Garmin GDL 88 Series Pilots Guide - Page 27

if available, Height Above Terrain as provided by a GNS or GTN navigator

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As in some TCAS I TA implementations, altitude above terrain is used to adjust the sensitivity of the CSA algorithm to minimize nuisance alerts. Radar Altitude (if available), Height Above Terrain (as provided by a GNS or GTN navigator with a terrain database), and Geodetic Altitude are used to adjust the sensitivity of the CSA algorithm in accordance with the following table: Sensitivity Radar Altitude Height Above GPS Phase of Ownship Alt Look- Vertical Incremental Level (feet) Terrain (HAT) Flight* (feet) Ahead Threshold Protected (if Available)* Time(s) for Alarm Volume (NM) (sec) (feet) 4 Up to 1000 Any (RA or HAT) Any Any 20 850 0.20 4 Unavailable Any Any Any 20 850 0.20 4 Unavailable Unavailable Approach Any 20 850 0.20 5 >1000 Any 1000 Any 2350 approach and not Terminal (including unavailable) 7 Unavailable Unavailable Not >5000 40 850 0.55 or >2350 or >2350 approach 10,000 45 850 0.80 or >2350 or >2350 approach 20,000 48 850 1.10 or >2350 or >2350 approach

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4-7
190-01122-03
Rev. E
Garmin GDL 84/88 ADS-B Transceiver Pilot’s Guide
As in some TCAS I TA implementations, altitude above terrain is used to adjust
the sensitivity of the CSA algorithm to minimize nuisance alerts. Radar Altitude
(if available), Height Above Terrain (as provided by a GNS or GTN navigator with
a terrain database), and Geodetic Altitude are used to adjust the sensitivity of the
CSA algorithm in accordance with the following table:
Sensitivity
Level
Radar Altitude
(feet)
Height Above
Terrain (HAT)
(if Available)*
GPS Phase of
Flight*
Ownship Alt
(feet)
Look-
Ahead
Time(s)
(sec)
Vertical
Threshold
for Alarm
(feet)
Incremental
Protected
Volume (NM)
4
Up to 1000
(RA or HAT)
Any
Any
Any
20
850
0.20
4
Unavailable
Any
Any
Any
20
850
0.20
4
Unavailable
Unavailable
Approach
Any
20
850
0.20
5
>1000
<=2350
Any
Any
Any
25
850
0.20
5
Unavailable
>1000
<=2350
Any
Any
25
850
0.20
5
Unavailable
Unavailable
Terminal
Any
25
850
0.20
6
Unavailable
or >2350
Unavailable
or >2350
Not
approach
and not
Terminal
(including
unavailable)
<=5000
30
850
0.35
7
Unavailable
or >2350
Unavailable
or >2350
Not
approach
and not
Terminal
(including
unavailable)
>5000
<=10,000
40
850
0.55
8
Unavailable
or >2350
Unavailable
or >2350
Not
approach
and not
Terminal
(including
unavailable)
>10,000
<=20,000
45
850
0.80
9
Unavailable
or >2350
Unavailable
or >2350
Not
approach
and not
Terminal
(including
unavailable)
>20,000
<=42,000
48
850
1.10