Precautionary landing inspection pass
Inspection pass: low pass, often preceded by a high pass, over a chosen site before a precautionary landing. Fly it needing minimum attention, leaving maximum for the ground.
Speed and altitude trade-offs:
| Setting | Lower or slower | Higher or faster |
|---|---|---|
| Speed | Shows more; harder to control | Easier to control; shows less |
| Altitude | Shows more detail; raises sensation of speed and risk of hitting trees, wires, towers or hills | Safer; shows less |
Speed:
- Stay out of slow flight range.
- Use manufacturer's lower normal operating range, above endurance speed.
- No figure: near normal approach speed.
- Partial flap helps: more nose-down attitude, lower stall speed.
Altitude:
- Airport tolerates lower pass than hilly, forested terrain.
- Level off and trim at chosen altitude and speed: aircraft holds itself.
Track:
- Never fly directly over site: cannot see straight down.
- Fly beside it: close enough to see surface plainly, far enough that wheels or struts do not block view.
- High wing can fly closer: wing blocks less view.
- Side-by-side cockpit: fly along site's right side (from left seat) for clearer view.
Sequencing (where both passes are flown):
- Some pilots suggest the high pass sets the track and reveals any obvious reason NOT to land.
- Low pass(es) must then give good reasons TO land.
- Many obvious obstacles, no advance information: some pilots suggest several progressively lower passes, so no obstacle is met unexpectedly on first low pass.
- Reliable advance information: fewer or abbreviated passes.
- Know level-flight power setting at inspection speed beforehand: set and trim, freeing attention for field.
Obstacles:
- Check the whole circuit, final approach, and overshoot/departure paths, not just the touchdown area.
- Expect them where experience says: power and phone lines parallel roadways, trees line fields and laneways.
Field length (TP 1102 low pass): 60 kt ground speed covers about 100 ft each second, so field length in feet = time in seconds x 100.
Wind:
- Open water: upwind side usually calmer (wind lines in strong wind).
- Some deciduous trees show the white or silver underside of their leaves on the upwind side.
- No visual sign: estimate from wind at departure point, destination forecast, and groundspeed/drift in flight, then compare against what the ground should show.
Trap: treating the high pass as optional once a low pass is planned; on an unfamiliar, obstacle-rich site, skipping straight to one low pass removes the chance to see the whole picture before descending.
References
- TP 1102 Ex.21, Precautionary Landing: Wind Velocity; Detecting Obstacles; Airspeed; Altitude; Inspection of the Landing Surface; Length of the Landing Surface