began including the restriction in departure instructions, and the mountain beacon was replaced with a higher-intensity electric light.

**Probable cause** The Board determined that the probable cause of this accident was "the failure of the pilot to comply with published departure procedures applicable to runways 6 left and 6 right."