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Should you find that the nose of the helicopter is tending to pitch down while in the steep turn, do not attempt to correct by applying cyclic backpressure alone since this will only serve to tighten the turn. Use lateral cyclic to reduce the angle of bank slightly, then correct the attitude with coordinated aft cyclic. Another frequent error is the application of too much aft cyclic before it is required when rolling into the steep turn, causing altitude control to be erratic.
EXERCISE 18 - AUTOROTATIONS 3 (RANGE VARIATIONS)
In preparation for this exercise, you should review the two previous air exercises on autorotations, Exercises 7 and 13.
In the preceding autorotational exercises, you found that to achieve the minimum rate of descent in most helicopters, you fly the autorotations at the manufacturer’s recommended airspeed. However, under emergency conditions, this airspeed will not necessarily result in your reaching your chosen landing spot. In fact, under actual emergency conditions, it will often be necessary to vary the airspeed, change the direction of flight, or employ some other combination of airspeed and turns in order to reach the spot. For example, should the landing spot be a small clearing in a wooded area, considerable manoeuvring may be necessary if you are to effect a safe landing. For this reason, you should take advantage of the helicopter’s capabilities in autorotative flight.
AIRMANSHIP
Prior to conducting an exercise of autorotations, it is recommended to roll off the throttle once while the helicopter is on the ground. This will confirm that the clutch or freewheeling unit is operating correctly, and that the engine is not going to quit. Always choose a large, level area for the full on with plenty of safety margin.
In the air, a confirmation of the selected area should be followed by the HASEL check.
Prior to conducting this exercise, your instructor will review with you the speeds, rotor RPM, and VNE according to your helicopter type. The maximum range speed will also vary depending on the helicopter types. (Refer to Figure 18-1).
Figure 18-1: Rate of descent vs. forward speed in autorotation
EXTENDING THE RANGE
Many helicopter manufacturers specify a maximum autorotation range speed in their flight manuals (Fig 18-2). It is this speed that you should reference when performing this exercise. There is certainly no purpose in exceeding that speed, as after that point, no increased range will result. Indeed rate of descent will increase range will decrease.
You will also note that, although the rate of descent is higher, the distance covered over the ground is appreciably greater.
To enter and practise a range autorotation, after completing the checks, proceed as follows:
1. from cruise speed into wind, give the verbal warning “Practice engine failure”, lower collective while smoothly rolling off throttle to idle;
2. at the same time, adjust cyclic to set the airspeed for maximum range and maintain balance with pedals;
3. check the RRPM frequently, particularly in turns, and make any collective adjustments to maintain the RRPM within limits;
4. maintain the range speed throughout until the spot can be made, then reduce the speed to the minimum rate of descent speed. This will reduce both forward speed and the rate of descent; and
5. Flare, level and land the helicopter as previously taught.
Try to return to the minimum rate of descent speed as early as possible (by 200 feet AGL). Should you hold the maximum range speed down to flare height, you would find that the flare would have to be maintained longer in order to reduce the ground speed to acceptable level for the touchdown.
MAXIMUM RANGE AUTOROTATION
By reducing RRPM using collective the range can be further extended, but the rotor tachometer has to be closely monitored (Fig 18-2). In this instance, it is even more important to return to normal autorotation limits as soon as the landing spot is assured.
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