HMAS AE1 was an E-class submarine of the Royal Australian Navy (RAN). She was the first submarine to serve in the RAN, and was lost at sea with all hands near what is now East New Britain, Papua New Guinea, on 14 September 1914, after less than seven months in service. Search missions attempting to locate the wreck began in 1976. The submarine was found during the 13th search mission near the Duke of York Islands in December 2017.
Design and construction
The E class was a version of the preceding D-class submarine enlarged to accommodate an additional pair of broadside torpedo tubes. AE1 was long overall, with a beam of and a draught of . She displaced on the surface and submerged. The E-class boats had a designed diving depth of , but the addition of watertight bulkheads strengthened the hull and increased the actual diving depth to . The complement consisted of 34 men: officers and ratings.
The boat had two propellers, each of which was driven by an eight-cylinder, diesel engine as well as a electric motor. This arrangement gave the E-class submarines a maximum speed of while surfaced and when submerged. They carried approximately of fuel oil, which provided a range of at while on the surface and at while submerged. AE1 had four 18-inch torpedo tubes, one each in the bow and stern, plus two on the broadside, one firing to port and the other to starboard. The boat carried one spare torpedo for each tube. No guns were fitted.
In February 1911, defence minister George Pearce announced that orders had been placed with Vickers Limited for two submarines. AE1 was built at Barrow-in-Furness, England, having been laid down on 14 November 1911 and launched on 22 May 1913 and commissioned into the RAN on 28 February 1914. After commissioning, AE1, accompanied by , the other of the RAN's first two submarines, reached Sydney from England on 24 May 1914. Officers for the submarines were Royal Navy (RN) personnel, while the ratings were a mix of sailors drawn from the RN and RAN.
Deployment and loss
At the outbreak of World War I, AE1, commanded by Lieutenant Commander Thomas Besant, was part of the Australian Naval and Military Expeditionary Force sent to attack German New Guinea. Along with AE2, she took part in the operations leading to the occupation of the German territory, including the surrender of Rabaul on 13 September 1914. The submarine's involvement was recognised in 2010, following an overhaul of the RAN battle honours system, with the retroactive award of the honour "Rabaul 1914".
At 07:00 on 14 September, AE1 departed Blanche Bay, Rabaul, to patrol off Cape Gazelle with . When she had not returned by 20:00, several ships were dispatched to search for her. No trace of the submarine was found, and she was listed as lost with all hands. The disappearance was Australia's first major loss of World War I.
After the discovery of the submarine in December 2017, Rear Admiral Peter Briggs, retired, said the likely cause of its loss was a diving accident. He added:
, the best-supported theory for the submarine's loss was that it went below its crush depth due to a mechanical failure. Later that year, a team of researchers headed by the National Maritime Museum director Kevin Sumption concluded their investigation into the sinking of AE1. They concluded that a ventilation valve, which was likely open to make the tropical conditions a little more bearable while the submarine was cruising on the surface near the Duke of York Islands, was insecure when the submarine dived, causing a flood of the submarine's engine room and total loss of control of the AE1. The submarine subsequently sank below 100 metres and imploded, killing everyone on board instantly.
Searches for wreck
Beyond the search immediately after the submarine's disappearance, there were no concentrated efforts to locate the wreck of AE1 until the 1970s, when John Foster, a RAN officer working in Port Moresby, became interested in the story. After researching wartime records, Foster persuaded the RAN to deploy the survey ship HMAS Flinders in 1976. Flinders found one potential sonar contact, but did not have a sophisticated enough side-scan sonar to make a determination either way. During a deployment to Papua New Guinea in 1978, Flinders conducted several ad-hoc searches, again with no useful result. In 1990, while sailing between New Britain and New Ireland, Jacques Cousteau diverted his ship, Calypso, to investigate the potential contact found in 1976. His original plan was to investigate up close with a submersible, but mechanical issues prevented it, and Calypso instead performed a magnetometer search of the area, finding no wrecks.