|Fighter Command - Detection and Interception|
> Units and Formations
Updated: 17 Aug 04
The first hint of an impending attack may have been detected at the strategic level via timely decryption of ENIGMA traffic, or more generally by the increase in radio traffic picked up by the Y services, as the various Luftwaffe aircrew involved in the upcoming raid, test and tune their wireless sets. Weather reports transmitted by Luftwaffe long range reconnaissance aircraft also provided some early warning of possible avtivity.
As the actual attack began to be prosecuted, Chain Home Radar operators within the Group and Sector areas (at for example RAF Stenigot) sitting in the receiver buildings would start to assessing the 'blips' on their cathode ray tubes. Shortly, the WAAF at the converter would read the glowing numbers from the 'fruit machine' indicating both Grid Position and Height.
A phone call was then made to the Filter Room, usually at Fighter Command at Stanmore, but possibly to the individual Groups' Filter Rooms, to alert the staff to the incoming raid. The Filter Room staff, fusing this information with other reports from the 'Y' services, Naval observers and other sources, then issued the incoming raid with a 'track' designator to minimise the confusion and double-counting of tracks.
As the air picture became clearer, this information was passed simultaneously to Fighter Command Ops and to Groups and Sector Station Operations Rooms, such as that at RAF Digby. Group Operations staff scrambled squadrons to deal with the intruders, if within their area. Orders were also relayed to the Sector controller whose staff kept track of the raid and the interceptors on his own table. Because of the limitations of IFF (Pipsqueak), the Sector controller could only control a maximum of 4 squadrons effectively.
By the time a raid crossed the coast, it would have been reassessed as to its strength and possible destination. Once over land control may well have passed to Ground Control Interception (GCI) sites such as that at RAF Orby.
The interceptors (Hurricanes and/or Spitfires) would scramble within 1 to 3 minutes of the first warning. RAF aircraft needed about 15 minutes to climb to 20,000 ft (slightly less for Spitfires, slightly more for Hurricanes), giving them a couple of minutes margin of safety in the race to intercept.
Ops 'A' gets the squadron scramble orders from Fighter Command. He passes these on 'form A' to the controlling officer.
Ops 'B' calls the squadrons by phone and gives the 'scramble' order, passing on some raid information at the same time.
The Squadrons call the Sector controller on R/T when airborne. They now receive directions until intercept.
At intercept, the individual leaders call 'Tally-ho' and the Sector controllers relinquish control of the intercept to them.
After the battle,
the squadron leaders contact the Sector controller and receive instructions
about where to land.
Between 1935 and 1937, interception techniques were tried out at Biggin Hill with No. 32 Squadron. It was discovered that ... provided plots of attacking aircraft at one minute intervals, correct to within 2 miles were available, it was possible to vector intercepting fighters to within 3 miles of the attackers. These experiments ran parallel to the building of the radar belt around England's South and East coasts under the direction of Air Vice-Marshall Sir Hugh Dowding. The brilliant part wasn't that A.V.M. Dowding figured out how to use the individual technologies but how he forged them into a Command and Control system. Another benefit of this Ground Control Intercept (GCI) system was that the RAF was better equipped to meet any air foe. As long as Fighter Command had access to 'early-warning' information, it could forego the use of standing patrols, thereby reducing the wear and tear on both equipment and personnel.
As it turned out, they built long range stations (CH) about every 20 miles
up and down the coast and 'twinned' them with nearby (some within 1000
yards) short range sets (CHL). Also in reserve, where Mobile Radio Units
(M.R.U.s) which where comparable to CHL sets, with approximately the same
range and accuracy. In modern military terms, the Radar/GCI system was
a 'force-multiplier' allowing a numerically inferior combatant to stay
in the fight against what normally would be overwhelming odds.
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