Disaster DC-6 in Guam

Cargo Douglas DC-6A with registration number N90779 (serial number - 44914, serial - 646) was released on January 9, 1956 , and on January 11 was transferred to the customer - the American airline American Airlines . Its four piston aircraft engines were the Pratt & Whitney R-2800-CA15 and equipped with Hamilton Standard propellers, model 43E60, with hydromechanical propeller pitch control. On October 4, 1959, in Tulsa ( Oklahoma ), the aircraft underwent its fourth overhaul, having at that time an operating time of 10,398 hours. It was soon sold to another U.S. airline, World Airways , which was based at Auckland Airport , and entered on April 5, 1960. On April 14, on the basis of the Air Research Aviation Corporation in Los Angeles, the N90779 was converted from a cargo version to a cargo-passenger version (model DC-6A / B ). The liner operating time at that time was 11 631 hours 26 minutes, including 1233 hours 12 minutes from the overhaul, when it received a flight certificate and began to operate. At the time of the crash, the aircraft had a total operating time of 12,746 hours ^{[1] [2]} .

In the cockpit was a flight crew of 4 people ^[1] :

• The aircraft commander is 46-year-old Rudy J. Holman . He had a total flight experience of 15 681 hours, including 713 hours of instrument flight and 6343 hours of night flight. The fly-on type DC-6 was 2548 hours;
• The co - pilot is the 31-year-old Clayborne P. Clonch. He had a total flight experience of 6317 hours, including 266 hours of instrument flight and 4617 hours of night flight. The flight on type DC-6 was 217 hours 11 minutes, including 208 hours in the last 90 days;
• Flight Engineer - 29-year-old Robert E. Davis. Had a total flight experience of 5554 hours, including 748 hours on type DC-6, including 216 hours in the last 90 days;
• Navigator - 27-year-old Edgar W. Schwoyer ( Eng. Edgar W. Schwoyer ). He had a total flight experience of 3638 hours, including 258 hours on type DC-6, including 201 hours in the last 90 days.

Three stewardesses worked in the cabin ^[1] :

• Diddy H. Kaeger ( English Diddy H. Kaeger );
• Caroline Yates;
• Patricia Ellis ( English Patricia Ellis ).

An additional member of the crew was a representative of the Federal Aviation Agency Gerald Pease ( Eng. Gerald Pease ) ^[1] .

The N90779 was chartered by Military Air Transport Service for the passenger flight WO830 / 18 (callsign - World Airways 779 ) for transporting a group of military from the Philippines to California with intermediate landings on the islands of Guam , Wake and Honolulu . At 6:57 p.m. ^{[* 1]} on September 18, flight 830 left Clark Philippine air base and after seven hours of flight, at 01:50 a.m. landed at Agan air base (Guam) already on September 19. This flight went without deviations, and on Guam the liner received a new crew, which has been here since September 16 ^[3] .

Under the contract with World Airways, Pan American World Airways (Pan Am) was engaged in the ground handling of civilian aircraft and the preparation of passenger flights to Agan. The handing over crew on the plane had no comments, but in Guam, when viewed on a keel at the rear of the high-frequency antenna, an L-shaped hole was found in the skin. Upon closer inspection, it turned out that this was a fatigue crack, so the Pan Am aircraft technicians, while observing the flight engineer from the aircraft crew, performed a temporary repair by removing part of the skin with the crack and putting a patch of 18 square meters in this place. inches. The aircraft commander Holman also overseen the repair and was satisfied with it ^[4] .

A total of 86 passengers and 8 crew members were on board, including an employee of the Federal Aviation Agency , and the approximate weight of the liner at the time of takeoff was approximately 99,005 pounds (44 908 kg) with a maximum allowable for this flight 103 000 pounds (46 720 kg), which was determined on the basis that the landing weight on arrival at Wake should not exceed 86,780 pounds (39,363 kg). The centering of the aircraft was 23.5% of the SAH with established limits from 14.1 to 33% of the SAH ^[4] .

According to a weather forecast received by the crew from a Pan Am spokesperson, at 06:06 a variable cloud cover was expected with a lower boundary of 1400 feet (430 m ) and a variable cloud at 14,000 feet (4300 m ), high continuous, visibility 15 miles (24 km ), air temperature 77 ° F (25 ° C) , dew point 75 ° F (24 ° C) , southeast wind 5 knots, altimeter pressure altimeter 29.80 inches (757 mm) RT. Art. Civil morning twilight was supposed to begin at 06:49, and the sun rise only at 07:10. The scheme of departure from the Agan airfield provided that after taking off from the “6 left” lane, the aircraft had to rise to 10,400 feet (3200 m ), and then perform a right turn. A poster with this diagram was also at the control room, where the crew commander came to receive instruction. At the same time, the practice was widespread at the airfield itself, when crews perform this turn at least at an altitude of 1000 feet ^[4] .

Next, the crew contacted the take-off and landing controller and received permission to fly from him. Negotiations between the dispatcher and the crew themselves were not recorded, but the tape was recorded inside the control room, from which it was determined that the crew had received permission to follow the direct course to Wake at the level of 11,000 feet (3400 m ), and also instructed to take the right turn on course 100 ° and then switch to communication with the center at a frequency of 135.9 KHz. Then the dispatcher gave permission to take off, after which at 06:00 the crew began to take off ^[5] .

According to eyewitnesses, the aircraft performed a normal run along a strip of approximately 5,000 feet (1,500 m ), then took off and flew over a brightly lit construction site at the end of the strip, while eyewitnesses noticed how he immediately made a small turn and began to climb ^[5] .

