Definition
An onboard safety system that warns the flight crew of potential collision with terrain, obstacles, or the ground. It compares the aircraft's position, altitude, and flight path against an internal worldwide terrain and obstacle database, using GPS and other inputs to predict conflicts well before they happen and issue aural and visual alerts in the cockpit.
Plain English
A system that watches the ground and obstacles around the aircraft and warns the pilots — out loud and on a display — if the aircraft is getting too close to hitting something.
Context Anchor
You may see EGPWS discussed in instrument flying, approach procedures, night operations, low-visibility operations, and flights near mountains or rising terrain.
Derivation
Called 'enhanced' because it improves on the older Ground Proximity Warning System (GPWS). The original GPWS only looked downward using the radar altimeter, so it could only react to terrain directly below. The enhanced version added a forward-looking terrain database and GPS position, so it can see what's ahead, not just underneath.
Why Pilots Care
Provides the last line of defense against controlled flight into terrain, a leading cause of fatal accidents in instrument conditions.
Grounding Statement
If an aircraft is descending in clouds toward rising terrain, EGPWS can warn the pilot before the terrain is visible outside.
Intuition Check
Do not assume EGPWS keeps the aircraft clear of terrain by itself. It is a warning system; the pilot must still fly the aircraft and respond correctly to the alert.
Example Sentence 1
On the missed approach, the EGPWS issued a terrain caution as the aircraft turned toward rising ground east of the airport.
Example Sentence 2
EGPWS uses GPS and a terrain database to give earlier alerts than the original GPWS.