Hi Ed,
Comments interspersed below.
WRB
--
On Aug 18, 2010, at 22:05, Ed Burkhead wrote:
Bill,
A directional signal to the satellites is not needed. The
omnidirectional signal put out by the ELT is sufficient as it is
direct line-of-site to all satellites above the horizon (unless you
are below the cliff face or down in the deep valley or already down
under the forest trees).
Understood. Didn't I read somewhere that satellites has ceased to
monitor the old-style ELT frequency?
A 406 MHz ELT is pre-registered as being installed in a specific
airplane. When the ELT is triggered by the cockpit panel switch it
immediately (no wait) starts putting out an emergency signal with a
unique ID code. That signal and unique ID is picked up by all the
SARSAT satellites above the horizon. With only the basic squawk, it
may take up to 1-3 hours to determine the fix to locate you within a
quarter to 1-3 miles or so but they will immediately know who you are
and what type of aircraft right down to the paint (as recorded on your
registration form).
If the ELT contains a GPS chip AND keeps working long enough for the
GPS chip to receive signals, initialize and determine its location,
then the outgoing signal begins to contain a report of the exact GPS
location accurate to within a hundred yards or so - this may take from
a minute or two up to 10 or so minutes before the fix is determined
and starts to be included in the report.
(Note: if you have your ELT connected to an always-on GPS, the ELT can
transmit the GPS signal with it's first squirt. One I'm looking at on
my other screen even accepts the NEMA 0183 data format that my old
GARMIN GPSMAP60 (and most older GPS units) can output. My old GPS is
WAAS enabled and has accuracy down to 8-20 feet!
As it is an ELT registered to an aircraft, the action starts at once.
They can check the FAA database to see if you are on a filed flight
plan - if so, no more delay is needed. If there's no flight plan
filed, they may call your home, airport and (maybe) cell phone to see
if they can contact you. But, if you have the hookup to a GPS, they
have an instant pretty good fix and an emergency call. It's not a
many hour delay like there was for the old-style ELTs. For all I
know, they may be sending police (and an ambulance?) to your location
within five minutes.
Did not know all this...thanks!
The current switch in the cockpit does activate the ELT and starts
sending out the help call.
Yeah, it comes back to me now...it made the "on the hour" (activation
verification) test easier when on the control panel.
I'd like a very big red button I could slap while anything is going
on.
While endorsing that idea I was speculating further to have it initiate
a sequence built into future Transponders and Com Radios. Each has a
different, independent antenna...just the idea that three sources of
MAYDAY might be worthwhile redundancy given the inconsequential cost in
volume of the additional chip and wire in such future devices. The
"Aux Audio" freebie saved a few intercom purchases way back when.
The SPOT system mentioned by Perry also has value (even though it
does not satisfy the ELT requirement for airplanes). It can be set to
auto report its location every so many minutes (I think 5) and that
location is recorded with the SPOT company. If you don't close your
flight plan, they have a trace to the last 7-10 miles of your
location. If you didn't file a flight plan and your friends or
relatives note that you didn't come home or arrive at your
destination, that record can show approximately where you went down.
If you manage to activate the SPOT emergency call, their system can
immediately start the emergency process, sending out help to your
location.
I'd kind of like to have a SPOT along with a 406 MHz ELT. Or, being
poor, I would like to have at least an old-style ELT (the minimum
required by law) and a PLB (Personal Locater Beacon) (even though the
PLB must be hand triggered and has no impact activator). The PLB
could have most of the immediate location finding effectiveness of the
406 MHz ELT - especially if you list it on your flight plan and
especially if you have a GPS enabled PLB.
http://en.wikipedia.org/wiki/Distress_radiobeacon#How_they_work
Me too!
Ed
