Transcript
SA Flyer magazine
(March 2006 issue)
Corrected and updated 2008
Flight test and technical report of Aerokopter’s AK1-3 SANKA helicopter. After my initial visit to Aerokopter in June 2005 to test fly their pre-production helicopter, I revisited the plant again with Mr. George Snyman of Nelspriut in late November to view and fly one of the first helicopters off the production-line. George, a seasoned helicopter pilot with many flying hours is also a qualified helicopter technician and was looking for a replacement helicopter after selling his beautifully finished Rotorway 162F. George has also previously owned a four place Hiller, R44 and Hughes 300 C. I found the Ukraine a country of contrasts. Observing the farmland over France and Germany, the patchwork of small farms looks like a quilt in stark contrast to the enormous farm fields of the Ukraine. Where the Europeans would measure in hectares the Ukrainians would measure in square kilometers. Arriving at Kiev, the capital city’s Borispil airport, which is about the size of Durban airport, I caught a connecting flight to the city of Kharkov in east Ukraine. (Due to a last minute visa problem, George only arrived two days after me.) This city of some 2 million inhabitants has a very small airport. The small passenger terminal building, which I had completely missed on my first trip, is only used for departure. Arriving passengers walk off the plane, collect their luggage from a hand pushed trolley, walk through a steel door in the “airport” perimeter wall and into the parking lot, where I met my contact and interpreter Mr. Alex Miroshnichenko. The roads in and around Kharkov are not in a very good state but the many public gardens in the city center are very nice and meticulously kept. It is true, the women in Ukraine are mostly very beautiful, and no, I had not been away from home long. The people are very polite and friendly and there are many new opportunities opening up in that country for bold entrepreneurs. The worst part of Ukraine for me was my inability to speak or understand Ukrainian or Russian and to top it all, their Cyrillic alphabet is different to ours. Later, when returning via Germany I already felt I could half understand German just because I could read it, even though I don’t understand German either. The Aerokopter factory is located in Poltava some 130 km from Kharkov. This town of some 300,000 inhabitants looked rather depressing and run down, made worse by grey skies and rain when I arrived. The Aerokopter factory is situated in a narrow suburban street and these streets have not seen road maintenance by the impoverished local council since they were built a long time ago. I. E. large potholes every where. There were no road name signs or traffic signs visible, so an English speaking tourist with a road map would have no chance of finding their way. The factory itself consists of several separate old looking warehouse type buildings in different stages of renovation, around a large open yard. My thoughts on arrival at Aerokopter the first time were, “Why have we stopped here? They couldn’t be building any helicopters here!” Well they were! Stepping inside the first building through a solid steel door, and up narrow concrete stairs we were led to the managing director’s office and introduced to Igor Polituchiy, himself a helicopter pilot and major shareholder of Aerokopter. With introductions and pleasantries done via Alex translating, Alex and I then started on my tour of the factory. Inside, the various areas containing the different manufacturing departments were in stark contrast to the dreary outside. With building renovations still underway, most rooms had been completed and were clean, bright, and very neat inside. This same contrast we experienced at the flats that George and I stayed in during our visit. Old and decrepit on the outside, but superb and modern inside. A strange type of property sectional title exists, where the state still owned the building structure and common areas, but the individual flats were owned privately. The design office is equipped with numerous PC’s and the staff were busy manipulating drawings on CAD type software. A small demonstration by one operator showed a complete helicopter on the screen, then removing pieces on the PC and zooming in, till we were down to minute detailing on one selected part deep inside the helicopter. Quite amazing to see! But that was only the beginning. Each of the components that would require machining in their manufacture is linked to further software that calculates and plots the tool paths of some of the various machining centers in the machine shop. These
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computer numeric controlled (CNC) machines then physically cut the 2 or 3D shapes out of the various solid materials. This Computer Aided Machining (CAM) is a modern high tech manufacturing strategy that has allowed relatively quick development of the helicopter allowing for rapid implementation of design changes and quick manufacturing of new parts. This type of manufacturing infrastructure is not usually cheap to set up, but allows a consistently high quality of machining to within very small tolerances. Aerokopter have utilized this strategy to the maximum by machining hundreds of different components from solid billet raw material. The quality of fit and finish of all these components is outstanding! There are no castings used in the production of the Ak1-3 Sanka, even the large main rotor gearbox casings are machined from solid bars of aluminium alloy.
