Re: [RMURRAY] Vigil Status report

[mdrejhon 8]

Alternative perspective, for future AAD models (Cypres 3, Vigil 2, etc)

This may encourage future AAD's to use an accurate 3-axis inertial accelerometer (similiar to those used in missles and super-expensive automobile GPS systems for tunnel use).

The accelerometer would determine whether there was a sudden acceleration proportional to the pressure reading. So if the acceleration calculated by air pressure reading was vastly different (i.e. pressurization simulating a sudden acceleration to 200 mph freefall) from the acceleration calculated by the 3-axis inertial accelerometer (i.e. there has been no acceleration measured, the plane is still moving at the same speed), it will automatically prevent the AAD from firing.

If accurate enough, an inertial accelerometer would be useful for wingsuit jumpers, and theoretically, algorithms in a 3-axis inertial accelerometer, could possibly be developed to automatically detect acceleration that looks like a swoop instead, and avoid firing. Thus, no need for a "Speed Cypres" model (in theory, at least). True, this may not be possible though, but at the very least, there should already be enough accuracy in a 3-axis accelerometer to prevent misfires from aircraft pressurization. (Since the readings from an accelerometer would now be so vastly different from readings from air pressure)

Of course, the accelerometer would likely need military-level accuracy similiar to those used in weapon missles. They are typically bulky (gyroscopes, etc), but some accelerometers are so tiny they fit inside the control unit of an AAD. I am sure all of them are already researching this, but I do know that tiny accelerometers are not yet as accurate as the gyroscopes used in missles, so I assume there's a good reason they are not being used right now.

I am pretty certain the military has occasional issues about AAD misfires in erroneous aircraft pressurizations during military exercises, but this is never made public. This may be why Cypres2 does not seem to fire in most aircraft pressurization situations, since Cypres is the most popular AAD used in the military, too. However, I bet the Cypres2 can still fire in an aircraft pressurization if the pressurization was exactly at the right speed (to simulate a 120mph freefall going through 1000feet, instead of 673mph or 361 feet below the ground).

Since C130's are probably going to be around for a long time, I believe technology will solve AAD misfires in aircraft within 15 years -- take my word for it as a programmer/engineer. (Even if I am a newbie jumper, I have a good understanding of technology since I work with both software and hardware design)

[slotperfect 7]

This was too good on its own - I moved it from the Vigil thread.

Arrive Safely

John

[nbblood 0]

This all sounds good, but here's the problem:

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similiar to those used in missles and super-expensive automobile GPS systems for tunnel use

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Of course, the accelerometer would likely need military-level accuracy similiar to those used in weapon missles.

People are not going to pay $15,000 for an AAD to prevent an misfire in a plane due to pressurization. There simply is not that many occasions when this situation presents itself and it's not going to be worth the "super-expensive" "military accuracy". Personally, I'd be surprised if the AAD companies were even considering this option due to the cost vs. benefit.

Swoops can be accounted for by a simple on/off button. Why spend all this money on a device for that? How often does the situation as experienced in Thailand really happen? Not very and only under special circumstances.

I just don't see AAD companies making major changes due to this. It's just not worth the cost.

Blues,
Nathan

If you wait 'til the last minute, it'll only take a minute.

[bob.dino 0]

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Swoops can be accounted for by a simple on/off button. Why spend all this money on a device for that? How often does the situation as experienced in Thailand really happen? Not very and only under special circumstances.

I just don't see AAD companies making major changes due to this. It's just not worth the cost.

Agreed, though it's worth noting that an on-off button may not be all that simple to implement.

[PhreeZone 15]

AirTec has probally ran into this a lot more due to their experience with different military units in their development with the Military CYPRES. Overall, while this might seem to be a rare occurance it has happened and the conditions continue to exist for this to occur at the next World team event or at any boogie with a pressurizable aircraft. Its interesting to see each companies responce to this.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[FrogNog 1]

If you use a sufficiently accurate accelerometer, it can determine your 3-d location over the Earth's surface and, if the ground height at that point is known, your altitude above ground level. Accelerometers of this precision have been in use for quite a few years in commercial airline flight, if I understand correctly.

