Ex. 17 Advanced Autorotations

If a landing site is close to the helicopter then clearly a standard autorotation will carry us too far from this site. It is possible with altitude to fly around the site making a series of turns in order to stay nearby and eventually fly a constant angle autorotative approach to the site. If we are directly over, or very near to the only available landing site it may be necessary to fly a minimum range autorotation.
Once established in autorotation we reduce the speed by raising the nose with cyclic. In extremes we may find that we have a zero airspeed, which if flown into wind may even result in a backwards ground track.
The rate of descent will increase as speed is reduced below the minimum ROD speed. The RRPM will also settle to a lower value which will result in a lower collective pitch setting being necessary to avoid possibly exceeding the lower limits. The autorotation must be 'converted' to a standard autorotation by about 300 feet in order to have sufficient kinetic energy at the bottom to flare and reduce the rate of descent.

At night or in IMC it is not possible to see the ground. Whilst we may have an idea of our height above the ground it is necessary to adopt an attitude which will result in a low descent rate and when the ground can eventually be seen, would result in a the skids being in a fairly level attitude. This will give us the best chance of performing an EOL under these conditions.

Any turns performed in autorotation will increase the ROD, and the RRPM (due disc loading).
It is normal to practice 180 and 360 turns in autorotation at the PPL level.
Turns are used to remain near, or not overshoot a target site when height is in excess of that need to perform a straight in autorotation.
Turns are also used to manoeuver the helicopter into wind, or into a chosen landing site.

The maximum range in autorotation can be obtained by flying at a higher speed than normal, and drooping the Rotor RPM.
Under normal circumstances increasing the airspeed in autorotation will increase the rate of descent, as well as the ground speed and will result in a slight increase in range. If we examine the characteristics of autorotation we find that at higher airspeeds for a given collective pitch setting we achieve a higher RRPM. We can use this RRPM increase to our advantage and raise the lever to product more rotor thrust and stay in the air longer.