Reviewer-in-Basic-Heli-Prelims.pdf

BASIC HELICOPTER & PROPELLER DESIGN  Military Operations - Helicopters play a crucial role in military INTRODUCTION TO HELICOPTER operations, including troop transport,...

BASIC HELICOPTER & PROPELLER DESIGN  Military Operations - Helicopters play a crucial role in military INTRODUCTION TO HELICOPTER operations, including troop transport, reconnaissance, and close air support. They can operate in various terrains and conditions  Firefighting - Helicopters are used to fight wildfires by dropping water or fire retardant on the flames. They can also transport firefighters and  HELICOPTER equipment to hard-to-reach areas  Annex 1: IC - A heavier-than-air aircraft supported in flight chiefly by the reactions of the air on one or more power driven rotors on substantially vertical axes  Agricultural Operations - A helicopter is an aircraft that is lifted and - Helicopters are used in agriculture for tasks propelled by one or more horizontal rotors, such as crop dusting, seeding, and monitoring each rotor consisting of two or more rotor crops. They can cover large areas quickly and blades. with precision.  HELICOPTER OPERATIONS  Search and Rescue (SAR) - Helicopters are often used in search and rescue missions due to their ability to reach remote or difficult-to-access areas. They can  Aerial Surveying and Mapping hover, land in tight spaces, and carry out - Helicopters are used to conduct aerial rescues from land, sea, or mountains surveys, gather data, and create maps. This is especially useful in areas that are difficult to access by land  Medical Evacuation (MedEvac) - Helicopters are used to transport critically  Transportation injured or ill patients quickly to hospitals. They - Helicopters are used to transport people and are equipped with medical supplies and goods, especially in areas where other forms staffed by paramedics or doctors of transportation are impractical or too slow  Tourism - Helicopters provide aerial tours of scenic  Law Enforcement locations, giving passengers a bird's-eye view - Police and other law enforcement agencies of landscapes, cities, or natural wonders. use helicopters for surveillance, crowd control, and pursuit of suspects. The aerial view allows for better monitoring of large areas. -  Construction - Helicopters can be used to lift and place heavy materials or equipment in construction projects, especially in areas that are difficult to reach with traditional cranes.   1930 - Hundreds of experimental helicopters were built in America and abroad with varying degrees of success.  “Helicopters are multi-mission machines, one  1939 of the most important missions they have, are - Igor Sikorsky flew his VS-300, with which he saving lives.” - Rossi Morreale solved many of the control problems that had  Helicopters are classified as rotorcraft or rotary- plagued other experimenters. wing aircraft to distinguish them from fixed-wing aircraft.  The helicopter derives its source of lift from the rotor blades rotating around a mast  THE HELICOPTER TIMELINE  The word “helicopter” is adapted from the French hélicoptère, coined by Gustave de Ponton d’Amécourt in 1861.  It is linked to the Greek words helix/helikos (“spiral” or “turning”) and pteron (“wing”).  1500 - Leonardo da Vinci, who made drawings and  TYPES OF HELICOPTER models of a "helix.“  Each type of helicopter has specific  1800 advantages depending on the mission - Several small models of helicopters that did requirements, such as speed, lifting capacity, fly. or maneuverability  1907  Single-Rotor Helicopters - The French engineer Louis Breguet built a - The most common type of helicopter with one man-carrying helicopter that actually rose main rotor for lift and a tail rotor to counteract from the ground, but was highly unstable and the torque. had no means of control.  Tandem Rotor Helicopters - These helicopters have two main rotors—one at the front and one at the back—which rotate  1921 in opposite directions - The U.S. Army contracted with Dr. George de Bothezat to build a helicopter  1922 - From the U.S. Army the large four-rotor machine did actually fly.  Coaxial Rotor Helicopters - Equipped with two rotors mounted on the same axis, rotating in opposite directions, eliminating the need for a tail rotor.  Compound Helicopters - These helicopters have additional propulsion systems, such as jet engines or wings, to achieve higher speeds.   Tiltrotor Helicopters  aluminum - A hybrid between a helicopter and an  stainless steel airplane, tiltrotor aircraft have rotors that can  titanium tilt to act as propellers for forward flight o Airframe design encompasses engineering, aerodynamics, materials technology, and manufacturing methods to achieve favorable balances of performance, reliability, and cost.  Intermeshing Rotor Helicopters (Synchropter) - These have two rotors that are mounted close together, intermeshing without hitting each other, eliminating the need for a tail rotor.  