And an accelerometer would need nowhere near that amount of precision or intelligence to be able to tell when you had gone from 13,000 feet AGL to 750 feet AGL and what your descent speed was at that point. It would be reasonable to tell your accelerometer device what altitude you were exiting at _when you exited_ and it could figure out the rest (assuming it knew which way was down ).

Switching gears, and talking about misfires and anti-fires, what you're basically trying to cover is how to tell the AAD when you're under canopy and not about to die.

The classic AAD-compatible way to do this has been to 1. not fly wingsuits below AAD save altitude and 2. not fly canopies at descent speeds that mimic freefall.

An AAD programmed to fire regardless of descent rate could catch wingsuiters who lose altitude awareness (but still manage to fly at a low descent speed), and would require the wingsuit jumper to disarm the AAD under canopy before passing activation/save altitude.

An AAD that can be disarmed once a good canopy is in place should work for people who fly their canopies all crazy and don't want the AAD to get scared. (On a swoop that looks like freefall, there's really nothing helpful the AAD can do other than yell "yeehaw!" through a little speaker.)

Are there already any AADs that the jumper can turn off under canopy?

And are there already any AADs that will fire at the lowest current wingsuit descent speed? (Certainly, there are existing ones that could be reprogrammed to do so.)

Are there any AADs that combine these two things?

Ironically, if I remember correctly there are old, untrustworthy AADs that incorporated both these features, and the advent of new, trustworthy, electronic AADs shifted the feature set (i.e. removed descent-rate-independent firing and, in some cases, in-flight-user-disarmability) as a coincidence of increased precision, reliability, and ease-of-use under most conditions. Perhaps we need only ask that the feature set be shifted back the way it was.

-=-=-=-=-
Pull.

[mdrejhon 8]

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This was too good on its own - I moved it from the Vigil thread.

Gee thanks, BEER! First thread upgrade by a greenie!

I don't think I warranted that much of an upgrade, but thanks.

[mdrejhon 8]

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People are not going to pay $15,000 for an AAD to prevent an misfire in a plane due to pressurization. There simply is not that many occasions when this situation presents itself and it's not going to be worth the "super-expensive" "military accuracy".

Hi,

I have a $19.95 digital clock/countdown/alarm/thermometer from Radio Shack that automatically switches modes turns into a clock or countdown timer, when turned turned 90 degrees or upsidedown. It likely uses a two-axis accelerometer to pull this off (most likely, two cheap one-axis micro accelerometers). Not nearly accurate enough as it is very slow responding and not 3-axis (for full 3D capability).

TomTom's ~$1199.95 GPS unit now has an accelerometer. This is the cheapest unit that has an accelerometer ("Assisted Satellite Navigation (ASN)") for the GPS to continue to function inside tunnels with no satellite reception. I think it's still only 2-axis, not 3-axis though, since it only needs to go horizontally, not vertically.

Some accelerometers are really cheap (under one dollar each for the accelerometer chip, like the one used in my cheap Radio Shack gadget thingy), while others are super-expensive and massively more accurate. There's a massive price spread, and a corresponding massive accuracy difference. And accelerometers are everywhere now (i.e. automobile airbags, some specialty wristwatches and gadgets, certain kinds of presentation-room controllers, etc.)

The verdict: Prices appear to be falling while accelerometer accuracy is going up. By 10 years, I would imagine cost is not going to be an issue for a super-accurate one. There was a long lead time between Cypres and Cypres 2, so there appears to be plenty of time before Cypres 3.

I am no expert at what Cypres does, but I would bet the smart AAD manufacturers are already keeping an eye on this, since it is a very useful datapoint for AAD's.

