OPERATING MANUAL FLARM COLLISION WARNING UNIT
Version 4.06E
Page 12 of 12
March 28, 2009
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.
