FlyCart 100: How We Delivered a 100 kg Winch System to a Desert Solar Farm at 02:17 A.M.—and Beat a Sudden Katabatic Gust
FlyCart 100: How We Delivered a 100 kg Winch System to a Desert Solar Farm at 02:17 A.M.—and Beat a Sudden Katabatic Gust
TL;DR
- The FlyCart 100 lifted a 100 kg dual-battery pallet, flew 42 km BVLOS, and still held 18% reserve after a surprise 35 km/h night katabatic downdraft.
- Payload-to-weight ratio tuning, real-time route optimization, and an emergency parachute logic layer kept the mission inside a ±2 m drop zone on a live solar-panel array.
- Operators who lock payload mass without accounting for night-time density altitude give away 6–8% hover efficiency—easy to prevent with the pre-flight checklist inside.
The Call-Out
The text came in at 19:42: “Critical inverter swap needed on Array 14. Site access road washed out. Night window opens 01:30–03:00. Can you land on the panels?”
I was already pre-flighting the FlyCart 100. Its delivery rails were configured for a 100 kg crate containing the replacement inverter, a winch system, and two liters of coolant. Payload-to-weight ratio sat at 0.68, well inside the drone’s 0.75 structural ceiling. Battery A and Battery B—each 6.8 kWh—were married in dual-battery redundancy mode, giving us 22.4 kW of continuous overhead before any thermal fold-back.
Mission Geometry: Route Optimization vs. Darkness
The flight plan crossed 42 km of black desert, a corridor we fly weekly under an experimental BVLOS waiver. The twist tonight: a zero-lux new-moon environment and an inverter swap that could not tolerate dust. Translation—no rotor wash above 3 m/s on touchdown.
I uploaded waypoints into the FlyCart’s route optimization engine, letting it chew on top-of-climb temps (38 °C at dusk), expected density altitude (+1,340 ft above field elevation), and panel reflectivity that can spoof LiDAR returns. The algorithm shaved off 3.2 km and 1 min 14 s by hugging the lee side of a low mesa, keeping us below the rotor-disc line of a nearby telecom tower.
Pro Tip
Night desert ops always run cooler, but don’t trust the thermometer alone. Plug the forecast lapse rate into the FlyCart’s mission planner; it auto-adjusts vertical speed so you don’t hit a temperature inversion that suddenly bumps your power draw +9%.
Take-off: Calm, Then the Switch
We launched at 01:46. Air was glass, METAR showing 6 kt out of the south. At 30 m AGL, the FlyCart’s front-mounted IR-EO gimbal painted the desert floor in grayscale. I keep the gimbal on even in cargo mode—it’s the first sensor to spot tower guy wires or rogue UAVs.
Eleven kilometres out, the array’s LED beacons appeared like a string of pearls. That’s when the weather flicked a switch. A katabatic drainage that hadn’t shown in the high-resolution NAM run spilled off the mesa. In 14 seconds, the wind swung 180°, speed jumping to 35 km/h and gusting 42 km/h. The FlyCart’s EKF blended air-data, GNSS, and visual-inertial odometry. Rotors spun up +8% RPM, but the aircraft never deviated more than 0.7 m horizontally.
The secret sauce? Fly-by-wire propulsion governors tied to a 50 ms gust suppression loop. While cheap drones swap efficiency for brute thrust, the FlyCart keeps its 5.2 kg/kW specific thrust ratio intact, so payload-to-weight doesn’t nosedive when the air gets angry.
Precision Drop: Winch System on a Live Array
Array 14 sits atop a 3° tilt, rows spaced 4.3 m. Touchdown ellipse had to stay inside 2 m × 2 m to avoid micro-cracks. I toggled the winch system icon on the GCS: 0.2 m/s descent, 30 kg tether preload. At 2 m above the panels, the FlyCart hit a laser-defined virtual ceiling, killed vertical speed, and unspooled the crate softly onto the glass. Contact switches cut power to the winch drum; the aircraft leapt 1.5 m and held station while technicians unhooked.
Battery readouts: A at 46%, B at 48%. We still had 18% total energy reserve—comfortable margin for the 42 km home leg plus a reroute around a new cell building to the west.
Technical Snapshot
| Parameter | FlyCart 100 Value | Industry Mean (100 kg Class) |
|---|---|---|
| Max payload | 100 kg | 80–90 kg |
| Payload-to-weight ratio | 0.68 | 0.50–0.55 |
| Dual-battery redundancy energy | 22.4 kWh | 14–16 kWh |
| Hover efficiency (SL, ISA) | 66.3% | 58–61% |
| Emergency parachute deployment V | <6 m/s | 8–10 m/s |
| BVLOS radio link range (verified) | 52 km | 35–40 km |
| Night EO detection range (human) | 320 m | ~150 m |
Common Pitfalls—What to Avoid on Solar-Panel Night Drops
Static dust devil prep
A single 30 kt whirl can sand-blast panel coating. Check local vorticity indices; if >12, delay drop or approach from the leeward side where panels act as a wind fence.Over-locking payload mass
Pilots love round numbers. Loading exactly 100 kg without subtracting coolant expansion volume risks 1.2 kg overweight at 35 °C. Always weigh at ambient, not in the air-conditioned hangar.Forgetting panel reflectivity in IR
Polished glass can raise background temp +8 °C, tricking the thermal sensor into thinking the motors are hot. Disable external reference when landing on bare cells.Relying on moonlight for visual observers
BVLOS doesn’t mean blind. A night-vision spotter with an 810 nm IR illuminator extends detect-and-avoid range to 1.2 km—well outside the 400 ft buffer our waiver demands.
Expert Insight
Expert Insight
“In 1,300 night deliveries, the moment that still wakes me up is when a 1 kW RF amplifier on a solar site walked our compass +6°. FlyCart’s redundant IMU array rejected the bad mag, but only because we’d disabled magnetic heading fusion above 20 kt ground speed. Always hard-code a fallback mode; the sky rarely gives you second chances.”
— Lena Lugo, Chief Remote Supply Pilot, Atacama Ops
Frequently Asked Questions
Q1: Will the FlyCart 100 maintain payload capacity in a 35 °C night-time inversion?
Yes. Density altitude is automatically compensated; expect <3% hover thrust margin loss, well inside the 12% power reserve.
Q2: Can the winch system handle fragile components like glass inverters?
Absolutely. The constant-tension drum keeps shock load under 0.3 g, lower than a manual two-person hand-off.
Q3: Is the emergency parachute reusable after a night deployment?
The canopy is single-use, but the mortar and extraction rocket are good for three repacks—just log the serial number and send it to our service hub; turnaround is 48 h.
Ready to run your own night-time BVLOS delivery? Contact our team for a payload-to-weight simulation and waiver roadmap. If your circuit is smaller than 100 kg, check out the FlyCart 30 for lighter, shorter hops—same avionics, scaled-down props, and interchangeable batteries.