MIKE GERZANICS / GENOA, ITALY
The Piaggo P180 Avanti may look exotic, with its three lifting-surface configuration, but it handles better than most entry-level business jets
First flown in 1986 the Piaggio P180 Avanti traces it roots back to the 1970s, when the world was in the midst of an oil crisis. Back then, the business aircraft market comprised two distinct segments, jet and turboprop. Rocketing fuel prices had pushed jet aircraft operating expenses skyward, with no relief in sight. Turboprops had lower operating costs, but were slower and lacked the panache of jet aircraft.
Italy's Rinaldo Piaggio designed the Avanti to combine the best of both segments: jet-like speeds at turboprop costs. Italian and US certification was obtained in 1990, but sales were weak, and the firm's aviation division entered receivership.
Piaggio Aero Industries was formed in 1998 under the leadership of Piero Ferrari, vice-chairman of the performance car manufacturer. In addition to continuing production of the P166 twin-turboprop utility aircraft, the new company sought to reinvigorate the innovative Avanti. Flight International was able to see if Piaggio has hit its mark during a flight from Genoa.
The Avanti's unusual three lifting-surface configuration is a result of Piaggio's desire to develop an economical high-speed turboprop with a spacious and quiet cabin. To minimise drag, a laminar-flow wing was positioned at the midpoint of the fuselage, aft of the cabin to prevent the spar intruding into the passenger compartment. The aft placement of the wing required a foreplane to balance the lifting moment generated in flight. For pitch control, a tailplane was placed atop the vertical fin.
In a classic canard configuration, the foreplane serves as both horizontal stabiliser and pitch control surface. At first glance the Avanti may look like a canard, but the foreplane is fixed and does not incorporate an elevator. Pitch control and stabilisation is provided by the T-tail's horizontal stabiliser and elevator.
An extra flying surface would seem to be at odds with the goal of producing a lightweight, low drag aircraft. But in practical applications, a pure canard will have a higher stall speed than a conventional aircraft optimised for same cruise condition. Higher stall speeds in turn have an adverse affect on field length requirements. The increased wing area needed in a pure canard to achieve acceptable field performance would have resulted in less than optimal cruise speeds, leading Piaggio to employ a three lifting-surface configuration for the Avanti. Piaggio chief pilot Giuliano Currado says the Avanti is more like a stagger-wing biplane than a canard.
Striking feature
After its wing configuration, the most striking feature of the Avanti is the pusher engines - two Pratt & Whitney Canada PT6A-66s, each flat-rated to 635kW (850shp) and driving a 2.16m (7.1ft)-diameter, five-blade, constant-speed propeller mounted aft of the wing. The pusher configuration has advantages over the traditional tractor layout. Propwash does not interfere with laminar flow over the wing and turbine exhaust gas heats the propeller blades, eliminating the need for de-icing. From a comfort standpoint, the aft-mounted engines place the counter-rotating propellers several metres behind the rearmost passenger seat, minimising their acoustical effect on the cabin.
As we conducted the preflight I was impressed by the smoothness of the aircraft's surface. Production of the Avanti is accomplished at Piaggio's Genoa factory, where the fuselage skin is formed and held to the desired contour in a vacuum jig. Internal stringers and ribs are then flush-rivetted in place. The result is a smooth and ripple-free surface that reduces drag. The walk-around itself was straightforward, and I noted the two ventral delta fins, designed to provide a nose-down pitching moment at slow speeds. Entry to the aircraft is via a two-piece door on the forward left-hand side of the fuselage.
Our aircraft, I-FXRD, was configured with seven leather passenger seats: three forward and four in a club arrangement to the rear. At the aft of the cabin is an enclosed lavatory and baggage closet. The 6m-long cabin is spacious. Its 1.85m width and 1.75m height are greater than both the Cessna Citation III's and Raytheon Premier I's and equal to the Dassault Falcon 200's. A hard partition separates the cockpit from the cabin.
Settling into the semi-reclined left seat, the control yoke and throttle quadrant fell easily to hand. The cockpit is fairly tight, and at my height of 1.78m I found headroom to be just adequate. Instrument charts, approach plates and aircraft manuals were conveniently stowed and readily accessible in two slide drawers aft of the right cockpit partition panel. Field of view out of the two large cockpit windows is excellent.
Clear and clean
The cockpit layout is exceptionally clean, with aircraft system switches located on the lower edge of the instrument panel, itself clear and logically laid out. The standard Rockwell Collins avionics suite seems dated, but is more than adequate for single-pilot operations. In addition to a full complement of navigation and communication radios, the aircraft is also equipped with a GPS receiver and radar altimeter.
Two 127 x 127mm (5 x 5in) cathode-ray tube (CRT) displays at the pilot station act as an electronic attitude director indicator (ADI) and horizontal situation indicator. Engine instruments are analogue round-dial units, with torque and interstage turbine temperature (ITT) gauges at the top of the cluster. A multifunction CRT display in the centre of the panel hosts the weather radar and displays expanded navigation data. The centre console-mounted control display unit is located just aft of the throttle quadrant, a less than optimal position.
