EUREKA BA [Main Title]

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  • Title: EUREKA BA [Main Title]
  • Film Number: AMY 468
  • Other titles:
  • Summary: A technical instructional film with extensive use of animated diagrams, illustrating the basic principles and uses of the BABS Mark II "Eureka" radar system that uses a ground based transponder and an airborne transceiver for aircraft navigation purposes. It can operate in conjunction with the Rebecca or Lucero airborne transceivers, but in this film an improved version of Eureka is demonstrated in conjunction with the H2S radar system installed in a Lancaster aircraft.
  • Description: Part one: The first part of the film covers the basic principles of Eureka. While the fundamental principles of the system remain unchanged from earlier versions, advances in electronics and the development of adjustable ground based antennae have resulted in more precise systems that also provide the navigator with information about his position with respect to the landing runway vector or QDM. The ground equipment for Eureka is installed in a small van accurately positioned at the far end of the runway in a static wooden frame. The transmitter, receiver and monitors are installed inside the van. The rear of the van incorporates two square wooden cones that may be rotated about the axis of their respective apex to form the transmitting and receiving antennae. This system provides two areas or cones of radiation which overlap. The signal from the left cone is strongest to the line QDM, decreasing rapidly to either side. The right cone is an image of the left and the two cones are adjusted to give a narrow equisignal 1 degree beam extending from the far end of the runway in the direction of the reciprocal runway vector (QDM). Either side of the 1o vector are vectors of 2 degrees, 5 degrees, and 12.5 degrees whose signal strength is derived from the field strength of the left and right antennae. The sectors to the left are divided into dashes (long pulses) and those to the right in dots (short pulses). To use the Eureka system, the navigator in the Lancaster switches on the Lucero transceiver and monitors the returned signal on the H2S display which appear as broad and narrow pulses (blips) of varying amplitude, from which the sector and range can be determined. By modifying the pulse duration an aircraft can determine the deviation of its flight line from the axis of the runway by observing the strength of the dots and dashes. When they are equal the flight line is aligned with the runway. The distance of the aircraft from the approach end of the runway is obtained by the navigator entering into Lucero the runway length plus a correction to compensate for the time taken to trigger the Beacon which transmits a pulse back to the aircraft where he adjusts a cursor to give the distance. Part two: The second part of the film illustrates how Eureka can assist in the blind landing of aircraft where the pilot has no visual control unti he is above the boundary of the runway. The Eureka van is seen parked at the end of the runway and the operators preparing to check that the antennae are transmitting a 1o equisignal beam that extends centrally down the runway. The van itself is held within a wooden frame to be  1o of the line of the runway. The final positioning of the beam is done by using a small unipole aerial placed on the centre line of the runway about 50 yds from the van. The RF unit at the base of the aerial is connected by a feeder cable to the monitoring system. The van antennae transmits then transmits the long and short pulses as normal. These pulses are received by the unipole aerial (in lieu of an aircraft) and fed to the monitor cathode ray tube (CRT) display similar to that in an aircraft. The relative positions of the two antennae are adjusted with reference to the received pulses to achieve precise alignment with the runway axis. A Lancaster bomber is seen flying blind under the control of the pilot and navigator working together flying the aircraft to land at a local aerodrome. The navigator monitors the Lucero transceiver/CRT display having input the parameters relevant to the local aerodrome, and advises the pilot they are at 1000 ft and eight miles from the aerodrome but are drifting off the QDM of 270 o magnetic as indicated by an asymmetric display of dots and dashes on the CRT monitor, with a SW wind blowing. This drift off course is corrected by the pilot who maintains the course as directed by the navigator. The navigator continues to report the distance from the runway. The film shows 265o magnetic indicated on the compass as they obtain visual contact with the runway, but the aircraft overshoots the runway because of a 5o drift due to the wind. The aircraft circles as the navigator makes a correction of 5o to the QDM and monitoring distance to touch down, maintaining a symmetric display of dots/dashes, they remain on beam. As the navigator reports they are over the runway boundary, the pilot confirms visual contact and guides the Lancaster to a safe landing.
  • Alternative Title:
  • Colour: B&W
  • Digitised:
  • Object_Number: AMY 468
  • Sound: Sound
  • Access Conditions:
  • Featured Period: 1939-1945
  • Production Date: 1944
  • Production Country: GB
  • Production Details: Air Ministry (Production sponsor) Telecommunications Research Establishment (Production company)
  • Personalities, Units and Organisations:
  • Keywords:
  • Physical Characteristics: Colour format: B&W Sound format: Sound
  • Technical Details: Format: 35mm Number of items/reels/tapes: 2 Footage: 1938ft; Running time: 22 mins
  • HD Media:
  • Link to IWM Collections page:

    AMY 468

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