Unit I. Helicopter Design
Exercise 1. Read and translate text 1.
Text 1. Rotary wing aircraft
The helicopter is a flying machine, a rotorcraft, heavier than air, deriving both lift and control from one or several horizontal rotors (power-driven rotors) and is capable of vertical take-off and landing. The rotary wing aircraft made to fly by fast-turning metal blades, or rotors can land in a small space, take off without running along the ground, and stay still, or hover, in the air. The simplest helicopter consists of a rotor system, a fuselage, a cabin, a cargo compartment, an engine, the undercarriage.
The lift of the helicopter is generated by one or more rotors. Besides its main or lift rotor, the helicopter usually has an auxiliary, or tail rotor. The small rotor is mounted at the tail to counteract the torque of the main rotor. The tail rotor diverts some part of the engine power and lowers the power plant efficiency.
The co-axial rotor system is free from this drawback, but it is not capable of high forward speed because of the drag of the widely separated rotors. Helicopters with coaxial rotors have proved their main advantages – great maneuverability, small size, high payload, and great effectiveness. But high cost of manufacture, heavy fuel consumption, restricted range and speed make the helicopters impractical for long range transportation.
Even the best helicopter makes have an endurance not exceeding 3-4 hours.
Exercise 2. Read and learn the recommended vocabulary to text 1.
Rotorcraft – летательный аппарат с несущим винтом; винтокрылый ЛА
rotary wing aircraft – винтокрылый ЛА
make to fly – удерживать в воздухе
fast-turning metal blades – приводимые в быстрое вращение металлические лопасти
hover – зависать, висеть в воздухе
main / lift rotor – несущий винт вертолета
auxiliary / tail rotor – рулевой / хвостовой винт вертолета
counteract the torque – скомпенсировать аэродинамический крутящий момент
divert – отклонять, отводить
coaxial rotor system – система соосных несущих винтов
drawback – недостаток, изъян
maneuverability – маневренность
heavy fuel consumption – большой расход топлива
restricted range – ограниченная дальность полета
make impractical – делать непригодным
endurance – продолжительность полета
exceed – превышать, быть больше
Exercise 3. Translate word combinations with the terms: “blade”, “rotor”, “helicopter”.
a) rotor blade, helicopter blade, propeller blade, fixed blade, airscrew blade, all-metal blade, main rotor blade, tail rotor blade;
b) helicopter rotor, tail rotor, upper rotor, front rotor, lifting rotor, front main rotor, rear main rotor, dual main rotors, jet-driven rotor, lower coaxial rotor, power-driven rotor, upper coaxial rotor, high-speed rotor, twin-bladed rotor, three-bladed rotor;
c) civil helicopter, land helicopter, sea helicopter, transport helicopter, cargo helicopter, commercial helicopter, search helicopter, ambulance helicopter, mail helicopter, hospital helicopter, fire helicopter, marine helicopter, combat helicopter, training helicopter, research helicopter, reconnaissance helicopter, high-performance helicopter, all-purpose helicopter, agricultural-version helicopter, single-seat helicopter, all-weather helicopter, carrier-based helicopter, flying-crane helicopter.
Exercise 4. Read and translate the following noun clusters.
Hovering helicopter, winged helicopter, multi-rotor helicopter, multiengine(d) helicopter, turboprop helicopter, turboshaft helicopter, coaxial-rotor helicopter, multiengine helicopter, tandem-rotor helicopter, dual-rotor helicopter, folding-rotor helicopter, four-rotor helicopter, hoist-equipped helicopter, hot-cycle helicopter, jet-augmented helicopter, pressure jet helicopter, rocket-boost helicopter, rocket-powered helicopter, shaft-driven helicopter, stub-wing helicopter, tail-rotor helicopter, thrust-assisted helicopter, tip-driven helicopter, turbine-engine(d) helicopter, twin-engine(d) helicopter, twin-rotor helicopter, twin-turbine helicopter, variable stability helicopter, single-engine helicopter, side-by-side rotor helicopter, single main rotor helicopter, four-blade rotor helicopter.
