Reply from a recent Vigil tech support query.

[riggerpaul 1]

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Just because there is only one that lets us do that now doesn't mean it will always be that way.

The Argus will also display the barometric pressure.

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A quick check says there are digital barometers available in a wide range of prices, from about $30 up.

I don't in any way think of this as a replacement for periodic maintenance and evaluation by folks with more specialized tools than I have. So I don't presume I'd need a lab-quality instrument. Personally, there is a barometer in my home weather station already. So I'd just use it.

With no idea of the accuracy or precision of the barometer in your home weather station, comparing it to an AAD is of limited value, IMO. In fact, I'd have more faith in the readings from the AAD, which presumably meets some specified level of precision and accuracy and has been calibrated, than in the readings from the consumer device in a home weather station.

First, thanks, I hadn't realized that the Argus would display the pressure. But you are correct. Thanks.

Regarding the utility of a barometer, well, my home weather station barometer agrees with the ATIS I receive from the nearby airport.

We are not talking about factory-level maintenance here. We are talking about a quick sanity check of the device.

I use a fish scale to check pull forces. It is not as accurate as I'd like, but it works well enough to be better than nothing.

Anyway, when next I can, I'll bring my Argus home and report on the correlation between the two barometers.

[Abedy 0]

There is another aspect to keep in mind.
Most measurement devices do not measure the intended physical value itself but something that is in a relation to it. (Example: A classic thermometer provides the length of a column of a liquid based on the fact that the expansion of it is in a linear correlation to the temperature.) Same goes with air pressure. Means you must also take care the relation between the physical value actually measured and the value you want to know remains unchanged after calibration of the scale. (That's another piece of cake if it is non-linear, for example...) In German, this is called "Kennlinie" = characteristic curve.
If you wish to find out whether your AAD is really, really exact, you'd also have to check whether the abovementioned Kennlinie hasn't changed. That takes a little more than a calibrated barometer for ONE point of the characteristic curve
(Yeah, physics was one of my subjects at university long, long ago...)

The sky is not the limit. The ground is.

The Society of Skydiving Ducks

[koppel 3]

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In German, this is called "Kennlinie" = characteristic curve.
If you wish to find out whether your AAD is really, really exact, you'd also have to check whether the abovementioned Kennlinie hasn't changed. That takes a little more than a calibrated barometer for ONE point of the characteristic curve

So can you please comment on your thoughts about the Vigil requirement to compare the unit to QNH or a known air pressure/barometer annually?

cheers

I like my canopy...


...it lets me down.

[Nelyubin 0]

Using Vigil, even without the knowledge of university, you will at any time have the opportunity to judge the condition device. Try to overcome hatred and class to read one paragraph of instructions to the Vigil. :)
Page 16, paragraph
3.5.5. «INFO» Menu (Information)
http://www.vigil.aero/files/images/ENGELS___DP_JUN_2010.pdf

[Abedy 0]

Hatred? ROTFL!!!
You're pathetic.

The sky is not the limit. The ground is.

The Society of Skydiving Ducks

[Abedy 0]

I just wanted to point out that even if you check for ONE point of the characteristic curve you do not really know if other parts of it are still "in shape". The idea of checking it OK so far but again, I think that it doesn't really uplift safety to a much higher level.



P.S.: I do not own a VIGIL and I personally do not harbour any negative thoughts about it. If someone jumps with it, it's OK.
I just do not like it if someone's (NOT YOURS!) aim is only degrading the CYPRES. (Especially if coming from a country where some FJC'ers are still equipped with "hightech" such as KAP3 as an AAD...)

The sky is not the limit. The ground is.

The Society of Skydiving Ducks

[Nelyubin 0]

Thus, on this subject is nothing you can say?
You are once again engaged in advertising.

It is bad that you could not understand one paragraph (3.5.5.) statement.
Go to the topic of Cypres. Just try and not engage in advertising there.
P.S. How many times you press the button to go to the menu info Vigil ?
P.P.S. You reason that you do not know. This is silly.

