Ground effect

Ground effect: within about a wingspan of surface, ground weakens vortices and downwash (PHAK; TP 1102).

• Same lift coefficient needs less angle of attack.
• Same angle of attack makes more lift.
• Induced drag falls.

On takeoff (TP 1102):

• Can lift off below normal airspeed.
• Too little power or too heavy: can get airborne without enough excess speed to climb out of ground effect.
• Climbing out of ground effect before Vx (best angle of climb): can settle back onto runway.
• Contaminated wing: can fly in ground effect, then not climb once out of it (TP 10643).

On landing (PHAK):

• Aircraft tends to float.
• Excess speed at flare stretches float further.
• Reduce power to offset extra lift, or aircraft tends to climb above glidepath.

Leaving ground effect (PHAK):

• Induced drag increases.
• Thrust needed to overcome it increases.
• Wing needs more angle of attack to hold same lift coefficient.

Weight hurts a climb more than any other manoeuvre.

• Overweight aircraft can get off in acceptable distance in ground effect, then climb badly once clear.

Trap: judging a heavy aircraft's climb by how it clears the runway. Ground effect hides weight penalty until out of it.

Practice