FLIGHT TEST: Alenia Aermacchi M-311 - Bridging the gap

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Alenia Aermacchi believes the M-311 can play its part in a package that can support basic, advanced and tactical flight training for the latest military fast jets

Military fast-jet pilot training may be on the cusp of a change. Air forces are addressing the difference in capability between new-generation fighters such as the Dassault Rafale and Eurofighter Typhoon and the aircraft currently used for basic, advanced and tactical flight training leading up to operational conversion.

Alenia Aermacchi, part of Italy's Finmeccanica group, believes it can deliver a complete new-generation pilot training package to support the latest fighters. This package includes the new M-346 lead-in fighter trainer, evaluated by Flight International in July 2006, and the M-311, a smaller jet-powered trainer the company believes can cover present basic and advanced phases and much of the tactical training.

Flight International set out to evaluate whether, in terms of handling, performance and systems, the M-311 could cover such a wide training envelope to assess how well it would complement a lead-in fighter trainer like the M-346 and to judge whether it could offer training advantages as a jet while retaining a fuel burn comparable with a turboprop.

 
© Alenia Aermacchi   
The M-311 is intended to provide jet handling and performance with turboprop economy

The M-311 is an upgrade of the Stelio Frati-designed, SIAI Marchetti-built S-211, which first flew in April 1981 and entered service with the air forces of Singapore and the Philippines. Aermacchi acquired the S-211 design when it took over SIAI Marchetti in 1997, and in 2004 announced plans for an improved version.

Compared with the original S-211, the M-311 features a more powerful Pratt & Whitney Canada JT15D-5C turbofan developing 3,200lb (14.2kN) sea-level thrust on a standard day. The engine has electronic fuel control and a 4,500h time between overhauls. Aerodynamics are improved and the flight envelope expanded in the production aircraft to a maximum speed (VMO) of 430kt (795km/h) and Mach number (MMO) of 0.8, a ceiling of 40,000ft (12,200m) and a g range of +7.0 to -3.5.

The landing gear has more muscle for a 4m/s (13ft/s) sink rate and the airframe strengthened, with increased use of composite materials for secondary structures and panels. Fatigue life is 15,000h. There are two hardpoints per wing - one wet, one dry and all capable of carrying practice weapons - and one fuselage hardpoint for a gun or a baggage pod.

The avionics suite is completely revised, with three identical 5 x 7in (125 x 180mm) colour liquid-crystal multifunction displays in each cockpit, wide-angle head-up display in the front, full-size HUD repeater (using a fourth dedicated MFD) in the rear and hands-on-throttle-and-stick controls in both. Cockpit internal dimensions have been increased to be almost identical to those of the BAE Systems Hawk, and displays and lighting are compatible with night-vision goggles.

Avionics suite

Supplied by CMC Electronics, the integrated avionics suite includes dual mission computers, embedded GPS/inertial navigation, video/audio/data recorders and optional digital moving map and stores management system. An embedded simulation capability is available as an option, identical to that offered on the M-346 and able to display virtual radar targets and radar warning receiver threats.

Internal fuel capacity is 715kg (1,580lb), with the option to carry a further 415kg in two external tanks on the inboard wing stations. The ejection seats are zero-zero Martin Baker 10LKs with command ejection. An on-board oxygen-generating system eliminates the need for bottles. The environmental control system cools the cockpit for ground operations in temperatures up to ISA +35ºC (95ºF).

    
Excellent field of view over the short nose is one jet advantage

Conventional ailerons are hydraulically boosted with manual reversion. The elevator and rudder are connected mechanically by pushrods, with three-axis electrical trimming. Secondary flight controls are simple trailing-edge flaps (electrically actuated) and a belly-mounted airbrake (electrically controlled and hydraulically actuated).

The electrical system is DC with internal-battery engine start. The 207bar (3,000lb/in2) hydraulic system primarily operates the gear, wheelbrakes, airbrake and aileron boost. Maintenance is "on-condition", using a health and usage monitoring system, with only first- and second-line maintenance planned throughout the service life and requiring only semi-skilled personnel. All avionics boxes have been centralised in the nose and are accessed via large quick-release doors.

The flight, with M-311 project test pilot Quirino Bucci, took place from Venegono in northern Italy, with the test area to the north-east above the Italian Alps, with a low-level return from Lake Como. The aircraft - registered I-PATS, but since changed to CMX-619 for Italian military certification - was originally built as the prototype for the upgraded, JT15D-5C-powered S-211A, and has been reconfigured as the M-311 prototype and technology demonstrator. All-up weight was 3,100kg.

I took the front seat and flew the complete sortie. Entry was via a groundcrew-attached ladder, but there are integral fuselage steps if required. The manually operated and sideways opening canopy made stepping in easy. The seats are electrically adjustable and comfortable, and strapping in was simple. Aermacchi's design goal is to accommodate male pilot percentiles from 3% to 99%.

