FLARM F6 series User manual

®
OPERATING MANUAL
FLARM COLLISION WARNING UNIT
Status
Software version 4.06 (March 28, 2009)
This manual only covers hardware version 3 resp.
units with serial numbers F6•••• / F7•••• / F8••••.
For legacy units with serial numbers F4•••• / F5••••
Please also consult the legacy manual as well.
This is a translation of the German manual.
© 2003-2009 FLARM Technology GmbH
Hausen am Albis-Switzerland
www.flarm.com
[email protected]om

OPERATING MANUAL FLARM COLLISION WARNING UNIT
Version 4.06E Page 2 of 12 March 28, 2009
1. Welcome to the FLARM user community
Thank you for purchasing FLARM, a modern low-cost collision-warning unit for sailplanes and light aircraft.
The main task for FLARM is to support the pilot, while he scans the airspace ahead with his own eyes.
FLARM is simple to use and does not distract the pilot from the main business in hand.
Sport flying is an activity that is associated with considerable risks for crew, passengers, third parties and
other objects. In order to make full and safe use of FLARM, it is absolutely essential to be fully aware
of the risks, operating conditions, restrictions and limitations associated with the use of FLARM,
ensure a proper installation and do regular software updates. This includes familiarity with and
observance of this Operating Manual and the Installation Manual. Additional configuration information
can be found in the ‘Data Port Specifications' document, e.g. how to suppress additional data at the serial
port what might be required in international championships.
We welcome user feedback and reports, suggestions for improvements, and pictures that will help us make
further improvements to FLARM. Feedback reports should give a detailed description of the situation,
quoting the hardware and software versions used, plus the flight data records in IGC format with short time
recording intervals.
The latest version of this handbook and other related documents can be found at the Website
www.flarm.com. This Website also has answers to Frequently Asked Questions.
This Website also carries announcements when new software versions or functions become available. If you
enter your name on the mailing list, you will automatically receive notification of changes as and when they
happen: https://lists.flarm.com/mailman/listinfo/user-list_flarm.com
To use existing devices in April 2008 or later, it is required to update the software to version 4.00 or higher.
Use the free PC installation software available at www.flarm.com. You need a PC with Windows 98 / ME /
2000 / XP with a serial port or a suited USB-serial converter plus a data-power cable like the one used for
most IGC flight recorders. This cable connects the PC to FLARM and supplies FLARM with power. Ensure
you have configured the correct PC COM-port, only use the Power/Data-port on FLARM (not the Extension-
port) and know the printed device serial number. After completion of the software update, use the same PC
software to load the most recent obstacle file to FLARM; this file is available on www.flarm.com as well. Then
use the PC software to configure the flight recording functionality accordingly. In case of questions, contact
your FLARM dealer.
Software-versions 4.x will only remain operational until March 01, 2011. Before this date, you must update
the device in order to use it in the air. The update is available in October 2010.
2. How it works
FLARM receives position and movement information from an internal 16 channel GPS receiver with an
external antenna. A pressure sensor further enhances the accuracy of position measurements. The
predicted flight path is calculated by FLARM and the information - including a unique identifier - transmitted
by radio as low-power digital burst signals at one-second intervals. Provided they are within receiving range,
the signals are almost at the same time received by further aircraft also equipped with FLARM. The incoming
signal is compared with the flight path predicted by calculation for the second aircraft. At the same time,
FLARM compares the predicted flight path with known data on obstacles, including electric power lines, radio
masts and cable cars.
If FLARM determines the risk of dangerous proximity to one or more aircraft or obstacles, the unit gives the
pilot warning of the greatest danger at that moment. The warning is given by a whistle sound (beep) and
bright light emitting diodes (LED). The display also gives indication of the threat level, plus the horizontal and
vertical bearing to the threat. During circling flight different methods of calculation are employed to those
used during straight flight.
The GPS and collision information received from other aircraft can also be made available for third party
equipment (e.g. external display, speech synthesizer, PDA) via a serial data output. Such equipment is
available from a number of manufacturers.

