Fourth-generation fighters are now a reality, providing new levels of energy and agility as well as sensor and weapon networking, but posing the problem of how to train pilots to make safe and effective use of the carefree handling and mission capability of these costly combat assets.
A cheaper alternative to using the fighter itself could be a "fourth-generation trainer", and associated integrated training system, that could take a student pilot from basic to advanced training, then through the tactical weapons and operational conversion units (OCU), and on to the frontline alongside the fighter.
|"I admire Alenia Aermacchi's decision to put cockpit customisation at the heart of the M-346's digital architecture"|
Alenia Aermacchi has designed the M-346 for this role, and the aircraft is the only all-new European advanced/lead-in fighter trainer in development. Its main rivals are the Korea Aerospace Industries (KAI) T-50 Golden Eagle, and the BAE Systems Hawk 128.
Although still in development, w ith Italian military certification not due until mid-2007, Flight International was invited to assess the M-346's potential to span the "basic to OCU" gap and be a one-stop solution to the training, capability and budgetary problems faced by air forces fielding fourth-generation fighters.
Alenia Aermacchi is the result of the merging of Alenia and Aermacchi in July 2003, and is part of Italian aerospace and defence giant Finmeccanica. Based at Venegono in Varese, near Milan, the company has delivered more than 2,000 trainers to date. Its products include the SF-260 piston primary, M-311 turbofan basic, and MB-339CD turbojet advanced trainers.
The M-346 has its origins in European studies of a new advanced trainer in the late 1980s, in which Aermacchi participated. These led to the AT-2000 proposal for an aircraft with an empty weight around 6.2t and a single afterburning engine. Aermacchi believed the better option was a lighter aircraft, around 4.5t, with two non-afterburning engines and advanced aerodynamics to give high agility, but docile low-speed handling. In 1992, the company left the European study to pursue its own design based around two engines.
|Inlet location improves efficiency|
At the end of 1992, Aermacchi joined with the Yakovlev design bueau, which was struggling with development of the Yak-130 jet trainer for the Russian air force to replace the Aero Vodochody L-39 trainer. Aermacchi suggested the requirement be changed from basic to advanced lead-in fighter trainer and it took the basic Yak-130 shape and developed it. According to Emanuele Merlo, head of flight technology, the M-346 is a totally new aircraft, internally and externally.
The wing was moved up the fuselage, having been too low on the Yak-130 and causing horizontal stabiliser blanking at mid to high angle of attack (AoA). The leading-edge extensions (LEX) were reduced and redesigned to give controllable vortex lift. Two small vertical fins were added at the wing roots to "trap" and control the LEX vortices at AoAs from 25-30° upwards. These LEX vortex controllers ensure the "vortex burst" over the wing at high AoA is symmetrical and controllable.
The wing was remodelled to blend into the fuselage for improved span loading. A saw- tooth was added to the full-span leading-edge flaps. Thickness was optimised from root to tip, and planform, profile and camber were optimised for best lift/drag over the widest possible envelope from short field and subsonic manoeuvre, through transonic penetration to supersonic cruise.
The single fin was repositioned for high AoA and the engine nozzle positions changed to reduce zero-lift drag. The air intakes were completely redesigned and are now 98-99% efficient over virtually the entire operating envelope, says Alenia Aermacchi. The shielded intake position under the LEX also improves engine efficiency at high AoA and when supersonic. The engines were changed to Honeywell F124-200s, each producing 6,250lb thrust (28kN) and with full-authority digital engine control (FADEC). The inlets are sized to accommodate up to a 20% increase in thrust from the present engine or possible future versions.
The sharp "chine" nose of the Yak-130 was rounded and redesigned to reduce frontal area, prevent unwanted vortex development in sideslip and allow installation of radar. A top-mounted airbrake was placed on the fuselage spine; horizontal-tail control power was raised to improve short-field performance and post-stall manoeuvring pitch recovery; and a fixed (removable) in-flight refuelling probe was added on the right side of the nose. There are now nine hardpoints (three wet), including wingtip missile rails.
A digital fly-by-wire flight control system (FCS) operates the ailerons (there are no spoilers), rudder, taileron and leading-edge flaps. Simple half-span flaps are pilot operated. The quadruplex FCS can lose two channels and still provide safe operational capability. Rear-cockpit instructor controls provide the ability to "degrade" the FCS into various "training" modes. Although configured with a centre stick, the cockpit has been designed to accept a sidestick if requested by the customer.
