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Aviation History
1956
1956 - 0834.PDF
836 PLIGHT "Flight" photograph Clamping up the spar-boom laminations. In the foreground is a rib which has just been removed from its jig; the latter can be seen at the far end of the table. BUILDING A TURBI ... photograph above shows how the laminating operation wascarried out. Clamping was commenced at the centre, and there- after clamps were applied by two people, each one workingoutboard towards the tip. Two one-inch-thick planks were used to distribute the pressure of the clamps along the straightsections of the booms. Indicative of the difficulty experienced before a satisfactoryboom was made is the fact that the boom shown in die photo- graph was rejected, for two reasons. The first was that an un-filled gap was discovered between the laminations on the under- side of the boom, and the second was that in places thelaminations had become "stepped", and planing to remove this would have made the boom too narrow. Subsequent attemptswere successful simply due to the fact that more care was taken to ensure that the clamps were applied "square" to the job. A note might be added here concerning the Aerolite 300glue and its GBP separate-application hardener. In spite of fears that haste would be required in glueing such large com-ponents as the laminated booms, the rush to clamp up the first boom proved quite unnecessary, once an orderly system hadbeen evolved. Strength tests on specimen glued joints have been carried out at regular intervals with completely satisfactoryresults. The green-coloured hardener, though offensive to the eye, particularly at splices in ply, or where it has been allowedto run down a job, has been found to be greatly preferable to its colourless equivalent when assessing the efficacy of a gluedjoint, as it imparts a visible greenish tinge to any surplus glue. The wing ribs all have the same external profile and aretherefore being built in the same jig (Fig. 3). The only varia- tions are in the internal details, which are located by easilyremovable steel pins. Adhesion of ribs to the jig is prevented by rubbing with a block of beeswax the parts of the jig whichare likely to come into contact with glue. This practice in no way causes the parts of the rib to become greasy, which wouldimpair the strength of the glued joints. While the rib frame- work is still in the jig, the lmm ply bands (visible in the photo-graph) are glued in place, pressure being applied by superim- posing flat boards held down with weights. Turning to the tail unit, neither the fin and rudder nor thetailplane and elevator have given rise to snags worthy of men- tion. The former pair is now complete; and all componentshave been built for the horizontal surfaces and are now awaiting assembly. The metal fittings used in the construction of the Turbi areon the whole so simple that only time and very basic tools are required, and most of the fittings have been made. Weldinghas been done professionally in accordance with P.F.A. require- ments. One respect in which the procedure for making metal parts MAIN SPAR LOCATING BLOCK STRIPS GLUED ,TO BASEBOARD REAR SPAR LOCATING BLOCK L.E. LONGERON LOCATING BLOCK STEEL PEGS TO LOCATEDIAGONAL BRACING MEMBERS Fig. 3. Wing-rib jig. Rib components are shown dotted or shaded. has differed from the woodwork side is that new drawings havehad to be produced for most fittings, to cater for differences between British and French standards (such as gauge, bolt andtube sizes). In the case of the undercarriage, this has necessitated what amounts to the complete re-design of this unit. Not onlyare the sizes of the tubes and wheel-hubs different, but it has also been considered wise to improve on certain aspects of theoriginal design which have proved troublesome in service on the French prototype aircraft. These include weakness in the weld-ing near the axle and insufficient damping of the coil-spring shock-absorber strut. In the latter case it is proposed to userubber in place of the spring. The only remaining major modification has been to re-designthe engine bearers to take the Walter Mikron II engine. It is expected that, on approval from P.F.A., drawings of all thesemodifications will be made available by them to other Turbi constructors, who may not yet have reached the stage when theyhave had to grapple with these problems themselves. ......... - T.J. R. L. AVIATION OLYMPICS? AN international aviation sports meeting, to be held in a different• country every four years on the lines of the Olympic Games, is being planned by the Federation Aeronautique Internationale.It would include powered-aircraft flying, gliding, ballooning, para- chuting and model flying. A permanent committee has beenappointed to prepare a programme and lay down rules. It has been suggested that the meeting should include theinternational aerobatic competition, but the Lockheed Hydraulic Brake Co., who give the prizes for the existing event (entries forwhich were announced in Flight last week) have so far stipulated that this contest be held in Britain. THE GERMAN PIAGGIOS THE version of the Piaggio P. 149 ordered for the German airforce as a trainer and communications aircraft is an adaptation of the standard touring and club aircraft. The P.148 was theside-by-side two-seat military trainer, with a fixed-tailwheel undercarriage, which is now the principal Italian Air Force basictrainer for the selection stage. The first prototype flew on February 12, 1951; the type had been ordered in June 1950 anddeliveries started two years later, in June 1952. The P.149, a four/five-seat touring machine, with retractable nosewheel undercarriage, constant-speed airscrew and Lycomingengine, first flew on June 19,1953. During the following two years the first two prototypes were demonstrated at various air shows andrallies; and last summer one was shown at the comparable trials for trainers held for the Luftwaffe at Norvenich. German re-actions were so favourable that Piaggio began straight away to construct a modified version in which the P.149's LycomingGO-435 of 260 h.p. was replaced by the larger GO-480 giving 280 h.p. The number of seats was reduced to two, the controlswere altered to conform to military standards, and special seat harness and provision for parachutes were added. One month after the decision was taken to produce the modifiedversion, the first P.149D was flying; and last December the Germans were able to evaluate it at Hangelar airfield, near Bonn.The result was a firm order for 75 aircraft to be produced by Piaggio, fitted with the Piaggio type 1033 constant-speed, three-blade airscrew, and with the Lycoming engines which they were building under licence as well. Meanwhile the German Focke-Wulf company of Bremen took the licence for construction of the P.149D, and some 500 were ordered. Principal data of the P.149D are: span, 36ft 5in; length, 28ft lin;height, 9ft 6in; wing area, 202.5 sq ft; empty weight, 2,500 1b; maximum aerobatic weight, 3,190 1b; maximum total weight,3,700 lb; maximum cruising speed, 168 m.p.h.; range, 610 miles; full-load ceiling, 17,050ft; full-load take-off over 50ft, 1,280ft.
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