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Class B with no display mandated, Turbine powered with ten or more passenger seats, Class A with display required. Part 121—Class A with display mandated for all operators. For a Class A TAWS, you need additional equipment to provide input to the system: Gear and flap position, radar/ radio altitude, CADC, GPS, Glide Slope and SAT (static air temperature), for example. Here are the alerts and warn-
ings provided by Class A and Class B TAWS (neither system warns of even-toed ungulates):
CFIT happens most often when flying non-precision ap- proaches, now officially called “non-ILS.” Continuous Descent Final Approach (CDFA) is one of the initiatives to address the problem in this phase of flight. In industry parlance, the previous method of flying a non-precision approach such as VOR, NDB, LOC-BC or GPS/RNAV approach was called “Dive-and-Drive.” The phrase describes the technique of diving from each fix on the approach, and then from the FAF to the MDA, and then once level, driving to the MAP.
Mode
Class
Condition
Aural Alert
Aural Warning
1 A/B 3 A/B 4b A
5 A
7 A
Descent rate
Alt. loss after T.O Terrain w/no Flaps Descent below GS Windshear
SINK RATE DON’T SINK TOO LOW-FLAPS GLIDESLOPE WINDSHEAR
PULL UP
None
TOO LOW-TERRAIN GLIDESLOPE
None
PULL UP
This means we’re cruising at a very low altitude, rela- tively slow and often sev- eral miles from the runway.
We would then calcu- late a VDP, Visual Descent Point, from which to de- scend from MDA to the run- way. This type of approach descent differs greatly in stability, consistency, pre- dictability and pilot work- load from a constant rate of descent approach such as on an ILS GS. Most non-pre- cision (non-ILS) approaches now incorporate some form of a CDFA. Combining a
2
A/B
Terrain closure
TERRAIN TERRAIN
PULL UP
4a
A
Terrain w/No Gear
TOO LOW-GEAR
TOO LOW-TERRAIN
4c
A
Rising terrain after T.O.
TOO-LOW TERRAIN
None
6
A/B
Radar Altitude
500/100/50/30/10 etc.
None
##
A/B
Terrain Proximity
CAUTION TERRAIN
TERRAIN TERRAIN
24 • TWIN & TURBINE / February 2023