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Aviation History
1963
1963 - 0713.PDF
GALLEY GALLEY GALLEY TOILET SERVICE / EMERGENCY DOOR / EXITS PASSENGER _ DOOR PASSENGER DOOR COATS EMERGENCY EXITS TOILET Seating plan of a typiccl 727 configuration, with 28 first-class seats and 66 tourist. The layout of the flight deck and the position of the galley area and toilets is standard in all configurations BOEING 727... power package. The latter obviates the need for gust snubbers, control locks or limit stops. Control in the pitching plane is provided by the elevators, and the variable-incidence tailplane provides trimming control. Each elevator has a single main spar, a light rear spar, sheet ribs and bonded skins, together with honeycomb manual-control tabs, horn balance at the tips and five balance panels fitting compart ments inside the rear of the tailplane and driven through hinges on the mass-balance weights on the elevator nose extensions. In normal operation, pilot pitch demands are passed by cables to an artificial- feel and centering mechanism in the fin-tip fairing, and thence through push-pull rods to dual hydraulic actuators (each in A and B systems) driving the port and starboard elevators. Autopilot inputs are fed to a differential linkage on each elevator power unit. Snubbing, limit and locking functions are accomplished by the power units. In the absence of hydraulic power, pilot input auto matically drives the trailing-edge tab, any tendency towards "floating" being minimized by the balance panels. While the elevators are necessary for rotation at take-off and landing, and for manoeuvres required during training and FAA certification, longitudinal control in cruise conditions is accom plished mainly by the trimming tailplane. This is positioned by an irreversible ball-bearing screwjack with an electromechanical drive. The normal a.c. motor drive has d.c. magnetic clutches and is governed by the trim switches on the pilots' control wheels. Direct manual control is provided by the trim wheels on the flight-deck console. A mechanical brake prevents any tailplane motion in opposition to movements of the elevators. A slow-rate actuator provides cruising trim and autopilot servo input. Tailplane limits are +4° to -12J°. The rudder is divided into upper and lower segments, normally operated in unison. Both portions are of two-spar construction with bonded skin panels and full-span metal-honeycomb anti- balance tabs to enable the required power to be achieved from a smaller surface. The upper rudder is driven by a hydraulic actuator in system B; the lower rudder is normally driven by an actuator in system A, but it also has a smaller power unit served by the elec trically energized stand-by hydraulic system C. This not only provides system duplication but also enables the power units to be mounted aft of the fin rear spar. In the linkage between the two power units is a spring centering unit to generate pilot pedal forces. Each rudder has its own yaw-damper channel, which provides directional stabilization without force or motion transmitted to the pilots' pedals. An erroneous hard-over signal applied to either rudder would automatically be compensated by the remaining channel. Fuel All fuel is carried within the main wing box, which is divided into three tanks each normally feeding its own engine. Tanks 1 and 3, respectively in the port and starboard wings, each have a capacity of 1,700 US gal (1,416 Imp gal), and are of integral construction. Tank No 2 has a capacity of 3,600 US gal (2,998 Imp gal), and consists of integral compartments in the port and starboard inner wings supplemented by two flexible cells in the centre section. If a customer so desires, a third flexible cell with a capacity of 500 US gal (416 Imp gal) may be added at the front of the centre section. Pressure-fuelling at 600 US gal/min (500 Imp gal/min) is accom plished through double sockets operating at 501b/sq in located beneath the starboard wing leading-edge about half-way to the tip. The same nozzles may be used for defuelling (at approximately 50 US gal/min each for tanks 1 and 3 and 100 US gal/min for tank 2) under the pressure of the a.c.-driven tank boost pumps. There are two pumps in tanks 1 and 3 and four in tank 2; their capacity is greater than engine demand, and the surplus is available for dumping fuel overboard through jettison nozzles near the wing tips (which are aft of the engine intakes). System instrumentation includes a true mass-flow meter for each engine, a temperature gauge for tank 1, and quantity gauging for each tank both at the fuelling station and on the flight deck (third crewman). Hydraulics The 727 has two independent main systems plus a stand-by system, all operating at a nominal 3,0001b/sq in and filled with Skydrol 500A filtered to 10 microns. System A is energized by two variable-displacement pumps, mounted on engines 1 and 2. It serves the ailerons, elevators, lower rudder, outboard flight spoilers, ground spoilers, flaps (leading edge and trailing edge), slats, undercarriage, and nosewheel brakes and steering. System B is energized by a.c. electric motors and serves the ailerons, elevators, upper rudder, inboard flight spoilers, mainwheel brakes and aft airstairs. System C is energized by a single a.c. motor, and is brought in only following the unlikely failure of both main systems to provide stand-by power for the lower rudder, Kriiger flaps and slats. Service data on the 707/720 has been utilized to improve 727 hydraulics. Extensive use is made of modular packages to minimize the number of tube connections. Metallic element, non-by-pass filters located as near as possible to the pumps preclude the need for extensive system flushing in the event of pump failure. Engine- driven pumps have been chosen on the basis of proven service-life history, and magnetic plugs are used in case drain lines. Flight experience to date suggests that this design care has resulted in a hydraulic system commendably free from leakage. Electrics Each engine carries a constant-speed drive coupled to a 40kVA, 400c/s a.c. brushless generator. Parallel operation provides good capacity utilization and peak-load handling. Although the system is based upon that of the 707 and 720, numerous improvements have been incorporated. In particular, generator bearings and cooling have been improved and a central ized checkout system is incorporated. An essential a.c. bus provides power for safe flight when the rest of the primary system is de-ener- "Flight International" photograph When this picture was taken, the third 727 was having its side engines hung and under going checks on the end of the Renton flight-line
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