[Skybear 0]

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You are once again engaged in advertising.

You not?

3.5.3 only says, that the Vigil verifies that the battery pck, the cutter and the electronic circuits (main functions) are in proper working conditions.

There is no statement about the determination of sensor accuracy. But this is, what was asked by Kenny.

[Nelyubin 0]

Any DZ you have the opportunity to hear the nearest airport manager. Manager generally reports the temperature, pressure, humidity, and much more. After reading the information menu you have the ability to compare data. No need to have their own precision instrument for comparison.
This is advertising?
Specifically for you attached a picture of paragraph 3.5.5

I'm just trying to explain to a person unknown to him the possibility of the elementary unit.

[PiLFy 0]

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Hi,

I am currently out of the office until June 27th and will have limited internet access. I will reply to all voice mails and email periodically and upon my return in the order it was received.

Thank you!
___________________________________________________
On Jun 17, 2011, at 7:14 PM, ***********************wrote:

Hello Again Vladi,
A further question has come up in our debate. How exactly does the Vigil2 self-diagnostic determine the pressure sensor is accurately reading atmospheric pressure? How do we, as end users, know that the unit is properly calibrated w/respect to barometric pressure?
Thank You, & have a nice weekend.
Kenny

__________________________________________________

Kenny,

sorry for the late reply. I'm at the Vector Fest in Europe right now so travel, lack of internet and time difference can cause some delay in answering emails the next few days...

To answer your question, pretty simple...
the Vigil will use the current pressure from the location where you start it up as a reference, so actual pressure used in QNH settings (in military or aviation applications) is irrelevant. It's a different story for military units where QNH (actual pressure measured to sea level) is extremely important. Those devices will get a recommended two yearly calibration.
With a VigilII, it's pretty much like turning your analogue altimeter back to zero every morning before jumping.
Upon start up and self check, if the parameters/calibration are out of range beyond an acceptable point, then the unit will respond by giving a "control error" and then shutdown.

Hope this helps!

Regards,

Vladi

OK, is it me? Or, was my question not answered? BTW, a couple of you are squabbling. Please stop fighting. I didn't post this topic to provide another thread to be locked. I did it to find out some answers. OK, please & Thank You?

[GobbleGobble 0]

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Hi,

I am currently out of the office until June 27th and will have limited internet access. I will reply to all voice mails and email periodically and upon my return in the order it was received.

Thank you!
___________________________________________________
On Jun 17, 2011, at 7:14 PM, ***********************wrote:

Hello Again Vladi,
A further question has come up in our debate. How exactly does the Vigil2 self-diagnostic determine the pressure sensor is accurately reading atmospheric pressure? How do we, as end users, know that the unit is properly calibrated w/respect to barometric pressure?
Thank You, & have a nice weekend.
Kenny

__________________________________________________

Kenny,

sorry for the late reply. I'm at the Vector Fest in Europe right now so travel, lack of internet and time difference can cause some delay in answering emails the next few days...

To answer your question, pretty simple...
the Vigil will use the current pressure from the location where you start it up as a reference, so actual pressure used in QNH settings (in military or aviation applications) is irrelevant. It's a different story for military units where QNH (actual pressure measured to sea level) is extremely important. Those devices will get a recommended two yearly calibration.
With a VigilII, it's pretty much like turning your analogue altimeter back to zero every morning before jumping.
Upon start up and self check, if the parameters/calibration are out of range beyond an acceptable point, then the unit will respond by giving a "control error" and then shutdown.

Hope this helps!

Regards,

Vladi

OK, is it me? Or, was my question not answered? BTW, a couple of you are squabbling. Please stop fighting. I didn't post this topic to provide another thread to be locked. I did it to find out some answers. OK, please & Thank You?

He might not be able to get into it too specifically if they consider it to be proprietary information.

[davelepka 4]

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OK, is it me? Or, was my question not answered?

