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AIRPASS
AIRPASS was a British aircraft interception radar and fire-control radar system developed by Ferranti. It was the world's first airborne monopulse radar system and fed data to the world's first head-up display. The name is an acronym for "Aircraft Interception Radar and Pilot's Attack Sight System". In the Royal Air Force (RAF) it was given the official name Radar, Aircraft Interception, Mark 23, normally shortened to AI.23. AIRPASS was used on the English Electric Lightning throughout its lifetime.
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. This AIRPASS II was originally intended for the BAC TSR.2, but when that aircraft was cancelled in 1965, it was subsequently used in the Blackburn Buccaneer. 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.
Development of the monopulse radar underlying AIRPASS began in 1951 at Ferranti's Ferry Road location in Edinburgh. The AIRPASS system was announced to the public in late June 1958. It was initially tested on Douglas DC-3 TS423 (later civilian registered as G-DAKS) and later on an English Electric Canberra WJ643 for higher speed trials, replacing the nose sections of these aircraft. After testing use, WJ643 was renamed T.Mk 11 and used as a trainer aircraft for the radar operators of the Gloster Javelin. Several further T.Mk 11 were produced, but these mounted the AI.17 from the Javelin. The first flight on the English Electric Lightning took place on airframe XG312 on 29 December 1958.
It was initially linked to the de Havilland Firestreak air-to-air missile. It introduced the HOTAS (Hands On Throttle-And-Stick) system whereby the radar and gun sight controls were situated on the control column and throttle lever instead of elsewhere in the cockpit, eliminating the need for the pilot to take his hands off the controls while making an interception. The radar entered service with the RAF in 1960 in the English Electric Lightning interceptor.
The next version of the system was called AIRPASS II, or "Blue Parrot", and was a system optimised for use at low-level and originally developed for the cancelled BAC TSR.2 and subsequently used in the Blackburn Buccaneer.
AIRPASS was based on a magnetron source which provided pulses of about 100 kW peak. Pulses were about one microsecond in duration and sent 1000 times a second. To make the system as compact as possible, Ferranti invested in a numerical control system to mill the waveguides from single blocks of aluminium. The signal was sent and received from feedhorns that were split vertically to produce two outputs, one on either side of the reflector centerline. The reflector was shaped as two partial paraboloids, so that the two signals re-combined in space in front of the aircraft. The entire assembly was mounted on a servo system that allowed the antenna assembly to be pointed in two dimensions.
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. The monopulse technique requires the signals from the two channels to be compared in strength, so the output of the amplifiers must be precisely matched. This was accomplished with a highly advanced automatic gain control system with 100 dB range that adjusted the pulse-to-pulse outputs. To this point the system was entirely analogue, using miniaturized vacuum tubes cooled by forced air.
Behind the analog section was the analog computer portion of the system. 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. The system also read data from various aircraft systems like the altimeter and air speed indicator and combined this into the same display. The result was the world's first heads-up display, a concept that was soon licensed by US manufacturers.
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AIRPASS AI simulator
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AIRPASS
AIRPASS was a British aircraft interception radar and fire-control radar system developed by Ferranti. It was the world's first airborne monopulse radar system and fed data to the world's first head-up display. The name is an acronym for "Aircraft Interception Radar and Pilot's Attack Sight System". In the Royal Air Force (RAF) it was given the official name Radar, Aircraft Interception, Mark 23, normally shortened to AI.23. AIRPASS was used on the English Electric Lightning throughout its lifetime.
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. This AIRPASS II was originally intended for the BAC TSR.2, but when that aircraft was cancelled in 1965, it was subsequently used in the Blackburn Buccaneer. 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.
Development of the monopulse radar underlying AIRPASS began in 1951 at Ferranti's Ferry Road location in Edinburgh. The AIRPASS system was announced to the public in late June 1958. It was initially tested on Douglas DC-3 TS423 (later civilian registered as G-DAKS) and later on an English Electric Canberra WJ643 for higher speed trials, replacing the nose sections of these aircraft. After testing use, WJ643 was renamed T.Mk 11 and used as a trainer aircraft for the radar operators of the Gloster Javelin. Several further T.Mk 11 were produced, but these mounted the AI.17 from the Javelin. The first flight on the English Electric Lightning took place on airframe XG312 on 29 December 1958.
It was initially linked to the de Havilland Firestreak air-to-air missile. It introduced the HOTAS (Hands On Throttle-And-Stick) system whereby the radar and gun sight controls were situated on the control column and throttle lever instead of elsewhere in the cockpit, eliminating the need for the pilot to take his hands off the controls while making an interception. The radar entered service with the RAF in 1960 in the English Electric Lightning interceptor.
The next version of the system was called AIRPASS II, or "Blue Parrot", and was a system optimised for use at low-level and originally developed for the cancelled BAC TSR.2 and subsequently used in the Blackburn Buccaneer.
AIRPASS was based on a magnetron source which provided pulses of about 100 kW peak. Pulses were about one microsecond in duration and sent 1000 times a second. To make the system as compact as possible, Ferranti invested in a numerical control system to mill the waveguides from single blocks of aluminium. The signal was sent and received from feedhorns that were split vertically to produce two outputs, one on either side of the reflector centerline. The reflector was shaped as two partial paraboloids, so that the two signals re-combined in space in front of the aircraft. The entire assembly was mounted on a servo system that allowed the antenna assembly to be pointed in two dimensions.
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. The monopulse technique requires the signals from the two channels to be compared in strength, so the output of the amplifiers must be precisely matched. This was accomplished with a highly advanced automatic gain control system with 100 dB range that adjusted the pulse-to-pulse outputs. To this point the system was entirely analogue, using miniaturized vacuum tubes cooled by forced air.
Behind the analog section was the analog computer portion of the system. 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. The system also read data from various aircraft systems like the altimeter and air speed indicator and combined this into the same display. The result was the world's first heads-up display, a concept that was soon licensed by US manufacturers.