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Aviation History
1957
1957 - 0106.PDF
106FLIGHT, 25 January1957 MAIN P"KSU EMtRGENCT PRESSURE EMERGENCY RETURN Bomb-door circuit in the new 3,000 Ib/sq in hydraulic system. Main undercarriages are delivered from iarry Hydraulics Division. CL-28... - months after producing final drawings. The steerable nose gear differs from that of the Britannia in retracting to the rear, by Faireyjacks. This change was necessitated by the proximity of the search radar, which has also forced Canadair to adopt a complex doorarrangement. The outer doors covering the nosewheel bay are lightly built fairings incorporating the rear portions of the radome.The inner doors, which are tied to the lower set by linkages, are very strong and are structurally capable of standing up to waterimpact during ditching. In the hydraulic system—by Jarry—the operating pressure is3,000 lb/sq in. Although the component and pipe weights are inevitably greater (by some 21 lb) than those in the 4,000 lb/sq insystem of the Britannia the penalty has been accepted in order to use available American or Canadian components. Each enginedrives a Sundstrand constant-speed unit through which shaft- power is taken to drive the main alternators and, on the innerunits, the two hydraulic pumps. Both pumps are by Vickers, Inc., and have an output of8.5 gal/min. Services supplied include bomb doors (a line diagram clarifies the bomb-door circuits), flaps, control locks,steering, undercarriage and wheel-brakes. All components are exceptionally easily maintained; the main circuit panel is on therear face of the forward weapons bay and the panel for the elec- trically energized emergency system is on the rear wing spar, bothpanels being accessible in flight. The main reservoir is held at 12 lb/sq in above ambient pressure by a bleed from the armamentpneumatic system. The four Sundstrand-driven alternators are each rated at 40 kVAand they supply a fully paralleled automatically controlled and protected system generating three-phase power at 208/120 volts.The D.C. system works at the conventional 28 V and the battery- supplied emergency system feeds loads at 115 V, three-phase.An exceptional proportion of the total electric power is utilized by the avionic systems, with precise frequency control. Provision is made for a crew of 15. The flight deck is arrangedfor two pilots, with duplicated controls, and is spacious and com- fortable. Owing to the absence of pressurization loads the win-dows are very large and deep. Each pilot has a conventional wheel-type control on a vertical pedestal, in contrast to the ram'shorns of the Britannia. The autopilot is the Bendix-Eclipse PB-20. A flight engineer's station is provided on the starboard side andthere are multiple stations for radar signallers, navigators and observers. One of the latter sits in the low-level attack stationin the transparent nose and there are dished observation windows at the rear. Full provision is made for galley and crew-restinstallations. Test rigs for the CL-28 systems have been built since 1954and, ui view of the sound basis upon which the whole aeroplane is designed, it seems very unlikely that any serious trouble will bemet in the future. The presently completed machine—20710—is not a prototype but is the first off a true production line, fromwhich succeeding aircraft will foUow at regular intervals. Already several CL-28s are m final assembly and the second fuselage wasdelivered for static (destruction) testing as early as last October. When 20710 flies it will be complete in every detail, the auto-observers and other test gear being readily accommodated in ion to all operational equipment,the original order for 13 aircraft has been added a further radar mounted in the chin position. The latter is a particularlygood location for such equipment and the general arrangement is similar to that used on the Shackleton MR.l (although the equip-ment is more powerful on the Canadian aircraft). Another very obvious item is the MAD (magnetic airborne detector) installationhoused in the "sting" fairing at the rear end of the fuselage. There are many other dielectric areas and the whole upper part of thevertical tail is structurally isolated to act as an aerial. It is probable that a receiver for Sarah will also be fitted (made under Ultralicence by Canadian Aviation Electronics). In addition, Com- puting Devices of Canada have developed ANT AC (air naviga-tion and tactical air control) specially for the CL-28; it is likely to prove a development in instrumentation of great significance.Wing and tail structures do not greatly differ from those of the Britannia (described in detail on July 6 last). Fuel capacity is6,800 Imp. gal, compared with 6,670 in the Britannia 102 and 8,486 in the Britannia 312. The fuel is 115/145-grade petrol andit is contained in inter-spar bags. De-icing is effected by hot air from Janitrol heaters, of which there are two in the fuselage (oneach side of the forward weapons bay) and one in the tail section to heat the empennage (Napier Spraymats are on the elevatorhorns). The bonded secondary structure in the leading edges employs FM.47 in place of the British Redux. As already noted, the flying controls are generally similar tothose of the Bristol machine. There is one major change, intro- duced to meet the requirements laid down for high rates of roll,particularly during attack operations at fairly low airspeeds. The three-view drawing shows the position occupied by the smallspoiler on the upper surface of each wing immediately outboard of the outer nacelles. There is much to be said for such surfaces,actuated asymmetrically by application of heavy aileron deflection. Each spoiler has to flick fully up in about 0.6 sec, a factor whichcomplicated the design. Similar surfaces are used on the Neptune. Flap geometry is very like that of the Britannia. An appreciablesaving in weight (some 25 lb) has resulted from the use of ball- bearing screw-jack rams (now used throughout N. America) whichgreatly reduce the required flap-motor torque. Perhaps the greatest single difference between the Britannia andthe CL-28 is mat the latter is powered by Wright Turbo-Com- pound piston engines. The turboprops of the airliner, althoughvery efficient at high speeds and altitudes, could not approach the economy of the piston engine for long patrols at low levels Each engine is an R-3350-34W, rated at 3,500 h.p. without water,and driving a 15ft 6m Curtiss electric three-blade propeller. Much of the firewall and nacelle structure is of titanium alloy(it has a darker appearance man the polished aluminium-alloy sheet used elsewhere) and it is calculated that on each CL-28 atotal of 600 to 900 lb of titanium does the work of 1,800 to 2,700 lb of stainless steel. Canadair built a special outdoor test stand forthe complete powerplant installation in 1955, and over 250 hours had been completed on this by last October. One of the pro-grammes was a sound-measurement investigation, in which a test section of CL-28 fuselage was placed in the correct relative posi-tion beside the propeller of the ground-running rig. Noise is an important factor in an aircraft with great endurance and theCL-28 is very well soundproofed. One incidental advantage of the switch to Turbo-Compounds isthat there is no jet pipe in the CL-28 nacelle. As a result the bogie on each main undercarriage leg does not have to fold through morethan 60 deg with respect to the leg. In the Britannia the bogie has to fold completely flat, requiring a special auxiliary hydrauliclack; the reduced movement in the CL-28 bogie can be introduced mechanically by a simple coupling linking the main radius rodto the upper half of the anti-shimmy scissors. The resultine elimi- nation of jacks and sequence valves has saved 12 lb on each unit t JTy ^T^1111" W3S *5 &°Ta,head firm which won the contractfor the CL-28 main gear (and for the hydraulics, of which more is said later, as well as the feel simulator and flying-control locks)and they completed the first set of main-undercarViage u^itt five reported to have raised the"'mi toToT' F^eTorders mayTe c^eval^S ST^T S"^ ^^ -e CL-28 has Xdyoeen evaluated bv the U.S. Navy and it mav wrfi find y
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