BVLOS Inspection Flight at a Controlled Aerodrome Boundary
You are the remote pilot in command of a 6.8 kg multirotor conducting a BVLOS powerline inspection. The operation is authorized under a RBAC 100 special certificate for a corridor 3.2 km long. The corridor's northern end lies 1.1 km from the boundary of a controlled aerodrome whose control zone extends to 1 500 ft AGL. Your planned cruise altitude is 400 ft AGL. At 09:40 the tower informs you that a search-and-rescue helicopter will depart the aerodrome at 10:00 and will transit your corridor at 500 ft AGL. Your visual observer at the northern waypoint reports the control link RSSI has dropped from -72 dBm to -91 dBm over the last four minutes, and the wind at 400 ft is 18 kt gusting 26 kt from the northwest, perpendicular to the corridor. Your battery state of charge is 61 percent and the aircraft is at the midpoint of the corridor.
1. What actions do you take in the next five minutes, and in what order of priority?
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Priority one is deconfliction with the helicopter, because that risk is time-bound and involves other people. The corridor's northern end is inside or immediately adjacent to controlled airspace, so I must establish and maintain separation from the SAR transit. I would contact the tower, state my position, altitude and the 400 ft cruise level, request a clearance or coordination for the 10:00 transit, and if coordination cannot be guaranteed, I would either descend below the helicopter's route to a safe altitude over unpopulated ground or hold clear of the corridor's northern segment until the helicopter has passed. A remote pilot must not assume the helicopter crew can see a 6.8 kg aircraft.
Priority two is the control link. A drop from -72 to -91 dBm over four minutes is a trend, not noise, and it coincides with a strong crosswind. I would turn back toward the launch point while the link is still usable, reduce distance to the ground station, and verify antenna orientation. If RSSI continues to fall, I execute the lost-link procedure: the aircraft should hold or return autonomously, and I must already know which it will do and at what altitude.
Priority three is energy. At 61 percent, mid-corridor, with a 26 kt gusting crosswind, the return leg will cost more than the outbound leg. I would compute a conservative return time, set a hard reserve, and land at the nearest suitable site rather than complete the inspection. The inspection is the least important objective; the flight is not worth completing if the reserve is threatened.
2. The tower clears you to remain at 400 ft AGL but requires you to stay at least 500 m from the aerodrome boundary. Your northern waypoint is 1.1 km from the boundary. Does the clearance change your plan?
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Yes, it changes the geometry but not the underlying obligation. A 500 m buffer from the boundary is a containment requirement, and my northern waypoint at 1.1 km gives roughly 600 m of margin. However, the buffer applies to the aircraft's actual position, not to the planned waypoint, and with 26 kt gusts the aircraft can drift significantly during a hold or a turn. I would compute the worst-case drift: at 26 kt, roughly 13 m per second, a 20-second hold or turn can displace the aircraft 260 m, which eats nearly half the margin.
I would therefore set a geofence at 500 m from the boundary, with a warning at 600 m, and plan the northern turn to occur at least 700 m from the boundary so that gust-induced drift does not breach the buffer. I would also confirm with the tower whether the 500 m applies horizontally at all altitudes or only within the control zone's lateral limits, because the clearance wording matters.
The clearance does not authorize me to ignore the helicopter. It is a containment clearance, not a deconfliction clearance. I would still confirm the SAR transit timing and keep the northern segment clear until the helicopter has passed.
3. At 10:02 the link fails completely and the aircraft does not return. Outline your immediate actions and the information you must be able to produce afterward.
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Immediate actions: announce the lost link on the tower frequency and state the last known position, altitude, heading and the aircraft's autonomous behavior. Activate the visual observer to scan the last known position and the predicted drift track. Notify the operator's safety manager and, if the aircraft is over or near a populated area or the aerodrome, request that the tower alert emergency services. Do not launch a second aircraft into the same airspace without coordination.
Because the wind is 18 gusting 26 kt from the northwest, the aircraft will drift southeast if it is not holding position. I would plot a drift cone from the last known position and brief the observer to search that cone, prioritizing the downwind edge.
Afterward I must be able to produce: the flight authorization and its conditions, the pre-flight risk assessment, the aircraft registration and airworthiness documentation, the remote pilot licence and medical fitness evidence, the maintenance and battery logs, the link budget and RSSI record, the recorded telemetry and the lost-link procedure, the deconfliction coordination with the tower, and a written occurrence report. The report should state the facts, the sequence, the decisions taken and the corrective actions, without speculation about cause. I would also preserve the data before any firmware update or log overwrite.