The following is summarised from Radar in WWII by Henry E. Guerlac and an article ‘The Air Warning Service and The Signal Company, Aircraft Warning, Hawaii’ by Stephen L Johnston 20.
The strategic importance of Oahu was recognised in late 1939 and the Air Warning Service (AWS) was to provide warning of approaching enemy aircraft using the newly developed radar.
Extensive negotiations were needed as the sites, for the three SCR271s received in Hawaii on 3 June 1941, were located on land owned by either the Department of Interior National Parks Service or the Territory of Hawaii. In addition access roads, power supply, water supply, buildings et cetera had to be constructed – which occasioned even further delay. The net result was that none of the SCR271s had been installed by 7 December 1941 !
Six mobile SCR270Bs arrived in Hawaii on 1 August 1941 and were shortly thereafter put into operation because very little site preparation was required. Extensive testing of the sets was carried out in the next few months on installations at Kaaawa, Kawailoa, Waianae and Koko Head, Schofield Barracks and Fort Shafter.
On 27 September 1941 the SCR270Bs were tested in an exercise which, in retrospect, resembled to a remarkable degree the actual attack of 7 December. The exercise began at 0430 hours. Attacking planes were detected by the equipment at Waianae and Koko Head as they assembled near the carrier from which they had taken off 85 miles away. When they had assembled, the planes headed for Hawaii. The ‘enemy’ were clearly seen on the cathode ray tube and fighter aircraft were notified within about six minutes. They took off and intercepted the incoming bombers at about 25 miles from Pearl Harbour.
Under the control of the Signal Corps, Air Warning, Hawaii, the Schofield training SCR270B was moved to the site at Opana about two weeks before the attack on Pearl Harbour. The construction of a temporary Combat Information Centre (CIC) was in progress and training of the personnel at the centre was under way with reporting coming from six mobiles SCR270Bs. Ironically the program was to hand the CIC over to the Air Corps when the installation had been completed and the personnel had been properly trained – scheduled for about two weeks after Pearl Harbour.
A training period for operators of the SCR270Bs and the Combat Information Centre was scheduled for Sunday morning, between 0400 and 0700 hours, on 7 December 1941. There were two operators at the Opana site, George Elliot a recent transferee from the Air Corps, and Joseph Lockard. Because the supply truck did not arrive on time Lockard decided to give Elliott some more training on the SCR270B.
At 0702 hours a huge echo, almost due north of Opana at a range of 137 miles, appeared on the screen. Lockard immediately checked the equipment to ensure that it was functioning properly since it was a maximum size or saturation echo. Having established that it was indeed moving and needed to be reported, efforts were made to report it to the plotters at the Information Centre but these proved to be fruitless as the Centre had closed down. Eventually, on another phone, a Lt Kermit A Tyler was spoken to and he told Lockard not to worry even though it was a huge echo and travelling towards Oahu – mention was later made about a flight of B17s being expected.
Plotting continued until 0740 hours when the supply truck finally arrived at which time the aircraft had disappeared in the Permanent Echoes (PEs) at a range of 20 miles. These PEs were the result of back radiation from the antenna as the mountains were behind the radar set.
The unit was closed down, the men boarded the truck and proceeded towards Kawailoa for breakfast meeting another truck travelling at high speed towards the SCR270B. On reaching the camp they learned that Pearl Harbour had been attacked by the Japanese thereupon they realised that they had plotted the enemy approaching Hawaii for more than half an hour.
According to John Bennet’s “SIGNAL COMPANY, AIRCRAFT WARNING, HAWAII ORGANIZATIONAL HISTORY”, between Thanksgiving and December 3, 1941, these SCR-270B radar stations had been operated for a period of 24-hours a day. Then on December 4th, the SCR-270Bs switched to a different schedule. So on the fateful day of Sunday, December 7th 1941, Opana only operated from 3:00 AM to 7:00 AM, per order of the Headquarters, Hawaii District.