Operating time forin parallel, each one of which has two cylinders with a common ram. The two jacks are mounted side by side, the lower cylinders in gimbal mountings in the base of the nose-fairing structure, the upper cylinders also in gimbal mountings in a fixed bracket on the forward pressure bulkhead of the nose fuselage. Extension of the jacks between these two points has the effect of moving the nose downward about the main hinge-point. The lower cylinders have a stroke equivalent to a droop angle of 5°. That of the upper cylinders is equivalent to a droop angle of 12]2°, giving the maximum droop of 171 2° when the two cylinders are fully extended. In the first stage (5° droop) movement of the nose is effected by downward movement of the lower cylinders of the jacks. The remaining 1212° of droop is given by a further downward movement of the rams from the upper cylinders.Roller carriages, anchored to the fittings at the rear ends of the top and bottom longerons of the nose fairing, track along guide rails, port and starboard, on the front of the nose pressure-fuselage and stabilise the droop movement of the nose. The four possible positions of the droop nose and visor are: Nose and visor up. Nose up, visor down. Nose at intermediate (5°) droop, visor down. Nose at maximum (1712°) droop, visor down. Two hydraulic systems, designated Green and Yellow, are provided for the actuation of the droop nose and visor. Normally, operation is by the Green system with the Yellow available for standby. Operating time for the visor is approximately 6sec. The nose can be fully drooped in 12sec and raised in less than 19sec. normally; the aircraft would be operated with the visor up during the greater part of the flight. For take-off, the nose is drooped 5° and the visor is lowered; both would be raised at the start of supersonic flight. During holding, both nose and visor remain up. During the final stages of approach and landing, the visor is lowered and the nose is fully drooped. Production As already mentioned the nose-fairing structure is basically traditional in type, consisting of skin panels, stringers and frames. It might, however, be described as traditional rendered in modern terms. Skin panels are contour-etched on both sides with, for example, rebates for lap-joints on the external surfaces and, on the inner surfaces, areas between stringer and stiffener lands for weight reduction.This double-sided etching presented an interesting production problem as the etched areas on the opposite faces must be accurately related. The required result was achieved by locating the resist-area marking-out templates for both sides by tooling holes in integral lugs at the panel edges. These tooling holes were also used for panel location in the subsequent assembly stages and the lugs were removed when assembly was completed. Skin panels were stretched to form before being etched and the marking-out templates for the resist areas were also stretched to form on the same forming-tools. Both sides of the panel were etched simultaneously.Many parts of both nose fairing and visor were machined units and for these, and indeed for a large amount of subcontract work done for the industry, Marshalls maintained a machine shop equipped with modern numerically controlled machine tools. The principal NC machines were two Marwin Max-E-Trace triple-head high-speed profiling machines, one with a 14ft and the other with a 28ft table; and a Marwin twin-spindle Max-E-Mill machine.In general, NC procedure followed customary practice. On the two Max-E-Trace machines, Ferranti Mark NC control was used, but the Max-E-Mill had the Bunker-Ramo system. Programming languages used included Profile data (predominantly), Apt and Adapt. In-house programming was preferred because, despite its mathematical-factual basis, the process can become, to a degree, idiosyncratic and therefore more familiar in a particular environment.Tape-proving, as always, presented its problems. A plastic material, Tancast, was largely used for the tape try-out stages. Commercial aluminium was also needed to some extent, although this was an expensive medium, approaching actual component billet cost. Flush-riveting was used for the nose-fairing skin panels, which were hot dimpled to receive solid rivets. What is known as the triple-action dimpling process was used. Triple-action dimpling was development by the American Zephyr Manufacturing Co of conventional Cain dimpling. It was claimed at the time that it produced sharper dimple definition on both the top and bottom of the sheet with better flushness of fitting by the rivet head in the result. As used by Marshalls the dimpling equipment was fitted to a CP-450EAf riveting machine.