Classic FLARM Indicators

The following information is taken from the FLARM Operating Manual^[2] and is for the FLARM "Classic" device.  The PowerFLARM will indicate the same information in a similar fashion along with several additional screens.

The Front Panel

The front panel has a push-button, four green Status-LED, twelve bicolour LED for horizontal and four bicolour LED for vertical position indication. Depending on the threat caused by other aircraft or obstacles the LED show up red or green.  Also included is a microSD-reader.  microSD cards are not included, but widely available in electronic and mobile phone shops.

The Status Display

The green Status Display LEDs operate as follows; normal operating mode is underlined:

• Receive: Lights up when a signal is detected from another aircraft less than the configured range (default is 3 km) away, with a height separation of less than 500 m; otherwise the LED is dark. If the warning is temporarily suppressed (see below) but signals are still received from other aircraft, then the LED flashes.
• Send: Lights constantly during operation and indicates that the on-board FLARM is transmitting. Transmission requires GPS reception.
• GPS: Lights constantly during operation (with very brief interruptions once per second). If the LED is constantly dark and flashes briefly once per second, then there is no GPS reception. When switching on this condition can take several minutes.
• Power: Lights constantly during operation. If the LED flashes, then the power supply has dropped below 8 V. FLARM will not operate below 8 V DC.

The 'Receive' and 'Send' LEDs give no indication of FLARM's transceiver range.

Push Button

The push button can be used to select the following functions:

• Brief Push (<0.8 s) changes the volume from <loud> to <medium> to <quiet> to <silent> (and <loud>  again). A short sound is emitted at the new volume selected. The default setting is <loud>.
• Longer Push (2 s) changes mode between <Nearest> and <Collision> when airborne. Visual confirmation. Default setting <Nearest>.
• Longer Push (5 - 8 s, only on the ground) activates the receiver self-test: Two seconds after the button is released, FLARM will show how many other FLARM are received with reduced sensitivity (50% of the normal range). It will then emit a long beep and light one vertical LED for every 10 and a short beep and one LED of the compass rose for every single received aircraft (e.g. 14 received FLARM is:  "beeeeep bep bep bep bep", with one vertical and 4 LED's from the compass rose). After the self-test, FLARM switches back to normal operations. Note that for other units to be displayed these must be running.
• Double Push suppresses optical and acoustic warnings for five minutes. Suppression is followed by declining melody, normal setting followed by a rising melody. A double push terminates the suppressed operation at once.
• Long Push (>8 s): Re-boot. This procedure is recommended if a fault is apparent. No confirmatory sound signal.
• Very long push (>20 s) brings FLARM back to the factory settings. The very long push deletes all configurations that have been loaded by the user. No confirmatory sound signal.

Aircraft Anti-Collision Warnings

An illuminated red LED indicates the approximate bearing to an aircraft currently posing the biggest threat of collision. The bearing is relative to the track. This indication is inaccurate if there is a strong wind, if the aircraft is in a sideways yaw / slip, or if ground speed is very low (e.g. when a helicopter is in the hover). The display is refreshed every second.

The unit emits an audio warning (beep) tone at the same time as the flashing red optical warning. The time between the warning and possible collision is brief, just a few seconds. Warnings of fixed obstacles are given slightly earlier.

Horizontal indication

The twelve bicolour LED show a compass rose, i.e. the birds view on the traffic situation. 'Top' is track-up according the own aircraft. Each LED covers an equal-sized horizontal sector of 30°.  If the threat is moderate (less than 18 seconds to possible collision), a single LED lights up; in the case of a medium threat (less than 13 seconds) then two diodes light up; if the threat is imminent (less than 8 seconds) three LEDs. The threat is at the centre of the illuminated block of LEDs. The flash and beep frequency increases with the threat.

Vertical indication

The vertical bearing is indicated by a vertical line of four red LEDs and show the bearing relative to a horizontal plane. This is independent of the aircraft's climb angle. The uppermost or lowest LEDs illuminate when the bearing exceeds 14°. The LED flash frequency is identical and synchronous with that of the horizontal display.

Traffic indication (only in Nearest-mode)

In Nearest-mode the closest aircraft is shown in green as long as no warning is necessary. Traffic indications don't flash, there is no sound and the distance is not shown.

Traffic around 2 o'clock                       No flashing Traffic around 7 o'clock No flashing