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The operating range is very dependent upon the antenna installation in the aircraft. The normal range is
about 2 km. In individual cases the range may be up to 5 km, which can be valuable for fast sailplanes with a
speed of up to 250 kt, providing the pilots in both aircraft with a warning enabling visual identification and
reaction to the potential hazard. The effective range can easily be verified with an online tool
1
. Warnings are
given in order of the time remaining before a potential collision, not the geometrical distance. The first
warning level for another aircraft or an obstacle is delivered when less than 18 seconds remain to the
possible collision; the second warning level is delivered when less than 13 seconds remains; the third level
when less than 8 seconds remains.
The warnings continue as long as FLARM calculates a threat of collision. The warning level may decline or
be cancelled, depending upon the prediction. The warnings are selective; they are only issued if the
calculation reveals a high probability of collision in the near future. The alarm sensitivity can be configured
with the PC.
In addition, FLARM operates as an IGC-file compatible flight recorder including the G-record. Flight logs can
be read out either via the SD-card or via the data port and a suitable cable. The SD card does not need to be
carried on during the flight. FLARM is optionally also available as diamond-level IGC-approved Flight
Recorder, optionally with Engine Noise Level sensor (ENL).
With the standard Jan 2009 obstacle databank there is memory for more than 100 hrs of flight recording at a
2s interval. Use the free PC-software to download flights to your PC and to properly configure your device for
flight recording. Flight recording automatically starts when the aircraft is moving and ends when the unit is
switched off. Switching off the device during the flight for a longer period results in separate flight record files.
Allow at least 1 minute (if the interval is 2s, our recommended value) after landing before you switch off the
device else you loose the last part of the flight. Allow more time after landing if the interval is higher. When
the memory is full, the oldest data is overwritten. Always download you flight data before you update the
obstacle databank or the software.
FLARM applies for the radio communication between the units a proprietary and copyright-protected protocol
in regionally different frequency bands. The radio communication is separately secured against unauthorized
access. The design is protected by several patents. The radio communication protocol is not public, but
FLARM Technology GmbH offers a license contract where it is accessible in the form of a compatible core
design ready for integration into 3
rd
party systems. These systems are officially declared as FLARM-
compatible. Any non-licensed use, dissemination, copying, implementation, reverse engineering or
decompilation of the FLARM radio communication protocol, the FLARM hardware and software or parts of it
is forbidden by law and will be prosecuted. FLARM is an internationally registered trademark and can not be
used without license. Technical specifications subject to change at any time without notice.
3. General Advice on Operation
This Manual must be carried on board the aircraft. When permanently installed in an aircraft, the 'AFM
Supplement' must also be carried in the aircraft.
In flight the pilot must have direct sight of and immediate access to a switch or circuit breaker that
disconnects FLARM from the aircraft electrical power supply, without affecting other essential aircraft
systems. This might be necessary if the pilot suspects that FLARM may be interfering with another on-board
system, the suspected presence of smoke, the smell of smoke, or flying in a country where the use of
FLARM is not permitted.
FLARM must not be operated at night or with night vision systems.
FLARM will not operate without adequate GPS signal strength. Correct antenna installation has a great
effect on the transmission/receiving range; an incomplete or improper installation can make correct
operations impossible without the system being able to detect this.
FLARM is not able to measure its own RF-receiver sensitivity. When the pilot detects that other aircraft are
received only when very close or not at all and when the RF-antenna’s positioning is clearly not the cause of
it, the device must be checked by the manufacturer.
1
www.flarm.com/support/analyze