It was answered, the problem is that some of the info is this thread is misleading, so you were expecting something else.

The idea is that the unit 're-zeros' itself at start up to 'set' the ground elevation. Just like you do with your wrist mount alti, and just like a Cypres, Argus, ProTrack or any other audible does.

What the Vigil offers is a readout of what pressure it reads, but that's not always going to be related to what the weather service says. If the Vigil thinks the pressure on the ground is 29.75, and the weather service says it's 30.10, it's irrelevant because the Vigil will fire at what it thinks is ground level plus 750 (or 790, or whatever).

This thread has lead you to believe that you can use that to check the accuracy of the sensor, but that's not entirely true. If you kept a log of what the Vigil displays and what the weather service reports, you would have an on-going idea of the offest between Vigil-pressure and 'real' pressure, and in that sense you could track the offset and check that it's consistant. On a one-time basis, however, looking at Vigil-pressure and 'real' pressure will tell you nothing about the accuracy of the Vigil.

It's a feature that's being pushed as one thing, when it's really no better or worse than the Cypres (in that respect). Both units conduct a self check on start-up, and neither will 'power up' if anything fails the check. If the unit reads everything as OK, it will 'power up' and indicate for normal operation. Beyond that, the Vigil offers you the ability to check the 'Vigil pressure' but if that was reached by a faulty sensor that could pass the self check (like the Cypres), you will jump with a faulty sensor. The reporting of the arbitrary pressure the Vigil measures is of questionable use in the real world.

There are other, much more significant issues between the two that should guide a decision to purchase in either direction.

[riggerpaul 1]

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OK, is it me? Or, was my question not answered?

It was answered, the problem is that some of the info is this thread is misleading, so you were expecting something else.

The idea is that the unit 're-zeros' itself at start up to 'set' the ground elevation. Just like you do with your wrist mount alti, and just like a Cypres, Argus, ProTrack or any other audible does.

What the Vigil offers is a readout of what pressure it reads, but that's not always going to be related to what the weather service says. If the Vigil thinks the pressure on the ground is 29.75, and the weather service says it's 30.10, it's irrelevant because the Vigil will fire at what it thinks is ground level plus 750 (or 790, or whatever).

This thread has lead you to believe that you can use that to check the accuracy of the sensor, but that's not entirely true. If you kept a log of what the Vigil displays and what the weather service reports, you would have an on-going idea of the offest between Vigil-pressure and 'real' pressure, and in that sense you could track the offset and check that it's consistant. On a one-time basis, however, looking at Vigil-pressure and 'real' pressure will tell you nothing about the accuracy of the Vigil.

It's a feature that's being pushed as one thing, when it's really no better or worse than the Cypres (in that respect). Both units conduct a self check on start-up, and neither will 'power up' if anything fails the check. If the unit reads everything as OK, it will 'power up' and indicate for normal operation. Beyond that, the Vigil offers you the ability to check the 'Vigil pressure' but if that was reached by a faulty sensor that could pass the self check (like the Cypres), you will jump with a faulty sensor. The reporting of the arbitrary pressure the Vigil measures is of questionable use in the real world.

There are other, much more significant issues between the two that should guide a decision to purchase in either direction.

If the sensor does not read QFE (field elevation barometer) with the required accuracy, the device cannot fire at the correct AGL altitude.

The pressure lapse rate is not linear. A proper algorithm will understand that a very low pressure reading at startup means a high field elevation, and will take that into account when determining the firing altitude parameters.

If the ground-level reading is sufficiently wrong, the AAD will fire at the wrong time.

Do the current AADs use a proper curve for the lapse rate? Damned if I know. But if they really intend to fire at the altitudes AGL that they say, they must. Else they should publish that at different field elevations the devices will have different firing altitudes.

If you don't get a proper value at ground level, you are not going to get a proper firing altitude.

Maybe people at high elevations have NEVER gotten a proper firing altitude. I didn't write the software, so I don't know.

