Airtest- Eagle X-TS

The concept, the late seventies vision of mining brothers Deryck and Neil Graham, was intended as an affordable bush aircraft with exceptional visibility and benign low speed manners to replace Cessnas for safe low level sheep mustering. They chose the then fashionable canard layout because both such flying surfaces efficiently contribute to lift, and when the forward one stalls first (as it is designed to) the aircraft automatically recovers. The prototype’s front wing had significant anhedral and, with considerable dihedral on the rear it looked from head on like the X-wing fighter, inspiring its X-Ts (X-wing two seater) designation.

The project suffered from a difficult and prolonged gestation, and I have only been able to trace much of its history by hearsay. It seems that, initially funded by the Grahams, their company was later floated on the Australian stock market to absorb several millions of dollars of venture capital. But their resources were spread too thinly, with more than forty employees engaged, not only on airframe and aerodynamic research, but on developing layup techniques and special resins. Yet they sold no airframes, so had no income.

Then the Malaysian government came on the scene. Primarily interested in the composites technology, which they rightly see as vital to their country’s continued industrialisation and economic development, Malaysia initially acquired fifty per cent of the stock. Then, in May 1993, they bought out the whole company, installing as Ceo ex-Airbus luminary Peter Schoonens to impart a new and more professional drive.

During the rather protracted evolution (with its fair share of dramas) aerodynamicist John Roncz came over from the Usa to refine the aerofoils, and local aeronautical consultant Graham Swannell was brought in to refine the design and take the project through to certification. Graham qualified in aeronautical engineering at Sydney and for the last seventeen years has run a successful consultancy business. He was also responsible for the wonderful little super lightweight O-200 powered all composite Maverick aerobatic single seater among other less well known designs.

The first of three prototypes, an overweight 50hp (37kW) single seat ‘proof of concept’ airframe, is now in Sydney’s Powerhouse Museum and the second, still flying, O-200 engined two seater, is destined for Perth’s Aviation Museum. The third, Io-240 powered airframe is more representative of production models, and continues to fly for development. I flew the fourth machine — the first production aircraft — which will be the company’s demonstrator for the foreseeable future.

The next half dozen airframes have been sold to Western Australia’s Department of Conservation and Land Management (Calm) as bush fire spotters and support coordination aircraft. These are in various stages of completion, with a couple already flying, and all six should be delivered by the end of June. The current two per month production rate is planned to grow quickly to eight per month (with a staff increase from 130 to 250) by Christmas, while the four month order to delivery time is expected to extend as demand builds.

Eagle Aircraft’s imposing 6300m² factory proudly flies the flapping flags of Australia, Western Australia and Malaysia. The spotless building is divided into zones for welding, metalwork, canopy moulding, wing bonding, fuselage construction, a strength testing rig, a paint shop and a laminating room. Both the avionics and the Continental engines are imported from the Usa, and rows of boxed Io-240s await installation. The upstairs offices, with panoramic views of the Indian Ocean, house the design engineers’ Computer Aided Design (Cad) equipment, whilst executive and admin staff work at ground level. Technical staff work in smaller buildings outside with a team of R&D scientists who experiment with resins and techniques to solve production problems and refine manufacture. Long term plans include doubling the factory’s size, construction of a component production satellite in Malacca and possible relocation of some facilities to Jandakot Airport, where I was introduced to Vh-Ahh by company marketing manager Denis Macneall and test pilot Sciona Browne, who has been involved with the project right from its early stages.

The all composite aeroplane is certainly eye catching, standing high on a tricycle undercarriage, with conventional oleo nose gear and well faired U shaped glassfibre main legs. All wheels would normally have fully enclosing spats. The neatly cowled engine fairs smoothly into a generous, specially strengthened cockpit pod, which then tapers back to a slim tail. A multi bolted manufacturing joint in the aft fuselage will be dropped from future aircraft which will have detachable wings for easy shipping. Long ventral and dorsal fillets lead to a tall fin and aerodynamically balanced rudder with an anti-servo tab to increase feel and effectiveness. The fixed tailplane was added to improve pitch stability and to allow lift increasing flaps on the canard. The structure uses aerospace quality Kevlar and carbon fibre cloth vacuum bonded with vinyl ester resins over Nomex honeycomb, and has a 2.25 strength factor, as opposed to aluminium’s 1.5 limit.