Clearly, Aerokopter had focused their limited capital resources in the right areas of the business to develop an excellent quality product and chose good manufacturing capabilities rather than glitzy offices to start with. The brightly lit machine shop itself occupied the largest space of the entire plant which currently occupies over 1200 square meters and growing. The selection of different types of machining centers although relatively old is enough to make a toolmaker’s heart fill with joy and some two thirds of the helicopters components are manufactured in house. The small welding department is dominated by a robust looking welding jig in which an air frame was in the process of being welded. The quality of the welding is superb. The exhaust system, lower skid leg attachments as well as the Titanium-tube seat frames are welded here. The small air frame is made from chrome alloy tubing and is triangulated in design for maximum rigidity. The Skid legs are made of 51mm Titanium tubing and are attached to the air frame by semi circular clamps with a rubber bush insulators. The lower skid foot then holds the 60 mm diameter Duralumin skids to the Titanium legs. The blade making department had several long blade moulds in various stages of rotor blade production. The composite main rotor blades are constructed from three main elements. First a rectangular shaped spar is created from composites. This spar is then cured in its electrically heated mould. This high tensile spar is then placed into the blade mould where shaped lead weights are placed along the outboard front leading edge together with Rohacell foam trailing edge inserts. This whole assembly is then skinned in composite material and cured. Stainless steel bushes at attachment points and the leading edge wear strip is applied once the blades have been cleaned and painted. The tail rotor blades are also made of composite material and Rohacell foam. Each main rotor blade has a non linear twist of 9.5º and a variable profile and thickness along its length. The quality of finish was excellent. These blades have no life limit and are only replaced on condition.
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The Instrument pedestal, tailboom, horizontal and vertical stabilizers was assembled in the sheet metal room. The tailboom assembly including the stabilizers is made of formed and riveted sheet metal sections and during construction a large assembly jig is used for proper alignment of all parts. Inside the tailboom are 3 x CNC machined internal ribs, equally spaced to carry the tail rotor shaft support bearings. Even the internal ribs for the stabilizers have been CNC machined from solid aluminium and all rivets are solid, no pop rivets. Only close up photos will do justice and show the overall quality of this tail section.
The cabin structure including door frames are made from a composite material. The composite fuel tank is made from sections bonded together. It incorporates brass fittings for the fuel filler cap, fuel drain valves on each side and the fuel level sensor attachment point. The cabin floor is unusual and consists of
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two components, a 16mm plywood and foam floor and supported by a triangulated aluminium sub-frame below, that attaches to the steel airframe. The cabin floor is made by machining out different sized squares from the plywood so as to leave a light wooden grid to which other parts will be bolted to. All the machined out wooden areas are then filled with foam inserts to replace the wood removed. Then a skin of composite cloth is applied to both sides. The result is a very light and riged floor with the wooden grid matching the aluminium frame below where they are joined. The gearboxes and swash plate are assembled in a clean room that also stores the components for their assembly. The heavy duty drive line components are out sourced from specialist aeronautical manufacturing companies. These include the steel alloy rotor head components, Main rotor blade holders, Main and tail rotor transmission gear sets, V-belt reduction drive shafts, sprag clutch and main and tail rotor shafts. Each of these components had serial numbered tags attached to them with component documentation, which I presume was a necessity for obtaining type certification in the Ukraine. The heavy duty hardened and precision ground steel spiral beveled gear sets are very beefy indeed and would do proud inside a large truck differential. From my intuitive mechanical perception, it appeared that all the propulsion driveline components looked over-engineered and should last a very long time. Both main and tail rotor transmissions have a large oil level sight glass and magnetic screw plugs (not chip detectors). The main transmission also has a temperature sensor.
