Decca Navigator http://www.jproc.ca/hyperbolic/decca.html WHAT IS DECCA NAVIGATOR? The Decca Navigator System, herein abbreviated as DNS for convenience, is a hyperbolic radio navigation system which was established in the United Kingdom after World War 2 and later used in many areas around the world. It operated by measuring the phase differences between continuous signals from a master and slave stations. These differences were then related to a hyperbolic lines printed on a chart. By plotting the readings from two pairs of hyperbolas at any particular instant, users could plot their position instantly. The system used groups of at least three shore based transmitter stations called chains operating in the 70-130 kHz radio band. Each chain comprised of one Master and two or three Slave stations, usually located 80 to 110 km from the Master station. The accuracy of DNS ranged from 50 meters during daytime to 200 meters at night. It could decrease up to 800 meters as the distance from the baseline increased. Accuracy was also affected by seasonal effects which generally reduced the accuracy by a factor of 6 to 8. The maxium daytime range for DNS was 300 to 400 miles with a reproducibility of 200 meters. At night, accuracy was guranteed out to 240 nm by the British Admiralty. For a comprehensive look at Decca, select the following: History Corporate Highlights System Overview Transmitters and Antenna Description of Chains Decca Survey Chains Receivers and Indicators - Airborne Types Receivers and Indicators - Marine Types Test Equipment Manufacturing Facilities Sales Demonstration Aids Decca Hi-Fix and Hyperfix (off site link) Key People Decca Memorabilia Decca Navigator News Listing User Comments and RCN Useage Submissions From Former Employees Product Brochures (off site link) Looking For Former Employees Museums and Collections Wish List for HMCS HAIDA Bibliography 1 of 2 13/07/2011 10:53 Decca Navigator http://www.jproc.ca/hyperbolic/decca.html This was the corporate logo of The Decca Navigator Company as imprinted on a system manual. (Graphic courtesy The Decca Navigator Company) Back to Hyperbolic Index Page 2 of 2 13/07/2011 10:53 Decca Navigator - Airborne Receivers and Indicators http://www.jproc.ca/hyperbolic/decca_rx_ind_airborne.html (Survey and special-purpose receivers, e.g. Type 990 (RAF Mk 1 Air) not included in this document). Mark 6, 7, 8, 9, and 10 were all airborne-only receivers. Mk 4 was available in both airborne and marine versions Mark IV Receiver Mk IV - Front View (Photo from the collection of Walter Blanchard) Mk IV - Rear View (Photo from the collection of Walter Blanchard) Type: Mark IV (MkIVA airborne version shown above) Input Power Requirements: Airborne - 80 VAC at 1000 cps at 80 watts. 12 VDC at 90 watts. 24 VDC at 90 watts. Marine - 110 VDC at 90 watts 1 of 15 04/11/2011 09:41 Decca Navigator - Airborne Receivers and Indicators http://www.jproc.ca/hyperbolic/decca_rx_ind_airborne.html Display: 1 set of decometers Number of Channels: 4 (Master, Red, Green and Purple) Dimensions: 15.5 x 15 x 7.5 inches Weight: 25 Quantity Produced: ?? Purpose: Airborne navigation Comments: Receiver in production as of 1946. Sub-designated QM 's 6,7,8,11,13 depending on chain and frequencies. The very first Mk 4 receiver was fitted to M.V. ROGATE (Stephenson Clarke Shipping) on Feb 26, 1947 Variant: MkIVA was used for airborne navigation. Mk 6 RECEIVER 1949: Decca Mk 6 Aircraft Receiver. (Photo from the collection of Walter Blanchard) This diagram shows the external controls of the MK 6 receiver. (Image from the collection of Walter Blanchard) SPECS 2 of 15 04/11/2011 09:41 Decca Navigator - Airborne Receivers and Indicators http://www.jproc.ca/hyperbolic/decca_rx_ind_airborne.html Receiver Dimensions: 21" W x 8.5" H x 11" D. Receiver weight: 24.5 lbs. Capability: Can receive up to 5 chains. Remotely controlled from cockpit. Power Unit Dimensions: 6"W x 8.5"H x 11"D Power Unit weight: 19 lbs. Power Input 24 VDC@ 12.5 amps Comment: Airborne receiver electrically similar to Mk. 5 Pilot's remote control for the Mark 6 receiver. (Decca Navigator Company image) 1949: Mark 6 decometer panel. (Courtesy "The Aeroplane", June 1949) FLIGHT PLOTTER 3 of 15 04/11/2011 09:41 Decca Navigator - Airborne Receivers and Indicators http://www.jproc.ca/hyperbolic/decca_rx_ind_airborne.html To simplify the problem of navigating in all types of aircraft, Decca came up with a solution in the form of a presentation suitable for pilot navigation. Simple route graphs prepared by the Decca Navigator Company for all European air routes were inserted in the Flight Plotter and the pilot only needed to turn the knobs of the Flight Plotter to bring the perspex cursor to correspond to the Decometer readings at any point on his flight, to obtain, without further effort, not only a position fix, but also range and bearing from destination. The pilot was entirely free to make any deviation from route when circumstances necessitated and was able to use this simple and efficient method of navigation throughout his flight. 