The first M-346 prototype flew in July 2004 and the second in May 2005. Initial operational clearance of the FCS is due at the end of this year, with full clearance and Italian military certification due in mid-2007. Production rate is envisaged at three a month with an initial run of 12 aircraft plus one static and one fatigue test airframe planned for 2007, after certification.
The prototype has been demonstrated to the Greek air force, which has a critical need to replace its ageing T-2 Buckeyes, and Alenia Aermacchi has a memorandum of understanding with Hellenic Aerospace Industry for Greek participation in development and production of the M-346. Other potential customers include Chile, Poland, Portugual, Singapore and the United Arab Emirates. There is also the Advanced European Joint Pilot Training (AEJPT), or Eurotrainer, requirement involving 11 countries.
As part of its AEJPT studies, Alenia Aermacchi modelled the training mission density and superimposed it on the M-346's flight envelope. The four "hot spots" - low speed/low altitude (circuits and approaches), 420kt (775km/h)/500ft (150m) (low-level attack), M0.7-0.8/20,000ft (air combat manoeuvring) and M0.7-0.9/38,000ft (air interception) - fall within the M-346 operating envelope. In the air combat training mission, the M-346 at full dry power would use 50kg/min (110lb/min) of fuel and could remain in the training area for 18min - three times the endurance of the afterburning T-50, the company claims.
Embedded training simulation (ETS), a system already operational on Italian air force MB-339C/Ds, allows the M-346 pilot to train within a virtual scenario involving computer-generated forces displayed in the cockpit. ETS allows early introduction and enhanced proficiency with situational awareness, tactical operations, sensor management and weapon deployment. The ETS system can simulate offensive sensors such as radar, defensive aids such as radar warning, datalinked information and a wide variety of air-to-air and air-to-ground weapons. The full integrated training system includes ground classroom trainers, procedural tactics trainers and full mission simulators that can be linked together and to the aircraft.
Basic empty weight is about 4,600kg and, with two pilots an a full internal fuel load of 2,000kg, the M-346 weighs around 6,700kg clean at take-off. Given a combined thrust of the two F124 turbofans of 12,500lb, the aircraft has greater than 1:1 thrust-to-weight ratio from around half fuel when clean. This is important when comparing the M-346 with trainers with a single afterburning engine that can exceed 1:1 only in reheat and at the cost of fuel and training time. Maximum take-off weight fully loaded is 9,700kg. This is also the maximum landing weight.
Three 465kg-capacity external fuel tanks can be carried (limit M0.92), which gives the M-346 a range (with 10% reserves) of 2,850km (1,540nm) compared with 2,070km clean. The aircraft's service ceiling is 45,000ft, time to 40,000ft is 3.5min at an initial climb rate of 21,000ft/min (107m/s). Maximum speed is M1.2 at altitude or 572kt equivalent (590kt true) at 5,000ft. Load factors are +8/-3g. Take-off run is around 400m and landing roll around 500m.
The FCS endows carefree handling throughout the flight envelope. The aircraft is spin resistant and can be held inverted for 30s. With about 500kg of internal fuel, final approach speed is around 100kt indicated.
The F124-200 turbofan has a dual- redundant FADEC. The throttles feature a spring detent at 90% NH (core speed) to represent full dry power, giving a time for take-off roll of around 20s, typical of current trainers. Full throttle travel gives 100% NH, representing afterburner and giving a roll of 11s, typical of current fighters. The engines are surge resistant with auto-relight, which can be achieved up to 30,000ft and M1.
Maximum sustained load factor at 15,000ft and M0.6-0.8 is +6g and turn rate 14.5°/s - performance that exceeds many fighters and all trainers in either dry power or reheat. Only above M0.8 at this altitude does the KAI T-50 in reheat start to better the turn rate of the M-346. Maximum angle of attack is 40°, which matches or exceeds the limits of most modern fighters and allows the M-346 to undertake post-stall manoeuvres. Maximum roll rate is 230°/s and can be sustained up to 6g.
An auxiliary power unit (APU) is fitted that can be used for air supply, engine starting and 28V DC power supply up to 25,000ft. The hydraulic system has one pump per engine, with dual 3,000lb/in2 supply to the primary and secondary flight controls and wheel brakes. Park brake, steering, speed brake and landing gear are driven from the right-hand system, allowing the left engine to be shut down during taxi back after landing. An emergency power system is linked to the left hand supply.
