Aircraft Takeoff Distance & Obstacle Clearance Calculator
Calculate takeoff ground roll and distance to clear a 50 ft obstacle with CASA safety margins.
Input Parameters
C172S standard sea level ground roll ~960 ft (PA28 ~1,190 ft, DA40 ~1,250 ft)
C172S sea level distance over 50ft ~1,630 ft
Enter positive for headwind, negative for tailwind
Positive for uphill (+7% per 1% slope), negative for downhill
Calculation Results
Formula & How Aircraft Takeoff Distance & Obstacle Clearance Calculator Works
Takeoff distance is governed by aerodynamic lift requirements and engine power output. Thinner air from high pressure altitude and hotter-than-standard temperatures reduces thrust and propeller efficiency while requiring higher True Airspeed to achieve takeoff lift. CASA CAAP 92-1 recommends applying a 1.25x safety factor to total distance over a 50 ft obstacle.
- Enter Sea Level Base Ground Roll (ft): Input your target parameter value.
- Enter Base Distance over 50 ft Obstacle (ft): Input your target parameter value.
- Enter Takeoff Gross Weight (kg) (kg): Input your target parameter value.
- Enter Maximum Takeoff Weight / MTOW (kg) (kg): Input your target parameter value.
- Enter Pressure Altitude (ft) (ft): Input your target parameter value.
- Enter Outside Air Temperature / OAT (°C) (°C): Input your target parameter value.
- Enter Headwind Component (kts) (kts): Input your target parameter value.
- Enter Grass Runway Surface (+15%): Input your target parameter value.
- Enter Runway Slope Gradient (%) (%): Input your target parameter value.
- Apply Formula: Calculate using
TODR = BaseRoll × (Weight/MTOW)² × [1 + 0.1(PA/1000) + 0.01ΔISA] × WindFactor × SurfaceFactor × 1.25 CASA Margin. - Review Results: View exact computed answers, metrics, and worked mathematical proofs.
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Frequently Asked Questions (FAQs)
How does density altitude affect takeoff distance?
High density altitude reduces engine power output, lowers propeller efficiency, and increases the true airspeed needed for liftoff, dramatically lengthening the takeoff ground roll.
What is the CASA takeoff distance safety factor?
Under Australian CAAP 92-1 / Part 91 guidelines, a 1.15 safety factor is applied to ground roll and 1.25 (or 1.33 for private operations) is applied to total distance over a 50 ft obstacle.
How much does a grass runway increase takeoff distance?
Dry short grass typically increases takeoff ground roll by 15% to 20%, while wet long grass or soft soil can increase ground roll by 25% to 40%.
Authoritative Standards & Verified Reference Citations
Calculations and mathematical logic on this page are grounded in published statutory rules, regulatory standards, and official government data published by the following bodies:
CASR Part 91 general operating and flight rules, Part 121 fuel reserves, and flight crew licensing standards.
Aviation weather services, standard atmosphere (ISA) profiles, METAR/TAF aerodrome weather reports.
Aeronautical Information Publication (AIP), En Route Supplement Australia (ERSA), and airspace procedures.
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