why 406 beacons are bad

[Spaceman3750]

It's my understand that the 121.5 tone from a 406 is very weak and useless to any ground team beyond 1/2 mile.

Is this correct?

Correct; however, an aircrew should be able to put you within a reasonable distance from the target, if not right on top of it.

[lordmonar]

It's my understand that the 121.5 tone from a 406 is very weak and useless to any ground team beyond 1/2 mile.

Is this correct?

The 406 beacon gets you to withing 3KM....and then you use 121.5 to DF it to a find.

[Buzz]

Back when dinosaurs ruled the Earth, and I was a CAP cadet, the FAA came out with these fancy new radios they called "ELTs."  They were supposed to help us find downed aircraft within minutes, by screaming for help on the radio frequency which had been reserved for emergency use since the 1930s.

There was a minor problem, though -- the FAA-approved, super-flexible antennas had the annoying tendency to snap off in any impact where the ELT would be of any use.  This was eventually corrected.

Fast-forward 40 years, and now we have the 406MHz EPIRB.  This is an advanced system, which is supposed to help us find downed aircraft within minutes, by screaming for help on a radio frequency intended for monitoring by satellites.

The pros of the new system are that, when it works, it provides a faster and more accurate general fix.

The cons are that this frequency is used by many users (not just aviation), and it requires a special receiver, rarely found in aircraft, control towers, etc.  The low-power signal on 121.5 is all but worthless in most places that a plane will go down due to such factors as terrain, antenna orientation, etc -- and the antennas are tuned for 406, not 121.5. 

This means that the only people who can know that it's operating are those who either buy the special equipment, or have the frequency plugged into their scanner radios.  No more "casual" finds, where some pilot has 121.5 plugged into the B channel of his radio as he flies across the desert.  No more homing across the miles by a GT with an air-band handheld and a fox-hunt Yagi antenna.  No more multi-station fixes.  Worse, the weak signals on 121.5 will make the plane-in-a-hangar search harder, as the 406 signal punches through to the satellite but just rattles around at the airport. 

We can overcome most of these problems by changing techniques, but one problem which we CAN'T work out is that a battery running two transmitters will go dead long before that same battery if it only runs one, and as it weakens, the "homing signal" on 121.5 will go from being poor to being completely useless, in a matter of hours (at best).

One other issue is due to the vast number of users of the frequency.  Anyone who remembers their first CB walkie-talkie at Christmas will remember the joy of trying to pull your buddy's signal out from among the thousands of others on Channel 11.  Imagine the thrill of hunting for an actual missing plane or person, and discovering that the EPIRB in some nearby fisherman's tackle box has activated, is radiating into the boat's sunshade support, and has the strongest signal for miles around.  Or, worse, let's say we're looking for a plane and there are SEVERAL signals, from fishing boats, hikers' packs, kidfinders, etc, all on the same frequency.  Having a separate frequency for aviation ELTs has let us avoid this problem.

Losing 121.5 will cost us a lot of effort, a lot of money for new equipment, and possibly even cost lives.

[Buzz]

The 406 beacon gets you to withing 3KM

Yeah, it says so right on the label.

[Ed Bos]

It's my understand that the 121.5 tone from a 406 is very weak and useless to any ground team beyond 1/2 mile.

Is this correct?

Correct; however, an aircrew should be able to put you within a reasonable distance from the target, if not right on top of it.

Not to mention, that even without integrated GPS, the 406 style beacons and new SARSAT appear to get us much tighter to the actual coordinates than the old 121.5 SARSAT.  Because teams seem to be starting much closer, the lower power of the 121.5 digital tone is far from the end of the world.

And for more delicious troll food... ... The USCG can DF several 406-range beacon frequencies. There's some ok reading on this capability at http://www.sarsat.noaa.gov/BMW%2008%20attachments/USCG%20406%20Df%20presentation%202008%20BMW.pdf

[lordmonar]

I just love the nay sayers.

The frequencies might get too busy because everyone and his brother will have a a beacon of some type!.......really? 
If......IF that ever happened.....then just look at how useful CAP will be!  We will have plenty of buisness and no one would want to get rid of us!

True....it is harder to DF on 121.5.

But the probablity area is smaller and you get notified within minutes of an activation instead of hours.

Add GPS.....which I thing should be required!.....and if everything goes as plan.....SAR is going right to your location no DFing or searching required.

And once again all together for the people who did not get the memo........if you are relying on 121.5......well unless someone is monitoring it or you are close to an ATC facility.....no one is going to hear you....hope you filed a filght plan.

[EMT-83]

And do you really think that ATC is listening?

We came across an ELT signal while flying in the vicinity of a towered field last year, and reported it to ATC. Their response? "Okay, we'll turn on the radio and see if we can hear anything." Very reassuring.

[blackrain]

It's my understand that the 121.5 tone from a 406 is very weak and useless to any ground team beyond 1/2 mile.

Is this correct?

Correct; however, an aircrew should be able to put you within a reasonable distance from the target, if not right on top of it.

