crazy 0 #1 February 22, 2003 [Pruned from "Re: [AndyMan] Students jumping WITHOUT an altimeter"] QuoteYup, I'll give a case of beer to anyone with less then 400 jumps who can consistently pull within +-1000 feet of an intended altitude on a solo jump without an altimeter. You are definitely right if you assume that there is only altitude awareness and no time awareness at all. However, most people can count 20 seconds accurately (much better than +-6 seconds) with minimum ground training. Thousands of skydivers actually had to do it, and succeed, to be signed off for the next exercise: reading the altimeter and pulling at a specified altitude. A significant number of instructors used to think that even for the 20 seconds delay, the student had to jump without an altimeter, else, he would be able to cheat (you owe beer to many people :-). From this point of view, the increased safety provided by the training seems to outweight the risk of jumping without an altimeter, if any (please listo, voice your opinions about students jumping without an altimeter in the appropriate thread). I understand why some people think that jumping without an altimeter is scary. However, it's easy to understand why some instructors emphasize so much on time awareness: it's the tool that you're supposed to use to keep your altitude awareness. The only reason why you are able to keep your altitude awareness between two altitude checks is that you are aware of the time elapsed since the last altitude check (eye balled, visual alti or audible). As soon as you lose track of the time, you lose track of the altitude. Basically, people forget to pull because they lose their time awareness for a much too long duration. When you underestimate the importance of time awareness, you get funny things like: - Q: when do you first check your altitude after exit? - A: when i'm around 6000-7000 feet. Modern training and modern equipment emphasize more on altitude rather than time (altimeter vs. timer, altitude awareness vs. time awareness). However, counting consciously is an extremely valuable tool: easy to train (you can do ground training all day long while doing other activities), reliable (after a few jumps, losing the count rings an alarm) and free. At the beginning, it can be difficult to count while doing something else, but after a while, it's not even a distraction. Of course, most people are fine without counting. It's just an additional tool to the survival kit. It's much more reliable than the subconscious feeling of elapsed time (varies a lot with mood, health and activity) or eyeballed altitude guess (varies a lot with mood, health, goggles, weather, visibility, luminosity and landscape). Also works perfectly in combination with planned altitude checks (after the 4th point for instance).-- Come Skydive Asia Quote Share this post Link to post Share on other sites
listo 0 #2 February 22, 2003 Just to be the devil's advocate here for a second. Which is more important, altitude awareness or time awareness? Personally I think that they do go hand in hand, but altitude awareness is time awareness since the only time that really matters is how much time you have left before impact with that great big planet. ListoLive today as tomorrow may not come Quote Share this post Link to post Share on other sites
Liemberg 0 #3 February 22, 2003 Quote [Pruned from "Re: [AndyMan] Students jumping WITHOUT an altimeter"] Yup, I'll give a case of beer to anyone with less then 400 jumps who can consistently pull within +-1000 feet of an intended altitude on a solo jump without an altimeter. Does he own a brewery? And - more important for old farts - does past performance count? "Whoever in discussion adduces authority uses not intellect but memory." - Leonardo da Vinci A thousand words... Quote Share this post Link to post Share on other sites
riddler 0 #4 February 22, 2003 Quotemost people can count 20 seconds accurately I'm not an expert in this field, but I have to disagree with most of your "time awareness" argument. I should also say that I never did static line, or time-delayed jumps, with the exception of a few hop-n-pops (count to five, pull). I think that most people (probably a higher percentage of skydivers) feel that their perception of reality is accurate, but it's my belief that most of what we perceive is skewed from reality by many factors. One factor is excitement - the more excited we are, the more our perception is skewed. The majority (IMO) of skydiving related deaths can be attributed to mental mistakes - people that *thought* that they were right about something, when they weren't. Instruments can fail, of course, but in most cases, they are less likely to fail than our perception of reality. So, having said that - most of my skydives are 50-60 seconds. Can your arguments about 20 seconds apply to something three times as long? How about if you factor in the "excitement" of the skydive, where time appears to speed up or slow down, depending