Crosswind design limit at 20% of stall speed
US-built light aircraft: certification crosswind limit, not just technique (TC AIM AIR 2.2, TP 1102).
- 20% rule: must handle 90-degree crosswind up to 20% of stalling speed =
0.2 x stalling speed. - Below 90 degrees: read permissible wind off crosswind component graph using known stalling speed, not the 20% figure directly.
- Reverse use: graph converts max-crosswind limit into max total wind speed by angle (TC AIM AIR 2.2).
- Owner's manual: may give higher or limiting crosswind; use that figure instead (TC AIM AIR 2.2).
- Guide only: 20% figure and graph are a guide, not a hard ceiling. Acceptability at any angle or strength depends on all circumstances, including PIC competence (TP 1102).
Worked examples (crosswind component graph), permissible wind by angle off runway:
| Angle off runway | 60 MPH stall speed | 50 KIAS stall speed |
|---|---|---|
| 90 deg | 12 MPH (0.2 x 60) | 10 kt (0.2 x 50) |
| 60 deg | 14 MPH | 12 kt |
| 30 deg | 24 MPH | 20 kt |
| 15 deg | 48 MPH | 40 kt |
Accident rate: about 10% of all light aircraft accidents in Canada are attributed to pilot failure to compensate for crosswind on landing (TC AIM AIR 2.2).
Trap: 10% accident-rate figure and 20% stall-speed design rule are both round crosswind numbers; do not swap them.
References
- TC AIM AIR 2.2
- TP 1102 Take-off: Cross-Wind Take-offs