Neptune 2 freefall times while wingsuiting

[stevemeg 0]

I have a Neptune 2 that I jump with and I have a question.
Since I've been working on my wingsuit technique, trying to fly longer (fall more slowly), I started having jumps where my neptune records something like 16 seconds of free fall when it's actually 150-170 seconds. It records my freefall speed as 35 mph.
So here are my questions:
Is 35 mph as low as the neptune will record? Is freefall speed even accurate in that range?
I assume the problem (not recording accurately) is that I'm falling slowly enough that the neptune doesn't recognize the wingsuit flight as free fall so it doesn't record it. Is there an update that will allow it to record freefall time (exit to deployment) on a long wingsuit flight?
If the Neptune just won't do it, what audible/freefall computer will?
Thanks

[wingit 0]

A video camera. And set you neptune 2 to log canopy flight for your freefall speeds.

[LouDiamond 1]

Is your Neptune set to Wingsuit mode?

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

[lurch 0]

To date, no device I've ever tried could accurately and reliably detect the real freefall time. I've had a Protrack, a Neptune 1, Neptune 3, Altitrack...

Any seriously long flight, the device is going to mistake a slow burst fallrate for a deployment. The 35 is fairly accurate, enough for our needs anyway, when I've done flights right at the threshold of deployment detection error the math, (time of flight vs altitude descended) worked.
The cutoff threshold is inconsistent, I don't think its just a number, I think its an equation tied to rate-of-change but gets repeatably screwed by the low-30's and below. With a suit the size of an Apache you can go low teens and single digits just by digging in your wings the right way and all my gear records deployment the moment I seriously spread my wings. That suit makes it easy to do flights in which the fallrate never broke high-30's the whole way down. Altimeters think it was a hop-n-pop.

The only gadget I've found truly useful for recording freefall times fallrates 40's and below has been the Altitrack. It detects, or misdetects deployments just as easily as the others do, but its' key feature is, it records fallrate not in just a few samples like a Neptune or Protrack, but sampling 4x a second all the way down, including a clock timer and it will play it all back for you in slo-mo or realtime. It lights up a little parachute icon at the point in the jump where it thinks you deployed, and states your freefall time based on that point, but it just keeps recording all the way to the ground.

You can speed up and slow down the playback at will to see moves played back frame by frame, and identify the end of the jump by approximate pull altitude and observing the speed changes- I'll be cooking along at a steady 25-28 mph, go to pull at 3500 and the altitrack shows sudden fallrate jump to 40's, 50's, followed by a sudden slowdown to a solid 16 mph and stays there... canopy speed. Identify what your own canopy speed is. Label the first 1-2 seconds of that speed "jump end" and compare the results to video. I've found it consistently agrees with video down to about 2 seconds... sometimes takes it a second or two to detect your exit, for example, so the altitrack might tend to leave out a few seconds, video shows flight was 3:55 exit to opening, altitrack counts 3:52 because it took a bit to notice it was descending... sometimes if I delay wingspread, it'll detect freefall sooner and it agrees with video down to the second. Anyway its the best way I know to get a halfway accurate freefall time, and for flights of 4:00-4:30 and beyond, plus or minus a few seconds is close enough anyway.
-B

Live and learn... or die, and teach by example.

[IanHarrop 37]

have you considered

http://www.flysight.ca/

"Where troubles melt like lemon drops, away above the chimney tops, that's where you'll find me" Dorothy

[LouDiamond 1]

Lurch, without getting into a lengthy explanation, you are on track as to the explanation of why. I worked with Alti-2 some years back on this issue and short story is that it is a mathematical algorithm issue with how the unit interprets all of the data it is gathering at that split second in time and where it thinks it will be in the next. The solution was identifying a certain set of parameters associated with wingsuiting and identifying the line in the sand so to speak on what is and isn't considered a deployment. It's a trade off as too tight/too loose a set of parameters you sacrifice reliability/accuracy. This is what lead to the creation of the wingsuit mode and fix for the issue. Now the caveat to that is that while it does work most of the time, there are always circumstances where you might see the unit being tricked into thinking the jumper has deployed a canopy while set in wingsuit mode. But these can typically be identified as they occur on exit or shortly after and or after a prolonged dive followed by a rapid slowing down (opening wings all the way).

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

[normiss 620]

Are you still up to date on the software?

There have been a number of updates, fixes, enhancements, and changes since you were jumping.

[Di0 1]

LouDiamond

Lurch, without getting into a lengthy explanation, you are on track as to the explanation of why. I worked with Alti-2 some years back on this issue and short story is that it is a mathematical algorithm issue with how the unit interprets all of the data it is gathering at that split second in time and where it thinks it will be in the next. The solution was identifying a certain set of parameters associated with wingsuiting and identifying the line in the sand so to speak on what is and isn't considered a deployment. It's a trade off as too tight/too loose a set of parameters you sacrifice reliability/accuracy. This is what lead to the creation of the wingsuit mode and fix for the issue. Now the caveat to that is that while it does work most of the time, there are always circumstances where you might see the unit being tricked into thinking the jumper has deployed a canopy while set in wingsuit mode. But these can typically be identified as they occur on exit or shortly after and or after a prolonged dive followed by a rapid slowing down (opening wings all the way).

Classic Kalman Filtering predictor/estimator problem. I like it! :)
Now, one way to improve the way this works would be to throw an IMU into the mix. Now, that will work. But even by using a sold state mini IMU, is it worth the increase in size, weight, power consumption and cost that the new logger would need? I say hardly. But that would reliably solve the problem once and for all, since the logger would be able to detect at any given time the attitude of the flyer, and that will easily distinguish between wingsuit flying and canopy flying (that 100+ mph horizontal speed will easily do the trick).

I can see why a kalman filter that can work only with barometric pressure and differential has a hard time detecting configuration changes between wingsuit flying and canopy flying, those having similar flying characteristics over time, if your only data is vertical pressure variation.


That being said, I'm very tempted to build my own logger, at the end of the day, that was my job until a couple of years ago. Applied to UAVs, not, well, people. But same concept.

The next logical step, is sticking a Pitot Tube on your helmet.

I'm standing on the edge
With a vision in my head
My body screams release me
My dreams they must be fed... You're in flight.

[phoenixlpr 0]

Quote

The next logical step, is sticking a Pitot Tube on your helmet.

I'd say jump with camera and you can find out the freefall you had from the video.

[Hellis 0]

Di0

The next logical step, is sticking a Pitot Tube on your helmet.

I believe there was a post about that a few years ago.
Yuri was the username if I remember correct, built one and mounted it on the chest.

Can't remember all the details.

[SkymonkeyONE 3]

Yuri, like five/six years ago was playing with a device that acted like a pitot tube when stuck out from the chest of his wingsuit.

PS: where's Yuri these days?