Notar Helicopters (No Tail Rotor) 2. Fuselage - These use a system that eliminates the need o The fuselage, the outer core of the airframe, for a tail rotor by directing airflow along the tail is an aircraft’s main body section that boom for stability. houses the cabin that holds the crew, passengers, and cargo. o The fuselage also houses the engine, the transmission, avionics, flight controls, and the powerplant. o Helicopter fuselages and tail booms are MAJOR COMPONENTS AND ROTOR often truss-type or semi-monocoque SYSTEM structures of stress-skin design  The rotors are rotating airfoils that provide lift  Steel and aluminum tubing similar to the way wings provide lift on a fixed-  Formed aluminum wing aircraft  Aluminum skin  Air flows faster over the curved upper surface of  Advanced composites the rotors, causing a negative pressure and thus, o Helicopter fuselages vary widely from those lifting the aircraft with a truss frame, two seats, no doors, and  MAJOR COMPONENTS a monocoque shell flight compartment to  Helicopters come in a variety of sizes and those with fully enclosed airplane-style shapes, but most share the same major cabins as found on larger twin-engine components. helicopters. o The multidirectional nature of helicopter flight makes wide-range visibility from the cockpit essential 3. Main Rotor System o The rotor system is the rotating part of a helicopter which generates lift. o The rotor consists of a mast, hub, and rotor blades. 1. Airframe o A helicopter can be made of:  Metal  wood composite materials  combination of metal and wood composite materials many layers of fiber-impregnated  Mast is a hollow cylindrical metal shaft resins which extends upwards from and is driven o Tubular and sheet metal substructures and sometimes supported by the are usually made of: transmission.  At the top of the mast is the attachment side, causing a boundary-layer control point for the rotor blades called the hub. called the Coanda effect.  The rotor blades are then attached to the hub by several different methods o Main rotor systems are classified according to how the main rotor blades are attached and move relative to the main rotor hub  Rigid  Semi-rigid  Fully articulated 5. Engine / Powerplant 4. Tail Rotor o Most commonly used engines: o Pilots vary the thrust of the antitorque  Reciprocating engine (piston engine) system to maintain directional control Generally used in small helicopters whenever the main rotor torque changes, or Simple and inexpensive to operate to make heading changes while hovering.  Turbine Engine o Most helicopters drive the tail rotor shaft Turbine engines are more powerful and from the transmission to ensure tail rotor are used in a wide variety of helicopters rotation (and hence control) in the event that They produce a tremendous amount of the engine quits. power for their size but are generally more expensive to operate o In most applications, the exhaust outlets simply release expended gases and do not contribute to the forward motion of the helicopter. Because the airflow is not a straight-line pass through as in jet engines and is not used for propulsion, the cooling o Fenestron effect of the air is limited  Another form of antitorque system is the o The gas turbine engine mounted on most Fenestron or “fan-in-tail” design. helicopters is made up of a compressor,  This system uses a series of rotating combustion chamber, turbine, and blades shrouded within a vertical tail. accessory gearbox assembly Because the blades are located within a circular duct, they are less likely to come into contact with people or objects. o NOTAR  Antitorque system provides safe, quiet, responsive, foreign object damage (FOD) o Engine Turbine Engines resistant directional control.  The compressor draws filtered air into the  The enclosed variable-pitch composite plenum chamber and compresses it blade fan produces a low pressure, high  The compressed air is directed to the volume of ambient air to pressurize the combustion section through discharge composite tailboom tubes where atomized fuel is injected into it. The fuel/air mixture is ignited and allowed to expand.  This combustion gas is then forced through a series of turbine wheels causing them to turn. These turbine wheels provide power to both the engine compressor and the accessory gearbox.  The air is expelled through two slots which  Power is provided to the main rotor and tail run the length of the tailboom on the right rotor systems through the freewheeling  unit which is attached to the accessory ROTOR SYSTEM gearbox power output gear shaft.  The combustion gas is finally expelled  The helicopter rotor system is the rotating part of through an exhaust outlet. a helicopter that generates lift On most turbine assemblies used in  A rotor system may be mounted: helicopters, the first stage and second  horizontally, as main rotors are, providing lift stage turbines are not mechanically vertically; connected to each other. Rather, they are  vertically, such as a tail rotor, to provide lift mounted on independent shafts, one horizontally as thrust to counteract torque inside the other, and can turn freely with effect. respect to each other. This is referred to  For TILT ROTORS, the rotor is mounted on a as a “free turbine.” When a free turbine nacelle that rotates at the edge of the wing to engine is running, transition the rotor from a horizontal mounted The combustion gases pass through the position, providing lift horizontally as thrust, to a first stage turbine to drive the compressor vertical mounted position providing lift exactly as and other components, and then past the a helicopter. independent second stage turbine. which  BASIC PARTS OF A HELICOPTER ROTOR turns the power and accessory gearbox to drive the output shaft, as well as other miscellaneous components. 