406 ELT internal antenna

[GeeBee]

Did you see the whole video? When called upon to work, they failed to activate 7 out of 9 times failed to activate. Further,  only 20% of the time, did they aid in location. Now do want to you put seat belts or fire extinguishers in that category? Are you telling me seat belts only work 25% of the time?

 

[testwest]

"Satellite coverage depends on line of sight, and the satellites are rarely directly overhead. Most times, they are low on the horizon, and if your antenna has a blind spot in that direction, the satellite won't see the transmission. Signal bounce helps offset some of this, but it is not something you want to rely upon in an emergency."

Well I just had to edu-ma-cate myself further on the subject!

And actually, the Sarsat system is on multiple constellations of satellites. Originally they were on LEO satellites like the NOAA POLES system. These used frequency doppler shift to find the beacon. There are Sarsat packages on GOES-16 and 17, in geosynchronus orbit, double coverage over the U.S at all times. These see the encoded GPS information if you hooked that up to the ELT. And the latest packages on the medium orbit birds, like GPS and Galileo, can do sophisticated location using time and/or frequency direction of arrival and also see the encoded GPS information.

GREAT info here for the curious: https://www.sarsat.noaa.gov/search-and-rescue-satellites/  

And the number of fully operational Sarsat payloads is here: http://cospas-sarsat.int/en/system/space-segment-status-pro/current-space-segment-status-and-sar-payloads-pro

Of course the US is the most conservative in declaring the MEOSAR loads fully operational. 18 fully operational Sarsat packages on GPS II birds and they won't say fully operational until the latest versions are up on the IIIF sats launching in 2026. Your tax dollars at work. Meanwhile, look at the Galileo coverage!

My takeaway is that it's way more important to hook up the GPS location to the 406 ELT than to worry that an FAA certified installation method may be sub optimum for the old DF location methods that are being supplanted anyway.

Also, reading the information in the link suggests the bolded assertion, above, would be well supported only if considering the first Sarsat implementation at LEO. The Sarsat system is far more advanced now. Please don't take it personally to anyone who has a stake in this discussion....we are all trying to learn and help one another. And intellectual debate is good for the soul and the noggin!

[philiplane]

53 minutes ago, testwest said:

"Satellite coverage depends on line of sight, and the satellites are rarely directly overhead. Most times, they are low on the horizon, and if your antenna has a blind spot in that direction, the satellite won't see the transmission. Signal bounce helps offset some of this, but it is not something you want to rely upon in an emergency."

Well I just had to edu-ma-cate myself further on the subject!

And actually, the Sarsat system is on multiple constellations of satellites. Originally they were on LEO satellites like the NOAA POLES system. These used frequency doppler shift to find the beacon. There are Sarsat packages on GOES-16 and 17, in geosynchronus orbit, double coverage over the U.S at all times. These see the encoded GPS information if you hooked that up to the ELT. And the latest packages on the medium orbit birds, like GPS and Galileo, can do sophisticated location using time and/or frequency direction of arrival and also see the encoded GPS information.

GREAT info here for the curious: https://www.sarsat.noaa.gov/search-and-rescue-satellites/  

And the number of fully operational Sarsat payloads is here: http://cospas-sarsat.int/en/system/space-segment-status-pro/current-space-segment-status-and-sar-payloads-pro

Of course the US is the most conservative in declaring the MEOSAR loads fully operational. 18 fully operational Sarsat packages on GPS II birds and they won't say fully operational until the latest versions are up on the IIIF sats launching in 2026. Your tax dollars at work. Meanwhile, look at the Galileo coverage!

My takeaway is that it's way more important to hook up the GPS location to the 406 ELT than to worry that an FAA certified installation method may be sub optimum for the old DF location methods that are being supplanted anyway.

Also, reading the information in the link suggests the bolded assertion, above, would be well supported only if considering the first Sarsat implementation at LEO. The Sarsat system is far more advanced now. Please don't take it personally to anyone who has a stake in this discussion....we are all trying to learn and help one another. And intellectual debate is good for the soul and the noggin!

Even if all is perfect in the satellites, the ground based rescue crews like the Civil Air Patrol still use the 121.5 signal to get the final location. That requires a good signal from the antenna, which should be installed the way the manufacturer designed and tested it. We all thought the SAR teams would just go to the GPS coordinates last broadcast, but that is not always the case. Many 406 ELT's do not have coordinates input & broadcast.

