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Farnborough devised a solution which was one of the simplest yet most effective inventions of the war: a mirror was fixed to the end of the gyro and made to reflect an illuminated graticule onto the reflector plate. This graticule moved to the correct position allowing for deflection, and also incorporated a ranging facility. The graticule consisted of a ring of six small diamonds, the diameter of which could be set to correspond with the target span. The type of enemy aircraft was set on a dial, enabling the sight to calculate the range. The reflector screen was a large glass plate 120 mm (4.7 in) x 64 mm (2.5 in). Looking into the screen, the operator saw two illuminated graticules. The one on the left was a fixed ring graticule which could be used if the gyro system failed, its main use being to harmonise the guns with the sights. In the right half of the screen was the gyro-controlled ring of six diamonds. The diameter of the ring was adjusted by foot pedals in the turret version of the sight, and by a twist grip on the pilot's throttle lever on the fighter type. Both graticules could be dimmed for night use, or used singly by switching either on or off. The height and speed setting unit of the Mk I was found to be ideal, and could not be improved. The first Mk II sights made at Farnborough were tested by the Armament Research Unit in July 1943, and it was clear that the problems had been solved.
The new sight had had the undivided attention of some of the most able brains in the country, some of those taking part under Sir Melville Jones being A.A Hale, B. Sykes and G/Capt. Ford. Ferranti played a central role in the design and development of the complex gyro and electrical components. The sight was to be known as the GGS Mk IIC (turret) and Mk IID (pilot). Deliveries from a purpose-built factory near Edinburgh began in late 1943.
The sights seemed to possess almost magical qualities. As an ex-Battle of Britain pilot stated: ' I look back on previous combats where the enemy escaped more or less intact, and realised that I could most certainly and easily have destroyed it if I had been using a good gunsight'. A demonstration was also staged for two pilots of the USAAF. One reported:
I believe this sight would improve gunnery at least 100 per cent. Shooting is at the moment for most pilots purely guesswork. A pilot cannot guess with this sight, due to this I am sure that at least the lower bracket of pilots (75 per cent) will improve their shooting to the level of the best gunnery shots now, and the best ones can do even better. It is easy to handle, and there is no situaiton it cannot handle as well as the GM2, and in most cases (90 per cent) it will do better.
The second pilot reported
Speaking from the point of view of the day fighter, I would say that the Mk IID gyro gunsight is definitely the answer to our problem with deflection shooting. We are proving daily that the average pilot cannot do deflection shooting, even with small angles, accurately with a fixed sight. I think that the sight should be put into produciton immediately and fighter squadrons equipped with them as soon as possible.
Bomber Command were also very keen to receive the Mk IIC version. It was first issued to gunnery schools and operational training units where lectures and air-to-air gunnery practice were quickly arranged. The gunnery schools had been very pleased with the Mk I sight, which had proved invaluable for instructional purposes. A compact 16 mm sight-recording camera had been produced, and gunnery training was much improved owing to the fact that no ammunition needed to be fired, and a record of accuracy could be shown to the trainee. As with the Aldis sight, word soon spread round the operational squadrons and the new sight was eagerly awaited.
At first there was concern over the possibility of the sight falling into enemy hands, and there were restrictions on gyro-equipped aircraft flying over enemy-held territory, but as they became more numerous this rule was relaxed, and the Luftwaffe began to suffer from the attentions of an enemy who could suddenly fire with uncanny accuracy. Not that all fighter pilots accepted the gyro sight with enthusiam at first, for it required a fair degree of dexterity: select graticule brillance, set graticule presentation, set span level, then once the target is presented align the ring of diamonds to the enemy span. No such preparation was needed on the Mk II, but as pilots gained experience the early scepticism vanished, and results bore witness to the gyro's effectiveness. The US Navy and Army Air Force formally accepted the sight, and production commenced in America where it was designated the Mk 18 (Navy) and K-14 (USAAF). In Canada, Semco Instruments produced a naval sight more robust than aircraft versions and with two dimming screens to counter glare off the sea. Otherwise the 'works' were identical to the Ferranti model.
Perhaps the reader can imagine himself seated in the Frazer-Nash FN.20 tail turret of a Lancaster, flying in daylight over Germany in early 1945, when an enemy fighter is seen to dive to the attack.
The heart misses a beat, but then you realise that only you can save the aircraft and crew, you are in effect in full control. First you inform the captain and crew of imminent attack, and tell the pilot which way to break away to give the enemy maximum deflection. You will have already set the height and speed on the dials of the control box mounted horizontally at hand level to your right. You identify the fighter and set its wingspan on the span handle. You now operate the left pedal which opens the ring of diamonds to the maximum range setting. As your attacker closes in, you keep him inside the ring until he fills the ring; he is now framed and within range - open fire with a four-second burst. As long as you can keep him centre in the ring your bullets will be striking home. If he keeps coming in, he will appear to get larger; depress the right pedal to control the ring and keep his wingtips touching the diamonds. Track the target accurately and smoothly at the same time as closing the range with the pedals. When the target reaches 183 m (200 yds) the graticule will not get smaller, but the sight will still be accurate. Keep the right foot pressed and aim at the aprt of the fighter where hits will do the most damage.
A fighter pilot using the Mk IID would not use pedals to control the diamonds but a twist grip on his throttle. The operator could select various combinations of illumination. With Gyro Night, only the gyro graticule was visible, and the range was set to 165 m (180 yds) irrespective of pedals or twist grip. This was the usual maximum range at night.
Several types of German aircraft were marked on the dial, and aircraft identification became even more important to pilots and gunners. Gunners were taught to recognise the frontal silhouettes of German and Allied aircraft instantly. Anyone who failed the aircraft recognition test badly often failed the course.
Details of Mk II GGS Gyro Sight Production
GGS specification received from Air Ministry to Ferranti Ltd, Edinburgh, February 1943.
Site for new factory purchased December 1942.
Building commenced February 1943.
Factory opened June 1943
First production sight 30 November 1943
Quantity production commenced February 1944
Output by March 1945: 1,000
From a labour force of 100 in July 1943, Ferranti employed 950 at peak production in October 1944.
Number produced.
1944
February: 8
March: 110
April: 200
May: 250
June: 370
July: 380
August: 420
September: 540
October: 700
November: 720
December: 600
1945
February: 400
March: 1,000
April: 1,100
Other companies were also involved in production: Barr & Stroud supplied lenses and produced a small quantity of complete sights. Salford Electrical Company produced gyro sights to Ferranti drawings, and other concerns carried out sub-contract work.
The above text was taken from "British Aircrat Armament Vol.2: Guns and Gunsights", by R Wallace Clarke.
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