FLIGHT TEST: C-27J - No small measure
Nicknamed "half a Hercules
" due to its commonality with the four-engined C-130J, the twin-turboprop C-27J may set the standard for medium tactical airlifters
Based on the Alenia G222 and the C-27A operated by the US Air Force in Central America, the C-27J Spartan represents a significant enhancement of an already capable tactical transport. Offered by the Lockheed Martin Alenia Tactical Transport Systems (LMATTS) joint venture, the C-27J follows the route set by the C-130J in taking a proven design and adding improved avionics and propulsion. Rather than develop unique systems for the Spartan, LMATTS borrowed them from the C-130J. Development time and costs were minimised as proven systems were readily available, and life cycle costs should be reduced as spares commonality with the C-130J ensures a readily available parts pool. The benefits for operators of both the C-130J and C-27J will be even greater, as common avionics and systems will reduce transition-training costs, and may allow for cross-crew qualification.
The C-27J programme was launched in September 1997. The first prototype, used for testing the Rolls-Royce AE2100D2 engines and Dowty R-391 six-blade propellers, flew in September 1999. The second aircraft flew in May 2000, incorporating the new avionics. The third and final development aircraft, representing the baseline model, flew in September 2000. The C-27J received civil certification in June 2001 and military qualification six months later.
With production ramping up for delivery of the first of 12 aircraft to the Greek air force later this year, Flight International was invited to fly the Spartan at Alenia's Turin production and test facility.
The Spartan's true strength is apparent on the ramp; it is not a small aircraft. While slightly shorter than its most direct new-build competitor, the EADS Casa C-295, the C-27J has a larger useable cargo volume. The cargo compartment is 2.45m (8ft) wide at its flat floor and 3.33m at it widest point. The large diameter allows a utility vehicle to be driven directly on and off without any modifications or disassembly. The size advantage also carries over to palletised cargo loads. Assuming standard 2.24m-wide pallets, the Spartan can carry 44.1m3 (1,560ft3) of cargo, compared with the C-295's 37.4m3, says LMATTS. These pallets are the same height (2m) as those carried by larger transport aircraft. Pallet compatibility allows cargo to be transferred directly to the Spartan, not broken down and repalletised as may be required for loading into a smaller aircraft. For air-dropped cargo, the C-27J can carry up to 6t of material on a single drop, 9t on multiple runs, while the C-295 is limited to 2t, says LMATTS. Jump cadence
The large cargo compartment also carries dividends when transporting troops. The C-27J can carry up to 68 troops in an optional high-density configuration, based on a 460mm (18in) seat width. For the paradrop mission, the aircraft can carry 46 paratroopers, seven more than the C-295 can reasonably carry, says LMATTS.
The C-27J's large cargo compartment has greater headroom, allowing heavily laden paratroopers to stand erect as they shuffle to the door. The dual exit doors on the C-27J are also larger than those on the C-295 and should allow for rapid exiting of the aircraft. Tactically, the higher the jump cadence the closer the paratroops will be when they hit the ground, thereby increasing combat effectiveness.
The Spartan was developed as a military aircraft and its 17,500kg (38,500lb) operating empty weight is markedly heavier than that of the civil-derived C-295's. The extra weight yields a robust aircraft with a three-spar wing. LMATTS says the Spartan's aluminum structure is more damage-tolerant than composites and easier to repair in the field. In addition, military cargo tends to be denser than civil freight, requiring high floor strength. The Spartan's cargo floor has a strength of 5,000kg/m (3,400lb/ft) (along the length of the compartment), superior to the C-295's 1,000kg/m and slightly better even than the C-130's, says LMATTS. In addition, the C-27J can carry any cargo further than the C-295: according to LMATTS the Spartan can carry 7,000kg a distance of 3,060km (1,650nm) at its basic and tactical MTOW, while the C-295 can carry the same load over 1,350km.
Pre-flight inspection of the Spartan, the developmental baseline aircraft, was conducted by Alenia test pilot Agostino Frediani. Externally, the aircraft closely resembles the G222 and C-27A, with the exception of the 4.11m-diameter six-blade composite, scimitar-shaped propellers, which are the same as those on the C-130J. The R-R engines put out 4,635shp (3,455kW) and are nearly identical to those on the updated Hercules. When viewed from behind, the propellers turn clockwise, making the critical engine the left one. As the rudder and vertical stabiliser are essentially unchanged from the C-27A, increased rudder power was required to keep minimum control speed at desired levels.
