In article ,
Gezellig wrote:
On Thu, 09 Jul 2009 17:44:28 -0500, Jim Logajan wrote:

http://www.ntsb.gov/ntsb/brief.asp?e...07X17184&key=1

How long after first impact should it take for the ELT to kick out a
call on frequency?

If the ELT isn't destroyed in the crash, it usually doesn't go off until
the wreckage is hauled away.

406 ELTs are slightly better then 121.5 ELTs in terms of false
positives (ELT goes off with no crash), but in real crashes, they
both have extremely high failure rates.

I don't have access to the stats any more, but when I was in CAP,
something like 98% of ELT searches where false activations, and
ELTs failed to activate in about 95% of all crashes. Numbers are
from memory, so might be off by a bit, but the magnitude of the issue
should be obvious.

Being on flight following and/or getting off a Mayday before crashing
greatly increase your chances of being found. Manually triggering
your ELT before impact might help, if it survives the impact.

John
--
John Clear - http://www.clear-prop.org/