Limitations

This chapter defines the operating limitations framework for the family. The binding numeric limits for each aircraft are in its Part B Limitations table (EP250 · EP450). Limits are hard limits unless explicitly marked as guidance; do not exceed them. Wind and speed limits are given in multiple units (m/s · km/h · kt); the SI value is authoritative. (Conversion: 1 m/s = 3.6 km/h = 1.94 kt.)

Airspeed & manoeuvre envelope

Each aircraft’s Part B table states: stall speed (Vs), minimum airspeed, trim/design cruise speed, maximum airspeed, and bank limit. Do not command speeds outside the minimum–maximum band, and do not manoeuvre (turn) below the minimum airspeed — turning raises stall speed with bank angle.

Mass & loading

Do not exceed the aircraft’s maximum take-off weight, its payload limit, or its CG band (see the Part B Weight & balance section). Hover thrust margin is the binding constraint for a tail-sitter: an overweight aircraft may cruise normally yet fail to arrest its vertical landing.

Wind — three-tier framework

Wind limits are stated in three tiers per aircraft (the hover phases near the ground are the critical ones for a tail-sitter):

Tier	Meaning	How used
1 · Ground go/no-go	Wind measured at the launch point, sustained over ~30 s	Do not launch above this
2 · Operating limit	Wind at operating height in which the mission may continue	Above this, recover the aircraft
3 · Demonstrated recovery	Highest wind in which a safe recovery has been demonstrated	Margin, not an operating target

Wind at cruise height is typically stronger than measured at the ground — allow for this when the ground reading is near the limit. Measure before every flight with the hand-held anemometer supplied in the RFD kit (sustained reading over ~30 s). Wind build-up discipline: if you intend to operate near the limit, work up progressively across flights (see Part B EP250 for the build-up approach).

Weather

• 🚫 No flight in rain, snow, fog or cloud. The airframes carry no ingress-protection (IP) rating; moisture threatens the open electronics and (where fitted) the pitot system.

• 🚫 Icing band: do not fly between −5 °C and +5 °C in visible moisture (mist, drizzle, wet cloud base) — ice accretion on the propeller and wing is not detectable from the ground.

• Do not launch from standing water, snow or wet mud.

• Temperature (family) [E]: the printed nylon airframe is not the limiting element — the electronics and batteries are.

  Condition	Limit
  Operational (airframe/electronics)	−10 °C to +45 °C
  Storage (aircraft)	−20 °C to +50 °C, dry, out of direct sun
  Battery in use (LiPo & Li-ion)	+10 °C to +40 °C at launch
  Battery charging	+10 °C to +30 °C
  Battery storage	ideally +15 °C to +25 °C

  Battery temperature is a separate limit from air temperature — do not launch on a cold-soaked pack; warm packs above +10 °C before cold-weather operations (see Battery Management).

Altitude

• Regulatory ceiling: 400 ft (120 m) AGL by default in Australia; higher only with the operator’s specific CASA approval. Complying with airspace law is the operator’s responsibility (see Safety & Regulatory).
• Density altitude: hover thrust falls with density altitude. Demonstrated operations to date are near sea level; a density-altitude ceiling will be published after altitude testing.

Satellite navigation

Do not take off without a stable 3D GPS fix. The autopilot requires ≥ 6 satellites to use GPS (PX4 EKF2_REQ_NSATS); RFD recommends waiting for ≥ 10 before take-off. Avoid launching adjacent to large metal structures, transmission towers and power lines (magnetometer and GPS interference).

Hover-time budget

Hover consumes several times cruise power. Each aircraft’s Part B limitations table states its maximum continuous hover time (EP250: 4 min total [V]; EP450: ~18 min [E]); plan missions so that take-off, landing and any hover contingency fit inside it with reserve.

Day / visual line of sight

As delivered, the aircraft are limited to day VLOS operations. Night or EVLOS/BVLOS operation is subject to the operator’s own CASA approvals and appropriate aircraft lighting/equipment.

Command & control

Operate within the demonstrated range of the fitted datalink (see Ground Control Station); range depends strongly on terrain, antenna height and interference.

Launch & recovery area

Use a firm, level, obstacle-free pad of at least 2 m × 2 m (demonstrated landing accuracy is ~0.5 m), taking off aligned with the outbound bearing, with an obstacle-free climb-out and a clear back-transition volume overhead for recovery (the back-transition balloon needs ~20 m of vertical clearance — see Flight Operations).

Prohibited operations

• 🚫 Flight in precipitation, fog, cloud, or the icing band above.
• 🚫 Hover in wind above the aircraft’s hover wind limit.
• 🚫 Flight with any propeller damage, or with a crack in a structural area (see Maintenance → Damage tolerance).
• 🚫 Force-arming past a failed pre-arm check (voids warranty), and flight with non-RFD-approved batteries, propellers or firmware.
• 🚫 Flight over people, beyond the operator’s authorisations, or contrary to CASA rules.

Limitations in this chapter and the Part B tables are the configuration baseline for the aircraft; modifications that affect them require RFD’s written approval (see Document Control).