[EricJ]

17 hours ago, GeeBee said:

Did you see the whole video? When called upon to work, they failed to activate 7 out of 9 times failed to activate. Further,  only 20% of the time, did they aid in location. Now do want to you put seat belts or fire extinguishers in that category? Are you telling me seat belts only work 25% of the time?

Yes, I saw the whole video.   I'd watched it once before when it first came out, too. 

This is where the interpretational stuff comes in.    How many of those "accidents" were low or insufficient impact to trigger it, anyway?   Somebody landing softly in a field and the airplane subsequently burning down an hour later may have been considered a "failed to activate".    This was stated in the video, that the characterizations of the ELTs or conditions were not at all detailed so that correlations were not able to be made.   And he gave no explanation for how he personally selected the subset of cases that he then calculated his "statistics" from.   His analysis was largely his own interpretations of cherry-picked data, and he basically said as much after explaining that there wasn't enough data to do more than that.

It's an interesting vid, but take his conclusions with a grain of salt.
 

[testwest]

In the paper entitled "Effect of 406 MHz ELTs and COSPAS-SARSAT Cessation of 121.5 MHz ELT Monitoring on Search and Rescue Duration for General Aviation Aircraft Accidents in the Contiguous United States", located here:

https://works.bepress.com/ryan_wallace/7/

Dr. Ryan Wallace (Embry Riddle) and Dr. Todd Hubbard (University of Oklahoma) found that in 139 missions reviewed, the mean search duration for 121.5 MHz beacons was 14.2 hours, 11.8 hours for 406 models, but only two hours for 406 beacons equipped with GPS position input. This paper was published before the MEOSAR capability was up and running. I would wager the time-to-search deltas are even greater in favor of the GPS-enabled units now.

To see how difficult it is to find a 121.5 signal due to signal factors that are not in the control of the pilot or the installation view the CAP training video here:

https://www.youtube.com/watch?v=JlB5u49FvzY

In my opinion, it is far more important to make sure the OP (and others who are considering a new installation) installs the GPS interface to the 406 ELT than it is to worry that an approved antenna installation (on a unit whose 406 output is a 5 watt burst, while now only putting out .025 watt on 121.5 instead of .1 watt like the old 121.5 ELT units) will somehow be a negative determative factor in a rescue.

Yes, there are older 406 ELT units that don't have a GPS position input. The OP is talking about a new 406 installation so the GPS input capability will be available in the unit. Yep, it is a pain to run the RS232 GPS input wires from the GPS in the panel back to the ELT unit (I did this on 201JX while the seats and left sidewall panels were out) but it's worth the effort, as evident by the citations above.

I have to thank Philiplane, EricJ and others for motivating me to learn more on this. Having done so, I am even more confident in my recommendation to the OP. Also thanks for reading through this whole thread to those who have persevered!

[bmcconnaha]

7 hours ago, testwest said:

In the paper entitled "Effect of 406 MHz ELTs and COSPAS-SARSAT Cessation of 121.5 MHz ELT Monitoring on Search and Rescue Duration for General Aviation Aircraft Accidents in the Contiguous United States", located here:

https://works.bepress.com/ryan_wallace/7/

Dr. Ryan Wallace (Embry Riddle) and Dr. Todd Hubbard (University of Oklahoma) found that in 139 missions reviewed, the mean search duration for 121.5 MHz beacons was 14.2 hours, 11.8 hours for 406 models, but only two hours for 406 beacons equipped with GPS position input. This paper was published before the MEOSAR capability was up and running. I would wager the time-to-search deltas are even greater in favor of the GPS-enabled units now.

To see how difficult it is to find a 121.5 signal due to signal factors that are not in the control of the pilot or the installation view the CAP training video here:

https://www.youtube.com/watch?v=JlB5u49FvzY

In my opinion, it is far more important to make sure the OP (and others who are considering a new installation) installs the GPS interface to the 406 ELT than it is to worry that an approved antenna installation (on a unit whose 406 output is a 5 watt burst, while now only putting out .025 watt on 121.5 instead of .1 watt like the old 121.5 ELT units) will somehow be a negative determative factor in a rescue.

Yes, there are older 406 ELT units that don't have a GPS position input. The OP is talking about a new 406 installation so the GPS input capability will be available in the unit. Yep, it is a pain to run the RS232 GPS input wires from the GPS in the panel back to the ELT unit (I did this on 201JX while the seats and left sidewall panels were out) but it's worth the effort, as evident by the citations above.

I have to thank Philiplane, EricJ and others for motivating me to learn more on this. Having done so, I am even more confident in my recommendation to the OP. Also thanks for reading through this whole thread to those who have persevered!

thanks for the info, i PMd you back.