The 7.16 metre span main wing is shoulder mounted just aft of the cockpit, while the much shorter canard attaches to the lower firewall. Both surfaces sport fashionably upturned tips and have clearly undergone considerable aerodynamic modification to achieve Jar-Vla’s required 45 knot (83kmh) stall. Thus there are fixed 67cm long leading edge cuffs and stall wedges inboard on the canards and a metre long cuff, a chordwise fence and four large upper surface vortex generators on each outer wing. While the wings have normal differential, mass balanced, slotted ailerons with nicely narrow gaps, the canards only carry flaps. These are duplicated on the main wings and all four electrically powered surfaces run simultaneously to a maximum of 36 and 38 degrees respectively. The canards’ flaps are faired with their trailing edges when retracted, but the main wing flaps rise around five degrees up to reduce drag and increase cruise speed.

Instead of specifying Lycoming’s commonplace 100 to 120 horsepower O-235, Eagle Aircraft chose Teledyne Continental’s newly relaunched and slightly more powerful Io-240. A refined and fuel injected development of the 1960s Aerobat’s O-240, this develops 125 horses (94kW) at 2800rpm. The current wooden propeller is mounted on an aluminium extension which will be deleted when the proposed metal prop is used.

The broad, optically clear canopy is locked with a substantial 180 degree handle to hinge up forwards. Fitting snugly, it can be held a few centimetres open by a simple latch on the left sill, and has an inflatable seal which is pumped up with a rubber bulb stowed to the left of the seat. The 1.07m wide cockpit is roomy, and the well padded, fabric covered, semi reclined seats are very comfortable. Between them the single stubby side stick has a light, frictionless feel and a stick top electric trim switch operates the right elevator’s tab. Aft of the stick are the spring biased aileron trim, a small armrest and, neatly out of the way behind one’s elbows, the headset plugs.

On a sloping sub panel ahead of the stick is the simple rotary on/off fuel cock. Above it a neat row of circuit breakers and switches serve the electrics, magnetos, fuel pump and avionics. A coaming top Garmin Gps is standard, as are a central 750 channel King Vhf and transponder. The orderly instrument panel contains the usual six dials with all electric gyros and four warning lights for oil pressure, failed alternator, Gps message and low fuel. To the lower left are the alternate air knob and the ungated flap switch, which can be overridden by the instructor’s symmetrically placed twin. Although there is a trim position indicator above the central panel, there is none for the flaps so blue painted segments on the canards establish the ten degree takeoff setting.

The right panel holds a set of digital/analogue Lcd engine gauges. There are small vents on the sidewalls and the narrow side ledges hold the twin throttles, beside the left of which is the single ratcheted mixture lever. Here also is the sole unusual control — a small switch for electrically adjusting rudder pedal position, a neat innovation which dispenses with the usual foot well fiddling, and makes cramp relieving inflight leg stretching a possibility at last; a useful facility with the Eagle’s five hour endurance.

A plastic flap behind the occupants’ heads covers a 25cm high, 1m by 50cm hat shelf approved for up to 9kg. Pulling forward the moulded fibreglass seat backs reveals two more irregularly shaped 18kg luggage areas 30cm wide, 20cm high and 70cm deep, for nylon overnight bags.

The airframe weighs 430kg and its 650kg maximum is well within Jar-Vla’s 750kg limit. This allows two 77kg pilots to take 90 litres of fuel for a three hour flight at 75% power with a 45 minute reserve. Filling the 100 litre tank allows five hours of flight to empty tanks with one 77 kilo occupant and another of 65 kilos. Altogether the Eagle will legally carry twenty kilos more than a Cessna 152, and for our flight we had sixty litres of fuel, to total slightly under 630kgs.