Exercise 5. Memorize the terms referring to the helicopter dimensional data and the main flying characteristics.
Main rotor radius
Main rotor chord
Tail rotor diameter
Tail rotor chord
Landing gear type
Maximum gross weight
Maximum cruise power
Range with payload
Rate of climb
Main rotor diameter …. 32 ft. 0 in.
Tail rotor diameter ……..4 ft. 8 in.
Width, fuselage ………...5 ft. 1 in.
Height ………………….9 ft. 0 in.
Elevator span …………..5 ft. 3 in.
Width, skids ……………7 ft. 4 in.
Main rotor disc area …803.8 sq.ft.
Tail rotor disc area ..…17.34 sq.ft.
Seats, standard ……………2 or 3
Never exceed speed, VNE ..112mph
Maximum level speed …..112mph
Range, maximum ………..263mi.
Rate of climb, sea level ...1150fpm
Service ceiling ……….…12,000ft
Weights and Loading
Gross weight ……………2600 lb.
Empty weight, standard ....1570 lb.
Useful load, standard ……1030 lb.
Disc loading ….……3.23 lb./sq.ft.
Max power loading …11.55lb./hp.
Fuel capacity, total ……….40 gal.
Hover ceiling, IGE@2600pounds...7700ft
Hover ceiling, IGE@2350pounds..13200ft
Hover ceiling, OGE@2350pounds...8700ft
Exercise 6. Memorize the terms which refer to the helicopter (external view).
Main rotor blade – лопасть несущего винта
blade-root attachment – крепление комля лопасти
droop stop – ограничитель свеса (лопасти)
main rotor hub – втулка несущего винта
main rotor mast – колонка несущего винта
jet pipe – реактивная труба
engine – двигатель
horizontal stabilizer – горизонтальный стабилизатор
anti-collision beacon – проблесковый маяк
upper fin – верхний киль
anti-torque tail rotor – хвостовой винт
lower fin – нижний киль
tail boom – хвостовая балка
boarding step – подножка для посадки
transponder aerial – антенна (радио)ответчика
forward hinged door – дверь с передней подвеской
air temperature probe – датчик температуры воздуха
VHF aerial – антенна ОВЧ
baggage compartment – багажная дверь
Exercise 7. Make use of the suggested words and word combinations in order to present the helicopter design.
Rotor blade, flight deck, drive shaft, cabin, rotor head, mast rotor hub, tail boom, antenna, position light, tail fin, exhaust pipe, tail plane, luggage compartment, tail skid, air intake, fuel tank, boarding step, landing light, control stick, landing window.
Exercise 8. Ask questions to all parts of these sentences.
1. Rotary wing aircraft are made to fly by fast-rotating rotors. 2. The helicopter is at its best on short haul trips. 3. Heavy fuel consumption and restricted range make the helicopter impractical for long transportation. 4. The rotor-craft can land in a small place. 5. Any helicopter takes off without running along the ground. 6. The helicopter can stay still, or hover, in the air. 7. The co-axial rotor system is not capable of high forward speed. 8. The rotor blades have lifting aerofoils and are all-composite. 9. The helicopter rotor is a lifting surface. 10. The lessening of vibration, simplification of the controls, improved stability, increased safety and easier maintenance are the problems of the helicopter flight. 11. This helicopter rotor system is the three-blade main and antitorque rotors. 12. The landing gear of the helicopter is non-retractable tricycle type. 13. This helicopter power plant contains the turboshaft engine, fuel in a single tank in the fuselage centre section.
Exercise 9. Read and entitle the text.
A helicopter ability to carry out its mission is directly connected with its equipment. Plans are made to equip helicopters with integrated autopilot / navigation equipment which were primitive on earlier helicopters because of mass constraints became almost the same as in airplanes. Crew workload under bad weather conditions is heavier in a helicopter than in an airplane (instability, low airspeed, hovering). That is why a helicopter needs a very sophisticated autopilot systems. Helicopter and equipment makers developed autopilots that can control the helicopter during all phases of flight including hovering.