The electrical system has one 20kVA 115V AC generator per engine and left and right transformer rectifier units to give 28V DC power. There are also separate AC and DC external ground-power receptacles on the left-hand side of the nose close to the pressure refuelling panel.
Main wheel brakes and nosewheel steering are "control-by-wire", with steering selectable from high (taxi) to low (take-off and landing). The main gear folds forward into the fuselage, but wheelbase is a generous 2.7m. Gear limiting speed is 250kt. Carbon brakes allied to the low approach speed negate the need for any reversers, brake chute or lift dump.
The canopy is hinged on the right, electrically operated and features a bird-proof blast-shield transparency between the cockpits. The canopy can be jettisoned manually from inside or outside the aircraft using an explosive severance system, so there is no transparency-shattering miniature detonating cord obscuring the view. In an ejection, striker arms on top of each seat shatter the canopy. The seats are auto-sequenced, auto-separated and a command eject function is available to the instructor in the rear cockpit.
The heart of the avionics are two main computers, linked by 1553B databuses, one for navigation, weapons, head-up (HUD) and multifunction displays (MFD) and one for comms/audio. Both cockpits have three 5 x 5in (125 x 125mm) MFDs, an upfront control panel for comm/nav/ident and data insertion and the wide-angle HUD. The cockpit is night-vision compatible and provisioned for a helmet-mounted display (HMD). The HUD will be able to display infrared imagery from a pod-mounted sensor. Alenia Aermacchi says it will be able to customise the HUD and MFD formats and stick and throttle controls to closely match any fourth-generation fighter.
Alenia Aermacchi is convinced a two-engined trainer offers higher levels of safety. Its figures show one loss per million flight hours, rising to 10 for a single-engine aircraft. The company has designed the M-346 for low life-cycle costs, high reliability and low maintenance.
|The nose can house multi-mode radar|
There is extensive built-in test and an on-board maintenance/fatigue data recorder. The aircraft is maintained by "on condition" for essentially all of its service life. After 100h, an 8h two-man inspection is carried out and after 500h a preventative inspection is conducted by a bigger team. The engine hot section is inspected, on-airframe, every 2,000h and the cold section every 4,000h. There is no engine time between overhauls. The direct ratio is 3.5 maintenance manhours/flight hour. Recently the prototype flew direct from Venegono to Greece and flew nine demonstration flights over two days without fault.
Our short test flight took place from the company airfield at Venegono in mid-June using the second prototype, aircraft 002 registered X616, with roughly 100h on the airframe. The M-346 was still in the middle of its development and certification programme and had not been cleared over its full envelope.
The principal limitations on 002 were a maximum altitude of 40,000ft (45,000ft for the production aircraft), speed at altitude of Mach 0.85 (M1.2 production), speed at low level of 530kt indicated (572kt production), gear limiting speed 200kt (250kt production), maximum +20° AoA in all configurations (+40° production), load factor +7/-1.6g (+8/-3g production).
The fly-by-wire FCS had been cleared to software Phase 1 (direct link) and was undergoing Phase 2 (reversionary mode) testing at the time of my flight, which would be conducted in Phase 1 standard. Phase 3 (full carefree handling) had been tested in the full mission simulator, which I flew briefly later as a comparison, but had yet to be loaded and tested in the prototypes in the air.
My safety pilot was Olinto Cecconello, experimental chief test pilot and M-346 project test pilot. He also flies the Eurofighter Typhoon as a test pilot and is able to bring fourth-generation fighter "read across" to the M-346 design.
Because of air traffic control and aircraft limitations we elected to look at handling and performance in the air combat manoeuvring training role and finish with some high-speed low-level transit and visual work. We could not go supersonic and did not have the time for a weapons or ETS evaluation.
Cecconello would take the front cockpit, and I the rear in the role of an instructor, drawing on my 1,200-plus hours on Hawks, many in the back seat as an instructor. I was planned to fly the complete sortie, but had no time for simulator familiarisation before stepping into the rear cockpit. The ease with which I could fly the aircraft would be a mark of how good its design was.
