Calculator Inputs
Example Data Table
| Scenario | Airspeed | Wind | Ground Speed | ROC | Safety | Gradient | ft/NM | Obstacle Clearance |
|---|---|---|---|---|---|---|---|---|
| Light aircraft departure | 92 kt | +8 kt | 84 kt | 920 ft/min | 10% | 9.733% | 591.43 | 149.57 ft |
| Turboprop climb review | 125 kt | -6 kt | 131 kt | 1450 ft/min | 12% | 10.674% | 648.85 | 418.27 ft |
| High obstacle departure | 105 kt | +4 kt | 101 kt | 880 ft/min | 8% | 8.036% | 480.95 | -43.10 ft |
These rows are sample planning cases for demonstration. Replace them with aircraft-specific performance data before making operational decisions.
Formula Used
1) Ground speed
Ground Speed (kt) = Climb Airspeed (kt) − Wind Component (kt)
Positive wind means headwind. Negative wind means tailwind.
2) Effective rate of climb
Effective ROC = Entered ROC × (1 − Safety Factor / 100)
3) Ground speed in feet per minute
Ground Speed (ft/min) = Ground Speed (kt) × 6076.12 ÷ 60
4) Climb gradient
Climb Gradient (%) = Effective ROC ÷ Ground Speed (ft/min) × 100
5) Climb gradient in feet per nautical mile
Climb Gradient (ft/NM) = Effective ROC × 60 ÷ Ground Speed (kt)
6) Climb angle
Climb Angle (deg) = arctan(Climb Gradient ÷ 100)
7) Altitude at obstacle
Altitude at Obstacle (AGL) = Screen Height + [Gradient (ft/NM) × Distance (NM)]
8) Obstacle clearance
Clearance = Altitude at Obstacle (AGL) − Obstacle Height (AGL)
This calculator is a planning aid. It simplifies the climb path into steady-state geometry and does not replace certified aircraft performance data or approved procedures.
How to Use This Calculator
Enter the expected climb airspeed and wind component first. Use a positive wind value for headwind and a negative value for tailwind.
Enter your expected climb rate in feet per minute. Add a safety factor if you want a more conservative result based on real-world variability.
Provide the obstacle distance and obstacle height above the runway environment. Keep both values in nautical miles and feet.
Set a screen height and target gradient. The screen height defines your starting climb point, while the target gradient helps compare your margin.
Press the calculation button. The page will show the results above the form, generate the plot, and enable CSV and PDF downloads.
Review the status line, obstacle clearance, gradient margin, and required climb rate. Negative clearance means the entered profile does not clear the obstacle.
Frequently Asked Questions
1) What does climb gradient mean?
Climb gradient describes vertical gain relative to horizontal distance traveled. It can be shown as a percentage or as feet gained per nautical mile during climb.
2) Why is climb gradient different from rate of climb?
Rate of climb measures vertical speed only. Climb gradient also depends on horizontal speed, so the same vertical rate can produce different gradients at different ground speeds.
3) Why does ground speed affect obstacle clearance?
Higher ground speed covers more horizontal distance each minute. With the same climb rate, the aircraft gains less height per nautical mile, reducing climb gradient and obstacle clearance.
4) How do headwinds and tailwinds change the result?
A headwind lowers ground speed and usually improves gradient. A tailwind raises ground speed and usually worsens gradient, which can significantly reduce obstacle clearance.
5) Why should I use a safety factor?
A safety factor reduces the entered climb rate to reflect operational uncertainty. It helps create a more conservative planning result for performance reviews and departure assessments.
6) What is screen height in this tool?
Screen height is the initial altitude above the departure surface where the climb profile starts in this model. It often represents a standard departure reference point.
7) Can I use this for certified dispatch or compliance?
Use it as an engineering and planning aid only. Certified dispatch, aircraft limitations, and regulatory compliance should always rely on approved aircraft data and procedures.
8) Which units does the calculator expect?
Use knots for speeds, feet per minute for climb rate, nautical miles for horizontal distance, and feet for altitudes and obstacle heights.