Peter Henley/MOSCOW
Russian light aircraft designed for general aviation - excluding the aerobatic Yaks - are virtually unknown in the West. The territory traditionally claimed by Cessna, Piper and Grob has not, until now, been challenged by the Russian aircraft industry.
The SV Ilyushin Research and Production Complex aims to change the status quo and has been involved in the design and development of the Il-103 since the early 1990s. Work has continued to the point where US (FAR 23) and Russian certification has been won.
The philosophy has been to produce a simple, versatile, multipurpose, single piston-engined light aircraft, the appeal of which would lie in its quality, purchase price and operating costs, rather than in defining a new level of technical innovation. The construction is consequently conventional - all metal, with a semi-monocoque fuselage and a wing of riveted spars and ribs. Composites are used only for non-load-bearing fairings.
To add worldwide appeal to the design, major components have been bought in, bringing with them worldwide support. The engine is a Teledyne Continental 1O-360ES producing 160kW (210hp) at 2,800rpm. It is fitted with a Hartzell two-bladed constant-speed propeller, and the option of Western flight instruments and communications and navigation equipment is offered.
The primary flying controls are conventional in design and operation, being mechanically linked by rods to the ailerons and elevator and cables to the rudder. There is electrically operated pitch trim, but no rudder or aileron trim other than fixed pre-set tabs. The flaps are plain hinged, single slotted and manually operated. The fixed undercarriage is similarly straightforward, with spring steel legs, a castoring nosewheel and hydraulically operated disc brakes with an anti-skid system for the main wheels. Two wing tanks hold 200 litres (50USgal), of fuel. A fuel reservoir is fed by gravity from the tanks and an electric fuel pump supplies the engine injectors from the reservoir. Clearly, the Il-103 is essentially 25-year-old technology.
The Moscow-based Ilyushin Design Bureau was responsible for the design of the Il-103, but its manufacture is undertaken at the Lukhovitsi Machine Building Plant, about 145km (90 miles) south-east of Moscow. Here, light aircraft are assembled alongside MAPO MiG-29 fighters. The factory is on the edge of a large flight-test airfield and it was from here that Flight International flew the aircraft.
The Il-103, registered RA61913, is a production aircraft. Its cockpit is configured for two pilots seated side by side, with a double passenger seat behind. The canopy has two gull wing doors, hinged along the centre line of the transparency. The cockpit is entered via a step behind the wing root and a walkway on the top surface, negotiated with the aid of a small handle on the side of the fuselage. It is possible, but not easy, to step from the wing directly on to the cockpit floor. Once in the seat, it can be adjusted for reach and height; the rudder pedals are not adjustable. The seat is comfortable, has an easily fastened four-point harness and adequate elbow room. The field of view is good, except for vertically downwards (as the cockpit is directly above the wing), and the windscreen pillars are wide and a little intrusive, but I soon adjusted to looking around them. The tailplane on each pilot's side of the aircraft can easily be seen through the rear side window.
Simple start
Chief test pilot Yuri Abramovich took the right-hand seat and started the engine simply by turning on the battery master switch, priming the injectors, putting the rotary magneto switch to "Both" and pressing the electric starter motor button. The throttle had to be opened progressively until the engine fired, after which it ran smoothly at 50% rpm until warm. The parking brake is operated by a handle on the instrument panel between the pilots. Releasing the wheel brakes and applying a little power moved the aircraft, after which the speed could easily be controlled with the throttle. The aircraft is steered via differential wheel braking, applied by large, convenient pedals mounted above the rudder bar. The brakes were smooth and progressive, but using them for directional control took a little time to master. I would have preferred the castoring nosewheel to have been steerable via the rudder pedals.
Although the Hartzell propeller has a constant speed unit, the blade angle is not adjustable from the cockpit, and there is no pitch control lever. A small centre console houses a throttle lever and its friction adjuster, and the fuel-mixture control. There is a duplicate throttle lever in a quadrant on the cockpit wall by the left-hand pilot's left thigh. Each throttle lever grip has press-to-transmit and intercom buttons.
The flaps have four positions - up, 10°, 20° and 30° - and are operated by a lever mounted on the floor between the left-hand pilot's seat and the cockpit wall. The lever locks into a detent for each flap position and is released by a thumb button. The quadrant through which the lever travels is marked with the flap positions, but there is no flap-position indicator on the instrument panel. If the aircraft were used for flying instruction, the instructor pilot in the right-hand seat would have no control over the flaps and would not be able to see the flap lever. The position of the lever is not easily seen by the left-hand seat occupant either, and both pilots tend to look out at the flaps themselves to confirm their position. An indicator visible to both pilots would be an advantage, as would a flap selector on the centre console and therefore available to both pilots.
The flaps were set at 20° for take-off. I opened the throttle smoothly to full power, keeping the aircraft straight using differential brake, until the rudder became effective. Here again, directional control during the early part of the take-off run would have been easier with a steerable nosewheel. Once airborne, the flaps were retracted; the travel of the flap lever from 20° to up was through an arc of about 30° and finished with latching the lever against the cockpit floor. The pilot has to move his head and shoulders while reaching down to operate the lever at a time after take-off when he should be concentrating on establishing and maintaining the attitude of the aircraft. There was little discernible trim change as the flap was retracted.
