It was essential to avoid electric devices, because of the effects of seawater. The diver had to be able to test the device was working by simple movements. Such a system should be automatic. Indeed, the 'Guardian Angel' should be a device put between the diver's shoulder blades. When he is on the surface, this position would let the system be virtually at atmospheric pressure.

   We opted for a "fluidics" temporization system, that was built and tested successfully. This pre-study cost a lot, so I asked a friend, Albina du Boisrouvray, for help. She had lost her son too, in tragic circumstances; he was nearly the same age as mine. François-Xavier Bagnoud was an helicopter pilot and he became the private pilot of Thierry Sabine, who founded the Paris-Dakar rally. As he was checking out the desert with the singer Daniel Balavoine as passenger, all three died in a crash the cause of which remains a mystery. Grief-stricken, Albina decided to devote her life to charity through a foundation she gave her son's name to. She agreed straight away to finance the built of a prototype. The device drawn (approximately on a 1:1 scale) was so built and tested successfully by the 'Disk' Company, managed by the dynamic Mr Koenig and located at Bourg lez Valence (France). The budget was to cover all the process from the pre-study to the adjusting of the final product, in collaboration with an industrial partner, that was to be found. We all expected that the venture could be seen through to completion. A patent was prepared and I thought it was natural that I should take as agent someone who had dealed with my son's business affairs while he was alive. Jean-Christophe was a brilliant designer of diving equipments. Sadly, it turned out that this woman was a crook of the worst sort who embezzled the most of the money by juggling skilfully the books, as she used to do in the past with several organizations intended for humanitarian activities. This person even foung means to recover a sizable sum, in Italy, claiming she had been appointed as an executor. There are people who could cut a dead person's finger to get back his ring. It's well known that humanitarian activities are one of the favorite targets for crooks, because people are less suspicious. With the sum this person left, we could finish a prototype and test it successfully, but we couldn't go any further. Therefore, we're searching for an industrial partner who may take over the project in his own name. If the sale of those safety devices could bring in some money, I only would like FXB foundation to be compensated for the sum they lost in this affair.

   The trials were about a "baro-temporizer"-working system. We designed it to limit to two minutes (120 seconds) apnea divings; after this period of time, it had to strike automatically a CO₂ cap, that should blow up the two bladders of the jacket and so bring the diver back on the surface. The system was working quite well and repetitively. But now, it's time to describe it. The drawings below match a prototype having the size and the volume of two VHS video tapes sticked one on the other. Of course, the optimized device would have a different shape, more compact, and would be made up of moulded plastic parts. We had built the prototype manufacturing plates in aluminium alloy, just to prove the feasibility.

   Initially (before the dive), the system, that is supposed to be located between the diver's scapulas, is at water level. The external pressure is exerted through the holes shown on the drawings. The system is on contact with the external environment by a rubber membrane similar to those of diving bottles' regulators. This membrane is interdependent with a mobile part (red-colored) that has the rotation symmetry. The system comprises several chambers. We'll call B the upper chamber and D the lower one. In normal circumstances, without high pressure due to the diver's descent, the membrane is flat. The turret, there colored in red, is in the position you can see on the drawing. Its awl isn't engaged and the B chamber communicate with the D one, so they've got the same pressure.

   The yellow color figures an oil filling. A second turret, white-colored on the drawing above, is interdependent with two very soft rubber membranes. This turret is made up of a cylindrical central body, interdependent with the two disks on which the upper and the lower membranes are sticked. A light spring keeps this second mobile part in contact with the upper thrust, through the rubber membrane. No oil leak is possible. The oil can flow out by two ways:
<            - slowly, toward the bottom and along the axle, as a function of the sliding play of this axle in the hole;
            - quickly, toward the top, through the check valve (brown-colored).

   The device is ready to work. As soon as the diver is deeper than one meter, the pressure exerted on the rubber membrane in contact with sea water become strong enough to cause the isolation of the D chamber: the awl of the left mobile part comes into contact with the toric seal.

   The color of the environment is supposed to show the depth. There, we're about at one meter. If the diver goes deeper, only a few more meters, the pressure exerted on the left membrane pushes the left mobile part to its thrust. Look at the drawing below:

   The air contained in the B chamber will be at a slight high pressure (figured by the pinkish coloration) comparatively to the air contained in the D chamber, that "remembers" the value of the atmospheric pressure at the time of the immersion (plus the equivalent of one meter of water, i.e. a tenth of a bar). Thus, the air in the B chamber will press down the upper membrane of the second mobile part (white-colored). It will tend to go down, but it will necessarily have to force some oil out, from the upper part (C) where it is to the lower one. The oil is flowing out along the axle, some play having been loosened during the machining. It's the value of the play itself that dictates the time of temporization.

