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Aviation History
1955
1955 - 1596.PDF
FLIGHT, 4 November 1955 713 LOCKHEED ELECTRA ... even the most common, Electra engine. One Lockheed engineersaid, bluntly, "we want the engine from Derby; and if we can't have the Rolls engine in time, the Eland has a good chance."Anyway, for the time being the Electra is wrapped around four Allison 501s. Each is installed as a complete power package and,except for certain handed items and accessories, all four are inter- changeable. These Allison engines have the reduction gearboxmounted remotely from the power section (see detail drawing on p. 715), thus allowing the air intake free entry to the compressor.In the C-130 the intake is under the spinner, but various factors have resulted in the Electra engine being "the other way up," i.e.the axis of the airscrew lies below the axis of the engine, and the main air intake duct passes down from the top of the cowlingbehind the spinner. The cowling and nacelle structure contains a high proportionof stainless steel and titanium alloy, and firewalls divide the interior into three zones, each of which is provided with "thelatest fire surveillance" and high-rate extinguishing systems. In the large cut-away drawing the starboard outer powerplant isshown with the various access doors open. All doors and panels are secured by quick-release latches, and may be completelyremoved at the hinges if necessary. Loads from the reduction gear and engine are taken out through a tubular structure whichis finally anchored to the front spar. By removing the turbine- access door, disconnecting the firewall connections and thenreleasing the four engine-mounting bolts, the complete engine- change unit, with airscrew, can be inched forward slightly andthen lifted clear of the airframe. Airframe accessories are nearly all mounted on the airscrewreduction gearbox, projecting to the rear. The oil tank is carried above the compressor, and the oil cooler is mounted beneath theengine in an individual air tunnel, with a flush, thermostatically controlled exit vent. The jet pipe is carried back across thewing, from which it is sealed by a stainless-steel firewall over the unbroken wing upper skin. Considerable attention has been paid to reducing the drag ofthis installation, both externally and internally. Lockheed claim that, by "Coke-bottling" the tailpipe fairings over the area ofmaximum wing thickness, the drag of this region has been reduced, particularly at high speeds. Interference drag can beconsiderable at the speeds for which modern transports are designed. For the Electra, design limit speeds are: diving, 420 kti.a.s. to 7,000ft and M = 0.725 above; and level flight, 335 kt i.a.s. to 11,000ft and M = 0.625 above. Airscrews are of 13ft 6in diameter—slightly on the small side,one would think—and have four wide-chord blades. Aeropro- ducts are expected to supply units for the first production Electras,although Curtiss (and possibly Hamilton Standard) are in the market with suitable units. Airscrew de-icing is electric, andfeathering and reversing are to be provided, with auto-feathering for take-off being (at present) a specified requirement. Engine starting is pneumatic. Each engine carries a Bendix-Eclipse air-turbine starter working off a 3,000 Ib/sq in supply. When one engine has fired-up properly, it can serve as the sourceof air for the other three. Undercarriage. Each main leg carries two wheels, withdimpled tyres and multi-disc brakes fitted with anti-skid units. Retraction is in a forward direction under the action of a singlehydraulic jack, the up-locks being mechanical. The gear can be lowered without hydraulic power, and can lock down undeigravity and air loads. Conversely, the units cannot be retractec on the ground unless hydraulic power is present, since the staticposition of the leg is "over-centre." Each main leg is a simple machined forging, housing an oleo-pneumatic shock strut. The wing attachments are also large machined forgings, and Lockheed have stressed the fact thatexcessive loads from the main legs cannot normally rupture the wing tankage, the latter nowhere coming into the close proximityof the leg attachments. It may be observed that the retracted main units require quite a bulge in the underside of the innernacelles, although the wing structure is not broken into. The nose unit also carries two wheels, and is likewise a forgingwith an oleo-pneumatic shock absorber. The unit is mounted on a pair of forged attachments under the floor of the flight deck(which at this point also serves as the boundary of the pressure hull), and is hydraulically steerable. The unit retracts forwards, The Electra cockpit is designed to S.A.E. recommendations and provides tor a flight crew of two or three, with a fourth seat (visible in the foreground) for a supernumerary. On the pedestal are radio controls and, to port, the flight-idle gate release, and flap controls to the rear of the big trim wheels. The fuel panel is on the rear face of this pedestal. Power levers are on each side, sandwiching the four condi- tion levers and the large undercarriage lever. On each side of the facia is a P.P.I, display for storm-warning radar and the nosewheel- steering wheel is just behind the captain's radar display to port. hydraulicalry, into an unpressurized bay. All undercarriage baysare closed by twin doors. Power Services. Most of the accessory power of the Electrais electrical, and the entire load is generated as three-phase A.C at 208/120 V, 400 c.p.s. by four alternators, one on each power-plant. It is the manufacturer's intention that output should be paralleled. Low-voltage D.C. supplies are provided by advancedrectifiers, most of this load being required by ancillary heating and lighting services.In the unpressurized bay under the wing centre-section (under the passenger-cabin floor) is an electrical service centre, reachedfrom outside via large downward-hingeing doors. In this area are fitted hundreds of circuit-breakers, fuses, junction boxes and everyother electrical component which could reasonably be put there. The interior is electrically lit and is painted white to improve thelevel of illumination. Hydraulic power is provided by engine-driven pumps supplyinga 3,000 lb/sq in system. Full pressure is used tor undercarriage retraction, air-stair actuation and other main power functions,and reduced pressure is employed for wheel braking. Compressed air at 3,000 lb/sq in is delivered by multi-stage compiessors, andserves for engine starting. Fuel. All fuel is housed in integral tanks formed by the mainwing box bounded by the tront and main spars and the upper and lower, integrally stiffened skins. There are two such tanks ineach wing, each tank being inboard of the engine which it serves in normal flight (although, of course, any engine could draw fuelfrom any tank). Total capacity in the normal four-tank system is 3,480 Imp.gal, but this can be supplemented, in a long-range aircraft, by some 500 gal outboard of each outer engine. Provision is madefor jettisoning in flight. The entire system is replenished via a single pressure-fuelling socket under the fuselage, close to thefillet beneath the starboard wing. This socket can be reached without trestles. Cockpit Very extensive study has gone into the design ofthe Electra flight deck, which is laid out for a normal operating crew of three, although two-man crew operation is possible. Ineach case an additional jump-seat is provided. Lockheed have also allowed plenty of room for crew kit stowage. General form of the flight deck is fairly conventional, with aclassic type of nose entry, and windscreen panels of normal shape and angle. The transparent areas are electrically heated andcomply with bird-proofing requirements for high airspeeds. Additional windows are provided in the roof. Comfortable seats,of unusually large dimensions, are provided for the two pilots, each of whom has a pillar-type control column and a full set offlight instruments. The general arrangements of the controls, instruments and lighting is in close conformity with the require-ments of S.A.E. Committee S-7. The accompanying drawing shows the manner in which flightinstruments face each pilot and are separated by engine instru- ments in neat rows with miniature faces. Extinguishing andother emergency controls and warning lights are arranged below
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