But without a reasonable pressure reading at ground level, all other bets are off.

If all dropzones were are seal level, it would be a different story. But they are not. And if the AAD is really going to fire at a particular AGL altitude, it MUST have an accurate idea of what the MSL altitude of the field is.

So, Dave, simply, is the barometric lapse rate linear or not? I do not believe it is. And if it is not, then an accurate field level barometric pressure is REQUIRED for the device to work as advertised.

[GobbleGobble 0]

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OK, is it me? Or, was my question not answered?

It was answered, the problem is that some of the info is this thread is misleading, so you were expecting something else.

The idea is that the unit 're-zeros' itself at start up to 'set' the ground elevation. Just like you do with your wrist mount alti, and just like a Cypres, Argus, ProTrack or any other audible does.

What the Vigil offers is a readout of what pressure it reads, but that's not always going to be related to what the weather service says. If the Vigil thinks the pressure on the ground is 29.75, and the weather service says it's 30.10, it's irrelevant because the Vigil will fire at what it thinks is ground level plus 750 (or 790, or whatever).

This thread has lead you to believe that you can use that to check the accuracy of the sensor, but that's not entirely true. If you kept a log of what the Vigil displays and what the weather service reports, you would have an on-going idea of the offest between Vigil-pressure and 'real' pressure, and in that sense you could track the offset and check that it's consistant. On a one-time basis, however, looking at Vigil-pressure and 'real' pressure will tell you nothing about the accuracy of the Vigil.

It's a feature that's being pushed as one thing, when it's really no better or worse than the Cypres (in that respect). Both units conduct a self check on start-up, and neither will 'power up' if anything fails the check. If the unit reads everything as OK, it will 'power up' and indicate for normal operation. Beyond that, the Vigil offers you the ability to check the 'Vigil pressure' but if that was reached by a faulty sensor that could pass the self check (like the Cypres), you will jump with a faulty sensor. The reporting of the arbitrary pressure the Vigil measures is of questionable use in the real world.

There are other, much more significant issues between the two that should guide a decision to purchase in either direction.

If the sensor does not read QFE (field elevation barometer) with the required accuracy, the device cannot fire at the correct AGL altitude.

The pressure lapse rate is not linear. A proper algorithm will understand that a very low pressure reading at startup means a high field elevation, and will take that into account when determining the firing altitude parameters.

If the ground-level reading is sufficiently wrong, the AAD will fire at the wrong time.

Do the current AADs use a proper curve for the lapse rate? Damned if I know. But if they really intend to fire at the altitudes AGL that they say, they must. Else they should publish that at different field elevations the devices will have different firing altitudes.

If you don't get a proper value at ground level, you are not going to get a proper firing altitude.

Maybe people at high elevations have NEVER gotten a proper firing altitude. I didn't write the software, so I don't know.

But without a reasonable pressure reading at ground level, all other bets are off.

If all dropzones were are seal level, it would be a different story. But they are not. And if the AAD is really going to fire at a particular AGL altitude, it MUST have an accurate idea of what the MSL altitude of the field is.

So, Dave, simply, is the barometric lapse rate linear or not? I do not believe it is. And if it is not, then an accurate field level barometric pressure is REQUIRED for the device to work as advertised.

I understand what both of you are saying, or I think I do. Both Vigil and CYPRES calibrate 0ft as barometric pressure of X. This happens after some self tests at power on. The Vigil displays value X, where as CYPRES does not. If CYPRES did, I wouldn't expect that value to be different than what Vigil displayed. For all AADs to function properly they would have to properly calculate the pressure at firing altitude. While there may or may not be differences in the math used. This whole discussion seems to boil down to Vigil shows you, CYPRES doesn't.

Is that right?

[PiLFy 0]

Aren't there hand held barometers that are accurate enough to check the sensor's readings? I would think there would be.