1949: Decca Flight Plotter. Click to enlarge. It bears no model or part identification because it was the very first one that Decca produced. The complete Flight Plotter illustrated here contains the Route Graph for the Metropolitan Control Zone, which enabled the pilot to continuously and accurately plot his approaches along the corridors to the principal Metropolitan airfields in Europe. Weight of the Flight Plotter is 4.5 pounds and its dimensions are 12"W x 14" H x 2"D. (Decca Navigator Company image) This device, in conjunction with the Decca Navigator Mark VI receiver and the existing Decca chains of the day provided a realistic and practical aid to navigation in Europe. SAMPLE ROUTE GRAPHS FOR THE FLIGHT PLOTTER Click to enlarge. This is the Route Graph for the area north of London enabled range and bearing from Luton Control Point to be obtained at any time during the flight. This. Route Graph was used for general flying in this area and for all routes running into the London Control Zone from the North East area. (Graphic courtesy Decca Navigator Company) Click to enlarge. The Route Graph shown here is for a typical European air route such as Brussels to London. (Graphic courtesy Decca Navigator Company) FLIGHT LOG The Decca Flight Log was a logical extension of the Flight Plotter and was made possible by the use of the new map projection technique used in the Flight Potter. The map of the route to be flown was carried on a cylinder, measuring 16 inches in length and 7.5 inches in diameter. As the cylinder was rotated about its axis by the drive unit, it was traversed by a Perspex scale. A marker carried by this scale made, on the map, a continuous recording of the track of the aircraft over the ground. As was the case with the Plotter, the map could be varied to suit particular requirements. Complete flights of up to 300 miles could be covered on one map, with separate diagrams to cover the approach pattern, traffic holding procedure, etc. 4 of 15 04/11/2011 09:41 Decca Navigator - Airborne Receivers and Indicators http://www.jproc.ca/hyperbolic/decca_rx_ind_airborne.html Decca co-ordinates would not normally be marked in on the map but would be printed in the appropriate colours on the reverse side. If it was desired to check the Log for accuracy, the inside of the drum could be illuminated, to make the co-ordinates visible. Readings could then be taken from the receiver and plotted in the usual way on the map. A time plotter was also provided for optional use. When switched on, it caused the pencil marker to deviate at given intervals and thus provided a record not only of the track flown by the aircraft, but of the time taken over various sections throughout the flight. Apart from the obvious value of the Log for navigational use, it had an important application as a flight recorder. The installation of a Log in the rear of an aircraft used for navigational training, for instance, would enable a complete picture of the pupil's flight to be obtained and a post morteum could be held if necessary. Similarly, aircraft operators would find the installation of a Log useful as a means of checking the movements of their aircraft. In 1949, the Flight Log only existed in prototype form and flight trials had not yet commenced. It had, however, been extensively tested in road trials, and some impressive results were obtained. In one test, a vehicle equipped with the Flight Log had a run down the Kingston By-pass (in the UK). The engineers watched the Log draw a line accurately down the centre of the road marked on the map. They did however, notice that telegraph and trolley bus wires sometimes caused serious deviations. At short ranges, this would make road use of the instrument impracticable. It was anticipated that Flight Log would be available by 1950. Essential components of the Flight Log were a torque amplifier, a drive unit, a display unit, and the Mark 6 Decca Navigator Receiver which fed the drive unit. In 1949, only prototypes of the Flight Log were available. (Decca Navigator Company photo) Mk 7 RECEIVER Airborne receiver using locked oscillator; phase comparison directly at slave frequencies. Mk 8 RECEIVER Airborne receiver same as Mk. 6 but fitted in standard SBAC racking. This receiver was used by the RAF. In 1955, eight Valiants and ten Shackletons were fitted with Mk 8 receivers and flight logs for “Operation Grapple”, the nuclear bomb tests at 5 of 15 04/11/2011 09:41 Decca Navigator - Airborne Receivers and Indicators http://www.jproc.ca/hyperbolic/decca_rx_ind_airborne.html Christmas Island.