Control Towers Part 1 (1937-1946)
by Roger Meyer
The control tower the tip of the Air Traffic Control (ATC) iceberg has long been the icon that identifies an airport. From a simple glass-sided box on top of the aero club building to the 1995 landmark tower at Sydney Airport, the evolution of the control tower conveys an interesting story. A photographic essay of control towers would show very few which are alike, despite the fact that they all perform the same basic function.
The history of the control tower in Australia began in February 1937, when the Civil Aviation Board appointed Aerodrome Control Officers at Sydney/Mascot, Brisbane/Archerfield and Melbourne/Essendon aerodromes. The function of these officers was to regulate and control air traffic in the vicinity of their aerodromes to prevent collisions, to coordinate the radio and meteorological services provided for regular air services and to give assistance to pilots engaged in local and long distance flights.
While there were already aircraft inspectors, ground engineers and groundsmen at these aerodromes, they had little time to supervise aircraft movements, and also lacked appropriate training.
The personal qualities required of Aerodrome Control Officers were mature age, discipline, power of command and level-headedness. The salary range was £306 - £384, being slightly above that of a Rifle Range Superintendent. The first appointments were: Commander H.T. Bennet and Flt. Lt. A.A. Poole (Mascot); A.V. Lauchland (Archerfield); and Sq.Ldr. A.E. Hempel (Essendon).
These officers performed their collision avoidance duties within the movement area of their aerodromes from temporary elevated towers. At Mascot and Essendon, these towers took the form of a glass box on top of the Aero Club, while at Archerfield it was a separate structure.
As this was in the era when few aircraft carried radio communications equipment, all contact between the Control Officer and the pilot had to be by visual signalling from the tower. The tools-of-trade were an electric Aldis lamp and a Very flare pistol. The Controller would aim the lamp, through its telescopic viewfinder, at an aircraft up to two miles away. If no signal was given, the aircraft was clear to land, but a white light from the tower was necessary before the aircraft could proceed to its parking place after landing. If it was necessary at any time to prevent all planes from landing and to go around again, the controller would fire a succession of red cartridges from the Very pistol. To restore the clear-to-land condition, a series of green cartridges were fired. Again, a red lamp would warn the pilot of a departing aircraft to hold his position and a green lamp would clear him for take-off. Messages from the few aircraft equipped with radio were received by Aeradio and relayed to the Aerodrome Controller.
Another visual aid was the Signalling Square. This was a sealed area of ground in front of the tower on which were arranged symbols, visible from the air. These symbols indicated the state of the aerodrome, wind strength and direction, and taxying information.
The tower carried other visual indicators to pilots. Based on RAAF procedures, the controller would hoist spherical red or yellow cane balls from the tower structure to indicate whether the tower was manned, and therefore if there was control over aerodrome movements at the time.
In 1940 DCA constructed administrative/terminal buildings at Mascot, Adelaide/Parafield and Archerfield aerodromes. On the top floor was located Aeradio and the ATC Area Control Centre, while in front and facing airside was the control tower cabin. The tower had a curved wall, constructed almost entirely of glass, and stood proud of the building line for maximum field of vision.
Plans for the Maylands (Perth) and Cambridge (Hobart) buildings were not implemented due to wartime stringencies, and temporary structures were erected in lieu. (A retired controller recalls that the windows in the Cambridge tower faced the wrong way!).
During World War II, the air forces, particularly the USAAC, established control for military purposes at many existing and new aerodromes in Australia. After the wars end in 1945, DCA took over the control towers and their equipment at Bankstown, Cairns, Canberra, Cloncurry, Darwin, Eagle Farm, Madang, Rockhampton, Townsville and Wagga Wagga. These towers have since been replaced.
At Essendon a new tower, designed by mechanical engineer Marshall Fordham, was constructed in 1946, and boasted a fresh water tap on the balcony. Access was via a two-section steel ladder, without any shelter from the weather. While the visual signalling devices were retained for aircraft without radios, high frequency communications were now available. (VHF was progressively introduced in 1949, but HF remained in towers for light aircraft until the 1970s). The tower had a rudimentary two-man control console with direct communications to other operational positions, receivers, telephones, meteorological instruments and equipment to cope with an aerodrome emergency.
Another novel device in the new tower was an in-house invention - the Automatic Runway Selector. It was the idea of aeronautical engineer, Mr Icko Tenenbaum, and gained international interest. Simply stated, it comprised a field wind speed and direction sensor, connected to Selsyn motors in the Automatic Runway Selector display unit. This produced a moving light source under a chart which showed the maximum allowable cross-wind for a given aircraft type. If the light beam was beyond the limits of the chart, another runway had to be used.
The Essendon Tower, while a vast improvement on the original box atop the Aero-Club, had its shortcomings. On one occasion staff wrote to Head Office complaining of having to stand ankle-deep in water due to the rain leaking in. The response was to offer a supply of waterproof coats and gumboots. On another occasion, the aerodrome was declared closed due to fog. Hours later, aircraft were still awaiting take-off clearance when it was discovered that steam from the kettle in the tower had condensed on the inside of the window, giving the controller the illusion of fog, while the sun was shining brightly outside.
Problems such as these would soon be overcome with the next generation of tower design and facilities.
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