Dan'sMagic 9: Understanding the Game
4-way competition explained from first principles...
Cypres, the ground-breaking AAD for experienced jumpers was introduced more than 25 years ago. At the time the activation altitude was set at 750 feet, about 4 seconds from impact. This was basically the last possible moment to give time for the reserve to deploy.
Cypres had to assume the worst-case scenarios when figuring out whether a given jump is a low-pull or a no-pull. The last thing any AAD manufacturer wants is to open the reserve just as a main was about to appear – two canopies out simultaneously is a very dangerous situation.
Imagine a skydiver in 2010. She intends to stick to the then USPA rules of ‘initiating deployment’ by 2,000ft’. She sees someone else when flaring out of her track and sucks it down a bit. She has a slight pilot chute hesitation and an unusually slow opening. It’s easy to imagine that she’s roaring through 1,100ft with nothing useful out yet. She’s dangerously low – but she hasn’t really broken any rules, and she doesn’t want her reserve to be released automatically. It’s easy to see why Cypres chose 750 feet, and later manufacturers mostly followed suit.
When the first Vigil units were released, in 2003, the activation altitude was set at 750 feet, the company later raised its firing altitude to [an average of] roughly 850 feet. The first Vigil units included an option for the user to change the activation altitude; this could be used to land at a DZ with different elevation to the take-off zone, or to manually adjust the AAD firing height higher. In 2013, Cypres introduced an option to increase activation height (here). In the Vigil and the Cypres, these settings are permanent; you adjust the setting once, and don’t have to touch it again until you change the battery in your AAD.
The Mars AAD activates at 885 feet and has an option (like Cypres & Vigil) to change the firing altitude for individual jumps, due to different elevation of take-off and landing zones – but not to amend it permanently. It has to be re-set every jump, which is not really practical.
In the last 15 years there has been an average in the US of almost one fatality a year where an AAD activated the jumper’s reserve but it did not fully open before impact
The downside of leaving deployment to 750 feet is that in more recent years sometimes it’s been too late. In the last 15 years there has been an average in the US of almost one fatality a year where an AAD activated the jumper’s reserve but it did not fully open before impact*. The only antidote to this nightmare scenario seems to be to raise firing altitude. Some jumpers may still be pulling low now and then. But if you’re not one of those - does it not make sense to raise the initiation altitude of your AAD accordingly?
*(Note, the above should be compared with a conservatively estimated 400+ total AAD Saves in the US in a similar time period)
Many parameters have changed since the first Cypres was introduced. Containers have become smaller and more tightly packed. We deploy higher, our canopies take more altitude to open, and they lose more height in a malfunction. Freeflyers have greater wind speeds than belly flying, so burn through altitude if they lose awareness.
If you jump at a dropzone with a variation in surrounding altitude (eg, a valley, or beach next to cliffs) a difference in exit point could put you with insufficient altitude to open the reserve.
a difference in exit point could put you with insufficient altitude to open the reserve
USPA discussed with the PIA Technical Committee a series of 9 fatalities where jumpers impacted without a fully open reserve, after AAD activation. These were dubbed LROs (Low Reserve Openings – a bit of a misnomer, they’re actually Low Reserve NON-Openings). In March 2010 they released a Skydiver Advisory (here, page 9), which recommended that jumpers review their decision altitudes and consider deploying higher than the recommended minimum of 2,000 feet.
In 2014, USPA raised its minimum opening altitudes from 2,000 feet to 2,500 feet, a move copied by most of the world. The BPA raised minimum openings to 3,000 feet, which has been standard in France for many years. Yet, how many of us made a conscious change in our critical activation altitudes? With opening at least 500 feet higher, we could reasonably raise our AAD firing altitude by 100 to 400 feet and build a bigger margin of safety at the bottom end, without affecting the top end (provided we are vigilant).
Six years of investigations into LROs by the PIA Committee produced a report (here), that considered 6 possible LRO factors:
Despite extensive investigations the committee was unable to establish equipment-related causes (A, B, D, E) and was therefore only able to make recommendations relating to C and F.
“Over the last six years of discussion, committee deliberation, bench testing, development of customized load sensors, live testing and the combined efforts of some of the brightest contributors to our industry in modern times, the Committee Members have yet to locate evidence that supports or indicates a systemic or specific equipment design issue.” PIA Technical Committee
A – AAD and Harness/Container interface B – AAD initiated deployment sequence is different to manual activation…
A rig assembled with the incorrect loop length (too long) is an issue, yet we see a worrying trend in the field of loop lengths getting longer and longer. If a rigger packs a reserve and it registers too high on the 22lb pull test a common ‘solution’ is to lengthen the loop – but this brings its own problems. If the loop is too long it can be slow to clear the flaps, if it clears at all. Proper tension is very important.
