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REDUCING THE RANGE 
You will learn two methods of reducing the range in autorotation during this exercise:
1. reducing the airspeed; and
2. turning.
1. Reducing the airspeed (Fig 18-2):
The procedures are the same as other autorotations until after the entry, then as the helicopter enters autorotation, apply aft cyclic to reduce airspeed. It is possible to perform an autorotation at zero airspeed, but the rate of descent increases rapidly, and yawing may develop that is difficult to control because of loss of `keel surface effect’. During low speed autorotations it is permissible to have a negative groundspeed but NEVER a negative airspeed, so be sure to maintain some indicated airspeed. Select a reduced airspeed that will enable you to make your selected landing spot. You will practise this manoeuvre with speeds down to 10-15 mph with your instructor.
Notice that the rate of descent, in this type of autorotation, is significantly higher than with one flown at the minimum rate of descent speed. For that reason, it is important to increase the airspeed, to that for minimum rate of descent, as soon as you are assured of reaching the selected touchdown spot. This will have the effect of reducing the rate of descent to  that which will allow you to safely flare the helicopter and land. Remember to abide by the height/velocity diagram when performing autorotations. Therefore, ensure that the airspeed is increased to the minimum rate of descent speed in order to remain outside the “Avoid” areas. As a rule of thumb to increase airspeed by 10 mph requires 100 feet of altitude.
 

 
Figure 18-2: Range variations 
 
2. Turning (Fig 18-3):
It is also possible to shorten the range of an autorotation by turning the helicopter. When  using turns to reduce the range, bear in mind that the increased disc loading can cause a  rapid increase in the RRPM. Monitor the RRPM to ensure that the limits are not exceeded;  it may also be necessary to raise the collective slightly to prevent overspeeding the rotor,  but reduce it again as soon as possible to conserve RRPM for the landing.
 

 
Figure 18-3: Shorten the range by turning 
 
In addition to shortening the range of an autorotation, turning will greatly increase the rate of descent. Consider this fact when judging the distance to the desired touchdown spot, as this will determine what type of manoeuvre will allow safely reaching that spot. Figures 18-4, 18-5 and 18-6 represent different examples of turning autorotations.
Rates of descent in tight-turning autorotations can build up to more than 2500 feet per minute in some types of helicopters.
 

 
Figure 18-4: the 90-degree turning autorotation

 
Figure 18-6: the 180-degree turning autorotation 
 

 
Figure 18-5: the 360-degree turning autorotation
 
EXERCISE 19 - PRACTICE FORCED APPROACHES
Practice forced approaches, as the name suggests, are the practical application of the autorotation and emergency exercises which your instructor has previously taught you.
During this exercise, you will be shown how to apply these skills to any emergency situations simulated by your instructor. The most common is the surprise engine failure. Your instructor will teach you the actions to be taken should the engine fail. The instructor normally simulated by twisting off the throttle; at that time:
1. enter autorotation by fully lowering the collective, setting the best rate of descent speed with cyclic, and adjust the pedals to control the yaw;
2. select a landing area, obviously the larger and flatter, the better, if possible into the wind;
3. adjust the controls to make the selected area, using the techniques shown in the previous lessons on autorotation to achieve that landing spot (Fig 19-1); and
　
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