The cockpit immediately reminded me of the Hawk in terms of dimensions and field of view, and I was struck by the improvement in view directly forward and down over the nose compared with the Shorts Tucano turboprop trainer. All side-console controls are forward of the pilot's "3-9" body line, which is impressive. Some of the switch positions in the prototype are not ideal, but will be changed in the production aircraft, Bucci says. HOTAS controls and HUD symbology were modelled on the Lockheed Martin F-16 in this cockpit, but as in the M-346 can be customised to represent any new-generation fighter.

Start procedure

After canopy closure, start was by a simple switch selection with the throttle placed through the gate at 10% NH (high-pressure spool speed, which then became the controlling engine parameter). With the engine stable, avionics were brought on line and the aircraft was ready to taxi about 45s after initial start selection.

A brisk taxi pace could be maintained with the throttle just out of idle. Nosewheel steering is permanently connected to the rudder pedals and, although centreline tracking was accurate and pedal input responsive at taxi speed, turning tightly was not that good. Aermacchi aims to cure this with a pilot-selectable high/low ratio setting and by improving the effectiveness of the rudder-pedal-operated wheelbrakes.

Take-off with mid-flap was from full power against the brakes and took 17s and about 550m (1,100ft) to the rotate point at 100kt. Rotation was achieved easily and accurately with small rearwards stick force and displacement to capture the 12º-pitch initial climb attitude. The HUD as used throughout the sortie and in all flight modes. Symbology was clear and easy to use, with a variety of modes available.

Gear was raised, followed immediately by flaps, at 130kt and no trim changes were felt. Acceleration towards a climb speed of 220kt was rapid and smooth and an initial altitude level-off of 3,000ft was captured precisely using the HUD flightpath vector and tape presentation of altitude and speed.

Roll control immediately felt strong and precise, and later tests would show a fighter-like sustained roll rate of 160-170/s. All controls were well harmonised, with a classic force ratio of 1/2/5 for aileron/elevator/rudder. The control feel was so good, with such small breakout force, little freeplay and positive centring that it was hard to remember the aircraft did not have hydraulically actuated controls in all three axes. Handling this good would immediately give any fast-jet student confidence in manoeuvring the aircraft in the circuit, in close formation or in combat training.

A climb to 15,000ft was flown at 220kt/M0.42, giving a climb rate of around 4,000ft/min. The cockpit environment was delightful at all power settings: smooth, quiet, well-ventilated and cool. At 15,000ft some stability checks were made around 150kt indicated airspeed. "Slam" power increases/decreases from idle to full power and back showed no pitch up/down and gave no changes in directional trim. Full power from idle could be achieved in less than 4s. Throttle handling throughout the flight was "carefree".

Airbrake deployment

Moving the flaps from "up" to "take-off" (6s) and from "take-off" to "land" (3s) resulted in a lowering of nose attitude, but the pitch rate caused was small and without any "ballooning". Raising or lowering the gear took 6s. Airbrake deployment was fully variable and well indicated on the cockpit display - extension created a small but unmistakable level of airframe buffet, but with no attendant pitch change.

Speed changes of up to about 30kt away from trim speed were acceptable in that the out-of-trim forces could be held with the control stick and would give the student a clear indication of speed deviation. The "Chinaman's hat" trim switch for elevator and aileron was accurate and rapid in operation. Any out-of-trim forces could be negated so quickly that the student would find the pitch control characteristics to be "fighter-like" with respect to speed change, appearing essentially neutral during combat manoeuvring. Short-period pitch response was less than 0.5s and damping was high so that the M-311 displayed an accurate fighter-like response that would allow accurate target tracking.

A wind-up turn at full power at 250kt (achieving a maximum of 5g) and 350kt (a maximum of 6g) showed the stick force per g gradient was linear, but the final force to hold the maximum g was quite high as the aircraft has a mechanically linked elevator rather than a fighter's hydraulically actuated "all-flying" tailplane. Maximum sustained g was limited by wing buffet, but the onset was progressive and there was no hint of wing rock or uncontrollable wing drop. Aermacchi data shows a "corner speed" (best turn rate versus best radius) of 280kt.

A quick lateral and directional stability check showed the aircraft could generate 12º of sideslip against 18º of opposite roll, and so easily cope with the quoted crosswind limit of 25kt during a landing from a crabbed approach. The aircraft displayed little adverse yaw with aileron, but an improved slip indication would ensure the student is properly directionally trimmed.

    
Peter Collins judged the aircraft to be a 'delight to fly'

Stalling and spinning were next. The aircraft features a stall approach warning aural "warble" followed shortly thereafter by a digital voice stating "STALL, STALL". In a clean stall the aural warnings triggered at 110kt, but were followed almost immediately by an unmistakable buffet felt through the stick that continued to the stall at 99kt. Stall was indicated by a distinct nose drop and the established stall by pitch nodding, buffet, back stick and about 4,000ft/min rate of descent. The wings could be held level at all times.

