throwaway456789

The problem with an option like that would be that the unit can be turned off by accident. AAD manufacturers create their products having to counterbalance two major risks caused by malfunctions: 1. AAD firing when it should not fire vs. 2. AAD not firing when it should fire While in my opininion (and I think I am not alone with it) malfunction #1 is much worse than #2 (saying I will prefer an AAD that does not fire at all and accept an accidental shutdown to one that fires when it should not), manufacturers try to keep the functionalty of the AAD under all circumstances and will accept an accidental fire. As already said - from a technical and safety point of view this doesn't make sense to me. From a marketing and PR point of view it makes a lot of sense. Imagine the uproar that would go through the skydiving community if an AAD did not fire at all even though it was switched on correctly? The typical "The unit functioned as it was designed" would not count anymore then. An unintended fire from time to time is not that difficult to handle. The manufacturer can always blame the skydiver on using a unit although it was known in before that limits could have been exceeded. You cannot do that, when an AAD was not to fire at all. Imagine all the skydivers/customers running away from that specific AAD brand, to switch to one that has not yet failed to activate. Imagine all the money that an AAD manufacturer would loose. If you look into the Cypres patent I posted before you can see, that the AAD actually knows when the canopy is open. It would be easy to shut it down as soon as this happened but of course you run the risk to accidently shut down if you missdetect a canopy opening or in case of a cutaway. The same goes about a manual off-switch, even though this is less likely to happen. So while I fully support your idea of an AAD the switches off as soon as the canopy is open, I do not think that any of the current manufacturers is ever going to sell something like this due to the high image and marketing risk.

The Cypres in this video (https://www.youtube.com/watch?v=pLqaMGIqWe4) was a standard version - anyways, also the standard version is not supposed to fire below 130ft. I think it is pretty clear, that the activation altitude seen was well below 130ft - so how much are you going to trust in the parameters set in the Cypres? I work as an engineer and design safety systems for different machinery. To be clear - if the system I (or my company) design fails, people are very likely to die. And because of this there are very strict rules and standards to be satisified. For example a risk exceeding a certain level will require the whole control system to be built redundantly. That means two sensors, to measure a value, two control/logic units to process the values and two actor/output units to initiate a certain action/reaction. Failures in each of the subcomponents must not cause a dangerous failure and should be detected. I looked up the patent that describes the functionality of the Cypres unit (http://www.google.com/patents/US5825667) and did not really like what I saw. While there are two sensors (acceleration and pressure) to calculate altitude and speed, differing values do not lead to a shutdown of the unit, but to the value beeing calculated as an average. That means one malfunctioning sensor will not directly be detected but distort the measured altitude, which can lead to a fire outside the set limits. Also as far as I have found out, there is only one CPU built inside, giving another single point of failure. The Cypres unit was not constructed in compliance with any of the safety standards applicable to machinery or general safety systems - at least I was not able to find out anything. Nobody knows how the Cypres was constructed, how it was checked for failures and how it was tested. For comparison - certain types of machines (also the ones I work on) have to be checked by an external company in order to ensure proper safety and to eliminate design errors. No external company has ever reviewed Cypres (again - at least I was not able to find any reference on the Cypres homepage). Of course you have to consider the history under real circumstances that shows that the Cypres works very well and a Cypres fire when it should not fire is quite rare. Also given all the AADs on the market, Cypres is definitely the safest unit as it is the only one to rely on two different types of sensors (pressure and acceleration as already mentioned before) - due to the patent Airtec is holding other manufacturers are not allowed to copy this principle. This eliminates the possibility for false fires due to pressure fluctuations and gives a huge advantage to overall safety. (I remember a few incidents when another type of AAD with only pressure sensors fired after the airplane door has been opened during climbing or car doors beeing closed with the rig inside). After all I have to say everybody has to decide for themselfes if they want to use an AAD, but consider that there can be quite some margin on the activation limits set in the units. Not only you might cause a fire by exceeding the limits but also the unit might cause a fire by misinterpreting the measured values. P.S.: Anonymous post because the skydiving world is too small (especially in this case) to leave such a controversial opinion somewhere, where it cannot really be removed forever. I will always stand my opinion in person but have learned to be cautious with what you post on the internet and hope you understand.