Not to mention, that even without integrated GPS, the 406 style beacons and new SARSAT appear to get us much tighter to the actual coordinates than the old 121.5 SARSAT.  Because teams seem to be starting much closer, the lower power of the 121.5 digital tone is far from the end of the world.

And for more delicious troll food... ... The USCG can DF several 406-range beacon frequencies. There's some ok reading on this capability at http://www.sarsat.noaa.gov/BMW%2008%20attachments/USCG%20406%20Df%20presentation%202008%20BMW.pdf

I saw one interesting statement from the report you linked. "90 percent of EPIRB SAR cases are within 20 NM of shoreline." Anyone know if that still holds true?

[SARDOC]

And do you really think that ATC is listening?

I know in my area I haven't heard ATC reporting 121.5.  They Frequently relay the message from airliners flying over.  it's really surprising how many that do get reported.

[Larry Mangum]

Back when dinosaurs ruled the Earth, and I was a CAP cadet, the FAA came out with these fancy new radios they called "ELTs."  They were supposed to help us find downed aircraft within minutes, by screaming for help on the radio frequency which had been reserved for emergency use since the 1930s.

There was a minor problem, though -- the FAA-approved, super-flexible antennas had the annoying tendency to snap off in any impact where the ELT would be of any use.  This was eventually corrected.

Fast-forward 40 years, and now we have the 406MHz EPIRB.  This is an advanced system, which is supposed to help us find downed aircraft within minutes, by screaming for help on a radio frequency intended for monitoring by satellites.

The pros of the new system are that, when it works, it provides a faster and more accurate general fix.

The cons are that this frequency is used by many users (not just aviation), and it requires a special receiver, rarely found in aircraft, control towers, etc.  The low-power signal on 121.5 is all but worthless in most places that a plane will go down due to such factors as terrain, antenna orientation, etc -- and the antennas are tuned for 406, not 121.5. 

This means that the only people who can know that it's operating are those who either buy the special equipment, or have the frequency plugged into their scanner radios.  No more "casual" finds, where some pilot has 121.5 plugged into the B channel of his radio as he flies across the desert.  No more homing across the miles by a GT with an air-band handheld and a fox-hunt Yagi antenna.  No more multi-station fixes.  Worse, the weak signals on 121.5 will make the plane-in-a-hangar search harder, as the 406 signal punches through to the satellite but just rattles around at the airport. 

We can overcome most of these problems by changing techniques, but one problem which we CAN'T work out is that a battery running two transmitters will go dead long before that same battery if it only runs one, and as it weakens, the "homing signal" on 121.5 will go from being poor to being completely useless, in a matter of hours (at best).

One other issue is due to the vast number of users of the frequency.  Anyone who remembers their first CB walkie-talkie at Christmas will remember the joy of trying to pull your buddy's signal out from among the thousands of others on Channel 11.  Imagine the thrill of hunting for an actual missing plane or person, and discovering that the EPIRB in some nearby fisherman's tackle box has activated, is radiating into the boat's sunshade support, and has the strongest signal for miles around.  Or, worse, let's say we're looking for a plane and there are SEVERAL signals, from fishing boats, hikers' packs, kidfinders, etc, all on the same frequency.  Having a separate frequency for aviation ELTs has let us avoid this problem.

Losing 121.5 will cost us a lot of effort, a lot of money for new equipment, and possibly even cost lives.

And anyone who has chased 121.5 beacons, when multiple ones are going off, also knows they mask each other, so your point about the vast numbers of users on the 406 frequency is being a new issue, is just not valid, especially since 406 beacons transmit in bursts and not continously as 121.5 beacons did.  And sicne teh 406 beacon gets you nominally with 3 km of the target it is much easier to get a read off of the 121.5 homing signal among the clutter then it is with 121.5 only beacons.

[lordmonar]

And do you really think that ATC is listening?

We came across an ELT signal while flying in the vicinity of a towered field last year, and reported it to ATC. Their response? "Okay, we'll turn on the radio and see if we can hear anything." Very reassuring.

I know my last two ELT searches were started because ATC heard the tone over their radios. (one was 121.5 and the other was 436).

So yes they are listening.....but that's okay for about 10 miles or so.  Beyond that....good luck.

[bosshawk]

Here is an interesting situation for some of you guys to chew on.  On Saturday, I replaced the battery in my 121.5 ELT, tested it with my handheld radio and closed up the airplane.  I apparently forgot to set the switch to ARM and left it on ON.  From Sat at about 1530 until Monday around 1000, not a soul heard the signal.  Somebody finally heard it Monday AM and reported it to the airport attendent(I am on a non-towered airport and the nearest tower is roughly 50 miles away).  The airport attendent, a pilot, had no idea as to whom to report it.  He knew of my CAP background and called me(I was 80 miles away).  I suggested that he take a handheld and go to my hangar, since it struck me that I might have had a brain F----.   He called back and said, yep and the local mechanic turned it off.

