Density Altitude Explained (and Why It Matters at High-Elevation Airports)
Quick answer: density altitude is the altitude the airplane "feels" like it's at, based on air density. Hot temperatures, high elevations and low pressure make it higher, which means longer takeoff rolls, slower climbs and less engine power.
Why it matters
At a high-elevation airport on a hot summer afternoon, density altitude can be thousands of feet above the field elevation. An airplane that climbs well on a cool morning can struggle to clear obstacles. This is one of the classic causes of takeoff accidents in the mountain West.
How to estimate it
- Pressure altitude ≈ field elevation + (29.92 − altimeter setting) × 1,000
- Standard temperature at that altitude ≈ 15°C − 2°C per 1,000 ft
- Density altitude ≈ pressure altitude + 120 × (actual temp − standard temp)
Try it with our density altitude calculator.
What pilots do about it
- Use the POH performance charts for the actual conditions, not a rule of thumb.
- Fly early in the morning when it's cooler.
- Reduce weight: fewer passengers, less fuel or baggage if appropriate.
- Lean the mixture for best power per the POH.
Estimates are a study aid. Always use your aircraft's POH and get proper mountain-flying instruction before operating at high-elevation airports in hot weather.