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Installation and operation must be on the basis of non-interference with and no hazard to the existing suite of
other certified equipment necessary for safe flying operation, or installed to comply with official requirements.
Installation and operation must comply with official regulations and requirements. It is recommended that the
FLARM, GPS and radio antennae are all installed as far away as practicable - but at least 25 cm from -
susceptible aircraft systems such as GPS antennae and the magnetic compass.
The unit must be protected from solid particles or liquids, should not be exposed in use to temperatures
below –10°C or above +60 °C , or stored at temperatures –20°C or above +70 °C, because this may cause
irreparable damage. On the ground, the unit should be protected from exposure to long periods of direct
sunlight, because it is likely to be overheated. Also avoid static discharges to the radio antenna.
Details on correct installation are found in the Installation Manual. Ensure that you have configured the
correct aircraft type with the PC-software. Ensure that tug planes are configured as such!
4. Operating Modes
FLARM operates in two modes, Nearest and Collision. The change from one mode to the other is effected by
a two-second push on a button followed by a brief visual confirmation from the unit. After the change has
been signalled, the current mode selected is not displayed. When switched on, the unit is in Nearest mode.
The warnings given are identical in both modes, and generally relate to an immediate threat to which the
pilot should make an immediate and appropriate reaction. The assumption has been made that following a
warning it will take up to 12.5 seconds from the time that the other aircraft is seen, until a change in flight
path has removed the threat
2
.
When operating in the Nearest mode, the unit also reports the presence of other aircraft operating in the
vicinity, even though calculations indicate that they do not represent a threat. The information displayed is
limited to a configurable radius (default is three kilometres) and a vertical separation of 500 m. When no
aircraft was displayed so far but one is received now, this is signalled with a click-sound. Only one single
aircraft is indicated in green. The optical signal is static (no flashing); the threat intensity is not indicated and
there is no sound warning. As soon as FLARM detects the risk of a collision it automatically switches to
Collision mode, followed by automatic reversion to Nearest. The choice of mode is presented, such that
immediately after pressing the key, the display presents a diverging pattern .
When operating in the Warning mode a red LED lights up only if the calculation predicts a threat. Warnings
are always shown by flashing LEDs, the threat level being shown by the number of LEDs illuminated, by the
frequency of flashes, and the simultaneous sound signal (beep). Selection of this mode is indicated by a
upwards converging pattern immediately after pressing the selector key.
In both modes the pilot can suppress the display and the acoustic warning: after a double push FLARM
will suppress all visual and acoustic signals relating to traffic, obstacles or other threats. The act of selecting
suppression is followed by a descending tone. A further double-push reinstates the Collision mode at once
and is followed by a rising tone. While warnings are suppressed, FLARM nevertheless continues to transmit
signals for reception by other aircraft.
2These times were published in 1983 FAA Advisory Circular 90-48-C and were based on military data. They relate to fast jet pilots with
no on-board warning systems for other traffic and hazards. The assumption was made that only one aircraft takes avoiding action. Of
the 12.5 seconds, five seconds were to recognise the threat of collision and four seconds were required to decide upon avoiding action.
No information is available as to whether these times are applicable to light aircraft, sailplanes or helicopters, when using a warning
system.

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5. 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.
Push-button 4 green LED
(Status)
12 LED (horizontal)
4 LED (vertical)
all bicolor
microSD
reader
6. Use the microSD card
microSD cards are smaller than SD cards or miniSD
cards, but mechanical adapters exist to insert a microSD
card in a SD or miniSD cards; these adapters are often
provided with the cards.
Ensure that the microSD card is formatted to FAT /
FAT16, not FAT32. Cards with more than 2 GB memory
need to be reformatted to FAT / FAT16. Cards with less
memory are often preformatted in FAT / FAT16. Small
cards with 32 MB are sufficient for more than 100 flights.
microSD
(used in FLARM)
miniSD
(not used)
SD
(not used)
Insertion and removal
Carefully insert the card upside-down (metal contacts
on top), push with the finger until the card locks with a
click sound. To remove, push the card with the finger
into FLARM until it releases with a click sound, then
carefully pull it out. No force should be required to
insert or remove the card.
Updating the firmware
Download flight records before updating the firmware, otherwise data might be lost. Firmware files for
microSD card updates have the extension .fw and are available on the FLARM webpage
(www.flarm.com/support/updates/index_en.html). Copy the file to the top level directory, don’t use sub-
directories. Don’t modify filenames. Delete files with the same extension. To start an update, insert the card
into FLARM and interrupt power for at least 5 seconds. The update then takes about 50 seconds. The card
may remain in the device after updating and during operation.
Updating the obstacle database
Download flight records before updating the obstacle database, otherwise data will be lost. Obstacle
database files for use with microSD and PC software have the extension .obs and are available on the
FLARM webpage (www.flarm.com/support/updates/index_en.html). Copy the file to the top level directory,
don’t use sub-directories. Don’t modify filenames. Delete files with the same extension. To start an update,
insert the card into FLARM and interrupt power for at least 5 seconds. The update then takes several
minutes, depending on the size of the file; progress is shown on the display. The card may remain in the
device after updating and during operation.

