Transverse flow effect is an aerodynamic effect encountered when a helicopter moves (typically forward) through the air. As the helicopter starts moving into undisturbed air, a portion of the disk is in clean, unaccelerated air, while the remaining portion of the rotor disk is still working on descending air.
What are the 3 different regions for autorotation in order?
During vertical autorotation, the rotor disc is divided into three regions—the driven region, the driving region, and the stall region.
What is effective translational lift?
Effective translational lift (commonly referred to as ETL) is a term used to describe the airspeed at which the entire rotor system realizes the benefit of the horizontal air flow. This happens when the helicopter’s rotor disc moves completely out of its own downwash and into undisturbed air.
What is Coriolis effect in helicopter?
The Coriolis effect is when the rotor blades speed up or slow down as the center of gravity moves closer or further away from the axis of rotation. As the rotor disc diameter becomes smaller, all the blades increase speed. This can be felt as an increase in rotor RPM, without corrective action by the pilot or governor.
What turns the main rotor during autorotation?
Autorotation is the state of flight where the main rotor system is being turned by the force of the relative wind rather than engine power. It is the means by which a helicopter can be landed safely in the event of an engine failure.
What is ETL in helicopter?
Improved rotor efficiency resulting from directional flight in a helicopter is called translational lift. While transitioning to forward flight at about 16 to 24 knots, the helicopter goes through effective translational lift (ETL). The rotor blades of the helicopter become more efficient as forward airspeed increases.
What causes blade flapping?
When a rotor blade advances toward the front of the helicopter and experiences an increased velocity of airflow, the increase in lift causes the blade to flap up.
What causes a helicopter to lift?
In the case of a helicopter, the object is the rotor blade (airfoil) and the fluid is the air. Lift is produced when a mass of air is deflected, and it always acts perpendicular to the resultant relative wind. A symmetric airfoil must have a positive AOA to generate positive lift. At a zero AOA, no lift is generated.
Does the Coriolis effect affect helicopters?
Axis of rotation – The axis of rotation of a helicopter rotor is the imaginary line about which the rotor rotates. Coriolis effect – When a rotor blade of a three-bladed rotor system flaps upward, the center of mass of that blade moves closer to the axis of rotation and blade acceleration takes place.
