User Guide

3: GROUND SCHOOL
3.7
Ground Effect in a Hover
When a helicopter hovers within a rotor length of the ground, downwash pushes
down against the surface. An artificial cushion is then created as the air “bounces”
off the terrain and back up into the rotor blades. This is called
ground effect.
In the game, you’ll notice ground effect when you’re flying within 50 feet or so of
ground level. Look at the torque indicator (which indicates the engine’s power out-
put) when hovering at 50 feet, then again when you’re hovering above 100 feet.
The difference in engine torque required to sustain lift at these altitudes is due to
ground effect.
Within a ground effect cushion, less power is required to keep the helicopter aloft
because downwash bouncing off of the ground adds to the lift produced by the
spinning rotor blades. When hovering inside ground effect, pilots can decrease the
collective angle of the blades and reduce engine power. Hovering outside ground
effect requires more power than any other helicopter maneuver.
Settling with Power
If a helicopter makes an extremely fast descent with little forward velocity, it can
get caught in its own downwash, and the pilot may find it difficult to generate
enough lift to break the descent. This condition is called
settling with power , also
referred to as the
vortex ring state .
When a helicopter settles with power, its descent rate exceeds the airspeed of the
downwash. This means that airflow under the inner section of the rotor disc is no
longer creating lift — air is actually flowing upward relative to the disc. Lift is being
created in the wrong direction, pushing the craft down in the direction of descent.
Smooth surfaces (like asphalt or concrete) generate a better cushion. Rougher
terrain tends to distort the air flow and make the cushion less uniform.
Lift pushes up
Inducing Flow During Hover
Lift pushes down
Induced Flow in Settling
with Power State
Air
flows
down