Seventeen vortex generators were added to the left-hand side of the vertical stabiliser just forward of the rudder. These energise the airflow over the rudder, increasing its effectiveness when deflected to counteract yawing moments generated by an engine failure.
Access to the aircraft is through the forward entry door with its integral steps. The flightdeck is quite spacious with 16 windows. Eight shoulder-height windows, four per side, provide an excellent field of view (FoV), while the four floor-level windows gave a direct view of the ground. Four ceiling-mounted windows enhance the overall FOV, while allowing for clearing of the flight path when manoeuvring at high angles of bank.
Like the C-130J, the C-27J's forward instrument panel is dominated by 180 x 205mm (6 x 8in) displays, of which the Spartan has five: two multifunction displays in front of each pilot and one centre-mounted. Each pilot has primary flight and navigation displays, with the centre screen displaying engine parameters and warning information. Dual autopilots are controlled via a glareshield-mounted panel. Aircraft system controls, mounted on the overhead panels, lend themselves to intuitive operation.Cool start
An external-power cart was connected to our aircraft and the dual global-positioning/inertial-navigation units aligned in less than 4min. The Hamilton Sundstrand auxiliary power unit (APU), mounted in the left landing-gear sponson, provided an air source for engine start. If the APU is inoperative an external air cart or even another Spartan can be used to start the engines. The engines were started one at a time, the full-authority digital engine control (FADEC
) metering fuel to ensure a cool start. Before-taxi check items were rapidly accomplished and consisted primarily of testing the propeller overspeed protection system. Frediani released the parking brake and used the nosewheel steering system's left sidewall-mounted tiller to navigate the taxiways to Turin Caselle's runway 36 for departure.
With an operating empty weight of 18,803kg and 3,606 kg of fuel, our take-off weight of 22,409kg was well below the maximum of 30,500 kg. Once aligned on the runway, Frediani gave me control of the aircraft for the take-off. I released the toe brakes and advanced the throttles to the take-off detent. The FADECs stabilised the engines at 4,700 shp. During the initial part of the take-off roll Frediani used the nosewheel steering to track centreline, while I applied right rudder to counteract the propeller P-factor. At 60 kt (110 km/h) indicated airspeed Frediani released the tiller, and rudder alone was used to track centreline.
At 91 kt, less than 15 kg of yoke force was required to establish the initial take-off attitude. With the flaps set to position "2" the Spartan leapt off the runway after a ground run of less than 280 m
. At maximum take-off weight and standard sea-level conditions, LMATTS quotes a ground run of 580m. Once airborne a pitch attitude approaching 20° was required to maintain the initial climb speed of 130kt. Gear and flap retraction caused little change in pitch forces as the pitch attitude was reduced to capture a climb speed of 170kt.Cargo drop
Hand-flying the aircraft during a climb to 8,000ft (2,440m) above mean sea level, I did a series of gentle manoeuvres to get a feel for the aircraft. Pitch and roll forces were well harmonised, with roll response fairly crisp for a transport-category aircraft. Once level, I engaged the autopilot and autothrottle. Rate of climb to level off had averaged roughly 3,000ft/min (15.2m/s).
Frediani had programmed the mission computer to simulate a cargo drop and the autopilot followed its guidance along the planned route. The simulated drop zone was an airfield around 90km (60 miles) south of Turin. Like the C-130J, the Spartan does not have a navigator; the GPS/INS and ground-mapping radar combine to allow the two pilots to accurately find the drop zone.
At 180kt the ramp was lowered in preparation for the drop. A slight reverberation was felt with the ramp down, but ambient flightdeck noise was not markedly louder than with it closed. The mission computer commanded a descent to a drop altitude of 1,500ft above ground level and appropriate speed reductions as the aircraft approached the initial point (IP) leading to the computed air-release point. Flaps were set to "3" and speed further slowed to 105kt before reaching the IP. Once past the IP I disengaged the autopilot and autothrottle to hand-fly the drop run. The mission computer provided the flight director (FD) with wind-corrected guidance to the air-release point for an aimpoint at the centre of the airfield. I found the lower sidewall windows useful for confirming that the computer-derived release point made sense in relation to the real world.
