FLIGHT TEST: Hawker 4000 - Beyond the horizon

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When it was announced in 1996, the Hawker Horizon was to be one of the first business jets to enter the new super-midsize niche, with certification and initial deliveries to begin in 2001.

After a 14-year development programme and a rebranding, the Hawker 4000 achieved its amended type and production certification on 6 June 2008, with the first customer delivery taking place less than a fortnight later on 18 June.

mike-gerzanics-hawker-4000 
 © Mark Donaghue

The 4000 continues the Hawker tradition in looks and performance. Ice-detection probes control the de-icing system (top left) vortex generators (left) test pilot Gerzanics took the left seat

With the wait finally over, Flightglobal in early September was able to see first hand how this newest super-midsize business jet stacks up against the host of competitors that emerged in the seven years between the forecasted 2001 delivery date and eventual arrival of the Hawker 4000.

Those rivals include the Gulfstream G200, nee IAI Galaxy, which entered service in 2000 the Embraer Legacy 600, entering service in 2002 and Bombardier's Challenger 300, first delivered in 2004.

While the Hawker 4000's extensive delay can be attributed to any number of factors, the primary reason may have been attempts by Raytheon (now Hawker Beechcraft) to develop three aircraft simultaneously: the Premier I light business jet and T-6 Texan single-engined turboprop trainer as well as the 4000.

A primary feature of the Hawker 4000 is its cabin. When it was launched, the $20.9 million composite/metal aircraft promised to have the segment's second-largest cabin at 21.6m3 (762ft3), slightly smaller than the $22.8 million G200's 22.7m3 cabin.

Embraer's ERJ-135-based Legacy 600, with its 46.7m3 cabin, straddles the super-midsize and large-cabin segments but costs $4.5 million more than the Hawker 4000. Of the 4000's competitors it is the Challenger 300 that most closely replicates its capabilities and comforts.

The Challenger 300 is priced slightly higher than the 4000 at nearly $21 million, and offers a cabin volume of 23.2m3, although Hawker Beechcraft says its rival has optional features that are standard on the Hawker 4000 - add those to the base price of the Challenger 300, it says, and it rises to $21.6 million, $1.7 million more than the Hawker.

The Hawker 4000 price advantage is even greater when standard features such as dual inertial reference units (IRU) and auto-throttles are considered, neither of which are available in the Challenger 300.

With maximum fuel, the Hawker has an NBAA instrument flight rules range of 5,808km (3,136nm) while carrying a payload of eight passengers and their baggage - 726kg (1,600lb).

For the Challenger 300 with eight passengers and baggage, Bombardier reports an NBAA IFR range of 5,741km. With four passengers and baggage, however, the balance tilts in the Challenger's favour, with a range of 6,067km, slightly greater than the Hawker's 5,941km.

SIMILAR CABINS

As with payload and range capabilities, the passenger cabins of the Hawker 4000 and Challenger 300 are similar: both offer a double-club seating arrangement, with galley forward and lavatory aft. Both have a flat floor and stand-up height - 1.83m for the Hawker and 1.85m for the Challenger.

Cabin length devoted to the seating areas is roughly the same for both aircraft, but the Challenger's larger cabin width at the sidewalls - 2.18m compared with 1.97m for the Hawker - would seem to give the Challenger's passengers more seated room, although Hawker Beechcraft says that, as installed, the Hawker has 12mm wider seats and a 25mm wider aisle.

From the cockpit partition to the lavatory aft wall, the Hawker's cabin, at 7.62m long, is 0.41m longer than the Challenger's. This extra length provides two closets opposite the galley, one more than the Challenger.

Although the 4000 is a clean-sheet design, its creators ensured the aircraft looked and performed like a Hawker. The midsize Hawker 800 series, as exemplified by the 900XP has always been a load-and-go aircraft.

The 4000 is no exception, at maximum take-off weight, eight passengers and full fuel can be accommodated. The cabin entry door's placement low in the fuselage echoes that of the 900XP.

In the cockpit, the heritage is even more evident. The stepped-forward panel glare shield of the newer 4000 reflects that found in the 900XP, and the distinctive ram's horn control yokes are a definite indication the 4000 is a Hawker.

Where the 4000 diverges most from its older midsize stablemate is its composite fuselage. Hawker Beechcraft has been at the forefront of composite business aircraft development, starting with the turboprop Beechcraft Starship in the early 1980s.

The Starship used a hand lay-up process, which proved to be expensive and time consuming.

Composite construction offers many benefits, but Hawker Beechcraft has been judicious in its use.

