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Authored by Scott E. Lanis 28-Aug-1998Modified by Lt Colonel Fred BlundellTX-129 Fort Worth Senior Squadron
For Local Training Rev 5.0 02-Feb-2014
OBJECTIVES
By the end of this course, you should:àKnow what an ELT is, and how it can be activatedàUnderstand why an ELT signal is an emergencyàDescribe how CAP is called out on an electronic searchàBe familiar with these fundamentals:
• Plotting a SARSAT hit on a map (latitude/longitude)• Direction finding - Little L-Per™ Operation• Triangulation• Body shielding• Aircraft coordination/LORAN/GPS operations• Ground Vehicle Operations
Is an Aircraft Missing?
How would we know?Radio distress callMonitored aircraft drops from RADAROverdue Flight PlanReport from friends/relativesELT Signal (maybe!)
How does CAP Searchfor Missing Aircraft?
Purely Visual SearchesVery Difficult: often few clues
àAir - most effective to cover groundàGround
Electronic Searches - “Quick” (24 hrs)àAir - best reception and rangeàGround - autonomous search is slower and more difficult
Advanced TechnologyFew of these resources available directly to CAP
àSynthetic Aperture Radar (SAR), Thermal/Infrared Imagery, Other Remote Sensing (satellites/reconnaissance aircraft)
What Will A CrashedAirplane Look Like?
Air to GroundCoordination
The most effective way to search The only way CAP stays in the SAR business The plan:
CAP aircraft locates crash (visual / electronic)Coordinates to bring ground team on scene
• Radio (transmit the Lat-Longs from LORAN/GPS!)• Radio Out• Lat-Long (LORAN/GPS)
Ground Team effects rescue
Aircraft Limitations
WeatherCan’t pinpoint signal
àRow of hangers
Ground Search Types for Missing Aircraft
Ramp SearchEnsure the missing aircraft has not landed safelyCan be conducted by both air and ground crews
Bastard SearchEnsure the missing person isn’t in a favorite hangout“You bastard!”
How does a search start?
There is the possibility of a missing aircraftàRadio distress call, aircraft drops from RADAR, overdue
flight plan, report from friends/relatives, ELT Signal AFRCC performs a telephone search
àAirport managers, towers, etc. Missing Aircraft Confirmed!
àAFRCC activates the appropriate CAP wing
What if only an ELTsignal is received?
AFRCC Telephone SearchAirports: “Do you hear it too?”
àLikely false alarm at this point; signal silenced by crews on airport
CAP called sooner if “after hours”àNo one else answers the phone!
Is there another indicator of a missing aircraft?If not, AFRCC will wait to see if the signal terminates
àTestsà Inadvertent actuations terminated
What is an ELT anyway?
Emergency Locator TransmitterIt’s an automatic radio beacon!
3 Frequencies of Operation121.5 MHz (VHF)AND 243 MHz (UHF)
(Military Guard)406.025 MHz (new)
Most aircraft have ELTsinstalled
General Types of ELTs
Aircraft (General Aviation) Military (“beepers” or “beacons”) Personal (PELTs or PLBs) Marine EPIRBs Advanced (406/GPS)
Typical Aircraft ELTOperation
3 Switch positions--on, arm/standby, and off G-switch activated (Generally 9G) Activates ELT upon impact when armed May be manually operated by placing the switch in in the ‘ON’
position
Can you test an ELT?
Yes, with restrictions:First 5 minutes of the hour, no more than 3 sweeps
Battery must be replaced after:One cumulative hour of use or50% of useful life has expiredFAR §91.207(c)
Does not apply to our Practice BeaconsCall nearest FSS in advance: 1 (800) WX-BRIEFGive a contact phone-interference happens on 121.775!
Inadvertent Activationof an ELT May
Occur From
Excessively hard landingInadvertent change of switch positionRemoval of the unit
à activating the switch or G-switchMalfunction
à switch shortàbattery leakage
Who is listening?
SARSAT/COSPASFAA Facilities
àFSS, Centers, TowersAirliners
àOnly if pilot choosesMilitary Aircraft
à243 MHz RequiredGeneral Aviation Aircraft
àThat’s us! Help the system work: monitor 121.5 MHzSignal report is relayed to AFRCC
How SARSAT Works
Receive 121.5, 243, 406 MHz Signals Orbiting and Geostationary Satellites
Orbiting: SARSAT/COSPAS àHigh Inclination (polar) orbits
Geostationary: GOES Weather SatellitesàSAR payloads for 406 only
Operated by Canada, France, Russia, USA They give us digital lat-long coordinates
CAP Mission Coordinator plots these and assigns assetsGround teams must interpret for land navigation
System OperationDetails
SARSAT/COSPAS in polar orbit
Calculates location of signal by measuring Doppler shift
This yields a latitude and a distance
Narrowing the Search (SARSAT/COSPAS Only)
First passàAmbiguity
Where Is It? Second Pass
à average 30-45 minute waitàAmbiguity resolvedà5-12 Nautical Mile Average Error
How do Different ELTs stack up?121.5 MHz ELT
à12 NM Radius, 452 Sq MiàAve. 6 Hour Notificationà60 Milliwatt Transmitter
406 MHz ELTà2 NM Radius, 12.5 Sq MiàAve. 1 Hour Notificationà25 Milliwatt 121.5 Beacon
406 ELT with GPSà .05 NM Radius, .008 Sq MiàAve. 5 minute Notificationà25 Milliwatt 121.5 Beacon
System Review ELT, PLB, EPIRB Signal Received AFRCC gets coordinates from SARSAT Appropriate CAP Wing is activated
False Alarms
97% of received ELTs are false alarms121.5 MHz: 1 in 1000 is an actual emergency (0.1%)406 MHz: 1 in 8 is an actual emergency (12.5%)
Why is a False Alarm a big deal?SARSAT can only monitor 10 ELTs at once (within footprint)
àbent-pipe repeaterVERY easy to overload the systemBlocks emergency communications
Blocks the real emergency!
