Mark XIV bomb sight
The Mark XIV Bomb Sight[a] was a bombsight developed by Royal Air Force (RAF) Bomber Command during the Second World War.
It equipped the majority of the RAF bomber fleet during the second half of the war; small numbers of the Stabilized Automatic Bomb Sight and Low Level Bombsight, Mark III were used in specialist roles.
As the bomb aimer turned a wind direction knob, the main portion of the sight was pushed to the left or right, indicating the required angle to fly to take the aircraft over the target.
Learning of a similar design developed by the US Navy, the Air Ministry began extensive negotiations in an effort to gain a production licence for this Norden bombsight.
Given the problems of obtaining a modern bombsight, he pressed for the creation of a high-speed bomber design that could safely attack at low levels.
Ludlow-Hewitt presented a report on the attack on 22 December 1939, noting that flying straight and level for the CSBS made the bombers easy targets for fighters and anti-aircraft gunners.
[10] What was needed was a new bombsight, one that could be very quickly set up, had useful illumination of the crosshairs for night use, and was stabilized so the bomb aimer could watch the approach as the bomber was manoeuvring.
XI, which mounted a cut-down CSBS on the front of a gyro unit taken from a Sperry Gyroscope artificial horizon, to provide stabilization in the horizontal plane, useful for aiding drift measurements and corrections.
[11][b] The request for a new bombsight was quickly passed on to the Royal Aircraft Establishment, where Patrick Blackett of the Aeronautical Research Committee volunteered to lead the effort.
This reduced the possibility that the numbers would not be changed as the bomber manoeuvred, but required so much manual working that a new crew member was introduced to operate the console, the bomb-aimer's mate.
[14][16] After the initial design was complete, Blackett moved onto other matters with RAF Coastal Command, where he continued development of his theories of operational research.
The fast settling time was invaluable during night bombing missions, as it allowed the bomber to fly a corkscrew (a helical path), climbing and turning, and then level out immediately before the drop.
Even slow turns made it difficult for night fighters to track the bombers within the limited view of their radar systems and continually changing altitude was an effective way to avoid anti-aircraft fire.
This was enough to equip the heavy bombers as they arrived from the production lines and by late 1942 the Handley Page Halifax was being delivered with the sight head already installed.
[17] To fill the demand for other aircraft, especially smaller ones like the de Havilland Mosquito, the Air Ministry began looking at US manufacturers to supply the bombsight.
Sperry arranged for AC Spark Plug to take over manufacture, initially on a sub-contract basis and later for direct sales to the UK.
In August 1943, George Mann of AC Spark Plug visited the UK for a period of about a year, liaising with RAE Farnborough, Boscombe Down and the Ministry of Aircraft Production.
[20] The A model also introduced the ability for the minor differences in instrument readings for indicated and true air speed between aircraft to be corrected simply by replacing a cam.
These T-2 and T-4 (Blue Devil) designs had much higher altitude, airspeed and wind-speed settings, suitable for high-altitude bombing in the jet stream.
These measurements were fed into a mechanical computer that directly output the latitude and longitude of the aircraft, based on automatic dead reckoning.
The same outputs were also sent to the sighting head of the T-4, eliminating the need to manually set the windage and providing those values with much higher accuracy (about ±0.1 mph and ±0.1 degrees).
[26] The CSBS had introduced a mounting system on the left side of the bombsight that allowed it to be easily removed and then replaced without affecting its levelling.
This allowed the bomb aimer to select any convenient object on the ground for drift measurements, including the target itself, long before the aircraft reached it.
When the handle was returned to the resting position and released, the shaft to the computor automatically re-engaged and started tracking the proper range angle again.
Taking this measurement while nearing the target was an important procedure on the CSBS; its manual included several methods of determining the wind speed.
This normally resulted in a small triangular area forming where the three lines came close to meeting, and the centre of this triangle revealed the wind speed and direction.
XIV could calculate the effects of a shallow climb or dive (or glide as it is referred to in bombing), the computor included its own levelling mechanism.
[17] In this case the bomb aimer would dial in the same basic parameters on the various disks, and read out the proper sighting angle at the bottom.
[h] In comparison, units using the much more complex Stabilized Automatic Bomb Sight (SABS) improved the systematic error to 120 yards (110 m) under the same operational conditions and altitude.
[40] A series of reports in the summer of 1944 produced by Bomber Command's operational research division attempted to explain these differences, starting with problems in the bombsight itself.