The Premier I represented the company's second generation of composite manufacturing techniques, highlighted by a highly automated lay-up process for its two-piece fuselage.

While the Starship was nearly an all-composite aircraft, only the Premier I's fuselage, fairings and some control surfaces were made from composites.

The 4000's fuselage, with a larger diameter than the Premier I's, is constructed using the same basic process.

To achieve the desired cabin size, the 4000's fuselage is built in three sections, with each section defined by an all-aluminium mandrel that represents the interior mould line or shape.

The sections are placed on a computer-controlled "Viper" fibre placement system built by Cincinnati Machine.

The Viper places fibre at a rate of up to 45.7m per hour with an accuracy of 0.0127cm (0.005in). Two graphite layers surround an internal NomexTM honeycomb core, yielding a shell that is on average about 25.4mm thick. After lay-up, each section is cured for 8h in a large autoclave. As with the Premier I, composites are used primarily for the 4000's fuselage and fairings.

The demonstration aircraft for our flight, US registration number N7007Q, is the seventh aircraft manufactured and the first to be fully type compliant. I was struck by the aircraft's smooth surfaces as I approached it at San Jose airport. The composite fuselage is devoid of rivets, reminding me more of a high-performance glider than a business aircraft.

The conventional aluminium supercritical wings, built by Fuji Heavy Industries in Japan, feature single-piece top and bottom skins to maximise laminar flow.

The wings are swept to 28.4°, as measured at the quarter-chord point, with full-span bleed air anti-iced leading edges. The only protrusions on the upper surface are 12 vortex generators, about 12mm high, forward of each of the conventional ailerons, installed to prevent aileron flutter at high speeds.

During testing at VDIVE conditions at M0.91, Hawker Beechcraft detected a flutter condition that was excited in the ailerons.

Dan Weatherford, the Hawker 4000 chief demonstration pilot, who accompanied me, says aileron flutter was not perceptible at the pilot station when he performed some of the VDIVE testing - the condition was revealed through flight-test specific instrumentation.

Joining the three cabin sections are two "splice bands" visible as slight bumps in the fuselage mould line over the wing. The wing's fore and aft spars align with the mid-fuselage section's ends, allowing the single piece wing assembly to be joined at the splice bands for a robust structure.

Weatherford conducted the pre-flight inspection, which started at the entry stairs. Notable on the nose gear assembly were two hydraulic cylinders for the Hawker's steer-by-wire nose wheel steering system.

The NWS, controlled solely by a conventional tiller on the captain's sidewall, provided for displacements of +/-70° from centreline.

The four large electrically heated cockpit windows feature a rain repellent coating, making windshield wipers and blowers unnecessary. Fixed high-intensity landing and taxi lights with flush covers are in the lower portion of the wing-body fairing.

The short main landing gear assembly is a trailing link design that retracts into the fuselage. Single point refuelling can be controlled from either the exterior panel forward of the right wing root or from the cockpit.

System fuel capacity is 6,622kg, divided equally between two internal wing tanks. The 4000 can also be over-wing gravity refuelled. Prominent on the vertical stabiliser are two ice-detection probes that control the fully moveable horizontal stabiliser's leading edge electro-magnetic expulsive de-icing system.

While the tail-mounted auxiliary power unit had made discussion on right side of the aircraft difficult, as we rounded the tail we were able to converse at normal voice levels.

External access to the heated and pressurised 2.51m3 aft baggage compartment is afforded by a chest-high 648 x 762mm door just forward of the left engine inlet.

The sizable compartment has a 410kg capacity, greater than the Challenger's standard 225kg. The baggage compartment can also be accessed in flight at altitudes below 35,000ft through a door in the lavatory. Entry into the cabin is via an electrically operated door with integral steps.

Like the 900XP, storage bins are provided in the steps for "remove before flight items". Unlike most business jets whose entry doors are secured either by pins or over centre locks, the 4000 door is a plug type that offers an additional level of safety.

Once strapped into the left seat, I used the centre pillar-mounted reference blade to attain the design eye position. Overall, the flightdeck is well arranged, with aircraft system controls on the small overhead panel.

The avionics package includes a Honeywell Primus Epic system with five 8 x 10in LCD displays and a level of equipment unmatched at its price point. Dual laser IRUs, dual GPS navigation units, dual flight management system (FMS) units and a full authority auto-throttle are standard.

The five displays give each pilot his or her own primary flight display and multifunction display, with the centre fifth display typically used for the engine instrument and crew advisory system (EICAS).

