Platform Overview

The RFD platform is a single-propeller thrust-vector-controlled (TVC) tail-sitter. Unlike quadrotor-VTOL aircraft (e.g. Carbonix Volanti, DeltaQuad, Quantum Trinity), which carry dedicated lift rotors that are dead weight in cruise, the tail-sitter uses the same propulsion system for both hover and forward flight. The aircraft takes off and lands on its tail with the nose pointing vertically; forward flight is achieved by pitching the whole airframe over ~90° about the lateral axis until the wing is horizontal and generating lift.

Architecture — how the aircraft is built

Common to the family:

• Ø120 mm bayonet fuselage in stacked sections (nose → payload bay → battery bay → avionics → propulsion) — packs into a transport tube.
• Removable fixed wing for cruise; stows alongside the fuselage for transport.
• Propulsion & Control Unit (PCU) — the fixed rear assembly: motor, ESC, propeller, four servos, TVC vanes, and an X-tail of swept fins. The X-tail fins double as the landing gear.
• Control by thrust-vectoring: vanes in the propeller slipstream steer the thrust to produce pitch, roll and yaw moments in hover, complemented by the aerodynamic surfaces in cruise.
• PX4 flight stack on a Cube-class autopilot; RFD QGroundControl-based ground station.

Aircraft identity & markings

• Serial number: on an adhesive label at the battery power connector (receiving side) — in front of the operator every time a battery is plugged in. Quote it in all support and warranty correspondence. Format: <model>-<variant>-<sequence>, e.g. EP250-A-0001.
• Model identifier: printed into the airframe skin.
• CG and orientation fiducials: the CG symbol with fore/aft limit arrows, and the circular “this-way-up” alignment fiducials, are printed into the skin (see Part B weight & balance and assembly).
• Registration: mark and register the aircraft per your CASA obligations; RFD aircraft to date carry CASA-issued registration numbers.

The two family members differ in how thrust is produced:

• EP250 — a ducted, contra-rotating coaxial propulsor. The duct shrouds the prop (safety, compactness) and the contra-rotating pair cancels reaction torque.
• EP450 — a single open propeller, ductless, with the reaction torque handled in closed loop by the TVC vanes/fins. This removes the duct (FTO-clean) at the cost of a slightly larger disc.

See Part B for the per-aircraft anatomy and specifications.

Why tail-sitter

• Tube-launchable. The slender, near-axisymmetric stowed form fits inside a transport/launch tube.
• No dead weight. Every gram of propulsion contributes to both hover and cruise, enabling high cruise/dash performance at low gross weight.
• Mechanical simplicity. No tilt mechanisms, no separate lift rotors, no transition-geometry servos.

What pilots transitioning from other platforms must know

1. The aircraft pitches its entire body to transition. There is no separate “lift” and “cruise” propulsion. Loss of thrust = loss of both lift and control authority at once.
2. In hover the nose points up. Orientation cues that work for a quadrotor (looking down on the platform) do not apply — you are looking at the underside of the aircraft in hover.
3. Transition is an energetic, autopilot-managed manoeuvre. Manual transition is for emergency recovery only. The forward transition is tuned to be near-flat; the back transition trades cruise speed for a modest altitude gain (a “balloon”) as the aircraft pitches up — plan clearance for it.
4. Hover yaw authority is lower than cruise. Yaw in hover comes from the TVC vanes/fins in the slipstream (and, on the EP250, the contra-pair); plan hover manoeuvres accordingly. On the single-motor EP450 this is the weak axis — take off already aligned with the intended outbound bearing (it cannot slew a large heading quickly in hover).
5. Wind affects hover more than a multirotor of similar mass, because the wing presents a large side-on area to crosswinds. Hover wind limits are correspondingly tighter — see each aircraft’s data.

Comparison to quadrotor VTOL (e.g. Volanti/DeltaQuad class)

Aspect	Quadrotor VTOL	RFD tail-sitter
Take-off attitude	Wings horizontal, lift rotors vertical	Wings vertical, nose pointing up
Lift in hover	Dedicated VTOL rotors	Main propulsion thrust
Transition	Gradual, lift rotors assist	Rapid pitch-over, wing lift develops
Cruise efficiency	Lift rotors are dead weight	All propulsion is productive
Hover wind tolerance	Higher (compact footprint)	Lower (wing presents side area)
Stowed form factor	Large case, wings detached	Slender tube, fully integrated
Failure of one lift source	Degrades to remaining rotors	Total (single thrust path) — manage battery/thrust margin