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Another interesting aspect of the Main rotor transmission and pulley reduction drive system, is that it does double duty as part of the airframe structure, thus reducing the actual airframe size and weight. This concept is used very successfully on motorcycles and in Formulae-1 where the engine and gearbox forms part of the frame. While the largest and main assembly hangar was still being renovated, a smaller “show room” stored the complete and painted subassemblies and doubled as an assembly area. Here, there was an unpainted assembled sample of the flight control system that I could inspect in detail. The amount of detailed machining of the control system is amazing. Even the most mundane little re-enforcing brackets used in this assembly are CNC machined from solid stock, including all bolts made of Titanium. Overall the controls look robust and every part that moves or rotates is fitted with sealed bearings and locked with either castle nuts and split pins or safety wired where needed. There are adjustable frictions for both cyclic and collective controls. The Collective lever has an interesting mechanical mechanism below the floor that keeps the lever in the down position via a spring loaded override arm, but when you lift it a few centimeters up, it becomes light and with a little friction applied will remain in what ever position you leave it in, but still easily moved if need be, thus making longer flights less tiresome on your left arm. It had stopped raining by now and Alex called me out to the yard where the demonstration helicopter with Victor Tomilin the pilot and company director was waiting for me. The demonstration helicopter is the second prototype and their pre-production craft . This helicopter was being used for type certification and has been flying for two years. This demo craft had additional measuring equipment installed on board to measure control inputs and loading. It also had its vertical and horizontal stabilizers removed and in its mounting point a control measuring devise was fitted. The production helicopter was will little changed mechanically from this demonstrator, testament to good design know how by getting it right first time. The result is a helicopter with a empty weight of 410 kg. Approaching the helicopter from thirty meters away there was no sound, yet the rotors were turning and I thought the engine had been switched off, but as I approached, I realized it was idling very quietly. With Victor as instructor and pilot in command in the left seat, I climbed in on the right. Getting into most small helicopters is usually a bit awkward and the AK1-3 Sanka was no different to a Schweitzer / Hughes 269C. There is a beautifully machined Duralumin foot peg on each front skid leg to ease climbing in. The trick is to first place your butt on the seat, then swivel your legs in with one leg swinging over the cyclic control. Whew! Relative size of cabin
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Plenty of head and elbow room.
Very similar to Schweitzer 269C The cabin is very spacious and the width at the elbows is similar to that of the Schweitzer 269C at 1353 mm. I am 1.81 meters tall and there was still a good 100mm headroom clearance with me seated. The aluminium anti torque foot pedals were positioned just right for me. The pedals are not adjustable for reach, but the seats can be adjusted to three positions by unfastening and refastening the four the holddown bolts. The pedals, collective and cyclic controls are virtually the same as on the Schweitzer. The instrument consul holds three separate panels one above the other at varying angles going down. There is enough space for a good panel layout spread over these separate panels, including radio, transponder(if required), switches and the like. The cabin interior is smart and neat, with colourcoordinated comfortable seats with four point harness’s. The top instrument panel was fitted with, 10 warning lights, an altimeter, vertical and airspeed indicator (VSI &ASI), artificial horizon, a blade pitch indicator, balance ball and a rotor and engine rpm gauge. There was no manifold air pressure (MAP)
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gauge, but this will be fitted into the blank space provided for SA models. The rotor and engine rpm gauge was very unusual and I was very skeptical when I first saw it. It consisted of two parallel vertical columns of different coloured lights, one column for rotor rpm and the other for engine rpm. Each column had three lower red lights, three amber, six green, three amber and three upper red lights. The individual lights lit up indicating the respective rpm’s and move up and down the column as rpm’s increase or decrease. Beam me up Scotty! Incredibly, they were very effective in use and I would not change them for the more conventional instruments. The green light was easily visible out of the corner of your eye while flying. The rotor rpm lights are driven via a magnetic pick-up mounted on the front end of the tail rotor drive shaft and is independent of any external electrical power source. The blade pitch gauge which consists of a horizontal row of coloured lights, I never got to interpret or understand properly in the time that I flew. The rest of the panels housed the switches, engine oil and water temperature gauges, fuel gauge, Microair 