A stall with landing flap and gear down displayed the same behaviour, with warning at 95kt and stall at 82kt. Recovery was comfortably achieved by relaxing back stick and applying full power. The engine spooled up so quickly (3.5s from idle) that it felt akin to the power delivery of a propeller, but with none of the associated directional trim changes.

Two spins were conducted, both to the left to ensure the observed spin behaviour was consistent and both entered from 100kt at 18,000ft. The first turn took about 6s and both spins showed the aircraft hesitating in yaw for 2-3s at the entry to the second turn then re-establishing the yaw rate and pitch attitude. Recovery was instantaneous on centralising the controls at the end of the second turn. Recovery level-off was 14,000ft.

Some aerobatics and combat manoeuvring finished off the upper air assessment. The aircraft was a delight to fly aggressively and precisely, but the aural stall warning was distracting when pulling hard at low speed over a loop or a wingover. Given such good pre-stall buffet indication from the wing itself, the aural warning may be unnecessary. I had to continually remind myself I was not flying a BAE Hawk as the overall feel of the controls, turn performance, excess power, cockpit view and dimensions of the M-311 are so similar. A dive to low level at M0.75 showed the aircraft to be trouble-free approaching MMO.

A series of simulated air-to ground gun and bomb attacks were then made to an inertial navigation-designated point on the shore of Lake Como. Not only could different bomb types be selected (retarded or free-fall), but a cockpit MFD could display the simulated bomb score and plot it on a bulls-eye presentation on the screen. The HUD weapon symbology was again clear, well-defined and easy to use. Manoeuvre airspeed, tip-in heights and dive angles were achieved without fuss within the available engine power. The VMO of 430kt calibrated airspeed allowed realistic dive attack speeds.

Low-level navigation

A low-level route was then flown to return to Venegono at 500-1,000ft above ground level and speeds from 240-360kt indicated. The aircraft could achieve a level speed of 360kt at full power with no sign of strain. The low-level ride/gust response was smooth and stable. Forward visibility for low-level navigation was greatly improved over that in the Tucano, by comparison. I liked the digital moving map with terrain awareness or restricted airspace overlay especially given the poor into-sun visibility while flying in mountainous terrain. HUD navigation was easy to follow.

At 360kt cruise fuel flow was 12.5kg/min 300kt gave 8.5kg/min and 240kt gave 6kg/min. Starting with an internal fuel load of 715kg and returning to the circuit with 150kg would allow the aircraft at least 60min of low-level navigation at 300kt with several accelerations to 360kt for low-level attack or air-combat manoeuvring. In my opinion this fuel usage would be comparable to that of a turboprop, but at a performance level a turboprop is unlikely to match.

An instrument landing system approach was flown using HUD symbology, although the head-down MFD could also be used. The approach was flown at 130kt with take-off flap to a roller landing from 120kt. Two further visual circuits were flown, with the last one using landing flap, a downwind leg at around 130kt, base turn at 115kt, final approach at 110kt and touchdown at 95-100kt. The aircraft showed excellent speed stability around finals and could be placed accurately on the touchdown point. Landing roll was around 600m and the gear felt progressive and forgiving. We shut down after a flight time of 1h 10min and had used 450kg of fuel.

Having flown many in-service basic and advanced trainers such as the Tucano and Hawk, I was impressed with the M-311. The aircraft has a superb blend of precise handling yet docile and predicable behaviour, excellent medium and low-level performance and a comprehensive suite of avionics. The basic airframe has been around for a while, but the M-311 feels like a modern trainer designed for the mission.

Training becomes even more productive when allied to embedded simulation using a datalink and computerised mission planning, briefing and debriefing using commercial laptops, plasma TV screens and cockpit video playback, all of which I saw after the flight. The mission data is stored on a small memory "flashcard" and loaded in the cockpit where it is linked to the aircraft's mission computers.

There is no doubt in my mind that the M-311 could cover the basic and advanced training phases as envisaged now or in the future. Moreover, I perceive the on-board systems to be good enough to cover most of the presently designated tactical phase. The M-311 would readily complement a lead-in fighter trainer such as Aermacchi's own M-346, BAE's Hawk 128 or the Korea Aerospace Industries T-50.

A critical element of Alenia Aermacchi's next-generation pilot training package, the M-311 is a delight to fly and as a jet, in my opinion, offers significant performance advantages over competing turboprops, but at comparable fuel flows, similar life-cycle costs and almost identical acquisition costs. Its main advantages are operationally equivalent low-level cruise/attack speeds, swept-wing ride/gust response, and a cockpit environment with improved forward field-of-view over the shorter jet nose.

See other test flights here....
Craig Hoyle's military trainer review
Training with jet or turboprop