After completing the drop run the ramp was closed and flaps retracted. Once the aircraft was in a clean configuration I engaged the autopilot and autothrottle for a climb to 8,000ft. Once level at 8,000ft the autopilot precisely maintained 200kt indicated air speed. Total fuel flow was 966kg/h and the 22,160kg aircraft maintained 228kt true airspeed with a static air temperature of 14°C (57°F/ISA +15°C). For high-speed transit LMATTS projects a maximum true airspeed of 315kt for a 29,000kg gross-weight aircraft (95% MTOW) at 16,000ft on a standard day.
I next used the flight-level change mode of the autopilot to initiate a descent to 2,500ft (1,500ft AGL). While the autopilot and autothrottle did an excellent job of maintaining flightpath and airspeed, it did not trim the rudder. The conventional ball-type slip indicator on top of the outboard display, where the PFD is usually presented, allowed me to keep the aircraft in trim as varying power levels required corresponding trim changes. Once level at 2,500ft a total fuel flow of 1,110kg/h was required to hold 220kt (208kt indicated). Trimmed, with autopilot and autothrottle off, the aircraft was quite stable, allowing me to fly it hands off. The ride at low altitude, albeit on a calm day over level terrain, was quite smooth.
To avoid simulated small-arms fire along our route, I jammed the throttles to the maximum-continuous detent and started a rapid climb. The initial climb rate was in excess of 4,000ft/min as the airspeed was bled off to obtain an optimum value of 170kt indicated. Rate of climb from 10,000ft to 15,000ft was roughly 3,000ft/min. While one would do well to avoid hostile fire, the Spartan can be equipped with optional armour plating and an anti-deflagration inerting system for the fuel tanks.
Having climbed out of the small-arms threat envelope, we were now more vulnerable to missile threats. The Spartan can be equipped with radar and or laser warning receivers, as well as a missile approach warning system and chaff and flare dispensers. Additionally, a directional infrared countermeasures system and towed decoys are available.
Should these systems fail to defeat the missile, the Spartan is fairly manoeuvrable, with 3g attainable in a large portion of the flight envelope. Earlier, I found that at a gross weight of 22,000kg, slightly over 2.5g could be sustained at 200kt and 5,000ft. During manoeuvres at 5,000ft, pitch forces were fairly low. While load factor can be read on the PFD, the aircraft provided good tactile cues as to g loading. Pulling through 2.8g light airframe buffet signalled the approach of the 3g limit at tactical weight. At sea level and MTOW, LMATTS quotes a maximum sustained capability of 3.5g for the Spartan. The conventional boosted flight controls will allow the pilot to exceed the published limits and "bending it" may be preferable to missile impact.Simulated loss
Next, while still at 15,000ft, Frediani shut down the left (critical) engine to simulate its loss. Sensing an engine failure the FADEC automatically signalled the propeller control unit to feather the left propeller, a feature that could substantially reduce pilot workload during a critical phase of flight. At 140kt and maximum continuous power, the 21,500kg aircraft was able to maintain level flight in a 40°-banked turn. At this weight LMATTS quotes a one-engine-inoperative ceiling of roughly 24,000ft pressure altitude. Less than 35kg of rudder force was required for co-ordinated flight and around three-quarter deflection of the rudder trim zeroed out pedal forces. While I did not explore the Spartan's single-engine handling qualities at speeds lower than 140kt, the aircraft was quite responsive and had significant excess power at this intermediate gross weight and medium altitude.
Frediani used bleed air from the operating engine to restart the left engine. Once both engines were running the power was set to idle for a clean configuration power-off stall. In level flight the Spartan was decelerated at about 1kt/s. The stick shaker activated at 112kt. At shaker speed, control effectiveness in all three axes was good. Slowing just below shaker speed caused the onset of light airframe buffet. The aircraft was further slowed until the yoke was at the aft stop. The aircraft settled into a wings-level descent at 104kt. Recovery to normal flight was accomplished by releasing yoke back pressure and advancing the throttles.
