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Aviation History
1947
1947 - 2165.PDF
DECEMBER I8TH, 1947 FLIGHT 693 The New Basic Trainer two light-alloy castings not unlike those sloping stools onwhich assistant^ sit when fitting one's shoes. These mem- bers support and accommodate respectively the rudderpedal assemblies and the control column assemblies: the latter are standard units but the pedal units are Percivals'own and strike us as being a useful development. The swing arm supporting the pedals is pivoted in a yoke mem-ber which is capable of being set, according to the leg- reach requirements of the pilot, within a range of about12m; pedal movement is transmitted to the rudder control cable by an arrangement of chain and sprockets, the greatadvantage being that pedal leverage remains unchanged throughout the whole adjustment range, and static frictionis small. The top surface 01 the spar bridge-box is formed into awell which slopes back to a depth of about 8in at the rear. By this means the occupant of the rear seat is afforded footroom. The under surface of the centre-section box accom- modates two doors about 15m long by ioin wide whichgive access to the interior. Forward of these doors is a View aown rear fuselage showing panel-type semi-monocoque form of construction. single large access door which, hinged on its leading edgeimmediately abaft the firewall, gives access to the primary controls linkage. Dividing the front and rear compartments of the cockpitis a lateral rail of box form made up with channel-section side members tied together with top and bottom plates.This rail ties together the cockpit side panels and, on the centre line, is supported by a sloping box beam which, atits foot, attaches to the centre of the foot well in the centre- section bridge-box. From this point to the top boom ofthe rear-spar spanning-member rearwardly extends a tubular strut to act as a compression / tension member in takingthe reaction of the flap jack mounted behind the spar. The sloping box-member just mentioned provides the centralsupport for the lateral tubes upon which the front seats are pivoted ; the seat backs have swinging link anchoragesto fork brackets carried on top of the lateral tie rail. This arrangement provides rigid mounting whilst permittinga useful range of vertical adjustment for each seat. The rear fuselage is a plain semi-monocoque of Z-sectionstringers for which the channel-section frames are notched, attachment between the two means of stiffening being pro-vided by shear cleats. This part of the aircraft is also built •*s sub-assemblies of side panels, floor and roof panels,which are joined together by riveted lap joints on each frame: a guise of monocoque structure which is seldom The pitot head is mounted close beneath the starboard wing at •'.-"• about mid-aileron span. used, but which has much to offer on the twin scores of rapidity and reduced cost of construction,J|In the tail cone of the fuselage is a built-up box frame in which are carried the two forged brackets to which complementing forgings on the base of the tailplane front spar are laterally bolted. The rear spar of the tailplane is attached to the fuselage at a single central point, the pick-up being a T-bolt and trunnion whereby tailplane incidence may, if neces- sary, be varied; there is, however, little likelihood of this being required unless some radical change in weight distribution is made. Tail Structure The tailplane is built up around the twoplate-web spars with interspar diaphragm- type ribs spaced alternately with lipped-angle contour members. Bracing the three attachment points a pair of diaphragm ribsare splayed in a V about the centre line. Transference of attachment point loadsinto the surrounding spar structure is made with forged fittings to which the pick-upanchorages are through-bolted with the spar boom. The spars themselves are sub-stantially alike, differing only in boom details. .Local reinforcement to booms isapplied by ribbon-extrusions, and the free flanges of booms are machined off pro-gressively outboard. The fuselage terminates with a sternpost in the form of a diaphragm pierced with lightening holes: registering withthis, and through-bolted with it, is the base extension of the fin rear post. The raking front'post of the fin isattached at the foot with a forged end-fitting incorporating Part skinned centre-section spar bridge-box showing spar structure and forkilug wing-cttachment points.
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