Choosing a cruising altitude & planning range
Altitude selection: a judgment call, not just the aerodynamic optimum. Factors:
- Height of hills, peaks, obstructions
- Cruising altitude for leg direction
- Weather: ceiling, visibility, upper winds
- Turbulence
- Distance: short leg needs no high climb
- Fuel economy
- Passenger comfort
- Radio reception, navaid range
- Aircraft performance
- Airspace restrictions
Specific rules:
| Situation | Rule |
|---|---|
| High altitude | Know oxygen requirement and service ceiling |
| Crossing water | Altitude allowing glide to shore with margin if engine quits |
| Map reading | Lower: more detail. Higher: more distance |
| Climb to optimum range altitude | Not always practical. Weigh nature of flight, weather, fuel burned in climb vs range gained |
Range for planning:
| Fuel load | Range source |
|---|---|
| Full tanks | Read off Aircraft Flight Manual charts (normally assume full fuel) |
| Partial fuel (gross weight forces fuel left out) | Not on charts. Use fuel-over-rate method: aeronautics/range-endurance |
Aerodynamic technique (best-range speed, CG, engine-limited max range altitude, headwind/tailwind speed adjustment): aeronautics/range-endurance.
Trap: AFM best-range altitude is not the whole answer (hills, weather, distance, airspace restrictions can override it), and AFM range charts do not cover partial fuel.
References
- TP 1102 Pilot Navigation, Choosing an Altitude
- TP 1102 Ex.10 (Flight for Range and Endurance)