Accelerometers are easily obtainable these days (lots of google ads when you search "cheap accelerometer chip" on Google -- clicky) and are a popular electronics geek project or University education project as well.

[mdrejhon 8]

FrogNog,

As I am not a swooping nor a wingsuit expert, you have many good points, and it is possible that accelerometer plus air pressure is not enough data to distinguish swooping vs winsuiting vs emergency situations vs canopy opening shock, etc. But, we owe it to the AAD manufacturers to eventually answer these questions through their research, no?

True, a 3-axis accelerometer can only determine relative changes in the velocity vector (direction, speed) so a constant 100mph looks identical to a constant 170mph to an accelerometer. BUT, if you cross-reference the accelerometer readings (i.e. no changes in velocity, so you haven't accelerated) with a sudden change in the rate of pressure change (i.e. aircraft pressurization suggests you fallrate suddenly accelerated), this is a very clear an unmistakable inconsistency in acceleration comparisions.

World Team 2006 has highlighted the problem of AAD problems in pressurized jump aircraft (not one, but TWO separate incidents on separate days causing AAD problems), and how Cypres 2 seemed to have behaved properly in these situations. So an accelerometer may not even be necessary if it's very rare for aircraft pressure issues mimic the right activation thresholds (78mph between ~120 and 1000 feet).

I'm pretty sure that at least one of the AAD manufacturers have thought of using accelerometers yet, but have not done so mainly because of cost/accuracy/size/power concerns. What if all these limiting factors were solved, and available in a cheap 1-dollar 3-axis accelerometer chip that is accurate enough? The question is, will it now be massively useful and not counterproductive in an AAD? And another question, what specific things can such a 3-axis accelerometer do to benefit AAD's? Will an accurate accelerometer cause more or fewer misfires and no-fires? Would the accelerometer still be useful even in situations such as tumbling and centrifugal G-forces that can confuse accelerometer readings? This should be researched, or is currently being researched.

Simpler accelerometers are already being used in automobile airbags. They're already well trusted in those emergencies. So there is at least some precedent of accelerometers being used in emergency situations. Understandably, skydiving is a lot more complicated, and a lot of data logging would need to be done...

I agree there are limits on the usefulness of accelerometer readings, but I think it is a good idea to have the AAD companies research this if it really genuinely makes an AAD better or not. It's their job to research, after all. After all, tomorrow's cheap accelerometers may become as accurate as today's expensive stuff eventually, knowing how technology drops in price.

[RMURRAY 1]

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Swoops can be accounted for by a simple on/off button. Why spend all this money on a device for that? How often does the situation as experienced in Thailand really happen? Not very and only under special circumstances.

I just don't see AAD companies making major changes due to this. It's just not worth the cost.

Agreed, though it's worth noting that an on-off button may not be all that simple to implement.

I guess you don't need an button to turn off, it can be automatic.

on the subject of pressurized a/c how about keep the door cracked open. is that simple procedure off limits?

rm

[spanky39154 0]

Not saying an on / off for swoopin isn't a good idea to an extent but what your forgeting is the human factor to remember and turn the thing back on!!!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Never under estimate the power of stupid people in large Groups!!

[tso-d_chris 0]

Would this be similar to the technology used in laptops to lock down the HDD and shut off the screen in the event it senses it is falling?

For Great Deals on Gear

[LouDiamond 1]

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This is the cheapest unit that has an accelerometer ("Assisted Satellite Navigation (ASN)") for the GPS to continue to function inside tunnels with no satellite reception.

I looked at the Tom Tom site and I think you may be confusing this for something that it is not. What allows the Tom Tom to do what you describe is possible through the products use of a cell phone and is known as AGPS.There is no way for a GPS to accurately function if it is not receiving signal/information from the satellites be it from a repeater or other assisted means.


