THE AIRCRAFT AND THE INSTRUMENT CAN DISAGREE.
Compare true motion with sensed motion. Introduce a pressure-source fault and watch it enter the feedback loop.
Drag to orbit · right-drag to pan · scroll to zoom. Flight-path angle is shown; body pitch is not resolved by this point-mass model. Height uses a relative scale. A is amber; B is turquoise.
The aircraft obeys force and kinematic equations. The controller receives the pressure-derived measurements.
Whole-run summary · live values appear above
CAUSE → RESPONSE → COMPARISON
B · solid turquoise A · dashed amber
Time plots share the playback cursor. Design sweeps and phase plots retain their own axes. A stopped run holds its final resolved state.
| Whole-run quantity | A · saved | B · live | B − A | Unit |
|---|
A snapshot includes parameter values and event times. Export retains both configurations and their calculated traces.
THE PHYSICS BEHIND THE RESPONSE
Follow each balance, then connect it to the response above. Open Symbols & units for the notation. A dot denotes a time derivative unless a non-dimensional time is stated.
Actual motion follows force balance, even when a blocked pressure source gives the controller an incorrect indication.
The subsonic isentropic relation connects total and static pressure to Mach number. This model uses an independent true temperature to recover true airspeed.
Altitude error commands a flight-path angle. Airspeed error commands thrust. A plausible-looking but false indication can therefore produce a real control response.
The aircraft path and thrust do not change instantaneously. Pressure-derived instrument values also have a 0.5 s first-order lag.
Equations describe this bounded teaching model. Assumptions and source references are retained below. Internal calculations use SI units; controls and plots show their own labelled units.
Generic 3,000 kg aircraft; S = 24 m², CD = 0.026 + 0.055CL², |CL| ≤ 1.5, thrust 0–8 kN. Initial h = 1 km, TAS = 65 m/s. Pressure measurements use subsonic isentropic relations, independent true temperature and 0.5 s instrument lags. Thrust lag 1.5 s; path command ±5°. Blocked pressures are retained at the event. Invalid pressure reconstruction, excessive lift demand or speed below 30 m/s stops the trace. No sensor voting, detailed ADC, real flight-control law or post-stall model.
NASA · Pitot–static measurement ↗FAA · Aircraft systems ↗Numerical checks test the stated equations. They do not establish aircraft certification or experimental accuracy. Schematic flow markers indicate direction; their speed is illustrative. No manufacturer geometry or performance data is reproduced. Version: coupled-labs-v1.1.