NAVWEPS OD-EOT-80  APPLICATION OF AERODYNAMICS  TO SPECIFIC PROBLEMS OF FLYING  When normal autorotation has been estab-  lished, a normal power recovery from the auto-  rotation can be made. While such a recovery  technique is effective, considerable altitude  may be lost.  Hence, diving out of the power  settling condition provides the most favorable  means of recovery.  control experienced during “power settling”  results from the turbulent rotational flow on  the blades and the unsteady shifting of the  flow in and out spanwise along the blade.  There is an area of positive thrust in the outer  portion of the rotor as a result of the mass of  air accelerated downward and an area of  negative thrust at the center of the rotor as a  result of the mass of air flowing upward.  The  rotor is stalled only near the hub but no  important effect is contributed because of the  low local velocities.  Actually, real instances of true “power  settling”  are quite rare. A condition often  described incorrectly as “power settling”  is  merely a high sink rate as a result of insufficient  power to terminate an approach to landing.  This situation frequently occurs during high  gross weight or high density altitude operation.  The flow conditions within the rotor are quite  normal and there is merely insufficient power  to reduce rate of descent and terminate an  approach. Such a situation becomes more  critical with a steep approach since the more  rapid descent will  require more power to  terminate the approach.  Operation in the “vortex ring”  state is a  transient condition and the helicopter will  seek equilibrium by descending. As the heli-  copter descends,  a greater upflow through the  disc results until eventually the flow is entirely  up through the rotor and the rotor enters auto-  rotation where lower rates of descent can be  achieved. Unfortunately, considerable alti-  tude will be lost before the autorotative type  of flow is achieved and a positive recovery  technique must be applied to minimize the loss  of altitude.  “Power settling”  can be recog-  nized by rotor roughness, loss of control due  to the turbulent rotational flow, and a very  high rate of descent (as high as 3,000 fpm).  It is most likely to be encountered inadvert-  ently when attempting to hover when suf-  ficient power is not available because  of high  gross weight or high density altitude.  For the professional aviator, there are few  documents which are as important as the air-  plane flight handbook. The information and  data contained in the various sections of the  flight handbook provide the basis for safe and  effective operation of the airplane.  Various sections of the flight handbook are  devoted to the following subjects:  Recovery from “power settling” can be ac-  complished by getting the rotor out of the  “vortex ring state.”  If the condition is en-  countered with low power, rapid application  of full power may increase the downwash suf-  ficiently to get .the rotor out of the condition.  If the condition is encountered at high or  maximum power or, if maximum power does  not effect a recovery, increasing airspeed by  diving will result in recovery with minimum  loss of altitude.  This type of recovery is most  effective but adequate cyclic control must be  available. If cyclic control has been lost, re-  covery must be effected  by reducing power and  collective pitch and entering autorotation.  (2) Operating Procedures. Good procedures  are mandatory to effect safe operation of the  airplane and its equipment. The complexity  of modern equipment dictates the use of special  and exact procedures of operation and any  haphazard or non-standard procedure is an  (1) Equipment and Systems. With the me-  chanical complexity of the modern airplane,  it is imperative that the pilot be familiar with  every item of the aircraft.  Only through exact  knowledge of the equipment can the pilot  properly operate the airplane and contend  with malfunctions.  THE FLIGHT HANDBOOK  411 