EPIRB’sHow They Work

&DF-430

On the C-130H

January 2010

How the System Works

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LEOSAR & GEOSAR Satellites

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Types of Beacons

• EPIRBs

406 MHz (w/ 121.5 homer)

Automatic activation when out of bracket and wet.

Floats upright to transmit

Strobe light

Min 48 hour transmit

Some GPS enabled

Maritime Distress Beacon

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Types of Beacons

• PLBs406 MHz (w/ 121.5 homer)Manual activationCarried on persons May or may not floatHeld out of water to transmitNO Strobe light requiredMin 24 hour transmit Some GPS Enabled

Distress Beacon for Personal Use (Land Rescue)

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Types of Beacons

• ELTs

Transmit on 121.5 (most) or 406 MHz

Integrated 121.5 MHz homerCrash activation

Floats upright to transmit

No Strobe light

Min 48 hour transmit

Aviation Distress Beacon

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EPIRB

• Maritime Satellite

• Emergency

• Position-Indicating

• RadioBeacon

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EPIRB Operational Requirements• EPIRB 406 MHz Signal - 5 Watts• Short bursts at approximately 50 second

intervals (varies between 47.5 and 52.5 s), with a transmission time of 440 ms or 520 ms.

• Transmits in the 406.0 to 406.1 MHz band.• Transmission consists:

– unmodulated carrier, for 160 ms,– short synchronization signal, signal inverted for test,– Digital message that provides stored information

(identification, nationality, type of user),– Optionally, current information like, type of emergency

and estimated location.

Designed to prevent inadvertent activation

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Hex ID• EPIRB’s identification, when decoded into

its 15 character hexadecimal representation, which is the EPIRB’s unique identifier number.

• http://www.cospas-sarsat.org/Beacons/decode.htm

• Normally readout in 3 groups of 5 characters. Example: ABCDE 12345 ABCDE

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Battery Replacement• Required at Expiration date or if EPIRB

activated for any reason besides test.

• Useful Life = power for all required testing + 48 hrs operation.

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EPIRB Operational Requirements

• Positive visual and/or audible indication that EPIRB is activated (strobe light flashing).

• Easily manually deployed, activate, and deactivated, and transferred to survival craft.

• Not be activated or deactivated by conditions encountered in maritime environment.

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EPIRB Control

• Ready – EPIRB should be ON in the water unless in its bracket. Sometimes labeled “OFF”.

• ON – EPIRB operates regardless of location or orientation. Unconditional “ON” position. (Requires two physical actions)

• Test – Self-test Function.

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Prevention of Inadvertent Activation

• Must be fitted with means to prevent inadvertent activation and deactivation.

• Not automatically activate when water washes over while in bracket.

• Most EPIRBs use bracket with magnet to disable activation circuit.

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EPIRB Deactivation

• Remove beacon from water and dry off or replace in bracket

• Move switch to OFF or Ready position

• If the above failed then: – Remove cover and disconnect battery

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EPIRB Activation

• How– By definition it transmits:

• out of bracket and wet,

• by manual switch, in or out of bracket,

Or– Self test

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EPIRB Activation

• What Happens;– Beacon starts transmitting its Unique

Hex ID in a 406 MHz digital message,

– 121.5 MHz homer with an audible warble,

– Strobe Light starts flashing.

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Rockwell Collins DF-430

DF-430 Bearings

• Bearing are relative– (Heads up, not compass).

• Bearing Accuracy – less than 3°

• Bearing Stability - +/- 5° (means less needle swing, a more stable point)

• Bearing Range – continuous 360°

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Bearing Inhibit

• Bearing Inhibit – during on-board transmission, the bearing computation is frozen (DF LOCK is displayed during on-board transmissions)

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SLDMBs

• ARGOS (401.650) is the frequency for your SLDMB.

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DF Bearing Pointer

• DF pointer only updates on receipt of next 406 MHz EPIRB burst transmission.

– Will seem jerky.

• EPIRB transmission only every ~50 sec.

• Burst transmission only half sec duration.

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Figure-of-Merit (FOM) Values

• DF-430 will display a FOM value in range of 0-255.

• Practical application is as a secondary level of confidence the aircraft is tracking towards target.

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406 MHz Detection Range

Altitude (ft)Detection

Range (nm)

25,000 133

22,500 129

20,000 124

17,500 119

15,000 113

12,500 106

10,000 99

7,500 88

5,000 76

2,500 57

1,500 23

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Operational Considerations

• Transit in SAR Scan, unless tasking indicates a need to monitor a tactical freq.

• Greatest range/ earliest detection opportunity at higher altitudes.

• If a 406 signal is detected, DF needle will point.

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406 Beacon Tests• Every 406 MHz Beacon is supposed to be

tested (using the self-test function) once every month.

• Each test transmits one live 406 burst.

• Wait at least two bursts before you react to a 406 Det.

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EPIRB Prosecution

What Does the CC/RCC

do with a 406 Alert?

Registered/Unlocated 406MHZ EPIRB

• 1. RCC or RSC on receipt of unlocated registered 406 EPIRB:– a. Place case in the DISTRESS phase.– b. Assume SMC.– c. Determine status of vessel from contact

number listed, available databases, etc.

