1. This course is designed to give a basic introduction to how electronic searches for downed aircraft are conducted. It includes use of the L-Tronics “Little L-Per™,” triangulation, body shielding, and activation of CAP. This course is mainly focused on the ground team member aspect of electronic search.
Authored by Scott E. Lanis 28-Aug-1998
Modified by Lt Colonel Fred Blundell
TX-129 Fort Worth Senior Squadron
For Local Training Rev Feb-2014

2. OBJECTIVES By the end of this course, you should:
Know what an ELT is, and how it can be activated
Understand why an ELT signal is an emergency
Describe how CAP is called out on an electronic search
Be 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

3. Is an Aircraft Missing? How would we know? Radio distress call
Monitored aircraft drops from RADAR
Overdue Flight Plan
Report from friends/relatives
ELT Signal (maybe!)

4. How does CAP Search for Missing Aircraft?
Purely Visual Searches
Very Difficult: often few clues
Air - most effective to cover ground
Ground
Electronic Searches - “Quick” (24 hrs)
Air - best reception and range
Ground - autonomous search is slower and more difficult
Advanced Technology
Few of these resources available directly to CAP
Synthetic Aperture Radar (SAR), Thermal/Infrared Imagery, Other Remote Sensing (satellites/reconnaissance aircraft)
A purely visual search is often a nearly impossible task when the range and speed of a missing aircraft is considered.
An airborne search covers the most ground per period of time.
Ground searches by themselves are ineffective. (not including ramp and bastard searches)
This “cutting edge” technology was heavily utilized in Colorado’s search for Craig Buttons’ A-10.

5. What Will A Crashed Airplane Look Like?
Your second most likely place to find a Bonanza. JOKE! I love Bonanzas.
An aircraft like this is likely to have survivors-and they’ve likely already gone home and left the ELT operating! (I’ve seen this twice)

6. Air to Ground Coordination
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

7. Aircraft Limitations
Weather
Can’t pinpoint signal
Row of hangers

8. Ground Search Types for Missing Aircraft
Ramp Search
Ensure the missing aircraft has not landed safely
Can be conducted by both air and ground crews
Bastard Search
Ensure the missing person isn’t in a favorite hangout
“You bastard!”

9. How does a search start?
There is the possibility of a missing aircraft
Radio distress call, aircraft drops from RADAR, overdue flight plan, report from friends/relatives, ELT Signal
AFRCC performs a telephone search
Airport managers, towers, etc.
Missing Aircraft Confirmed!
AFRCC activates the appropriate CAP wing
AFRCC will try to resolve the ELT
AFRCC will call airport managers to see if they receive a signal that seems to be near an airfield
if a signal is received on the field, the manager will responsibly disable the ELT
If no airports are in the vicinity, a CAP search is initiated after a set period of time has passed
If the signal coincides with an overdue aircraft or unclosed flight plan, search begins faster
CAP often is called out “after hours” when there are no airport managers left at work!
CAP answers the call because everyone else has gone home.

10. What if only an ELT signal is received?
AFRCC Telephone Search
Airports: “Do you hear it too?”
Likely false alarm at this point; signal silenced by crews on airport
CAP called sooner if “after hours”
No one else answers the phone!
Is there another indicator of a missing aircraft?
If not, AFRCC will wait to see if the signal terminates
Tests
Inadvertent actuations terminated

11. What is an ELT anyway? Emergency Locator Transmitter
It’s an automatic radio beacon!
3 Frequencies of Operation
121.5 MHz (VHF)
AND 243 MHz (UHF) (Military Guard)
MHz (new)
Most aircraft have ELTs installed

12. General Types of ELTs Aircraft (General Aviation)
Military (“beepers” or “beacons”)
Personal (PELTs or PLBs)
Marine EPIRBs
Advanced (406/GPS)

13. Typical Aircraft ELT Operation
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

14. 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 or
50% of useful life has expired
FAR §91.207(c)
Does not apply to our Practice Beacons
Call nearest FSS in advance: 1 (800) WX-BRIEF
Give a contact phone-interference happens on !

15. Inadvertent Activation of an ELT May Occur From
Excessively hard landing
Inadvertent change of switch position
Removal of the unit
activating the switch or G-switch
Malfunction
switch short
battery leakage

16. Who is listening? SARSAT/COSPAS FAA Facilities FSS, Centers, Towers
Airliners
Only if pilot chooses
Military Aircraft
243 MHz Required
General Aviation Aircraft
That’s us! Help the system work: monitor MHz
Signal report is relayed to AFRCC

18. How SARSAT Works Receive 121.5, 243, 406 MHz Signals
Orbiting and Geostationary Satellites
Orbiting: SARSAT/COSPAS
High Inclination (polar) orbits
Geostationary: GOES Weather Satellites
SAR payloads for 406 only
Operated by Canada, France, Russia, USA
They give us digital lat-long coordinates
CAP Mission Coordinator plots these and assigns assets
Ground teams must interpret for land navigation

