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Aviation History
1957
1957 - 1564.PDF
652 ARROW . . . FLIGHT, 25 October 1957 ing the attachment of extrusions to sheet members. One field inwhich Avro broke much completely new ground is the bonding of magnesium alloys, which are extensively used in the Arrowairframe. Rigid control has to be applied at all stages of the bonding processes, owing to die very fine dimensional tolerancesand the arduous thermal conditions under which every bond will operate in service. Turning to the fuselage, the structure is again sub-dividedinto major sub-assemblies. Several feet of the extreme nose- made by Brunswick—is formed from non-structural dielectricmaterial (and in production aircraft will clearly serve as a radome). Continuing to the rear, the next section is obviously to beoccupied by the exceedingly comprehensive search and tactical radar and fire-control system. This bay must be air-conditionedto dissipate the considerable quantity of heat generated by the equipment which it houses, and photographs show that it isenclosed by four substantial access doors which open along longitudinal piano hinges. The radar nose terminates at the frontpressure-bulkhead of die cockpit. The latter is an integral part of the front fuselage, which also incorporates the intakes and thenose undercarriage. Each of the laterally mounted intakes has a fixed geometry andis devoid of a centre-body, although the edges of the intake are exceedingly sharp. These intakes were developed with the helpof the Lewis Flight Propulsion Laboratory of the N.A.C.A. and, although probably reaching peak efficiency at one supersonicMach number, the arrangement undoubtedly has high efficiency over a very wide range of flight conditions. The inner wall of theintake is a flat vertical surface which lies some inches clear from the mould-line of the fuselage proper, the boundary layer beingdiverted through the resulting gap. The sharp edge of the shock- forming wedge which separates the boundary layer from theengine air has a novel interior structure consisting of small hemi- spheres attached to the inner and outer walls and joined to eachother by rods in a manner reminiscent of molecular models. Pilot and navigator sit in tandem Martin-Baker Mk 4 seats ina comfortable cockpit provided with an acutely raked, razor-edged windscreen and separate partially glazed canopies. The latter areof unique design in that each consists of port and starboard halves, which are hinged along their lower edges to the cockpit boundarylongerons. When a canopy is shut, its two halves are locked by multiple bolts along the upper centre-line; the unit can be power-opened in clam-shell fashion for normal entry and exit of the crew. Manufacture of the canopies presented immense problems,and the material is a magnesium alloy not previously used in N. America. Pilot vision, frequently unsatisfactory in aircraft of this nature,was perfected with the aid of a special cockpit rig. A dummy cockpit was mounted at the correct height and angle on a truckwhich became a familiar sight at Malton Airport. Avro's experi- mental test pilots, led by Don Rogers, spent hundreds of hours inconsultation with the design staff responsible for cockpit layout and instrumentation, and the result—as those who have examinedthe mock-up can testify—is outstanding. The U.S.A.F. Director of Flight Safety, the renowned Gen. Joseph Caldara, is on recordas describing the Arrow cockpit unequivocally as the best layout he had seen. One of the complicating factors in the design of the centrefuselage is that much of the underside is broken into by a missile Joining the port and starboard inner wings in their horizontal 'jig. The vertical jigs for constructing each half are visible in the background. Particularly difficult engineering problems had to be solved in providing the Arrow with an undercarriage. The main gear (left) by Dowty carries tandem wheels. As it retracts, eccentric A on the skewed axis pulls up linkage B, shortening the unit by SViin; as the lower leg comes in it is turned by cam C to lie flat in the wing. The nose gear (right), by Jarry, is of equally ingenious design. The arrow points to the retraction jack pivot on the starboard branch of the "Y." When down the unit is locked and braced by the folding strut acting on the projecting arm. The photograph clearly shows the steering system. bay (larger than the bomb-bay of a B-29) which houses a trulyimmense armament pack. No details of the weapons carried may be published,* but the space available is quite remarkable, notthe least impressive dimension being the width of some 10ft. The armament pack occupies the lower part of the centre fuselage andthe missiles must clearly be lowered beneath the aircraft before launching. Inspection shows that the pack itself is arranged tohinge downwards about a transverse axis at its rear end immedi- ately before the missiles are fired. It will also be noted that adetachable pack makes the Arrow inherently versatile. Along each side of the centre fuselage pass the engine ducts,each of roughly oval section and curving across the weapons bay. Major portions of the ducts are allowed to float axially,being restrained at one end only and locked at the other end in sliding joints. The wisdom of this unusual feature becomesapparent when it is appreciated that the Arrow may take off in air at 50 deg below zero Fahrenheit and accelerate until the kineticheating and ram compression make the intake air well over 300 deg F hotter. The remainder of the centre fuselage—the spacebetween the ducts above the armament pack—provides accom- modation for fuel and for air-conditioning. The next section of fuselage is known as the duct bay and, asits name implies, houses continuations of the floating ducts and joins the centre fuselage to the engine bay. Beneath the duct bayare mounted the two speed-brakes, which are very strong and unperforated surfaces hinged at their forward ends and actuatedby Jarry hydraulic jacks. The engine bay itself then follows and, like the duct bay, it comprises a wide, flat-topped assemblyroughly half the depth of die centre fuselage and attached to the underside of the wing by multiple bolts down each side. These portions of die body are completely slab-sided and meetthe wing at a perfect 90-deg joint with no fillet of any kind. The Avro designers were aware of the N.A.C.A. area rule (Flight,September 30, 1955) from an early stage in the design, and the Arrow has naturally been planned to conform to the rule insofaras it is applicable to a machine of high supersonic performance. Between the engines the under-surface of the fuselage rises, toreduce the overall cross-section and improve maintenance acces- sibility. The lower rear part of each powerplant bay can beremoved to provide access to die engine afterburners and hot parts (the word "hot" is only relative in the case of the Arrow) andto allow die complete powerplants to be "pulled" and replaced. * Several Canadian companies are collaborating in the developmentof Sparrow 2, a fully active radar-homing air-to-air weapon original'^ evolved by Douglas from the Sperry-Raytheon Sparrow family.
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