The Avanti does, however, have a number of features typically found only in jets, including single-point pressure refueling and heated wing leading edges for ice protection. Fuel is carried in the wings and in tanks in the fuselage. Fuel management for the crew requires nothing more than to have enough onboard, or to occasionally transfer fuel from side to side if an imbalance occurs. All of the feeding from various tanks is automatic, as is the fuel distribution to the tanks when the line crew hooks up to the single point refueling port under the right wing root.
The heated leading edges of the main wing are different in that they do not get so hot that paint is blistered. In most jets the leading edges are heated to hundreds of degrees to vaporize moisture on contact, but paint can't endure those temperatures so they have bare polished leading edges. The Avanti's wings are hot enough to prevent ice, but not so hot as to blister the paint. The forward wing has a very thin, almost imperceptible electric heating blanket that keeps it ice free. The engine inlets have pneumatic boots that inflate automatically to remove ice when the ice detection system activates. The vertical and horizontal tails require no ice protection, and the windshields are electrically heated.
The five-blade Hartzell propellers need no ice protection because the hot exhaust is blasted over them continuously. The propellers have delivered excellent performance and reliable service, but their far aft location does make them susceptible to damage from debris kicked up from the runway or taxiway. Piaggio does offer a fender that is mounted just to the rear of the nosewheels that helps prevent stones and debris from being kicked up, but the airplane is still not intended for unimproved runways.
The baggage compartment is located above the wing and aft of the rear fuselage pressure bulkhead and can hold 44 cubic feet of cargo. Soft-sided luggage works best because the compartment curves to conform to the shape of the fuselage. The cabin door is another unusual feature, with a lower half that swings down to form an airstair, while the upper portion of the door has a forward hinge. The door is a combination of the traditional Learjet clamshell and the swinging door of a Citation.
Part of the upgrade to the Avanti II, in addition to the change to Pro Line 21 avionics and the more efficient engines, is a new interior. Large sections of the side panels and overhead are created in single pieces, giving the cabin a very solid and luxurious finish that rivals any midsize jet. There are several cabin options with the core being a club four arrangement in the rear where the cabin cross section is largest. Many select a two-place divan forward along with another single seat. All cabin arrangements have a private and sizable lavatory aft that can also be used as a passenger seat for takeoff and landing. The seats are also new and have the same comfort and adjustment range you would expect in a midsize jet.
The Collins Pro Line 21 system transforms the cockpit of the Avanti II, compared to the original that had early generation EFIS equipment. The three big flat-panel displays of the Pro Line 21 system have all of the capability you expect in a turbine airplane with the MFD in the center showing all engine instruments as well as maps, navigation and satellite weather. A single Collins FMS mounted in the pedestal handles the navigation chores, and a radio management unit in the panel is used to dial in frequencies.
Learjet contributed much to the cockpit design during the original partnership when the airplane was developed in the 1980s and the lineage is evident. There are no overhead switches or gauges, and systems are controlled by toggle switches instead of the now more common push buttons. The pointy nose and swept shape of the fuselage means the cockpit is not as roomy as the maximum size of the cabin would indicate, but it is reasonably comfortable. The windshields that are faired so smoothly into the fuselage provide good visibility, except in the climb where, as in many airplanes, the view forward is blocked at higher deck angles.
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.
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.