FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1964
1964 - 1643.PDF
900 FLIGHT international, 28 May TURBO-SKYVAN ... around 3,0001b weight. The dimensions of this basic freight hold formed the basis for calculating the optimum wing geometry and powerplant, with the result that an aspect ratio of 11 was chosen with a strut-braced wing. It was estimated that a cantilever wing would have slightly reduced the optimum aspect ratio, but would have been less efficient overall. This original Skyvan, of 9,0001b gross weight, was powered by two Continental GTSIO-520 air- cooled flat-six turbo-charged piston engines each delivering 390 h.p. for take-off through Hartzell three-bladed fully feathering propellers. Originally as an exercise to see where development of the Sky- van's design features and proportions would lead, investigations were made of developments of up to 12,5001b gross weight with a maximum payload of 4,0001b. Some of the arrangements studied even had four of the Continental piston engines, but the final choice lay with two Turbomeca Astazou turboprops of some 550-650 h.p. each. This development became known as the Turbo-Skyvan, and was initially expected to be a series subsequent to the piston-engined Skyvan. In the event, however, the Turbo-Skyvan was found to be of much greater interest to potential operators, the extra cost and more refined maintenance requirements of the turbine engine being outweighed by the appeal of the greater payload and performance. After completing about 35hr flying on the Continental engines following the first flight on January 17, 1963, the prototype Skyvan was re-engined with Astazou Us. After again taking to the air, as the Turbo-Skyvan, last October 2, development flying is now pro- ceeding in earnest and some lOOhr flying have been achieved in over 130 flights. Manufacture of a batch of production aircraft is now under way, and the following description applies to these produc- tion machines. Structure It is a general rule with aircraft that the equipped weight ex- pressed as a percentage of maximum weight becomes less with in- creasing size. The reasons for this are many: most of the equipment and fittings weigh the same regardless of size; the ratio of "wetted" area to gross weight increases as aircraft get smaller; and small structures become less efficient, because the problem of providing sufficient stiffness to resist aerodynamic and handling loads in- evitably leads to low stress levels. Because of the Skyvan's light weight yet generous dimensions, the aircraft's ultimate success depends to an unusually large extent upon that of the structure. Short's boldness in going for the difficult and elusive general- purpose freighter market with a relatively small aircraft was based on an unusual structure composed of large, stiff, light-weight panels made by Reduxing together a thin, flat outer skin to a thin, corru- gated inner skin; the resulting fully stressed panels are then sup- ported by widely spaced frames and ribs. Besides being very light, this form of construction gives an excellent outside surface finish and is naturally fail-safe. Fuselage The Skyvan fuselage is virtually a rectangular box, with rounded corners and simple fairings fore and aft, and a rear door and tail-unit mounting. In the design and method of assembling the fuselage, every advantage has been taken of the simple overall shape. The flat sides, top and bottom are taken to an advanced stage of individual assembly complete with frame portions, door and window coamings, aerials and other equipment, before beinc pinned together in the main assembly jig. The principal features of this jig are to locate the wing, undercarriage, strut and tailplane pick-ups, as well as the box members surrounding the end door. The flat sides, top and bottom corrugated light-gauge skin panels are reinforced by frames approximately 20in apart. The front-end and windscreen frame assembly is a conventional light-alloy monocoque structure which has undergone minor refine- ment since the prototype to give plenty of room for equipment and optional weather radar. The tailplane attachment is straight on to the fuselage frames, whereas in the prototype it was carried above the fuselage; the change was made to save weight. The single-piece main door, which is an integral part of the structure, is hinged at its rear end and can be opened from either inside or outside the cargo hold by a hand crank, which on its first turn releases all the retaining bolts and thereafter raises the door through a simple cable and drum mechanism. The main hold has an emergency-exit hatch in the roof ahead of the wing, and five rectangular windows along each side. Four semicircular doors along each side at floor level provide access for lashing down wide loads. Crew access is through doors with built-in steps on either side of the flight deck. The freight-compartment floor is designed to carry both distributed and concentrated loads, including wheel loads of up to 1,0001b with the use of spreaders. The floor is made of detachable Malinite balsa/ light-alloy/p.v.c. sandwich panels, to which the lashing points are attached directly. The spars for the stub wing carrying the main undercarriage and wing-strut attachment are integral with the two strong frames that pick up the fore and aft wing attachments. Owing to the difficulty of inspecting the corrugated skin panels for signs of corrosion, every part of the light-alloy structure is anodized and the complete fuselage is painted inside and out, the under-floor structure having two coats of epoxy primer. Each main-undercarriage unit is fixed on the end of the port or starboard stub wing. The levered suspension carries single wheel and the simple oleo-pneumatic shock absorber carries only axial load. Designed for operations from rough strips, the single main wheels are fitted with 11.00-12 tyres inflated to 401b/sq in, and hydraulically actuated disc brakes with a differential action for ground manoeuvring. The fixed nose leg is also an oleo-pneumatic unit cantilevered from the front fuselage, with a single wheel having a 7.5-10 tyre at the same pressure. Wing The wing consists of separate port and starboard units, each structurally continuous from root to tip and attached to the fuselage frames by two chord-wise axis pins. Triple-spar fail-safe lift struts attached at approximately the mid-semi-span brace each This "Flight International" operators' reference drawing of the Turbo-Skyvan first appeared in our November 28, 1963, Commercial Aircraft Survey. That the item numbers are not consecutive is due to the fact that the drawing was one of a large number covered by a common key DISTANCE ,5; X—X 76ft 3 Crew door 6 Emergency window or hatch 7 Cargo doors 9 Electronics equipment 22 Jacking points 23 Towing points 28 Intake to air conditioning 34 Batteries 37 Captain 39 First Officer/Navigator 43 Light-alloy fuel tank 44 Gravity fuel fillers 45 Pressure refuelling/defuel- ling 46 Oil fillers 55 VHF 56 VOR 58 ADF 60 General access panel 66 Fire-suppression bottles 69 Booster pump access 74 Landing/taxi lamp 75 Anti-collision beacon 76 Icing inspection lamps 77 Flap gear access 80 Generator 85 Weather/nav. radar 86 Flying control access 87 Flying control power unit access . . . 93 Access to structural JOI« 96 Picketing points 102 Hinged/removable leadingedge 109 Liquid de-icinf . 111 Freight-lashing points "ii 112 Freight-lashing access pa" e>113 Steering angle 115 Loading supports124 Combustion-heater ac«» 127 Window size (inches) 128 Freight-door operates 130 Efe^tHc windscreen wi 151 Auto-feathering pilot 22. 96
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