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Configuring the device
If at power up on the microSD card a file named flarmcfg.txt is detected, it will be processed as
configuration commands. The syntax is the same as on the serial data port (see ‘FLARM Data Port
Specifications’ manual), except for PFLAC,,ID. This feature is especially useful for batch configuration or a
pilot’s individual configuration for shared aircraft.
For easy task declaration, use the free online-tool FlarmCfg (http://www.segelflug-software.de/flarmcfg/ ,
using the microSD card), the corresponding offline-version (http://www.segelflug-
software.de/prod_flarmcfgtool.php), the free PDA software tools SeeYou ConnectMe
(http://www.naviter.si/products/connectme.php) or pocket*StrePla-Connect
(http://www.strepla.de/StrePla4/english/pS_connect/), and many of the other, partially commercial products
on the market. Note that task declaration only works on IGC-enabled units.
Basic data entries and the SD-card configuration file can be made with the free FlarmTool software
(http://www.flarm.com/support/updates/).
7. Start-Up
FLARM is always switched on if the unit is connected to an adequate power supply.
Immediately after it has been switched on there follows a one-second long beep while a start-up pattern
might be shown on the LED, followed by a binary presentation of the hardware-version installed during the
system self-test. The self-test mode lasts from two to 20 seconds, depending upon the size of the obstacle
data bank. The April 2008 data bank takes about twelve seconds.
0x03
Hardware Version 3 (only green)
•This is followed by another one-second beep, followed by a brief binary presentation of the software-
version: The first six LEDs clockwise represent the minor version in red, the other LEDs clockwise the
major version in green.
If the software version is not indicated and the beep sound is not emitted, the unit is not ready for operation.
-
Software version 3.xx (operational only to March 2008)
0x100
Software version 4.00 (operational till March 01, 2011)
0x101
Software version 4.01 (operational till March 01, 2011)
-
Software version 5.xx
(available in October 2010, mandatory on March 02, 2011)
Then FLARM shifts to normal operation and waits until it has acquired an adequate GPS position fix. When
switching on, this procedure can take several minutes. Without a proper GPS position fix, the unit is not
ready for operation. Before departure the pilot must ensure that at least the Power-, GPS- and Send-
LED are all continuously on. This state must be preserved during the whole flight to ensure correct
operation.

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8. Fault Finding
If a fault should occur during start-up self-test or subsequent operation, then all four green status LEDs will
flash in unison for 30 seconds, while the red collision LEDs will give a binary indication of the most serious
fault. The fault display can be stopped before 30 seconds has elapsed by pushing the button.
For safety reasons FLARM will not start up if there is a fault. FLARM may not be used if a fault has been
reported or indicated. Limited operation is possible if there is an indication of a problem with the obstacle
data bank or data recorder.
0x11
Fault: Software out of date
(needs GPS reception) No operation
0x12
Fault: Software integrity violation No operation
0x21
Fault: Low Voltage No operation
0x31
Fault: Internal GPS communication No operation
0x32
Fault: Faulty GPS configuration No operation
0x41
Fault: Internal radio communication No operation
0x51
Fault: General internal communication No operation
0x61
Fault: Flash memory No operation
0x71
Fault: Pressure sensor No operation
0xF1
Fault: Other fault No operation
0x81
Indication: No obstacle data bank Operation possible
0x91
Indication: Flight recording not possible Operation possible
0xA1
Indication: Error with SD-card configuration file Operation possible
The communications faults itemised above indicate if internal modules within FLARM are not communicating
correctly with each other. For reasons associated with the system, reduced radio range cannot be detected
by a single unit alone.

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Software-versions 4.x will only operate until March 01, 2011. Before this date, you must update the device in
order to use it in the air. An update with the same functionality can be downloaded free of charge, and will be
available in October 2010. Users will be able to load the software with the aid of a suitable power supply/data
cable (not supplied). This operation requires the user to have the unit’s serial number to hand. Software
validity has to be time-limited to ensure that all FLARM units are mutually compatible and that updates
include the latest obstacle data.
9. 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.
10. 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.

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11. 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. The flash and beep frequency
increases with the threat.
Moderate threat from ca. 3 o'clock
(less than 18 seconds to calculated collision)
Slow flash at 2Hz
Moderate threat from 1 to 2 o'clock
(less than 18 seconds)
Slow flash at 2Hz
Medium threat from 1 o'clock
(less than 13 seconds)
Medium flash at 4Hz
Immediate threat from 1 to 2 o'clock
(less than 8 seconds)
Rapid flash at 6Hz
Medium threat from the rear, 5 to 7 o'clock
Medium flash at 4Hz
Moderate threat from the rear right, 4 to 5 o'clock
Slow flash at 2Hz
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

