The Last Flight of Halifax JB837
25/26th May 1943

GEE

Fitted to the first bombers in August 1941 (similar to the German Knickebein system) Gee (short for 'Grid') was a radio navigation system which allowed an aircraft to fix its position within a few hundred yards at distances up to 350 miles away. It was accurate and independent of weather conditions.

Gee stations, one master and two or three slaves, transmitted timed radio pulses which were received within the aircraft on an oscilloscope display, and knowing the difference in reception times of the different pulses, the relative distance from the master and slaves could be plotted on a navigation chart in the aircraft.

Because the pulses were transmitted in all directions, German defenses would know that an attack was imminent, but could not know where the individual bombers were because of the passive nature of the system.

Gee also helped aircraft to find their way back to base, but it was limited because it could be jammed by enemy radio. The RAF estimated that within six months GEE would be useless because of German jamming and pressed ahead with development of OBOE

H2S

H2S was the first airborne ground scanning radar. It was able to identify objects on the ground at night and in all weathers, and because it was not dependent on radio signals transmitted from home territory, could be used outside the range of aids such as Gee or Oboe.

The crude early sets allowed the navigator to identify coastlines, and major ground features such as rivers and built-up areas. Unlike Gee, H2S was an 'active' system, which operated by sending out radar pulses and detecting the reflections, allowing German night fighters to track and home in on the signal source. Initially, in early 1943, it was used solely as a navigational aid, but as it became more sophisticated it was used as a target identifier.

The Germans succeeded in capturing an almost intact H2S on only its second operational mission when a 7 Squadron Stirling R9264 was shot down near Rotterdam by Oblt.Frank and his Bordfunker Fw. Gotter of 2./NJG1 in box Gorilla on the evening of 2nd February 1943[10]. By late 1943, the Germans had developed the Naxos radar detector to home in on the H2S signals. Naxos was first deployed operationally in September 1943, but proved unreliable and inaccurate and was quickly abandoned.

Details of radar equipment including part numbers can be found in the British Radar Manuals library in the Internet Archive [12]

Lorenz 'Blind Approach' Radar

Lorenz standard 'blind approach' radar equipment, including mains and marker beacon receivers (R1124/ R1125) and accessories

The Lorenz system for aiding the blind landing of aircraft was developed between 1932 and 1934 and was widely adopted for both civil and military aircraft. The system employed three ground transmitters, one being the main beacon to indicate the correct landing track and the other being the inner and outer beacon respectively.

The aircraft receiving equipment comprised of: the main beacon receiver, a 6-valve superheterodyne operating between 305-40.4MHZ and the marker beacon receiver, a simple instrument operating on 38MHz. In addition, the equipment included a visual indicator, a control unit, and a power unit.

When approaching an airfield along the beacon, the pilot would hear a succession of dots or dashes according to whether they were to the left or right of the centre line of the beam. When exactly in the centre of the beam, the pilot would hear a continuous note. As the pilot approached the airfield and at a range of about two miles, they would receive a distinctive signal as they passed over the outer marker beacon. Another distinctive signal would be received as they passed over the inner marker beacon at a range of about 3/4 mile from the airfield.[11]

OBOE

A ground controlled blind-bombing device which was remarkably accurate, and proved to be the most accurate form of blind bombing used in World War II. The first Oboe operations took place 20/21 December 1942.

It took its name from a radar pulse which sounded like a musical instrument.

Radar pulses were sent from two ground stations in England called 'Cat' and 'Mouse' while a transponder in the aircraft transmitted the signals back to the ground stations after a short delay. The time taken from the signal being sent and returned could determine the distance of the aircraft. Cat was used to guide the aircraft, and Mouse was used to indicate the bomb release point.

Oboe was a line-of-sight system, so because of the curvature of the earth, Oboe-equipped aircraft could only operate within a relatively short distance of 'Cat' and 'Mouse'. The higher an aircraft could fly, the further its useful range would be. Oboe sets tended therefore to be fitted into Mosquitoes or Lancasters of the Pathfinder Force which had a high altitude ceiling.

Predicted Flak

Flak guns were designed as anti-aircraft weapons. The word is derived from the German FLugAbwehrKanone or 'aircraft defence cannon'.

Their accuracy was improved enormously when associated with a Wurzburg radar which detected the height, speed and direction of the enemy aircraft, so that the flak was directed to where the aircraft was predicted to be when the shell exploded.

Tour of Duty

For most of the war, Bomber Command expected a man selected for aircrew duty to complete a tour of thirty operations, then after a recuperative break, undertake a second tour of a further twenty operations. After that, men could be transferred to training duties or volunteer to continue combat operations.

Remarkably, some men did volunteer to continue. The chance of a bomber crew surviving fifty operational flights depended on the casualty rate, as shown below:

In May 1943, the average Casualty Rate was over 4.7%, an attrition rate that, if it had continued, meant there was only a 10% chance that a bomber crew would survive a Tour of Duty.[4]

The Chances of a Bomber Crew surviving 30 and 50 operational sorties by Casualty Rate

German Words & Abbreviations

German Ranks and their Equivalents [3]