The autopilot together with other instruments such as radar, radio altimeter, INS (Initial Navigation system), satellite receiver, etc. give civil helicopters the ability to fly in all weather conditions, except icing conditions. Ice on rotors or engine inlet duct can result in dangerous situations and in a crash. The only helicopter that can fly in icing conditions is super puma.
Exercise 10. Read and learn words and word combinations to text.
Integrated autopilot system – комплексная / встроенная система автопилота
constraint – ограничение
workload – физическая нагрузка (на летчика в полете)
hovering – зависание
radio altimeter – радиовысотомер
initial navigation system (INS) – инерционная навигационная система
satellite receiver – спутниковый приемник
Exercise 11. Select the correct answer for each of the questions.
1. What makes crew workload in bad weather conditions heavier in a helicopter than in an airplane?
a) low altitude;
b) instability, lower airspeed, hovering;
c) uncomfortable cockpit.
2. Which of the following is correct?
a) Helicopter communication and navigation equipment is very primitive.
b) Helicopter makers developed some equipment that enables to control the helicopter during all phases of flight including hovering.
c) Because of low altitude icing is not a problem for helicopters.
3. Which of the following statements is not correct?
a) Instability, low airspeed, hovering make crew workload more difficult than in an airplane.
b) Helicopters need a very sophisticated autopilot system because of instability, low airspeed and hovering.
c) Communication and navigation equipment in a helicopter is less sophisticated than in an airplane.
Exercise 12. Divide text into logical parts and write a topical sentence for each part.
Text. The mechanics of flight
Helicopter flight is achieved by spinning a wing, called the ‘main rotor’, overhead. The engine, whether turbine or reciprocating, is connected to the blades via a transmission and driveshaft. This same engine also drives a small propeller – the ‘tail rotor’ – on the rear of the ship to overcome the torque generated by the main blades overhead.
The speed of both these sets of blades is constrained within narrow parameters, but the pitch of both is controlled through a large range by the pilot. The tail rotor’s pitch is controlled by foot pedals, exactly like the rudder on a plane. Push on the left pedal, and the ship yaws left; push on the right, and the ship yaws right. With the blades spinning overhead, a certain amount of pressure is always going to be required, but when forward speeds reach a certain value, the helicopter will streamline and make the required pressure little or zero.
The pitch of the main rotor blades is controlled by two separate controls. The first, the ‘collective’, is located to the pilot’s left. It is a rod that pivots at the back of the seat. Pulling this rod up increases the pitch of all the main blades the same amount and at the same time. This provides lift and makes the helicopter rise straight up – assuming everything else is in balance. Another stick, the ‘cyclic’, is located between the pilot’s legs and controls the pitch of the main blades at various points around its arc.
This concept is of paramount importance in understanding helicopter flight. It should seem intuitive that the overhead spinning disc would be titled to move the helicopter in non-vertical directions. In other words, to lift the helicopter, you’d increase the pitch of the blades. For example, if the pitch of the main rotor blades was increased as the blades came around the left side and decreased when they went to the right, the disc (and, of course, the helicopter) should tilt to the right and move that way.
That is exactly what the design pioneers thought, so they were perplexed when the helicopter didn’t respond as desired. The problem comes from gyroscopic precession.
The disc overhead is a gigantic gyro wheel. A rotating force applied will result in a movement at 90 degrees to the input. Much as with a two-wheeled vehicle, the lesson is that to turn left, the bike must either be leaned to the left or the handle bars pushed to the right. The former will cause the front wheel to turn in the proper direction, while the latter will cause the bike to lean, or roll, into the turn.
Back to helicopters. Gyroscopic precession is accounted for by moving the point of maximum pitch 90 degrees in advance of the desired direction. If the pilot wants the ship to move forward, he pushes the stick forward. The engineers would have arranged the control rods so they induce an increase in pitch on the left side – assuming it’s an American helicopter with a clockwise direction of rotation when looking up. Doesn’t make much sense? It’s not important; just keep the main rotor speed up and check the disc movement before liftoff.
Exercise 13. Translate into English.
