EGPWS
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Tx mcdhu for your reply and link, but I cannot find ,what really I am looking for,the differences between the gpws and the egpws.
So, if somebody out there knows ......
RD
So, if somebody out there knows ......
RD
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Try these:
GPWS: http://www.boeing-727.com/Data/systems/infogpws.html.
The 'different modes' are detailed there.
EGPWS: http://www.honeywell.com/sites/aero/Egpws-Home.htm - which you have already had. I'm ASSUMING you have fully explored link 2 so you know all about the different modes? (Have you read 'General Information'?)
===============================
EGPWS has, amongst other things, a database of terrain - so assuming it knows where the a/c is (IRS/GPS/FMC) it can produce 'enhanced' warning of terrain problems, and also show the crew the elevations of terrain in their vicinity. It also has airports in the database so with accurate positional information it knows whether you are descending to destruction or making an approach on a known airport. It also introduces a few other modes (which are also in the link).
GPWS: http://www.boeing-727.com/Data/systems/infogpws.html.
The 'different modes' are detailed there.
EGPWS: http://www.honeywell.com/sites/aero/Egpws-Home.htm - which you have already had. I'm ASSUMING you have fully explored link 2 so you know all about the different modes? (Have you read 'General Information'?)
===============================
EGPWS has, amongst other things, a database of terrain - so assuming it knows where the a/c is (IRS/GPS/FMC) it can produce 'enhanced' warning of terrain problems, and also show the crew the elevations of terrain in their vicinity. It also has airports in the database so with accurate positional information it knows whether you are descending to destruction or making an approach on a known airport. It also introduces a few other modes (which are also in the link).
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In laymans terms, the EGPWS will give you warning for rising terrain ahead of you, whilst the GPWS will not be able to give you same warning. Rest of the modes are the same. The EGPWS has one extra more for rising terraing ahead.
If you want technical details I can dig in my notes and post them here.
If you want technical details I can dig in my notes and post them here.
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On the Airbus 319, the Ground Proximity Warning System (GPWS) generates aural and visual warnings, when one of the following conditions occurs between radio altitudes 30 and 2450 feet.
1. Excessive descent rate, "Sink rate"
2. Excessive terrain closure, "Terrain, terrain"
3. Altitude loss after T.O, "Dont sink"
4. Unsafe terrain clearance, "Too low flaps - Too low gear - Too low terrain"
5. excessive G/S deviation, "Glideslope"
In addition to the basic GPWS functions, the GPWS has an enhanced function (EGPWS) which provides, based on a worldwide terrain database:
A) A Terrain Awareness Display (TAD), which predicts the terrain conflict, and displays the terrain on the Nav Display. The Terrain Awareness and Display (TAD) function computes a caution and a warning envelope in front of the aircraft, depending on the aircraft altitude, the nearest runway altitude, the distance to the nearest runway threshold, the ground speed, and the turn rate. When the boundary of these envelopes conflicts with the terrain, or with an obstacle memorized in the database, the system generates the relevant alert. On the 'Bus you get 60 secs for an amber caution and 30 secs for a red warning.
B) A Terrain Clearance Floor (TCF), which improves the low terrain warning during landing. A terrain clearance floor envelope is stored in the database for each runway for which terrain data exist. The Terrain Clearance Floor (TCF) function warns of a premature descent below this floor, regardless of the aircraft's configuration.
The EGPWS uses the geometric altitude. The geometric altitude is calculated by means of a specific algorithm that uses the following as inputs : The pressure altitude, GPS altitude, radio altitude, and data from the terrain database.
If you receive a caution or warning you are required to do something about it!
1. Excessive descent rate, "Sink rate"
2. Excessive terrain closure, "Terrain, terrain"
3. Altitude loss after T.O, "Dont sink"
4. Unsafe terrain clearance, "Too low flaps - Too low gear - Too low terrain"
5. excessive G/S deviation, "Glideslope"
In addition to the basic GPWS functions, the GPWS has an enhanced function (EGPWS) which provides, based on a worldwide terrain database:
A) A Terrain Awareness Display (TAD), which predicts the terrain conflict, and displays the terrain on the Nav Display. The Terrain Awareness and Display (TAD) function computes a caution and a warning envelope in front of the aircraft, depending on the aircraft altitude, the nearest runway altitude, the distance to the nearest runway threshold, the ground speed, and the turn rate. When the boundary of these envelopes conflicts with the terrain, or with an obstacle memorized in the database, the system generates the relevant alert. On the 'Bus you get 60 secs for an amber caution and 30 secs for a red warning.
B) A Terrain Clearance Floor (TCF), which improves the low terrain warning during landing. A terrain clearance floor envelope is stored in the database for each runway for which terrain data exist. The Terrain Clearance Floor (TCF) function warns of a premature descent below this floor, regardless of the aircraft's configuration.
The EGPWS uses the geometric altitude. The geometric altitude is calculated by means of a specific algorithm that uses the following as inputs : The pressure altitude, GPS altitude, radio altitude, and data from the terrain database.
If you receive a caution or warning you are required to do something about it!
Last edited by Craggenmore; 8th Oct 2006 at 10:05.
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And in further integration of cockpit avionics, the latest and greatest weather radars are using this terrain data base for auto tilt, along with software that modifies gain for what part of the world you are in....pretty neat.
Hit the Honeywell or Rockwell sites for more info.
Hit the Honeywell or Rockwell sites for more info.
Last edited by Shore Guy; 8th Oct 2006 at 10:28. Reason: spelling
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bold from me
EGPWS is only as good as the database, isn´t it?
Wasn´t an E-jet attempting to land at Suvarnabhumi confused by a warning that no airport existed there? What is a pilot supposed to do about EGPWS warnings related to nonexistence of runways, or obstacles that only exist in database (since demolished/collapsed)?
