Icing's lift/drag penalty
Ice shape matters, weight barely. Airflow disruption, not added mass, costs lift and adds drag (TP 10643 ch.4 para 39; AWH 20.3.10).
Thin layers cost a lot:
| Contaminant | Effect | Cite |
|---|---|---|
| Ice, snow or frost roughness as thin as 0.40 mm (1/64 in.) | Airflow disrupted: severe lift loss, increased drag | TP 10643 ch.2 para 1 |
| Frost, snow or ice no thicker or rougher than coarse sandpaper, on leading edge or upper wing surface | Can reduce lift by 30%, increase drag by up to 40% | TP 10643 ch.1 para 14 |
| Thicker or rougher contaminant | Increasing effects on lift, drag, stall speed, stability, control | TP 10643 ch.1 para 14 |
- Texture beats amount: small amounts of rough ice can hurt far more than large amounts. On some wings, insignificant-looking ice sharply raises drag (AC 700-031 App. 5 s.1.1(4)).
- Compensating worsens it: power up and nose up to hold altitude raises angle of attack, so wing underside and fuselage collect MORE ice. Feedback loop: longer exposure compounds faster (AWH 20.3.10).
- Ice builds on all exposed surfaces: wings, propeller, windshield, antennas, vents, intakes, cowlings. Also builds where no heat or boots reach (AWH 20.3.10).
- Accumulation can end the flight: moderate-to-severe icing can load a light aircraft until continued flight is impossible (AWH 20.3.10).
Trap: judging danger by visible ice amount. A 0.40 mm layer already disrupts airflow, severely cutting lift (TP 10643); the natural fix (power up, nose up) accretes more ice underneath.
References
- AWH 20.3.10
- TP 10643 ch.1 para 14
- TP 10643 ch.2 para 1
- TP 10643 ch.4 para 39
- AC 700-031 App. 5 s.1.1(4)