6. Transmission o The transmission system transfers power from the engine to the main rotor, tail rotor, and other accessories during normal flight conditions. o Main components of the transmission system are the main rotor transmission, tail  The swash plate assembly consists of two rotor drive system, clutch, and freewheeling parts — the upper and lower swash plates. unit.  The upper swash plate connects to the mast, or rotor shaft, through special linkages. As the engine turns the rotor shaft, it also turns the upper swash plate and the rotor blade system  The lower swash plate is fixed and doesn't rotate. Ball bearings lie between the upper and lower swash plates, allowing the upper plate to spin freely on top of the lower plate.  Control rods from the upper swash plate have a connection point on the blades, making it possible to transfer movements of the upper swash plate to the blades. - Control rods attached to the lower swash plate connect to the cyclic- and collective- pitch levers.  Blade grips connect the blades to a hub. 7. Landing Gear  ROTOR BLADE MOVEMENTS o A helicopter’s landing gear can be simply a  Main rotor systems are classified according to set of tubular metal skids how the main rotor blades are attached and o Many helicopters do have landing gear with move relative to the main rotor hub wheels, some retractable - Feather - Flap - Lead – Lag   Blade Flap – The ability of the rotor blade to move in a vertical direction. Blades may flap independently or in unison.  Blade Lead or Lag – The fore and aft movement of the blade in the plane of rotation. It is sometimes called hunting or dragging.  Feathering – The action that changes the pitch angle of the rotor blades by rotating - Semirigid them around their feathering (spanwise) axis o The teetering hinge allows the main rotor to  CLASSIFICATION OF ROTOR SYSTEM tilt.  Main rotor systems are classified according to o The feathering hinge enables the main rotor how the main rotor blades are attached and angle’s to change. move relative to the main rotor hub. - Rigid o A semirigid rotor system is usually composed of two blades that are rigidly attached to the main rotor hub. The main rotor hub is free to tilt with respect to the - Fully Articulated main rotor shaft on what is known as a o Fully articulated rotor systems allow each teetering or flapping hinge. This allows the blade to lead-lag (move back and forth in blades to flap together as a unit. As one plane), flap (move up and down about an blade flaps up, the other flaps down. inboard mounted hinge) independent of the o The blades are rigidly attached to the rotor other blades, and feather rotate about the hub. They cannot flap or lead-lag, but they pitch axis to change lift). can be feathered. rigid rotor systems may become more common because the system is fundamentally easier to design and offers the best properties of both semirigid and fully articulated systems. o The rigid rotor system is very responsive and is usually not susceptible to mast bumping like the semirigid systems because the rotor hubs are mounted solid to the main rotor mast. This allows the rotor and fuselage to move together as one entity and eliminates much of the oscillation usually present in the other rotor systems.’ ’  FLIGHT CONTROLS rotor blades. This causes the helicopter to move in the direction that the cyclic is moved. - The control is called the cyclic because it can vary the pitch of the rotor blades throughout each revolution of the main rotor system (i.e., through each cycle of rotation) to develop unequal lift (thrust)  FLIGHT CONTROLS  Collective - The collective, operated by the pilot with the left hand, is pulled up or pushed down to increase or decrease the angle of attack on all of the rotor blades simultaneously. This increases or decreases lift and moves the aircraft up or down. - Collective changes the pitch angle of all the main rotor blades collectively.  Foot Pedals - The foot pedals control the pitch of the tail rotor blades thereby balancing main rotor torque  Throttle - The engine throttle control is located on the hand grip at the end of the collective. - The throttle controls the power produced by the engine, which is connected to the rotor by a transmission. The purpose of the throttle is to maintain enough engine power to keep the rotor rpm within allowable limits to produce enough lift for flight.  Cyclic - The cyclic is the control “stick” located between the pilot’s legs. It can be moved in any direction to tilt the plane of rotation of the