the basics of how a helicopter flies

THE BASICS OF HOW A HELICOPTER FLIES PAIGE DUMKE

INTRODUCTION Unlike ordinary aircraft with fixed wings, a helicopter is a type of rotorcraft that allows for both vertical and horizontal flight, as well as vertical takeoff. The first successful helicopter was developed by a man named Igor Sikorsky in 1942. Since then, single main rotor helicopters have been used every day, and have become an essential tool for emergency transportation. Although these machines are made up of intricate systems that are always becoming more complex with the growing technology, the same basic mechanisms and parts have remained the same. What makes a helicopter different from an aircraft is how lift (the aerodynamic force that opposes the weight and moves the rotorcraft vertically) and thrust (the amount of force required to overcome the drag force and move the rotorcraft forward through the air) is supplied through a set of rotors that allow it to take off and land vertically.

ANATOMY In order to function, a helicopter consists of three main parts:  The Rotor System,  The Transmission,  The Engine. The frame of the helicopter is called the fuselage, which contains the cockpit. Attached to this body, is the tail boom. These parts and other basic parts of a helicopter can be found below in Figure 1. The functions of the main parts of the helicopter will be discussed below, as well.

Figure 1. http://s.hswstatic.com/gif/helicopter-basic-parts.gif

THE ROTOR SYSTEM The rotor system is made up of two main parts: • The Main Blade. One of the most important parts of the helicopter that consists of the Rotor Mast & Swash Plate • The Tail Blade. Works counteractively with the Main Blade and is attached to the Tail Boom & Fuselage

When rotating, these blades work together to produce lift and thrust. The rotor system is also the key identifier of what makes a helicopter different from a conventional aircraft.

THE MAIN BLADE The main rotary blade performs the same function as a plane’s wings: to create lift. Lift is produced by rotating and changing the amount of revolutions per minute (rpm) of the blades. The rate at which a helicopter takes off is directly proportional to the rpm of the main blade. Also, by changing the angle of attack of the blades, a pilot can change the direction of the helicopter. The main blades are vital to the performance of the helicopter.

Figure 2. http://s.hswstatic.com/gif/helicopter-rotor.gif

The main rotor blades also allow the aircraft to move laterally, make turns, and change altitude. Attached to the main rotor blade is the stabilizer bar, which works directly with the main rotor blade using its weight and rotation to dampen out the vibrations caused by the main rotor. This allows for the helicopter to be more stable and as a result, causes smoother movements by the aircraft as a whole.

THE ROTOR MAST The rotor mast is an apparatus that connects the main rotor to the transmission and rotates the main rotor and swash plate.

THE SWASH PLATE In order to control the blades, the pilot needs some sort of mechanism to communicate the adjustments. This part is called the swash plate and consists of two plates that work together to adjust the blades’ rpm and angle of attack. Connected to the main rotor through the mast, this swash plate allows the pilot to make all changes to the blades so that he can properly steer the helicopter. The swash plate is vital to controlling a helicopter because it controls the pitch of the entire helicopter as well as the altitude. It adjusts the angle of all blades while simultaneously increasing and decreasing lift. The figure to the right illustrates this procedure.

Figure 3. http://s.hswstatic.com/gif/helicopter-directionalflight.gif

THE TAIL BLADE The tail rotor blade is the other type of blade on helicopters, accurately named from its location, off of the tail boom. It is much smaller than the main rotor blade; however, the tail rotor blade always spins faster than the main rotor. This is because the tail rotor blade works in conjunction with the main rotor blade. They are linked together through a series of drive shafts (mechanical components that transmit rotation and torque) and gearboxes (a series of incased gears that make up the transmission), which means when the main rotor spins, so does the tail rotor. The main purpose of the tail rotor is to counteract the torque caused by the main rotor so that the aircraft won’t just rotate around in circles. The tail rotor blade also acts as a rudder and can make the helicopter turn left and right.

THE TRANSMISSION AND ENGINE The engine supplies the helicopter with power. In modern helicopters, a gas turbine engine is used. The transmission is the mechanical part that transmits the power supplied by the engine to the rotor system. Containing a set of gearboxes, the transmission makes sure the power translates into rotation of the blades. The main gearbox of the transmission makes sure the speed that the main rotor rotates at does not exceed the speed of the engine shaft. A second gearbox does the same for the tail rotor. A rotor driveshaft is used to transfer power from the helicopter transmission to the tail rotor blade.

WORKING TOGETHER Once the power is supplied from the engine, the transmission takes this power and spreads it throughout the fuselage to the rotor systems, causing rotation. When the rotor system blades are turning, the helicopter begins to achieve lift, the main force to how a helicopter is able to fly. Lift is affected by the pitch and angle of attack, which are provided by the blades. In order to maneuver in the air, the main rotor blade uses the swash plate to control the pitch and altitude of the helicopter. By adjusting the angle of attack of all blades instantaneously, the helicopter can move up, down and laterally. As for the tail rotor blade, its opposing rotation counteracts the torque that the main rotor blade produces, which refrains the Figure 4. http://www.naval-technology.com/projects/uh1y-huey-utilityhelicopter from spinning in circles helicopter/images/uh-1yhuey_5.jpg uncontrollably. The rotation of the tail rotor blade helps the helicopter to turn left and right. With all these parts working together, it is ultimately the job of the pilot to know when to make adjustments to these parts to make the helicopter fly at optimum conditions.