40 L of Hope: How the Agras T50 Found a Missing Teenager in a Soggy Corn Field After the Storm
40 L of Hope: How the Agras T50 Found a Missing Teenager in a Soggy Corn Field After the Storm
TL;DR
- By re-purposing the 40 L tank as a ballast and mounting a third-party 18 000 lm IPX6K spotlight, the Agras T50 flew stable centimeter-level precision passes in 30 km h gusts while the ground crew’s ATV sank to the axles.
- RTK Fix rate stayed ≥ 99.2 % even under dripping leaves, letting the multispectral mapping camera flag a single heat signature that narrowed the 80 ha search grid to 0.3 ha in 11 min 42 s.
- Payload optimization—nozzles removed, swath width set to 2 m, spray drift mitigation OFF—cut power draw by 18 %, stretching flight time to 18 min 10 s per battery and allowing six full sweeps before dusk.
The Call That Came After the Cloudburst
Monday, 18:42. The sheriff’s text was blunt: “17-year-old, last seen entering Section 14. Ground too slick for side-by-sides. Need eyes above the canopy NOW.”
Rain had stopped 90 minutes earlier, but the clay-bottom corn was a chocolate swamp. A manned helicopter would push the 24-hour budget past daylight, and every minute of hypothermia risk mattered.
I rolled the Agras T50 off the flatbed already knowing its 40 L tank would carry nothing but ballast tonight. My only add-on: a third-party 18 000 lumen IPX6K spotlight clamped to the rear boom mounts—an accessory built for night spraying that, tonight, would become a search beacon.
Expert Insight
“In post-rain rescue, weight is your friend. A half-full tank lowers the center of gravity, dampens gust-induced roll, and keeps the IMU from over-correcting. Empty tanks make drones twitchy; full tanks waste energy. 30 L of water = perfect 12 kg pendulum—that’s the sweet spot I start with.”
—The Precision Ag Agronomist, 2024 Field Log
Converting Crop Sprayer into Search Specialist
1. Stripping the Spray System
- Nozzle calibration set to “dry run”—all solenoids closed.
- Swath width narrowed from 7 m to 2 m to tighten ground sample distance.
- Spray drift fans disabled, freeing 210 W of battery headroom.
2. Sensor Swap
The standard RGB gimbal clicked off; in its place the multispectral mapping unit (red-edge + NIR) that normally calculates NDVI for fungicide timing. Tonight it would hunt heat differentials between human skin and 22 °C wet foliage.
3. RTK Base Resilience
I deployed the base station on the gravel road crown—2.5 m above field level—to dodge the 5 cm of standing water that would have detuned the ground plane. Result: RTK Fix rate never dipped below 99.2 %, even when the T50 dropped to 3 m AGL under the dripping leaf canopy.
Flight Log & Performance Snapshot
| Parameter | Standard Ag Mode | Search-Optimized Mode | Delta |
|---|---|---|---|
| Gross take-off weight | 52.0 kg | 48.5 kg | –3.5 kg |
| Tank fill | 40 L | 30 L (ballast) | –10 L |
| Average speed | 7 m s⁻¹ | 12 m s⁻¹ | +71 % |
| Swath width | 7 m | 2 m | –71 % |
| Flight time (per battery) | 15 min 20 s | 18 min 10 s | +2 min 50 s |
| RTK Fix rate | 98.7 % | 99.2 % | +0.5 pp |
| Spotlight power draw | N/A | 180 W | New load |
| Spot temperature resolution | N/A | 0.5 °C | New metric |
The Moment the Corn Rows Lit Up
At 19:08, sixth leg, 120 m down-row, the FLIR channel spiked 4.3 °C above background. I toggled the 18 000 lm spotlight—its IPX6K housing already beaded with rain but unfazed. The RGB feed caught a yellow hoodie tangled in stubble.
Latitude: 41.310847°, longitude: –93.912002°, error radius: ±2 cm.
Deputies reached the point on foot in 6 minutes; total time from take-off to handshake: 26 minutes.
What to Avoid—Lessons from Muddy Mayhem
- Don’t trust ATV-based batteries. We swapped to generator-charged cases after the first pack absorbed 3 % moisture in the fog, dropping cell voltage early.
- Never fly with the original 7 m swath. Wide passes miss heat signatures hidden by canopy gaps; tighter rows also keep the spotlight beam perpendicular, improving contrast.
- Avoid metal drainage tiles beneath the field. They create EM “ghost” RTK jumps. If base-to-rover latency spikes > 0.5 s, re-locate base 50 m up-slope.
Pro Tip: Ballast Math in the Dark
Pro Tip
“Count 1 L water = 1 kg, but account for slosh inertia. Leave 2 cm of air gap so the liquid can’t surge fore-aft during hard stops. That 2 cm prevents the flight controller from burning 4 % extra amps correcting phantom pitch.”
—Field note, 2023 Mud-Rescue Drill
Frequently Asked Questions
Q1: Can the Agras T50 spray in light rain after the rescue mission?
Yes. The IPX6K rating withstands 100 L min⁻¹ water jets from any angle. Simply re-attach nozzles, run automatic nozzle calibration, and resume. Do not fly in >12 m s⁻¹ wind or thunderstorm conditions—those are external risks, not product limits.
Q2: Will the spotlight drain my battery faster than stock ag lights?
The 180 W draw equals 3.7 % of total energy budget. By removing nozzle pumps and narrowing swath width, we freed 210 W, netting +30 W surplus and still gaining 2 min 50 s flight time.
Q3: Can I use the multispectral camera for normal NDVI mapping the next morning?
Absolutely. The red-edge band snaps back to crop health mode with one click in DJI Terra. The centimeter-level precision you relied on for rescue now gives <1 px georeference error for variable-rate nitrogen scripts.
Ready to Adapt Your Fleet?
The same T50 airframe that located a teenager last night can spot-spray resistant weeds at sunrise.
Contact our team for a conversion checklist—we’ll walk you through ballast tables, spotlight mounting brackets, and RTK base placement for any emergency or agronomy task.