1. Французский виконт Гюстав де Понтон д’Амекур придумал слово «геликоптер», образовав его из двух греческих слов: «Хеликос» - винт, и «птерон» - крыло. «Геликоптором» виконт назвал свою модель вертолета, винты которого приводились в движение паром. 2. Вертолет – это летательный аппарат, тяжелее воздуха, подъемная сила которого создается одним или несколькими горизонтально расположенными винтами, способный производить вертикальный взлет и посадку. 3. В 1475 году Леонардо да Винчи выполнил рисунки «винтовой машины». Маленькую модель с двухвинтовой (соосной) схемой и пружинным приводом успешно испытал Ломоносов в 1754 году. 4. 1907 год считается годом рождения полномасштабного человеческого вертолетостроения. 5. В 1907 году взлетел вертолет конструкции французских братьев-механиков Бреге и профессора Рише на высоту больше метра с «пилотом» на борту. Вертолет Бреге и Рише весом более полутоны поднимался и висел над землей при помощи четырех винтов диаметром восемь метров. 6. В 1908 – 1910 г.г. конструктор Сикорский построил свои первые два вертолета сосной схемы, но ни один из них не смог взлететь. 7. В 1911 году российские ученые Юрьев и Сабинин создали теорию воздушного винта. 8. Первый в мире заказ на военный вертолет получил не Сикорский, а профессор Ботезат в 1921 году от армии США. Профессор Ботезат родился в Росси и защитил докторскую в Сорбонне, до революции 1917 года работал в Петербурге.
Exercise 14. Translate into English.
Cлово «геликоптер» придумал французский виконт Гюстав де Понтон д’Амекур, образовав его из двух греческих слов: «Хеликос» - винт, и «птерон» - крыло. Вертолет – летательный аппарат, тяжелее воздуха, подъемная сила которого создается одним или несколькими горизонтально расположенными винтами, способный производить вертикальный взлет и посадку. Сама идея вертикального полета с помощью пропеллера распространена в природе. Разнообразные «вертолетные модели» сочинялись с давних времен. Маленькую модель с двухвинтовой (соосной) схемой и пружинным приводом успешно испытал Ломоносов в 1754 году. В 1784 году Лонуа и Бьенвеню создали простую двухпропеллерную вертолетную игрушку. 1907 год считается годом рождения вертолетостроения. В 1907 году взлетел вертолет конструкции французских братьев-механиков Бреге и профессора Рише на высоту больше метра с «пилотом» на борту. Вертолет Бреге и Рише весом более полутоны поднимался и висел над землей при помощи четырех винтов диаметром восемь метров. В 1908 – 1910 г.г. конструктор Сикорский построил свои первые два вертолета сосной схемы, но ни один из них не смог взлететь. В 1911 году российские ученые Юрьев и Сабинин создали теорию воздушного винта. Первый в мире заказ на военный вертолет получил профессор Ботезат в 1921 году от армии США. Профессор Ботезат, родившийся в Росси и защитивший докторскую в Сорбонне, до революции 1917 года работал в Петербурге. Только в начале тридцатых годов двадцатого столетия вертолеты начали летать.
Exercise 15. Translate text in writing.
Text. The 280 FX Shark
The Shark is basically a conventional light helicopter with a skid for gear. Two removable wheels allow easy ground handling, although it’s best to have two people do the work. The three main blades are very heavy and thus contribute to the system’s high inertia. The main rotor system is fully articulating, with the blades attached to the head by a retention pin and drag links. The control rods pass inside the tubular mainshaft to the swash plate, which is located inside the fuselage. The tail rotor is a two-blade affair that teeters. Power from the engine is delivered to the transmission via a single, large 30-groove belt.
The engine is a 225-sph Lycoming HIO-360-F1AD flat-four engine with a Rotomaster turbo charger. It is enclosed and mounted horizontally. The standard load of fuel is in two fuel tanks. Each holds 21 gallons, 20 of which are usable. There is an optional 13-gallon auxiliary fuel tank. Power throughout is supplied by a 12-volt, 70-amp alternator.
There is room for three, although the center section of the bench seat is normally removed. Dual controls allow flight from either side, and the doors can be removed for those very hot days. There is a heater for cold weather.