19. System Operation Details
SARSAT/COSPAS in polar orbit
Calculates location of signal by measuring Doppler shift
This yields a latitude and a distance

20. Narrowing the Search (SARSAT/COSPAS Only)
First pass
Ambiguity

21. Where Is It? Second Pass average 30-45 minute wait Ambiguity resolved
5-12 Nautical Mile Average Error

22. How do Different ELTs stack up?
121.5 MHz ELT
12 NM Radius, 452 Sq Mi
Ave. 6 Hour Notification
60 Milliwatt Transmitter
406 MHz ELT
2 NM Radius, 12.5 Sq Mi
Ave. 1 Hour Notification
25 Milliwatt Beacon
406 ELT with GPS
.05 NM Radius, .008 Sq Mi
Ave. 5 minute Notification
Diagram and information adapted from NOAA Pamphlet, with the exception of 25 milliwatt beacon.
Note that hunting ELTs by signal alone will become much more difficult with less than 1/2 the power (inverse square law says less than 1/4 the effective radius from previous ELTs) but hopefully uncommon
Food for thought: how common will the GPS portion of an ELT fail with the beacon operating?? That’s anyone’s guess.

23. System Review ELT, PLB, EPIRB Signal Received
AFRCC gets coordinates from SARSAT
Appropriate CAP Wing is activated

24. False Alarms 97% of received ELTs are false alarms
121.5 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)
bent-pipe repeater
VERY easy to overload the system
Blocks emergency communications
Blocks the real emergency!

25. How should we treat an ELT?
As an EMERGENCY!
You can’t know which ones are Distress ELTs
And even the false ones are good training!

26. 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 triangulate
Close range may be required for signal acquisition

27. 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

28. DFing with the Little L-Per
6 Steps: use the full procedure every time!
Turn the unit to Receive, check proper frequency and volume
Turn the Sensitivity Knob to HALF SCALE
This will prevent oversense and a good starting point
Turn the unit to DF (Direct to the Flipping target)
Turn at least one FULL circle, stopping and calling, “Center!”
Check: Use Turn to Tell: the needle will point Direct to the Flipping target
Use your compass, shoot an azimuth to get a bearing to the ELT

29. Direct to the Flipping, Turn to Tell

30. REC
1/2 DF
Center
Turn
Shoot

31. Little L-Per Receive Mode
Measures Signal Strength only
From a direction of the arrows on the antenna (to your left)
Use it with multiple centers (more than 2) to verify strongest path
Due Reflections
That’s most likely the true direction to the ELT

32. Reflections Caused by flat surfaces Hangars are notorious
Rock wall, cliff, or mountains
To beat reflections
Check sensitivity half scale often
Use RECeive mode
Rubber ducky antenna
Off-frequency tuning
Usually strongest DF center is not a reflection

33. Triangulation
Best method for ground troops to get an accurate fix when search aircraft support is unavailable
You must be able to receive the signal
Center up DF unit on the signal
Take the magnetic bearing (shoot an azimuth)
Correct for magnetic variation
East is least, West is best
Plot your bearings (draw a line) on map
The ELT should be where the lines cross!

34. Let’s See That

35. Body Shielding The BEST method of beating reflections at close range
Can 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 will probably not identify a particular hangar
Body blocks out the signal
Called a NULL
Null should be at your BACK

36. Off-Frequency Tuning Decrease sensitivity when:
Sensitivity (L-Per™) is at the minimum and signal is still too strong (full scale on receive)
You don’t get a null during body shielding
You don’t have a sensitivity knob (Jetstream)
Shortening (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

37. I can’t hear the signal! ELTs are limited to Line of Sight propagation
You don’t always need to hear the ELT
Carrier wave may be broadcasting with no audible sweep
Especially true in low batteries, or odd transmissions
You can tell by DEFLECTION
Good needle deflection generally indicates a signal that is strong enough to DF

38. What else can affect an ELT signal?
Power lines
EM Radiation
If you get an actual ELT during a practice search, shut down all practice beacons. The signal on 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

39. How does an aircraft perform an electronic search?
Aircraft use the same type of methods as used on the ground
DF mode (most common)
Wing Null Method (body shielding with the wing!)
Signal Strength
Aural Search (rare)

40. Before going home, silence the signal!
Sometimes that’s the only goal!
Methods of disabling an ELT:
Switch off (not always effective!)
Foil tent
Grounding wire
Remove battery
Remove antenna
The Sheriff is required for forcible entry
Most folks will be very cooperative
Ensure the aircraft operator is notified you disabled the ELT!

41. Summary You Should Now:
Know what an ELT is and how it can be activated
Understand why an ELT signal is an emergency
Describe how CAP is called out on an electronic search
Be 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

42. QUESTIONS?
Always Think Safety!