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Aviation History
1949
1949 - 1935.PDF
FLIGHT, i December 1949 logged over 30 flying hours, including some night flying, in 18 consecutive days. In the flight shed we inspected the second Canberra—a purely experimental Nene-powered variant which made its first flight on November 9th. Production of this version is not foreseen, but it was at one time considered as an insurance policy against delays in Avon development. One also saw the auxiliary tanks which fit snugly at the wing tips and which are jettisonable by explosive bolts. Another Canberra feature, hitherto little known, is the dive-brake installation, in the form tof substantial "fingers" which can be projected vertically from top and bottom wing surfaces, outboard of the nacelles. The third (Avon-powered) prototype was due to fly on the afternoon of our visit, and the fourth we saw, well advanced, in the great Preston factory. Here, too, were others fast taking form. On the lengthy bomb-doors are rollers which slide on curved tracks, allowing the doois to be retracted well into the fuselage to reduce drag. Designed to give positive con- trol at high Mach numbers, the tailplane is of variable-incidence type. The ailerons have spring tabs and a «iand trimmer, the elevators a spring tab and 1 geared tab, and the rud- der a spring tab, which also functions as a trim cr ntrol, allowing " feet off*' handling with asymmetrical thrust. The Avon turbojets are located just forward of the main spar and have removable cowlings, comprising a front circular cowl, secured on a hoop and attached over the leading edge, two main top and bottom removable panels, and a service panel secured by four flush toggle fasteners and quickly removable for inspection of the power plants. All auxiliaries are moun- ted on gear boxes inside the inner wings. By way of a change the men behind the Canberraare seen in front of it : left to right, F. D. Crowe (chief draughtsman), who played a big part inthe structural design; D. L. Ellis (aerodynamics); H. C. Harrison (production design) ; A. E. Ellison(assistant chief designer, development) ; W. E. W. Petter (chief engineer) ; R. P. Beamont (chietest pilot) ; D. B. Smfth (senior administrative officer) ; F. W. Page (assistant chief designer,technical and projects) ; H. S. Howat (R.T.O.). FROM THE OUTSIDE IN AN entirely new technique of airframe assembly has beendeveloped by the Faircy Aviation Co., Ltd., and is already in use in the production of one of the firm's latest types. Thenew system, which reverses the nsual method of first erecting the structure and then applying the skin, gives better controlof the skin contours and also permits interchangeability of components to be achieved at the outset of manufacture—evenin the prototype stage. Briefly, the system (which the company has given the nameof "envelope jigging" because it is based upon the outer aerodynamic form of the aircraft) consists in erecting a systemof accurately shaped formers or templates for the control of the skin contours. These formers are set up on a solid fixture-base and over their contoured surfaces is fixed a metal sheet shaped to the form of the unit that is to be assembled and sodimensioned that the inside or concave face of the sheet cor- responds to the outside form of the aircraft. The formers andthe sheet are related accurately to a common datum. The inside face of the sheet is sprayed with a suitable mediumfor marking-out, and a special table carrying a " scribing- tower " is aligned accurate^ with the datum. The outline ofthe unit to be built is then marked out on the sheet, together with frame or rib stations and the positions of rivet and otherattachment holes. When the marking-out has been checked, the holes are drilledthrough the sheet at the rivet-hole positions, and the sheet then becomes, in effect, a drill-template. Locations for com-ponent-attachment points are also mounted on it. In assembling a unit in a jig of this type, the skin-panelsare first located on the sheet by tooling holes, and ribs or other stabilizing members are then attached inside the skin. Whenthe hole structure has been built up, it is drilled through the sheet template from the outside and the skin countersunk ifnecessary. Riveting is completed in the jig and is done from the inside of the structure, with the rivet heads " held-up "on the outside. This method of construction has the advantage that positivecontrol of the skin contours is given by the sheet template and that the building of the jigs can be begun as soon as theactual shape of the aircraft has been settled, very early in the design stage. By the time that detail design has been com-pleted the jigs can be well in hand or ready—and this work can be done in the knowledge that, unless the external form olthe aircraft is altered, the basic construction of the jig will not be affected. The sheet template also serves as a check on theaccuracy of rib and frame profiles. ORDER COMPLETED: Aotearoa II, last of the 'our ShortSolents for Tasman Empire Airways, Ltd., left Belfast on Nov- ember 26th on the first stage of its delivery flight to NewZealand. Actually the first of the four to be launched, it has been retained for research and test work. It is themakers' claim that, although the Tasman Solents were designed before the 1952 I.C.A.O. safety and performance standardswere published, they comply fully with the requirements.
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