The second and final stall was also in a clean configuration, but this time the throttles were set to a mid-range position of 2,600shp. This power-on stall demonstrated the effect of propeller-wash flow over the wing. The stick shaker in this condition did not activate until 101kt. As before, light airframe buffet was felt as the aircraft slowed below the shaker speed. With the yoke at the aft stop the aircraft was in a 20° nose-high, wings-level descent at 94kt. Recovery to normal flight was again accomplished by lowering the nose and advancing the throttles. The two clean-configuration stalls showed the Spartan to be docile at slow speeds, while illustrating the effect power setting can have on the stalling speed.
On our return to Turin Caselle, Frediani demonstrated the Spartan's steep descent mode. This is armed by push buttons on the throttles and allows the FADEC to schedule reduced idle torque: by varying the propeller pitch, a slightly negative thrust can be commanded for a rapid descent. Pulling both throttles to idle engaged the steep descent mode, with the word "STEEP" displayed below the power display for each engine.
At 130kt the aircraft stabilised in a 10° nose-down flight path from 15,000ft. Initially the rate of descent was around 2,500ft/min, increasing to 3,000ft/min by 4,000ft as the FADEC allowed more negative thrust. The steep descent mode may help the Spartan get into hot landing zones by allowing it to stay above the threat posed by small-arms fire until close to the field.Ergonomic error
Once level at 4,000 ft en route to Turin Caselle, I used the Northrop Grumman APN-241 colour radar to paint the airfield. At 75 km from the field, the runway and surrounding roads were clearly displayed in shades of green. Returns from targets such as buildings were presented in colour. The radar cursor could be moved via a control handle on the centre console.
While the cursor itself was easy to move and control, I felt the handle was located too far aft on the console for comfortable use while at the co-pilot's position. In addition to an excellent ground mapping capability, the radar also has a beacon mode. Pathfinder personnel place a transponder at the drop zone. The beacon's distinctive code gives an easily identifiable return on the radar display, making drop zone location an easy task.
In preparation for an instrument landing system approach, Frediani removed the radar display from the right inboard screen and replaced it with a map display. This showed approaching waypoints as well as TCAS traffic in the terminal area. The flight director's guidance allowed me to easily capture and track both the localiser and glideslope. With the flaps set to "2" for a touch-and-go manoeuvre, I slowed the aircraft to 120kt on short final.
As could be expected, the digitally controlled engines and propellers allowed target airspeed to be precisely maintained. At 10ft above the runway I retarded both throttles to idle and raised the nose several degrees for the flare manoeuvre. The Spartan settled on to the runway less than 30m beyond my aimpoint. After lowering the nosewheel to the runway I advanced the throttles to the take-off detent. At 120kt I rotated the aircraft and established a climbing left-hand turn to downwind.
The last approach and full-stop landing was again to runway 36, but with the flaps set to "4", their most extended position. A 5° visual glidepath was intercepted and an airspeed of 105kt maintained. Rate of descent on this steep approach was 1,000ft/min. At 20ft above the runway I retarded the throttles to idle, and raised the nose slightly. The aircraft touched down in a 500ft/min sink on the aimpoint, just beyond the threshold.
The four trailing-arm main landing gear readily absorbed the impact and the spoilers automatically deployed to dump lift. I moved the throttles to the maximum reverse position, allowing the large propellers to slow the 21,185kg aircraft. Frediani applied maximum toe brakes and the aircraft was stopped after a ground run of less than 300m. Total landing distance would have been roughly 500m. Frediani took control of the aircraft for the taxi back to Alenia's test ramp. After a 2min cool-down period, both engines were shut down and we deplaned.
The C-27J is a complete tactical airlifter. Derived from the G222/C-27A, its upgraded avionics and propulsion system are shared with Lockheed Martin's C-130J and significantly enhance its capabilities. The large cargo compartment allows for drive on and off of utility vehicles and the direct transfer of standard-size pallets from large transport aircraft. Combat survivability
The upgraded avionics allow two pilots to successfully conduct air-drop operations, a task that used to require three flightdeck crewmembers. Rugged construction, redundant systems, self-protection systems and a high power to weight ratio combine to enhance combat survivability.
The baseline Spartan flown by Flight International can be further enhanced with the addition of a head-up display and in-flight refuelling capability. With 24 firm orders from the Greek and Italian air forces, the C-27J Spartan is on its way to defining the new standard for medium tactical airlifters.