Max Track - AltiTrack Graph

[sraja 0]

Got out of the otter at 13500, went into a max track right out of the door. I felt myself potato chipping so I got out of the track and then went right back into it. On the second track after a few seconds the velcro covers on my Havok helmet blew open on the right and left sides. The flapping noise was really irritating and so I stopped and pulled at the appropriate altitude. I covered a lot of ground too vis-a-vis I checked the deploy spot versus the exit spot.

Now, I had my altitrack with me and it recorded a minimum fall rate of 75mph and an average of 112mph. The graph has me confused -
1. Why did I accelerate to 160mph after exit when I was in a max track position? Shouldnt I be falling slower?
2. The second track is when the altitrack recorded the minimum fall rate - anyone here seen anything similar? Some people at the DZ said it could be because my altimeter was in a burble - but everything else about the graph looks perfect. The low fall rate combined with the high forward speed is probably what blew my velcro covers open (atleast I'd like to think so)
3. Anyone here who has max tracked with an alti-track see anything odd on this graph? Someone recommended that for the most accurate readings I should have the altitrack on my ankles - that way it has the least intereference from the burble.

Thanks in advance

[sraja 0]

And for more details on my body position during the track so that someone can comment on possible burble interference

1. Shoulders cupped
2. Toes pointed
3. Hands inverted - meaning my altimeter was perhaps at sometimes facing the ground instead of the sky
4. Belly sucked in
5. Dearched at the hip
6. Tightening up my entire body so much that it pained for the entire track

[JeepDiver 0]

If you reached 160 on exit my guess would be you went head extremely low in a steep dive, which I would venture a guess also blew your velcro covers open.

The low fall rate speed is because you went to your belly.

I have used an altitrack for over 250 jumps, 75 mph is extremely slow. I doubt that reading.

Based on the graph your fall rate was never constant which would reflect a stable flat track. Good effort but you need more stable tracking jumps. Keep trying.

I average 106 in a flat track, can get it as fast as needed. 126 is normal for me if I need a swooping track to get to the lower leader, when I stop the track I'll reduce my fall rate to about 95-100 before dumping.

Yesterday I exited from 13,300, dumped at 3000 and the tracking dive lasted 71 seconds. I don't have the altitrack software to upload my data however. My longest flat track time-wise was 84 seconds. I do wish I had the software to show you the graph.

I always wear it ion my left hand. I see no need to put it on the ankle.

What is important is the degree of difference in speeds. 160-75-112 for your tracking jump does not show a great deal of stable control.

Try to maintain a constant fall-rate speed in the 105-115 range for the entire tracking jump.

[kallend 1,623]

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If you reached 160 on exit my guess would be you went head extremely low in a steep dive, which I would venture a guess also blew your velcro covers open.

The low fall rate speed is because you went to your belly.

I have used an altitrack for over 250 jumps, 75 mph is extremely slow. I doubt that reading.

Based on the graph your fall rate was never constant which would reflect a stable flat track. Good effort but you need more stable tracking jumps. Keep trying.

I average 106 in a flat track, can get it as fast as needed. 126 is normal for me if I need a swooping track to get to the lower leader, when I stop the track I'll reduce my fall rate to about 95-100 before dumping.

Yesterday I exited from 13,300, dumped at 3000 and the tracking dive lasted 71 seconds. I don't have the altitrack software to upload my data however. My longest flat track time-wise was 84 seconds. I do wish I had the software to show you the graph.

I always wear it ion my left hand. I see no need to put it on the ankle.

What is important is the degree of difference in speeds. 160-75-112 for your tracking jump does not show a great deal of stable control.

Try to maintain a constant fall-rate speed in the 105-115 range for the entire tracking jump.

Instantaneous readings are very flaky, but averages are usually pretty good. Freefall times are also pretty good indicators

Averages speeds in the 80s are quite achievable.

Of more importance in group dives is HOW FAR can you go horizontally to achieve good separation.

...

The only sure way to survive a canopy collision is not to have one.

[saxboy 0]

I am not sure for this because I bought my altitrack a few days before and I don't test it yet,but I thing you must change the speed from "TAS" to "SAS"...
to see you "real" speed...Maybe I am wrong..

[quade 3]

Actually, "REAL" speed is TAS.

SAS is pretty bogus.

quade -
The World's Most Boring Skydiver

[saxboy 0]

Ok!
But according the manual the "TAS" is the "true airspeed" and "SAS" is skydiver's airspeed.
"Using SAS, skydivers in any body position can express their vertical speed by a number"

[kallend 1,623]

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Ok!
But according the manual the "TAS" is the "true airspeed" and "SAS" is skydiver's airspeed.
"Using SAS, skydivers in any body position can express their vertical speed by a number"

Marketing jargon. SAS is a fudged value obtained from the true airspeed by "adjusting" for air density.

...

The only sure way to survive a canopy collision is not to have one.

[pchapman 261]

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Marketing jargon. SAS is a fudged value obtained from the true airspeed by "adjusting" for air density.

Sorry, gotta call you on that.

Saying SAS is a fudged value is like saying that aircraft flight test data for certification & operating handbooks is fudged because they didn't actually all do the flight tests at 29.92" Hg air pressure, 15 deg. C, 0 % R.H., at Sea Level. Data is collected and then adjusted to show what the plane would be doing at some set of reference conditions like those.

The SAS concept is similar, adjusting speeds from different altitudes to compare them as if every measurement were done at 3000' in a standard atmosphere. So it is a useful adjustment to help compare numbers taken at different altitudes.

But it only adjusts for altitude assuming one version of a standard atmosphere. It doesn't compensate for air mass temperature or other non-standard atmospheric conditions, and isn't going to give professional aerospace level data quality.

I'll accept that the data is 'fudged' if you meant that it is 'adjusted in a rough manner', but won't accept it in the pejorative sense that it is likely to be taken, that 'the data is adjusted to lie to you'. The SAS numbers are more useful for comparing data between jumps and skydivers, than the raw unadjusted "TAS" numbers.

[kallend 1,623]

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Marketing jargon. SAS is a fudged value obtained from the true airspeed by "adjusting" for air density.

Sorry, gotta call you on that.

.

CALL what you like. True air speed (TAS) is the speed at which you fell (within the limits of measurement accuracy). SAS is NOT the speed at which you fell except at one particular value of air density, which may or may not have existed at all during that particular jump. Hence SAS may have the dimensions of speed, but it doesn't reflect what actually happened during the jump.

...

The only sure way to survive a canopy collision is not to have one.