Obstacle-clearance takeoff technique
An obstacle-clearance takeoff climbs over a fixed obstacle in the departure path (trees, wires, rising terrain) using the least ground distance.
- Vx/Vy meanings and default-vs-obstacle switching rule: see
climb-speed-selection. - Climb performance data matter most with obstacles in the climb path, especially at high field elevation and high ambient temperature (TP 1102).
Procedure:
- Roll: soft field: soft-field technique. Short field: short-field technique. The obstacle does not replace it.
- After liftoff at recommended speed: climb at Vx until the revert cue.
- Revert cue: top of obstacle appears to drop below the horizon = aircraft already above it. Ease into a normal climb for better forward visibility.
AFM-dependent factors:
| Factor | Effect | Action |
|---|---|---|
| Flap | Partial flap can shorten the roll. Climb effect varies by aircraft: helps some, hurts others | Check AFM, assume neither way |
| Weight | Changes climb performance and, in many aircraft, the Vx figure itself | Use AFM weight-specific number, not one memorized speed |
Trap: revert cue is obstacle position against the horizon, not a height or airspeed; watch the obstacle, not the ASI, to leave Vx.
References
- TP 1102 (Flight Training Manual) Take-off: Obstacle Clearance Take-offs
- TP 1102 (Flight Training Manual) Type Conversion: Retractable Landing-Gear