760 radio/com and the cabin heat and ventilation control system. The cabin heat system will be left out for S.A. thus saving 7 kg of weight and replaced with circular vents in the doors. The final layout of the central panel was still to be finalised for S.A. at the time of my visit. Buckled up and engine warm it was time to lift off and try this craft. I did not check the elevation at Poltava, but the whole country is very flat and below 500 ft according to my world atlas. The outside air temp was 17 C and it had started to rain lightly again. With me following on the controls, Victor brought up the rotor rpm to the middle of the “green” (lights) and then slowly raised the collective without seeming to make further throttle adjustments, lifting into the hover and using a fair amount of right pedal to hold our heading. The helicopter in the hover is pretty smooth and confidence inspiring. Victor then performed rapid pedal turns to the left, then right to demonstrate tail rotor authority, which was impressive in both directions. I have flown the last 380 + hours in my CH-7 Kompress kit helicopter and have become used to its very sensitive pedals, where you only have to think about a turn and that is sufficient pedal movement, so here I had to quickly readjust to the longer pedal travel as in the Schweitzer that I had done my training in. Next we lifted to approximately 30 feet and Victor performed tight fast circuits in the yard between the buildings – backwards! Then back down to the hover and a power climb out of the yard and over the suburban houses at 300 ft heading towards the open farmland nearby. They don’t seem to have the same rules of the air as we do and height above built up areas does not seem to apply there. The only rule that we stuck religiously to was a maximum height restriction of 1000 ft (300m) above ground level imposed by the military airfield situated close by. Clear of houses Victor handed over control and I immediately started drifting to the left and porpoising slightly. Gee this was difficult to fly! I can’t be so bad at flying? After a couple of minutes I had it figured out and readjusted my brain to the clockwise rotating rotors. Thereafter, straight and level flight at varying speeds was easy to maintain even without any stabilizers fitted. The helicopter seemed to slip through the air easily and was very comfortable and smooth at its 85 knot cruising speed. I then handed back to Victor to take it to maximum level flight speed and 102 knot Vne, which he duly performed with no fuss at all. I then tried the same and it was no problem getting to 100 knots. There was no shaking or increased vibration and it did not feel like we were pushing the machine at all, in fact the only indicators were more collective and more forward cyclic stick. I did start to miss the MAP gauge at this point as I had no sense of power measurement. Then slowing down again to different speeds, I tried to fathom what the blade pitch indicator was telling me, but I gave up after a while. Next I gently lowered collective and started a long approach for a landing on a field, slowly reducing airspeed until we came to a hover. The pre-production helicopter had no governor but the correlation between collective and throttle is good and needs very little pilot adjustment to keep the rpm’s in the wide green band. The production helicopters have the option of a governor, utilising the Subaru “cruise-control” system. This is turned on and off by a push-button and the rotor/engine rpm can be adjusted up or down via a coolie-hat switch, both of which are mounted on the cyclic stick grip and easy to use. My first hover with the Sanka was no problem, but I still had to get used to the right pedal forward travel required to hold our heading. Next I performed some square bashing exercise, hovering sideways forwards, backwards with some spot turns thrown in and although my sideways flight was a little wobbly I have no doubt that with a couple of hours on the machine I would get it significantly better. After several minutes of witnessing this feeble performance, Victor took control and again performed some more demanding maneuvers to demonstrate its true abilities. First side ways flight in a circular pattern using a point approx 5 meters ahead as the center, at ever increasing speed while simultaneously gaining
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a nose down attitude, then using the tail rotor as the center we rotated with a nose up attitude, some more high speed backwards flight and followed by pirouette turns down the field. OK, I was not going to try all that but it could be done by some one with only 3000 thousand hours experience! After some 10 minutes of hover exercises, I checked the gearbox and engine temperatures and noted that they were still nice and cool, bearing in mind that it had been raining all this time. Next I performed a few short circuits around this large field with landings and take offs to assimilate myself more with the helicopter behavior and control coordination. There is no carburetor-heat to worry about, as the engine is fuel injected. Happy with that, I then checked the rate of climb with two 80 kg persons and approx 35 kg (2/3rd’s) fuel remaining. From the hover I moved forward to the best rate of climb speed of 45 knots and started the climb with an eye on the VSI, slowly pulling collective up. Without