question: How does a helicopter fly forward, and not just up/down?
comment: In order to fly forward, a helicopter will tilt slightly forward. Now that it is tilted forward some of the downward thrust will actually push it forward instead of just up.
passages: Section::::Flight conditions.:Forward flight.
   Section::::Flight.:Transition from hover to forward flight.
  
  As a helicopter moves from hover to forward flight it enters a state called translational lift which provides extra lift without increasing power. This state, most typically, occurs when the airspeed reaches approximately , and may be necessary for a helicopter to obtain flight.
  
  Section::::Flight.:Forward flight.
   The control is called the cyclic because it changes the pitch of the rotor blades cyclically. The result is to tilt the rotor disk in a particular direction, resulting in the helicopter moving in that direction. If the pilot pushes the cyclic forward, the rotor disk tilts forward, and the rotor produces a thrust in the forward direction. If the pilot pushes the cyclic to the side, the rotor disk tilts to that side and produces thrust in that direction, causing the helicopter to hover sideways.
   In many piston engine-powered helicopters, the pilot manipulates the throttle to maintain rotor speed. Turbine engine helicopters, and some piston helicopters, use governors or other electro-mechanical control systems to maintain rotor speed and relieve the pilot of routine responsibility for that task. (There is normally also a manual reversion available in the event of a governor failure.)
  
  Section::::Flight conditions.
  
  There are three basic flight conditions for a helicopter: hover, forward flight and autorotation.
  
  Section::::Flight conditions.:Hover.
   The control is called the cyclic because it changes the mechanical pitch angle or "feathering angle" of each main rotor blade independently, depending on its position in the cycle. The pitch is changed so that each blade will have the same angle of incidence as it passes the same point in the cycle, changing the lift generated by the blade at that point and causing each blade to fly up or down in sequence as it passes the same point. If the pilot pushes the cyclic forward, the rotor tilts forward. If the pilot pushes the cyclic to the right, the rotor disk tilts to the right. 
   A swashplate controls the collective and cyclic pitch of the main blades. The swashplate moves up and down, along the main shaft, to change the pitch of both blades. This causes the helicopter to push air downward or upward, depending on the angle of attack. The swashplate can also change its angle to move the blades angle forwards or backwards, or left and right, to make the helicopter move in those directions.
  
  Section::::Flight.
  
  There are three basic flight conditions for a helicopter: hover, forward flight and the transition between the two.
  
  Section::::Flight.:Hover.
   A helicopter pilot manipulates the helicopter flight controls to achieve and maintain controlled aerodynamic flight. Changes to the aircraft flight control system transmit mechanically to the rotor, producing aerodynamic effects on the rotor blades that make the helicopter move in a deliberate way. To tilt forward and back (pitch) or sideways (roll), requires that the controls alter the angle of attack of the main rotor blades "cyclically" during rotation, creating differing amounts of lift (force) at different points in the cycle. To increase or decrease overall lift requires that the controls alter the angle of attack for all blades "collectively" by equal amounts at the same time, resulting in ascent, descent, acceleration and deceleration.
   With a single main rotor helicopter, the creation of torque as the engine turns the rotor creates a torque effect that causes the body of the helicopter to turn in the opposite direction of the rotor. To eliminate this effect, some sort of antitorque control must be used with a sufficient margin of power available to allow the helicopter to maintain its heading and provide yaw control. The three most common controls used today are the tail rotor, Eurocopter's "Fenestron" (also called a "fantail"), and MD Helicopters' "NOTAR".
  
  Section::::Rotor configurations.:Single main rotor.:Tail rotor.
   The collective pitch control, or "collective lever", is normally located on the left side of the pilot's seat with an adjustable friction control to prevent inadvertent movement. The collective changes the pitch angle of all the main rotor blades collectively ("i.e.," all at the same time) and independent of their position. Therefore, if a collective input is made, all the blades change equally, and as a result, the helicopter increases or decreases its total lift derived from the rotor. In level flight this would cause a climb or descent, while with the helicopter pitched forward an increase in total lift would produce an acceleration together with a given amount of ascent.
   Section::::Differential pitch control.
  
  For helicopters with two horizontally-mounted rotors, changes in attitude often require having each rotor behave inversely in response to the standard control inputs from the pilot. Those with coaxial rotors (like a Kamov Ka-50) have both rotors mounted on the same mast, one above the other on concentric drive shafts contra-rotating–spinning in opposite directions on a shared axis–and make yaw changes by increasing the collective pitch of the rotor spinning in the direction of the desired turn while simultaneously reducing the collective pitch of the other, creating dissymettry of torque.
   Some rotorcraft, such as helicopters, have a powered rotary wing or "rotor", where the rotor disc can be angled slightly forward so that a proportion of its lift is directed forwards. The rotor may, like a propeller, be powered by a variety of methods such as a piston engine or turbine. Experiments have also used jet nozzles at the rotor blade tips.
  
  Section::::Propulsion.:Powered aircraft.:Other types of powered aircraft.
   Torque effect
  
  The torque effect experienced in helicopters and single propeller-powered aircraft is an example of Isaac Newton's third law of motion that "for every action there is an equal and opposite reaction."
  