Today’s Shark has more creature comforts with lumbar supports, NASA foam seats, a new tailplane with endplate fins, heavy-duty tail rotor guard, redesigned air inlet system and completely faired landing gear. With the optional auxiliary fuel tank, the helicopter’s range has been extended to 390 miles.
Exercise 16. Make up a sort summary of the text “Flight”.
As with all aircraft, you preflight the helicopter by looking for loose or missing hardware, seepage or leaks, and sufficient quantities of fluids, along with whatever else is need. You also want to examine the blades, which can delaminate, and climb up to the rotor mast for a close-up inspection of some essential bolts. Make sure there’s a lot of room around the ship and that nothing important will be tipped by the air blast when the blades come up to speed. Strap-in whether or not you normally do this in your fixed-wing-because if there were some sort of unreported ground accident and the blades are out of balance or trim, the helicopter may decide to shake itself to death.
The instrument panel should look very familiar. At minimum, there will be an altimeter, airspeed indicator, magnetic compass and some engine gauges. The engine tachometer is the only instrument that will look different. It will be co-joined with the tach for the main rotor. There are a number of ways this is done, but it’s fairly obvious that both needless should be aligned together somehow. If they aren’t, don’t fly the machine.
In order helicopters, monitoring the tachs is vital. The green band is narrow, and constant variations in the throttle are required. The newer ships, as well as all the turbine models, have governors that take this effort away from the pilot.
Text 1. Eurocopter tames the whirl
The prime technology thrust at Eurocopter continues to be the development of a rotating helicopter system that delivers less vibration, less noise and improved performance. The ultimate goal is to the complicated swashplate at the heart of the rotor control system with actively controlled individual blades.
Although the company has been a leader in taming the vagaries of vertical flight – Eurocopter led the industry with the first rigid rotor hub and all-composite blades in 1967, the first fly-by-wire helicopter, the NH90, in 1997 – its latest efforts will push its technological prowess to the limit.
“Rotor dynamics continue to be one of our greatest challenges,” says Yves Favennec, Eurocopter vice-president of research and technology.
Like its counterparts, Eurocopter has been working on active blade technology for years, sharing the work between its French and German partners.
In 2005 it became the first manufacturer to test a rotor system with piezoelectrically actuated flaps attached to the rotor trailing edges, functioning initially with open loop software, then closed loop.
“We saw a significant improvements in noise and vibration,” says Favennec.
“We’re also working on continuously working on a blade with a continuously moving trailing edge, again using piezo-electric actuators.’
In the cabin, vibration improvement are aimed at giving passengers the same experience as they have on fixed-wing jets.
“the future of helicopter is to be able to use them like small airliners into city centres,” says Favennec.
“We’re looking at giving passengers a flying carpet’ level of comfort.”
A range of activities, including passive active damping, are under way to achieve 0,1g vibration levels, many of which have already been spun off into existing types.
Computer simulation plays a vital part in improving understanding, explains Favennec, not only in visualizing airflows around the rotor system, but in areas such as the main rotor gearbox, where it is now possible to simulate the stresses and loads on individual pinions.
“If we can test a new pinion design without having to manufacture it we save a lot of time and money. We’re making real progress in this area,” he says.
Another major theme is to develop all-weather capability of the helicopter, and while the technology to do so exists, the European regulatory framework does not.
“The traffic rules in Europe do not reflect the state of technology,” says Favennec.
“We’re pushing the national and European authorities to allow instrument flight rules flights and to provide specific IFR routes for helicopters lice in the USA.”
As such, Eurocopter is heading the helicopter industry’s contribution to the Eurocontrol Optimal programme, which is looking at changing the procedures for fixed and rotary-wing approach and landing. In June it will use an EC155 to demonstrate a Category 1 IFR landing at Toulouse airport using the Egnos wide area augmentation system. Later in the year it will perform an IFR landing on top of a roof in Lausanne, Switzerland as part of Eurocontrol’s Giant programme, which is investigating the us of GNSS systems for approach and landing.
