Helicopter Operations - Preliminaries

Helicopter

• considered one of the heavier-than-air aircraft developed through time and need for the advancement of transportation.

Helicopter

• Also known as “rotorcraft”, “rotary wing” aircraft, and “chopper”

helix

• greek word that means spiral

pteron

• greek word that means wing

1100 (Chinese Flying Top)

• reportedly describes some of the ideas inherent to rotary-wing aircraft.

1480 (Leonardoo Da Vinci)

•   Created a design called “Aerial Screw”

1784 (Launoy and Bienvenu)

•   Feather model which was created more successfully in 1870 by Alphonse Penaud in France.

1870 (Charles-Alphonse Penaud)

• August 18, 1871: Inherently stable airplane called Planophere.

1843 (Sir George Cayley)

•    Father of fixed-winged flight

• Aerial Carriage

• Governable parachutes

1907 (Breguet Brothers and Charles Richet)

•   Made Gyroplane no. 1

1907 (Paul Cornu)

• A bicycle maker like the Wright Brothers

• Attained a free flight of 20 seconds duration

• With twin-rotor craft powered by a 24-horsepower engine.

1912 (Jacob Ellehammer)

• a helicopter that featured contrarotating rotors and cyclic pitch control.

1916 (István Petroczy and Theodore von Kármán)

• proposed an electrically driven rotorcraft to replace the dangerously flammable observation balloons.

George de Bothezat (1924)

• for the U.S. Army Air Force lifted off the ground for slightly less than two minutes, under minimum control.

Argentine inventor Raúl Pateras Pescara

• designed several helicopters in the 1920s and ’30s that applied cyclic pitch control

736 meters (2,415 feet)

• straight-line distance record on April 18, 1924

May 4, Étienne Oehmichen

•       established a distance record for helicopters by flying a circle of a kilometre’s length.

1923 (Juan de la Cierva)

•        Father of the Autogyro

•       First practical rotorcraft

1936 (Focke-Wulf)

•      designed the world’s first practical transverse twin-rotor helicopter, the Fw 61

Fw 61

•       also known as the Fa 61

1938 (Hanna Reitsch)

•      the world’s first female helicopter pilot flying the Fa 61 inside the Deutschland-Halle in Berlin.

1938 (Flettner Kolibri)

• was the first to place a helicopter into mass production

1938 (Igor Sikorsky)

• turned his attention to helicopters once again, and after a long period of development, he made a successful series of test flights of his VS-300 in 1939–41.

commercial use of helicopters

• fire fighting, police work, agricultural crop spraying, mosquito control, medical evacuation, and carrying mail and passengers.

Fuselage

• the outer core of the airframe

• is an aircraft’s main body section that houses the cabin which holds the crew, passengers, and cargo.

Engine

• it is the source of power of the helicopter

Landing Gear

• It is the understructure that supports the helicopter in ground or during landing; it may be a skid or a gear type.

Tail boom

• It is the part of the helicopter that houses the portion of the tail drive and tail rotor assembly.

• It is the part of the helicopter that counter acts the torque produced by the main rotor system.

Tail Rotor System

• It is the part of the helicopter that counter acts the torque produced by the main rotor system. It is used to maintain the directional heading of the aircraft.

Main Rotor System

• the rotating part of a helicopter which generates lift.

Gyroplane

• spiderweb-like frame and four sets of rotors

airfoil

• sometimes called as aerofoil is the cross-sectional shape of a wing or rotor blades in helicopter.

Blade Span

• the length of the rotor blade from center of rotation to tip of the blade.

Chord Line

• a straight line intersecting leading and trailing edges of the airfoil.

Chord

• the length of the chord line from leading edge to trailing edge; it is the characteristic longitudinal dimension of the airfoil section.

Mean Camber Line

• a line drawn halfway between the upper and lower surfaces of the airfoil.

• Middle Line

Leading Edge

• the front edge of an airfoil.

Flight Path Velocity

• the speed and direction of the airfoil passing through the air.

Relative Wind

• defined as the airflow relative to an airfoil and is created by movement of an airfoil through the air.