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Registered/Unlocated 406MHZ EPIRB (cont)

• 2. If vessel is determined to be safe underway or in port:– a. Close case. A case will be claimed for all

406 alerts prosecuted

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Registered/Unlocated 406MHZ EPIRB (cont)

• 3. If vessel is underway and cannot be contacted:– a. Issue UMIB for Home Port and general

area in which vessel is believed to be operating.

– b. Contact AMVER Ships and request callouts for the vessel.

– c. Contact USMCC and request satellite forecast for the geographic area.

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Registered/Unlocated 406MHZ EPIRB (cont)

• 3. If vessel is underway and cannot be contacted:– d. If the next forecast satellite pass does not

locate the beacon consider sending an SRU to the area to attempt to hail the vessel or DF on 406/121.5MHZ homing signal. Continue investigating to try to determine last known position/probable track of vessel for additional searches.

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Registered/Unlocated 406MHZ EPIRB (cont)

• 3. If vessel is underway and cannot be contacted:– e. If vessel cannot be located after reasonable

search is conducted, search will be suspended.

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Registered/Unlocated 406MHZ EPIRB (cont)

• 4. If SRU is tasked to search for vessel:– a. Proceed to LKP/tasked search area. Make

callouts for vessel and attempt to DF homing beacon on 406/121.5MHZ.

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Registered/Unlocated 406MHZ EPIRB (cont)

• 4. If SRU is tasked to search for vessel:– b. If signal cannot be DF’d once on scene and

unless otherwise tasked, aircraft shall complete a VS search at radius of 12NM. Vessels shall complete the same search at 3NM.

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“A” solution located 406MHZ EPIRB

• 1. RCC or RSC on receipt “A” solution located 406MHZ EPIRB:– a. Place case in the DISTRESS phase.– b. Assumed SMC. – c. Determine status of vessel from contact

number listed (if registered), available databases, etc.

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“A” solution located 406MHZ EPIRB (cont)

• 2. RCC or RSC if vessel is determined to be safe/underway or in port:– a. Close case.

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“A” solution located 406MHZ EPIRB (cont)

• 3. RCC or RSC if vessel is underway and cannot be contacted:– a. Issue UMIB for general area in which

vessel is believed to be operating.– b. Contact AMVER ships in vicinity and

request callouts for vessel.– c. Dispatch SRU to located vessel and

determine status. SRU’s should be tasked to DF on the signal.

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“A” solution located 406MHZ EPIRB (cont)

• 3. RCC or RSC if vessel is underway and cannot be contacted:– d. If vessel cannot be located after reasonable

search is conducted, search will be suspended.

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“A” solution located 406MHZ EPIRB (cont)

• 4. SRU if tasked to search for vessel:– a. Proceed to position/tasked search area.

Make callouts for vessel and attempt to DF homing beacon on 406/121.5MHZ.

– b. If a signal cannot be DF’d once on scene and unless otherwise tasked, aircraft shall complete a VS search at radius of 12NM. Vessels shall complete the same search at 3NM.

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“B” solution with alert probability less than or equal to 20%

1. RCC or RSC on receipt “B” solution with probability less than or equal to 20%:

a. Place case in the UNCERTAINTY phase.

b. Assume SMC.

c. Coordinate investigation with RCC responsible for “A” solution. If investigation determines “B” solution is the likely position, respond in same manner as an “A” solution.

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“B” solution with alert probability greater than 20%

• 1. RCC or RSC on receipt “B” solution with probability greater than 20%:– a. Place case in the ALERT phase.– b. Assumed SMC.– c. Coordinate investigation with RCC

responsible for “A” solution. If investigation determines “B” solution is the likely position, respond in same manner as an “A” solution.

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Unregistered/Unlocated EPIRB alerts:

• 1. RCC or RSC investigate identity of vessel through vessel data bases.

• 2. RCC or RSC contact RCC country of vessel registered and attempt to determine vessel’s status.

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False Alerts

False Alerts

• If a false alert is determined upon arrival on-scene complete the following actions:– Have vessel de-activate the beacon.– Have vessel provide the beacon “HexID”– Have vessel provide the reason beacon

alerted and include in MISLE Reporting.– Advise vessel that EPIRB and bracket require

servicing and battery replacement.– Relay to tasking authority as required.

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Operator Induced False Alerts

• 10% were Testing without following manufactures instructions, or other deliberate non-emergency activations

• 6% were EPIRBs deliberately taken out of bracket and naked of any control of the wet sensor.

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EPIRB False Alerts

69% Caused by Failure of “The bracket decoupling function” to control the EPIRB–Manufactures, makes and models

in the US registration data base were proportionally represented by False Alerts

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Why didn’t I get a 406 Detection or

How Long do False Alerts Last?

105 36 20 12 9 2 48

45.3%

60.8%69.4% 74.6% 78.4% 79.3%

100.0%

0

20

40

60

80

100

120

10 20 30 40 50 60 More

Alert Duration (in minutes)

Nu

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of

Ale

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Questions?

(305) 415 6868

Larry.T.Yarbrough@uscg.mil

L Yarbrough/D7 CFVS