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Learn

Speeds explained

Quick definitions of the numbers you will see.

V1: decision speedUp to V1 you can stop on the runway. Beyond it you continue the takeoff, even with an engine failure.
VR: rotationThe speed at which you pull back to lift the nose and leave the ground.
V2: takeoff safety speedThe speed to hold after liftoff, giving a safe climb even with one engine out.
Vref and VappVref is the landing reference speed. Vapp adds a margin for wind and gusts.
Flex temperaturePretending it is hotter than it is, so the engines run at reduced thrust and wear less when the runway is long enough.
Top of descentWhere to start coming down: about 3 nautical miles for every 1,000 feet to lose.

Questions

How accurate is it?

It is a simplified physics model built for flight simulators. The 737-800 and A320 presets are the most carefully set up. The 777, A330, 747 and CRJ values are approximate. Use the Match my sim tool to tune any aircraft to your sim. It must never be used for real flight planning.

Where does the data come from?

Airports and runways come from OurAirports, a free public-domain database. Current weather and forecasts come from aviationweather.gov, with model data from Open-Meteo as a backup. Flight plans come from SimBrief.

What is stored or sent?

Your inputs and saved setups stay on your device. When you press Load current weather or Forecast, only the airport code (or its coordinates) is sent to fetch it. When you import from SimBrief, only your username is sent to SimBrief. There is no account and no tracking.

Can I use another aircraft?

Yes. Choose Custom aircraft and enter wing area, thrust, weights and flap lift values, then use Match my sim to fine-tune.

Can I download my results?

Yes. The Briefing page exports every input and result as CSV, JSON, text or a printable PDF.