Unconscious in freefall? Or injured to the point that you can’t deploy your own main or reserve? It’s the kind of stuff that shows up in skydiving nightmares. Thankfully we have AAD’s that step in when we can’t. Know and understand yours, because your life may depend on it one day.
Many thanks to Tom Noonan, Vigil Sponsored Instructor for this contribution on AAD’s.
Know your gear, including your AAD!
It’s early March, and USPA Safety Day 2014 has just arrived. It’s that one day a year where skydivers around the country take a collective pause from their rides to altitude to evaluate the safety of the sport, and their individual place within those safety margins. Safety Day is a time to reflect on the skydiving disciplines we practice and of course, we dedicate a lot of our time on Safety Day to learning about our gear. We learn about our main parachutes, our reserve parachutes and our harness containers, as those are the big-ticket items, and traditionally that is the gear that we tend to discuss the most. And that makes sense, as canopy collision incidents remain on the rise and equipment maintenance issues continue to be paramount to safe skydiving. That said, one item of gear that seems to escape discussion each year on Safety Day is learning more about our Automatic Activation Devices, otherwise known as our AADs. And why is that?
For over a decade, the first AADs were largely considered to be a “set it and forget it” device. After all, they had only one button to push and they were so convenient, that all you had to do was turn them on……they were so simple to use that they were even designed to turn themselves off! And once you turned them on, all you had to do was throw a quick glance at their LED display to make sure they were still on before each jump and you were ready to go. That was it. Simple. Easy. But that was years ago, and things aren’t so simple anymore.
Today, we are skydiving in a 3-D universe with varying fall rate speeds. We can fall very slow (vertically) in a wingsuit or fall very fast while freeflying on all axis, or fall at any speed in between depending on our jumpsuit selection. Regardless of how slow or fast we fall today however, everyone still has deploy a main parachute at the end of their skydive.
That is common knowledge of course, so what’s the big deal? The issue that we must address today that was not such a big deal a decade or two ago is “How long does it take for our main parachutes to open?” It’s a simple question for sure but you’d be surprised at how many skydivers have an incorrect idea of what they think is the altitude loss on their modern main canopy. Yet, if they go up and actually do a few jumps with the specific focus on determining their altitude loss during deployment, they are surprised to find that they were off by 300-500ft in the wrong direction. If you think your parachute opens in 500ft, it’s probably closer to 800ft, if you think it opens in 800ft, it’s probably closer to 1000ft. Okay then, but why is knowing the altitude loss so important?
Today’s AAD manufacturers are now offering units that allow skydivers to raise their AAD’s deployment height from it’s initial factory setting, and if a jumper elects to raise their AAD activation altitude without first knowing what their altitude loss is on their main canopy, they could be drastically reducing the altitude gap between their main canopy deployment height and their AAD activation altitude. Advanced Aerospace Designs, makers of the Vigil, recommend that you have a minimum of 1000ft between your open main canopy and your Vigil activation altitude to give you the maximum height and time to deal with main parachute malfunctions. So, before you go raising your activation altitude, it’s in your best interest to first establish an accurate height for main canopy altitude loss during deployment.
Another common misunderstanding of AAD activations is what altitude they actually activate at. Both major manufacturers (AAD and Airtec) have different activation heights depending on the burble caused by your body at the time of activation. If you’re in a belly to earth position, Airtec units will activate at approximately 750ft AGL where as Vigil units will activate at approximately 840ft AGL in the same body position. I say approximately, because all AADs use algorithms based on changes in barometric pressures to determine an indicated altitude of the unit at time of activation. It is important to emphasize that indicated altitude and the true altitude may not in fact be the same height. The true 750ft and 840ft could be slightly higher or slight lower depending of the changes in pressure readings, especially if the person is unstable and tumbling in freefall. Okay, so what about this “other” height that AADs can fire at? Both major AADs on the market also can have a higher activation height if the person is falling back to earth, based on the higher pressure readings that falling back to earth will generate. An Airtec unit will fire at approximately 1000ft AGL and a Vigil unit will fire at approximately 1100ft AGL in a back to earth orientation. I keep using the word “approximately” as each unit is continually attempting to calculate an indicated airspeed and altitude based on these changes in pressure. There even exist numerous additional algorithms in this process designed to smooth out the calculations when perpetually unstable body positions occur.
With all the talk lately about raising minimum deployment altitudes for main canopies, it’s important to understand where that movement came from. USPA has always recommended a minimum break away/decision altitude of 1800ft AGL to deal with canopy malfunctions, and with most modern canopies today taking 700ft or more to open, it just makes sense to create a deployment altitude high enough to allow for EPs to be executed with sufficient altitude to let the EPs do their job. An obvious off shoot of that main canopy movement inevitably led to the question, if we are raising main canopy deployment heights, should we then also raise the deployment height of our AADs? While there does not exist any one finite answer to cover every scenario, what is universal is the need for every skydiver to understand the relationship between their main canopy deployment altitude loss and the activation height they elect to set their AAD to.
AAD operational parameters have continued to evolve since their first introduction to the skydiving market. Over the years, as the evolution of our sport has continued to push the limits of human body flight, so too have the AAD manufacturers continued to evolve their products to best adapt to the evolution of skydiving. Many updates and upgrades are known by the end users, yet there still exists numerous upgrades and operating parameters that skydivers are unaware of, and sometimes being unaware of these new parameters can cause the end-user to place the equipment in conditions beyond the intended operating limits of the equipment.
In the end, it is critical to accept that the era of “set it and forget it” AADs is a statement of the past and that modern skydiving, and thus modern skydivers, must dedicate the time and research to understand the complete set of operating parameters that their AAD’s are programmed to operate within. Please visit your AAD manufacturer’s website and read the owner’s manual from cover to cover. If you still have questions, contact your local rigger, local dealer or the manufacturer and get answers. Not knowing your gear, even your AAD, can mean the difference between having a fun uneventful skydive and finding yourself operating outside the limits of your gear.
And remember, every day should be safety day.
Check out the Vigil Life Saving List – first hand accounts from skydivers, so that you may learn and understand.
Tom Noonan works as the Tandem Program Director at UPT, serves on the USPA Board of Directors as a National Director and is well known for his Everest skydiving expeditions.
Check out the entire Get Current 2014 series for more articles and info!