March 2nd Denver avalanche victim alive after 3hr

www.denverpost.com/ci_22911190/colorado-...ading-during-3-hours

I wonder what this "pulse rate" things is all about? Perhaps it would have helped if they had turned off the deceased skiers beacon but I am sure they thought of that.

(Avalanche researcher Ethan Greene, who investigated the slide as director of the Colorado Avalanche Information Center, said the signal issue was perplexing. He speculated that the beacons Philpott and White carried were different models and were sending signals at different rates, one quickly and one slowly, and that somehow confused the search. Greene said avalanche researchers likely will dig deeper into the "pulse rate" beacon issue that arose that day on Cameron Pass.)

I heard they both had analog beacons which can get complicated when it is a multiple situation because of overlapping pulses that searching digital beacons have a hard time seperating. See here for some light reading

www.earnyourturns.com/9331/time-to-retire-your-beacon/

So even when your analog beacon is off it is still emitting a searchable signal. Good in a recovery situation I guess. Bad in an active search if the searchers are digital and there are multipal burials.

So even when your analog beacon is off it is still emitting a searchable signal.

The Dostie article wasn't super precise about the claims. I don't think he meant that analog transceivers transmit even when they are turned off with the switch. I'm pretty sure he is saying that in between pulses (but still turned on) older analog transceivers have more residual transmitted power (since the oscillator isn't turned off, just disconnected from the antenna). This residual in-between-puleses power from an old, nearby transceiver can then compete with the (full-power-during-pulse) signal from a remote transceiver, making the remote transceiver harder to detect. I'd be interested to hear something from our experts (Jonathan S? Amar?) about how the transmit modes of avalanche transceivers have changed, and how these changes interact with the function of newer transceivers. Has anybody out there done any testing regarding the ability of different transceivers to be located? I was certainly surprised to read Dostie claim that the pulse duration and frequency of new transceivers differs from that of old ones. It seems that these should be standardized (and used by fancy transceivers to determine the number of signals in a burial)!

Regarding the Cameron Pass accident, all the accounts I have read avoid making any claims about wether or not the first victim's (Philpott's) transceiver was turned off. I assume it was transmitting until the survivor (White) was rescued and that this fact is not explicitly stated by the reporters to avoid casting all the responding parties in a bad light. I could be totally wrong about this since my info all comes via the Denver Post.

I can't investigate this fully today, and a beacon manufacturer will be more current on the present state of the standards. As near as I can tell, the relevant standard is ETSI 300718 . It's all locked up behind a copyright wall (might be free, but requires some mess of registration). Searching at etsi.org suggests that EN 300 718-1 V1.2.1 is the most current variant (May 2001). The original draft standard was ETS 300 718 ed. 1 (March 1997).

The 2001 standard (page 16) requires a beep of greater than 70 ms, and a delay between beeps of greater than 400 ms. The pulse period (between the beginnings of beeps) is required to be 1000±300 ms

The 1997 standard (page 17) requires a beep of greater than 70 ms, and a delay between beeps of greater than 200 ms. The pulse period (between the beginnings of beeps) is required to be 900±400 ms.

The relevant pdfs may be obtained from behind the copyright/pay wall by googling for en_30071801v010201p.pdf (2001 edition) and ets_300718e01p.pdf (1997 edition)

So, the standards at least changed a little from 1997 to 2001. I don't know whether there was a change in implemented best-practices from 1997 'till now.


Older folks - did older beacons have a longer duration of the beep? (like "beeeeeeeeeeeep .beeeeeeeeeeeep. ." instead of "beeeep .beeeep ")




Aside: it's interesting to see the standards discussion leading to the mandatory removal of ancillary beacon functions (altimeters, inclinometers, etc.) from the beacon standard.

So replying very briefly here (gotta finish up some work, then go ski, then pack for biz trip to ... Seattle, wuhoo!!!):

-- If you want a copy of the beacon spec pdf files, just pm me your email address.

-- A beacon that is switched to Off, is, well, off, regardless of brand. The "continuous carrier" refers to how even during the "quiet" phase a small signal is still broadcast by one particular model. So, in other words, any beacon is transmitting "BEEP [quiet] BEEP [quiet] BEEP" but that one model is kind of whispering "beep" when it really should be entirely quiet.

-- Of the two buried beacons, both were single antenna, one purely analog processing, and one digital, although the processing is of course irrelevant for transmitting. But of those two beacons, one has some signal characteristics that were quite clever at the time for optimizing being searched for by other analog beacons (including what Charlie posited), though unfortunately those same characteristics can cause problems when being searched for by current signal separation beacons. But only one buried beacon had those characteristics, and the other beacon had a extremely DISsimilar transmission pattern, which is exactly what you want for search optimization. Plus the first two searchers didn't even have signal separation beacons anyway.

-- If the proceeding paragraph didn't make much sense, well, neither does anything I've read about the botched hour-long search. (I have some additional information from a contact out there, which is partially reflected in the preceding paragraph, but he's pretty much stumped too.) Sure, wasting many precious minutes stumbling around, that's understandable. But an entire hour? They could have even gone back to where they had cell reception and watched Youtube video on how to use a beacon ... or turned off the beacon of the first beacon.

The ironical saving grace in all this is that the world's worst beacon search was offset by the world's most spectacular burial survival ... so I suppose all's well that end's well?

Thanks for your replies Jonathan and Charlie!

Jonathan: I hope your trip to Seattle included some ski time.

-- If the proceeding paragraph didn't make much sense, well, neither does anything I've read about the botched hour-long search.  (I have some additional information from a contact out there, which is partially reflected in the preceding paragraph, but he's pretty much stumped too.)  Sure, wasting many precious minutes stumbling around, that's understandable.  But an entire hour?  They could have even gone back to where they had cell reception and watched Youtube video on how to use a beacon ... or turned off the beacon of the first beacon.

The ironical saving grace in all this is that the world's worst beacon search was offset by the world's most spectacular burial survival ... so I suppose all's well that end's well?

With all due respect, lets stay classy here.  The "world's worst beacon search" was performed by a close friend.  After discussing the incident with him directly, It was his actions and decision making that ultimately resulted in the survival of the second victim. 

It easy to say what one should do from the comfort of your computer chair, dealing with this in the moment is another matter entirely.  Undoubtedly, mistakes were made regarding their search.  They needed to finish uncovering the first victim and rifle through his corpse to find the beacon and turn it off.  Easy to say hard to do.  He is very aware of this fact!!!

It is important to remember his actions resulted in the survival of the second victim.