Determining your minimum opening altitude

Determining a minimum opening altitude is an important decision that every jumper should make, but it’s not as simple as looking at USPA’s Basic Safety Requirements or other national organizations’ regulations. Over the last decade, an average of two jumpers per year have died after their automatic activation devices activated their reserve parachutes at altitudes insufficient for full reserve deployment. With an estimated 200 to 300 actual AAD saves per year, chances are greater than 99 percent that an AAD will fire in time to save the life of a jumper who has failed to activate a parachute. However, close to one in 100 do not survive because the reserve did not fully open above ground level. It is likely that many of these fatalities could have been avoided if the jumpers had used higher AAD-activation-altitude settings.

Both Airtec CYPRES and Advanced Aerospace Designs Vigil AADs have the capability for users to set activation altitudes that are higher than the factory settings. To determine whether you should alter your AAD activation altitude, assess four critical altitudes for each jump:

  1. Your planned main-parachute-deployment altitude
  2. Your minimum main-parachute-deployment altitude
  3. Your minimum cutaway altitude
  4. Your minimum reserve-deployment altitude (AAD-activation altitude)

Your minimum altitudes will change as your equipment changes and will vary depending on your vertical speed when deploying. To arrive at your planned main-deployment, minimum main-deployment, cutaway and reserve-deployment altitudes, you need to calculate from the ground up.

Minimum Reserve-Deployment Altitude (AAD Setting)
If you have an AAD activation, how much altitude do you want to have under canopy to prepare to land? Can you land your reserve with no flare and not get hurt? Do you want to be able to unstow your brakes and let the canopy build up some speed for a flare? Do you want to be able to turn into the wind or have a chance to avoid obstacles? You should know how much altitude it takes after opening to land your reserve safely. At the lowest AAD settings, you may not have enough time to maneuver the canopy into a clear area, set up an approach or get a good, flared landing. This alone could be a good reason to raise your AAD setting to around 1,000 feet above ground level or more.

While the factory settings of the Sport CYPRES (750 feet AGL) and the Sport Vigil II (840 feet AGL) are high enough to prevent a fatality in the vast majority of cases, in some cases the reserve deployment process takes more altitude than available. These longer deployments could have a number of causes. Keep in mind that with freefall speeds of 200 feet per second, a one-second hesitation between the AAD activation and reserve inflation could become fatal. It’s likely that some recent deaths could have been prevented if the AADs had been set to activate closer to or even higher than 1,000 feet AGL. Do you really want your AAD set so close to the edge that a one-second pilot-chute hesitation will be the difference between life and death?

It’s important to keep in mind that your AAD-activation-altitude setting is a minimum activation-altitude setting. According to both CYPRES and Vigil, your AAD unit could fire up to 260 feet higher than the setting depending on circumstances such as your body position. That means that with their factory settings, CYPRES and Vigil AADs may open as high as 1,010 and 1,100 feet, respectively. If you raise your AAD activation altitude to 1,000 feet AGL, your AAD could fire as high as 1,260 feet AGL.

Minimum Cutaway Altitude
How much altitude do you need to perform your emergency procedures? There are a few factors to consider when determining this number. Do you want to leave yourself time between cutting away and pulling the reserve to get in a stable belly-to-earth orientation? How much altitude do you want to set aside for unforeseen circumstances? What if you reach for your cutaway handle and also get a handful of jumpsuit? What if you have a hard time breaking the Velcro loose or pulling the handle? What if the risers do not release immediately? Could you handle these situations in two, three or four seconds? Once you have determined how much altitude you want for your EPs, you can then calculate your minimum deployment altitude.

Minimum Main-Deployment Altitude
When determining your minimum deployment altitude, consider the following: How long does your canopy snivel? After that, how long will it take you to decide whether to keep your main parachute or cut it away? If you have a small, high-performance canopy, you could be losing altitude very quickly in a malfunction. Will you fight the malfunction or cut away immediately?

Let’s take a look at an example. Jumper Joe has his AAD set to activate at 750 feet AGL, meaning that the AAD could fire as high as 1,010 feet AGL. He believes this AAD setting leaves him enough time to find a clear landing area and flare under his large reserve. Jumper Joe wants at least 500 feet to perform his emergency procedures and account for any unforeseen circumstances such as a hard pull. His canopy usually snivels for about 600 feet. If he has a malfunction, he wants to leave himself enough altitude to at least assess the situation and make one attempt to solve it. He will leave himself 400 feet to do this. By adding these altitudes together, Jumper Joe can determine that his minimum main-deployment altitude is 2,510 feet AGL.

These altitudes are constantly in flux and you must re-evaluate them for every condition, including your canopy size and type, experience level and the location where you’re jumping. (Are you jumping in the desert, or are you surrounded by 100-foot-tall trees?) If you decide to change one altitude, it will affect the other altitudes. For instance, if you change your AAD-activation setting from 750 feet to 1,000 feet AGL, every other altitude would have to bump up by 250 feet. Failure to raise these other altitudes could result in having two canopies out, increasing your chance of injury or death.

Planned Main-Deployment Altitude
In any case, it’s important to give yourself a buffer between your minimum opening altitude and your planned opening altitude. What happens if the ripcord or pilot-chute handle is not exactly where you thought it would be and it takes you a second or two to find it? Experienced jumpers should have at least a 500-foot safety buffer here. So, if Jumper Joe’s minimum deployment altitude is 2,510 feet, his lowest planned deployment altitude should be no lower than 3,010 feet AGL.

Even though AADs have a very impressive safety record over the years, it is the responsibility of all jumpers to ensure that they are maximizing their safety margins. All jumpers must carefully consider their planned main-deployment altitude, minimum main-deployment altitude, minimum cutaway altitude and minimum reserve-activation altitude for their particular situations. These decisions could make the difference between life and death.

About the Author
Bill Coe, D-6657, began skydiving in 1976 and received a Bachelor of Science degree in aviation technology from Embry-Riddle Aeronautical University in 1981. Shortly thereafter, he founded Performance Designs with the primary goal of improving ram-air canopies.

Comments

Post new comment

Please provide your full name. We will not post responses from anonymous sources.
The content of this field is kept private and will not be shown publicly.
Type the characters you see in this picture. (verify using audio)
Type the characters you see in the picture above; if you can't read them, submit the form and a new image will be generated. Not case sensitive.