How should wetreat an ELT?
As an EMERGENCY!You can’t know which ones are Distress ELTs
And even the false ones are good training!
Transportation to Target
Ground Teams generally will use vehicles for transportation to and from mission base
Aircraft Coordination will get the Ground Team to the target the fastest
If no aircraft is available:Vehicles provide enough speed and range to triangulateClose range may be required for signal acquisition
Direction Finding
DF unit Measures equal strengths of signal• not wholly accurate, but good enough!
Therefore, when needle is centered, ELT could be either direction
Needle always POINTS to the ELT (DF=Direct to the Flipping target)
Use a TURN to TELL if the ELT is in front or behind you
DFing with theLittle L-Per
6 Steps: use the full procedure every time!àTurn the unit to Receive, check proper frequency and volumeàTurn the Sensitivity Knob to HALF SCALE
• This will prevent oversense and a good starting pointàTurn the unit to DF (Direct to the Flipping target)àTurn at least one FULL circle, stopping and calling, “Center!”àCheck: Use Turn to Tell: the needle will point Direct to the
Flipping targetàUse your compass, shoot an azimuth to get a bearing to the
ELT
Direct to the Flipping, Turn to Tell
REC 1/2 DF Center Turn Shoot
Little L-Per Receive Mode
Measures Signal Strength onlyàFrom a direction of the arrows on the antenna (to your left)
Use it with multiple centers (more than 2) to verify strongest pathàDue ReflectionsàThat’s most likely the
true direction to the ELT
Reflections
Caused by flat surfacesHangars are notoriousRock wall, cliff, or mountains
To beat reflectionsCheck sensitivity half scale oftenUse RECeive modeRubber ducky antennaOff-frequency tuningUsually strongest DF center is not a reflection
Triangulation
Best method for ground troops to get an accurate fix when search aircraft support is unavailable
You must be able to receive the signalàCenter up DF unit on the signalàTake the magnetic bearing (shoot an azimuth)àCorrect for magnetic variation
• East is least, West is best
àPlot your bearings (draw a line) on map
àThe ELT should be where the lines cross!
Let’s See That
Body Shielding
The BEST method of beating reflections at close rangeCan use L-Per™Radio Shack JETSTREAM radio is better and CHEAP!At extremely close range, a 2m VHF radio unsquelched may work
• This works ok when trying to figure out a particular aircraft on a flight line, it willprobably not identify a particular hangar
Body blocks out the signalàCalled a NULLàNull should be at your BACK
Off-Frequency Tuning
Decrease sensitivity when:àSensitivity (L-Per™) is at the minimum and signal is still too
strong (full scale on receive) àYou don’t get a null during body shieldingàYou don’t have a sensitivity knob (Jetstream) àShortening (Jetstream) or removing (Little L-Per™) the
antenna will also decrease sensitivity Off-Frequency tuning may be used any time you have too much
signal, but this technique is especially effective during body shielding
I can’t hear the signal!ELTs are limited to Line of Sight propagationYou don’t always need to hear the ELT
àCarrier wave may be broadcasting with no audible sweepEspecially true in low batteries, or odd transmissionsYou can tell by DEFLECTIONGood needle deflection generally indicates a signal that is strong
enough to DF
What else can affect an ELT signal?
Power lines EM RadiationIf you get an actual ELT during a practice search, shut down
all practice beacons. The signal on 121.5 may be frequency shifted from your practice beacon! (often due to power lines)
Fence Line (signal can follow) Coffee Can/Stovepipe effect Hangars Moving Target
How does an aircraft perform an electronic search?
Aircraft use the same type of methods as used on the groundàDF mode (most common)àWing Null Method (body shielding with the wing!)àSignal StrengthàAural Search (rare)
Before going home,silence the signal!
Sometimes that’s the only goal! Methods of disabling an ELT:
Switch off (not always effective!)Foil tentGrounding wireRemove batteryRemove antennaThe Sheriff is required for forcible entry
àMost folks will be very cooperative Ensure the aircraft operator is notified you disabled the ELT!
Summary
You Should Now:àKnow what an ELT is and how it can be activatedàUnderstand why an ELT signal is an emergencyàDescribe how CAP is called out on an electronic searchàBe familiar with these fundamentals:
• Plotting a SARSAT hit on a map (latitude/longitude)• Direction finding - Little L-Per™ Operation• Triangulation• Body shielding• Aircraft coordination/LORAN/GPS operations• Ground Vehicle Operations
QUESTIONS?
Always Think Safety!