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. 
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. 
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. 
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. 
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. 
THE FLIGHT HANDBOOK 
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: 
(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. 
(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