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Aviation History
2004
2004-09 - 0724.PDF
should they fall prey to hangar rash, they can be unbolted and replaced. The oval-section fuselage is of conven tional monocoque construction and is built for operation up to 51,000ft. Extensive use of single-part machined components has dramatically reduced the parts count. The passenger cabin directly benefits from the wing design, as it features a flat floor for its entire length. Maximum headroom, while it does not allow the pas senger to stand up, is a reasonably gener ous 1.5m. The oval shape of the cabin and its slightly greater maximum width com bine to give significantly more head and shoulder room than offered in the Encore. The standard Lear jet 40 interior has seat ing for six, four in a club arrangement and two in aft forward-facing seats. An exter nally serviced toilet is standard, and can acc ommodate a seventh passenger if the belted lavatory option is purchased. The aircraft seats two fewer people than the Learjet 45, yet has a cabin that is only 620mm shorter. Bombardier has put the extra cabin volume to use by installing a full-size galley and coat closet opposite the cabin entry door. The Learjet 40's powerplants are the same as for the Learjet 45, two Honeywell TFE731-20AR turbofans. The engine is a two-spool design with geared fan and a thermodynamic rating of 4,4601b thrust (19.8kN). As installed on the Learjet40/45 they are flat-rated at 3,5001b thrust up to 31°C (88°F) at sea level. Each is controlled by a single-channel digital electronic engine control (DEEC). A conventional hydro- mechanical control module backs up the DEEC. Nordam-supplied hydraulically actu ated thrust reversers are standard on the Learjet 40, quite a feature for a light jet. To increase directional stability on slippery runway surfaces, maximum reverse-thrust Nj is reduced as ground speed decreases. Safety by design Unlike some light jets, the Learjet 40, as a derivative of the recently certificated Learjet 45, meets stringent Part 25 require ments. One important area where this is apparent is in the design of the flight-con trol system. The primary flight controls are mechanically operated surfaces with inte gral balance tabs. In the event of a jammed elevator, the pilot and co-pilot control columns can be disconnected to allow each to operate one side (left/right) of the elevator. Redundant elevator and rudder control cables are routed on the top and bottom of the tailcone area, reducing the chances of a burst engine rotor severing all control runs to the tail surfaces. Similar redundancy is provided in the roll axis. In addition to ailerons, the Learjet 40 has a single hydraulically actuated fly-by- wire wing spoiler on each side. A sensor in BOMBARDIER LEARJET 40 GENERAL ARRANGEMENT Length overall Wing span Wing area Accommodations Cockpit crew 16.92m 14.56m 28.95m2 2 Passengers 6 standard/7 max Landing dstance (SL, ISA, MLW) Powerplant 2 x Honeywell TFE731-20AR @ sea level up to ISA +16°C 811m 3,500lb Basic operating weight Maximum take-off weight Maximum landing weight Maximum fuel load Limit mach Take-off distance (SL, ISA, Maximum operating altitude Range (6 passengers, 2 crew NBAA IFR reserves) MTOW) 6,091kg 9,231kg 8,709kg 2,438kg 0.81 1,306m 51,000ft. 3,300km the captain's yoke controls the spoilers. In the event of jammed ailerons, the captain can disconnect his yoke from the ailerons with the flick of a column-mounted switch. The system operates like that in Bombardier's Challenger 300. Once discon nected the captain can maintain roll control solely with the spoilers. The Learjet 40's heritage also pays divi dends when the rubber hits the road. Its trailing-link main landing gear has dual tyres and brakes. The carbon brakes have brake-by-wire control with independent anti-skid systems for each wheel. As blown tyres are a common cause for rejecting a take-off run, dual tyres on each main gear assembly reduces the chances of a single blown tyre being misidentified as an engine failure. If a rejected take-off is initiated, dual tyres and brakes increase the odds of keep ing the aircraft on the runway and slowing it to a stop without running off the end. Overall cockpit design of the Learjet 40 employs the dark panel concept: lights are off for normal operations. System control panels are on the bottom of the forward instrument panel. System schematics are logically arranged, allowing intuitive opera tion of their respective controls. Notable for their operating simplicity are the electrical and ice protection systems. The 28V DC electrical system has two engine-mounted starter/generators, as well as two main and one emergency battery. Either engine gen erator alone can provide sufficient power for night instrument flight rules operations. Automatic load shedding and fault protec tion features make the electrical system's operation essentially automatic from the pilot's perspective. The anti-ice system uses engine bleed air to heat wing and horizon tal-stabiliser leading edges as well as engine nacelles. A nose-mounted ice detect probe alerts the crew to icing conditions, and automatically turns on protective systems. Enhanced avionics The Learjet 40's avionics are Honeywell's Primus 1000, but not all such systems are created equal. The Primus 1000 in the Citation XLS has three 255 x 200mm liq uid-crystals, while the Learjet 40 has four 200 x 180mm cathode ray tubes. "Maximum headroom, while it does not allow the passenger to stand up, is a reasonably generous 1.5m1 i" www.flightinternational.com FLIGHT INTERNATIONAL 18-24 MAY 2004 57
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