Three Point Eight Kilometres from the Aerodrome Reference Point
You are RPIC for a 12.5 kg multirotor flying a 60-hectare photogrammetry mission over a sugarcane estate. The estate's north-west corner lies 3.8 km from the aerodrome reference point of a provincial airport whose control zone has a 5 NM radius; the northern boundary sits under the departure centreline for runway 04. Your planned block altitude is 110 m AGL. You hold a valid RPAOC and the aircraft is registered. The tower controller, reached on the published number, says: 'RPAS activity inside the control zone requires prior coordination; call again in 30 minutes.' A NOTAM is active for parachute dropping between 14:00 and 16:00 local, 2 NM east of the airport, on your side of the field. It is 13:05, you have about 70 minutes of usable light, and the client's agronomist insists the flight must happen today because the next available slot is after harvest.
1. Explain what airspace you are proposing to enter and what the tower's 30-minute deferral does and does not mean. What should you have ready before you call back?
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The airspace
The estate corner is inside the airport's control zone, so the flight is in controlled airspace and requires ATC coordination, not merely a courtesy call. Being under the departure centreline for runway 04 adds a second hazard: departing traffic climbs through your block shortly after rotation, and wake turbulence from a departing turboprop or jet can be violent at low level even where the aircraft is nowhere near you.
What the deferral means
It is not a clearance and it is not a refusal. It means the controller is busy and has not yet assessed your request. Critically, it does not authorise you to start flying while you wait, and it does not shorten the coordination requirement. Do not launch a 'quick partial' mission in the meantime on the assumption that the tower will say yes.
Prepare before calling back
- A map with the operating boundary, distances and bearings from the aerodrome reference point, and the coordinates of the launch point.
- Maximum altitude (110 m, about 361 ft) and the exact time window requested, with an end time that respects your light limit.
- Aircraft type, mass, registration and your pilot certificate details.
- Lost-link and abort procedure, including the failsafe altitude, ready to state on request.
- A note that the parachute NOTAM may conflict: ask the controller whether the drop area overlaps your north-east corner and whether the drops are running.
Call back at the stated time with all of that in one pass. Controllers appreciate a request they can answer in fifteen seconds.
2. Write out how you would structure the call-back, and describe your options if the controller replies 'unable due traffic'.
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Call structure (keep it short, then read back)
- Who is calling and who is being called: 'Provincial Tower, this is RPAS Alpha-One.'
- Your position relative to a known point they use: 'Three point eight kilometres north-west of the aerodrome reference point.'
- What you want: 'Request operations in the control zone, surface to one hundred and ten metres AGL, from one-three-two-zero to one-four-two-zero local, within one kilometre of my position.'
- What you will do if it goes wrong: 'Lost link procedure is return to home at sixty metres, abort on request.'
- Read back the clearance or the refusal verbatim, including any altitude or area restriction.
If 'unable due traffic'
- Do not enter the control zone. A refusal is a firm boundary.
- Ask a useful question: 'Is the restriction area-based or time-based?' If a later slot is offered, and it fits your light limit and battery plan, take it; if not, decline politely.
- Re-plan on the ground: fly only the portion of the estate that is genuinely outside the 5 NM boundary, which is likely to be a small southern strip and may not be worth the setup.
- Consider relocating the launch point further south for tomorrow's mission, rescheduled and coordinated in advance, rather than improvising today.
Note the compounding factor: between 14:00 and 16:00 the parachute drop also closes the eastern side. Even a permissive tower answer at 13:35 gives you a hard stop, and your 70-minute window is already shorter than it looks.
3. The controller clears you but with the condition 'remain below 200 feet AGL and clear of the approach'. Your survey block is 110 m. What do you do, and what must change on the aircraft before you launch?
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First, translate the clearance. 200 ft is about 61 m. Your planned 110 m is nearly double that. The clearance is a limit, not a target, and 'clear of the approach' is a moving boundary as traffic arrives.
Assess feasibility honestly. Flying at 61 m instead of 110 m cuts the ground sample distance the wrong way, narrows the swath, and roughly doubles the number of lines and the flight time. In a 70-minute window with a light deadline, the full 60 hectares is probably not achievable. Decide now, on the ground, whether a partial block at the cleared altitude is worth it. If it is not, decline the clearance and say so; that is far safer than taking it and pushing.
Reconfigure before launch. The critical item is the failsafe. If the RTH altitude is still set to 120 m, a lost link will command the aircraft to climb to double the cleared altitude and bust the restriction inside controlled airspace. Lower the RTH and lost-link altitude to a value that respects 61 m and the local obstacles, and confirm it on the ground with a link-loss test if the system supports one.
Also set a geofence ceiling at the cleared altitude, brief the observer to call inbound traffic immediately, and define abort criteria: any aircraft on approach, any instruction from the tower, any link anomaly. Land and call the tower back.