How well it flies
How Plane Forge works
Air: it uses the International Standard Atmosphere — the air is about a third thinner at 3,000 m than at sea level. Lift is ½·ρ·v²·S·CL; the wing stalls at its maximum lift coefficient, which flaps raise. Drag is the body drag (CD0) plus induced drag, which falls with a longer, slimmer wing (higher aspect ratio), plus wave drag near the speed of sound.
Engines: piston power comes from the displacement, compression and revs, and falls with altitude unless it is turbo-normalised. A propeller turns power into thrust; its static thrust comes from momentum theory and its efficiency is about 80% in cruise. Jets give thrust directly, falling with thinner air and speed.
Performance: the takeoff run is simulated step by step with rolling friction until the plane reaches lift-off speed, then climbs over a 15 m (50 ft) obstacle. Rate of climb is the extra power divided by the weight, worked out at every speed and altitude. Range keeps a 45-minute reserve. Stability uses the tail volume, wing aspect ratio and downwash to find the neutral point.
These are estimates for learning and comparing designs, usually within 10–20% of real aircraft. A real aircraft needs a qualified designer, structural testing and approval from the aviation authority.