In the realm of next generation technologies, Eurocopter continues to research tiltrotors and is now concentrating on the four-yeat Nicetrip (novel innovative competitive effect tiltrotor integrated project) effort being run by the European Commission under its sixth framework research programme.
Eurocopter is working with Agusta on the programme, which will lead to windtunnel testing of a one-fourth scale mock-up.
“We have to ensure all of the aerodynamic problems are solved,” says Favennec. He admits Europe is lagging behind the USA in tiltrotor research, “but we didn’t have a government-funded V-22 programme to pay for it”, he adds dors, including Sikorsky, call for a range of vehicles that can lift as much as 26t of Future Combat System equipment, in some cases at high speeds.
Nixon’s team of 80 employees working at two NASA centres has been focusing on the ultra lightweight but protective composite structures that such an aircraft would need to provide safe travel for troops as well as increased performance. The army says it might fund a demonstrator version of the JHL in the 2015 timeframe.
Rotorcraft industry advocates have said the R&D needed to realise the development of the JHL is under funded by about a factor of 10. Most vocal has been Rhett Flater, executive director of the American Helicopter Society, two says a sustained investment of $2 billion a year for the next five to seven years is needed for basic research.
Nixon does not necessarily agree. “I can’t say we’re so under-funded we just won’t get there,” he says, noting that the required R&D will depend on the aircraft the military chooses. An entrant like Bell’s quad tiltrotor JHL candidate, for example, should not require as much research as other candidates as much of the R&G work has already been accomplished on the V-22 Osprey programme, he says.
Text 2. Sales spur Russia to hone helicopter engine technology
While other helicopter-producing national have been investing in a broad range of advanced vertical lift technologies, Russia has been focusing primarily on manufacturing new turboshaft and rotary piston engines.
With new powerplants, the country hopes its helicopter makers can produce competitive product in the lower-medium and lightweight rotorcraft market sectors, where Russian manufacturers feel they have been losing ground to Western rivals.
A key goal to develop indigenous engines for the Kazan Helicopters Ansat and the Kanow Ka-226, both of which currently have Western-built engines.
Kazan Helicopters developed the Ansat with its own funding to fill the void left by the once popular lightweight Mi-2 and Ka-25 helicopters, last produced decades ago. The single-engine helicopter features fly-by-wire flight control, lightweight structures and modern avionics using a mix of Russian and Western components.
Certified two years ago and already operational, with the first units going to South Korea, the Ansat has not been selling well in Russia. Though the Russian air force selected a special version of the Ansat over the Kamov Ka-226 as its future training helicopter for flying school, it demanded that its versions of the trainer and light reconnaissance helicopter were powered by a Russian engine instead of the Pratt & Whitney Canada PK207.
The same issue, but with the Rolls-Royce 250 engines, has limited Russian sales of Kamov Ka-226s in the Ansat’s 2-2,5t maximum takeoff weight (MTOW) class.
Although oil and natural gas giant RAO Gazprom and Moscow Police placed small orders and have already received some of the aircraft for an advanced Russian power plant.
Russia’s emergencies ministry has also made it clear that it will buy only “mature” versions of the Ansat and Ka-226, both of which already passed evaluation tests, when they get a Russian power plant.
Along with the political reasons, a new breed of homemade engines will also make Russian helicopters competitive on the words market. Official expect engines in the 400-1,000hp (300-745kW) range to be two to three-times less expensive than their Western counterparts, while offering better performance.
Much hope is being placed in the VK-800, which is the 600-1,000hp range. This is a joint development project between Russia’s Klimov and Ukraine’s Motor-Sich and Progress. Certification is expected in 2008.
In order to make the product competitive, Klimov has secured the support of the Russian government and local authorities to build an all-new production plant for TV3/7-117 and VK-800 engines in St Petersburg. When complete, the facility will become the first new factory for the Russian aviation industry since the 1970s.
Klimov estimates a global market demand for VK-800-class helicopter engines of 7,900 units through 2015. In Russia, the company project sales of 1,250 VK-800s for Ansat helicopters, including 800 military versions, generating $260 million in revenue. For the Mi-38, it predicts a need for 600 TV7-117 turboshaft engines valued at $420 million, half of which will be for military variants.