This aircraft had standard production instrumentation and avionics with Russian presentations and legends, so the cockpit was not particularly user-friendly for a Western pilot. The avionics would be fitted to customers' requirements, so there is little point in assessing the instrumentation other than to say that the layout is not in logical easy-to-find groupings. The sales brochure, however, illustrates other, neater and more logical, choices of instrument panel layout. Navigation equipment is an AlliedSignal Bendix/King KNL-89B, with a global positioning system and automatic direction finder.
The recommended take-off technique was to raise the nose at 43kt (80km/h) and unstick at 54kt. This worked well, and the aircraft settled comfortably into the climb at 80kt. Pitch trim is via an electric motor controlled by a "coolie's hat" trim button on top of the pistol grip of the control column. At 81kt in the climb, with full power, a snapshot check of static stability showed good positive longitudinal stability, while a doublet applied to the rudder pedals produced natural damping in about one and a half cycles.
The longitudinal and directional control forces were well harmonised and pleasant for this class of aircraft. The exception was the roll control. Here the break-out forces were high and the roll acceleration and rate of roll disappointing. I had expected to find the Il-103 wanting for lack of a rudder trimmer, but this was not so. During changes of power and speed, the change to directional trim was small and could easily be countered by light foot pressure on the rudder pedals. During acceleration and deceleration checks, the longitudinal pitch change was small and simple to trim. The electric pitch trim was easy to use and rate of change was ideal.
After climbing to 2,300ft (700m), three stalls were carried out: clean power-off; 20° flap power off; and clean with power. In each case, the audio stall warning sounded at about 11kt before the stall, there was little natural buffet and the stall was defined by a gentle nose drop and a fairly rapid rate of descent. With power, the pitch altitude was 20° nose up before the stall was reached.
In the power-off clean stall, the left wing dropped, but was easily recovered with rudder. The aircraft is not fitted with a stick shaker or stick pusher and does not require either. Behaviour at and near the stall was benign and safe, but, from an instructional viewpoint, it would be possible to introduce a student to natural stall warning in the form of aerodynamic buffet.
Spin recovery
Extensive cloud cover precluded climbing high enough to carry out developed spins, but, at about 3,500ft, after two turns, it was possible to explore the entry to the erect spin, recovery from the incipient spin and recovery from a developed spin. With the throttle closed and aircraft clean, full stick back and left rudder were applied at 65kt, which resulted in one turn of autorotation from which the aircraft immediately recovered when the controls were centralised. Next, from a similar entry, the aircraft was allowed to establish in the spin for two turns, from which it recovered in less than a turn upon the application of full opposite rudder and forward stick. From this brief investigation, the Il-103 seems safe for spinning, entering the manoeuvre in a smooth - almost leisurely - manner and recovering readily.
Cleared to +6g and -3g limits, the Il-103 was pleasant for flying loop aerobatics. I started a loop at 170kt and pulled 4g during the upward part of the manoeuvre. Full power was maintained throughout the loop and the speed washed off to 65kt over the top. A stall turn to the left was uneventful, but an aileron roll confirmed the heaviness of the roll control. Steep turns were pleasant to fly at 110kt, but a roll reversal from a left-hand turn to a right steep turn took time and effort. There was sufficient power to maintain 108kt during the steep turns, and loops and rolls could be flown at full power throughout. The fuel system provides unlimited time inverted, but the engine oil pressure limits permits only 5s in this position.
Engine failure was simulated by closing the throttle (Abramovich selected hot injector air for this exercise). The aircraft was easy to trim and fly at the recommended glide speed of 80kt, allowing the pilot to give attention to picking the landing area, planning the pattern and completing the checks.
On return to Lukhovitsi airfield, a straight-in powered approach was flown at 81kt, reducing to 75kt over the runway threshold. A crab approach was flown to counter the crosswind, drift was easy to "kick-off" in the flare, the aircraft behaved as it should in ground effect and the touchdown was easily controlled. The runway was of large concrete slabs that had become uneven with age. During the ground roll, there was considerable vibration in the cockpit and lowering the nosewheel on to the runway caused some shimmy. From the touch-and-go, two circuits were flown. The first was from 1,400ft with a glide approach - the throttle being closed downwind at the point abeam the runway touchdown point. Excess height on the final approach was lost by side slipping the Il-103 at 81kt. The aircraft handled pleasantly and safely throughout.
The final circuit was flown at 500ft as a bad-weather circuit, using power to maintain height on the final turn. Extending and retracting the flaps close to their maximum limiting speeds (10°/102kt, 20° and 30°/97kt) caused pleasantly little trim change, while the control force needed to move the mechanical flap selector lever did not markedly increase with aerodynamic load at the higher speeds.
The ground-run harshness and nosewheel shimmy were common to all three ground runs, the shimmy disappearing as the speed was reduced to taxi. I felt that the spring leg design was neither as compliant nor, paradoxically, as stiff torsionally as an undercarriage with oleos and trailing links might be.
At the post-flight debriefing, I raised my concerns with Il-103 designer Andrei Pupkov. He explained that a nose oleo is being considered, but that there had been no problem with shimmy during the development flying, so the nosewheel might be maladjusted on this particular airframe.
So far as the high roll control forces were concerned, he admitted that other pilots had made the same criticism. He said that the aileron control circuit included a spring that might allow some adjustment. My own view is that a change such as adding a mechanical servo tab would be more likely to harmonise the lateral control with the other two axes - but that would involve redesign and certification issues.
With the exception of the roll control, the Il-103 is reassuring and pleasant to fly. But to sell against Western competition, its purchase price and running costs will have to be significantly lower than those of its competitors.
Source: Flight International
