Reliance on altimeters

[Piece 0]

As many people probably know, there has recently been a 4-way CYPRES fire due to what appears to be a loss of altitude awareness. Many of the current responses in that thread amount to: use your eyes instead of your gadgets. I've been thinking about this and I want to float the following thoughts I have on this topic to hopefully get some meaningful critique.

Before I say anything else I will say this: if I am in freefall and I look down and see something that looks below my usual deployment altitudes (3000'-4000'), especially if I am beginning to get substantial ground rush, and I do not have a very strong reason to believe my altimeter is not malfunctioning, I will deploy (hopefully, although this is a different discussion) the correct parachute. Please do not bash me on the head about this. I am not planning to go in staring at my altimeter with my hands on my handles, or in any other way for that matter.

Having said that, I am unconvinced that it is wise to not rely on a mechanical altimeter to measure altitude. The human brain or any of its ancestors as far as I know never had to measure altitude, only distance. We use our brain to navigate our environment on the ground and it does not matter much exactly how far away something is if it's more than a few hundred feet. I do not know the exact numbers but, from my experience, depth perception becomes more and more limited with distance. By depth perception here I mean primary cues that measure the exact distance, such as stereopsis or parallax, and not secondary cues that infer distance from other things.

As far as I know, and again I can be wrong, there are no primary cues that our brain can use to measure altitudes like the ones in skydiving (see http://en.wikipedia.org/wiki/Depth_perception). The only primary cue that I can believe could work in skydiving on this list is kinetic depth perception - measuring distance from the speed with which object size changes. This is, presumably, one of the causes of ground rush. Arguably though, this still requires the brain to assume something about the size of the object to begin with and so may actually be somewhere between a primary and a secondary cue. It is always possible that there is some major undiscovered mechanism that is not on this list but I don't know if I'm willing to bet my life on that.

As a result, when we train our brains to recognize altitude we train our brains to recognize a myriad of visual cues that are only symptomatic of altitude in our current location and environment: the area of the fields, the diameter of the treetops, the widths of roads. Here's my punchline. It seems to me that this is just as likely, if not more likely, to "malfunction" than a mechanical altimeter. What if you unconsciously train yourself to recognize altitude by the "visible length" of (angle subtended by) the runway, as one poster on this forum did? If you start at a DZ where the runway is long and then move to a DZ where it is short, your eyes will start lying to you. What if all the farmers around the DZ decided to plant corn one season and wheat the next?

Perhaps even more importantly, mechanical altimeters malfunction randomly and those malfunctions can often be easily detected. On the other hand, if your eyes ever do malfunction it will be at the worst possible time: you are at a new DZ, you're jumping at dusk or dawn, you're on a solo and have less chance of realizing your mistake, etc. Don't forget that you can always wear more than one mechanical altimeter but you've only got one set of eyes. Of course, all of this has little to do with altitude awareness on the whole since usually the problem seems to be that whatever method people use to measure altitude, they forget to check it.

To summarize, we wouldn't rely on just our bodies to take the role of a parachute. Is it really that wise to rely on our eyes to take the role of an altimeter? Or is this, like many other things, more part of our tradition? As of right now, while I spend most plane rides training myself to recognize break-off and deployment altitudes visually and I can do it quite well in the plane, I do not expect myself to be able to do it accurately. In other words, unless I am in serious danger, I will trust my altimeter over my eyes. This is doubly true if I am at an unfamiliar DZ or in unfamiliar lighting conditions.

False confidence and complacency are grave dangers to skydivers. With this in mind, please try to limit replies that mostly consist of slogans or arguments of the form "it works for me and I'm a ninja."

http://icanhascheezburger.com/2008/02/28/funny-pictures-i-come-with-sarcasm/
Proudly uncool since 1982.

[DBCOOPER 1]

Its really pretty simple. Little houses wait, big houses pull...

Replying to: Re: Stall On Jump Run Emergency Procedure? by billvon

If the plane is unrecoverable then exiting is a very very good idea.