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12. Obstacle Warnings
The standard obstacle data bank (as of Jan 2009) has about 33,000 coordinates locating about
11,000 Alpine obstacles
3
. This data bank is loaded by FLARM at manufacture; subsequently the user may
upload but not alter up-dated information via a PC. Special data banks, corrections and amendments can be
reported to us.
The FLARM display flashes when there is warning of obstacles. The warning always relates to obstacles
straight in-line with the current flight heading. In other words there is no horizontal or vertical bearing given to
the obstacle. The threat level depends upon the time remaining to impact; the flash and beep frequency
increases with reducing distance from the obstacle. The display is refreshed every second.
A warning is given if an aircraft flies under a cable or power line.
An acoustic warning (beep) is given at the same time as the flashing fixed obstacle warning. The time
between warning and possible collision is brief, just a few seconds. However, warnings are given of fixed
obstacles earlier than those for other aircraft.
Obstacles are indicated as follows:
A toggling pair of two LED’s is shown, with the toggle frequency
depending on the threat.

3For details on the data sources and status, consult the ‚Obstacle Data Format Specifications’ manual.
Neither FLARM Technology nor these organisations accept any responsibility for the accuracy, completeness or up-to-date
status of the data or any direct or indirect damage resulting from using such data. Official data sources only collect data
which have been reported by those who own, construct or operate constructions which represent an obstacle, and do not
check these reports.

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13. Operating Limitations
FLARM is designed and built as a non-essential 'situation awareness only' unit to only support the pilot, and
cannot always provide reliable warnings. In particular, FLARM does not give any guidance on avoiding
action. Under no circumstances should a pilot or crewmember adopt different tactics or deviate from the
normal principles of safe airmanship. Even with FLARM installed, you remain responsible for flying the
aircraft and ensure the safety of passengers and other traffic. The use of FLARM is solely at the discretion of
the commander and his delegated crew member. Operation must be preceded by thorough familiarisation by
the commander or his delegated crew member with the Operating Manual.
FLARM will only give warnings of other aircraft that are likewise equipped with a compatible unit. FLARM
does not communicate with Mode A/C/S transponders and is not detected by ACAS/TCAS/TPAS or Air
Traffic Control. Likewise FLARM does not communicate with FIS-B, TIS-B or ADS-B.
Compatible FLARM units must be within range in order to provide a warning. The range is very much
determined by the type, installation and position of the radio antennae, plus the relative positions of the two
aircraft. Under optimum conditions the internal antennae can give a head-on range of up to 5 km; normally,
range is about 2 km, which is adequate for light aircraft and sailplanes. The radio signals can only be
received by line of sight. There is no FLARM signal between two aircraft on opposite sides of the same
mountain.
FLARM has to know its current position in order to operate. For this reason, FLARM will only operate in the
presence of good quality three-dimensional GPS reception. GPS reception is greatly influenced by the
installation and position of the antenna, and aircraft attitude; furthermore, it requires that the US-American
GPS-system is fully operational. This is particularly true during turns, when flying close to mountain slopes
and in areas known for poor reception. If the installation is poor the GPS signal quality may be reduced. In
particular, there can be rapid degradation of height calculations. FLARM resumes operation as soon as the
GPS reception quality is adequate.
Movements calculated by the GPS relate to a fixed system of terrestrial coordinates. In strong wind there
may be a substantial difference between aircraft heading and track, leading to a distortion of the threat
bearing. If the wind speed is one third of True Airspeed (TAS) and the yaw-free aircraft Heading is 90°out of
wind, then the threat indication displayed has an error of about 18°. If the wind is very strong, the Track can
deviate up to 180°from Heading. Under such circumstances and when circling, the calculation and warnings
given are unusable.
When close up, when two aircraft are at the same or similar height, or GPS reception is poor, the vertical
bearing indication is imprecise and fluctuates.
FLARM calculates the predicted flight path of the aircraft to which it is fitted for less than the next 20
seconds. This prediction is based on immediate past data, current position- and movement data, plus a
movement prediction model that is optimised for the respective user. This forecast is associated with a
number of uncertainties that increase with an extension of the forecast time. There is no guarantee that an
aircraft will actually follow the predicted flight path. For this reason, the warning issued will not be accurate in
all cases. In sport flying flight path predictions of more than 30 seconds are unusable. This is particularly true
for sailplanes and hang gliders. For this reason, the radio range is generally adequate.
Warnings are given at very short notice, i.e. the warning is given within a time frame of from a few seconds to
18 seconds, depending upon the closest predicted proximity, as calculated. The threat intensity (pitch of the
warning tone, LED block width, flash interval) flags up the threat (collision time point), but not the geometric
distance. FLARM only issues a warning if the calculation forecasts a considerable threat. For this reason, it is
usual - depending upon the mode selected - that no warning is given about the presence of other aircraft, in
spite of the fact that signals have been correctly received.
When a number of moving threats or fixed objects are within range, then FLARM gives warning only of the
most dangerous in accordance with the threat calculation algorithm. The pilot is unable to confirm receipt of
this warning, nor is he able to call for presentation of further threats. In spite of the warning issued for one
other aircraft or fixed objects, it is quite possible that there are several further aircraft or fixed objects that
represent a greater threat than that which has been signalled. When the unit simultaneously detects a threat
from moving and fixed obstacles, then the warning issued relates to the earliest likely collision.

