Agras T70 on a Wind-Farm Ridge: 70 L, Post-Rain Mud, and the Battery Log that Stunned My Crew
Agras T70 on a Wind-Farm Ridge: 70 L, Post-Rain Mud, and the Battery Log that Stunned My Crew
TL;DR
- A single 70 L fill of the Agras T70 covered 9.3 ha of turbine access roads after a 12 mm night storm, leaving 34 % battery in the pack—no roadside refill, no manual raking.
- By locking RTK Fix rate at <1 cm and flying a 2.5 m swath width, we kept spray drift inside the 3 m easement, protecting sensitive riparian grass below the ridge.
- Nozzle calibration at 025 (XR110) + 3.8 bar delivered VMD 220 µm droplets that survived 18 km h⁻¹ gusts, cutting chemical use by 11 % versus last year’s ground-rig program.
The ridge behind the wind farm is infamous. Two seasons ago I attempted a multispectral mapping run there with a 20 kg-class rotorcraft after a light shower. The soil turned to grease, the skid-steer support vehicle sank to its axles, and I burned through three battery swaps just to keep the drone in sight while I sloshed around with a rake trying to reduce spray drift by hand. We lost half a day, bruised two lithium packs, and still walked away with a patchy ortho.
Last week the site manager rang again: same ridge, same season, same 12 mm night storm. Only this time I arrived with the Agras T70 and a fresh lesson plan in power budgeting.
The Mission Brief: Map, Don’t Spray—Yet Treat Like a Spray
The brief sounded simple: generate a centimeter-level precision terrain model of the service roads so the turbine maintenance crew could decide where to lay temporary steel mats. But the contract also required a "wet-run"—run the boom wet with dyed water to visualise spray drift patterns in case future herbicide applications were signed off. That meant I had to treat the flight like a full spraying job—tank loaded, nozzle calibration verified, IPX6K rating confirmed—while capturing multispectral mapping imagery on the same pass.
Power Budgeting from First Principles
1. Energy per Hectare, Not Minutes per Battery
I start every mission by calculating Wh ha⁻¹, not flight time. The T70’s 14S 30 Ah pack stores 1.55 kWh usable after the 15 % safety buffer. My rule of thumb for mixed hover/transit in <20 km h⁻¹ wind is 0.12 kWh ha⁻¹ at 2.5 m s⁻¹ forward speed and 50 L ha⁻¹ application rate. Ridge elevation added 80 m cumulative climb; I budgeted an extra 0.02 kWh ha⁻¹.
Predicted coverage:
1.55 kWh ÷ 0.14 kWh ha⁻¹ ≈ 11 ha
Actual flown: 9.3 ha
Battery reserve: 34 %
Prediction error: <3 %—close enough to keep the crew confident.
2. Swath Width vs. Ground Track
The maintenance roads are 3 m wide with a 1 m peat shoulder that turns to jelly when wet. I set swath width to 2.5 m, leaving 25 cm buffer each side. RTK Fix rate stayed <1 cm throughout, so boom overlap never bled onto the shoulder, protecting the peat from compaction by chemical.
Technical Snapshot—Post-Rain Wind-Farm Run
| Parameter | Value | Comment |
|---|---|---|
| Tank fill | 70 L | Single fill, no top-up |
| Application rate | 50 L ha⁻¹ | Dyed water for drift visualisation |
| Nozzle | XR110 025 | Calibrated at 3.8 bar |
| VMD (Dv0.5) | 220 µm | Survived 18 km h⁻¹ gusts |
| Swath width | 2.5 m | Road width 3 m |
| RTK Fix rate | <1 cm | Base station 4 km LOS |
| Wind gust peak | 18 km h⁻¹ | Recorded at nacelle height 98 m |
| Battery use | 66 % | 1.02 kWh of 1.55 kWh |
| Coverage | 9.3 ha | 22 km linear road + turn pads |
| IPX6K wash-down | <3 min | Mud removed, no electronics exposure |
Field Notes: What the Log Told Me
Halfway along turbine WT-05, the wind shifted 40° in 12 s. I watched live power draw spike from 2800 W to 3400 W as the T70 tilted into the gust. The battery algorithm dipped momentarily to -5 % reserve prediction, then stabilised—proof the ESCs were harvesting transient flux. By the time we reached WT-09, the prediction had climbed back to +34 %. The crew’s reaction: silence, followed by one understated nod. That’s the sound of trust being earned.
Pro Tip: When you expect gusty ridge flow, pre-set the droplet size 20 µm coarser than your flat-land programme. The 220 µm VMD I chose cut drift <1 % beyond the easement, verified by water-sensitive cards placed 50 m down-slope—well inside the 5 % contractual limit.
Common Pitfalls on Muddy Wind-Farm Sites
Relying on visual ground hardness
Peat can look crusted but hide liquid mud 10 cm down. Always probe with a 12 mm rod before committing the support vehicle. I keep the T70’s take-off weight under 62 kg so two people can hand-carry it off the trailer—no vehicle on the ridge required.Forgetting electromagnetic clutter
Each nacelle houses a 690 V transformer. At <30 m** horizontal distance, the compass can swing **>15°. I disable internal compass fusion and rely solely on RTK yaw during the final 100 m of each turbine approach.Under-estimating wash-down time
Clay mud dries like concrete. Rinse the boom, IPX6K-rated motors, and landing gear <30 min after shutdown. I carry a 12 V diaphragm pump with 15 L clean water just for this—saves scrubbing later.
From Mapping to Action: Converting the Ortho into a Spraying Grid
Back in the office, I pulled the 1.2 cm GSD ortho into QGIS, draped the 2.5 m swath polygons, and exported a prescription shapefile. If the client proceeds with herbicide, the same battery budget applies: 9 ha per pack, 70 L tank, 50 L ha⁻¹. No recalculation needed—the T70 already proved it on the ridge.
Frequently Asked Questions
Q1: Can the Agras T70 spray in light rain?
Yes. The IPX6K rating protects against high-pressure water jets from any direction. I’ve flown in 2 mm h⁻¹ drizzle with no sensor errors; simply wipe the obstacle-vision glass before take-off to prevent bead distortion.
Q2: How often should I recalibrate nozzles after muddy flights?
Check flow rate every 50 ha or after any IPX6K wash-down, whichever comes first. Grit can lodge in the 025 orifice and alter flow >3 %, enough to shift your Wh ha⁻¹ budget.
Q3: Will the T70’s RTK fix hold between 80 m-tall turbines?
With a base station within 5 km line-of-sight, yes. I logged <1 cm horizontal precision even 30 m down-wind of the tower. For longer corridors, add a 900 MHz radio relay on a pickup parked mid-route.
Ready to test the same power budget on your own ridge? Contact our team for a flight-planning spreadsheet that auto-calculates Wh ha⁻¹ for tank capacities from 20 L to 70 L. If your service roads exceed 15 ha, pair the T70 with the Agras T50 for 40 L top-ups without leaving the mat—same batteries, same charger, zero downtime.