Ads-B And Mode-S Traffic; Obstacle Collision Warnings - FLARM FUSION PowerFLARM User And Maintenance Manual

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before impact. The warning is active as long as the collision risk remains.
Depending on changes in the predicted flight paths, the warning level may be
downgraded or cease. The collision risk algorithms are sensitive; warnings are only
issued if there is a high probability of a collision within the next 18 seconds. The
margin used depends on several factors, including but not limited to aircraft type
(size), speed, vertical speed, turn radius, and position accuracy.
6.2.1

ADS-B and Mode-S Traffic

PowerFLARM Fusion incorporates a complementary 1090 MHz ADS-B and
transponder (SSR) Mode-S receiver.
The positions of aircraft with ADS-B Out 1090ES will be received and processed
independently of the received integrity and accuracy values (SIL/SDA). For aircraft
with both FLARM and ADS-B Out, Fusion will automatically choose the better
signal. Because of the inherent limitations of the ADS-B system, ADS-B aircraft
will have larger margins than FLARM-equipped aircraft. Collision warnings for
ADS-B Out aircraft will be issued similar to FLARM-equipped aircraft.
Aircraft with a Mode-S transponder will be received when the aircraft is
interrogated by a Secondary Surveillance Radar (SSR) or TCAS/TAS. Since the
transponder signal received is non-directional, the intruder will only be indicated
with approximate distance (e.g. a range ring on the display) and relative altitude,
but without bearing. The approximate distance is based on the signal strength of
the transmission from the other aircraft. Collision warnings will be issued based on
the altitude difference and approximate distance.
The altitude difference to the intruder is calculated using the altitude received from
the own Mode-S transponder, if installed. In other cases, the pressure sensor
inside PowerFLARM Fusion is used, which may deviate from true static pressure.
6.3

Obstacle Collision Warnings

When an obstacle database and license is installed, collision warnings are issued
for static obstacles in the database, such as cable railways, powerlines, and
antenna masts. The annunciation is different from traffic collision warnings; see
the display Operating Manual for details.
The first warning is issued around 18 seconds before impact. The alarm level
increases at 12 and 8 seconds before impact, respectively. The warning is active
as long as the collision risk remains. Depending on changes in the predicted flight
paths, the warning level may be downgraded or cease. The collision risk algorithms
are sensitive; warnings are only issued if there is a high probability of a collision
within the next 18 seconds.
POWERFLARM
FUSION USER AND
MAINTENANCE
MANUAL
Date: 2020-11-10
Version: 1.0
Page: 30 of 49
Document Number:
FTD-078