121.5 ELTs banned

On Jun 22, 3:51*am, Scott wrote:
Darryl Ramm wrote:
I'd much rather have a manually activated PLB instead of an ELT -- and
personally I use a SPOT tacker in tracking mode to provide a rough
last-known position that does not rely in impact activation or being
physically able to active a PLB.

Darryl

Are these 406 units ONLY activated manually? *If so, what if a guy is
too busy flying the plane and forgets to activate the 406 unit? *If
that's the only way to set one off, the rescue rate may be less than the
121.5 units...

A 406 MHz ELT is impact activated. This requires the unit to be
properly mounted, the crash to have sufficient energy to trigger the
ELT and you also need apparently a lot of luck since correct
activation rates are pretty low (~20%?) in GA aircraft. And false
alarms (especially on older 121.5 Mhz ELTs) are high. But stats are
hard to get, and we need to be careful about comparing different
generation ELTs. I expect worse in many glider installs.

With a PLB post crash and/or landing you need to manually activate a
PLB. Trying to activate on in the air with their fold out antennas is
going to be difficult. If you can move then putting the unit flat on
the ground away form obstructions will likely produce a better signal
than many of the very bad ELT antenna installs I've seen in gliders.
Modern 406 MHz ELTs are required to be activated from a panel switch.
Older ELTs (without that switch) if they did not automatically
activate on impact may require more effort to get to and activate than
manually activating a PLB. If you cannot manually activate the PLB you
may be dead. While finding a fatal crash victim, especially with least
danger exposure to SAR personal, is important. A SPOT messenger with
tracking is a great start for that case.

There are SAR experts like Doug Ritter who keep trying to emphasize
that since ELT activation is so unreliable that a PLB is actually
better than an ELT. Carry a PLB first and maybe have an ELT as backup
for that, not the other way around.

Darryl

5Z wrote:
Just saw this in my inbox:

http://www.avweb.com/avwebflash/news..._202760-1.html


The Federal Communications Commission took the general aviation world
by surprise when it said in a recent report ...... "Were we to
permit continued marketing and use of 121.5 MHz ELTs ... it would
engender the risk that aircraft owners and operators would mistakenly
rely on those ELTs for the relay of distress alerts," the FCC says.
AOPA said today it is opposed to the rule change.


OK, maybe the satellites don't monitor the 121.5 units anymore, but
haven't commercial airliners been required to monitor 121.5 at all
times? I would think there are enough flight routes in the USA that
almost all areas would be in range of an overflying jetliner to pick up
the signal...

On Jun 22, 3:47*am, Scott wrote:
5Z wrote:
Just saw this in my inbox:

http://www.avweb.com/avwebflash/news..._202760-1.html

The Federal Communications Commission took the general aviation world
by surprise when it said in a recent report ...... "Were we to
permit continued marketing and use of 121.5 MHz ELTs ... it would
engender the risk that aircraft owners and operators would mistakenly
rely on those ELTs for the relay of distress alerts," the FCC says.
AOPA said today it is opposed to the rule change.

OK, maybe the satellites don't monitor the 121.5 units anymore, but
haven't commercial airliners been required to monitor 121.5 at all
times? *I would think there are enough flight routes in the USA that
almost all areas would be in range of an overflying jetliner to pick up
the signal...

You can Google for past discussions on r.a.s. where 121.5 MHz
monitoring has been discussed ad nauseum. Basically many airlines,
corporate flight departments, military (where equipped) and other
aircraft do guard 121.5 Mhz.

An aircraft monitoring 121.5 MHz may hear an 121.5 Mhz ELT - but if
that ELT is 121.5 MHz only it has no way to work out where the ELT is
located. You then have to launch a SAR operation to try to triangulate
that signal. We need to stop putting that silly workload on SAR
organizations and replace 121.5MHz ELTs with 406 MHz ELTs and PLBs.

Probably worth to keep reminding people that since a 406 MHZ ELT and
406 MHZ PLBs also transmit a 121.5 MHZ homing beacon if you think a
fellow pilot may be in distress you can listen for that sweep tone
sound on 121.5 Mhz. In the USA the PLB will also have a morse code
"P" (dit dah dah dit) added to the signal -- the FCC wanted that
because they thought there would be lots of false PLB activations,
that seems to have turned out not to be the case. At least that will
let you know id somebody has activated an ELT or PLB (the morse code
"P" will let you know for sure it is a PLB). Assuming the pilot is
smart and has a 406 MHZ PLB or ELT then their position has already/is
being worked out by COSPAS-SARSAT and your job is to contact the
county sheriff or similar authorities and let them know a pilot is in
distress and has activated their ELT or PLB.


Darryl

brian whatcott wrote:
Since satellite cover has been withdrawn for 121.5
(High false alert rate, poor localization)
406.0 and 406.1 ELTs will be needed, following a recent FCC determination.