Both engines were started using the aircraft's battery. The highest peak ITT was 690ºC (1,275ºF) for the right engine, comfortably below the 1,000ºC limit. Currado guided me through the pre-taxi checks and called for taxi clearance. A slight advance of the power levers was enough to start the aircraft rolling. I engaged the electrohydraulic nosewheel steering (NWS) via a control yoke switch. While at first the NWS seemed overly sensitive, after a little practice I was able to keep the aircraft on painted taxiway lines. Carbon brakes, powered by hydraulic pressure, were responsive.
As part of the before take-off checks, the propeller autofeather system was checked and armed. During take-offs and landings, the system automatically feathers the propeller of a failed engine to reduce asymmetry. The practical benefit of this system is a reduction of air minimum control speed (VMCA) from 128kt (234km/h) indicated airspeed to 100kt. As the lowest published take-off rotation speed (VR) is 103kt; an engine failure should not force a power reduction on the operating engine to maintain directional control.
For take-off the condition levers were set to MAX RPM and flaps to MID, causing flaps on both the wing and foreplane to partially extend. With 919kg (2,026lb) of fuel onboard, the 4,667kg aircraft was well below its maximum take-off weight of 5,239kg. When cleared by the tower, I lined the aircraft up on runway 29 and ran the engines up to 2,760Nm (2,000ft/lb) torque.
I released the toe brakes and advanced the power levers to 2,970Nm. Aircraft acceleration was brisk on the 8¼C day. At 103kt, I rotated the aircraft to an 8º nose-high attitude. The aircraft lifted off the runway after a ground run of less than 550m. Gear and flap retraction caused little change in pitch force as the aircraft accelerated to the climb speed of 160kt. Rate of climb to our intermediate level-off altitude, 8,000ft, was about 4,000ft/min (20.3m/s).
After ATC clearance we turned south to head into our working area, Danger Area 91. With power set to 3,080Nm, I started a 160kt climb to 39,000ft. Torque was kept at 3,080Nm until passing 22,500ft, where the flat-rated engines' performance was limited to 775¼C ITT. The climb from 10,000ft to 39,000ft, during which several turns were completed, took 16min and burned 103kg of fuel. According to the flight manual, a climb from sea level to 41,000ft would take just over 28min and burn 202kg of fuel.
Crisp response
Once level at 39,000ft the power was set to maintain 750¼C ITT and the aircraft accelerated to 191kt/Mach 0.62. Total fuel flow was 227kg/h (500lb/h) as the aircraft cruised at 353kt true airspeed. At altitude a 45¼ bank-angle 180¼ turn was accomplished. Aircraft response was crisp and no airframe buffet was felt at this extreme edge of the flight envelope.
Manoeuvring at altitude complete, I engaged the autopilot in the altitude hold (ALT) and heading modes via glareshield-mounted pushbuttons. Currado then took control of the aircraft and I got out of the pilot's seat to sample the cabin. The ambient noise level was low, with the noisiest location being aft of the cabin.
From the rear of the cabin a conversation with Currado, 3.5m away in the cockpit, was quite easy with only slightly elevated voices. The cabin was quieter than any other turboprop I have been in, and on par with some business jets.
I returned to the cockpit for our next manoeuvre, a simulated emergency descent. After retarding the power levers to idle, I nosed the aircraft into an 8¼ dive. The electric pitch trim easily reduced yoke forces as the aircraft accelerated to its maximum operating Mach number of 0.67. Stabilised there, I performed several sharp pitch and roll yoke inputs. In both cases the resulting motions quickly damped out. With the yaw damper off I did a rapid rudder input to excite a Dutch Roll, which damped out in 3.5 cycles. Passing 22,000ft I held the maximum operating speed (VMO) of 260kt indicated and continued the descent to 12,000ft. After just 6min 18s the aircraft was level at 12,000ft, an altitude where emergency oxygen is not required.
Level at this lower altitude I did a series of sharp control inputs at 260kt. Aircraft response was the same as I had experienced at M0.67. After slowing to 215kt, a 60¼-bank steep turn showed the Avanti to have crisp and predictable handling qualities. At 13,500ft and 185kt, a series of rapid rolls from 60¼ bank to 60¼ bank were performed. Each took less than 2s, showing an near instantaneous roll rate of 60¼/s.
Next the power levers were set to idle in preparation for a clean configuration stall. Slowing at 1kt/s light airframe buffet was felt at 112kt, just as the aural stall warning sounded. Ignoring the warning, I continued to hold full aft yoke and the 4,350kg aircraft settled into a wings-level 3,000ft/min descent at 104kt. Minimal altitude was lost when recovery was effected by releasing yoke pressure and advancing the power. Application of power aided the recovery by pushing the nose over, as the engine's thrust line is above the aircraft's centre of rotation.
