Learjet 75

By Fred George fred_george@aviationweek.com
Source: Business & Commercial Aviation

Fuel is stored in left and right wet-wing tanks, plus an aft fuselage tank, in keeping with long-standing Learjet design protocol. A single-point pressure refueling receptacle ports fuel into the fuselage tank, which then flows by gravity into the wing tanks. DC boost pumps supply fuel for engine start, APU operation and cross flow. After start, left and right jet pumps, using motive flow from the high-pressure engine-driven fuel pumps, transfer fuel to the feeders and supply the engines.

Bleed air is used for wing, engine inlet and horizontal tail anti-ice protection, plus air-conditioning and pressurization. As noted, the APU supplies bleed air on the ground for heating and air-conditioning. DC electric heaters are fitted to the probes, sensors, windshields, cockpit foot warmers and the baggage compartment.

A single, 3,000-psi hydraulic system using conventional mineral MIL-H-5606 red fluid, powered by left and right engine-driven pumps, supplies actuators for landing gear, spoilerons, flaps and thrust reversers, plus the wheel brakes. A DC aux pump provides power for the brakes prior to engine start, plus the landing gear and flaps if the engine-driven pumps fail in flight.

The Learjet 45/75 are the first Learjets to be fitted with trailing-link landing gear. Rolling stock, including carbon disc/rotor brake heat packs, is considerably larger than in any previous Learjets, providing excellent stopping power.

Let’s Go Flying

The Learjet 75 has excellent cockpit ergonomics, having 220 deg. of visibility out of the windshields and side windows. The quiet, dark cockpit design of the Model 45 is carried over to the Learjet 75. But the main lighting switches have been moved to an overhead panel, a first for a Learjet. They're still toggle switches. We'd prefer the quiet/dark annunciator light switches as used aboard some other business jets.

Bombardier's Vision flight deck, fea–turing Garmin G5000 avionics, uses three, portrait configuration, 14-in. displays that provide a wealth of information, especially compared to the original Primus 1000 avionics package. A pair of touch-screen controllers (TCSes) replaces the conventional FMS CDUs, radio tuning units, audio control panels and display controls, plus the rotary system test knob.

Building a flight plan is more akin to using an iPhone or iPad as compared to punching in characters on a traditional FMS keyboard. TCS icons pretty much guide you through the process. The touchscreen virtual keypad, concentric knob controls or graphic flight planning can be used to select waypoints, procedures and airways. As with all Garmin navigation systems, comm frequencies are part of the database and they can be selected for use by the VHF comm transceivers at the touch of a virtual button.

Bombardier sales engineer Matthew St. Cyr aptly describes the system as “Apple for avionics” because Vision using G5000 is easily discoverable and seldom leaves the crew asking, “What's it doing now?” More features will be added after deliveries begin in early 2014, including full takeoff and landing performance computations and full FANS-1/FANS-A functionality.

Virtually all of the systems functionality is carried over from the Model 45 to the Learjet 75. Automated functions are retained but so are some manual functions. Boost pump operation, for example, is completely automatic unless cross flow is needed. But the pressurization system still requires the crew to program in the landing field elevation. That function is not linked to the new Garmin FMS.

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