Section 8 Terrain Awareness Warning System
1
st
Ed Nov 2018
IDU-450 EFIS Software Version 8.0H (Rotorcraft)
8-5
upon TAWS type, FLTA mode, groundspeed, bank angle, and vertical
speed. Basic envelope parameters are as follows.
1)
TAWS Type
: Determines value of several parameters used to
calculate the search envelope.
Table 8-2: FLTA Search Envelope for HTAWS
Envelope Parameter
Level-Off Rule
10% of vertical speed
Used for level off leading for
descending flight reduced
required terrain clearance (RTC)
Range
36 seconds of the forward range
search envelope
Reduced to 24 seconds when low
altitude mode is engaged.
GPS/SBAS HFOM is added to
range.
Enroute Mode Level/Climbing
Flight RTC
150 feet
Reduced to 100 feet when low
altitude mode is engaged.
Terminal Mode Level/Climbing
Flight RTC
Approach Mode Level/Climbing
Flight RTC
Departure Mode Level/Climbing
Flight RTC
100 feet
Enroute Mode Descending RTC
Terminal Mode Descending RTC
Approach Mode Descending RTC
Departure Mode Descending RTC
2)
Aircraft Track
: Terrain search envelope is aligned with aircraft track.
3)
Aircraft Groundspeed
: Used in conjunction with range parameter to
determine look-ahead distance and used in with FLTA mode to
determine the search volume width as follows:
a)
Enroute Mode
: Based on a 30
change in track followed by 30
seconds of flight at aircraft groundspeed. Maximum width is 0.5NM
either side of track.
b)
Terminal Mode
: Based on a 15
change in track followed by 30
seconds of flight at aircraft groundspeed. Maximum width is 0.5NM
either side of track.