on the person and experience level. Even the most experienced skydivers can have an exciting jump that skews their perception of the time involved. I don't think altitude awareness necessarily HAS to come from an instrument, but I would trust my eyes (looking at the ground, looking at my alti) a lot more than my perception of time in an adrenaline-driven sport like ours. Right now, I'm relying on my instruments, but I have far less than 1000 jumps. This issue probably comes down to a few things. Experience, excitement and exposure. The more experience you have, the closer your perceptions are to reality - students are less likely to know their air-time than skygods. The more excited you are, the further from reality - again students, or anyone doing something new or different on a jump. By exposure, I mean air-time. Most people can probably count to five in a skydive more accurately than they can count to 60. Another thing to consider is fall-rate. Free-flying - Exit from 12,500 feet, spend the first part (the slide) in a sit. Transition to head-down for 10 seconds, then cork out and go back to a sit for 20 seconds. Flop over on your belly for 8 seconds to slow down and get ready to pull. What altitude are you at? Do you really want to do the math in free-fall? What about big-ways? A 4-way falls slower than a solo belly. Do you want to do the math? What about when the four-way funnels and you are effectively solo for part of the jump and in a group for part of it? Sorry about the long post! It's 3:15 AM right now, and I'm waiting for news on our servers at work. It's a difficult question complicated by the fact that most people have difficulty admitting they might be wrong. Can you admit you might be wrong in 5 seconds or less? Quote Share this post Link to post Share on other sites
AndyMan 7 #5 February 22, 2003 I supose I should've added one more condition to my wager, which would've been one that says the jump must've been from full altitude - 13,5. That means the second count goes from 20 to 55, roughly. A thousand feet is 5 seconds. I doubt very much that once you add in the energy and adrenaline of a jump, that people can count accurately to 55 and still be within 5 seconds of accuracy. Doing a solo jump where the jumper is mostly staring at the ground gives a huge amount of ground rush, too. And while I don't own a brewery, I AM a certified brewmaster, and still have connections at Molson.... When I made the wager I was not arguing that first jump students need altimeters, clearly in my mind, they don't. I made the wager to quiet all those who were saying that jumping without one teaches a level of altitude awareness that's good enough to bet their life on. It isn't. If you can't pull within a 2000 foot range, you shouldn't be betting your life on it. I doubt most can. _Am __ You put the fun in "funnel" - craichead. Quote Share this post Link to post Share on other sites
Liemberg 0 #6 February 22, 2003 Quote I supose I should've added one more condition to my wager, which would've been one that says the jump must've been from full altitude - 13,5. Wussing out ? "Whoever in discussion adduces authority uses not intellect but memory." - Leonardo da Vinci A thousand words... Quote Share this post Link to post Share on other sites
AndyMan 7 #7 February 22, 2003 Heh... I guess so! If I hadn't added that condition, I see a line up of people taking a 2 second delay from 4,000 and asking for beer. Which isn't all that bad. I'm pretty generous with my beer, anyways. _Am__ You put the fun in "funnel" - craichead. Quote Share this post Link to post Share on other sites
Designer 0 #8 February 22, 2003 Hey,simple,the way we did was let the student count the first 20,use the alty the next 1(2 in a day).Let himself,herself sort it out in their own minds. Quote Share this post Link to post Share on other sites
crazy 0 #9 February 23, 2003 QuoteSo, having said that - most of my skydives are 50-60 seconds. Can your arguments about 20 seconds apply to something three times as long? Great, you have less than 400 jumps, your skydives are 50-60 seconds, you are the perfect candidate for the beer (2 cases i think: 1 from AndyMan, 1 from listo). You can use a stopwatch, because they didn't specify anything about this. If you count, with minimal training you'll most probably be within the +-5 seconds as well, but it will be a long and boring jump (but it's 2 cases of beer!). [AndyMan: you thought you could save the brewery? :-)] Anyway, the point of counting is to consciously keep track of the time since the last altitude check (eyeballed, read on the alti or heared from the audible) in order to know when to do the next one. Hence, usually you don't have to count more than 20 seconds, even if your freefall is 60 seconds. It could be something like: exit, count 20 seconds, eyeball the altitude, count 20 seconds, check the alti, count 10 seconds, wave & track, count 5 seconds, wave & pull, count 3 seconds, check canopy. Of