Glossary & Acronyms
Common terminology for the RFD VTOL tail-sitter family. Tail-sitter-specific notes are called out.
Acronyms
Section titled “Acronyms”| AGL | Above Ground Level |
| AHRS | Attitude and Heading Reference System |
| AUW | All-Up Weight (as-flown mass incl. battery + payload) |
| CASA | Civil Aviation Safety Authority (Australia) |
| COM | Communication |
| EKF | Extended Kalman Filter (autopilot state estimator) |
| ESC | Electronic Speed Controller |
| EVLOS | Extended Visual Line of Sight |
| FBWA / FBWB | Fly By Wire A / B (stabilised forward-flight modes) |
| FPV | First Person View |
| GCS | Ground Control Station |
| GPS | Global Positioning System |
| HOTAS | Hands On Throttle And Stick |
| HUD | Heads-Up Display |
| IAS | Indicated Airspeed |
| IMU | Inertial Measurement Unit |
| MTOW | Maximum Take-Off Weight |
| NDAA | (US) National Defense Authorization Act — supply-chain compliance |
| PCU | Propulsion & Control Unit (the fixed rear assembly) |
| PIC | Pilot In Command |
| QGC | QGroundControl |
| ReOC | Remotely piloted aircraft operator’s Certificate (CASA) |
| RP | Remote Pilot |
| RPA / RPAS | Remotely Piloted Aircraft / Aircraft System |
| RTL / QRTL | Return To Launch / Q-mode (hover) Return To Launch |
| SITL | Software-In-The-Loop (simulation) |
| TVC | Thrust Vector Control |
| T/W | Thrust-to-Weight ratio |
| Vs | Stall speed |
| VTOL | Vertical Take-Off and Landing |
Definitions
Section titled “Definitions”| Term | Definition |
|---|---|
| Aileron / elevon | Trailing-edge control surface used for roll (and pitch, where elevons combine both) |
| Airspeed | Speed of the aircraft relative to the air mass |
| Altitude | Vertical distance from a reference (usually take-off home, or mean sea level) |
| Attitude | Orientation of the aircraft relative to the horizon |
| Autopilot | Flight-control system that maintains a set course without continuous pilot input |
| Back / reverse transition (pitch-up) | Manoeuvre from forward flight back to hover for landing |
| Cruise | Forward flight on the belly, wings generating lift |
| Dash | High-speed forward flight at maximum throttle |
| Failsafe | Pre-configured contingency behaviour triggered by a known fault |
| Forward transition (pitch-over) | Manoeuvre from hover (nose-up) to forward flight (nose-forward) |
| Forward-flight configuration | Aircraft horizontal, wings loaded, thrust along the body axis |
| Hover configuration | Aircraft vertical, nose-up, thrust opposing gravity |
| Pitch / Roll / Yaw | Rotation about the lateral / longitudinal / vertical body axis |
| PCU | The fixed rear assembly (motor, ESC, prop, servos, TVC vanes, fins) shared across a variant |
| Tail-sitter | A VTOL aircraft that takes off, hovers and lands on its tail, nose pointing up |
| Thrust vector control (TVC) | Steering the propeller slipstream with vanes to produce control moments |
| Transition | Either transition manoeuvre; “the transition” usually means forward transition |
| Tube launch | Deployment from a vertical tube under the aircraft’s own thrust (no pyro/pneumatic assist) |
| Waypoint | A 3D point (lat/lon/alt) the autopilot flies to, optionally with an action |
Note on axes for tail-sitters. The body-axis convention shifts by 90° between hover and cruise. In hover, “yaw” rotates the aircraft about the vertical (thrust) axis; in cruise, “yaw” rotates about the vertical (lift) axis. Body roll/pitch/yaw are referenced consistently to the aircraft body, but the world-frame effect of a given control input changes between regimes. Pilots transitioning from quadrotor or conventional fixed-wing platforms must internalise this before first flight — see Platform Overview.