   The drawing above shows the second mobile part going down. The small arrows show the oil flow. The general design of the system determines the time it will take for the second piston to reach its lower thrust.

   If the diver goes back to the surface before the 120 seconds are up, what's happen ?

   We've drawn the device after the return to the surface. Please note that the countdown goes on until the diver goes back to the surface, or very close to it. That's only at a depth of less than one meter that the left mobile part unblocks the communication between the B and D chambers. The right spring tends the mobile part to go back to its original position. This movement is very quick, because the oil can lift the valve up (look at the drawing).

   But what would have happened if the diver had not reached the surface before the deadline?

   The right mobile part (black-colored) would have met the trigger of a striker (manned with a powerful spring). That's this system (that we did not draw) that strikes a CO₂ cap, which brings the diver back to the surface, face upside, by inflating the two bladders very quickly. The excess of CO₂ is vented through a piercing whistle, that is supposed to warn people and make the diver regain conciousness.
   In order not to overload the drawing, we have showed neither the striking system, nor the one that tests the working of the device: a security pin avoiding any accidental strike of the CO₂ bottle's cap. The diver, on his boat or on the beach, proceeds to the armament of the spring. Then, pressing on a button, he drives the red left mobile part in and holds it in position, simulating a dive. Doing this, he causes the oil flow, the "baro-temporization". With his watch, he can check if the system works well once the deadline is reached. Now he has just to re-man the striker, to take the security pin off and to go diving without worrying about this device. His Guardian Angel watches over him and prevents any dive longer than 120 seconds (but he might change this value, just by adjusting the stroke of the right mobile part before it triggers the striker).

   The system stands up to shocks and corrosion as it is in contact with the sea water only by a rubber membrane. A shock would not lead the right mobile part to trigger the stike accidentally, because of the viscosity of the oil.

   My son invented antoher system, that was interesting too. It could be boarded on every boat. It was light and it had the size of an attaché case. This plastic colored box, easily visible and equiped with an foldable flag, was an air chest that allowed someone to dive at a depth limited by the length of the narghile (20 meters). This system could allow the captain of a yacht or a motorboat dive to free an anchor jammed between two rocks or to take something back, or let the crew members have a look under the sea.

   You may think it's an aqualung. Yes an no.

   As the air chest stays on the surface (diving bottles made in light alloys can float), other people on a boat can watch over the diver. It's working in "semi-apnea". Technically, it's just called an narghile, but psychologically, it allows everyone to dream he's the hero of "The Big Blue". The harness is equiped with the baro-temporizer, that starts automatically to countdown as the diver stops breathing. The device will so be set for shorter deadlines, e.g. 60 seconds.

   One minute without breathing: the striked cap brings the diver back to the surface. But as soon as he "sucks" on his narghile, the countdown is reset.

   I've got a moving thought for my friend Yves Girault, now dead, with whom I drove for my nearly first time. He knew my son very well, and he helped me in the conception and the adjusting of this rescue device.

Reactions

   May, 1st 2000: Benjamin Rottier, 20, wrote to me to suggest an improvement for this rescue system. I hadn't thought of this. We just could add on the harness, e.g. on one of the straps, on the front side, a handle (similar to those opening parachutes). It would be linked to the striking system by a plasticized cable sliding in a duct. By pulling on it, you'll strike immediately the CO₂ cap and so blow up the rescue bladders. This could happen in many cases:
            - a diver in depth feeling ill at ease (cold, impression that he has overestimated his performances...);
            - but this could allow a not so good apnea diver to dive towards another lifeless apneist, who is at such a depth that reach and rescue him would be very difficult. Parents could try something to rescue one of their child who've just sunk. Many people are able to paddle or to immerse themselves, but not to reach a depth of 5 or 6 meters. What to do when one of your nearest and dearest is 15 or 20 meters deep, and you have to act very quickly ? It's much faster to pull on this harness and rush to the place of the accident, where someone has just sunk, than to bring a boat straight above to try to pick him up with a rope. In case of syncope, minutes are very important. The brain can not stand up to a lack of oxygen more than 5 minutes. It's too short to drop anchor and start a motor. With this system, you've just to dive towards the lifeless diver, to grab him and to pull on the handle: the lifejacket will bring you together to the surface.