Success in the lightweight helicopters sector is currently the most elusive for the Russians. The Mi-34, in the 1t MTOW class saw little success, with a just a dozed aircraft delivered to Kazakhstan, Nigeria and Russian customers.
Blame is laid on the Vedeneyev M-14 engine, which dates back to the radial piston engines of Second World War fighters. Its recent reincarnation as the M-9F, with a digital control block and fuel injectors replacing the carburetor, is seen as a temporary measure.
High hopes are tied to a new lightweight helicopter from Kazan Helicopter, the Aktai. In same MTOW class as the ill-fated Mi-34, the Aktai is based on an AvtoVAZ rotary piston engine, the M-14, the VAZ 4265. Compared with the M-14, the VAZ product the same power but weight 100kg (220lb) less and delivers 25% more fuel efficiency.
AvtoVAZ became part of Russian arms vendor Rosoboronexport two years ago, and is being integrated into other Rosoboronexport industrial initiatives.
“We have received an offer from the helicopter makers of Oboronprom,” AvtoVAZ president Vladimir Artyakov told Flight International.
“They want a new rotary piston engine on their lightweight helicopters, and they want us to do this work for them.”
AvtoVAZ had been producing rotary piston engines since the 1970s for KGB cars until about three years ago. A derivative of the auto engine for aviation purposes failed in the early 1990s when Mil refused to accept the power plant for the Mi-34 due to reliability problems.
Given advances in manufacturing and computer-aided design technology however, the company now believes it can build a durable and reliable rotary piston engine for aviation applications. It recently reaffirmed that it will produce a next-generation aviation engine for the Kazan Aktai.
Text 3. X2 marks the spot for radical rotor designs
(Sikorsky’s X2 helicopter programme has a mixed R&D heritage, and could be the model for the next generation of rotorcraft designs)
A long with broadening the realm of vertical lift, first flight of Sikorsky’s compound helicopter demonstrator in the fourth quarter this year will also spotlight what may become the best model for introducing new civil and military rotorcraft designs – do it yourself.
DIY models could become widespread in the US rotorcraft industry, with limited amounts of government funding available for research and development and demonstrator vehicles that showcase transformational technologies.
The US government continues to invest in the basic and applied research that helps manufacturers create breakthrough aircraft. However, the prime focus for most funding has become results-oriented incremental component efficiency improvements to aid the US military on the battlefield.
Trough the X2 concept is the result of much of that government-funded R&D, the demonstrator itself is 100% Sikorsky funded, and features a frugality and simplicity that reflects who is paying the bill. The aircraft is being from numerous off-the-shelf components scavenged from near and far to keep costs low; so much so that Peter Grant, Sikorsky advanced programmes manager, affectionately refers to the two-seater as a “mongrel”. It uses dual rigid counter-rotating coaxial main rotors and a pusher propeller to reach cruise speeds of 250kt (462km/h), well beyond the 170km maximum speed for conventional helicopters.
The X2 has a mixed heritage of government and industry R&D in rotor systems, propulsion, aerodynamics and controls technologies that will help it meet performance goals of high speed and “low” vibration level as a traditional helicopter at its top speed of 140kt.
The X2’s chief predecessor, the XH-59A advancing blade concept (ABC) helicopter, was built by Sikorsky and funded by the US Army, NASA, Sikorsky and others. Two vehicles were built and readied in two years, starting in 1971, a time when the US government funded such experimental aircraft.
The goal was to test the premise that rigid counter-rotating main rotor, where the advancing blade on each side produces lift while both retreated blades are feathered, could be used reduce drag and tip velocities to allow for cruise speeds well above the norm for helicopters. During testing from 1973 to 1977, Sikorsky pilots reached 240kt with the help of two fuel-thirsty auxiliary turbojets.
Though it was successful, the flight-test programme proved that the concept was ahead of its time because the technologies needed to solve key issues – high vibration levels, tedious mechanical control mechanisms and inefficient power management – have only recently become available.