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:  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:  The following common errors should be prevented:  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.  11-7 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. 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. 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. Practice Autorotation with a Power Recovery  Technique (How to Practice) Common Errors 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.  •  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.  •  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.  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. 