A stand-alone GPS receiver (a) must search for satellite signals and decode the satellite navigation messages before computing its position - tasks which require strong signals and additional processing time. A cellular telephone network can assist a GPS receiver (b) by providing an initial approximate position of the receiver and the decoded satellite ephemeris and clock information. The receiver can therefore utilize weaker signals and also more quickly determine its position. (see chart 1)

Assisted-GPS requires a worldwide tracking network for obtaining the navigation messages of all satellites and data processing hubs along with a server which feeds data to a Serving Mobile Location Center (SMLC) or Mobile Position Center (MPC) operated by a network service provider. Data is sent to individual cell phones using Hypertext Transfer Protocol (HTTP) and the Short Messaging Service (SMS). (see chart 2)



As for military applications in AAD use goes. We are still using the tried and true FF2 which is a mechanical barometric system. The Cypress2 is in use and it did have some early issues which have been compensated for and hence the Military version being created. While there are some similarities, there is a difference in requirements for Military and sport skydiving. The easy answer to this issue is low tech but requires more user knowledge and hands on equipment. The Mechanical barometric system used in the FF2 would work for the issues described with canopy swooping and wingsuiting.This system works set up on the main but can be set up on the reserve like current sport systems.

However, if the A/C does decend below the activation altitude while the unit is armed, it will function. Likewise, the same can hold true if there is a rapid change in barometric pressure that would simulate the unit arriving at the preset barometric firing altitude. This system activates every time even if the main is deployed when it reaches the preset altitude. Since it pulls and doesn't cut , it is no big deal but the unit must be cocked/reset after each jump for it to function again.It also requires knowing what the current barometric pressure is on the ground and setting the unit to the desired activation altitude based on barometric pressure at different altitudes using what we commonly call a "whiz wheel". Of course if the weather changes throughout the day, the unit must be adjusted to compensate for the barometric change. Like I said, it isn't the easiest method but it is very effective when used correctly.

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[RMURRAY 1]

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Not saying an on / off for swoopin isn't a good idea to an extent but what your forgeting is the human factor to remember and turn the thing back on!!!

maybe I should not have used the term "off" --- I would like to see them (have an option to) unarm below 750 ft. Anything situation below 750 ft, you are on your own - very easy to understand.

rm

[phoenixlpr 0]

Oh God! NOOOOOOOOOOOO

KISS

[labrys 0]

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I looked at the Tom Tom site and I think you may be confusing this for something that it is not. What allows the Tom Tom to do what you describe is possible through the products use of a cell phone and is known as AGPS.

But they specifically claim to use ASN, not AGPS. ASN does use accelerometers to calculate location while the satellite signal is blocked.

Owned by Remi #?

[mdrejhon 8]

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I looked at the Tom Tom site and I think you may be confusing this for something that it is not.

You bring up good and excellent points, but you are mistaken at one thing: TomTom DOES definitely use accelerometers.

The news reporting at www.gpspassion.com brought this up a couple years ago, and I distinctly remember accelerometers. (It may take some hunting in the Archives to find this though). This was reported on a couple of mainstream news websites back around 2004 or thereabouts, and it did not use any additional radio references, so it worked in any tunnel in any world, for a certain amount of time until the accelerometer 'drifted' out of precision. You are correct that this is a finite amount of time, but sufficently enough precision to keep pretty good precision through a whole typical automobile tunnel. Accelerometers make a massive difference in urban canyons where GPS reception is intermittent and the accelerometer in the TomTom unit allows it to smooth the gaps in GPS reception much better. TomTom does use accelerometers for tunnel location tracking and for urban canyons. They just give it a marketing name called "Assisted Satellite Navigation" -- fancy marketing speak for accelerometer-assisted GPS. It is different from AGPS, which is a different technology.

Also, Google Search says TomTom uses accelerometers - CLICKY.

If you read online and magazine reviews about TomTom Go, there are good reviews about TomTom being one of the better third party add-on GPS navigation systems for a car, because of its excellent GPS position hold in urban canyons and tunnels that was clearly superior to competing automobile GPS units that did not have this accelerometer assistance. They did note that inside longer tunnels locks were automatically lost -- after having successfully held a reasonably accurate location fix for a remarkably much longer period than non-accelerometer-assisted GPS units. I saw a magazine review sometime in 2004, that also covered this as well.