If depressed when in its rightmost start position, the rotary magneto switch activates an electric priming pump. Twisting and pushing, I quickly brought the engine to life, checked its gauges, switched on the avionics and, after releasing the park brake valve under the seat front, was ready to taxi. The aircraft’s short span makes it extremely easy to manoeuvre in tight spaces, although you have to be aware that the wings behind your head are longer than the more obvious canards ahead.

The Eagle has a castoring nose wheel, and its differential braking system is a little unorthodox. The brakes are operated by increasing pressure on the rudder pedals. Braking does not occur at the end of the pedal travel, but feels rather more as if one’s feet are pushing on the top part of a conventional pivoting rudder and brake pedal. With a little practice the aircraft can be made to go precisely where one wants, but the system invites inadvertent retardation on takeoff. Denis feels an ab initio student unused to normal brakes might quickly adapt, but I think Eagle Aircraft would be wise to press ahead with developing a more traditional system.

Ten degrees of flap are used for takeoff, and the only unusual predeparture check is to inflate the canopy seal. Restricting myself to light pedal pressures (to avoid unintentional braking) resulted in a gentle leftward tendency during our roll. The low inertia wood propeller allowed rpm to build quickly, acceleration in the thirty degree heat was fair if not rip snorting and, with a positive rotation at 65 knots (120kmh), we left the ground effortlessly after running about 400 metres over gravel. Flap retraction caused a little sink before establishing a normal 500fpm climb at eighty knots (148). Although as good as a Tomahawk or Cessna 152 could achieve in similar conditions, this is still a little disappointing.

The fixed pitch propeller restricts engine rpm to 2500 (or 85hp 63kW) during takeoff, but a finer pitched prop would limit the cruise speed. Nevertheless Denis maintains that, flying solo with half fuel, he can generally break ground in just 200 metres in a ten knot headwind on a 25 degree day, and has climbed to 5000 feet in nine minutes at 37°C, while the brochure quotes a 440 metre run at max weight to clear a fifteen metre obstacle and a 633fpm climb in Isa.

Just a couple more horsepower on takeoff would make a big difference to the Eagle’s performance, and proposed improvements include fitting a better matched metal prop (whose thinner, more efficient blades will often increase thrust by up to 10%), retiming the camshaft and reshaping the engine’s cam lobes for a flatter power curve. These mods could double the climb rate without resorting to a heavy, expensive and complex variable pitch prop. Meanwhile, high temperature takeoff performance investigation continues at the hot inland airfield of Cunderdin.

One advantage of the current propeller is that climb rate and angle do not vary much with increased speed, so a 100 knot (185kmh) cruise climb gets you usefully on your way, an attribute exploited by Calm, who prefer the Eagle’s improved get to the troublespot speed over that of their old Piper Cubs.

The Eagle’s excellent visibility was apparent right from the start. Inevitably the nose caused some obscuration in the climb, but the canard does not intrude because it is short and slim, and so far ahead that it barely affects the superb downward view. The main wings sprout from behind the occupants’ shoulders, so they remain unnoticed. Significant right rudder is needed in the climb but, after levelling, the rudder pedals can be run forward to increase the already generous leg room. The cockpit is comfortable at all times, with reasonable space, plenty of foam padding in the cushioning and adequate face level ventilation. A heater is standard, and improved foot well cooling is in hand.

Levelling at 2000 feet and throttling back a little to remain within the 2800 maximum continuous rpm, our full power speed quickly increased to an impressive 117 knots (217kmh) Ias at 21 degrees Oat (123 knots 227kmh Tas). Propeller improvements and good spats should further increase top speed. Normal cruise at 2600rpm returns 115 knots (213kmh) Tas for a miserly 26 litre per hour fuel endurance at sixty per cent power is five hours, for a 536nm (993km) range. The noise level is very low, even with the canopy seal deflated, thanks to the Eagle’s clean aerodynamics.

Its high wing loading gave a good ride through the convective bumps, and cruise stability was truly positive in all three axes, making this aircraft much nicer to fly than any similarly sized homebuilt. Although many of these boast of higher speeds on similar power, this is almost always at the expense of a potentially hazardous lack of stability (one reason why few can meet Jar-Vla without modification).