[Piece 0]

That's not what I'm trying to say here. Altitude awareness means more than just "big houses pull." My point is: your eyes are definitely another way to break the links in the chain that lead to an accident but should you really believe them over an altimeter during an otherwise normal jump? If an RW jump plans to break at 4000' and I am used to breaking at 5500' and trained my eyes to do that, unless I believe my altimeter, I'm likely to break at 5500' anyway just like I see freeflyers of all skill levels do. I've watched people with thousands of jumps do this. Breaking high on a large RW jump and disappearing from the group is not necessarily a safe practice.

I view my eyes the way I view my audible: it's a useful tool but I wouldn't completely rely on it. If I hear the siren in my audible, I will pull. If the houses are big, I will pull. But there's more to skydiving than that. Don't people typically lose altitude awareness much earlier in the skydive?

http://icanhascheezburger.com/2008/02/28/funny-pictures-i-come-with-sarcasm/
Proudly uncool since 1982.

[Tuna-Salad 0]

However useful it may or may not be. On the ride to altitude I compare my alti with that of the cockpit (if possible) and also mark where we pass clouds. That way knowing my instrument was accurate at the time so in the event of a failure I still know.. "we passed clouds at 4,000 feet". Maybe this is stupid or a mistake to be doing.

Millions of my potential children died on your daughters' face last night.

[Piece 0]

One dude I knew did that. Around 1000 jumps, no audible. He was videoing a 4-way and cloud base was, I think, 4000' when they were going up. He entered the clouds (sorry, industrial haze) and his alti fogged up. He thought "no biggie, just wait out the cloud and pull". Well, once the cloud broke he crapped his pants cause he was at 1000'. He went straight to his main like everyone who actually were in this situation seem to do. CYPRES popped his reserve, he chopped the main right away. His main risers snagged on the reserve lines and the main streamered behind him, thankfully it did not choke the reserve. I was scared to death watching him land.

Lessons I learned: know what cloudbase is but don't rely on it, it can change quickly. Check your alti before going into a cloud. Stay aware in the cloud. Don't fuck up but wear an audible in case you do. Better yet, don't go if there are clouds at break-off though this is a conversation for a different thread.

http://icanhascheezburger.com/2008/02/28/funny-pictures-i-come-with-sarcasm/
Proudly uncool since 1982.

[MarkM 0]

Every time my Neptune has failed it froze the screen at a set altitude or setting.

I once passed opened tandems at 10k, thought to myself "huh they opened high, wonder why" and then noticed my Neptune wasn't moving from 10k.

I trust my eyes, internal clock, audible, what other jumpers are doing, open canopies and not just once source of information.

[billvon 2,400]

>Is it really that wise to rely on our eyes to take the role of an altimeter?

I think it is. Having your eyes as a primary source of altitude information, and a visual or audible altimeter as a backup, is a great way to ensure that you are both altitude aware and have a backup. Eyes cannot function as backups unless you train them, and using them on every jump is a good way to train them.

[PeregrineFalcon 0]

Just this weekend, I had my AFF level 5 and 6 jumps. While gaining alt on the first jump, I noticed the needle not moving. My JM gave me his altimeter. He said he had a back up in his camera. He then showed me how to test it while still on the ground.

For the second jump, I grabbed another altimeter and strapped it to my wrist. I then decided to take it off and test it. It wasn't a real altimeter. It was the practice one they use in training. Push the button and the needle moves. It was a timer!! I'm sure that would have been helpful.

[NickDG 23]

>>It was a timer!! I'm sure that would have been helpful.
LOL, actually on a belly flight, and if you set it to your jump altitude and pushed the button once out the door, it wouldn't be that far off. After all what is it? It's a clock. And at one time skydivers used stop watches all the time to skydive . . .

NickD

[IanHarrop 37]

I trust my eyes and brain more than I trust any mechcanical or electroninc devices.

Anything made by man will break.

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

[jsaxton 0]

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Breaking high on a large RW jump and disappearing from the group is not necessarily a safe practice.

It's a VERY unsafe practice.

[PeregrineFalcon 0]

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>>It was a timer!! I'm sure that would have been helpful.
LOL, actually on a belly flight, and if you set it to your jump altitude and pushed the button once out the door, it wouldn't be that far off. After all what is it? It's a clock. And at one time skydivers used stop watches all the time to skydive . . .