I've contacted Vigil once before. Vigil firing altitudes add another 260ft "To account for all possible body positions." Maybe that's rhetoric for a safety cushion?

[davelepka 4]

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So, Dave, simply, is the barometric lapse rate linear or not? I do not believe it is. And if it is not, then an accurate field level barometric pressure is REQUIRED for the device to work as advertised.

I don't know one way or another what any of the AADs do with their info, I was just tryning to help clarify what Vladi said -

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the Vigil will use the current pressure from the location where you start it up as a reference, so actual pressure used in QNH settings (in military or aviation applications) is irrelevant

The point of the inquiry was to question if the pressure readout that the Vigil can present is a valid form of 'user test' to see if the sensor is working properly. That is the notion that was put forth by the pro-Vigil crowd, and it was proposed a point in their favor over the Cypres, which they claim only test the sensor once every 4 years.

My only point is that as Vladi indicated, the Vigils baseline pressure reading is not based on it's accuracy against an outside barometer, but based on it's own baseline obtained at start up. If, for example, a sensor in a Vigil (or Cypres for that matter) was to read a full point different than what the weather service is reporting, it's irrelevant as long as the sensor is able to read the pressure accurately with regards to the baseline reading obtained at start up.

The end result of that is that using that reading as an indicator of sensor accuracy is not effective unless you chart the sensors reading in comparison to the weather services report over a period of several days, and then note the difference between the two. You can then calculate if the difference is of the correct value on a given day. Anything short of that is a shot in the dark as to the accuracy of the sensor, and even if should chart the pressure difference across several days and make the comparison, that reading says nothing to the sensors ability to read the changes accurately.

The ability of the sensor to read the pressure changes as the jumpers go up and down is left to the invisible and unknown (to the jumper) self-test in both the Vigil and the Cypres.

Yes, the Vigil can provide a single point of data, that can be employed (with significant effort) to determine the sensors ability to measure a static barometric pressure, and the Cypres can not.

Of course, the Cypres can tell when you open the door of an airplane, and knows not to fire, where the Vigil cannot always make that claim.

Take your pick.

[billvon 2,396]

>Aren't there hand held barometers that are accurate enough to check
>the sensor's readings?

Your airplane likely has an excellent (and calibrated) pressure sensor in its instrument panel in a prominent place, accurate down to about 40 feet or so.

>Vigil firing altitudes add another 260ft "To account for all possible body
>positions." Maybe that's rhetoric for a safety cushion?

It's the usual "lower pressure in the burble" issue. Sensed altitude depends on body position, so it's always a compromise between firing too high when on one's back (or when deploying) and firing too low when belly to earth.

[billvon 2,396]

>So, Dave, simply, is the barometric lapse rate linear or not? I do
>not believe it is.

No, but it's pretty close at the altitudes we jump at. (See chart below and note that it's an almost flat line from 0 to 30K feet.) Thus the sensor being off by 1000 feet absolute doesn't have much impact on overall accuracy.

[Nelyubin 0]

The User’s Manual on page 10 is written

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In practice, you must be aware that the Vigil® always acts based on a measured air pressure and time.
Those 2 parameters permit the calculation of the exact altitude, in function of the registered air
pressure, as well as the vertical speed related to a pressure variation in a certain period of time.
For information: The Vigil® is able to register pressure differences of 0, 1 hPa which is equivalent to
an altitude difference of only ± 2,6 feet (or 0,8 meter)!
Important remark: The sensor registered pressure will vary, in function of the skydiver position (face
to earth or on his back) up to 10 hPa (=mbar) equivalent to 260 ft (80m)!
Example: Let’s consider two skydivers in free fall, at exactly the same altitude but one is falling back
to earth and the second one is falling face to earth.
The influence of their falling position on their respective AAD reading is as follows

Back to earth
Depression zone
No influence
Pressure sensor location
Pressure = X hPa
Vigil® will register a pressure of X hPa
The stated or real altitude Y ft (or m)


