After the end of WW2, Sydney Camm, (the designer of the famous Hawker Hurricane) and his team set to work on an aircraft, which was given the company designation Type 1067 and the new design took shape in late 1948. Metal was cut for the first prototypes in late 1949 with the first aircraft being finished in July 1951. This aircraft being named the Hawker Hunter.
The new aircraft took shape around some design features necessitated by the intended equipment for the fighter's role one of which was the need for a Radar Ranging unit to be positioned in the nose, meaning the engine air intakes were moved to the wing roots and this to a large extent dictated the aircrafts overall shape.
To complement the excellent Ferranti gunsight, where good as it was, it was felt that with the increased performance offered by the Hunter, the Ferranti gunsight performance could be enhanced by a Radar Ranging Unit, which could display range information onto the gunsight graticule through a collimator lens system.
Collimator Lens System and Ferranti Gunsight courtesy Mark Gauntlett
In essence the main limitation of the Ferranti gunsight was the inconvenience and poor accuracy of the optical range measurement. This relied on the pilot manually adjusting a visual pattern of diamond dots until they just outlined the perceived wingspan of the target.
This adjustment controlled the precession of a gyro-stabilised mirror, which projected the offset sight line to correct for target motion. It was a pretty crude range measurement as changes in both the target wingspan and its attitude altered the apparent range.
Adding the Radar range input both reduced the pilot load in a combat situation and provided a major improvement in accuracy. No Radar display or separate lock-on indicator was necessary because the Radar range input also controlled the size of the ring pattern of diamonds which the pilot could see correctly surrounding the target.
Although detection was possible at a considerably greater range, the system operated over the range interval 200 to 800 yards, as this was the optimum firing range for the weapon system.
When a target was found, the radar locked onto it and lit the green light on the right hand side. The adjacent Amber light was lit when the target was within the pre-determined firing range.
When no target was present, the system continuously slowly cycled its range strobe over the range interval. The search range used was nominally set for 200yds to 1500yds although the system was theoretically capable of a maximum range of 10Km under ideal conditions.
This range strobe information was also fed to the gunsight so the pilot could see the size of the ring pattern continuously changing as the Radar searched for a target.
As soon as the strobe found a target both the strobe and the ring pattern remained locked at target range.
The pilot had a 'Target Rejection' switch in the cockpit, which over-rode the lock on and unlocked the radar thus allowing to the radar to restart the search cycle. Additionally there was a cockpit control 'Radar Presentation' switch, which was used to disconnect the radar from the ranging mechanism if for example the target was using ECM such as 'chaff'. Note: - only one target could be tracked at a time.
EKCO were awarded a contract by TRE by now renamed as RRE (Royal Radar Establishment) in late 1949 to develop the system although it was early 1953 before the 'A' and 'B' models were available
The system was designated Radar Ranging Mark 1 and given the official designation ARI 5820.
Installed system courtesy Mark Gauntlett
EKCO Radar Ranging Mk 1 description and team
The TRE team for this contract was Jerry Steer and Tom Holland who both became regular visitors to Ekco Malmesbury. The EKCO engineering team was headed by VJ Cox and the project leader was Cyril Drew.
The system consisted of two main units - Transmitter/Receiver (XMTR) and ranging unit. These were contained in cylindrical pressure cases, which in turn were mounted in 'wind tunnels' to enable cooling air to flow around the sealed units. These complete units were then mounted onto 'an aircraft-mounting tray'.
Cyril Drew was responsible for the design of the Transmitter/Receiver and Ray Reeves the Ranging units. One of the team working under Cyril Drew was Bill Graville.
In developing the system, the team were able to make use of the Transmitter/Receiver already developed for the first Weather Radar (the E38 system) although this unit was modified for this task. The system was an X band system.
Note: Careful attention had to be given to cooling the system and an ingenious solution was developed by TRE in conjunction with Hawkers, which used cooling slots taking 'ram air' from the radome and an exhaust duct at the rear of the radome.
In developing the XMTR, there were a number of sub-units and people involved such as:-
- IF Amplifier - designed by Normal Wall.
- Wave Guide Assemblies - designed by Hugh Green's department.
- Transformers etc, - produced in Vic Cook's department.
- Wiring and Assembly work from Development Assembly Department - Dennis Ricketts in charge.
- Various wiremen including Jim Bailey and Bert Ball.
- Development Inspection - Roy Henstridge, Bob Ward etc.
- D/O - Jack Tims, Horace Fowler, Johnny Radlett etc. etc.
- George 'Gibby' Gibson - Chief Mechanical Engineer in overall charge of design of pressure cases, wind tunnels, mounting trays etc.
The system used a British version of the American 2J42 magnetron, which was rated at 10Kw output power. Because of this it was often referred to as a 10Kw system. However, because of the inherent losses in the wave-guide duplexing system and magnetron tolerances 7Kw was a more realistic figure.
Radar Ranging was standard fit it almost all standard Hunters and Hunter variants. It was very much a money-spinner for EKCO and was to become EKCO's best selling Radar system through the 50's with the company making circa 2000 sets plus associated test gear. Towards the end of its production run the system was also manufactured under licence in India for their Hunters albeit that the units were made in Malmesbury, then broken down into major sub-assemblies - for re-assembly in India.
Radar Ranging was originally designed for both the Hunter and the Supermarine Swift however in trials the Hunter proved superior so this was selected as the front line fighter of the day.
Interestingly the Supermarine Swift became the principal trials aircraft for 'Blue Sky/Fireflash when this system was being worked up for service introduction before the project got cancelled.
Below is an installation schematic for Radar Ranging Mk 1 taken from the AP manual of the time.