NickD

That's true, but here's the thing. I'm told I have a very fast fall rate. I'll learn to slow it down soon. That brings me to a question. If a belly flyer had a big arch and fall rate, how many seconds would they shave off a free fall of say...8,000 feet? I know the answer is "it depends" but what's the fastest a body can go in belly flying and freflying?

[millertime24 8]

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After all what is it? It's a clock

I was always under the impression that an altimeter was a barometer.

Muff #5048

[svdree 0]

Looking at the ground for altitude awareness may not always be practical. I can imagine that most hardcore 4-way competition jumpers don't take the time to check their altitude during the dive; they probably just go until they hear the beep. Or take VRW camera flyers; looking up at the formation from some weird headdown position does not give you a lot of opportunity to regularly check the ground.

Even then: your eyes may not be as trustworthy as you think. Devices fail, but people make mistakes too. What if you're on a new dropzone, where the visual clues are totally different? What if the ground is covered in snow? What if low clouds came in during the ride to altitude? Sure, if you think that you're lower than what your altimeter tells you; by all means, pull. But only relying on visuals doesn't seem that safe.

Also, I think a lot of people are a bit quick to dismiss this 4-way cypres incident as a stupid mistake of some idiots that shouldn't be allowed to skydive to begin with. If you think that something like this couldn't possibly happen to you, you may be overestimating your abilities. I read some comments of people who said that if you wouldn't do a jump without your devices (alti's, audibles, AAD's), then you shouldn't be doing it at all. Personally, I jump with a wristmount altimeter, 2 audibles and a cypres. I don't care about the cypres (it's just that you have to have an AAD at my favorite DZ), the alti comes in handy sometimes, but the audibles are just indispensable. I'm doing most jumps in inverted positions (headdown, tracing), and most of the time I only see the ground just before deployment. I would definitely not make these kinds of jumps without my electronic gadgets. Does that make me unsafe?

[strop45 0]

I think that you made some very good points and wonder whether many of the "train your eyes" replies actually read your post.

It seems to me that using both your eyes and your alltimeters gives you the best result. Whether you use your eyes to check the mechanical/electronic or vica-versa seems like a moot point.

One issue seems to be people who don't use either their eyes or look at their visual altimeter and rely on their audible. At least if you are using a visual one, you have a chance to pick up that its has failed. Regardless of everything else, using your eyes and knowing when you left the plane, you have a sense of how high you are and can tell if the altimeter is working. or showing nonsense.

If you rely on an audible and it malfunctions, isn't turned on, set to the wrong height, fails off your helmet, or you don't hear it, then you are asking to become another post in the incidents forum.

Personally, I'll keep using my eyes, my commonsense (my time sense was destroyed recently by flying a wingsuit, which made me check my altimeters with my eyes more than normal), my altimeter and my audible (set to 500' less than breakoff).

Wayne.

The difference between stupidity and genius is that genius has its limits." -- Albert Einstein

[Broke 0]

Stratostar can explain how to do it better than I can. Do a couple of jumps where you look at the horizon and note what it looks like at different altitudes.

Divot your source for all things Hillbilly.
Anvil Brother 84
SCR 14192

[CMiller 1]

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>Is it really that wise to rely on our eyes to take the role of an altimeter?

I think it is. Having your eyes as a primary source of altitude information, and a visual or audible altimeter as a backup, is a great way to ensure that you are both altitude aware and have a backup. Eyes cannot function as backups unless you train them, and using them on every jump is a good way to train them.

Honestly though, how many jumpers check the ground during their skydives other than during the track, and the spot? If you're doing RW, you're focused on where you and everybody else is. Checking your wrist altimeter is simple during a move or whatever, but I don't think checking the ground is quite as easy or as useful.

[kelpdiver 2]

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That's true, but here's the thing. I'm told I have a very fast fall rate. I'll learn to slow it down soon. That brings me to a question. If a belly flyer had a big arch and fall rate, how many seconds would they shave off a free fall of say...8,000 feet? I know the answer is "it depends" but what's the fastest a body can go in belly flying and freflying?

Classic belly speed is 120, fast might be 135 ? Freeflying goes 160 and up.