The usual traffic alert and avoidance and enhanced ground proximity warning systems are available as well as displays of map and radar information. In addition, system synoptic displays and checklists can be shown on the MFDs.

Available synoptic displays are ECS and doors electrical flight control hydraulics bleed-A/I fuel and maintenance.

During my flight I found the various system synoptic displays to be logical and easily interpreted, greatly aiding my understanding of system operation and actual status.

The Honeywell-built cursor control device (CCD) on the left-hand (right hand for the right seat) side console fell readily to hand. The CCD is similar to the Honeywell unit in the Boeing 777.

Each pilot's cursor can only be navigated within his or her own-side PFD and MFD as well as the "shared" centre EICAS display. Movement from display to display is via three buttons at the forward edge of the device.

hawker-4000-flightdeck 
 © Mark Donaghue
The well-arranged flightdeck adds Honeywell Primus Epic avionics to heritage ram's horn control yokes

Within each display the touchpad allowed for rapid and accurate cursor positioning. Touching along the perimeter of the touchpad rapidly moved the cursor to a corresponding position on the actual display, a handy feature.

A dual-twist knob forward of the touchpad allowed for scrolling of pull-down menus, scale selection of certain displays as well as radio frequency and altimeter settings.

Compared with the trackball-type CCD in the more advanced Dassault EASy flightdeck, I much preferred the Hawker's touchpad.

The IRUs, which had started their alignment when APU power was available before the walkaround inspection, were fully aligned using GPS position information before engine start.

The current FMS load gives the Hawker a required navigation 4 capability, with RNP-1 and RNP-0.3 scheduled for future implementation. Pre-start flow steps were low in number, with the primary item being turning off the two air conditioning packs.

Engine start was accomplished by arming each engine's guarded "IGN" switch, with a push of the fuel/IGN button initiating the start sequence.

APU bleed air rotated the high-pressure spool as the FADEC controlled the start. Each of the Pratt & Whitney Canada PW308A engines attained steady-state idle less than 35s from initiation.

As each engine-driven generator came up to speed, the electrical system automatically configured itself for normal operations. The engines each provide 6,900lb of thrust (30.7kN) at sea level and are flat rated to ISA 22°C (71.6°F).

The large temperature margin inherent in these engines helps provide the 6,000h time-between overhaul interval, with hot-section inspection due after 3,000h.

The parking brake was released after the packs were brought online, flaps set to 12° and a control sweep performed. Idle power alone started the aircraft rolling. During the short taxi to Runway 30L, I found the NWS to be very responsive, allowing for accurate tracking of taxiway centrelines. One welcome improvement over the 900XP is the 4000's conventional NWS tiller.

The 900XP's is a large round knurled knob that I had found awkward to manipulate during my recent demonstration flight, while the 4000's was more akin to tillers on large transport. The brake-by-wire carbon brakes were easily modulated by pedal toe pressure, keeping taxi speed moderate.

With equipment and one passenger weighing 227kg, our test day Hawker had a zero-fuel weight of 10,614kg, slightly less than the published basic operating weight of 10,659kg. The basic weight includes allowances for water and galley provisions as well as unusable fuel and oil. Weatherford computed take-off data using a paper look-up chart as an FMS-based capability is still under development.

TAKE-OFF

With 2,631kg of fuel, he computed a balanced field length of 971m. At an MTOW of 17,916kg and standard conditions, Hawker Beechcraft lists a take-off distance of 1,569m.

Once aligned on the runway, pushing the throttles forward allowed the armed auto-thottle system to engage at 60kt (110km/h) indicated irspeed and set take-off power at 95.3% N1.

Acceleration was quite rapid, given our light weight. Passing through an indicated air speed of 80kt, I moved my left hand from the tiller to the yoke, as the Hawker's NWS is not controllable with the rudder pedals. Rotate was called at 111kt and the Hawker leapt into the air after a ground roll of less than 800m.

The yoke-mounted electric pitch trim easily zeroed out the changing pitch forces as the gear and flaps were retracted and the indicated air speed accelerated to 200kt.

Once clear of the class C airspace (generally 4nm/7.4km), a climb speed of 250kt was established. The flight director's flight-level change mode provided good pitch guidance as the auto-throttle maintained climb power.

During numerous air traffic control-directed intermediate level-offs, the auto-throttle retarded power to maintain the desired speed, greatly easing the task of flying the Hawker. Passing 10,000ft, an indicated air speed of 280kt was held until Mach 0.80 was intercepted.

