Approximate Density Altitude – Thousands of Feet
 

13
Altimeter� Pressure� Setting Altitude�
 

12 Conversion� Factor 

11
28.0� 1,824� 28.1� 1,727�
10
28.2� 1,630� 28.3� 1,533� 28.4� 1,436�
9
28.5� 1,340� 28.6� 1,244�
8
28.7� 1,148� 28.8� 1,053� 28.9� 957�
7
29.0� 863� 29.1� 768�
6
29.2� 673� 29.3� 579� 29.4� 485�
5
29.5� 392� 29.6� 298� 29.7� 205�
4
29.8� 112� 29.9� 20�
3
29.92� 0
30.0� -73�
2
 
30.2� -257� 30.3� -348�
1
 
 

30.4� -440� 30.5� -531� 30.6� -622�
 

°C SL -18 -12-7 -1 4 1016212732 30.7� -712� 

30.8� -803�
 

°F  0 10 20  30  40  50  60
  Outside A ir Temperature   
Figure 8-1. Density Altitude Chart.      
 

and tailwinds may require the use of more tail rotor thrust to maintain directional control. This increased tail rotor thrust absorbs power from the engine, which means there is less power available to the main rotor for the production of lift. Some helicopters even have a critical wind azimuth or maximum safe relative wind chart. Operating the helicopter beyond these limits could cause loss of tail rotor effectiveness.
Takeoff and climb performance is greatly affected by wind. When taking off into a headwind, effective translational lift is achieved earlier, resulting in more lift and a steeper climb angle. When taking off with a tailwind, more distance is required to accelerate through translation lift. 
 

PERFORMANCE CHARTS
In developing performance charts, aircraft manufacturers make certain assumptions about the condition of the helicopter and the ability of the pilot. It is assumed that the helicopter is in good operating condition and the engine is developing its rated power. The pilot is assumed to be following normal operating procedures and to have average flying abilities. Average means a pilot capable of doing each of the required tasks correctly and at the appropriate times.