Questions to Yellow-hatters re 406 MHz beacons

[Vasco Sodcat]

Seeking a little education, please:

1. As we now need 406 MHz beacons to automatically "hit" the Sarsats, are the RAF, Navy and Coastguard SAR fleets getting equipped with homers compatible with 406 beacons?

2. Am I correct in assuming these fleets will continue to be able to home onto the 243/121.5 beacons that still populate many LSJ's?

[Ali Barber]

Also, what happens if you go down with a 406 fitted and the operating area doesn;t have that in their SAR system?

[Critical_Al]

406 Beacons also contain a 121.5 beacon for SAR asset homing. The 406 beacon is picked up by satellite, and a position passed to the ground station. The SAR helicopter etc will then conduct the final homing to the reported position using the 121.5 signal. To the best of my knowledge ( current up until earlier this year) there is no current plan to upgrade all SAR assets to home to 406 MHz.

The 406 beacon satellite coverage is almost worldwide so unless you are 'really' lost it should pick you up. The areas without coverage are shown on several websites but unless you are planning on a trip to some really remote parts of the Southern Ocean you should be fine.

The Wikipedia entry for '406 Beacon' will tell you more than you ever wanted to know, should you be interested.

[Al-Berr]

Crit_Al,

I don't think you can get more current than "earlier this year"!!!! ;)

[EWD-STAB]

Not yellow hatter, but am able to shed some light:

1. Current CG helo's have the ablity to DF on 406mhz, as you know the various mks of Seaking can not. However this isn't the end of the world, as all 406mhz beacons also transmit a 121.5mhz homing signal. Thus enabling all SAR a/c to home on the 121.5 signal. I understand all/most USCG SAR a/c can home on 406mhz and trial gave a vastly improved range compared to 121.5. I assume (dangerously) that the incoming SAR-H a/c will also be able to home on 406mhz.

Somewhere I have read about GPS encoded beacons being able to transmit their L+L to SAR units directly on 406mhz. But cant remember the details. Will dig out and post.

2. As stated above the inbuilt 121.5 signal continues to be fitted to 406mhz beacons. So yes SAR units will continue to have this facility.

Ali - Not entirely sure what you mean... But I take it your worried about the 406mhz beacon being detected in the first place. COSPAS/SARSAT will now ONLY detect 406mhz signals, which will be relayed to the appropriate MCC for that Search and Rescue Region. If no reliable authority in the area of the alert then chances are the state registering the beacon will investigate, or pass the alert to a responsible neigbouring SAR authority.

If you meant homing on the 406mhz beacon, then hopefully my 1st two answers will shed some light on the matter.

Cheers

EWD

[EWD-STAB]

Just chased down that ref:

I was wrong about current CG a/c being able to DF 406mhz - memory playing tricks on me.

However both the S92 and AW139 can read the embedded lat and long of suitably equipped beacons.

EWD

[Sven Sixtoo]

The key to this is understanding the signal that a "406" beacon puts out.

It has two components:

The 406 MHz signal, which carries a unique ID (so if the database is correct the RCC knows where the beacon came from and can check where it should be) and a data message that can include a GPS position, is transmitted at 5 watts power for 0.5 seconds every 50 seconds. There is a small randomisation on that 50 seconds so that 2 beacons don't transmit on top of each other forever. Most beacons (including the ones being acquired for the British Military under the PELS programme) do have a GPS. Because of the structure of the digital message, there is a limt of about 4 seconds of arc on the position that can be transmitted. This is nothing to do with GPS accuracy - there just isn't enough space in the message (the structure of which is internationally agreed) to transmit digits to get you better accuracy. The accuracy achievable is a box about 120 metres x 70 metres at UK latitudes.

The other signal is a near-continuous swept-tone 121.5 MHz analogue at about 125 mW. This can be picked up by homing equipment in the exact same way as it has been done for many years.

Some beacons (including PELS) also transmit the swept tone on 243 MHz.

To find someone wearing one of these beacons, the primary method is to get the GPS position and go there. If at that point it's dark and foggy, you carry out an old-fashined homing on 121.5 / 243. You can get the GPS position either via the satellite network (the UK terminal is co-located with the Rescue Co-ordination Centre at Kinloss) or by receiving and decoding the 406 signal directly.

Most modern homing systems (eg the Chelton 7 fitted to the RAF Griffin 2s and the Chelton 9 fitted to the CG SAR 92s and 139s) can home on 406, as well as decoding the digital information. However, 406 homing, although very useful for long-range work because of the power of the signal and the fact that there shouldn't be anything except emergency beacons on that frequency, and quite useful for multiple beacon situations because of the short duration and long gaps in transmission, is very little use for establishing an on-top, because you can be 2 miles through the overhead (well one-and-a-bit in a Sea King) before the next pulse that tells you the beacon is behind you.

So, in theory, the fact that existing military SAR aircraft (Griffin 2 excepted) cannot home to or decode the 406 signal, doesn't affect their capability, provided the situation isn't too complicated and everything else in the beacon / satellite package works as advertised.

