The Take-off / landing performance page (/performance/) estimates an aircraft's takeoff and landing distances on each runway of an airfield, with the current conditions, and compares them with the available distances. It requires the Performance module enabled for your club and permission to view performance.
Which aircraft are covered
The aeroplane and microlight disciplines. Gliders, helicopters and balloons are excluded. The aircraft must be active and have an empty weight filled in: see Weight and balance. Otherwise, the page offers to configure an aircraft.
Using the page
- Choose the “Aircraft” and the “Aerodrome (ICAO)”. Your club's airfield is pre-filled.
- Enter the masses: “Front (kg)”, “Rear (kg)”, “Fuel (L)” and “Baggage (kg)”. A preview shows the total mass and the maximum take-off weight.
- Tick “Wet runway” if needed. The box is pre-ticked when the current runway condition report (RCR) flags a wet runway.
- Read the result runway by runway.
Conditions are not typed in: they come from the latest METAR (temperature, QNH, wind direction and speed). Without a METAR, Prepavol uses the standard atmosphere (15 °C, 1013.25 hPa, no wind) and says so. If the airfield has no station, the nearest station is used.
Available distances: TORA and LDA
Prepavol gives priority to official SIA data, with the AIRAC cycle mentioned: TORA, LDA, length, slope, surface and orientation per runway direction. Failing that, it uses unofficial runway data (OurAirports), flagged as such. The available distance shown is the TORA for takeoff and the LDA for landing.
Notes warn when a piece of data is doubtful: runway missing from the SIA, outdated AIRAC cycle, unknown surface (the grass allowance is then applied), unknown slope (not taken into account) or slope above 2% (the model is no longer valid). Always check the VAC and NOTAMs.
What is calculated
- Pressure altitude, density altitude and deviation from ISA.
- Wind components: head, tail and cross. Downwind runways are hidden.
- Two distances per runway: the “AFM distance” and the distance “with margin” (× 1.25 for takeoff, × 1.43 for landing by default).
- The detail of the corrections applied: density altitude, mass, surface, slope, wind.
The basis of calculation is either the flight manual chart when it has been entered in the profile (interpolation between values, no extrapolation outside the table), or a factor model that gives an estimate. The page states which one is used.
Entering the chart and margins on the aircraft profile
In the aircraft profile, the “Flight manual chart (optional)” section asks for a reference mass, pressure altitudes, temperatures and two distance grids: takeoff and landing. A grid must be completely filled in to be used. You can also enter the flight manual's wind limits (demonstrated crosswind, maximum tailwind) and, under “Safety margins”, adjust the club's coefficients.
Without any reference distance, the page invites you to enter those of the flight manual: Prepavol does not guess any value.
Reading the verdict
- Comfortable margin: the distance with margin is less than or equal to 85% of the available distance.
- Marginal: between 85% and 100%.
- Insufficient: above 100%.
A green result can be downgraded to amber when runway data is not verified. Alerts flag a crosswind above the demonstrated value in the flight manual or a tailwind above the limit. The calculation does not cover contaminated runways: refer to the flight manual.
The “Download as PDF” button exports the result. In the flight file, the “Take-off / landing performance” block uses the departure METAR for takeoff and the arrival METAR for landing.
Frequently asked questions
Can I enter the temperature, wind or runway length myself?
No. Conditions come from the latest METAR and runways from SIA data (or failing that OurAirports). You choose the aircraft, the airfield, the masses and whether the runway is wet.
Why does the page show no aircraft?
Only active aircraft of the aeroplane or microlight discipline that have an empty weight are offered. Configure the aircraft profile.
Are the × 1.25 and × 1.43 margins mandatory?
No. They are good-practice margins applied by default. The club can adjust them to the rules of its operations manual.
Does the calculation work on a snow-covered or contaminated runway?
No. The calculation does not cover contaminated runways: refer to the flight manual.