FAA Private Pilot Helicopter (PRH)Performance and LimitationsHard
As density altitude increases, the maximum gross weight at which a helicopter can hover out of ground effect (OGE)
- Aremains constant regardless of altitude
- Bincreases, because thinner air reduces drag
- Cdecreases, because more power is required to produce the same lift
- Dincreases only if winds are calm
Show answer & explanationAnswer & explanation
Correct answer: C. decreases, because more power is required to produce the same lift
As density altitude increases, air density decreases, requiring the rotor system to work harder (more power) to generate the same amount of lift. Since available power is also reduced at altitude, the maximum gross weight for OGE hover decreases as density altitude increases.
Why the other options are wrong
- A. Hover performance charts clearly show gross weight limits decreasing with density altitude.
- B. Thinner air reduces lift production, not drag benefit, so this is incorrect.
- D. Wind can improve hover performance but does not override the fundamental density altitude effect.
Density Altitude and Hover Performance
As density altitude increases, both engine power output and rotor lift efficiency decrease, reducing the maximum gross weight for hovering, especially OGE.
- Higher density altitude decreases available engine power
- Higher density altitude requires more blade pitch (power) for the same lift
- OGE hover performance is more sensitive to density altitude than IGE
Memory trick: Thin air means thin margins — less weight allowed as DA climbs.