IAS 0 ktTAS 0 m/sAlt 0 mVS 0 m/sAoA 0°L/D 0readyFPS 0

Drag to orbit, wheel or pinch to zoom. Arrows (toggle in the panel): blue lift, red drag, green thrust, white weight.

Aircraft Flight Envelope: Lift, Drag Polar, Stall and Glide Performance

A four-seat light aircraft in a longitudinal point-mass model. Change weight, flaps, air temperature and altitude, then watch stall speed, best-glide speed and the power curves move.

Aircraft and air (applied on Reset)

Flying

Live readouts

Drag polar (lift coefficient against drag coefficient)

Power required and available against speed

Altitude and speed history

Experiment: which glide speed goes farthest?

With the engine idle and weight, flaps and air as set above, the aircraft is flown at each speed (pitch holds the speed), the glide angle is measured from the integrated flight, and it is compared with the closed form atan(CD/CL). The flattest glide should sit at the best-glide speed.

Independent numerical checks

Controls

Drag / one finger: orbit; wheel / pinch: zoom.
Hold altitude: the autopilot sets angle of attack to climb or descend toward the target height. Hold speed with pitch: pitch controls speed (use it with the throttle at idle to glide). Manual stick: you set the angle of attack directly.
Autothrottle holds the target speed; switch it off to set the throttle yourself. If you pull the stick beyond the stall angle with the nose held, the nose drops by itself (pitch break) and the wing flies again.
Touching the ground ends the run and reports the sink rate.

The science

Atmosphere. ISA troposphere: T = 288.15 − 0.0065 h + ΔISA, p = 101325 (1 − 0.0065 h / 288.15)^5.2559 Pa, ρ = p / (287.05 T). Indicated airspeed is shown as TAS √σ with σ = ρ/1.225.

Lift and drag. L = ½ ρ V² S C_L, D = ½ ρ V² S C_D. The lift curve is linear, C_L = a (α − α₀) with a = 4.9 rad⁻¹, α₀ = −2°, up to C_L,max = 1.55 at α ≈ 16.5°; beyond that lift falls to 55 % of the peak over 8° and flat-plate pressure drag 1.28 sin²α is blended in. Flaps (0–30°) shift the curve up by up to 0.45 and add 0.018 (δ/30)² to C_D0. Drag is the parabolic polar C_D = C_D0 + k C_L², k = 1/(π e AR), AR = b²/S = 7.47, e = 0.75, C_D0 = 0.027 (S = 16.2 m², b = 11 m, typical of a four-seat high-wing light aircraft).

Characteristic speeds. Stall speed V_s = √(2W / (ρ S C_L,max)). Maximum lift-to-drag occurs at C_L = √(C_D0/k), giving (L/D)_max = 1/(2√(C_D0 k)) at V_bg = √(2W/(ρS) · √(k/C_D0)). In a steady glide the flight path angle is γ = atan(C_D/C_L), independent of weight; weight only changes the speed at which each angle occurs.

Engine. Shaft power falls with density as P = P₀ (σ − 0.12)/0.88 (P₀ = 120 kW), propeller efficiency 0.80, thrust T = η P / V capped by a static-thrust limit of 3.2 kN × σ. Power required in level flight is D V; excess power gives the rate of climb ROC = (P_a − P_r)/W.

Equations of motion (point mass in the vertical plane, wind axes, RK4 at 50 steps per second): m dV/dt = T cos α − D − m g sin γ, m V dγ/dt = T sin α + L − m g cos γ, dh/dt = V sin γ. Pitch dynamics are replaced by a first-order response of α to the commanded angle (time constant 0.5 s); the short-period mode is therefore not modelled.

Simplifications and illustrative constants. No ground effect, wind, turbulence, sideslip, propeller slipstream, or compressibility; the post-stall curve and the pitch-break amount are illustrative; the autopilot gains are scheduled for stability, not tuned to a real autopilot. Not for flight planning. Models built with Blender, scene by Three.js.