Limitations

Deneb Aero gives numerical estimates. Know their limits before using them for design decisions or first flights.

Stall

Steady RANS is reliable for attached flow. Near and past the lift peak, separated flow may be unsteady, and a steady solution settles on one frozen answer. The stall estimate is marked as a steady RANS estimate that is not physically validated. Use the Stall sampled 1° apart and Unsteady past the stall blocks to improve it.

Half models

A half model’s flow is its own mirror image. Past the lift peak one wing can stall before the other; a whole run can settle on that lopsided flow, a half model cannot show it. Its lift and drag there are those of the symmetric flow.

Compressibility

The solver treats the air as incompressible. Above about Mach 0.2 lift reads low, by up to 5%. The Flight step warns about this.

Reynolds number

The coefficients are computed at the cruise speed. Skin friction, laminar flow and separation change with the Reynolds number. Speeds more than 15% from the cruise speed are marked in the report.

Fully turbulent runs

Control, sideslip, rate and propeller runs use a fully turbulent model with wall functions. They are used as increments from a neutral run on the same mesh, which cancels much of the difference.

Geometry

Slots narrower than the surface cells of the mesh are closed or meshed roughly, and small parts are resolved roughly. See Preparing the Geometry.

Flight model

Responses outside the sampled angles and deflections are held at their end values. Other speeds and combined inputs are not validated. Damping that is semi-empirical is named in the notes of the last build. Stopped lift rotors, booms and motors not in the CFD geometry are added as an estimated drag.

Propellers

Propeller tables are for sea-level air. Lower blade Reynolds numbers in thin air, and motors cooling less, are not modelled.

Autopilot gains

The generated gains and the gains tuned in the simulator are starting values. Tune each real aircraft again.

Battery

The battery model is a lithium-polymer pack with no avionics or payload power. Capacity lost in the cold is not modelled.