Water Tower Inside a Class D Control Zone: Clearance, NOTAM, and a Dead Radio

Airspace. A Class D control zone is controlled airspace. Operating an RPAS in it requires two-way radio communication and an ATC clearance - you now hold a clearance with limits attached. Class D does not impose a transponder requirement, which is why this is workable with a small RPA.

Second authority. The aerodrome operator's published guidance asking for 24 hours' notice is a separate requirement from the ATC clearance. If you have not given notice, that is a coordination item to resolve before launch, not after. Also confirm with the operator whether their RPAS guidance restricts the lot you intend to use.

The NOTAM. CYA123 is Class F advisory, not restricted - it is not an absolute prohibition - but an active parachute drop is a hard hazard: descending jumpers under canopy and a jump aircraft climbing and descending through your block. Your site is 1.2 NM southwest, the drop zone 2 NM east, so the site itself may be clear, but the jump aircraft's flight paths and the wind drift of canopies are not obviously clear of your window. Action: ask Tower where the drop aircraft is operating and whether the drop will overlap 1500–1600Z. If there is any overlap in space or time, move the window. If it were a CYR (restricted) area rather than a CYA, the answer would simply be no.

On site. With a highway 400 m away, set the geofence so a lost-link or drift event cannot carry the aircraft over traffic, and identify a sterile emergency landing area before launch.

Initial call (elements: who you are calling, who you are, where you are, what you want, altitude block, time window, how you are listening):

"Tower, RPAS C-XXXX, one point two miles southwest of the runway two-seven threshold, request clearance to operate within the control zone, surface to three hundred feet AGL, one-five-zero-zero to one-six-zero-zero Zulu, listening one-one-eight-decimal-seven."

Use the registered mark or the callsign Tower assigns. Keep the transmission short and use standard numbers ("one point two", "three hundred", "one-five-zero-zero Zulu").

Readback of the clearance:

"Cleared to operate within the control zone, surface to three hundred feet AGL, remaining west of the extended centreline, will report on station, RPAS C-XXXX."

Why these items. Read back every clearance, and specifically: the altitude limit (300 ft AGL), the lateral restriction, any frequency instruction, and any report the controller requires ("report on station"). Those are the items where a misheard word puts you in the wrong place. Never answer a clearance with a bare "roger" or "wilco" - a clearance must be repeated. If the controller amends the clearance mid-flight, read the amendment back before complying.

Losing the radio means losing the clearance, because the clearance was granted on the basis of two-way communication. The operation ends.

Priority order:

1. Regain control of the aircraft's position first - hold clear of the extended centreline and away from the highway, using the geofence and your planned recovery route.
2. Land normally and promptly at the surveyed recovery area, not over traffic and not in the parking area where people are working.
3. Do not attempt to "finish the orbit" while you still have the aircraft in sight. The clearance is void the moment communication fails, and continuing puts you inside Class D with no authorization.
4. Once on the ground, phone the Tower on the published administrative number, tell them the RPAS is on the ground and the operation is terminated, and ask whether they want anything further.
5. Log it and note the cause (frequency congestion, terrain shielding, radio failure) - if it was equipment, no further flights until fixed.

Judgement point: the temptation is to treat a garbled transmission as a temporary nuisance. It is a loss of the condition on which your entire authority to be in that airspace rests. Land, then talk.