ELT DF Search Simulator
This ELT Search Simulator emulates the function of an ELT Direction Finder (DF), similar to the L-Tronics L-Per. An ELT direction finder is used to locate the site of plane crash or accidental activation of an operational Emergency Locator Transmitter (ELT). The ELT Search Simulation Software lets you to "fly" around a hypothetical map looking for the source of a hidden ELT using a simulated ELT DF instrument display. The objective is to fly your aircraft as close as possible to the ELT. If you get close enough, the ELT is shown and you get a search score. The shorter distance you fly to find the ELT, the lower the score, just like golf. If you can't find it, just click the Reveal ELT checkbox and it will show the hidden ELT's location.
Sample Display
In this snapshot, the ELT has been revealed at the end of a search. You can see the red
search aircraft just below it. The concentric circles indicate the actual location of the ELT. The instruments along the right side show the heading of the aircraft, how far it has traveled in nautical miles (nm). The ELT/Signal Strength Meter shows the direction of the signal. In this case the red DF needle is to the left indicating the ELT is to the left of the aircraft as can be seen on the map. The VOR/DME has a functional VOR indicator with Distance Measuring Equipment (DME) indicator. Although not needed for the search, it was added as an additional instructional item.
Aircraft: The current aircraft heading is display with North up on the map. Move the aircraft with the Forward, Left, and Right buttons. The Left/Right buttons change the heading 30 degrees. Change the distance traveled with the Cruise (about 1 nm) and Slow Flight (about 1/3rd nm) buttons.
ELT DF/Signal Strength Meter This is the main instrument you will use to find the ELT. The red light in the upper right corner indicates that you are close enough for the ELT signal to be received. This light is out (black) when you are not in reception range. You may have to fly around the map until you start to receive a signal. The red line pointer in the meter operates in two modes: DF (Direction Finding) and Signal Strength.
DF Mode: This is the direction finding mode of the DF Unit. When the ELT signal is strong enough (you are close to the ELT), the pointer will deflect in the direction of the ELT. The blue line indicates the center of the meter. As you move, the pointer will shift left or right as the position of the ELT varies relative to the direction of your aircraft. As the signal strength increases (getting closer to the ELT), the pointer will deflect farther to one side or the other. Needle deflection is alway with respect to the aircraft direction.
Signal Strength Mode: In this mode the pointer indicates only the strength of the signal. The stronger the signal the greater the deflection to the right and the closer you are to the ELT. The full left position indicates no ELT signal.
Reveal: If you can't find the ELT, click the Reveal checkbox.
ELT Operation and Use
An Emergency Locator Transmitter (ELT) is required on practically all aircraft in the U.S. These battery powered electronic signaling devices transmit a sweep tone on a frequency of 121.5 MHz and/or 243.0 MHz. The ELT is impact-activated in the event of a crash. Search and Rescue (SAR) aircraft or ground teams use direction finding equipment like this simulator to find the downed aircraft emitting the ELT signal. ELTs are usually activated by accident due to rough landings, battery corrosion, and mishandling. More than 90% of all searches are false alarms of this type. A properly operating ELT will be capable of operating for 24 to 48 hours. The Civil Air Patrol conducts the majority of ELT searches in the U.S. under the direction of the United States Air Force Rescue Coordination Center. Newer ELTs operate on 406 MHz by transmitting a digital signal giving its GPS coordinates and an identification code. These also contain a low power 121.5 MHz signal to assist with location within a few miles.
Many times, locating an ELT is a coordinated effort between air and ground teams. Whether searching on an airport or off, ground crews use ELT DF equipment to guide them to the target.
Shown at the left, two members of the Civil Air Patrol use a hand held ELT DF unit
to locate a "hidden" ELT training transmitter (shown above, black box with antenna) at the airport during a training exercise.
Want to hear an ELT? Click here for the sound of an ELT {wav file}. Yes, that can be very annoying while trying to find one these.
Click this link for the
ELT DF Search Simulator
Other Links
Curator: Bruce Bream {tarrow@roadrunner.com}
Last Update: 13-Sep-2020