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In a level turn, lift must be sufficient both to support the helicopter and to provide the inward force. Therefore, it must be greater than during straight and level flight. This additional lift can be acquired by increasing power or by sacrificing some airspeed to maintain your altitude.
For training purposes, turns are divided into three classes:
1. gentle turns, involving angles of bank up to 15 degrees;
2. medium turns, involving angles of bank from 15 to 30 degrees; and
3. steep turns, involving angles of bank over 30 degrees.
In addition to level turns there are:
1. climbing turns - normally, climbing turns are gentle turns; and
2. descending turns - descending turns may be gentle, medium, or steep.
Here are some basic facts you should understand:
1. at a given airspeed, the greater the angle of bank;
a) the greater the rate of turn;
b) the smaller the radius of turn; and
c) the greater the load factor.
2. the higher the airspeed at a given angle of bank:
a) the lower the rate of turn; and
b) the larger the radius of turn.
3. to achieve a turn of the smallest radius and greatest rate for a given angle of bank, fly at the lowest possible airspeed commensurate with safety.
 
LOAD FACTOR

 
Figure 6-1: Load Factor in a turn
 
The resultant of weight and centrifugal force during turns produces an increased load factor on the helicopter. See Figure 6-1. Load factor may be described as the total load imposed on the helicopter, divided by the weight of the helicopter, and is expressed in G units. Load factor during a turn will vary with the angle of bank. Airspeed during the turn does not affect load factor, because for a given bank angle the rate of turn decreases with increased airspeed, resulting in no change of centrifugal force. Note that for a 60 degrees bank turn, the load factor for any helicopter is 2 G regardless of its airspeed (Figure 6-2 refers). This means  that a 3000 lb helicopter in a 60 degrees bank turn will, in effect, exert 6000 lbs of force  on the helicopter structure. Bank angles of up to 30 degrees will produce only moderate increases in load factor that are acceptable under most flight conditions that you will encounter. The load factor rises at an increasing rate at bank angles over 30 degrees,  and may produce unacceptable disk load depending upon the helicopter gross weight  and the prevailing flight conditions.
 

 
Figure 6-2: Load factors produced at varying angles of bank
 
In turbulent air, severe vertical gusts can cause a sudden increase in angle of attack, resulting in increased rotor blade loads that are resisted by the inertia of the helicopter. All helicopters have a maximum permissible load limit that must not be exceeded. As a responsible pilot you should be aware of the limitations of your particular helicopter, and avoid situations that may cause the load factor to approach the maximum. Practically what this means is to avoid doing turns over 30 degrees when you are heavily loaded, especially in gusty or turbulent winds.
The importance of look out, searching the sky for other aircraft before and during a turn, cannot be over-emphasized. Before entering a turn, look around carefully in both directions, above and below. A casual glance is not good enough. During the turn continue to look out especially in the direction of the turn. When recovering from the turn, look around again, in both directions, above and below. To maintain a good lookout, and manage the helicopter at the same time requires the pilot’s constant attention.
Posture is important in all helicopter manoeuvres, and especially so in turns. Sit comfortably upright, do not lean away from the centre of the turn, nor should you make a conscious effort to keep your body stiffly vertical. Relax and ride with the turn. Stiffening up or continually changing sitting position affects visual references, and may cause handling of the controls  to become tense and erratic. 
　
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