I think you're saving 5-10 seconds off on a full jump from 13-15k, down to 3.5. Which is about the same you shave off going from a DZ that does 14-15k normal as opposed to a place like Perris/Elsinore where they do 12.5 typically because of the higher ground elevation. That difference does throw me at times - jumps seem to end a bit early. However, if I'm at Elsinore, I'm probably doing a busier RW jump, so it also seems faster.

When I demoe'd a neptune, I was seeing times in the high 40s while the chart would suggest low to mid 50s, but there could be error there in the pull altitude or when the neptune stops counting.

[Piece 0]

I saw, with my own two eyes, a bellyflyer in the tunnel at Eloy surrounded by freeflyers in a slow sit or headdown. They were flying no contact, this was not the usual kind of hybrid. The bellyflyer was not heavy or short, he seemed to have an athletic tall-ish build. He was, however, bent almost in half at the waist and was falling straight down the tube. They looked like they were doing maybe 150mph, its hard for me to say since I don't jump with a Neptune and don't have a clear idea just how fast what kind of sit is.

http://icanhascheezburger.com/2008/02/28/funny-pictures-i-come-with-sarcasm/
Proudly uncool since 1982.

[Piece 0]

It seems like using the horizon for visual cues introduces even more variables we can't control. Cloud formations, haze and sunsets can really change what the horizon looks like, even in the course of one day. Then again, I'm quite certain that I've trained myself, mostly unconsciously, to recognize 6000' since I always seem to check my altimeter at that exact point.

It would be interesting to hear if pilots know anything that I/we don't about recognizing altitude visually.

http://icanhascheezburger.com/2008/02/28/funny-pictures-i-come-with-sarcasm/
Proudly uncool since 1982.

[yarpos 4]

there is no one answer...with experience you get better at this....now we have mutiple tools, eyes, audibles, altimeters but we can still make mistakes...its part of the sport. And then of course there are night jumps. I can assure you its pretty stomach churning to see the same altitude again when in freefall after admiring the city lights for a while.....arrrggh!!! this was olden days before audibles when an alti was all you had at night apart from your sense of time, if it was a dark night.

regards, Steve
the older I get...the better I was

[popsjumper 2]

Put me solidly in the "train your eyes" camp.

It's nice to know that the alti played such an important role in training my eyes in the first place and using it has it's benefits but when push comes to shov it's eyes that I depend on. All those gadgets are nice and they are tools to be used. IMHO, it's the eyes that are the most dependable.

In training your eyes, you should be training them in the realm of the "big picture" not on some specific feature at any one particular DZ.

If you've got time to glance at an alti, you have time to glance at the ground.

My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239

[Baksteen 84]

I've got an altimeter, an audible, a time sense and my eyes any of which might fail me for whatever reason whenever I least expect it.

I was practicing tracking when I had only a few freefals under my belt (SL student) and therefore had no timesense to speak of. I was trying to assume the tracking position but had trouble to get going. Of course I couldn't see my altimeter as my hands were behind me and since I was jumping only for a short time I didn't have an audible yet.
However, at some point I looked down and had the bigest scare of my life. I immediately pulled and found myself in the saddle and under a fully functional main at 2500...

"That formation-stuff in freefall is just fun and games but with an open parachute it's starting to sound like, you know, an extreme sport."
~mom

[virgin-burner 1]

“Some may never live, but the crazy never die.”
-Hunter S. Thompson
"No. Try not. Do... or do not. There is no try."
-Yoda

[kallend 1,623]

Quote

I saw, with my own two eyes, a bellyflyer in the tunnel at Eloy surrounded by freeflyers in a slow sit or headdown. They were flying no contact, this was not the usual kind of hybrid. The bellyflyer was not heavy or short, he seemed to have an athletic tall-ish build. He was, however, bent almost in half at the waist and was falling straight down the tube. They looked like they were doing maybe 150mph, its hard for me to say since I don't jump with a Neptune and don't have a clear idea just how fast what kind of sit is.

I saw, with my own two eyes, two sit flyers occupying "rooms" in a 104 way RW formation at Perris (does this count as the largest ever hybrid dive?). I think quade might even have the picture. Fall rate was around 120.

...

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