EGPWS - What is it??
EGPWS - What is it??
Guest
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In simple terms GPWS just looks at you radio altimiter to dertermine if you are about to bump into anything solid, which is useless if you are flying into a vertical cliff sticking out of level ground.
The EGPWS system incorporates a GPS so that the aircraft knows exactly where you are, it also knows the location of terrain all over the world, and so is able to work out if you are going to bump into anything on your route. A much safer system than simply relying on a radio altimiter!
The EGPWS system incorporates a GPS so that the aircraft knows exactly where you are, it also knows the location of terrain all over the world, and so is able to work out if you are going to bump into anything on your route. A much safer system than simply relying on a radio altimiter!
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EGPWS displays any terrain on the Map display that is likely to conflict with the aircraft. Colour coding is used - green for terrain 500' or so below the a/c, amber for terrain near a/c level and red for terrain above a/c level. On the newer updates we even have man made obstacles displayed such as towers. All in all an extremely positive addition to flight safety and terrain awareness.
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Saw a educational video on EGPWS and the story is that the whole earth is broken down into tiny sectors which are given a value for the most prominent piece of terrain in that sector. This info is then linked to the GPS. What I found interesting was the idea this might be the commercial outcome of the cruise missile navigation program.. EGPWS should have a REALLY up to date database for the terrain around Iraq.
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I don't have it in my aircraft, but I believe it also uses the local terrain data base to eliminate spurious warnings at airfields with irregular local terrain. Some airfields with rising terrain just before the threshold are know for spurious warnings. Warnings at these fields will now only be heard if they are real. However, this is only second hand info so may not be correct.
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On the German PPRuNe site i saw this one very recently as an excerpt from B737 infos...
"The GPWS provides alerts for potentially hazardous flight conditions involving
imminent impact with the ground.
(Aircraft with EGPWS)
The GPWS monitors terrain proximity using an internal world wide terrain data
base. Proximate terrain data shows on the navigation display. If there is a potential
terrain conflict, alerts are provided based on estimated time to impact. These alerts
are “look-ahead terrain alerts.”
The GPWS provides alerts based on radio altitude and combinations of barometric
altitude, airspeed, glide slope deviation, and airplane configuration. The alerts are
for:
• excessive descent rate
• excessive terrain closure rate
• altitude loss after takeoff or go-around
• unsafe terrain clearance when not in the landing configuration
• excessive deviation below an ILS glide slope
These alerts are “radio altitude based alerts.”
Ground proximity alerts are accompanied by voice aural alerts and the PULL UP
annunciation on the attitude indicators or, for deviation below glide slope alert, the
BELOW G/S light.
(Aircraft with EGPWS)
Note: Terrain ahead of the airplane may exceed available climb performance. A
ground proximity alert does not guarantee terrain clearance.
(Aircraft without EGPWS)
Note: GPWS does not provide alerts for flight toward vertically sheer terrain, or of
shallow descents when the airplane is in the landing configuration.
(Aircraft with EGPWS)
Look-ahead terrain alerts and radio altitude based alerts are prioritized based on the
level of hazard and the required flight crew reaction time. Look-ahead terrain alerts
and radio altitude based alerts are inhibited by an actual windshear warning (airplane
in windshear).
(Aircraft without EGPWS)
Radio altitude based alerts are prioritized based on the level of hazard and the
required flight crew reaction time. They are inhibited by an actual windshear
warning (airplane in windshear).
Look–Ahead Terrain Alerting
(Aircraft with EGPWS)
The GPWS terrain data base contains detailed terrain data near major airports, and
data in lesser detail for areas between airports. Terrain within 2,000 feet of airplane
barometric altitude shows on the navigation display. The terrain data is not designed
to be an independent navigation aid.
Note: The GPWS terrain data base, look-ahead terrain alerting, and terrain display
do not account for man made obstructions.
(Aircraft with EGPWS)
The terrain display is generated from a data base contained in the GPWS computer
and correlated to GPS position.
Terrain and weather radar cannot show together on a display. If one pilot selects
terrain and the other pilot selects weather radar, each display updates on alternating
sweeps. All other displays (TCAS, LNAV routing, etc.) can show with terrain data.
Look-ahead terrain alerts are based on the airplane’s position, barometric altitude,
vertical flight path, and ground speed."
"The GPWS provides alerts for potentially hazardous flight conditions involving
imminent impact with the ground.
(Aircraft with EGPWS)
The GPWS monitors terrain proximity using an internal world wide terrain data
base. Proximate terrain data shows on the navigation display. If there is a potential
terrain conflict, alerts are provided based on estimated time to impact. These alerts
are “look-ahead terrain alerts.”
The GPWS provides alerts based on radio altitude and combinations of barometric
altitude, airspeed, glide slope deviation, and airplane configuration. The alerts are
for:
• excessive descent rate
• excessive terrain closure rate
• altitude loss after takeoff or go-around
• unsafe terrain clearance when not in the landing configuration
• excessive deviation below an ILS glide slope
These alerts are “radio altitude based alerts.”
Ground proximity alerts are accompanied by voice aural alerts and the PULL UP
annunciation on the attitude indicators or, for deviation below glide slope alert, the
BELOW G/S light.
(Aircraft with EGPWS)
Note: Terrain ahead of the airplane may exceed available climb performance. A
ground proximity alert does not guarantee terrain clearance.
(Aircraft without EGPWS)
Note: GPWS does not provide alerts for flight toward vertically sheer terrain, or of
shallow descents when the airplane is in the landing configuration.
(Aircraft with EGPWS)
Look-ahead terrain alerts and radio altitude based alerts are prioritized based on the
level of hazard and the required flight crew reaction time. Look-ahead terrain alerts
and radio altitude based alerts are inhibited by an actual windshear warning (airplane
in windshear).
(Aircraft without EGPWS)
Radio altitude based alerts are prioritized based on the level of hazard and the
required flight crew reaction time. They are inhibited by an actual windshear
warning (airplane in windshear).
Look–Ahead Terrain Alerting
(Aircraft with EGPWS)
The GPWS terrain data base contains detailed terrain data near major airports, and
data in lesser detail for areas between airports. Terrain within 2,000 feet of airplane
barometric altitude shows on the navigation display. The terrain data is not designed
to be an independent navigation aid.
Note: The GPWS terrain data base, look-ahead terrain alerting, and terrain display
do not account for man made obstructions.
(Aircraft with EGPWS)
The terrain display is generated from a data base contained in the GPWS computer
and correlated to GPS position.
Terrain and weather radar cannot show together on a display. If one pilot selects
terrain and the other pilot selects weather radar, each display updates on alternating
sweeps. All other displays (TCAS, LNAV routing, etc.) can show with terrain data.
Look-ahead terrain alerts are based on the airplane’s position, barometric altitude,
vertical flight path, and ground speed."