I know that position fixes updated by accelerometers "decay" in accuracy when not corrected with a source of reference (updated satellite position fix) since errors are cumulative, and position fix gets worse and worse. So TomTom knows this, they give a finite amount of time after the actual real-satellite GPS fix, in trusting the accelerometer before automatically losing the accelerometer-assisted GPS fix (the threshold where it can no longer trust the accumulated error updating the last satellite GPS position only from accelerometer data). Typically, this buys you a certain amount of time after the last GPS fix, say, 60 seconds (maybe less, maybe more) of reasonably accurate position fixes (good enough for a map graphics subsystem) while driving through a tunnel or down a road through an urban canyon, for example. Essentially used as a GPS reception "gap-filler". I am just merely saying accelerometers have successfully found an application in civilian GPS units already, today.

Good information though about barometric stuff. Just wanted to be clear that I am familiar GPS vs AGPS vs accelerometer-assisted GPS. and that I am definitely not mistaken about confusing AGPS versus accelerometer-assisted GPS.

You likely do know more than I do about whether accelerometers are good or bad for AAD's. You may be right that a good barometric algorithm is good enough, but this begs a question: Are accelerometers useful in any possible way, in an AAD, without sacrificing safety? I think it's a valid question whether it's of any benefit in the future, don't you think?

[mdrejhon 8]

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Would this be similar to the technology used in laptops to lock down the HDD and shut off the screen in the event it senses it is falling?

Yep.

[kelpdiver 2]

Mark, this definitely looks like a KISS violation with very little need. If anything, points to yet another specific model (like the C2 swoop model) for those who have concerns with pressurized aircraft.

Or perhaps simpler solution lies in the aircraft procedures?

[LouDiamond 1]

Point of clarification. I don't doubt the Tom Tom uses an accelerometer but the way it is marketed can lead the average person to think their GPS is still receiving a signal.The ASN they refer to uses "dead reckoning" when GPS signal is lost by the receiver and basically guesses where the GPS receiver is going but it in no way receives a true GPS signal. Hence my using italcs on the word accurately in my post. All modern data loggers(neptune, etc) and AADs already use an algorithm that allows the unit to "think ahead" much like the Tom Tom uses the accelerometer, only a great deal faster and more often.

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[mdrejhon 8]

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Mark, this definitely looks like a KISS violation with very little need.

That's a valid question -- but that's for the AAD manufacturers to decide, no?

[billvon 2,400]

>People are not going to pay $15,000 for an AAD . . .

I have a two axis accelerometer right here on my desk. Would work well for an AAD, and it costs around $10. For three axis usage, get two.

[f94sbu 0]

A tumbling (or rotating) body will show very funky readings from the accelerometer. So in order for this to work, the device needs to be able to tell its orientation accurately. However this wont be doable using 2 3-axis devices since the spacing will be too small to notice any difference between the readings. A gravity sensor wont work either since it will be useless during the event of a sudden free fall (cutaway for example). The only thing left I can think of is a gyroscope.

I guess this problem isn't as simple as it may seem from the start...
rgds,
Stefan

[labrys 0]

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A tumbling (or rotating) body will show very funky readings from the accelerometer.

Rotation will read as rotation...nothing funky about that.

Owned by Remi #?

[mdrejhon 8]

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The only thing left I can think of is a gyroscope.

Good accelerometers are gyroscopes. They've become increasingly tiny. A good 3-axis accelerometer would compensate for tumbling.

Just give technology time and perhaps someday a simple chip with simple data output for a simple computer program, can much more easily cross-reference this data with the pressure data, for improved AAD use. Right now, KISS is probably violated as is suggested (although I'd leave it to the AAD makers to decide that), but it may not be in the future, theoretically.