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LOCUS Laser Radar

Technical Information

Catalogue No: C0479
Category: Surveillance/Acoustics
Object Type: Sensor/Transducer
Object Name: LOCUS Laser Radar
Part No: Not Marked
Serial No: Not Marked
Manufacturer: GEC Avionics
Division: Airborne Display [ADD]
Platform(s): A-6 Intruder
Year of Manufacture: circa 1988
Dimensions: Width (mm): 360
Height (mm): 900
Depth (mm): 300
Weight (g): 0
Location: Main Store



The Pod was unfortunately broken into three sections before the RAA acquired it. However at 14' in length and rather heavy we could not have got it into the Museum in one piece!

In 1986 using Navy foreign weapons evaluation money, topped up by GEC Avionics private-venture funding, an A-6E was equipped with a full suite of night-attack avionics. The overall system allowed the A-6 to operate in all weather conditions by day and by night and the system was called Night Attack Navigation System (NANS). This concept had been pursued in the UK with the Royal Aerospace Establishment at Farnborough and in the US with this programme called ‘Real Night’ at the Naval Air Test Center Patuxent River (near Washington D.C.).

The A-6's radar and inertial measurement unit were retained, otherwise the aircraft was completely redesigned around a 1553B digital databus.

A "Phase O" series of flight tests was conducted in mid-1986. For this the A-6 was equipped with a FLIR navigation sensor (supplied by GEC Sensors) with a thermal target-cueing device, contained in a systems pod carried under the port wing. Output from the FLIR was displayed on a monochrome head-down display. The A-6 was also equipped with a digital map generator. ADD supplied Colour Head Down Displays based on the ruggedised Matsushita shadow mask CRT. To fly at night the crew used the FLIR, the map, and GEC Avionics' Cat's Eyes indirect view night vision goggles.


For the Phase 1 flight trials which began in December 1986, the aircraft was equipped additionally with two raster-scan Head Up Displays capable of displaying the FLIR image. The HUDs were derived from displays under development for the C-17 transport. Cockpit lighting was modified to be compatible with the image intensifying NVG’s. A scan converter was added to allow the radar picture to be presented on any Head Down Display.

The Phase 2 flight trials added terrain-referenced navigation and passive terrain following based on an onboard digital terrain elevation database. This was combined with cultural information digitised from standard paper charts to produce the digital maps displayed in the cockpit. GEC's Spartan terrain reference - navigation terrain following (TRN/TF) system has been under development for 11 years and flew in a Tornado in late 1987. In the A-6, Spartan was used to generate fly-up/fly-down commands displayed on the HUD for manual terrain following.

Other Phase 2 additions included tactile bezels on the Head Down Displays and, latterly, the Locus obstacle warning pod to detect unmapped obstacles in passive terrain-following flight.

In September 1988 Grumman Aircraft Corporation awarded the Company a contract for the full scale development of a wide field of view day and night HUD for the A-6 aircraft.

There were about 200 A-6 aircraft in service with the US Navy at that time and retrofit orders were expected. Although five development aircraft were built, the Navy ultimately chose not to authorize the A-6F, preferring to concentrate on the A-12 Avenger II. This left the service in a quandary when the A-12 was cancelled in 1991.

Grumman proposed a cheaper alternative in the A-6G, which had most of the A-6F's advanced electronics, but retained the existing engines. This, too, was cancelled and the Navy concentrated on the F-14 Tomcat.

In 1988 GEC Avionics supplied a Laser Optical Cable Unmasking System (LOCUS) for the US A-6 Real Night night attack trials. Real Night was a follow-on from the earlier Cheap Night programme, which resulted in GEC Avionics being chosen to supply the forward-looking infrared (FLIR) night vision goggles (NVGs) for US Marines Corps night-attack AV-8Bs. The Real Night A-6 had Head Up Displays, Colour Head Down Displays, Digital Map , Spartan Terrain Reference Navigation and Terrain following, Cat’s Eyes Night Vision Goggles, FLIR Pod and LOCUS Pod all supplied by GEC Avionics.

LOCUS was a powerful laser radar contained in a 14ft pod under the wing of the aircraft (similar in size to the FLIR Pod) for the detection of obstacles such as High Voltage cables. The pod houses in its nose a C02 laser which scans an 8° box: 2° up, 6° down, and 4° left and right, executing a near-vertical sinusoidal scan pattern at 50kHz, to build up a picture in 1-1.5 sec.

This picture is overlaid on the HUD FLIR image, and obstacles, once detected and stored, continue to be displayed even after they have moved out of the 8° box covered by the scanning laser.

Locus is designed to detect a 1 cm-diameter cable at l-5km range in pouring rain, giving sufficient time for the pilot to avoid an obstacle that is neither logged in the digital terrain database nor visible on FLIR.

The pod was ground-tested before shipment to the US Navy and worked successfully in the Real Night trial when it detected cables out to 2km.

Mike Busbridge and Dave Puleston of GEC Avionics Ltd presented a paper on the trial ‘A laser obstacle avoidance and display system’ at the Aerospace and Electronics Conference, 1989.

When test flying with the LOCUS Pod one pilot would fly with just the HUD and the second pilot acted as a safety pilot. I must have been quite exciting as they flew close to the ground towards power lines to see if the LOCUS Pod picked them up!. The laser radar would scan ahead to detect power lines which presented a danger to low-flying aircraft.The complex processing of the radar returns and creation of an image on the HUD was designed by Simon Trythall and required the latest INMOS transputers.The image had to overlay the real world perfectly regardless of the aircraft movement. The concept was brilliant and successful but sadly the system was never developed further.


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