Andrzej Jeziorski/WARSAW
On a blustery Tuesday, 29 October, the Polish press and selected guests gathered at helicopter manufacturer PZL-Swidnik's factory near Lublin to watch an event crucial to the future of the country's struggling aerospace industry.
The focus of attention was a little red helicopter prototype, affectionately known among Swidnik's staff as Lolek, after a Polish children's cartoon character. This was the prototype's flying debut; the public presentation of the SW-4 light helicopter, Swidnik's first new design since the collapse of Communism.
TAKING TO THE AIR
With Swidnik chief test pilot Zbigniew Dabski at the controls, the five-seat helicopter lifted gingerly into the air at 13.20h, appearing as unsteady as a baby deer in winds gusting up to 29kt (55km/h). After briefly drifting backwards, the SW-4 seemed to find its balance, rotated away from the crowd, and the pilot began a demonstration of hovers and turns with level flight at speeds up to 50kt.
Relief and pride showed in the beaming smiles of the Swidnik designers and executives when the helicopter settled comfortably to earth, and the reporters hurried towards Dabski as he emerged from the cockpit.
This was in fact the Lolek's third time in the air - the first and second flights had taken place away from the public gaze on the previous Saturday. Company officials had been debating whether to invite people to witness the first take-off, but decided that it would be unspectacular and a little too risky. There are still vivid memories of the problematic first flight of the now-successful W-3 Sokol, in November 1979. This was followed by two-and-a-half years of rotor modifications, with the helicopter grounded. The management was keen to ensure that this time, under the scrutiny of a newly free and cynical national press, things should run smoothly.
The run-up to the first SW-4 flight had suffered delays of its own. The flight was to have been carried out by the Lolek's stablemate, nicknamed the Bolek, which was the first SW-4 to be completed, towards the end of 1994. The flight was scheduled to take place in January 1995, but was halted when engineers discovered vibration and static-strength problems after engine runs began in December 1994.
Swidnik engineers discovered that the original rotor blades failed at 110% of the standard maximum operational load, while the requirement was 130%. Vibration levels were found to reach limits of acceptability at 97% of the nominal engine RPM, and improvements in damping were needed. The Bolek was thus returned to the testbed, where it has remained along with a third, uncompleted, SW-4 airframe, which is being used for structural tests.
A new set of rotor blades was completed in October 1995, and underwent extensive testing before being fitted to the flight vehicle. The vibration problem was solved with the help of Polish hydraulics specialists PZL-Hydral, which helped improve damping to reduce vibrations to acceptable levels.
PZL-Swidnik president Mieczyslaw Majewski admits that the initial date planned for the SW-4's first flight was over-optimistic. "I think we will have to approach these things a little more rationally in the future," he says.
SW-4 PROGRAMME
According to Swidnik, the SW-4 programme dates back to 1981, when the company's engineers began working on a four-to-five seat, single-engined concept which was to have been powered by a Polish powerplant: the 298kW PZL-Rzeszow GTD-350 turboshaft. This engine powers the Mi-2 helicopter, manufactured under licence by Swidnik since 1964. It was a turbulent decade for Poland, and the project kept being delayed. A full-size mock-up of the helicopter was produced in 1987, but this bore little resemblance to the SW-4 as it is now.
A major redesign took place in 1989-90, under new design team leader Krzysztof Bzowka. The Polish engine was considered outdated, and would have had little appeal in the West. Instead, Bzowka selected the 335kW (450shp), US-built Allison 250-C20R. The Allison engine is 60kg lighter and offers 13% more power with 30% lower fuel consumption than that of the GTD-350.
The redesign incorporated the US engine into a more streamlined airframe with a longer, wider, fuselage and modified tail unit. For safety reasons the main rotor was located higher above the ground.
The helicopter has a classical rotor system with a conventional three-blade main rotor 9m in diameter, and a two-blade tail rotor. All rotor blades are made of glass fibre/epoxy composite. The airframe is about 20% glass and carbonfibre composite.
The helicopter has a sliding door either side of the fuselage, and hinged doors forward of these. There is a 1.05m3 luggage compartment aft of the cabin.
The 500litre fuel tank is under the main gearbox, giving the helicopter a 900km range and 5.5h endurance. The gearbox, built with engine manufacturer PZL-Rzeszow, is designed for 30min operation after loss of oil.
Swidnik chief helicopter engineer Jerzy Klimkowski modestly describes the predicted performance of the SW-4 as "not too bad". The company expects the helicopter to have a maximum take-off weight of 1,700kg, carrying four passengers or 400kg internally, or 600kg externally.
It is expected to achieve a maximum speed of 155kt (290km/h) and a 20,000ft (7,000m) ceiling, with a maximum climb rate of 2,170ft/min (11m/s). The helicopter is fitted with an AlliedSignal Bendix/King avionics suite, with the option of equipment allowing operations under instrument flight rules. The aircraft is to be able to operate in temperatures from -40¼C to 50¼C.
The prototype is fitted with provisional landing skids, which are 15kg heavier than is hoped for in the production version. The first skid design was found to be too stiff, with insufficient energy absorption.
Production standard landing gear, capable of absorbing impacts at 610ft/min (3.1m/s), should already be fitted to the next flying prototype, says Klimkowski.
The project received a financial boost in November 1991 with the signature of a five-year contract with the KBN, the state research committee, which has funded about one-fifth of the Pzl20.25 million programme cost since then. Swidnik now needs more financial backing to finish flight testing and certification to US Federal Aviation Regulations Part 27 standards, says research and development director Ryszard Kochanowski.
Talks are under way with the KBN to secure this financing, but Swidnik officials were disappointed that no KBN representatives turned up to the public presentation of the helicopter.
Swidnik has been considering offering the SW-4 in a high-performance version with an alternative Pratt & Whitney Canada power plant. According to Kochanowski, however, plans to fit the 460kW PW200/9 engine will be kept on hold for now, while development of the Allison-powered variant is given priority.
Plans are also afoot for a twin-engined variant of the helicopter. This would be needed to meet forthcoming European regulations limiting single-engined operations, says Kochanowski.
PRICE ADVANTAGE
A twin would be more expensive, however, with the two engines alone costing about $400,000, while the company is hoping to offer the basic helicopter to the market at about $600,000. This would give it a substantial price advantage over comparable rivals.
Swidnik also hopes eventually to be able to offer a Eurocopter-style bearingless main rotor, now under development at the Polish plant, and more advanced avionics packages.
Applications, which are being considered for the SW-4, include general-aviation, border-patrol and police duties, as well as emergency medical services (EMS). The EMS version of the aircraft would be able to accommodate one pilot, one medical attendant and a stretcher. Kochanowski believes that the aircraft could become a basic military trainer and light-combat support vehicle.
During a visit to Swidnik in August Polish interior minister Zbigniew Siemiatkowski hinted at a possible order for five SW-4s for anti-terrorist units. The company believes that it could sell its first aircraft towards the end of 1998 after a two-year certification programme. Demand is estimated at about 40 to 60 helicopters a year.
Swidnik envisages the SW-4 as filling out the lighter end of its family of products. It provides a smaller stablemate for the Kania ("Kittyhawk" - an improvement on the old Mi-2 airframe), with its 3,550kg maximum take-off weight, and the Sokol ("Falcon"), weighing in at a maximum 6,400kg.
There are dozens of proposed names for the SW-4, but Swidnik is keeping them under wraps for now. Although it has taken a long time coming and there are still hurdles to be overcome, this new helicopter is seen as a further indicator that, despite the loss of the once-lucrative Soviet market, helicopter manufacture does have a future in Poland.
Source: Flight International
