Amateur Radio High-Altitude Balloons: Know the CASA Requirements Before You Launch

High-altitude ballooning provides amateur radio clubs and experimenters with a fascinating platform for radio telemetry, propagation experiments, APRS and position tracking, digital communications, imaging and STEM activities. A small payload suspended beneath a balloon can become a flying radio laboratory reaching tens of kilometres above the Earth.

But before releasing one in Australia, there is another piece of equipment required: a flight plan that complies with CASA requirements.
The Civil Aviation Safety Authority has updated its guidance for uncrewed free balloons, including the small and light balloon categories most likely to be relevant to amateur radio and educational balloon projects. CASA defines an uncrewed free balloon as an aircraft that is lighter than air, carries no pilot or passengers and is not tethered to the ground. CASA specifically identifies education projects and hobby activities such as communications and high-altitude photography among their common uses.

Small and Light Balloons Are Still Aircraft

CASA divides uncrewed free balloons into small, light, medium and heavy categories, based on characteristics including balloon size, payload and attachment specifications. The detailed regulatory requirements are contained in CASR Part 101, particularly Subpart 101.E.

For an amateur radio club considering a small or light balloon carrying a transmitter, tracker, telemetry package, camera or experimental radio payload, an important message from CASA is simple: contact CASA before releasing a balloon of any size.
CASA asks operators to use its Sport Aviation Rules Enquiry Form so it can determine whether an area approval is required. Even where an area approval is not required, CASA says operators must still contact it with basic information so that a NOTAM can be published.

An area approval is required in circumstances including a balloon operating above 400 feet AGL in controlled airspace, beyond visual line of sight, in cloud, at night or outside Visual Meteorological Conditions. CASA advises that non-complex approvals can take up to 30 business days, so contacting them the night before launch is unlikely to produce the sort of rapid response we normally hope for.

Planning an Amateur Radio Balloon Flight

For small and light balloons, CASA says an application requires an application form, risk assessment, photographs of the payload, parachute and balloon-to-payload connection, a high-altitude balloon prediction showing the expected flight path and landing area, images of the release site and written permission from the landowner.

Flight prediction is particularly important. Operators must estimate the balloon's direction, distance travelled, maximum altitude and expected landing area. CASA identifies tools including Habhub, Balloon Flight Predictor 2 and NOAA's HYSPLIT Trajectory Model as possible prediction resources. Once approval has been received, CASA says the release should proceed only if the actual wind direction matches the prediction assessed in the application.

The release site itself also matters. CASA recommends an open, flat location with minimal obstructions, with landowner permission, and advises operators to avoid busy aerodromes, high aircraft traffic areas, helicopter landing sites and heavily populated areas. Additional permissions can apply around aerodromes, runways, approach and departure paths and restricted areas.

Keep the Payload Light and Safe

There is also practical guidance that should interest anyone constructing an amateur radio payload. CASA recommends using soft materials such as foam, balsawood and plastics. For small and light balloons, it advises avoiding dense packages and hard materials including metal, layered fibreglass and carbon fibre.

That presents an interesting engineering challenge for radio amateurs: build something light, mechanically safe, thermally capable of surviving the upper atmosphere and still able to support the antenna, batteries, transmitter, sensors and tracking system.

Amateur radio high-altitude balloon projects can be superb club and STEM activities. They combine electronics, radio communications, antennas, telemetry, software, atmospheric science, navigation and recovery into one project. But the balloon shares Australian airspace with other aircraft, so CASA requirements need to be part of the project from the beginning, not something considered once the balloon is already inflated.

Radio amateurs also need to ensure that any amateur radio transmitter and its operation comply with the separate requirements applying to the Australian Amateur Radio Class Licence.

For anyone contemplating an amateur-radio balloon project, start with the CASA guidance and contact
CASA well before the proposed launch date.

CASA: Approval to release an uncrewed free balloon - Link

Page Last Updated: Sunday, 27 Sep 2026 at 21:30 hours by Justin Giles-clark

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