Introduction
The E120 Weather Radar system and its later development into the E160 system must be considered the pinnacle of valve technology weather radars and launched EKCO onto the world stage as a serious manufacturer of radar systems for civilian aircraft at a time when there was rapid expansion of passenger traffic coupled with the introduction of jets towards the end of the 1950's.
Development started in late 1951 following the successful development and flight trials of the 'military style' E38 system where valuable lessons were learned about cloud precipitation and the needs of the flight crews of passenger aircraft particularly their need to identify dangerous cloud formations such as cumulo-nimbus clouds.
The project was to take 4 years to reach the production stage, but when launched in the autumn of 1955 was arguably the best weather radar system available, probably only equalled by the RCA AVQ-10 system.
Principal Personnel
A development team was set up under the auspices of Jack Gard as head of Laboratory who assigned Jack Halsall as 'Project Engineer'.
Detailed below are the team and their areas of responsibility.
Jack Halsall – responsible for design of Transmitter/Receiver and EHT block.
John Smith - Junior Engineer - working with Jack Halsall on T/R.
Mike Rose- (Chippenham Mike Rose) gave support as a Laboratory Assistant to Jack Halsall.
Frank Burnill - Design Engineer responsible for E 120/E160 Synchroniser Unit and the Display Unit electronics.
Norman Wall – responsible for IF unit.
Jeff Saunders - responsible to Frank for the design of the display unit. Jeff also assisted Norman Wall with the design of the I.F. Unit.
George 'Gibby' Gibson – Chief mechanical Engineer – with assistance from Miss Jones was responsible for the Scanner unit.
Ian Walker – responsible for Transformer design.
Hugh Green Senior Waveguide Engineer (head of wave-guide lab)– responsible for Wave-guide development and design including 'German Toy' construction adopted for E160.
Frank Oxborough - Engineer, responsible for flight trials of E 120 / E 160, worked on Britannia and Comet installations as well as Servicing of the equipment with BOAC etc.
John Jewsbury - Responsible to Frank Burnill for work on the Synchroniser unit.
John also produced the first handbook for E 120. Organised and gave training courses on E 120 to BOAC. Serviced E 120 at various overseas bases, Singapore, Israel, Beirut and was also involved with aircrew training programmes.
Jim Mines - Lab. Assistant/ Wireman. Assisted Jack Halsall with prototype wiring on E 120 units and various modules in the T/R system including the EHT unit.
Bernard Price - Assisted Frank Oxborough in Britannia support including the Britannia's on the BOAC on Australia and Singapore routes both of which normally exhibited high levels of cumulo-nimbus activity and caused many engine shutdowns (see note below).
Support was also given to De Havilland. on the Comet II trials with E 120 and later on the Comet IV with both E120 and the later the E 160 derivative.
Editors Note.
An EKCO team routinely accompanied Bristol Aircraft on flight proving trials as well as airline familiarisation flights, which were not without incident since the Proteus engines fitted to the Britannia were prone to icing within the air intakes due in the main to the construction/design involving a 'S' shaped turn in the air inlet to the turbine. (Heaters were eventually fitted to stop ice particles/fragments entering the engines when the planes reduced altitude prior to landing).
EKCO personnel also participated on the De Havilland Comet IV Icing Trials, which was filmed by the EKCO film unit.
Choice of Wavelength – 'C' Band or 'X' Band?
At the time of the E120 development there was a considerable amount of scientific research and debate within the radar and meteorological world about the best frequency to detect harmful cloud formations where proponents of the 'C' band (5.5cm) were stating that this frequency was the theoretical optimum, which was a view supported by the American radar manufacturers.
This however was not borne out by the joint EKCO-RRE (Radar Research Establishment) flight proving trials in the late 1940's (flying many tropical routes with high cumulo-nimbus cloud activity), which showed that an 'X' band (3cm) system performed with no discernable loss of performance since heavy rainfall zones were limited in area, had better discrimination and suffered less range reduction in the presence of heavy precipitation.
The EKCO-RRE research and proving trials also showed that the optimum 'beam width' for target discrimination should be no more than 5 degree's in order to allow safe passage through turbulent conditions.
Additionally despite the few advantages offered by the use of 'C' band, by adopting 'X' band, this considerably eased the packaging of units by using smaller microwave components in the T/R unit as well as on the Scanner/Antenna. There was also a beneficial effect on the aircraft installation, both in terms of weight and size.
E120 System Technical Specification
The E120 System comprised 6 units, as follows: -
- The nose mounted Scanner unit E121
- The avionics tray mounted Transmitter/Receiver E122
- The avionics tray mounted Servo/Sync unit E123
- The cockpit mounted Indicator unit(s) E124
- The cockpit mounted Control unit E125
- The avionics mounted Back Plate Junction Box E126
The E120 system was an 'X' band system operating on a frequency of 9,375 Mc/s powered by a 60Kw magnetron pulsed at approximately 400pps producing a 2ms pulse with a beamwidth of 5 degree's. This provided a guaranteed scan range of 120 nautical miles.
Azimuth coverage was + 75° about the fore and aft axis of the aircraft with the elevation coverage (tilt upwards and downwards) being + 7° to – 17° from the normal stabilised scanning axis. The scanner unit was roll stabilised to + 45° in roll and +18° to – 22° in pitch.
Range: The system was calibrated to have the following range markers: -
- 0-20 nautical miles
- 0-60 nautical miles
- 0-120 nautical miles
The E120 system was also equipped with Iso- Echo Contour circuits to more accurately discriminate the degree of turbulence within cloud formations.
Iso – Echo Contour Briefly Explained
At the time of development, there was already evidence that the degree of turbulence within a cloud formation was related to the amount of rainfall within the cloud formation.
While an experienced operator could distinguish less dangerous cloud formations by their soft fuzzy appearance, there was a need to help aircrew discriminate and identify potentially harmful cloud formations, which should be avoided both for passenger comfort as well as the structural integrity of the aircraft (in extreme cases).
The Iso-Echo contour system display developed by EKCO for the E120/E160 system was a means to identify potentially harmful cloud formations and is best demonstrated by looking at two cloud formations, which to the naked eye can look similar and had equally intense peak precipitation levels.
Using the Iso-Echo circuitry, this not only looked at the peak precipitation levels, it also measured the rate of build up of the precipitation thus while the two cloud formations look similar, in one of the cloud formations the circuitry showed returns, which were sharper and had well defined edges, whereas in the second case the returns would show up as considerably less well defined.
The cloud formation with the sharp well-defined edges showed that there was considerably higher rate of build up, which in turn meant that this cloud formation should be avoided at all costs although best practice also recommended that both cloud formations be avoided and using the weather radar, a course plotted to avoid both.