During the climb I engaged the autopilot, using the heading mode to comply with air traffic control vectors and flight-level change to maintain climb schedule.

Once cleared direct to a point on our flightplan, engaging the NAV lateral autopilot mode took the aircraft directly toward the point. Less than 23min after brake release and a fuel burn of 508kg, the Hawker levelled at FL430.

At MTOW, Hawker Beechcraft lists time to climb to an initial cruise altitude of FL370 as 14min, and FL430 as 25min. The Challenger 300 and Hawker 4000 have nearly identical thrust to weight ratios and wing loading, two key factors in defining climb performance. Given their similar attributes it should come as no surprise that the Challenger's time to climb to FL370 is also listed as 14min.

Level at FL430 the 12,700kg aircraft was accelerated to a high-speed cruise point, where 96% N1 and a total fuel flow of 826kg/h maintained M0.83, just below the MMO of 0.84.

At near standard conditions the Hawker's indicated airspeed of 235kt yielded 476kt true airspeed. The Hawker's M0.83 cruise capability is the highest in its class.

LINEAR TRADE-OFF

Slowing to a long-range cruise speed of M0.775 gave a true airspeed of 446kt and dropped total fuel flow to 762kg/h. With six passengers and baggage (544kg), the Hawker's NBAA IFR range at M0.78 is listed at 5,871km.

Pushing the speed to M0.82 with the same payload drops the range less than 6% to 5,537km. As that data shows, the trade-off between speed and fuel consumption in cruise conditions is nearly linear and most operators will operate at high-speed cruise for all but the most demanding stage lengths.

At an indicated air speed of 220kt, I accomplished a series of 45° and 60° angle of bank turns. At FL430 there was sufficient excess power to maintain altitude and airspeed with no apparent airframe buffet. Pitch and roll control forces were well harmonised throughout the manoeuvring.

With the autopilot engaged, Weatherford took control of the aircraft and accelerated it to M0.83 as I left the flightdeck to experience the 4000's plush cabin.

 

hawker-4000-interior 
 © Mark Donaghue
Standard interiors feature leather seats with an optional divan

The test aircraft had an optional nine-place configuration that featured a three-place divan in the aft portion of the cabin, which was spacious with comfortable seating. The lavatory had an externally serviced toilet and pressurised hot and cold water.

A belted lavatory option is available, allowing seating for up to 10 passengers. The ambient noise level was quite low, allowing conversation at normal voice levels throughout the long cabin.

The pressurisation system has a maximum delta pressurisation of 665mbar (9.65lb/in2), giving a cabin altitude of 6,000ft at its 45,000ft ceiling. At FL430 on the test day the indicated cabin altitude was only 5,500ft.

Lower cabin altitudes are less taxing than higher ones, and the 4000's high pressure differential should allow travellers to arrive at their destinations less fatigued.

I returned to the cockpit to initiate a descent to intermediate altitude. The power was set mid-range and the aircraft accelerated to MMO.

The clacker sounded at M0.84. Had the autopilot been engaged it would have raised the pitch attitude to avoid an over-speed. Stable at M0.84, a sharp control input in each control axis showed resultant aircraft motion to be well damped.

Speedbrake deployment was announced by slight airframe buffet, and caused a nose-up pitching motion that was easily countered by forward yoke pressure. The throttles were retarded to idle after completing the high-speed investigation, and speedbrakes retracted for a further descent to 16,000ft AGL.

During the descent a number of bank to bank rolls were performed at airspeeds varying from 200-280kt. As was the case at FL430, I found the flight controls to be well harmonised showing the Hawker to be a joy to hand-fly.

DECELERATION RATE

Once level at 16,000ft MSL, the power was set to obtain a deceleration rate of 1kt/s as the 12,338kg Hawker was slowed for a straight ahead clean configuration stall.

At an indicated 118kt, the airspeed tape turned amber to indicate a low-speed condition. At 103kt, the stick shaker activated, prompting me to rapidly advance the power to fly out of the stall. Had the autopilot been engaged during the manoeuvre, it would have been automatically disengaged upon shaker activation.

The next two stalls were in the landing configuration, gear down and flaps set to 35°. Roughly 60% N1 was needed to maintain a deceleration rate of 1kt/s.

The low-speed warning occurred at 108kt and the shaker activated at 97kt for both landing configuration stalls. During the first event the power was advanced to fly out of the stall in level flight.

For the second event, I continued to hold aft yoke pressure after shaker activation and waited for the stick pusher to fire. At 92kt the stick pusher fired, the elevator autopilot servo generating a 27.2kg forward force at the yoke to break the stall.

