Helicopter Glossary of Terms

Anti-torque pedals: The controls (foot pedals in real life) which modify the collective pitch of the tail rotor. Because the helicopter's throttle governor keeps the rotors turning at a constant RPM, changing the pitch also changes the thrust generated by the rotor, so the tail rotor can swing the helicopter's tail to the left or right. This is referred to as yaw motion (see the Flight Dynamics page).

Collective: The control (a lever in real life) that modifies the collective pitch of the main rotor's blades; called collective because the pitch of all the blades is modified at the same time. Because the engine keeps the rotor moving at a constant RPM, increasing the rotor blades' pitch with this control will also increase their lift.

Cyclic: The control (a joystick in real life) which changes the pitch of the main rotor's blades as they go through each cycle, used to steer the craft left, right, forward, or aft.

Drag: The aerodynamic force (created by a fluid such as air flowing around an object) that slows the object's motion.

Lift: The aerodynamic force (created by a fluid such as air flowing around an object) that pushes an object upward.

Mach speed: The speed of sound through the air. Mach's number actually describes the speed of sound through any fluid (that is, liquid or gas). In application to aeronautics, though, it is implied that the fluid is air. Note that this number is dependent on a number of factors, such as temperature, humidity, and pressure. Generally, "Mach 1" is cited as 768 miles per hour (the speed of sound at sea level in dry air at 68° Fahrenheit).

Pitch: Movement of the aircraft's nose up or down (see the image on the Flight Dynamics page). When used in discussing a helicopter's rotor, this refers to the way that the blades are angled.

Roll: Movement of the aircraft's body along the line formed by its body; in an airplane, this is easily seen as the dip or rise of the wings. See the image on the Flight Dynamics page.

Rotor: The rotating part of a helicopter that generates the craft's lift; similar in appearance to an oversized airplane propeller, though different in its operation.

RPM: Rotations per minute; a way of measuring the speed of a rotor or propeller. In a helicopter, the RPM of both the main rotor and the tail rotor are held constant.

Speed: The change in the position of an object over time; unlike velocity, speed does not take into account the direction of the object's movement.

Thrust vector: The direction in which the engine or rotor’s thrust is going; for a helicopter sitting on a helipad with its controls at neutral, this is straight down. Thrust vectoring: The ability of helicopters and some other aircraft (such as the Harrier or the F-22) to change the direction of the thrust from its engines/rotors.

Update: To update a piece of software is to convert it to a newer version. In the  X-Plane applications for the iPhone and iPod Touch, this is done by following the instructions in  Chapter 3. This should be done every couple months or so in order to take advantage of new features in the simulator.

Velocity: The combination of an object's speed and the direction of its movement; for example, a helicopter might have a vertical velocity of 500 feet per minute (meaning it moves upward at a rate of 500 feet per minute) or a vertical velocity of -500 feet per minute (meaning it moves downward at 500 feet per minute).

Yaw: Movement of the aircraft's body left or right. See the image on the Flight Dynamics page.