Brian Homewood/BOGOTA
AFTER TEN YEARS of development, Colombia's first indigenous aircraft is poised to enter production. The second prototype of the El Gavilan 358 (the Sparrowhawk) was due to have its maiden flight in the USA on 4 March, and the manufacturer expects that certification, under rigorous US Federal Aviation Administration regulations, will be completed in July.
Major structural checks on the aircraft, including tests to ultimate loads on the fuselage, landing gear and wings, have been carried out, and the production plant is nearing completion at Guaymaral Airport, which lies just beyond Bogota. The plant will employ 200 people and will produce four aircraft a month, with the first deliveries planned for September.
The Gavilan is a high-wing, single-engined, utility aircraft, which can carry eight people or be adapted to transport cargo. It has been developed by the Leaver group, which set up a new company, El Gavilan, to undertake the project. Reflecting conditions found in its native country, the aircraft is designed to be robust, versatile and able to be operated from short and unprepared remote airstrips. In other words, its most potent market is among small commercial operators in remote regions.
WORKHORSE
"It is not a leisure aircraft," says managing director Eric Leaver. "It could be used, by fisherman and hunters in the wilds of Canada or in the Australian outback, or in Brazil, for example. To begin with, we are concentrating on the Latin American market."
Leaver says that the aircraft's future is heavily dependent on selling an initial batch of ten aircraft to the Colombian air force, which has expressed a strong interest in the project. "We have a fairly firm commitment - I wish I could say letter of intent - from the air force and I am very confident that the order will materialise," he says.
Originally, it had been planned to start deliveries in late 1993, but the first prototype crashed during a test flight. The accident was attributed to a snapped crankshaft, which was eventually traced back to an error by the manufacturer of the engine. Leaver says that the aircraft had undergone 174h flying before the accident.
The project could only be restarted once the US National Transportation Safety Board inquiry had been completed. New financing was obtained from Inter-American Investment, the merchant-banking arm of the Inter-American Development Bank, and the Institute de Fomento Industrial, a development body owned by the Colombian Government. Both are providing long-term loans and equity investments. "The crash set us back about three years," Leaver says.
Now, the second prototype has been built and the manufacturer, which was originally targeting Colombian certification, is now aiming to have the aircraft certificated under the stringent US Federal Aviation Regulations (FAR) Part 23 amendment 45 rules. Leaver believes that around 250 flying hours will be necessary for certification. The process will take place at Lochhaven in Pennsylvania.
"Being the builder of a Colombian aircraft, we have to get over a big credibility gap," says Leaver. "An FAA certificate would remove any doubts there might be about the aircraft. Amendment 45 is a very, very complete test and we would be only the third manufacturer to meet the requirements." Leaver says that most aircraft in the same category were certificated in the 1960s under earlier US Civil Airworthiness Regulations 3 rules.
Among the most important requirements for FAR 23 certification is the need for crew seats, to withstand 19G and the passenger seats 16G, without hurting the occupants' backs, although the Gavilan's seats will be tested to 21G. FAR 23 also, demands lightning proof fuel systems, non-siphoning fuel caps and dual actuating rods on trim systems.
The Leaver Group has its roots in Aeromercantil, which was set up in 1952 to market Piper aircraft in Colombia. Sixteen years later, it began buying Piper kits to assemble in the country as a way of avoiding regulations on the import of foreign-aircraft parts.
The Group now operates five companies, employing around 300 people, who are involved principally in sales, maintenance and repairs to light aircraft. It also runs a flying school and occupies a 30,000m2 (323,000ft2) site at Guaymaral.
The El Gavilan 358 was conceived ten years ago because of uncertainty in the US aviation industry, which Leaver believed, could affect deliveries to South America. "We weren't sure what was going to happen to Piper and we decided we should develop our own aircraft. If I had known then what I know now, I might not have attempted it."
SIMPLE AND ROBUST AIRCRAFT
Leaver approached General Aviation Technical Services (GATS) at Lochhaven with a proposal to produce a single-engined aircraft, which could be flown in difficult conditions. The result was the El Gavilan 358.
It is designed to be simple and robust. The rectangular cabin has a flat floor, which allows it to be adapted for a variety of missions, and means that it can satisfy the demands of commercial operators which specialise in carrying passengers or cargo mail or offer logistical support. Aerial photography could be another application.
The seats can be removed and, because of its shape, the aircraft can carry awkward objects such as plywood, or even a full-size US coffin. It has three doors, two for each of the forward occupants and a large double cargo door on the left-hand side of the fuselage. The aircraft can also be adapted for use as an air ambulance, carrying four stretchers, and can be flown with the doors removed to allow it to be used for parachuting. Its centre of gravity has a wide margin of travel to ensure flexibility in loading.
The structure of the fuselage is a rugged tubular-steel truss, covered by aluminum sheet. Leaver says that, although this is not common, such frames are easily repaired and Aero Mercantil had construction experience from assembling Piper kits. The wings are constructed of aluminum and use two spars and an external strut for support. The tail surfaces are also built of aluminum and attach directly on to the steel fuselage.
Runways in Colombia have a reputation for knocking off the landing gear of similar aircraft, such as the Cessna 206, and so stronger landing gear was one of Leaver's demands when GATS presented its design.
The gear now has a tricycle configuration, with the nose-wheel using a trailing-link arrangement for operation on rough runways. It is freely castoring to make the aircraft manoeuvrable on the ground. GATS has also chosen to use elastomers in the design - these are small, hard-rubber discs which are stacked in a cylinder and compress on impact and then reform slowly rather than rebounding. This creates a gear, which will not bounce. The discs, made of Keoprene, have been nicknamed Gummy Bears after the jelly sweets sold in the USA.
Easy maintenance is another priority, and the Gavilan incorporates many features to assist servicing, such as readily accessible electrical systems and a hinged instrument panel, which permits any instrument to be easily changed.
Leaver says that the second prototype is, basically identical to the first, with no major structural changes having been made, although some of the specifications are different. The original 12V electrical system has been replaced with a 24V system because of the difficulties with the 12V system in cold weather. "We had trouble starting the engine with 12V," says Leaver.
He says that the possibility of fitting a turbine engine in the future is being seriously considered. "We are planning to do this as soon as we have got a few sales under our belts," he adds.
As before, the Gavilan will be certificated with a 260kW (350hp) Textron Lycoming TIO-540-W7A turbo charged piston engine, the -540 version being needed because of the high altitude of many Colombian airstrips. The -720 version may be offered outside Colombia. A Harzell three-blade propeller is used.
Fuel capacity is 454litres and the aircraft's range, with 30min reserve and 75% power, is 1,425km (770nm), compared to 1,120km with the original Gavilan. Maximum cruising speed is 145kt (268km/h), as before. Take-off distance is 310m (1,000ft), compared to the original 275m, while landing distance is unchanged at 200m. Fuelling is over-wing, and the fuel is gravity-fed to a collector tank beneath the cabin floor, then pressure-fed to the engine.
WING CONSTITUENTS
The wing has a NACA 4412 aerofoil, with constant chord and no taper and provides a high lift-coefficient in the climb. Large flaps are hinged at the 30% chord point to avoid creating pitch or trim changes during extension or retraction. Flaps can be selected to 15¡, 30¡ or 45¡.
Leaver says that the basic version of the Gavilan will now sell for $296,000 (the price had previously been announced as $320,000). The price includes a full set of gyro-based instruments, exterior and interior lights, a VHF radio and a choice of a VOR or a global-positioning system.
Source: Flight International