   There's not only people having a fainting fit who could need some help: pull on such a harness and swim towards someone in trouble let you be sure you'll have in case of need a buoy, you don't have to tow.

   In fact, the hazard does not concern only divers. Every year, many people drown because they've got an hydrocution or they're tired out when there's a current. Swimmers would not like to go away with an unaesthetic Mae West on their back along with a CO₂ bottle rattling on their abdomen. For adjusting the Guardian Angel, we'd be very careful of the design, the "James Bond" aspect: nice bronze buckle, knife fastening, hydrodynamic design, funny colors. And, why not, helpful gadgets: whistle, small flashing light...

   Harnesses usually used on boats are uneasthetic and aren't easily adjustable. It's not reasonable to board on a yacht or a sailboat people who don't know how to swim. On every boat, you must find lifejackets. But very often, unless when there's heavy weather, people don't wear those cumbersome devices. A harness, yes but a lifejacket, hmm. People have got those jackets aboard the most often in order not to be breaking the law in case of a police check, or because they think it would be useful if the boat sinks. How many good swimmers have died drowning falling overboard, by day or by night?
   Nobody seems to have imagined that the design of those devices could be a factor to increase safety. Indeed, there's a continuity between the rescue system for a syncopated diver and the ordinary harness of a crew member on a boat. If a manufacturer takes an interest in this problem, many parts could be common to the two devices. As a consequence, there would be a market expansion and economy, when producing.
   When you're aboard a yacht, the safety rules should make you wear a harness and hook yourself on to the handrail. In those cases, an instant of carelessness may be fatal. What's the good of the harness of a crew member who is not hooked at this time, and that the boom will throw overboard? When such a blow threw Tabarly into the sea, he wasn't wearing any harness.
   After the accident, several scenarios are possible:
            - the people who have fallen into the sea can trigger the inflation of the bladders by pulling on the handle;
            - but this inflation could be made automatic, e.g. by the least high pressure on a manometric capsule hidden in the belt's buckle;
            - as this lifejacket is handy and aesthetic, this could lead people into wearing it systematically. Someone wearing a harness provided with inflatable bladders wouldn't hesitate to dive to help a friend fallen overboard, knowing he'll be able to rescue him and he won't be one more worry for the skipper;
            - the jacket could have two positions: 'yachting-safety' and 'diving-safety'. When on the yachting-safety, no bathing is allowed; when on the diving-safety, no diving more than 120 seconds.

Another remark of Benjamin Rottier:

   Every aircraft that flies over the sea has to be provided with lifejackets for pilots, crew members and passengers.

And Benjamin, who has his pilot licence, adds:

   Let's imagine the situation: a private aircraft, with 4 persons on board upon the sea, with an engine failure. Everyone (but the pilot!) gets in a panic, tries to pull up his big orange jacket, contorting himself in the narrow cabin. The pilot lets go of the controls to put on his lifejacket. When the aircraft crashes, it must be evacuated. It won't be easy, loaded down with those big jackets.

   The situation can be much worse. Some runways face the sea. An engine failure when the aircraft is taking off will put it in a crash situation much more quickly. Moreover, a sea landing is not so easy. If there's the least swell, it's sure that it will overturn. For such a use, the guardian angel, in its aeronautic version, would have inflatable bladders hidden on the front side of the braces and a small bottle of CO₂ located on the chest. It could be triggered in two ways:
            - manually;
            - or automatically, when a little manometric capsule, located in the front of the abdomen, is on small high pressure.

   This second system, automatic, may save lives if the passengers are ejected when the aircraft crashes. In both cases, this uncumbersome device could be worn during the flight by the passengers and the pilots.
   You'll note that such devices could possibly replace the systems used on airliners. The actual lifejackets can be used only if the aircraft has made a perfect sea landing, gear up, on a smooth sea. You might imagine that the passengers will pull their jackets up, as the aircraft loses altitude and then will reach the exits in order and with discipline, guided by hostesses. But in reality, other situations can happen: the cabin may be broken, the passengers may be thrown away into the sea, unconcious or unable to blow up their jackets. In thoses cases, an automatic triggering of the inflation, by a barometric capsule, could be very useful.