With the power still set to 60% N1, yoke back pressure was reduced to allow the aircraft to descend and accelerate out of the stall. During the three stall manoeuvres there was no tendency to drop a wing or depart from controlled flight.

Response to control inputs in each axis at slow speeds was predictable, allowing for precise manoeuvring at elevated angle-of-attack conditions.

EXTRA VIGILANCE

After completing the medium-altitude manoeuvres, recovery to San Jose was initiated. During the recovery at 12,000ft MSL, a comfortable cruise indicated air speed of 280kt required a total fuel flow of 1.021kg/h.

The autopilot and auto-throttle were engaged, allowing both pilots to maintain extra vigilance in the crowded terminal area. Additionally, the Hawker's standard TCAS II helped us rapidly gain visual contact on proximate aircraft.

While ATC provided vectors for an approach to Runway 30L, I installed the instrument landing system 30L approach in the FMS. When the approach procedure was installed, the ILS frequency was automatically tuned, further easing pilot workload.

I disengaged the autopilot and auto-throttle and hand flew the aircraft during configuration for the touch-and-go manoeuvre. Due to conflicting traffic ATC kept us higher than normal, and the aircraft was configured landing gear down and flaps 35° in an idle power descent.

The flight display provided good lateral guidance, allowing me to capture and track the localiser. Passing 800ft AGL the glideslope was captured and the aircraft slowed to a VREF indicated air speed of 112kt.

Attitude on final was roughly level until a slight flare to 2° nose-up was initiated about 10ft above the runway. The trailing link landing gear made for a smooth idle power touchdown.

While tracking the centreline, Weatherford retracted the flaps to 12°. I slowly advanced the power to 90% N1 and rotated to a 12° nose-up attitude at 115kt indicated air speed. Once airborne at 150kt and passing 200ft AGL, Weatherford rapidly retarded the right engine to idle, to simulate an engine failure.

Unlike the 900XP, which has a bleed air based rudder bias system designed to reduce the adverse yaw caused by an engine failure, the 4000 lacks that handy safety feature.

While the 900XP's rudder is unpowered, the 4000's is driven by any one of three independent hydraulic systems. Rudder forces in the 4000 are defined by pedal springs, which I judged to be at most 40kg for maximum displacement, well under the certification maximum of 68kg.

With the right engine at idle, about 27kg of force and two-thirds of the available rudder displacement was needed to keep in co-ordinated flight.

While not at identical points, the rudder force required to maintain co-ordinated flight in the 900XP with the bias system turned off was more than double that - around 60kg.

Once cleaned up and at pattern altitude, available rudder trim was sufficient to compensate for the asymmetric thrust condition.

The simulated single engine approach was flown with flaps set to 35°, their maximum deflection. On final approach I centred the rudder trim, and was easily able to co-ordinate rudder deflection with the minor power adjustments needed to stay on speed, still an indicated 112kt. The trailing link main landing gear again made for a smooth touch down.

Once the aircraft had settled on to the ground, the three speed brake panels on each wing automatically deployed. I simultaneously lifted both thrust reverse levers and applied sufficient toe brake force to actuate wheel brake anti-skid protection.

Under moderate braking the aircraft had already slowed to a taxi speed by the time the thrust reversers were fully deployed. Estimated ground roll was less than 500m. Computed landing distance over a 15.24m obstacle for our 11,830kg gross weight was 751m.

At maximum loading weight (15,195kg), a landing distance of 913m is listed. Taxi back to the chocks and post-flight flows were notable only for their simplicity.

The Hawker 4000 represents real value in the super-midsize segment. Priced lower than its competition, its full fuel 726kg payload gives it a true load-and-go capability.

The five-screen fully integrated flightdeck offers standard auto-throttles and dual just about everything else. For over-water flights its dual IRUs, air conditioning packs and back-up hydraulic motor generator should give it near formalised ETOPS reliability.

Features on the horizon promise even more. E-charts will be a welcome addition when Honeywell fields the feature for its small display Primus Epic avionics system.

Planned FMS-based performance computation capability and electronic checklists will further cement the 4000's position as the value leader. It may not have the largest cabin in class, but when fully loaded it can go further than its pricier competitors.

Those who have awaited the arrival of the largest Hawker with bated breath will not be disappointed.

hawker-beechcraft-4000 
 © Hawker Beechcraft
The super-midsize Hawker 4000 has a continent-spanning range and an M0.83 cruise capability