You probably have one meaningful interaction with your AAD: you chase the red light.
Poke, poke, poke, watch. ...Zero. Okay. Off you go.
Just a quick note, friend: you might want to poke a little deeper. According to the USPA, there have been no less than nine fatalities related to AAD fires at designated firing altitudes that did not result in fully inflated canopies before impact. The point is that these guys chased the red light just fine, but there was likely a difference between what the AAD was told to do and the actual conditions of the jump. A couple hundred extra feet could have made the difference between nine annoying repacks and nine funerals.
Food for thought, y’know.
If your equipment is new-ish, your AAD probably has a feature that allows you to change its activation altitude. It’s good to know that feature exists, and it’s good to know how it works -- because it helps you understand that mysterious little whatsit in your rig a little better when you do.
If you’re ready to explore, do a little introspection first. Here are the important questions to ask yourself before you change the activation altitude on your AAD:
1.Do you want this to be forever, or just-for-now?
Most currently manufactured automatic activation devices let you offset the device’s activation altitude to allow for a one-time altitude differential between takeoff and landing area. This will be a factor for you only if you’re making a single wahoo at a dropzone with a significant altitude differential between takeoff and LZ -- or if you’re doing a demo jump with an offset. This method resets when the device turns off.
If you need a change that sticks around a little longer, don’t despair: both the Cypres 2 and Vigil 2+ have a way to increase the activation altitude until you change it back again. Your owner’s manual will explain how to do this.
2. What’s the difference?
The Cypres 2 adjusts in increments of 100 feet, from 750 up to 1,650. The Vigil adjusts in 150-foot increments. For example, if you have a Cypres you’ll add increments +100 feet for a higher landing zone compared to the take-off and increments of -100 feet for a lower landing zone.
3. When’s it going to give the all-clear?
When you make a positive altitude correction, the AAD will still disarm at its standard number of feet above the ground zero reference -- the exact same altitude as it does when no altitude correction is set. When a negative altitude correction is applied, however, it will disarm at its standard number of feet above the preset negative altitude correction -- the new landing zone.
4. How forgetful are you?
If you’re the type of person to run into sliding glass doors at full clip, wear your shirt inside-out all day and/or infuriate your spouse/partner/lover by brainfarting every single anniversary, beware: Adjusting the activation altitude on your AAD might not be the best idea for total space cadets. To avoid a two-out, you’re going to need to remember that setting and ensure that you’ve got an open, functional main no lower than 1000 feet above it.
Remember: a slow opening messes with that margin. Think about density altitude, and think about your packing choices.
Another liability for nutty professors: turning on your AAD in the landing area of one dropzone and driving to another dropzone with a different altitude without resetting the AAD. (Work out how much of a kerfuffle that could be.)
Finally, balance your know-how with your need. Bryan Burke, Skydive Arizona S&TA; (and über-adventuring renaissance man) has this to say about it: “I’m willing to bet that, for most skydivers, messing around with an AAD is likely to cause more problems than it’s going to solve.”
5. Which way are you pointing your belly button?
You may be surprised to know that your body position directly affects your AAD’s activation altitude. AADs work using the metrics of measured air pressure and measured time. Those two parameters allow the little guy to calculate your pretty-much-exact altitude (±3 feet or so) at any given moment as a function of the registered air pressure, as well as your vertical speed related to a pressure variation within a certain period of time.
But wait! Does that air pressure change depending on where your body has oriented that little AAD? Why, yes. Yes it does, smartypants.
A belly position puts your AAD in a burble. This changes the atmospheric air pressure registered by your AAD by up to 10 millibars. Interestingly, that works out to a difference of ±260 feet. In an AAD activation scenario, 260 feet is y’know kindof a big deal. The AAD senses that the belly-to-earth jumper is higher than they actually are -- kinda like a policeman working the exit road of a music festival. Be aware.
6. Why do you even have this little gadget?
If you have an AAD in order to make your skydiving life painlessly safer, you need to know that it’s not the foolproof set-it-and-forget-it piece of furniture you might think it is. You put so much faith in that thing that you really ought to get to know it a little better. There will, after all, likely be a fatality number ten...and it doesn’t have to be you.