Patent GB-581970-A (GB)
Title: Improvements in or relating to bombsights for aircraft
IPC: B64D1/04
Filed: 1941-12-31
Abstract: 581,970. Bombing-sights. BLACKETT, P. M. S., and BRADDICK, H. J. J. Dec. 31, 1941, No. 16816. [Class 92 (ii)] An aircraft bomb-sight comprises means for computing drift angle and ground speed from the course of the aircraft, the direction and speed of the wind and the airspeed, means for computing an ideal bombing angle from the obtained ground speed and the height of the aircraft above the target, means for applying a trail correction to the ideal bombing angle, said trail being computed from the airspeed and the bomb characteristics, and means for applying a further correction to the ideal angle, in response to change in the pitch attitude of the aircraft, to define a sighting angle relative to a datum line in the aircraft. In the computor shown, the data set into the apparatus are air pressure at sea level, estimated target height, wind speed and direction, and bomb terminal velocity. The data supplied automatically to the computer are course of aircraft, air speed and height, and the data automatically computed are the drift angle and the sighting angle. The computor is actuated by electric motors 1, 2, the conveyed rotation being controlled by a pneumatic detector system comprising a pipeline 3 and a pressure-actuated switch 5. The estimated target height and the barometer reading at sea level are set in by rotating a knob 10. The wind direction is set in by knob 100 and dial 103 and the wind speed by knob 104 and dial 107 and these settings pass to the wind mechanism. The terminal velocity is set in by knob 260 and dial 263 and passes to the trail mechanism. The automatic height is obtained by a bellows frame 20, Fig. 2, controlling a curved blade 26 inserted in the pipeline 34 leading to a bellows 32 controlling the directional power from the motor 1 to a shaft 41, Fig. 4, driving a height nut 49. The frame 20 is also rocked by operating the setting- knob 10. The automatic air speed is obtained by a pitot tube controlling- a bellows frame 60 through a curved blade 66 and a pneumatic detector leading to bellows 72 controlling the drive of motor 1 to'shaft 81, Fig. 3, operating through gear 87 a drift carriage 89. Air-speed values are given by a pointer 90. The shaft 81 also drives through the gear 87 a shaft 93 carrying the height nut carriage 51 and also controlled by the wind mechanism to give the ground speed. The wind mechanism shown to the left of Fig. 3 includes a compass-course control 125 and wind speed and direction settings by knobs 104, 100 which act through differential gears on a slotted pinion 110 and a scroll pinion 116 which control a pin 128. This pin actuates the shaft 93 through a tape 133 and acts through a slotted blade 139 on the pneumatic control of a bellows 143 of the automatic drift mechanism, Fig. 4. This mechanism is operated by the motor 2 and gives the drift angle on a shaft 150 connected to the sight, the follow-up being made by a flexible shaft 154 leading to the drift carriage 89. The bombing angle mechanism includes the height carriage 51 moved with the shaft 93 in accordance, with the ground speed, the height nut 49 actuating a lever 50 connected to a pulley 161 over which passes a band passing round a floating pulley 163 and connected to a third, pulley 164. The floating pulley 163 operates a lever 167 controlling the pneumatic supply to a bellows 175 governing the drive of the motor 2 to the sight-angle shaft 186. The follow-up is by a shaft 189 to a cam-shaft 196 acting through a pin 198 on the arm 165 of the pulley 164. Movement of a curved blade 171, in response to the pitch attitude of the aircraft given by a pitch gyro. 173, gives a correction to the sighting angle on the shaft 186. The trail correction is effected by a solid cam 265 and follower 270 which causes lateral displacement of a shaft 195 which, through the pulley 164, corrects the sight angle. The target is viewed through a half-reflecting screen stabilized in roll driven from the drift-shaft 150 in azimuth while the drive from the shaft 186 tilts the screen. A collimating lens may be moved instead of the screen.