Common Errors Practicing Power Failure in a Hover Technique (How to Practice) 1.  Initiating recovery too late, which requires a rapid  application of controls and results in overcontrolling. 2.  Failure to obtain and maintain a level attitude near the  surface. 3.  Failure to coordinate throttle and collective pitch  properly, which results in either an engine overspeed  or a loss of rotor rpm. 4.  Failure to coordinate proper antitorque pedal with the  increase in power. 5.  Late engine power engagement causing excessive  temperature or torque, or rpm drop. 6.  Failure to go around if not within limits and specified  criteria for safe autorotation. The pedals must be adjusted from a powered flight anti- torque trim setting to the opposite trim setting to compensate  for transmission drag and any unneeded vertical fin thrust  countering the now nonexistent torque and then reset to  compensate for the high power required for hovering flight.  All of the above must be accomplished during the 23 seconds  of the autorotation, and the quick, precise control inputs must  be made in the last 5 seconds of the maneuver.  Helicopters that do not have the throttle control located on  the collective are generally exceptions to basic technique  and require some additional prudence. The autorotation  should be initiated with the power levers left in the “flight,”  or normal, position. If a full touchdown is to be practiced, it  is common technique to move the power levers to the idle  position once the landing area can safely be reached. In most  helicopters, the pilot is fully committed at that point to make  a power-off landing. However, it may be possible to make  a power recovery prior to passing through 100 feet AGL if  the powerplant can recover within that time period and the  instructor is very proficient. The pilot should comply with  the RFM instructions in all cases. When practicing autorotations to a power recovery, the  differences between reciprocating engines and turbines  may be profound. The reciprocating powerplant generally  responds very quickly to power changes, especially power  increases. Some turbines have delay times depending on  the type of fuel control or governing system installed. Any  reciprocating engine needing turbocharged boost to develop  rated horse power may have significant delays to demands  for increased power, such as in the power recovery. Power  recovery in those helicopters with slower engine response  times must have the engines begin to develop enough power  to rejoin the needles by approximately 100 feet AGL. If a go-around is to be made, the cyclic control should be  moved forward to resume forward flight. In transition from  a practice autorotation to a go-around, exercise caution to  avoid an altitude-airspeed combination that would place the  helicopter in an unsafe area of its height/velocity diagram. Power failure in a hover, also called hovering autorotation, is  practiced so that a pilot can automatically make the correct  response when confronted with engine stoppage or certain  other emergencies while hovering. The techniques discussed  in this section are for helicopters with a counterclockwise  rotor disk and an antitorque rotor. This is one of the most difficult maneuvers to perform due to  the concentration needed when transitioning from powered  flight to autorotation and then back again to powered flight.  For helicopters equipped with the power control on the  collective, engine power must be brought from flight power  to idle power and then back to a flight power setting. A delay  during any of these transitions can seriously affect rotor rpm  placing the helicopter in a situation that cannot be recovered.  To practice hovering autorotation, establish a normal  hovering height (approximately 2–3 feet) for the particular  helicopter being used, considering load and atmospheric  conditions. Keep the helicopter headed into the wind and  hold maximum allowable rpm. To simulate a power failure, firmly roll the throttle to the  engine idle position. This disengages the driving force of the  engine from the rotor, thus eliminating torque effect. As the  throttle is closed, apply proper antitorque pedal to maintain  heading. Usually, a slight amount of right cyclic control is  necessary to keep the helicopter from drifting to the left, to  compensate for the loss of tail rotor thrust. However, use  cyclic control, as required, to ensure a vertical descent and  a level attitude. Do not adjust the collective on entry.  The cyclic must be adjusted to maintain the required  airspeed without power, and then used for the deceleration  flare, followed by the transition to level hovering flight.  Additionally, the cyclic must be adjusted to remove the  compensation for translating tendency. The tail rotor is  no longer needed to produce antitorque thrust until almost  maximum power is applied to the rotor disk for hovering  flight, when the tail rotor must again compensate for the main  rotor torque, which also demands compensation for the tail  rotor thrust and translating tendency. 11-8