SKY ARROW (Kits) UK Ltd

Hangar 3,Old Sarum Airfield,Salisbury,Wiltshire, UK,SP4 6DZ Tel: + 44 (0)1722 336686 Fax: + 44 (0)1722 410678 info@skyarrow.co.uk 

Flight Test of the First Kit Build Sky Arrow in the UK

Derek Piggot first saw the Sky Arrow at Lasham and was attracted by its good looks. He has since put it through its paces and tells us the story.

Photos: Ed Hicks Article reproduced with permission.

No one will deny that the Sky Arrow is one of the most attractive little light aircraft on the market today. A close inspection shows that much thought has gone into the design and construction and there are many novel features of interest to the home builder and to other aircraft designers.

The manufacturer, Iniziative Industriali Italiane SpA has 50 years' experience as an aircraft manufacturer and more than five years` experience with advanced composites There are a number of variants of the Sky Arrow all available in kit form.

The 650T kit versions are the only models which have been approved by the Popular Flying Association. It is now available with a metal wing and main undercarriage at a greatly reduced cost. Using metal in place of the carbon fibre reduces the cost of the kit. 

Incidentally, the kit includes the engine and propeller, instruments, adhesives and practically everything needed apart from finishing materials.

The Sky Arrow originated as a military design for surveillance, supported by the Italian government and there is no doubt that but for its origin it would have been a vastly more expensive machine. Without such backing it would have been too expensive to use carbon fibre so extensively throughout the structure It is stressed for the usual +3.8g and -1.9g with an ultimate of +5.7 and -2.85, although it has been tested to +7.6g and -3.8g at 54 deg C.

The kit comes in sections with all the minor parts carefully labelled and packaged with their main components. This is obviously a very high quality kit. All the parts are beautifully made and the drawings and instructions for assembly are very comprehensive. In fact there is a great pile of paper work, all in English, to help the builder through every stage of the construction. Even the wiring for the instruments is made easy by using a full scale drawing as a jig to get the exact lengths of wire required and the correct routing. This normally rather confusing and complicated job is made very simple and the result is a very professional loom.

All the major components such as the wings and tail come fully fabricated and no jigging is required. Everything except for paint finish is provided.

In spite of the completeness of the kit, there is no doubt there is more than 600 hours of work for the home builder, but the result must be a very elegant machine and worth all the effort.

I first saw the aircraft at Lasham in its unfinished state (although it had been flown) and was immediately attracted by its good looks. This was going to be one aircraft I must fly to see if it was as good as it appeared. The kit had been assembled at Old Sarum by Sky Arrow Kits UK Ltd., with the final finishing done professionally at Lasham by Southdown Aero Services in order to get it done in time for the 1997 PFA Rally at Cranfield. Another Sky Arrow is well advanced at Old Sarum and progress can be seen in the hangar there. Why not fly in to have a look?
It is powered by the Bombadier Rotax 912 which produces 81 hp at 5800 rpm. This rpm sounded rather high to me, but because of the 2.27 reduction gear the propeller is rotating much slower, so improving the efficiency and reducing the noise created. Cruising at 5000 rpm, for example, gives a propeller speed of only 2200 rpm and a very low noise level.

Pusher propellers are usually much noisier because they have to work in the disturbed air from the exhaust and behind the wing and fuselage. This sets up extra vibrations and usually a distinctive sound. I made a point of standing on the ground to listen to the noise at full power just after take off and was pleasantly surprised. In comparison with the other light aircraft it seemed much quieter. The liquid cooled cylinder heads also help to reduce the noise The noise and vibration level inside the cockpit in night is also very low.

The full tank holds 18 gallon and is mounted behind the rear seat and below the engine firewall. As the tank is semi-transparent the actual fuel level in the tank can be seen by lifting the seat back (a few seconds: job) during the preflight inspection, far better than relying solely on an electric fuel gauge.

A full tank gives about four hours of safe flying when cruising at about 85 knots. The oil contents can be reached through an inspection panel in the top of the engine cowling.

The main undercarriage legs are Cessna type made in glass and carbon fibre on the original versions but later in metal. The wheels are 11 ins in diameter with disc brakes ensuring a good ride and efficient braking on rough grass fields. The nose wheel is sprung with rubber blocks and is free castoring. Steering is by using differential braking and, of course, helped by using the rudder with the propeller slipstream.

The wings are parallel chord and braced by a single streamlined strut. The brochure shows the aircraft being towed by car with the wings folded alongside the fuselage. It should be an easy task to de-rig for transportation in this way. The plain flaps are electrically operated and are selected by a four-position switch giving 0 deg. 10 deg, 20 deg and 30 deg stages. The position of the switch indicates the amount of flap down.