the MAP I was unaware how far I could pull up before the rotor rpm would start to decay, but at approx 1,300ft/min (6.5m/s) Victor intervened and pulled the collective up till the VSI indicated just over 9 m/s (1800 ft/m) with no sign of rotor rpm decay or able to determine if we were at full power. It was all over in a few seconds as we quickly reached the 300 m ceiling. Wow! Very impressive! I estimate that we were some 45kg below the maximum “normal” gross weight of 650 kg, so the maximum rate of climb of 8.2 m/s (1600 ft/min) quoted in the performance graphs seems achievable. I say “normal” because the Sanka is designed to operate at a higher gross weight of 740 kg with the optional crop spraying option installed. This optional equipment is still undergoing durability field trails, but when installed, is positioned so as to maintain the helicopters center of gravity within limits. Now at 1,000 ft above ground, Victor demonstrated an autorotation at its lowest rate of decent speed of 45 knots with the “lights” split (engine at idle). I followed on the controls and monitored the rate of decent at 9 m/s (1800 ft/min) on the VSI, while Victor adjusted the collective to maintain rotor rpm in the green, then ending with a short flare and power recovery. Certainly good enough to get you to the ground safely in the event of an engine failure. Next was a slope landing near a river bank and this was done with no problem. The cyclic control on the Sanka has about the same sensitivity as R22 that I remember from the distant past. During forward flight the cyclic stick forces remain very light and I suffered no fatigue to my right arm during this 35 minute test flight. There is no cyclic trim adjustment on the Sanka, and only on much longer flights would one be able to determine if a lateral trim was necessary. I did check for the possibility of eventually fitting an electric trim system myself afterwards and this seemed a fairly simple add-on and there was plenty of space below for its installation. The rain really started pelting down now and the last exercise I wanted to perform before heading back was an accurate spot landing as for trailer landings. I selected a narrow dirt track ahead with a pothole as a marker and without difficulty landed nicely on the selected spot. After 30 minutes of flying this craft I would have very confidently landed it on my helicopter trailer back home. After a five minute flight back ending with a steep decent into the factory yard, Victor switched off the engine without a cooling down period as engine temperature was cool already, then disengaged the clutch which takes approximately one minute. There is no rotor brake on the Sanka so it takes a while for the rotors to stop completely. Like a small boy exited after a ride on a new toy, I realized I had discovered a gem! I had to have one of these. The next day I toured the central city streets of Kharkov on foot to get a better snapshot of daily life in the Ukraine and to allow the previous days excitement to settle. The following day I had planned a second test flight to verify that that my first flight assessment was not distorted by my own excitement. Bright sunshine greeted us the next morning and this time I was to fly with company test pilot Nickolay Morgoon with some 12,000 + flight hours. Start procedure was straight forward with master and ingnition switches on, a press on the push-button starter situated on the cyclic grip, and the water cooled EJ 2.5 Subaru fired up instantly. No priming, choking or fiddling with mixture levers required. Why can’t they make certified aircraft engines that start as easily? Clutch switch on and within a few seconds the rotors started to turn. The electric clutch tensioning devise is robust looking and tensions the primary reduction pulley V-belts to a pre set tension. The demonstrator Sanka had 7 narrow standard cord Vbelts, but production units have 6 broader Kevlar reinforced V-belts with much longer times between replacements. It took about 3 to 4 minutes to warn up the engine, then we lifted off to perform a hovering autorotation so as to check rotor blade inertia. At about 5 to 6 feet skid height Nickolay chopped the throttle and we settled down with a solid thump that I think would have splayed the skid legs on my Kompress, but with no apparent harm to this helicopter. I would rate the inertia in the disc on the light-ish side. No hovering
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for 3 + seconds available here! Heading out towards the open farm lands again I took control and performed some steep turns left and right with out excessive vibration or shaking. I had not been imagining, this helicopter was indeed smooth. Down to the hover, I tested engine recovery from low rotor rpm and intentionally allowed the rpm to drop to the low amber lights then twisted the throttle and the response was an immediate rotor rpm recovery! The smooth free spinning Subaru engine had plenty of spare power and in the hover was quieter than the R22 and Schweitzer when standing outside as an observer. The rotor rpm green band is from 505 to 565 rpm and the amber bands increase this from 465 to 600 rpm. After 30 more minutes of various flight maneuvers, I had reassured myself of my first assessment and we headed back. I had not imagined it, it was indeed a nice helicopter. Four-up at 750 kg gross weight on a cold winter day!