Brian W

I can see the 406 units providing better localization, but how do they
lower the high false alert rate? I assume they still use a "G Switch"
to activate?

I would think that localization could be good on the 121.5 units if they
would be made to accept GPS data and transmit lat/long data when they go
off...

On Jun 22, 3:41*am, Scott wrote:
brian whatcott wrote:
Since satellite cover has been withdrawn for 121.5
(High false alert rate, poor localization)
406.0 and 406.1 ELTs will be needed, following a recent FCC determination.

Brian W

I can see the 406 units providing better localization, but how do they
lower the high false alert rate? *I assume they still use a "G Switch"
to activate?

I would think that localization could be good on the 121.5 units if they
would be made to accept GPS data and transmit lat/long data when they go
off...

The 406 MHZ ELT or PLB may not have a GPS or may not be ale to get a
GPS fix, the position of the device is then determined by doppler
triangulation from the orbiting (non-geostationary) COASPAS-SARSAT
satellites. The higher frequency and higher spectral purity specs of
the 406 MHz transmitters enable better Doppler triangulation. A
relatively accurate Doppler fix takes several passes of these
satellites. The reception of the alert and the unique ELT or PLB
digital ID is immediate (via geostationary satellites). You get all
this by throwing away the crappy old 121.5 Mhz ELTs and replacing them
with a modern device.

If a 406 MHz PLB or ELT has a GPS unit (many low-cost PLBs do now)
then it transmits its GPS position if it has a fix and that is
immediately received by the geostationary COSPAS-SARASAT satellites.

The old 121.5Mhz devices are analog, 406 Mhz has many advantages over
121.5 MHz. The solution is to throw out the old junk and move to 406
MHz. 121.5MHz PLBs belong in a landfill, and the FCC is on the right
path here.

Darryl

Scott wrote:
brian whatcott wrote:
Since satellite cover has been withdrawn for 121.5
(High false alert rate, poor localization)
406.0 and 406.1 ELTs will be needed, following a recent FCC
determination.

Brian W

I can see the 406 units providing better localization, but how do they
lower the high false alert rate? I assume they still use a "G Switch"
to activate?

I would think that localization could be good on the 121.5 units if they
would be made to accept GPS data and transmit lat/long data when they go
off...

The rationale seems to go like this: the 406 spec is for 4 watts min on
the UHF (Oh, alright = 17dBm) pulsed for nearly 1/2 second per 50 secs
or so for the following 48 to 50 hours... It emits a traceable
signature, which can quickly be associated with a particular aircraft,
so that tracing a likely route is enabled.
The 121.5 continuous signal can help with close in location.
There are apparently as many as nine G-switches built in.
They say the rescue rates on 406 alerts have been MUCH better than 121.5
alerts.

Brian W

brian whatcott wrote:

The rationale seems to go like this: the 406 spec is for 4 watts min on
the UHF (Oh, alright = 17dBm) pulsed for nearly 1/2 second per 50 secs
or so for the following 48 to 50 hours...

Brian W

Huh? +17 dBm is only 50 milliwatts???

Scott wrote:
brian whatcott wrote:

The rationale seems to go like this: the 406 spec is for 4 watts min
on the UHF (Oh, alright = 17dBm) pulsed for nearly 1/2 second per 50
secs or so for the following 48 to 50 hours...
Brian W

Huh? +17 dBm is only 50 milliwatts???

Nice catch - 17dBm is apparently the 121.5 required component.
Try 35dBm for the 406 component.

Brian W

On Jun 21, 7:01*pm, brian whatcott wrote:
Since satellite cover has been withdrawn for 121.5
(High false alert rate, poor localization)
406.0 and 406.1 ELTs will be needed, following a recent FCC determination..

Brian W

So does that mean that we'll all have to disable the 121.5 MHz output
on our 406(.1) ELTs?

Our tax dollars busily at work, again.

121.5 is still used (exclusively, unless there are recent developments
I'm unaware of) for DF equipment by CAP. Don't suppose they were
consulted.

-Evan Ludeman / T8

T8 wrote:
On Jun 21, 7:01 pm, brian whatcott wrote:
Since satellite cover has been withdrawn for 121.5
(High false alert rate, poor localization)
406.0 and 406.1 ELTs will be needed, following a recent FCC determination.

Brian W

So does that mean that we'll all have to disable the 121.5 MHz output
on our 406(.1) ELTs?

Our tax dollars busily at work, again.

121.5 is still used (exclusively, unless there are recent developments
I'm unaware of) for DF equipment by CAP. Don't suppose they were
consulted.

-Evan Ludeman / T8

It appears that the frequency mix is to be 121.5 + 406.~, but not
121.5 + 243. 121.5 df should remain useful. And CAP will get the
opportunity to rescue pilots in distress, not chase false alarms.
Just ask them about false alerts...

Brian W