Fuel Miser
(continued) Unlike some other PT6 installations the Avanti uses only two levers to control each engine. The throttle controls engine power, and when lifted and pulled aft puts the propellers into reverse. A companion lever provides fuel shut off for engine start and stop, selects idle speed, and controls propeller rpm. With the engines and props behind you and out of sight it's easy to forget that you are in a turboprop and not a jet.
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A redesigned interior is one of the important changes in the Avanti II with new large single-piece side and overhead panels that create a smooth and substantial appearance. The cabin chairs are also new and, in addition to the expected plush leather, there is a wide range of tracking, sliding inboard and swiveling functions. This Avanti owner chose the forward two-place divan option.
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The Avanti has electrically controlled and hydraulically actuated nosewheel steering through the pedals. A button on the control wheel selects either taxi mode with large authority to spin the airplane on the ramp, or takeoff mode with limited authority to control direction at higher speeds. Pilots coming out of other turboprops, or even jets, that have direct mechanical nosewheel steering may find the system sensitive and a little hard to get used to, but I found it to be precise and predictable on taxi. It's all in what you are used to, and any pilot can learn to adjust to the system.
While the Avanti may require less runway than some jets, its runway speeds are high, particularly for a turboprop. The tiny wing has an enormous slotted flap that tracks far aft to add considerable wing area and low speed lift, but it is still a small wing to lift the 12,100 pounds the airplane can weigh for takeoff. At that maximum weight rotation speed is at 120 knots, which is higher than for most newer design jets. With both engines running the Avanti clears a 50-foot obstacle in about 3,300 feet of runway and there is no requirement to consider the effect of an engine failure in the takeoff calculation as you must do in a jet.
Despite its unusual configuration and appearance, the Avanti has totally conventional flying qualities. The airplane is very stable in all axis. As in many jets, but not turboprops, the horizontal tail leading edge moves up and down to provide pitch trim, and it is very powerful and precise. The delta fins under the tail are so effective that there is no need for the yaw damper even at high altitude. The only different flying characteristic of the Avanti is at the stall, where the forward wing quits flying first and as it stalls the nose drops smoothly down no matter what the pilot does with the controls. With the wheel full aft the airplane will bob up and down with the forward wing stalling and recovering on its own.
One other oddity of the Avanti is that when flying in a wet cloud the forward wing loses some of its laminar flow, and if you are hand flying you can feel the nose dip down a little as the forward wing efficiency decreases. It's no big deal and you simply retrim. If the autopilot is flying you'll never notice the change except for maybe a few knots of speed loss. The shape of the leading edges and forward section of both wings is critical to laminar flow performance, and experienced Avanti pilots believe they can see at least a little speed decrease if the leading edges are dirty, bug contaminated, or even if the paint is significantly damaged.
I was aware of the typical turboprop propeller sounds during taxi and takeoff, but once up and climbing that distinct noise seems to recede and the sensation is of being in a turbofan airplane in terms of both noise and vibration. The Avanti climbs quickly with an initial rate of nearly 2,800 fpm at maximum weight. It can be in the low to mid 30s in under 20 minutes, and that is a typical initial cruise level.
We departed weighing 10,900 pounds to see if we could hit the magic 400-knot cruise speed, but air temperature would be the key. The Avanti was climbing at more than 2,000 fpm out of 22,000 feet, but the air temperature was not cooperating with a reading of 12° C above standard. At 31,000 feet, the level for highest maximum speed, the air was still 8° C above, and at maximum cruise with a total fuel flow of 770 pounds per hour, the Avanti gradually accelerated to 383 knots true. Not quite 400, but still impressive for an airplane with such a large cabin and for so little fuel.
Up at 35,000 feet where the air was still above standard temperature we set up a more typical cruise profile of 600 pph fuel to cruise at 367 knots true. The fuel planning rule of thumb is to burn 800 pounds in the first hour for taxi, takeoff and climb, and then 600 pounds in subsequent hours. At lighter weights the Avanti can reach its certified ceiling of 41,000 feet, where fuel flow drops to around 450 pph and cruise speed is about 330 knots. The 9 psi pressure differential keeps the cabin altitude at 6,600 feet at that altitude, and no-wind range can stretch out to about 1,400 nm.
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