Face to earth
AAD or pressure sensor
located in depression zone
Pressure = X hPa – 10 hPa
Vigil® in depression zone will register an up to 10 hPa
lower pressure, notwithstanding they are at the same level
The stated altitude Y +260 ft (or +80m)

[riggerpaul 1]

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I understand what both of you are saying, or I think I do. Both Vigil and CYPRES calibrate 0ft as barometric pressure of X. This happens after some self tests at power on. The Vigil displays value X, where as CYPRES does not. If CYPRES did, I wouldn't expect that value to be different than what Vigil displayed. For all AADs to function properly they would have to properly calculate the pressure at firing altitude. While there may or may not be differences in the math used. This whole discussion seems to boil down to Vigil shows you, CYPRES doesn't.

Is that right?

Mostly yes - that the Vigil (and Argus) will show you, and the CYPRES will not.

But another question is whether or not knowing has any benefit. Dave and Abedy don't feel it is relevant, but for different reasons.

If I understand correctly, Abedy says that you need two points to check the accuracy of the sensor, while Dave says that the value that comes off the pressure sensor doesn't really matter much in the first place, because what is interesting is the change, not the exact value.

I agree with Abedy that a real calibration requires more than just the field elevation value. But I feel that even knowing that the field elevation barometer is better than not.

For Dave's thoughts, I think that if he is right, then we don't really have the full story regarding actual firing altitudes in the first place, because my understanding is that the pressure difference between the field elevation and the firing altitudes is not a constant value. That is, the pressure difference from sea level to the firing altitude is not the same, for instance, as the pressure difference from 5000 feet to the firing altitude.

[riggerpaul 1]

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That is the notion that was put forth by the pro-Vigil crowd, and it was proposed a point in their favor over the Cypres, which they claim only test the sensor once every 4 years.

Please don't presume that this discussion revolves around anyone's pro-Vigil or pro-CYPRES position.

I believe that the knowledge of the pressure sensor data is valuable, regardless of my actual dislike for the Vigil.

I'd rather have a CYPRES than a Vigil, but I'd prefer that all AADs are more transparent and verifiable than they seem to be today.

(I'd rather have an Argus than a Vigil too, but that is a different discussion.)

[riggerpaul 1]

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>So, Dave, simply, is the barometric lapse rate linear or not? I do
>not believe it is.

No, but it's pretty close at the altitudes we jump at. (See chart below and note that it's an almost flat line from 0 to 30K feet.) Thus the sensor being off by 1000 feet absolute doesn't have much impact on overall accuracy.

Thanks for the chart. "How close is pretty close?" is the next question.

I consulted some pressure information on the internet. I don't personally know which sites are better or not, but here's the gist of what I found.

Different AADs use different firing altitudes. So, for simplicity, I only examined what happens when you talk about 1" of hg difference at different altitudes. I used sea level and 5000' field elevations, again, for the sake of simplicity. (From my piloting days, I remember a rule-of-thumb of 1" per 1000 feet. Since 1000' is pretty close to the AAD firing altitudes, I decided to use that number.)

At sea level, a pressure difference of 1 inch of mercury is approximately 938 feet.

At 5000', a pressure difference of 1 inch of mercury is approximately 1091 feet.

So, if an AAD uses a linear lapse rate for determining the firing altitude, and a constant difference of 1 inch of mercury, it would fire 153 feet higher at 5000 feet than it would at sea level.

I'll admit - that's less than I thought it might be. But I don't think it is negligible.

There are two different concerns here.

One regards how much off a sensor could be and still give reasonable data upon which to base a firing decision. It seems that the 1000 foot difference you mention would not make a significant difference in the firing altitude.

So on this point, I guess we'd agree that the difference is insignificant.

But the other concern is that we should have the right understanding of where the device will fire over the whole range of altitudes at which we might be using the device.

If a linear lapse rate is used, then I can expect that I'll see as much as a 150 foot difference in the firing altitude between sea level California, and 5000 foot Denver.