After 50 seconds, flying at an altitude of 580 feet (180 m ) above sea level (300 feet (91 m ) above the level of the aerodrome), an airliner crashed into a covered vector 087 ° from the end of the strip two nautical miles from the aerodrome (three and a half kilometers) forest slope of the Barrigada mountain. Rushing 975 feet (297 m ) through the trees with an approximate course of 120 °, the Douglas stopped. According to the testimonies of the survivors, the impact on the trees itself was small, but then a strong fire broke out, which seemed to move from tail to nose. 13 passengers managed to escape through the fault on the left side of the cabin and through the emergency hatch above the right wing. Only the navigator who escaped through the window from the side of the co-pilot was able to escape from the crew ^[5] . All the remaining 73 passengers and 7 crew members, that is, only 80 people, were killed ^[3] .

In terms of the number of casualties at the time of the events, it was the largest plane crash in the Mariana Islands and with the participation of Douglas DC-6 ^[6] .

First of all, it was necessary to calculate the flight path of the N90779 board starting from the moment of separation from the strip in order to determine where he began to make a right turn to the 100 ° course. For this, a navy helicopter and a Douglas C-54 Skymaster air force aircraft were involved, roughly comparable to the crashed DC-6. The helicopter, hovering first over the crash site, began to follow the course of 280 ° to the airfield, that is, the opposite course of take-off 100 °, until it intersects with the continuation of the center line of the “6 left” strip. Then they began to check the flight path on a C-54 aircraft, following at a speed equal to the speed V ₂ for DC-6, and performing a turn at the point determined by the helicopter. It was found that the entire flight of flight 830 lasted only 50 seconds, and the right turn was carried out with a roll of 15 °. One of the residents east of the airfield claimed that the crashed plane flew right above his house, so investigators conducted flight tests trying to fly over the same house. As a result, the place of the turn and the roll with which it was carried out were confirmed ^[5] .

Attention was drawn to the repairs being carried out in Agan, since the patch was installed just at the horizontal stabilizers, which were separated from the aircraft. Later it was proved that the stabilizers separated when they hit the trees, but the patch was never found. A check of the engines showed that they rotated at a frequency of about 2550-2660 rpm, and the blades of their propellers were set at an angle of 34-36 °, that is, in the thrust mode. Fatigue destruction of propellers was not found. Sampling of fuel showed that it was in compliance with the standards and also could not lead to disaster. All debris was found at the scene. Thus, prior to this, for example, due to a collision with an obstacle during takeoff, there was no structural damage ^[7] .

Since takeoff was carried out at dawn dusk, much attention was paid to checking the operation of the lighthouse on the top of Mount Barrigada, into which the Douglas crashed. This lighthouse glows with a red flickering light and was installed on top of a tower 84 feet high (26 m ), that is, above the trees and various obstacles that could obscure it. This lighthouse burned for the entire short flight of flight 830, but its source of light was an acetylene gas burner, which gave a lighter glow than the red electric beacons located on the tops of some radio antennas, which were located slightly to the right of the flight path, but were aligned at the same height with an acetylene beacon, or 200 feet (61 m ) below it. However, it is worth noting that shortly after the incident, the acetylene torch was replaced by two electric lamps with a power of 600 W each, and together they shone with a brightness of 2000 candles , blinking at the same time with a frequency of 32 times per minute (controlled by a photocell) ^[7] .

The study of the nature of the destruction made it possible to determine that the plane crashed into the trees almost in a horizontal position and with a small right bank. Hitting a mountain at an altitude of 580 feet (177 m ) above sea level, the liner rushed up the slope 975 feet (297 m ), after which it stopped already at an altitude of 605 feet (184 m ) ^[7] . The landing gear and flaps were removed at that moment. The aircraft itself until the moment of impact on the trees, according to entries in technical journals, was fully operational. There was no fire or structural damage on board ^[8] .

Because of the darkness, the crew could not see the contours of the mountain, but had to know about it, because it was also indicated in the instructions for the flight, and the dispatcher warned him. In general, the take-off scheme from runway 6 is left, which, according to the representative of World Airways, was also in the flight data. First, it climbs up to 1000 feet (300 m ), and then turns east. But the commander, for unknown reasons, immediately made a turn, thus heading towards the mountain. The lighthouse on the top of the mountain, which was supposed to warn of danger, in this case was closed by predawn haze, which could not break through because of its weak light ^[9] .

To increase the flight speed and climb, the shields on the engine hoods should be opened only by 4 °, which is quite enough for the normal operation of the engines. However, when studying the wreckage, it was found that they were released at 22 °, which increased aerodynamic drag. However, if they were in the correct position, then the increase in speed would still not be enough to catch the mountain in time. Engines at the time of the accident developed a capacity of approximately 1900 liters. from. (1400 kW) each, and a small variation in their rotational speeds was caused by the fact that the engines just did not have time to normalize ^[9] .

The cause of the crash was the mistake of pilots who did not follow the established procedures for taking off from the “6 left” and “6 right” lanes of the Agan airfield ^[9] .

Comments

Sources

• WORLD AIRWAYS, INC., DOUGLAS DC-6AB, N 90779, AGANA NAVAL AIR STATION, GUAM, MARIANA ISLANDS SEPTEMBER 19, 1960 (inaccessible link) . Civil Aviation Council (12 July 1962). Date of treatment June 10, 2015. Archived January 29, 2016.