AIRPASS

The basic AIRPASS electronics system was later adapted as the basis for a terrain-following radar for navigation and targeting for air-to-ground attacks.

Elements of the AIRPASS design were used on many subsequent radars from Ferranti, while its head-up display was licensed for use in the United States, where it was quickly adopted for many aircraft.

It was initially tested on Douglas DC-3 TS423 (later civilian registered as G-DAKS)[2] and later on an English Electric Canberra WJ643 for higher speed trials, replacing the nose sections of these aircraft.

[6] On reception of a pulse, the signal was sent into a klystron local oscillator and then into two conventional superheterodyne receivers with an intermediate frequency of 30 MHz.

This was accomplished with a highly advanced automatic gain control system with 100 dB range that adjusted the pulse-to-pulse outputs.

This took the outputs from the radar system, calculated the proper intercept course based on the selected weapon, and presented the results in the reflector gunsight mechanism.

In the late 1950s,[7] Ferranti won the contract to supply radars for the Blackburn Buccaneer aircraft in Royal Navy service.

This version, AIRPASS II (also known by the rainbow codename Blue Parrot),[8] was modified to handle low-level scanning by eliminating the reflections from waves.

Since the waves reflected away much of the signal, to make up for these losses the new version used a more powerful 250 kW transmitter and a larger Cassegrain antenna.

[9] The idea was simple; the computer calculated a ski-ramp shaped ideal trajectory, flat directly under the aircraft and then sloping upward in a gentle curve.

The radar scanned in a U-shaped pattern, taking accurate measurements of the altitude and range to objects in front and slightly to either side of the aircraft.