Two audibles: altitude awareness at freefly speeds

Freefly changes the altitude problem in two ways. You have less working time than on a belly jump, and an audible can fail without making a sound. So altitude awareness in freefly is built on backups: two audibles, tones you know, and a visual altimeter.

Less working time

Vertical fall rates are high. The APF Freefly and Angles Guide puts head-up at about 220–260 km/h and head-down from about 270 to well past 400 km/h. The figures come from different sources, so compare them loosely. Either way the ground arrives sooner.

Working time shrinks with it. From about 13,000 ft a freefly jump can be around 20 seconds shorter than the same belly jump. Head-down working time can be 35–45 seconds, against about 60 on your belly.

Check your altitude between manoeuvres, or at least every 5 seconds. At those speeds a few missed checks cost a lot of altitude.

Why two audibles

An audible can go flat, be set wrong, or just not sound. Nothing in freefall tells you it has failed.

In a group there is a backup of sorts: if you miss your alarm, you may see the others break off and follow them. On a jump on your own there is nobody to see. So wear two working audibles on any freefly jump on your own.

Treat the group backup as a bonus. Nobody in the group is watching your altitude for you, and “someone will break off and I’ll follow” fails when everyone on the jump is thinking it. Set and check your own audibles to the full standard, on a jump on your own or on a 50-way.

Where you can, use two different models, or at least two devices with different battery ages. A single cause, such as a firmware fault or a cold battery, is then less likely to silence both at once.

Learn each alarm’s tone until you know it without thinking. Two alarms are little help if you can’t tell which one you are hearing. Before any deployment you didn’t plan, confirm on your visual altimeter.

The Australian Skydiver Magazine (issue 111) reports a flyer who believed a low hard-deck alarm had sounded at around 8,000 ft. The flyer flipped and deployed straight away, and another jumper close above had to make an evasive move.

Setting audibles for the jump

On an angle jump, everyone sets their audibles to the briefed breakoff, so the whole group hears the alarm at the same moment.

On a staged big-way breakoff, the setting is personal. Set your audibles to your own wave’s altitudes. One mis-set audible puts that flyer in the wrong wave and undoes the staged plan.

A head-down two-stage plan might, for example, break off the stingers at 6,500 ft to deploy at 5,000 ft, and the base at 5,500 ft to deploy at 4,000 ft. That gives each wave 1,500 ft. Your audible only helps if it matches the wave you are in.

What to wear

• A visual altimeter.
• A working audible, and a second one for any jump on your own. Two is good practice on every freefly jump.
• An AAD.

In Australia, the APF Operational Regulations require a working audible on every freefly jump. A visual altimeter with coloured altitude bands gives you another quick read of where you are through the whole freefall.

Deploying at freefly speed causes hard openings and diving line twists. The Australian Skydiver Magazine (issue 109) found these made up a large share of malfunctions in one 2022 quarter. Slow down and get symmetrical before you pitch.

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Advisory, educational content. All altitudes are guides. Comply with your federation’s rules and your drop zone’s policies, and treat altitude awareness as your own responsibility.