Because Venegono's runway 36 is short, just 1,420m, we elected to go with clean wing and 1,500kg internal fuel. Aircraft 002 carries 500kg of flight-test instrumentation and the landing gear, taken directly from an Aermacchi AMX, is nearly 100kg heavier than in the production aircraft. With crew, take-off weight was 7,700kg. Outside air temperature was +28°C (82°F), wind calm, QNH 1018mb and visibility 8km with haze, clear sky and no turbulence. The operating area was to the north east, above the mountains surrounding Lake Como and so our base level was 10,000-15,000ft.
Boarding was via a ground ladder, but production aircraft will have a drop-down ladder "post" for crew entry. Stepping in was simple with the enormous canopy side-hinged to the right. The Martin-Baker Mk16 ejection seat was comfortable, with electric adjustment and a five-piece harness, which I like for negative g. I immediately liked the fact that all cockpit switches are forward of the pilot's body line so there would be no need to bury my head or operate switches "blind" - something I had not seen since the Folland Gnat.
The three large head-down MFDs were bright, with clear formats and sharply defined symbology and with bezel buttons for sub-menu selection. The layout closely resembles that of the Eurofighter and Rafale. The centre stick, again similar to the Eurofighter's, is positioned so as not to obscure the centre MFD. Mounted on the left sidewall, the throttles are "twinned" to look like a single unit and move along rails rather than a quadrant - a nice design that frees up console space.
APU start assist was simple. I liked that the engine-start rotary selection knobs are press in to turn/select and not pull out, preventing damage to the switch. Post-start we had to wait about 12s for the OBOGS to start operating. The canopy was then closed electrically, but in a two-action sequence. The first activates a horn and brings the canopy over and down to about 25cm (10in) above the side rail. The second action fully closes the canopy after a delay of about 3s to ensure no fingers are trapped - another excellent design detail.
Field of view in the rear cockpit is outstanding (and even better in the front). The canopy is so large and clear that it gives the slightly weird impression of not being there at all. The rear seat is so high that you almost lose sight of the front seat and, with no detonation cord to disrupt the forward view, it gave the impression of being in a single-seat cockpit.
|The canopy is so large and clear that it gives the slightly weird impression of not being there at all. The rear seat is so high that you almost lose sight of the front seat|
We were ready to taxi 2-3min after start. Power to move was small and throttles close to idle at taxi speed. Taxiing was accurate, and tight turns easy to achieve with nosewheel steering (NWS) set to low and the carbon brakes were progressive and effective. I did not like the small NWS engage button at the base of the stick's forward face, or having to cycle between low and high settings on the cockpit coaming. I recommend a chunkier switch or paddle so that students can find it in a hurry and, as it is steer-by-wire, incorporating the low/high modes into a digital schedule and leaving it fully engaged.
Line-up checks consisted of setting the trailing-edge flaps to take-off (20°), which automatically scheduled the leading-edge flaps to 20°, checking both engines momentarily at 80% NH then setting 100% and releasing brakes (aircraft 002 was not yet fitted with the production "pseudo reheat" throttle detent at the 90% NH position). Acceleration was rapid and telemetry showed a 400m ground roll, 11s take-off run and lift off at 8° AoA and 130kt (I was a little late to pull at the target rotate speed of 115kt).
|M-346 is designed to handle and manoeuvre like a modern fighter|
The HUD can show various flightpath vector (FPV) symbols, but we selected climb/dive angle (CDA - a velocity vector in pitch, but locked laterally). To aid accurate pitch capture, the HUD take-off symbology features additional pitch target bars that were useful at rotation until the CDA stabilised. Gear and flap were selected up immediately to observe the 200kt indicated limit speed, and the aircraft throttled back just seconds later to observe an ATC speed limit of 300kt. I felt no pitch changes with gear or flap travel.
After the gear came up, the HUD automatically changed to navigation mode. In the ATC positioning turns that followed, the controls already felt powerful, light, harmonised and fighter-like. They reminded me of the Dassault Mirage 2000, which has the nicest fly-by-wire FCS of any fighter I have flown to date.
After stabilising at 3,000ft, we were re-cleared to climb to 29,000ft. Full power and 300kt best climb speed gave a climb angle exceeding 25° and a climb rate that was off any clock I could see. The cockpit environment remained quiet and smooth. The FCS with its Phase 1 software load still felt extremely good. The control mechanical characteristics were just about perfect, with low breakout forces, just 0.25kg, in all axes. Roll rate was well over 200°/s and the roll could be stopped precisely at the 90° point.
