ANA Skymaster Amana Crash - Subsequent Speculation About Cause of The Crash

Subsequent Speculation About Cause of The Crash

Investigators from the Department of Civil Aviation believed water in some of the fuel tanks of VH-ANA was responsible for rough running of one or more of the engines; and this ultimately led to intermittent failure of all the engines. The Inquiry led by Mr Justice Simpson found no evidence that there was significant water in the fuel tanks. No radio call was received from Amana to indicate the nature of any problem, or even that the crew was aware of a problem. The Inquiry concluded without determining the cause of the crash.

In the weeks and months after conclusion of the Inquiry one possible explanation of the crash began to circulate among employees of ANA. This possibility began with one piece of evidence uncovered by the Inquiry during cross-examination of ANA's ground staff. It was reported that after sunrise the morning after the crash the one-gallon container used to check Amana's fuel filters was found empty and lying on its side on the apron a short distance from where Amana had been parked. The Inquiry attached no significance to this evidence and did not explore it further.

Employees of ANA believed the container had last been used to drain fuel from the cross-feed drain cock, the fuel cock that serves the pipe in the wing centre-section for cross-feeding of fuel from tanks in one wing to engines in the other wing. Moments after this procedure commenced, the staff member was advised of a telephone call from his wife and he went to answer the telephone. With the cross-feed selector valves closed, little fuel ran out when the drain cock was opened. Some employees believed that because no fuel was running out neither the staff member nor anyone else noticed the drain cock was still open. Due either to the wind or the slipstream from Amana's propellers as it began to taxy prior to take-off, the almost-empty container was blown over and rolled some distance along the apron where it was found the next morning.

Some employees of ANA speculated that approximately ten minutes after take-off the crew of Amana were aware of the seriousness of rough running on number 4 engine so decided to shut it down. Company procedures specified that if an operational problem occurred prior to reaching Kalgoorlie, 290 nautical miles (540 km) east of Perth, the aircraft was to return to Perth; but if a problem occurred after reaching Kalgoorlie the flight could continue to Adelaide. The Douglas DC-4 was capable of flying from Perth to Adelaide with one engine inoperative. The crew of Amana on the fatal flight might have decided to wait until past Kalgoorlie before making a radio call to report one engine had been shut down, and then continue to Adelaide. In order to manage fuel usage and balance the weight of fuel across the wing, the crew might have selected some of the operating engines to draw fuel from number 4 tank. The DC-4 had a complex fuel selection system and, either deliberately or inadvertently, all operating engines might have been connected to number 4 tank. If the drain cock in the cross-feed pipe was still open to the atmosphere, air would be drawn into the pipe, causing an interruption of fuel supply to the engines, all engines to stop operating and their propellers to move to fine pitch. When the crew realised engines 1, 2 and 3 had all suddenly failed and that cross-feeding of fuel was the source of the problem they would have changed the fuel selections and restored fuel to the engines, causing the sudden screaming noise heard by witnesses as the engines burst back into life with their propellers in fine pitch. Amana had been flying at lower altitude than usual so there was inadequate height for the crew to arrest the high rate of descent before the aircraft struck high ground on the Inkpen family property. (At the Air Court of Inquiry, George Pape, representing ANA, described as "fantastic" any suggestion that the crew of the Amana would be cross-feeding fuel from one wing to the engines on the other wing at such an early stage of the flight.)

The Flight Superintendent and the Technical Superintendent of ANA simulated some of these events during a test flight in another DC-4. They were satisfied that the time intervals between events were compatible with the likely sequence of events leading to the crash of the Amana, and that it was a plausible explanation of the accident. However, on legal advice this possible explanation of the crash was not made public. Two accidents involving Douglas DC-4s, one approaching Dublin Airport, Ireland, in 1961 and another approaching Stockport Airport, Manchester, United Kingdom, in 1967 were attributed to interruption of fuel supply when engines were supplied from the cross-feed system which was open to an empty fuel tank, allowing air to be drawn into the cross-feed pipe.