Gpws

Short and simple explanation of GPWS

🧭 Ground Proximity Warning System (GPWS) — Simple Explanation

The GPWS helps prevent Controlled Flight Into Terrain (CFIT) by warning pilots if the aircraft is getting too close to the ground.

It continuously monitors height above ground and rate of descent using a downward-facing radio (radar) altimeter.

⚙️ How It Works

The radio altimeter measures the aircraft’s height directly above the terrain.
The system also uses other inputs:
- Barometric rate of descent
- Airspeed
- Aircraft configuration (gear, flaps)
- ILS glideslope deviation
If the descent rate or terrain closure is too high, it gives aural and visual warnings, such as:
- “TERRAIN, TERRAIN”
- “PULL UP!”
- “SINK RATE!”

⚠️ Limitation

GPWS only looks directly below the aircraft — it cannot see terrain ahead or over rising ground until it’s already close. That’s why it’s called a “reactive” system.

✈️ EGPWS / TAWS (Modern Version)

Later systems — Enhanced GPWS (EGPWS) or TAWS — include:

A terrain database
GPS/FMS position data → allowing forward-looking terrain warnings (predictive, not just reactive).

✅ In short:

GPWS uses the radio altimeter to detect how close the aircraft is to the ground and warns of dangerous descent or terrain proximity — but it only “sees” below, not ahead. EGPWS/TAWS adds a terrain database and GPS, giving forward-looking protection.

Perfect 👏 — that’s a great summary of GPWS modes (Ground Proximity Warning System). Here’s a clear, short explanation of what it all means and how to remember it 👇

🧭 GPWS (Ground Proximity Warning System) – Summary

The GPWS monitors the aircraft’s height above terrain, rate of descent, and configuration to prevent Controlled Flight Into Terrain (CFIT). It uses data mainly from the radio altimeter, air data computer, and aircraft configuration (gear/flaps).

When a dangerous condition is detected, it gives a visual light and distinct aural warning to alert the pilots.

⚙️ GPWS Modes and Warnings

Mode	Meaning / Trigger	First Aural Alert	Second / Severe Warning
1	Excessive descent rate	“SINK RATE, SINK RATE”	“WHOOP WHOOP PULL UP” (twice)
2	Excessive terrain closure rate (flying toward terrain)	“TERRAIN, TERRAIN”	“WHOOP WHOOP PULL UP” (continuous until safe)
3	Altitude loss after takeoff or go-around	“DON’T SINK” (twice)	—
4a	Too low with gear up	“TOO LOW GEAR” / “TOO LOW TERRAIN”	—
4b	Too low with flaps not in landing position	“TOO LOW FLAPS” / “TOO LOW TERRAIN”	—
5	Below glideslope	“GLIDESLOPE, GLIDESLOPE” (half volume)	“GLIDESLOPE, GLIDESLOPE” (full volume)
6a (optional)	Passing decision height	“MINIMUMS, MINIMUMS”	—
6b (optional)	Excessive bank angle	“BANK ANGLE, BANK ANGLE”	—
7 (optional)	Windshear warning	“CAUTION WINDSHEAR”	“WINDSHEAR, WINDSHEAR”

🧠 How to Remember the Logic

Mode Group	What it Watches	Example Warning
1–3	Altitude and vertical speed	“SINK RATE,” “DON’T SINK”
4	Unsafe configuration	“TOO LOW GEAR,” “TOO LOW FLAPS”
5	Approach deviation	“GLIDESLOPE”
6–7	Advisory or optional modes	“MINIMUMS,” “BANK ANGLE,” “WINDSHEAR”

✅ In short:

The GPWS continuously monitors descent rate, terrain closure, and aircraft configuration. When unsafe conditions are detected, it gives visual and aural alerts like “SINK RATE,” “TERRAIN,” or “PULL UP” to help the crew avoid controlled flight into terrain.