How effective were night fighters in World War II

How did night fighter planes manage to shoot down their enemies in World War II?

There are so many inaccuracies and omissions in @aeroalias' answer that I take it upon myself to add another answer.

Early Years (1939-41)

Up until the beginning of the war, planes were located by listening stations. By feeding each ear an oversized, articulated ear trumpet, both the direction and altitude of an approaching aircraft could be determined by a trained observer. Another method was to use large spherical concrete mirrors with a moving microphone in front of them.

Soldiers operating an acoustic aircraft seeker during World War II, Trelleborg, Sweden, 1940 (picture by Carl Gunnar Rosborn, source)

This could only provide an early warning and approximate location, which was then sent to the fighter plane. These had to rely on their eyes to find the plane and attack, which was relatively easy in the moonlight. The hard part was navigating back to the airfield.

By the start of the war, Britain had almost completed its early Chain Home radar system, while Germany had just deployed eight of the more advanced Freya stations. Both were able to spot planes at greater distances and accuracy than listening stations, and Freya even offered friend-or-foe capabilities early on with properly equipped planes. While the chain home system relied on direction and speed to differentiate between friendly and enemy aircraft, Freya stations (which were later completed with Würzburg stations for altitude finding) could already direct individual fighters to their targets. Tracking was manual and detection errors were common.

The fighters were normal single- or twin-engine aircraft, and initially their only modification was black paint for camouflage. On both sides, otherwise outdated designs were successfully used as night fighters. On the British side, some like the Boulton Paul Defiant were designed from the start to fend off invading bombers day and night.

Aerial reconnaissance photo of the Freya radars in Auderville, France, 1940 (source)

Since the RAF bombing civilian targets began before the end of the "false war", I will focus on the tactics of the Air Force:

  • Dark night hunting ("Dark Night Hunt") The fighters gathered over a radio beacon and were guided individually to their targets by radio commands from a Freya station. At close range, visual identification was used to aim and fire.
  • Light night hunting Here a trio of searchlights were sent to a Würzburg station and a second Würzburg was used to track and direct the hunter while the Freya was used for remote sensing. When the three beams of light converged on their target, the fighter could use that lighting for final approach and aiming. Due to the scarcity and immobility of the headlights, this technology only worked when the bomber train was in the vicinity of the headlight stations. This worked best with little or no cloud cover, but bomber navigation also required cloudless skies, so this technique worked well initially.

Between years (1942-43)

A big improvement in accuracy was the addition of lobe switching to the radar systems. A rotating, slightly offset receiver in the focal point of the Würzburg antenna generated a spherical scan, and the operator could compare the return flows of the radar blips in order to steer the antenna in the direction of the aircraft. If all the returns on the oscilloscope screen were the same, the antenna was pointing straight at the aircraft. Next, a hierarchy of command stations was built to collect information from all radar stations and to direct the fighters centrally. Larger and more powerful systems were used with better accuracy and range. The display of the aircraft locations was also refined: the command stations had plotting tables ( Seeburg table ) with a map showing the planes as points of light so that the Hunter control officer the Hunters could steer better.

Countermeasures were to focus the stream of bombers on a narrow area of ​​the belt of radar stations and searchlights ( Bright bars ) from 1942, so they were just overwhelmed. Remember that it took three radar stations to direct a fighter towards a target. In 1943, the RAF added falling clouds of metal foil strips (windows), the length of which was tuned to the radar wavelength, thereby oversaturating the radar returns. In response, the rigid system of a single line of defense (Kammhuber Line) was divided into a number of stations around possible targets for deep defense, and combat aircraft were given their own radar system to give them more independence. The British Bristol Blenheims and Beaufighters had installed early radar systems on board as early as 1940, the development of which was due to the poor accuracy of the chain home system. Aircraft-mounted infrared searchlights and infrared receivers were also tried, but were found to be missing.

The Seeburg-Lichtenstein method , which was named after the plotting table and the aerial radar, had to be covered by ground-penetrating radars over long distances. It was there bright night hunting without headlights. By adding simple ground equipment for direction and range measurement to control the actively radiating hunters, that was possible Y method switch all radars to tracking bombers, doubling the number of sections covered by one Canopy bed Station (a ground station with additional) could be managed fighter tracking equipment). Now, however, the fighters would also give up their position to the enemy, and specially equipped RAF fighters could use the radio signals of the air force fighters.

Two-way radios in a Me-110 G-4 (Image source)

Late years (1944-45)

A steady stream of improvements resulted in higher frequencies (to reduce antenna resistance) and variable frequencies (to detach yourself from the chaff), but the general tactic of centering fighters in a larger area and getting them close to their targets at large Ground based radars were serviced until the end of the war. By using PPI displays, these radars were able to cut through the chaff and were again effective in controlling hunters, as the detection range of their on-board radars was still limited. Both sides used aircraft radar emissions to hit the enemy with passive detectors.

As the number of Allied aircraft overwhelmed the limited number of dedicated night fighters, regular day fighters were deployed in parallel in an increasingly desperate manner. After General Kammhuber was replaced in his position as head of the night fighters by the much more aggressive Hajo Herrmann, new tactics were developed:

  • Tame pig (tame sow) saw the use of the FW-190 and Me-109 (Herrmann himself flew an aircraft carrier variant of the 109 E at times, which was obsolete for daytime use in 1944 but was fine for night fighting), aided by the lighting of torches from soaring Ju -88s dropped. The addition of passive receivers later went a long way in getting them to their destinations, and without active radiation sources they were immune to countermeasures. In addition, the radars would now perform multiple tasks and guide multiple fighters to their targets in quick succession. That way a single could Canopy bed Installation 15 direct fighters.
  • Wild pig (wild pig) While Tame pig reserved areas for ground-based anti-aircraft fire, expanded Wild pig the concept to mix AA and night fighters. By staying above the height where AA shells detonated intro fragments, they were supposed to avoid being hit by friendly fire, and the FlAK searchlights helped navigate to the stream of bombers and pick up targets (most effective, if they shine against a lower cloud) layer). Again, after an attack, the problem shifted to finding a home, and sophisticated radio navigation aids and floor lighting helped fighters find a home.

Enderland

This is a far broader and more accurate answer than the other is currently. There's a lot more talk of how the back and forth between British / German tech went, which was a big part of that question - especially Window, which shows how effective radar was before it was deployed.