The rotor head needs special mention as it is a very unusual design for such a small light weight helicopter. I had not seen a Laminated Blade Retention System before and have since discovered that it is also used on the Apache Longbow attack helicopter which I saw at the Paris air show. I have also been told that this system is used on the Russian Black Shark attack helicopter and on some Mc Donald Douglas helicopter models. The system principal and structural elements are very simple, but the mathematical number crunching to determine the shape thickness and material of the metal laminates is very complex and high tech. The Sanka’s main rotor system is comprised of three torsion bars, each made from a stack of special steel plates. These torsion bars are flexible up and down, can twist easily and replace the more conventional but bulky and heavy lead-lag, flapping and feathering hinges. The best comparison is a stack of engine feeler gauges that also bend and twist easily. The torsion bars connect the blade grips to the rotor hub. The major advantages are mechanical simplicity, massive weight savings, ease of inspection and no maintenance servicing. These torsion bars are non-serviceable items and are replaced “ON condition”. To reduce weight, the large diameter blade pitch torque-tubes are made of composite material and have two large inspection holes on each side for easy pre flight checks of the torsion bars. The replacement of these torsion bars does not appear very difficult to perform.
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The three blades can be removed or installed in less than 5 minutes with two persons. I witnessed this myself. The Sanka is ideal for towing behind a car on a light trailer with its blades removed, as was demonstrated to me on a 450 km drive to the Kiev air show with a small 1.2 L car towing on not very smooth roads. Servicing of the engine is very simple indeed, as all items are exposed and easily accessible. Even the engine is very easily removed for overhaul, as there are only three engine mount bolts to remove, the flexible coupling, radiator hoses and a couple of wires to disconnect and out it comes. Airframe servicing too is relatively simple, again as all items are very easily accessible. So how does Aerokopter’s Sanka compare against the popular light piston engine helicopter competition? I have compiled a comparative table from information available. I was unable to verify the actual IGE and OGE hover performance due to the 1000’ ceiling restriction imposed. I therefore quote the Sanka’s and the competitors hover performance from their respective flight characteristics performance graphs. Updated graph- 2008 Seats Passenger payload kg Cabin width m Operating weight kg Empty weight kg Standard Fuel load kg (L) Max. level speed at SL. Knots Cruise speed knots Vne knots
RotorWay 162F 2 180 1,100 682 454 48 (64) 100 83 100
R22 Beta II 2 181 1,100 622 388 53 (72) 102 96 102
Schweitzer 300CB 2 211 1295 795 495 89 (121) 84 80 94
Sanka AK1-3 2 186 1,353 650 410 53 (72) 97 85 97
Schweitzer 300C 3 271 1,295 865 510 84 (114) 84 80 100
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Max. range km Max. rate of climb at SL ft/min OGE hover ceiling IGE hover ceiling Engine power (Standard) Kg / hp at sea level with two 90 kg persons and full fuel
290 1000 5000 7000 150
330 1000+ 6500 9500 131**
354 1250 4800 7000 180
320 1600 5000 7000 156
375 990 5400 7900 190
4.55
4.73
4.23
4.16
4.07
Only founded in 1999, Aerokopter is a young company that has just recently completed the development of the Sanka helicopter and is now undergoing the long bureaucratic process of getting type certification in the Ukraine. It appears that in the Ukraine, type certification for a complete aircraft can be obtained with its installed engine, unlike many western counties where the engine has to be type certified separately. Therefore the AK1-3 Sanka with the non-type certified Japanese manufactured Subaru petrol engine will be imported to S.A. as a “factory built kit helicopter” under the ZU registration. The advantages with ZU registered aircraft is that you are allowed to service and maintain the helicopter yourself if you wish, to keep operating costs down. The down side is that you may not use it commercially for carrying fare paying passengers. The Sanka has no calendar time limit before overhaul and will not have to be shipped back to the manufacturer for an overhaul after 2,000 flight hours, as this can be done by our local approved maintenance organizations (AMO). Because the helicopter is still a new aircraft, there is as yet insufficient history to calculate accurately the direct operating costs over a long period. Pilot-production of 5 helicopters started in 2005 for first delivery to Ukraine customers. Production for 2006 is set at only 10 helicopters, of which five are destined for S.A. After assembly, each helicopter is test flown for a couple of hours to ensure that all is working properly before delivery to client. Aerokopter currently do not accept payment via letters of credit, as they literally use client pre-payments to manufacture their client’s helicopter. The factory offers a 1 year or 100 hour guarantee on airframe parts only. And what did George think about this helicopter? “Wunderbar”! He has ordered a yellow one! Black machine about to start up for a demo with client. …..Nice weather!
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A red helicopter about to be shipped to a lucky customer.
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