Cypres curiosity...

What I want to know is: What safeguards have been taken to keep a Cypres from firing while under a good main?

What I mean is, let's say you were at 850 feet and did some radical canopy work that got you falling faster than 78 MPH at 750 feet. Would the Cypres fire?

Is there some unwritten guideline out there that states: If you are smart, don't do anything radical on your canopy at that altitude? (Other than the one that says you should be well into the landing approach pattern at this point and not goofing around with the canopy

I am not saying that I am worried that this might happen to me. I am just curious.

Safe ones!

Please read a CYPRES owners' manual and/or go to SSKs' web-site. All of your questions have been dealt with, other than the one which you answered

Didn't Charlie Mullins try unsuccessfully to make one fire under canopy a year or two ago? Something like that....

As far as I know, the only canopy that could generate enough vertilce speed (78 mph) is the EXTreme VX 46. As far as I know, the only person currently jumping that canopy is Luigi Cani. I'm not sure if he would want to generate that much verticle speed at or below 750' agl. Below 130' agl, the CYPRES ceases operation and won't activate.

Hmm, I'm not sure that only Luigi could do it.

My Pro-Dytter's third warning signal is set at 1500ft. The third warning signal is activated only if speed exceeds 27m/s (=60mph).

Last weekend I did a 2-way head-down and we were first out on a Pilatus load with students and tandems. My friend had dumped higher than me. After deployment I had the air to myself. I was jumping a Sabre 150 loaded at 1.25. I was playing heavily with the canopy when suddenly I heard my Pro-Dytter at 1200ft.

Was I stupid to do such heavy manoeuvering at 1200ft? I was altitude-aware all the time. I wasn't pushing my limits, nor those of the canopy. I feel I could have gone even faster with this canopy. Unlike most other people on the same load, I had even noticed that the wind had changed since we got on the plane (half the people on the load landed downwind). I had time to set-up my landing pattern while playing with the canopy (I landed next to the manifest, as always). I stopped the radical canopy work at around 1000ft (didn't even hook it in). I have done almost 300 jumps with this canopy in the last year and my last 40 jumps were on a Stiletto 120.

Anyway this is not the point.

The point is that if even I can reach more than 60mph with a Sabre loaded at 1.25, I wouldn't be surprised to hear that a more aggressive canopy pilot with a small elliptical loaded at 1.6 can get pretty close to or even exceed the 78mph threshold.

You said in another reply in this thread that the cypres manual and the SSK website discuss these issues. All I can find is a statement saying:

'Whatever you can think of under canopy like stalls, spiral turns, down planes, hookturns with the smallest canopies as well as any CRW, CYPRES will analyze these movements without problems. It won't interfere with any normal activities while skydiving.'

Is there anything more in the manual or on the website? For me, it remains an open question how cypres can differentiate between a low cutaway and low radical canopy work.

I'm sure that Luigi would want to generate that speed at and below 750 feet, and am pretty sure that is the point of the 3.5 wingloaded 46 he is jumping.

Hi,

I sent a copy of my posting to SSK yesterday. I got an interesting reply today.

According to SSK I didn't really go 60mph when I heard my Pro-Dytter go off (what a relief!). What happened is that there was a sudden fluctuation in air pressure that fooled the Pro-Dytter into thinking I was going 60mph. Still according to SSK, it's not uncommon to hear your Pro-Dytter go off while under canopy. A Cypres cannot be fooled as easily as a Pro-Dytter. A Cypres (being a $1000 device) was designed to deal with such sudden fluctuations in air pressure.

I asked them whether I could post their reply. As soon as they've confirmed, I'll post it.

Just curious: what estimated vertical speeds did you reach?

Bwaa, you sissy!

Just kidding ))

Based on SSK's comments about fluctuations in air pressure, you don't need a highly loaded EXTreme to get your pro-dytter to go off. You would have to be in that accidental fluctuation that fools the pro-dytter.

One would reach 78mph after 3.6 seconds (velocity = acceleration * time). Actually it would take slightly longer, due to air resistance. Let's say 4-5 seconds, just to be on the conservative side.

By then, one would have covered between 260 and 400 feet (distance = acceleration * time * time / 2). Actually it would be slightly less, due to air resistance. Let's say 250-350 feet.

Cypres stops working at 130 feet.

So, the lowest cutaway were a Cypres could save a skydiver would be something like 400-450 feet.

Not that I'd be willing to thrust my life to these calculations ... or to the

I'm curious. Why would he want to generate that much 'verticle speed' at that altitude? It is verticle speed that we are talking about. I know why he wants to do it up high and I can understand why he would want the horizontal component at the low altitude. I know he has to increase his verticle speed somewhat at the lower altitude to convert to the horizontal component for increased lift, but from what I could see, he uses a carving turn and that won't generate that much verticle speed.

That is why I didn't call you a liar or idiot for making your claim and instead said 'OK'. You showed a good deal of intelligence by contacting SSK and getting solid information from a good source.

Just rough numbers, but about 55 to 60 mph. I think it it possible to go faster and at some points I may have, but this would be the average.

Hehehehe! I do get scared pretty easily.

Yup, that happens. I think some dytters may be more susceptable than others as well.

That all looks about right to me....especially the last comment.