Now, I suspect that the battery might have finally died had everyone waited for someone else to do something about it.  The local sheriff said "OK" and hung up, as they have no DF capability.  An airway goes directly over our airport and there are several others within radio range.  The attendent did call the FAA FSDO and got a guy who was checking the weather and he said, "everybody is off today, its a holiday".  That ended the FAA participation.

I suspect that a lot of 121.5 signals get ignored just like this, with nobody monitoring them.

[Ed Bos]

The attendent did call the FAA FSDO and got a guy who was checking the weather and he said, "everybody is off today, its a holiday".  That ended the FAA participation.

That should be criminal.

[Buzz]

And anyone who has chased 121.5 beacons, when multiple ones are going off, also knows they mask each other, so your point about the vast numbers of users on the 406 frequency is being a new issue, is just not valid, especially since 406 beacons transmit in bursts and not continously as 121.5 beacons did.

While you are correct, consider that when you have multiple 121.5 signals, they all have to be found and killed anyhow.  When you have multiple 406 signals, same story, but when there were, say, 5 ELTs going off after a heavy storm or an earthquake, you will have 5 THOUSAND EPIRBS going off in the same conditions.

Consider also that the only people on 121.5 are aviation-related, while EPIRBS on 406 are being sold to a far greater number of potential users, most of whom won't have the same kind of understanding of what they are and what they are for.

Think about the ELT-in-a-flight-bag searches you've been on.  These are ALL for pilots, trained in communications and who understand the "the whole ELT thing" -- and the still forget to disarm the things when they take them out of the plane.  Now compare that to the average EPIRB purchaser.  These are generally NOT people with any technical understanding.  They buy them because they are told of all the wonderful things that an EPIRB can do for them, then handle them carelessly.  I've seen them clipped to the daypacks of kids walking to school, on the dashboards of pickup trucks, and I watched a guy at a gun show trip 10 of them, trying to find the one that had the audible tone -- while the salesman watched, made suggestions and NEVER TURNED THEM OFF (when I came around the tables and started shutting them off, they both wondered why I even cared).  As was pointed out by a different poster, this will provide job security for CAP!

The problem is that the person in REAL NEED has to compete with all of the false signals, as well as the other shortcomings.

The thing that I have against the 406 units is simply that the same advanced technology could have been added to 121.5, for less money, and still kept us away from those millions of other users.  We have been taken out of our own, special lane on the highway and shoved into rush hour with everyone else, for the convenience of government bureaucrats who have no understanding of SAR needs and capabilities.

[Buzz]

I know my last two ELT searches were started because ATC heard the tone over their radios. (one was 121.5 and the other was 436).

So yes they are listening.....but that's okay for about 10 miles or so.  Beyond that....good luck.
[/quote]

A few years ago, before SARSAT, an airline pilot went missing in his Cessna.  The word went out on company channels to every airliner in the state, who all listened on 121.5.  By the time we got to the airport, we already were getting reports of the ELT signal.  It took longer for a crew to fly to the search area than it took them to find the plane once they got there.

There's a lot to say for having beacons on a frequency that requires no special equipment to monitor.

There's a lot to say AGAINST removing a capability which saves lives, even when you think you have something better, especially when there is no valid reason to do so, much less an actual NEED to make the change.

[lordmonar]

I know my last two ELT searches were started because ATC heard the tone over their radios. (one was 121.5 and the other was 436).

So yes they are listening.....but that's okay for about 10 miles or so.  Beyond that....good luck.

A few years ago, before SARSAT, an airline pilot went missing in his Cessna.  The word went out on company channels to every airliner in the state, who all listened on 121.5.  By the time we got to the airport, we already were getting reports of the ELT signal.  It took longer for a crew to fly to the search area than it took them to find the plane once they got there.

There's a lot to say for having beacons on a frequency that requires no special equipment to monitor.

There's a lot to say AGAINST removing a capability which saves lives, even when you think you have something better, especially when there is no valid reason to do so, much less an actual NEED to make the change.

The 406's still signal on 121.5.....that has not changed.....the only difference is the power out up and how far you can receive it.

If a 406 equiped plane has gone now.....and the ELT is workign properly.....you would not have to do an "all call" sort of search.  The satellite will pick it up before the individual is even missing.  SARSAT will check the registration against any filed flight plans and will know right away if this is a real SAR or not (assuming a flight plan was filed).  If no flight plan....SARSAT makes a few phone calls if they can't get a hold of the registered owner they send it up to AFRCC as a SAR....with inital coordinates within 3Km.....all of this happens quicker then when the 121.5 was tracked by satellite.

[PHall]

Slightly Off Topic, but how many of you pilots out there monitor 121.5 when you fly?

[bosshawk]

me, on my #2 com

[peter rabbit]

our unit - using the Becker on the Aux input.

[PHall]

Now, how many "civilian" pilots do it? You would think organizations like the AOPA would be all over this.
"Monitor 121.5, you may save a life!"

I would say that this would be perfect for CAP PAO's to get out to the public. But I've seen the way many CAP PAO's go about their jobs...