A take-off configuration stall, gear down and mid flaps, was accomplished in the same way. A light airframe buffet was felt at 112kt. The buffet decreased in intensity as the aircraft slowed, disappearing at 104kt. At 102kt the stall aural warning sounded as the buffet reappeared. Full aft yoke resulted in a stable 94kt descent. As for the clean stall, recovery was uneventful. A landing configuration stall, gear down and flaps fully down, again displayed the Avanti's docile stall characteristics. No airframebuffet preceded the aural warning, which sounded at 88kt, well below an approach speed of 117kt. Full aft yoke yielded astable 84kt descent. Control responsiveness in all three axes was good, as was the case for the two other configurations.
T-tail performance
Some T-tail aircraft are prohibited from performing full aft stick stalls, as the tail may stall and cause an uncontrolled pitch up. Some T-tail aircraft employ a stick pusher to make sure this does not happen. The ability to hold full aft yoke in a stall makes it hard for the novice pilot to put the Avanti in an unrecoverable situation.
Back in level flight, the gear and flaps were retracted in preparation for return to Genoa. Cleared to fly an instrument landing system (ILS) approach to runway 29 we descended to 4,000ft. With the autopilot engaged in the ALT and navigation (NAV) modes, my only task was to maintain the desired airspeed. An airspeed trend arrow on the ADI aided in this task, as the Avanti was quite responsive to power changes.
The NAV mode manoeuvred the aircraft along the published approach procedure, finally rolling out on a path overlaying the ILS localiser approach course. I selected the approach mode, and the autopilot immediately captured and tracked the localiser.
Just prior to ILSglideslope capture, the gear was lowered and flaps set to MID. At glideslope capture I reduced the power to 550Nm torque per engine to maintain 130kt. At 1,000ft the flaps were lowered to down. Some 830Nm torque was required to hold the reference speed (VREF) of 117kt. The autopilot smoothly tracked both localiser and glidepath until I pushed the go-around button on the left power lever at decision altitude. I advanced the power as the autopilot smoothly rotated the nose up to 8¼ and levelled the wing for the go-around manoeuvre. This mode of the autopilot should greatly reduce pilot workload during one of the most demanding phases of a flight, a missed approach in instrument conditions.
Failure simulation
Once level at 1,500ft on the downwind leg, Currado simulated a failure of the right engine. At 145kt with gear down and flaps MID, about 450N (10lb) of left rudder pressure was required to maintain a steady heading. Rudder trim was sufficient to alleviate rudder forces, but I elected to fly the approach with rudder trim set to zero. Final approach was flown at 129kt - VMCA (assuming inoperative autofeather) plus 1kt. When landing was assured the flaps were set to down and I slowed the aircraft to 117kt. I retarded both power levers a few feet above the runway, and the aircraft settled gently on centreline. The effective rudder easily controlled yawing moments induced by power changes during the approach. Flaps were then set to MID and both power levers advanced to accomplish a touch and go.
The next approach was a visual circuit to a touch and go. Local restrictions necessitated a slightly steeper approach than the ILS I had flown earlier, descent rate on final was 1,000ft/min for a 117kt VREF. As was the case during the single-engine approach, retarding the power just above the runway caused the nose to pitch up slightly, flaring the aircraft. I found it easy to hit the desired touchdown point, an admirable trait when flying into short fields.
The last approach I flew was with no flap, simulating failure of the electrically driven flaps. Pitch attitude on final approach was about 3¼ higher than the full flap approaches at a VREF of 137kt for the 4,128kg aircraft. At 50ft I retarded the power levers to idle, reflecting our low drag configuration. The flare manoeuvre required light back yoke pressure to attain the landing attitude as the power had been reduced earlier.
A touch and go was performed and Currado took the aircraft to demonstrate a steep approach to a simulated short field. At 140kt,with gear and flaps down, he lined up on the runway at 1,500ft. Just as the runway disappeared under the aircraft's nose, he pulled the power to IDLE and lowered the aircraft into a 20¼ dive, aiming about 2,000ft short of the runway. Skillfully executing the flare he touched the aircraft down in the first 200m of the runway. Using reverse thrust and less than maximum braking, he stopped the aircraft in time to turn off less than 800m from the threshold.
A joy to handle
Taxiing back to the ramp and shutting down were uneventful. During the 2h 4min flight (2h 33min block time) we burned 648kg of Jet A. From a handling qualities standpoint the Avanti was a pure joy. Control harmony and resultant aircraft response were excellent.
The twin counter-rotating turboprops provided near-jet speeds, with no propeller- induced yawing as power levels were changed. A ceiling of 41,000ft can get the aircraft above most weather to cruise in smooth air. While the Avanti may cruise slower than most of its jet competitors, a spacious cabin and lower direct operating costs may be more critical to some users.
To date, Piaggio has delivered 48 aircraft, and has firm orders for 20 more, mostly in Europe. Increased penetration into the North American market may hold the key to the Avanti's success. The long logistical trail to Italy has been shortened by the addition of four US service centres, with six more planned. Piaggio is in the process of updating the avionics suite, as people spending $4.9 million want all the latest bells and whistles.
The Avanti may look exotic, but it handles better than most conventional aircraft I have flown. For those not afraid to be different, the Avanti may be the turboprop answer to the question "which entry-level business jet do I buy?"
Source: Flight International
