14.58 Hovering

14.58.2 Explain the effect of the following factors on hovering flight:

(a) density altitude;

• Higher density altitude → reduced air density
• Results in:
  • Reduced rotor efficiency (less lift for same blade angle)
  • Higher power required to hover
  • Possible inability to hover out of ground effect (HOGE)
• Lower density altitude → increased air density
  • Improved lift
  • Less power required to hover
   

Summary:
As density altitude increases, hover performance decreases and power required increases.

(b) helicopter gross weight;

• Increased weight → more lift required
• Requires:
  • Higher blade angle of attack
  • Increased induced drag
  • More power to maintain hover
• Reduced weight:
  • Less lift required
  • Lower power required to hover