Deploying the reserve by cutting the loop is a different initiation to open the reserve container, compared to pulling the pin via the reserve ripcord or MARD. The pin is situated on the top flap of the reserve, releasing the pressure for a faster deployment. On the other hand, the AAD cutter is in some containers (but not all) placed at the bottom of the rig/pilot chute. If the AAD fires, it cuts the bottom of the loop. This leaves most of the loop in place – and that (often long remaining loop) may have to snake its way out through the grommets in the flaps for the pilot chute to launch. The problem is compounded if the pilot chute adds pressure from below, jamming the loop against the grommets. If the loop is too long and the grommets are not perfectly aligned above each other it can create a hesitation of a second or more, necessary to initiate the reserve opening in time.
For this reason, CYPRES recommends the cutter is placed above the reserve pilot chute, on containers with internal pilot chutes. Similarly, Cypres recommends lubricating the reserve loop with manufacturer’s silicon, to assist the remainder of the loop to clear the grommets from the inside of the container, after an AAD fire.
All the above could take fractionally longer than a manual deployment – especially when combined with other factors such as Cause D, Restrictive reserve container and/or Cause E, insufficient reserve pilot chute drag. Raising AAD activation altitude gives more time in case many factors align to slow down the opening. The majority of LRO fatalities had a reserve beginning to inflate on impact; there was not enough time for complete inflation.
An eyewitness account (from a very experienced, highly qualified person) of an AAD firing just before the jumper pulled the reserve handle reported that the reserve pilot chute did not appear until after the jumper pulled the handle. This supports the theory that AAD initiated deployment is different (slower) to pulling the pin.
Cause C, AAD Activation Altitude not Sufficient The committee agreed that raising AAD firing altitudes was a logical step to provide an extra margin of safety to offset unplanned variables.
Cause F, Burble The report’s recommendations for cause F were to reinforce the advice in USPA’s SIM: after deploying the reserve, look over your shoulder or be head-high, to help the reserve pilot chute launch into clean air. You can’t do this if you’re unconscious! This is one of the main reasons many skydivers wear an AAD. The burble problem would probably not exist if unconscious – but it still seems the only realistic preventive measure in this AAD firing scenario is to address Cause C by raising activation height.
USPA stated many possible contributory factors to LROs (below). Like most incidents in skydiving, there is probably no single cause, but instead a chain of events. It’s virtually impossible to eliminate them all but stopping one link in the chain can prevent catastrophe.
“Possible factors may include, but are not limited to, body position of the jumper, the reserve pilot chute getting caught in the burble, inhibitory actions by the jumper, entanglement with the jumper or other equipment, condition of the container and reserve components, exact combination of components utilized, fit of the reserve canopy in the container, AAD setting or functionality, reserve packing methods, container design and reserve pilot chute spring strength, as well as various combinations of these factors and other factors that have yet to be determined.” USPA/PIA Advisory, 2010
It’s virtually impossible to eliminate all the links in the chain but breaking just one can prevent catastrophe
So, six years of testing with the brightest and best brains in the industry resulted in the advice to raise AAD firing altitudes. Food for thought?
For me, I’m going to make that change.
You must be 100% certain you change the altitude correctly, as the consequences of an error could be fatal. NB: The Vigil permanent adjustment allows you to set the activation higher or lower (in case of landing at a DZ of lower altitude than taking off). This software design allows you to kill yourself if you get it wrong. By contrast, the Cypres permanent altitude adjustment only allows you to set the activation altitude higher. If you elect to change your activation altitude, refer to the Owner’s Manual AND check with a rigger. You must pay close attention to your opening altitude (as always) and revisit your hard decks for decision-making and EPs.
If you find yourself sometimes opening lower than the recommended height, an upward change could put you at risk of a 2-canopy out situation.
Like everything to do with your safety, it’s a personal decision with no single easy answer. It is each jumper’s responsibility to have a fully open main canopy well above activation altitude. The Vigil Manual (page 16) recommends allowing approximately 1,000 feet between a fully open main canopy and the activation altitude. The Cypres Manual does not make any recommendation on altitude, but includes instructions on changing activation altitude (pages 30-33). If you elect to make any change, get a second, qualified person to watch the procedure as a double check.
Do not rely on AADs to save your life. They don’t care as much as you!
NB This article does not constitute advice; it raises points for experienced skydivers to carefully consider, and make their own decisions.