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FLARM indicates the rough position of the aircraft or obstacle that currently represents the biggest threat, in
accordance with the algorithmic calculation. In the case of fixed obstacles, the unit does not signal a bearing.
FLARM does not indicate where the closest proximity may occur, nor does it signal avoiding action. Whether
and how avoiding action is taken is solely a matter for the pilot, who must base his decision on his own
observation of the airspace. In taking his decision, he must comply with the Rules of The Air and ensure that
no additional hazard is caused by his action. Depending upon the phase of the flight, FLARM uses different
forecasting methods, movement models and warning calculations, to provide the pilot with the best possible
support without causing a distraction. For example, when a sailplane is circling, the system sensitivity is
reduced. These models and processes are optimised, but are nevertheless a compromise. As seen by the
pilot these models are the source of 'false alarms'; i.e. FLARM would give warnings of 'threats' that would not
subjectively be regarded as a real danger. It is quite possible that FLARM will not give warning of the highest
threat, or will give any warning at all.
Obstacle warnings (e.g. cables, antenna masts, cable cars, avalanche dynamite wires, power lines) are
dependent on the information having been stored correctly in the internal data bank. The unit cannot give
warning of any fixed object that has either been incorrectly stored, or not stored at all. No data bank is
complete, up-to-date and correct. Obstacle information stored has usually been simplified; for example,
FLARM assumes that a power wire is slung absolutely straight between two fixed points with no sag.
Likewise, data for power lines and cable cars does not include all intermediate masts. In addition, FLARM
data does not include terrain data and no such warnings are possible.
FLARM radio communications take place in a license-free band in which there is general freedom to transmit
and receive. This means that the band is also available to a number of other uncoordinated users. FLARM
has no exclusive right to the use of this band and there is no guarantee that FLARM will not be subject to
interference by third parties.
There are national differences in frequency allocation and operating conditions between countries. The
aircraft commander and user are solely responsible for ensuring that their use of FLARM conforms with local
regulations. No radio licence is required for FLARM in Switzerland, Germany and France.
The radio transmission protocol employed places no limit on the number of units that may be operated within
a given range. However, an increasing number of units within range is associated with a reduction in the
probability that a single coded signal will be received ('graceful degradation'). The probability is small that
subsequent signals will not be received from the same transmitter. FLARM is designed to receive and
process signals from up to 50 aircraft within range. A high number of FLARM units within range has no effect
on range.
The transmitter has no effect on what the receiver in the other aircraft does with the data. It is possible that
this data may be captured and stored by other aircraft, or by ground stations, or used for other purposes.
This opens up a range of possibilities, some of which may be in the pilot's own interest, (e.g. automated
generation of an sailplane launch logging system, aircraft tracking, last position recovery), while others may
not be (e.g. detecting tailing of other aircraft, airspace infringements, failure to take avoiding action prior to a
collision). When FLARM makes a transmission, the signal also bears a unique identification code that can
trace to the pilot or aircraft registration. The user can - even though this is not recommended - configure the
unit so that identification is generated randomly and alters at one-minute intervals, making a back-trace
difficult.
Operation of FLARM is limited to non-commercial day VFR flights. FLARM may not be used for navigational
purposes or aerobatics.
FLARM has not been certified in line with the usual aviation procedures, however tests in line with DO-160/F
on high/low ops temperature, high/low ground survive temperature, pressure altitude, magnetic effects,
emission of radio frequency energy, electrostatic discharge and flammability have been conducted. The
FLARM software development is in-line with typical methods applied for industrial electronics.
Operation of FLARM is forbidden in the USA or Canada or in aircraft registered in the USA or Canada.
The association FLARM Technology, FLARM Technology GmbH, its associates, owners, staff, management,
development team, suppliers, manufacturers and data suppliers accept no responsibility for any damage or
claims that may arise from use of FLARM.