course, instead of (or in addition to) "count xx seconds", you can use other triggers for your altitude checks: time related triggers (subconscious feeling of time or planned checks), or altitude related triggers (subconscious visual reference, an audible...) QuoteHow about if you factor in the "excitement" of the skydive, where time appears to speed up or slow down, then you might count faster or slower and the track of time will be more inaccurate. A clock is a clock, a good clock is a bonus. QuoteAnother thing to consider is fall-rate. [zoo jump] What altitude are you at? Do you really want to do the math in free-fall? Counting or not, you still have eyes and an altimeter. Check on your altimeter, cross check with the ground. BTW, can you tell me when you check your altitude?-- Come Skydive Asia Quote Share this post Link to post Share on other sites
BikerBabe 0 #10 February 24, 2003 The time awareness issue is valid, I think, and not just for students. Personally, I can tell when a skydive is about to end based on how long I've been falling, but that comes with experience. If it starts to "seem long" (like we got extra altitude or something) I will glance at my altimeter just to be sure. As for students, I'm not sure if they've changed it, but where I used to teach, a student's first five jumps are 10-second unassisted freefalls. They were drilled over and over on the 10-second freefall sequence. Of course, we also gave them about 40 hours of ground school before they jumped, but the big emphasis was on counting to ten. Rather than low pulls/no pulls, what we found to be the most common occurrence was early pulls because adrenaline rush led to fast counts. There were sometimes one or two students per course (out of about 30) who forgot to count, but most counted, just too fast. I was one of the "too fast" folks, myself. As a reference, by the time I was teaching at USAFA, we were putting approximate 1000 students through the course per year. It was rare to see a main AAD fire. Usually those who "forgot to count" didn't forget to pull, they just fell longer than 10 seconds. The main AADs were set to fire after the equivalent of around 18 sec of freefall. Any current PTWOB/AM-490 grads on here care to comment?Never meddle in the affairs of dragons, for you are crunchy and taste good with ketchup! Quote Share this post Link to post Share on other sites
riddler 0 #11 February 25, 2003 Quote+-5 seconds As a free-flier, I don't think this is a good idea. We often say that 5 seconds=1000 feet, but forget that that applies to a terminal belly speed (120MPH = 880 feet/5 seconds). It's not too hard for 5 seconds to be closer to 2,000 feet when free-flying. If you amend your point to add occasionally checking your alitmeter and eyeballing the ground, then it becomes hard for me to argue with that. After all, I'm not locked-on to my alti the whole jump - I tend to check it every 5-10 seconds, and use the ol' internal clock to gauge those 5-10 seconds. I just believe that assuming your internal clock is a reliable reference is generally a bad idea. It's far too easy to distort your internal clock with other factors. But what the heck do I know? I have less than 400 jumps. Maybe after thousands of jumps, I will feel comfortable doing that. I kind of hope not. It only takes one bad jump.Trapped on the surface of a sphere. XKCD Quote Share this post Link to post Share on other sites
sfc 1 #12 February 25, 2003 i scare the crap out of myself everytime I jump at a new DZ. At home we always get 15K regular as clockwork, and I usually look at my alti at 5K just before my audible goes off. Go to new DZ where we get out at 12.5K, the audible almost always beats me on the first 2-3 jumps, when I get back home, I have a few jumps breaking off high, now this isn't scary. I think you get more used to freefall time rather than altitude, especially in vertical, where the ground isn't so in your face. Quote Share this post Link to post Share on other sites
nacmacfeegle 0 #13 February 25, 2003 " just believe that assuming your internal clock is a reliable reference is generally a bad idea. It's far too easy to distort your internal clock with other factors." I agree with the Riddler here. I have my eyes, my audibles, and my analogue alti, and my 'gut feeling' (internal body clock). The gut feeling has been way out more times than the other altitude management systems I use. The body clock thing is good if you are doing the same type of jumps, from the same altitude all the time. But I don't, I like to mix up my jumping disciplines, and I like to jump at different DZs frequently. Therefore exit alt. varies, as does 'time to pull' so the body clock, or sense of time, is not as useful to me as it is to others.. People used to jump with stopwatches mounted on their belly reserves by the way.....-------------------- He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me. Thomas Jefferson Quote Share this post Link to post Share on other sites