  In helicopters, the result of the torque effect is a tendency of the main rotor to want to turn the fuselage in the opposite direction from the rotor. A small tail rotor is the most common configuration to counter the torque effect.
   Controls vary the pitch of the main rotor blades cyclically throughout rotation. The pilot uses this to control the direction of the rotor thrust vector, which defines the part of the rotor disc where the maximum thrust develops. Collective pitch varies the magnitude of rotor thrust by increasing or decreasing thrust over the whole rotor disc at the same time. These blade pitch variations are controlled by tilting, raising, or lowering the swash plate with the flight controls. The vast majority of helicopters maintain a constant rotor speed (RPM) during flight, leaving the angle of attack of the blades as the sole means of adjusting thrust from the rotor.
   The collective pitch control or "collective" is located on the left side of the pilot's seat with a settable friction control to prevent inadvertent movement. The collective changes the pitch angle of all the main rotor blades collectively (i.e. all at the same time) and independently of their position. Therefore, if a collective input is made, all the blades change equally, and the result is the helicopter increasing or decreasing in altitude.
   The cyclic is used to control the main rotor in order to change the helicopter's direction of movement. In a hover, the cyclic controls the movement of the helicopter forward, back, and laterally. During forward flight, the cyclic control inputs cause flight path changes similar to fixed-wing aircraft flight; left or right inputs cause the helicopter to roll into a turn in the desired direction, and forward and back inputs change the pitch attitude of the helicopter resulting in altitude changes (climbing or descending flight).
   Flight controls allow pilots to control the collective (or throttle, on fixed pitch helicopters), the cyclic controls (pitch and roll), and the tail rotor (yaw). Controlling these in unison enables the helicopter to perform the same maneuvers as full-sized helicopters, such as hovering and backwards flight, and many other maneuvers that full-sized helicopters cannot, such as inverted flight (where collective pitch control provides negative blade pitch to hold heli up inverted, and pitch/yaw controls must be reversed by pilot).
   Section::::History.
  
  Section::::History.:Early design.
  
  The earliest references for vertical flight came from China. Since around 400 BC, Chinese children have played with bamboo flying toys (or Chinese top). This bamboo-copter is spun by rolling a stick attached to a rotor. The spinning creates lift, and the toy flies when released. The 4th-century AD Daoist book "Baopuzi" by Ge Hong (抱朴子 "Master who Embraces Simplicity") reportedly describes some of the ideas inherent to rotary wing aircraft.
   The helicopter includes 3 stick-on weights that can be attached to the nose in order to achieve forward flight, and some owners add greater weight (paper clips or pellets) to the nose, or nose canards. These modifications do increase the forward flight speed, but can reduce hovering ability and can increase the battery drain. Another mod that allows the helicopter to fly forward is to slightly twist the tail rotor downwards. This mod has the advantage of not adding weight to the helicopter and therefore doesn't affect battery drain.
   Traditional helicopters get both their propulsion and lift from the main rotor, and by using a dedicated propulsion device such as a propeller or jet engine, the rotor burden is lessened.
   "Compound rotorcraft" have wings that provide some or all of the lift in forward flight. They are nowadays classified as "powered lift" types and not as rotorcraft. "Tiltrotor" aircraft (such as the Bell Boeing V-22 Osprey), tiltwing, tail-sitter, and coleopter aircraft have their rotors/propellers horizontal for vertical flight and vertical for forward flight.
  
  Section::::Methods of lift.:Heavier-than-air – aerodynes.:Other methods of lift.
   The pilot tries to perfectly balance a helicopter so that the fuselage remains horizontal in hovering flight, with no cyclic pitch control needed except for wind correction. Since the fuselage acts as a pendulum suspended from the rotor, changing the center of gravity changes the angle at which the aircraft hangs from the rotor. When the center of gravity is directly under the rotor mast, the helicopter hangs horizontal; if the CG is too far forward of the mast, the helicopter hangs
   Any rotor system has a delay between the point in rotation where the controls introduce a change in pitch and the point where the desired change in the rotor blade's flight occurs. This difference is caused by phase lag, often confused with gyroscopic precession. A rotor is an oscillatory system that obeys the laws that govern vibration—which, depending on the rotor system, may resemble the behaviour of a gyroscope.
  
  Section::::Controls.:Collective.
   Now imagine the helicopter in forward flight at, say, "v" meters per second. The speed of the blade-tip at point A in the diagram relative to the air is the "sum" of the blade-tip speed and the helicopter forward-flight speed: "r"ω+"v". But the blade-tip speed at point B, relative to the air, is the "difference" of its rotational speed and the forward-flight speed: "r"ω-"v".
   Helicopters which lose power do not simply fall out of the sky. In a maneuver called autorotation, the pilot configures the rotors to spin faster driven by the upward moving air, which limits the rate of descent. Very shortly before meeting the ground, the pilot changes the momentum stored in the rotor to increase lift to slow the rate of descent to a normal landing (but without extended hovering).
  
  Section::::Rapid descents.:Dives.
   Section::::Design.:Parts and functions.
  
  The simple rotor of a Robinson R22 showing (from the top):
  
  BULLET::::- The following are driven by the link rods from the rotating part of the swashplate.
  
  BULLET::::- Pitch hinges, allowing the blades to twist about the axis extending from blade root to blade tip.
  
  BULLET::::- Teeter hinge, allowing one blade to rise vertically while the other falls vertically. This motion occurs whenever translational relative wind is present, or in response to a cyclic control input.
  
  BULLET::::- Scissor link and counterweight, carries the main shaft rotation down to the upper swashplate
  
raw_presuppositions: Helicoptor should only be able to fly straight up or down.
raw_corrections: Helicoptor can tilt to fly forward. 