The aileron circuit is remarkable for the very low friction. They are Frise ailerons with some differential.

The Tee tail attachment is conventional glider practice and the tailplane can be easily removed. The elevator trim tab is electrically operated by two flush buttons on the top of the stick with a trim position indicator on the instrument panel.

The one-piece canopy has a very sturdy carbon and glass frame and opens sideways to allow easy access to the front cockpit. There is a step to help getting into the rear seat. There would be room for wearing a slim line parachute with the seat cushions removed, but with a pusher perhaps parachuting is not to be recommended.

Five point harnesses are provided for both seats and unlike so many, the bottom straps are tightened by pulling upwards, the only sensible way. The rudder pedals in the front cockpit are readily adjusted to cater for different pilot sizes.

I found plenty of room in both cockpits with my arms comfortably supported by the flat top of the cockpit side walls On the: right hand side the side mounted stick, wheel brake controls and canopy jettison control and to the left, the throttle, choke and carburettor heat control come easily to hand. The fuel / ignition cock is also on the left hand side to the rear of the throttle. Switching it off automatically cuts the ignition as well, a useful feature in an emergency. The side stick has the advantage of leaving the cockpit floor completely clear and also makes it much easier to get in and out. The canopy locks are very positive and cannot he accidentally unlocked. When unlocked, there is a small gap showing below the canopy frame making it unlikely that it would go unnoticed. The canopy locks look proof against the most incompetent pilot.

The beautiful clear canopy has a direct vision window on the left hand side. Cockpit heating is by ram air and very effective and the front of the canopy is de-misted with air bled through the canopy frame.

I found that I could read all the essential instruments quite easily from the rear cockpit. One nice feature is a warning light system with four lights to let both pilots know immediately of a potential engine problem. In the event of the generator regulator, radiator temperature, oil temperature or oil pressure failing or getting out of the normal range, the appropriate distinctive red light appears, drawing attention to the trouble.

The demonstrator was fitted with normal instruments and there is plenty of room for a GPS and for a second radio if required. Another feature is that the whole instrument panel is easily removable for storage or working on at home It features a multi-pin plug for the electrics and a pneumatic connector to the pressure and static ports.

Man-handling the Sky Arrow out or the hangar is particularly easy as it is very light A small download on the tail boom lifts the nose wheel off the ground and the main wheels are positioned so that with no crew on board, the aircraft will sit either with the tail down on the ground or on the nose wheel. This tail down position makes looking over the tailplane and elevator very easy for the daily inspection.

The parking brakes are applied by lifting and turning the small knurled knob just ahead of the brake levers and then pulling both levers hack with the right hand.

The designers have clearly gone to some lengths to avoid pilot errors and the two magneto switches are the type which are locked ON or OFF so it is impossible to knock them off by accident. To operate them, the toggle of each switch has to be pulled out before it can be moved on or off.

It is recommended to use MOGAS in preference to 100L and the fuel system has been designed with this in mind, with a bleed pipe from close to the carburettor back into the fuel tank to eliminate vapour locks. A stainless steel fire wall extends below the engine with a drain to outside the bottom of the fuselage to cater for accidental spillage of fuel.

As the tank is below the engine level, the initial start requires the electric pump switched on for a few seconds to prime the system. It should be used for the take off and approach but only the engine driven pump is used in normal flight. Once again I will appeal to all aircraft manufacturers to fit an indicator light to indicate that the pump is on, a reminder so often needed by me and many others as well, I suspect. The choke is only required in cold weather and perhaps for the few seconds on the first start of the day.

Once the engine is running, the four warning lights go out and you are ready to taxy. With the free castoring nose wheel, the wheel brakes are needed for controlling direction. You need your right hand to operate the brakes and there is no alternative but to let the stick go to find its own position. Taxying is done with the left hand working the throttle and the other for using the brakes. Although the brake levers are only a few inches long, the hydraulic system does a wonderful job and the forces required are remarkably small and need only one finger pressure.

It seems very unconventional to taxy without a hand on the stick, but the Sky Arrow is stable enough on its three wheels for crosswinds not to cause any problems in normal flying conditions. With no engine in front, the visibility for taxying is near perfect and similar to most gliders.

On take off you are immediately aware of the very low friction in the control circuits and in particular with the ailerons. The acceleration is brisk and I do not doubt the manufacturers claim that the take off run is 8OO feet on smooth ground. A very unusual phenomenon on this particular aircraft is that the ailerons oscillate from side to side with every jolt on rough ground. The stick is almost impossible to hold still at low speeds.

The exact cause of this seems to be a combination of things. The friction in the control circuit is extremely low and so does nothing to damp the movements out. It only occurs while the aircraft is on the ground and I found no tendency for the stick to twitch sideways in the air and at first I was mystified as to the cause.

