activity simultaneously. A system processor determines the range and bearing of
the lightning energy pulse and forwards the information to the MAUs for formatting
and display on the active radar presentation(s). The processor retains strike
occurrences in memory in order to indicate intensity of lightning activity.
NOTE:
It is also possible to select the display of LSS lightning
strike data on the MAP display or PFD HSI without
weather radar information.
Lightning strikes are represented by white icons with a single strike shown as only
a jagged line, medium activity as a jagged line with an arrow head at the bottom
of the line, and areas of intense lightning depicted as a jagged line with
arrowheads at the top and bottom of the line. See the depiction in Figure 21. The
display criteria is a function of frequency of lightning strikes within a two (2) minute
period for a given area. A medium intensity icon is displayed if three to five (3 - 5)
strikes occur in the same vicinity within two (2) minutes, and an area that suffers
six (6) or more lightning strikes within two (2) minutes is marked by the intense
lightning icon. The initial icon display for a given area will change if the rate of
lighting activity within the monitored time period changes - i.e. if an area of intense
activity decreases to a level of four (4) strikes per two (2) minute period, the icon
will change to the medium activity format.
Whenever lightning is detected by the system, an alert symbol is shown at the
range perimeter of the active display window. The alert symbol is a single strike
icon shown in magenta. The purpose of the alert icon is to identify for the flight
crew the relative bearing from the aircraft of any lightning activity, since the crew
may have selected a display range that does not encompass the strike
occurrence.
The control panel for the LSS is usually mounted on the cockpit center pedestal in
a location determined by the individual customer. The panel has four pushbutton
controls as shown in Figure 22:
•
OFF - selects the LSS off
•
STBY - powers the LSS but places the system in standby mode. In standby
mode the system actively tracks lightning activity and begins storing strike
data in memory
•
LX - selects the display lightning sensing data
•
CLR/TEST - clears the processor lightning strike memory and performs a
system test. During a test, a simulated strike symbol is displayed at a
bearing of forty-five degrees (45°) at a distance of twenty-five nautical
miles (25 nm). The symbol increases in intensity to the maximum strike
icon within fifteen (15) seconds. An alert icon is also displayed only the
bearing line at the perimeter of the range display. The strike icon will
decrease in severity symbology and will be removed from the display after
two (2) minutes.
NOTE:
The system remains active during a test period,
recording and displaying any actual lightning activity in
addition to the test symbology.
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS
2A-31-00
Page 55
July 15/04
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