The Eagle’s controls are remarkable, quite brilliant. Ailerons, elevator and rudder are all light and effective, with a very impressive roll rate, and only the slightest rudder is needed for low speed coordination. Roll damping is almost instantaneous, the motion stopping immediately the stick is centred, so this machine would be perfect for making eight, sixteen or even 32 point rolls. Current g limits are +3.8 to -1.9, but aerobatic certification is being considered. All controls remain effective ten knots above the stall, becoming sensibly firmer as the 165 knot Vne is approached without ever getting heavy. The main problem at high speed is throttling back to restrain revs below the red line.

The Eagle’s canard gives it truly remarkable low speed manners, and stalls are a non-event in all configurations. Without flap, the warning horn starts at 65 knots (120kmh) and the nose gently pitches forward from ten degrees above the horizon to five degrees below it at 55 knots (102). With the stick held hard against the aft stop the nose remains below the horizon, but nods slowly up and down while the aircraft buffets and sinks at quite a high rate under complete control. Applying power promptly stops the descent.

Flap limit speed is 100 knots (185kmh) for up to ten degrees, and 85 knots (158) thereafter. The first fifteen degrees cause a very slight pitch up and a gentle backward stick movement. Stall behaviour with part flap is identical, but a couple of knots slower, while full flaps causes a noticeable increase in drag, a 45 knot (83kmh) pitch down and a significant descent rate in considerable buffet. But the aircraft remains in full control, and adequate roll capability is still available with the stick against the aft stop. Applying power lifts the nose and reduces the descent, but causes no departure from controlled flight. Stalls in even steep turns are a non-event, and with full flap, full power and full rudder (the worst possible mishandling) the most spiteful revenge the aircraft can muster is to waffle wings level and regain normal flight. The manual justly mentions that it is extremely hard to induce a spin; this totally amazing stalling behaviour is a credit to both aerodynamicists and test pilot and, while making the type ideal for its intended mustering role, renders it superbly safe for any flying.

The circuit is flown at ninety to 100 knots (167 to 185kmh), reducing to 85 (158) to take part flap for a base leg at eighty (148). Downwind checks should include adjusting rudder pedal position, with a mental note not to press too hard on them during rollout. Final approach is flown with power and full flap at seventy knots (130), which is rather more than 1.3 Vs because of the wing loading’s potential to develop an excessive sink rate at lower speed (although, in testing, approaches have safely been flown at minimum speed with the stick on the back stop).

The full flap glide angle is steep but, while I had too little time to experiment, Denis assured me that flapless approaches were innocuous, providing the speed is kept up to counteract that possible high sink rate. Sciona has developed a carrier deck touchdown technique, flying the aircraft onto the runway but, after a couple of touch and goes, I discovered that a normal flare and low hold off for a minimum speed touchdown worked better for me, provided I was careful not to over control in pitch to induce a balloon. Our landing roll out used perhaps 450 metres.

The Eagle is a remarkable aeroplane, with point and shoot manoeuvrability both in the air and on the ground.

Although its forward flying surface is referred to as a ‘canard’ this aircraft displays none of the canard’s usual handling idiosyncrasies

 and is perhaps better regarded as a low drag biplane. But it has the considerable advantages of being far more comfortable than any biplane I have ever flown, much quieter, with infinitely better visibility and a great deal easier to land. Its canard endows incredible low speed tenacity, while the addition of a tailplane puts the aircraft in the same category as the Piaggio Avanti. With a broad speed range and a good 7.5:1 lift/drag ratio it is nearly as fast as similar powered Lancairs, Glasairs and Rv-6 homebuilts, with equally crisp handling, but much easier to fly, more comfortable and, of course, properly certified.

After a difficult early life, the company now has a much more professional structure and considerable capital. Their product is aimed at the trainer and two seat private tourer market as well as for outback sheep mustering, but it can clearly fulfil applications in the low cost observation and surveillance roles. Aerobatic clearance is rightly under consideration, and a growing family of four and six seaters is in prospect. Perhaps Malaysia and Australia’s unconventional Eagle X-Ts is the shape of things to come.