  Usually this kind of oscillation would be caused by lack of mass balance in the ailerons. However, in this case it seems most likely to be caused by the weight of the side-stick itself. With the ailerons neutral the stick is at an angle so that any sharp bump on the ground results in the stick moving downwards, applying the aileron. In the air, the air loads completely eliminate this effect and the aileron control is very light and pleasant at all speeds.

It would be nice to try to improve this, although it is quite acceptable from the airworthiness point of view. I have suggested that the manufacturers are contacted to discuss possible solutions.

I have met the same kind of problem on several prototype gliders, but this was whilst flying in turbulent conditions and was caused by lack of mass balance on the ailerons. It disappeared immediately the mass balance was increased. In the gliders it shows up with a tendency for the aileron to snatch in bumpy air. This is not the problem with the Sky Arrow.

After my first take off. I found myself somewhat reluctantly agreeing with Raymond that on rough ground it is best to allow the stick freedom of movement sideways during taxying and the start of the take off, rather than to try to hold it still.

It seemed best to make a firm backward move on the stick to help the rotation at about 45 knots and within a few seconds it is climbing away rapidly, going up at over 700 feet per minute.

Once off the ground, the side stick feels quite normal and the stick forces are all quite low. The handling delightful with the Frise ailerons reducing the stick forces for manoeuvring at flying speeds. After a few minutes flying the stick system seems absolutely normal.

Cruising at about 65% power and about 5000 rpm, the airspeed settles at about 85 knots and the vibration and noise levels are low. The all-round view from the front cockpit is superb and even from the rear is much better than in most high winged aircraft.

The electric elevator trimmer is operated by two push buttons on the top of the stick. With them you re-trim with short bursts of pressing one of the buttons. It seemed to me that getting into trim becomes largely a matter of trial and error. I can well understand that after a few flights it becomes easier and more natural to use. I would prefer a small lever, the position of which dictates the position of the trim tab, operating rather like the servo system on a proportional radio control model.

I would certainly want to move the Press to Transmit switch from its present position in front of and just below the top of the stick where it is invisible and inevitably gets pressed unintentionally. Fortunately this is the kind of mod. that can easily be authorised with PFA aircraft; particularly when built from a kit.
    

This is an extremely easy machine to fly because there is so little change of trim power on or off. I tried going from no power to full throttle and back and was unable to decide which way the aircraft yawed and there was virtually no pitch change either.

The adverse yaw is not excessive and the aileron control is pleasantly light at cruising speeds. Only a small amount of rudder is needed when entering turns and I found myself tending to over rudder going into and out of turns quickly, but as a long time glider pilot this is only to be expected.

I was reminded of the latest Super Dimona which also has no apparent yaw with a change of power. Yet the Katana, which appears to be a short wing span version of the Dimona and is intended for basic training, has large trim changes with power, particularly in yaw. I find myself asking why they make trainers more difficult to fly for the beginners? Is it so that it takes longer to master and so is more profitable for the operators?

We flew with about half fuel and a cockpit load of about 330 lbs which put the cg fairly well forward. With a maximum flying weight of 1433 lbs and full fuel, there is still about 410 lbs available for the two crew.

At this cg position, the stalling is honest, with a definite nose drop and occasional fall off to one side, but with no tendency to spin. It is not cleared for spinning in this country so it was not possible to make a full blooded stall and full rudder attempt. Misusing the rudder during the stall results in a definite wing drop, but recovery is very quick with relaxation of backward pressure on the stick. The stall occurred at about 40 knots IAS with some buffet a few knots before the break. There is a stall warning buzzer which on this aircraft came on at about 10 knots before the stall. With full flap the stall speed was reduced by two or three knots.

The liquid cooled cylinder heads greatly reduce the risk cracking due to rapid cooling when descending and this feature together with the 2.27:1 reduction gearing for the propeller reduce the noise levels, both in the cockpit and from the ground.

With such simple handling there is not much to say about the circuit flying. The outstanding visibility makes it pleasant to be amongst the other traffic, in fact you really feel sorry for the other pilots driving round with limited vision.

Full flaps gives a good rate of descent and an approach speed of 55-60 knots is enough to give a fair float before touchdown. The flaps together with side-slipping should make it an easy aircraft for spot landings. Being a nose wheel machine there is no question of swinging or ground looping and it is approved for a cross-wind component of up to 15 knots.

I made a further landing from the back seat to assess the visibility and comfort and was very happy with it. It would be a fun machine for instruction and very easy for a student to master.

All in all, this is a beautiful little aircraft with a good performance. The outstanding view from the cockpit is a real pleasure. The lack of trim changes with power is remarkable and makes it particularly easy and enjoyable to fly.

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