Warning systems: GPWS, EGPWS, TCAS
Navigation · Chapter 33 · DGCA CPL and ATPL
The ground proximity warning modes and what to do, how EGPWS looks ahead, and how TCAS finds traffic and resolves conflicts.
Remember
- GPWS 50–2 450 ft: 1 sink rate, 2 terrain closure, 3 sink after take-off, 4 too low gear/flaps, 5 glide slope, 6 call-outs, 7 windshear.
- PULL UP: wings level, maximum climb.
- EGPWS: terrain database + position: looks ahead 40–60 s.
- TCAS: 1030 out, 1090 back; needs a transponder. TA 45-35 s, RA 35-15 s before collision.
- Symbols: hollow cyan, solid cyan, amber circle, red square. TA: look; RA: follow at once.
Warning, caution, advisory: and the altitude, speed and stall alerts
Three levels, and the simple warnings
- The cockpit shouts in three voices • Warning: red light, loud sound, act now. • Caution: amber light, one chime, act soon. • Advisory: amber words only. • Listen: the speaker button is on the picture.
- Where the words appear • The two lights get your eye. The words say why. • They appear under the engine dials on the centre screen.
- Altitude alert • You set a height on the glareshield. A chord sounds as you near it, and again if you drift off it. • It knows nothing about terrain or traffic.
- Overspeed • Past the maximum speed (VMO/MMO) a loud clacker sounds. You cannot cancel it. Slow down.
- Stall warning • It reads the angle of attack, not the speed. • It warns early: the stick shaker shakes the control in your hand, and a voice calls.
What warns you of the ground, and how?
GPWS modes 1 to 3
- What GPWS is • gpws (ground proximity warning system) watches your height over the ground and shouts if something is wrong. • It uses the radio altimeter (the pink beam), plus speed, gear, flaps and glide slope. • It works from about 50 to 2 450 ft.
- Mode 1: sinking too fast • Coming down too fast for your height. • First "SINK RATE". Then "PULL UP". • Watch the aircraft and listen.
- Mode 2: the ground coming up • You are level, but a hill rises under you. • "TERRAIN, TERRAIN", then "PULL UP".
- Mode 3: sinking after take-off • Just after take-off you should only go up. • If you lose height: "DON'T SINK".
- What the crew does • On PULL UP: wings level, full power, climb hard. • Find out why later.
Low with the wheels up, below the slope, bank, windshear
GPWS modes 4 to 7
This lesson is part of the Navigation plan. See plans
Why can GPWS not see a cliff ahead, and how does EGPWS?
EGPWS: looking ahead
This lesson is part of the Navigation plan. See plans
How does TCAS see other aircraft, and what does it tell you?
TCAS
This lesson is part of the Navigation plan. See plans
Test yourself on chapter 33
Test yourself
This lesson is part of the Navigation plan. See plans