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How many revolutions per minute does the E-3A's rotodome make?
Short answer
Six: the E-3 Sentry's rotodome turns at 6 revolutions per minute. It measures 9.1 m (30 ft) in diameter and 1.8 m (6 ft) thick at the centre, held 3.4 m (11 ft) above the fuselage by two struts. The rotation is hydraulic and serves the AN/APY-1 or AN/APY-2 radar.
A nine-metre disc above the fuselage
The rotodome is unpressurised and measures 9.1 m (30 ft) in diameter, with a thickness of 1.8 m (6 ft) at the centre. Two struts hold it 3.4 m (11 ft) above the fuselage. The antenna system rotates by hydraulic means at 6 revolutions per minute.
What it scans on every turn
That hydraulic rotation of the antenna allows the AN/APY-1 or AN/APY-2 passive electronically scanned array radar to provide surveillance from the Earth's surface up into the stratosphere. Surveillance works over both land and water. Its pulse-Doppler radar has a range of more than 400 km (250 mi) against low-flying targets, at its operating altitude. The BTH pulse radar reaches about 650 km (400 mi) against aircraft flying at medium and high altitudes.
The computer that won the contest
Westinghouse's engineering team won the competition using an 18-bit programmable computer whose software could be modified before each mission.
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