Preview — prints as A6 (105 × 148 mm)
Performance
Unicornlines
Density Altitude
What It Is
Density Altitude = Pressure Altitude corrected for non-standard temperature.
High DA → thinner air → reduced lift, thrust & propeller efficiency.
Quick Formula
DA ≈ PA + 120 × (OAT − ISA temp)
ISA temp at altitude = 15°C − 2°C per 1000 ft PA
Example
| Value | |
|---|---|
| Airfield elevation | 1500 ft |
| QNH | 1005 hPa |
| OAT | +28°C |
| PA ≈ | 1500 + (1013−1005)×27 = 1716 ft |
| ISA at 1716 ft ≈ | 15 − 3.4 = 11.6°C |
| DA ≈ | 1716 + 120×(28−11.6) = 3685 ft |
Rules of Thumb
- DA > 5000 ft → expect noticeably longer T/O roll
- Hot & high = density altitude danger
- Check POH performance charts using DA, not elevation
EASA PPL Syllabus / ICAO Annex 8
Performance
Unicornlines
Density Altitude
What It Is
Density Altitude = Pressure Altitude corrected for non-standard temperature.
High DA → thinner air → reduced lift, thrust & propeller efficiency.
Quick Formula
DA ≈ PA + 120 × (OAT − ISA temp)
ISA temp at altitude = 15°C − 2°C per 1000 ft PA
Example
| Value | |
|---|---|
| Airfield elevation | 1500 ft |
| QNH | 1005 hPa |
| OAT | +28°C |
| PA ≈ | 1500 + (1013−1005)×27 = 1716 ft |
| ISA at 1716 ft ≈ | 15 − 3.4 = 11.6°C |
| DA ≈ | 1716 + 120×(28−11.6) = 3685 ft |
Rules of Thumb
- DA > 5000 ft → expect noticeably longer T/O roll
- Hot & high = density altitude danger
- Check POH performance charts using DA, not elevation
EASA PPL Syllabus / ICAO Annex 8