While the active route page offers the necessary functions for creating, monitoring
and modifying the active route, the GPS 155’s CDI page is used to provide turn antic-
ipation, next desired track and waypoint arrival information to the pilot.
During route navigation, the GPS 155’s
turn anticipation feature
will smooth
out the transition between adjacent route legs by providing navigation along a curved
path segment. This leg transition is based on the aircraft’s actual ground speed and
the difference between the course angle of the two legs. The GPS 155 will automati-
cally sequence to the next leg when you are abeam the ‘active to’ waypoint and on
the curved transition segment (the to/from indicator on the CDI will flip momentari-
ly). During the transition, the CDI display will be referenced to the dotted line illus-
trated above. Turn anticipation will not be provided in the following scenarios:
• Waypoint/fix crossing is a requirement of the approach, SID or STAR
you’re navigating.
• The GPS SEQ switch is in the HOLD position.
• Automatic leg sequencing is disabled.
• Your current ground speed and the course angle between the two legs would
require a bank angle greater than 25º (see left).
60
DIRECT-TO & ROUTE NAV
Turn Anticipation
The GPS 155’s turn anticipation feature smooths
out the transitions between adjacent legs based on
a nominal bank angle of 15º, with the ability to
roll up to 25º. If the turn angle and your present
speed will require a bank angle that exceeds 25º,
you’ll be notified with a ‘Steep turn ahead’ mes-
sage approximately 90 seconds before arrival at
the active to waypoint.
If the leg transition is too short for a smooth tran-
sition, a ‘Leg not smoothed’ message will appear,
and the pilot should expect a rapid change in the
CDI deflection.
155man (GOOD) 7/24/98 1:57 PM Page 60
Summary of Contents for GPS 155TSO
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