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Aviation History
1956
1956 - 0638.PDF
638 FLIGHT, 25 May 1956 (Left). The compactly designed control unit. (Right). Recovering the CT-10 from the sea; the nose section, containing instrumentation, is watertight. THE CT-10 GUIDED TARGET . . . link for the jet-pipe has sufficient freedom of movement to takeup expansion. The fuel used is ordinary petrol, preferably of less than 90octane rating. The fuel system consists of the tank (forming the central portion of the fuselage), inside which is mounted thecompressed-air cylinder that pressurizes the system through a reducing valve. The fuel is metered by a form of barostaticvalve, mounted on the rear face of the tank. Stability and Control. The CT-10 is stabilized laterally by anautopilot, comprising a vertical free gyro and a rate gyro which actuates the wing spoilers through an electrical relay. The radiocontrols operate both the elevator and the spoilers through the autopilot, using a 109.08 Mc/s V.H.F. receiver. Power for theradio and autopilot is derived from a 40 amp (20 min) lead-acid battery. The aircraft has been designed to be inherently stable in yaw,dynamically stable in pitch and unstable in roll. The lateral instability is checked by the vibrating spoilers. The rate and rollgyros control the spoiler-actuating relay so that the electro- magnetic spoilers themselves are kept oscillating to correct thenatural tendency to roll. With the CT-10 in flight, it is just possible to see from behind that it is rocking rapidly, but with asmall amplitude. When the spoiler circuit receives a bank signal (as the first phase of a turn) an electric motor rotates the mountingframe of the gyros to the required angle. The spoiler circuit now receives its current through a trembler and limit switches, sothat the necessary angle of bank is automatically maintained. The dynamic stability in pitch is such that, with its fixed powersetting, the CT-10 has a slightly undulating flight-path. As the nose drops, the speed rises and lift builds up, so that the aircraftclimbs until the speed drops, the lift falls off and the nose dips again to repeat the cycle. The limits within which this takesplace are +20 kt with a vertical amplitude of 200 to 300ft. If the engine stops, the CT-10 settles into a similar type of phugoidglide. When the radio command "dive" or "climb" is given, theelevator is moved by an electric actuator. The elevator acts by upsetting the undulating flight-path and the initial effect is quite The electro-mechanical P.P.I., whereby the target's track is traced on o chart mounted on a frosted-glass screen. Altitude is shown by the ammeter at top left. The reason for the twin display is undisclosed. different according to whether the movement occurs during theupward or downward part of the phugoid. For example, if "dive" is given as the aircraft is climbing, it will continue to climb untilthe speed falls sufficiently for the nose to drop, when the resulting dip will be greater than normal and the aircraft will go into adownward phugoid. This motion will gradually be damped by the dynamic stability until the amplitude is similar to that forlevel flight. If, on the other hand, the elevator movement is initiated while the nose is pointing down, the new path will startas a steepened dive until the lift builds up sufficiently to raise the nose against the elevator. From this it is clear that the elevatoraction is in the nature of a trim change rather than the direct pitch control of a piloted aeroplane. Being inherently stable directionally, the CT-10 will continueindefinitely on its course. The command "turn" results in rolling (up to 30 deg bank) followed by the application of upelevator; the strong directional stability then serves to keep the nose level. At the end of a flight, when fuel runs out, or if at any timethe aircraft ceases to receive radio signals, the landing sequence takes place. Fuel, if any is left, is cut off from the engine by anelectrical valve within 8 sec; at 15 sec an explosive bolt in the nose is fired and the recovery parachute is released from itsnose compartment; after this there is a further 7 sec delay, to allow the engine to cool, before an explosive bolt blows out adump valve in the bottom of the tank. The parachute cable is reeved along the bottom of the fuselage to a shackle at the tail,so that the aircraft descends nose-first. The fuselage is well supplied with shackles and lifting eyeboltsockets to assist recovery from the sea. Launching and Flight Control. The CT-10 is launched froma transportable ramp of triangular girder construction, 39.4ft long and with a positive angle of 5 deg. Two U-shaped rails27.6in apart guide the launching trolley, to which two 8,000 1b- thrust powder rockets are attached. Trolley and rocket-casesdrop away and are saved from damage by a parachute. The combined thrust of the engine and rockets gives a lOgacceleration and an airspeed of approximately 115 m.p.h. when the aircraft leaves the ramp and 230 m.p.h. at the end of the com-bustion of the rockets. The launch is made with a positive elevator angle of 3 deg, so that the aircraft starts off with aninitial "zoom" to perhaps 1,000ft in a distance of about 1,500 yd. By the time this height is reached the speed has fallen off to thepoint where there is insufficient lift to support the aircraft, and it goes into a fairly steep dive, from which it recovers and settlesinto a phugoid climb. This will continue, unless "commanded" otherwise, until the aircraft reaches its ceiling. If the CT-10 is a simple aircraft, its tracking and control systemis uniquely so. The tracking system consists of a standard I.F.F. transmitter/receiver for height and range and sighting binocularsfor azimuth. The position readings from these instruments are electrically transmitted to an electro-mechanical P.P.I, display.The I.F.F. signals are re-transmitted by the transponder set in the aircraft. Two signals are returned: one direct, which gives arange "blip" on the time-base of the cathode ray tube of the I.F.F. receiver; and the other through a barometric capsule delayfor altitude. The altitude signal is received through a decoder which converts it to a cathode-ray tube "blip" on the height-baseand also to a milliameter with a large dial calibrated for altitude and mounted at the top of the main display. The I.F.F. range data and the bearing information from thesighting binoculars are converted by the P.P.I, into a light (or stylo) trace on its screen by a radius arm and traverse motor. Thistracking device is behind the circular frosted-glass screen, on the front of which either a flight plan or local map is mounted beforethe exercise. The tracking binoculars are electrically coupled to an azimuthmotor which orientates the I.F.F. aerial to follow the target. Should the CT-10 disappear into cloud the observer switches offhis control of the aerial, which is then used to make a D/F.
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