Sven

[sox6]

Homing did not work to plan here:-
http://www.aaib.gov.uk/cms_resources.cfm?file=/S3-2009%20G-REDU.pdf
http://www.aaib.gov.uk/cms_resources.cfm?file=/S4-2009%20G-REDU.pdf
Oil & Gas UK E-Newsletter (http://www.oilandgasuk.co.uk/issues/HTG_update_31_October.html)
Room to improve?

[Dave Angel]

The MRA4 can DF 406 Beacons as well as the legacy distress frequencies.:ok:

[Vasco Sodcat]

Thank you all for your most illuminating replies :ok:

Critical Al:

"...unless you are planning on a trip to some really remote parts of the Southern Ocean you should be fine"

You have hit one of the nails smack upon the head! :}

[EWD-STAB]

Unless I am very wrong indeed, a 406mhz beacon will work anywhere in the world. If you look up GMDSS the sea areas are divided into areas for distress alerting purposes. A 406Mhz is the gold standard, and will work anywhere. Alert times may be slightly longer due to the less frequent coverage by the LEOSAR sattelites, and the gaps in GEOSAR coverage. Nontheless 406mhz will be detected worldwide.

Potential confusion from the Imarsat service, which I believe is unreliable below approx 70 degrees South. I know the Australian and NZ SAR authorities reguarly deal with detects from well South of 70.

EWD

[Spanish Waltzer]

The title of this thread got me thinking. Where does the painting of flying helmets yellow stem from? I believed it was so that it was easier to spot the crewman on the ground if he was detached from the wire for any reason. However that does not explain why pilots have yellow helmets also.

Do any other SAR operators do the same thing or is it purely a RAF thing?

I'm sure the answer is out there somewhere....crab??

[Jerry Can]

It is so the rearcrew can be seen when we are on the ground. Most of our pilots are green hatters.

JC (RAF Winchman)

[TorqueOfTheDevil]

Most of our pilots are green hatters


Indeed so. There are some who have cajoled/bribed the Squippers to paint their helmets yellow, to jump on the rearcrew's bandwagon, and perhaps also to be an alternative splash of colour, following the ban on the apricot flying suits which were procured some years back for SARBoys but never issued...

[switch_on_lofty]

I recently attended a survival equipment brief and asked about PELS. The answer given was that it was delayed (same as for the last few years) which was not encouraging.

I have also discovered that the RAF SAR Force have purchased 406 PLBs for their crews seperately to the PELS programme. As someone who operates significantly further from rescue services than the yellow-jobs, I have a keen interest in potential self-preservation!

Does anyone have an update on PELS? Thanks.

[getsometimein]

The legacy maritime patrol fleet had also purchased an off-the-shelf 406 while it waited for PELS to be capable enough to stay in service for more than a week...

[NST]

Did my last tour as an MCC operator, albeit ten years ago so I am a bit out of the loop, but dont forget the Geostationary satellites. If a 406 goes off in their footprint then an alert is instantly generated and sent to the relevant MCC. In the case of a UK beacon that would be Kinloss. Obviously with no movement like their low earth orbiting brothers no resolved position can be obtained but Falmouth hold the UK maritime beacon register and the aviation one for 406 beacons was "under construction" when I left. As each beacon has its own unique 15 Hex ID its just a case of checking the database and making sure whatever it is attached to is safe. When a 406 low earth orbiting sat alert appears it is either relayed to the MCC of the country of registration or if its a UK beacon, traced by Kinloss or Falmouth depending on whether its AVIation or MARitime. I remember getting just a Geo alert on beacons in store at Bristows or Scotia at Aberdeen Airport which alerted us and when the orbiting sat hit came through we could identify the individual warehouse it was situated in to assist in shutting it down. The Geosat that provided UK area coverage back then was Goes 8 parked 35,000 km above Brazil to give you some idea of the visibility window it has. Obviously UK beacons picked up by other MCC's with a UK register will be relayed by the relevant MCC and the same tracing action provided.

For remote areas there always used to be two sats I think in "global dump" mode for "over the pole" coverage. They would download as they passed the nearest available LUT ground terminal and the data then distributed. Not perfect as I can remember beacons alerts that were hours old coming through due to the time taken to go over the hump .. but better than nothing.

I work on the rigs now as a Radio Operator and all our 406's have 121.5 homers. I have worked fixed rigs where the 406 has the GPS position embedded into it. The likes of the Brent Bravo for instance aren't going anywhere, and have been rooted to one spot for nearly forty years so it makes sense. But I work mobile rigs which obviously makes that a non starter. We never know where we will be in a month !!

PS .. We miss you Nimrod guys, and we appreciate you helo guys. Me more than most in both categories.

[RODF3]

The MRA4 can DF 406 Beacons as well as the legacy distress frequencies

Surely that's 'would have been able to' rather than 'can'.

[Stitchbitch]

Lofty, you might want to speak to your SE, who should be more than willing to fill you in on the reoccuring PELs saga..:zzz:

[Walrus75]

I'd have Svens babies... whilst keeping one foot on the floor obviously!

[2port]

Vasco

Where are you heading to then, or have you already gone?

2P

[Sven Sixtoo]

Quote
I'd have Svens babies... whilst keeping one foot on the floor obviously!
Unquote

Not while I have breath in my body you won't. I've been too close to the odd walrus or two.

7.62

is the solution to a lot of problems.