The FCS uses a flightpath hold control law, so the pilot can place the FPV at any pitch angle, release the controls and the aircraft will maintain that flightpath angle during speed change. I tried this inverted, with the FPV on the horizon line, and released the controls. It was impressive to see the aircraft maintain -1g precisely with no stick input.
Longitudinally, the aircraft has auto-trim with gear up and above 190kt, so throughout the climb and accelerating to M0.85 at 29,000ft, the stick never moved and there was no a need to trim in any axis - a fighter-type feature. I could detect no pitch changes with power. I could not exceed M0.85, so cannot comment on transonic/supersonic performance and handling.
I descended rapidly to 20,000ft for some hard combat-type manoeuvring. I liked the airbrake, which can be selected to any angle up to 60°, with the position shown on the combined airbrake/flaps/gear display panel just above the gear handle.
In the 15,000-20,000ft height band, at 300kt and with 1,200kg of internal fuel, the lift boundary was buffet limited around +4g. Cecconello says the automatic scheduling of the leading-edge flaps still has to be perfected in FCS Phase 3, which should allow more g to be generated. I would recommend investigating scheduling the flaps automatically with increasing AoA versus airspeed, as in the KAI T-50, but this may require strengthening of the flaps.
Rapid roll reversals, highly loaded rapid rolls, low-speed loops and a high g wing-over all showed the aircraft to have no vices or control law discontinuities. Field of view was superb all the way around to the fin.
The aircraft was stabilised gear and flaps up at 20° AoA, the Phase 1 FCS limit, equating to 109kt. Later, flying the simulator with Phase 3 FCS indicated that at zero airspeed, with full aileron deflection held against full opposite rudder, the M-346 was completely spin-resistant.
Laterally and directionally, the aircraft could be rolled with rudder in the direction of the applied rudder pedal, and over 12° of sideslip could be generated to "kick off drift" for a crosswind landing in up to the demonstrated 30kt limit. The FCS damped any Dutch roll. Overall, I thought the FCS even at Phase 1 was excellent, and at Phase 3 it should be superb.
We then dived to 1,500ft for a high-speed, low-level transit home at 500kt-plus following the HUD navigation symbology. The low-level ride felt steady and comfortable and the aircraft/engine combination feels strong in this flight regime. There is a lot of excess thrust at low level, so I have no doubt the 572kt equivalent airspeed will be achievable when cleared.
We broke into the circuit at +5g, from 360kt indicated, slowing with full airbrake. With the gear down, below 190kt, the aircraft requires manual trim, but this is an enhancing feature to give students the necessary feedback from on the stick on speed change if they lose attention to the HUD. Downwind, I checked the gear down and the leading- and trailing-edge flaps were at 20°. The turn on to finals was flown at around 150kt until the AoA "bracket" came into view (the HUD having automatically reverted to landing mode), then 12º AoA held before slowing to 14º AoA (128kt) for the roll.
Soaking it up
From the instructor position I found the forward canopy arch blocked the view of the touchdown point, but Cecconello says the arch will be half the size in the production aircraft. The FPV was placed over the intended landing point, small bursts of power holding the AoA, and the trailing-link gear soaked up the touchdown with no hint of bounce.
Two rollers were completed then, due to a problem with his microphone, Cecconello decided on a full-stop landing. This was with full landing flap (leading-edge 25°/trailing-edge 40°), with telemetry showing a touchdown at 115kt and 13º AoA and stopping within 600m without the use of heavy braking. Flying and demonstrating an accurate circuit and touchdown to a student would be simple. The aircraft was as easy to fly as any jet I have flown and could be coped with by a basic student. We shut down with 600kg of fuel, having used 900kg over a flight time of 45min.
A teaching effectiveness graph developed by Alenia Aermacchi - with the Eurofighter and Rafale referenced at 112% - puts the M-346 at 92%, 10% ahead of the T-50. The company claims the M-346 could save an air force around €2 million ($2.5 million) per student pilot, as its training effectiveness equates to reduced OCU flying hours. Alenia Aermacchi argues these savings make the M-346 a cheaper solution than current Hawk 115-type advanced trainers.
My overriding impression after flying the M-346 is of an aircraft with great handling and performance, a true fourth-generation trainer in design and part of an integrated training system. I believe the M-346 has the potential to offer "one-type" training from basic through to fighter lead-in, and I admire Alenia Aermacchi's decision to put cockpit and display customisation at the heart of the M-346's digital architecture. ■
Source: Flight International