abrupt collective movement could lead to mast bumping in some rotorcraft with teetering rotor systems. 

Energy is a very important property of all rotating components, and the kinetic energy stored in the rotor system is used to cushion the landing. More lift is produced at the bottom of an autorotation by raising the collective, which increases the angle of attack of the blades. The rotor rpm will also rapidly decay at this point and it is essential to properly time the flare and the final collective pull to fully arrest the descent and cushion the landing. Upon arriving into the course line prior to the flare, the scan should focus almost entirely outside. The scan should include: 

• The horizon for attitude, ground track, and nose alignment; 

• the altitude to set the flare and for closure (groundspeed); and 

• the instrument cross-check of airspeed, rotor rpm, and engine rpm in the descent. 

Every autorotational flare will be different depending on the existing wind conditions, airspeed, density altitude (DA), and the aircraft gross weight. A pilot operating a helicopter at a high DA needs to take into account the effects on the control of the helicopter when recovering from an aborted autorotation. 

Some effects to consider are: 

• Higher rate of descent. 

• Reduced rotor rpm builds in autorotation. 

• Low initial rotor rpm response in autorotation. 

• The requirement for a higher flare height. 

• Reduced engine power performance. 

## Common Errors 

The following common errors should be prevented: 

1. Entering the maneuver at an improper altitude or airspeed. 

2. Entering the maneuver without a level attitude (or not in coordinated flight). 

3. Entering the maneuver and not correcting from the initial deceleration to a steady state attitude (which allows excessive airspeed loss in the descent). 

4. Improper transition into the descent on entry. 

5. Improper use of anti-torque on entry. 

6. Failure to establish the appropriate crosswind correction, allowing the aircraft to drift. 

7. Failure to maintain coordinated flight through the tum. 

8. Failure to maintain rotor rpm within the RFM recommended range. 

9. Excessive yaw when increasing collective to slow rate of descent during power recovery autorotations. 

10. During power recovery autorotations, a delay in reapplying power. 

11. Initial collective pull either too high or too low. 

12. Improper flare (too much or not enough). 

13. Flaring too low or too high (AGL). 

14. Failure to maintain heading when reapplying power. 

15. Not landing with a level attitude. 

16. Landing with aircraft not aligned with the direction of travel. 

17. Insufficient collective cushioning during full autorotations. 

18. Abrupt control inputs on touchdown during full autorotations. 

## Practice Autorotation with a Power Recovery 

A power recovery is used to terminate practice autorotations at a point prior to actual touchdown. After the power recovery, a landing can be made or a go-around initiated. 

## Technique (How to Practice) 

At approximately 3–15 feet landing gear height AGL, depending upon the helicopter being used, begin to level the helicopter with forward cyclic control. Avoid excessive nose- high, tail-low attitude below 10 feet. Just prior to achieving level attitude, with the nose still slightly up, coordinate upward collective pitch control with an increase in the throttle to join the needles at operating rpm. The throttle and collective pitch must be coordinated properly. 

If the throttle is increased too fast or too much, an engine overspeed can occur; if throttle is increased too slowly or too little in proportion to the increase in collective pitch, a loss of rotor rpm results. Use sufficient collective pitch to stop the descent, but keep in mind that the collective pitch application must be gradual to allow for engine response. Coordinate proper antitorque pedal pressure to maintain heading. When a landing is to be made following the power recovery, bring the helicopter to a hover and then descend to a landing. 

In nearly all helicopters, when practicing autorotations with power recovery, the throttle should be at the flight setting at the beginning of the flare. As the rotor disk begins to dissipate its energy, the engine is up to speed as the needles join when the rotor decreases into the normal flight rpm. 

