User Guide

Autorotational Descent Charts

One of the most terror-filled periods of pilot training is practicing emergency land-

ing procedures. An autorotational landing is an emergency landing made without

power to either engine. In this type of landing, the rotor is disengaged from the

engine, and air moves through the rotor disc as the helicopter keeps its forward

momentum. This keeps the blades revolving, even without power. Autorotational

landings can only be made if the helicopter is already moving forward when the

engines shut down.

The following charts map the helicopters’ rate of descent at different airspeeds

during autorotational flight. The bar marks the rate of descent/airspeed combina-

tions conducive to a safe landing. A lower airspeed (around 60 -70 knots) will give

you a minimum rate of descent (softest landing), but higher airspeeds (100 knots

or greater) will allow you glide the farthest before landing.

Below the Curve. If your airspeed and descent fall beneath the safe autorotation-

al descent curve, rotor RPM is too low, and you aren’t generating enough lift to

glide safely. If you have some altitude to play with, you can increase speed by

nosing down into a slight dive and lowering collective. This will increase your lift.

Above the Curve. If your rate of descent and airspeed measure above the curve

on the chart, your rotor RPM is too high. Raise collective slightly to lower your

RPM.

AH-64D Longbow

D: FLIGHT CHARTS

D.4

0 20 40 60 80 100 120

INDICATED AIRSPEED (KNOTS)

AUTORATIONAL DESCENT

POWER OFF

5000

4000

3000

2000

1000

RATE OF DESCENT (FT/MIN)

Minimum Rate of

Descent Airspeed

Maximum Glide

Distance Airspeed