• In aeronautical term, it is the direction of the wind or the movement of the atmosphere relative to the aircraft or an airfoill.

Pitch Angle

• It is the acute angle between the rotor blade chord and the reference plane.

Trailing Edge

• the rearmost edge of an airfoil

Induced flow

• the downward flow of air through the rotor disk

Resultant relative wind

• relative wind modified by induced flow

AOA (Angle Of Attack)

• the angle measured between the resultant relative wind and the chord line

Angle of Incidence (AOI)

• the angle between the chord line of a blade and rotor hub.

Center of Pressure

• the point along the chord line of an airfoil through which all aerodynamic forces are considered to act.

Rotor Droop

• the blades are somewhat flexible, and when at rest will droop due to the weight and span of the blade

Tip Path Plane

• the tips will pass through a circular surface formed by the rotor blades

• also known as rotor disk

Dynamic Droop

• is how much the blades can move downward as a result of maneuvering and aerodynamic forces when at full operating RPM.

Lift

• opposes the downward force of weight, is produced by the dynamic effect of the air acting on the airfoil and acts perpendicular to the flightpath through the center of lift.

Thrust

• is the force produced by the power plant/ propeller or rotor. It opposes or overcomes the force of drag. As a general rule, it acts parallel to the longitudinal axis.

Weight

• It is the combined load of the aircraft itself, the crew, the fuel, and the cargo or baggage.

Drag

• Is a rearward, retarding force caused by disruption of airflow by the wing, rotor, fuselage, and other protruding objects.

• opposes thrust and acts rearward parallel to the relative wind.

Drag

• Is a rearward, retarding force caused by disruption of airflow by the wing, rotor, fuselage, and other protruding objects.

• opposes thrust and acts rearward parallel to the relative wind.

Induced Drag

generated by the airflow circulation around the rotor blade as it creates lift.

Parasite Drag

• is present any time the helicopter is moving through the air.

• This type of drag increases with airspeed.

Total Drag

• the sum of all three drag forces.

Translating Tendency

• tendency for the whole helicopter to drift in the direction of the tail rotor thrust.

Ground Effect

• It appears when the helicopter is within one-half of a rotor diameter from the ground.

Translational Lift

• This is an additional lift which is obtained when entering horizontal flight due to the increased in efficiency of the rotor system.

Autorotation

• Is the process of producing lift with the rotor blades as they freely rotate from a flow of air up through the rotor system.

Ground Resonance

• It is a self-excited vibration which, as the name implies, occur on the ground.

• This problem is associated with fully articulated rotor systems and is the result of geometrical imbalance of the main rotor system.

Torque

• It is the force when power is applied to the rotor system the fuselage of the helicopter will tend to move in the opposite direction of the rotor.

• Anti-torque rotors are used to eliminate this.

Gyroscopic Precession

• It means that action occurs 90 degrees from the force applied in the same direction as rotation.

Blade Stall

the condition under which the streamline flow of air separates from the camber of the blade and reverse flow occurs, resulting in almost loss of lift.

Coriolis Effect

• It is the change in blade velocity to compensate for the change in distance at the center of the axis rotation as the blade flaps.

Stability

• It is a term used to describe that behavior of an aircraft after it has been disturbed from its trimmed position.

Static Stability

• It means that after a disturbance, the tendency is to return to its original position.

Dynamic Stability

• It is the term used to describe the behavior of the object after the disturbance.

Single Main Rotor

creation of torque as the engine turns the rotor creates a torque effect

• simple design

• lower maintenance cost

• maneuverability

advantages of single main rotor

• higher torque

• anti-torque system is required

• less power

disadvantages of single main rotor

tandem rotors

two horizontal main rotor assemblies mounted one behind the other

co-axial rotor

pair of rotors mounted one above the other on the same shaft

intermeshing rotors

• set of two rotors turning in opposite direction

• also called synchropter

transverse rotors

mounted on the end of the wings

quad rotors

• comprises four rotors in an x configuration

• also known as quadcopter