And if the sensor has the 1000 foot error you mention, the firing altitude difference in Denver could be as much as about 187 feet higher than at sea level.

Those numbers are significantly different from what most of us think our AADs will do. If that's the way things really work, then I'd much prefer that the AAD manufacturers would have told us long long ago.

But if they use a "proper", non-linear, lapse rate, the differences would seem to be insignificant. The 1000 foot error you mention would result in about a 37 foot difference in firing altitude.

There's no question that such a difference is effectively insignificant.

[antonija 0]

http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/barfor.html

All you need is ground altitude, firing altitude and temperature (for this simplified formula using constant temperature).

BUT since temperature is never constant (usually decreases with altitude but sometimes can do funny stuff), air composition (and its average molar mass) is never constant and because local weather phenomena can change pressure as well I'd say someone's got quite a lot of math in front of them to figure this one out. Have a good one!

For what it's worth, IMO all AADs approximate pressure change to a single curve (linear or probably something very close to linear). Furthermore, the only way AADs can check themselves is (again IMO) one-point only (pressure at ground level), so this self-check is (at best; yup, IMO again) just a check to see if sensor is sending back data and (maybe) if received data seems logical or not.

I see some people really like to see numbers on their screens and compare them to some other numbers they hear from folks at DZ (or read of the barometers), but in the end that "check" is not worth much (except maybe as an excuse to not loose in court).

I understand the need for conformity. Without a concise set of rules to follow we would probably all have to resort to common sense. -David Thorne

[riggerpaul 1]

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http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/barfor.html

All you need is ground altitude, firing altitude and temperature (for this simplified formula using constant temperature).

BUT since temperature is never constant (usually decreases with altitude but sometimes can do funny stuff), air composition (and its average molar mass) is never constant and because local weather phenomena can change pressure as well I'd say someone's got quite a lot of math in front of them to figure this one out. Have a good one!

For what it's worth, IMO all AADs approximate pressure change to a single curve (linear or probably something very close to linear). Furthermore, the only way AADs can check themselves is (again IMO) one-point only (pressure at ground level), so this self-check is (at best; yup, IMO again) just a check to see if sensor is sending back data and (maybe) if received data seems logical or not.

I see some people really like to see numbers on their screens and compare them to some other numbers they hear from folks at DZ (or read of the barometers), but in the end that "check" is not worth much (except maybe as an excuse to not loose in court).

Do you agree that using a linear lapse rate would result in increasing firing altitudes as ground elevation goes up? I was not trying to do the math myself, but consulted tables and an online barometer calculator thingy I found.

Do you know that AADs have temp sensors and use them? If so, wouldn't being buried inside the reserve container mean that they get significant lag in temp change readings? Unlike pressure, temp would need either real air movement through the rig, or a quick transmission rate from outside the rig to inside, no? Either seems unlikely to me. In a nutshell, I don't believe they use temperature - it is simply too unpredictable. For instance, in a cold climate, the rig is stored inside, and the AAD is turned on inside. Then you go outside. How long do you think it would be before the AAD sees an accurate temp?

Anyway, thanks for the insights.

[holie 0]

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...Do you know that AADs have temp sensors and use them? If so, wouldn't being buried inside the reserve container mean that they get significant lag in temp change readings? Unlike pressure, temp would need either real air movement through the rig, or a quick transmission rate from outside the rig to inside, no? Either seems unlikely to me. In a nutshell, I don't believe they use temperature - it is simply too unpredictable. For instance, in a cold climate, the rig is stored inside, and the AAD is turned on inside. Then you go outside. How long do you think it would be before the AAD sees an accurate temp?

Anyway, thanks for the insights.

As the vigil manual tells us:
"3.5.5. «INFO» Menu (Information)
This menu allows you to display your Vigil
®’s reference parameters (version, date of manufacture and
serial number), data of previous jumps, as well as temperature and atmospheric pressure. "

blue sky