In addition to the basic GPWS functions, the GPWS has an enhanced function (EGPWS) which provides, based on a worldwide terrain database:
A) A Terrain Awareness Display (TAD), which predicts the terrain conflict, and displays the terrain on the Nav Display. The Terrain Awareness and Display (TAD) function computes a caution and a warning envelope in front of the aircraft, depending on the aircraft altitude, the nearest runway altitude, the distance to the nearest runway threshold, the ground speed, and the turn rate. When the boundary of these envelopes conflicts with the terrain, or with an obstacle memorized in the database, the system generates the relevant alert. On the 'Bus you get 60 secs for an amber caution and 30 secs for a red warning.
B) A Terrain Clearance Floor (TCF), which improves the low terrain warning during landing. A terrain clearance floor envelope is stored in the database for each runway for which terrain data exist. The Terrain Clearance Floor (TCF) function warns of a premature descent below this floor, regardless of the aircraft's configuration.
The EGPWS uses the geometric altitude. The geometric altitude is calculated by means of a specific algorithm that uses the following as inputs : The pressure altitude, GPS altitude, radio altitude, and data from the terrain database.
If you receive a caution or warning you are required to do something about it!
A) A Terrain Awareness Display (TAD), which predicts the terrain conflict, and displays the terrain on the Nav Display. The Terrain Awareness and Display (TAD) function computes a caution and a warning envelope in front of the aircraft, depending on the aircraft altitude, the nearest runway altitude, the distance to the nearest runway threshold, the ground speed, and the turn rate. When the boundary of these envelopes conflicts with the terrain, or with an obstacle memorized in the database, the system generates the relevant alert. On the 'Bus you get 60 secs for an amber caution and 30 secs for a red warning.
B) A Terrain Clearance Floor (TCF), which improves the low terrain warning during landing. A terrain clearance floor envelope is stored in the database for each runway for which terrain data exist. The Terrain Clearance Floor (TCF) function warns of a premature descent below this floor, regardless of the aircraft's configuration.
The EGPWS uses the geometric altitude. The geometric altitude is calculated by means of a specific algorithm that uses the following as inputs : The pressure altitude, GPS altitude, radio altitude, and data from the terrain database.
If you receive a caution or warning you are required to do something about it!
Wasn´t an E-jet attempting to land at Suvarnabhumi confused by a warning that no airport existed there? What is a pilot supposed to do about EGPWS warnings related to nonexistence of runways, or obstacles that only exist in database (since demolished/collapsed)?
If your EGPWS warning activates when you are IMC then you must follow it. If you are VMC then you can make a Captaincy decision. Many of the early warnings you refer to were caused by the airfield but not the runway being in the database.
The database is updated regularly by Honeywell. Your company should update your aircraft regulalry and check that your destination is in the database as part of the flight planning process.
If you wish to check yourself then you can do so herehttp://www.honeywell.com/sites/aero/...7B.htm#Airport
The database is updated regularly by Honeywell. Your company should update your aircraft regulalry and check that your destination is in the database as part of the flight planning process.
If you wish to check yourself then you can do so herehttp://www.honeywell.com/sites/aero/...7B.htm#Airport
rduarte see the EGPWS descriptions available from the Honeywell links above.
The new ‘EGPWS’ modes are described as ‘Enhanced’; the descriptions of modes 1-6 are essentially the ‘old’ GPWS. However, note that the warning logic for all modes (particularly the Enhanced capabilities) is under continuous review and may have been updated on several occasions. Operators should frequently check for system software revisions in addition to the terrain, runway, and obstacle database revisions. References to all aspects of these updates are in the Honeywell website.
EGPWS also includes optional ‘peeks’, geometric altitude, and obstacle modes, each offering major safety advantages; other new and revised operating modes are being developed.
The obstacle mode is available in all EGPWS ‘boxes’ although not all aircraft have been configured. Operators should seriously consider activating the obstacle mode (minor mod – wire change); there has been at least one large commercial aircraft ‘save’ due to an obstacle warning – and at least two near misses without the mode activated.
This is a very limited description; EGPWS warnings will be given for any terrain (rising, level or falling) whenever the aircraft infringes the alerting or warning boundaries.
No. The ‘old GPWS’ modes still work even if the Enhanced terrain functions are inhibited. The enhanced databases are comprehensive, highly reliable and updated regularly; the Honeywell web site has the technical details. If a new airport/runway is not in the database then report it to Honeywell. If you get an alert or warning, report those also – air safety report. All events are recorded in EGPWS memory and can be downloaded to assist with an investigation. All events must be investigated to establish the reasons for the alert. Follow the philosophy that there are ‘no false warnings’ with EGPWS; there is always a reason, and considering the alternatives in the air is not an option.
Many operators are considering removing the Captains decision in ‘VMC’ as EGPWS is a highly reliable system. With a warning in VMC the aircraft is not where it ought to be – it is not on a safe flight path. A recent FSF presentation identified several instances where crew did not react correctly (believing that they were VMC) and the aircraft narrowly escaped an accident. Human error – believing that you know where you are was a dominant contribution as was night ‘VMC’ black hole illusions – low approach and you do not realize – both pilots suffers the same effect.
EGPWS uses advanced technology, is highly reliable, and provides excellent safety displays in normal operation – always display the terrain on one EFIS during take off and particularly during descent and approach; this may prevent an alert that you did not expect – and a visit to the Chief Pilots Office.
The new ‘EGPWS’ modes are described as ‘Enhanced’; the descriptions of modes 1-6 are essentially the ‘old’ GPWS. However, note that the warning logic for all modes (particularly the Enhanced capabilities) is under continuous review and may have been updated on several occasions. Operators should frequently check for system software revisions in addition to the terrain, runway, and obstacle database revisions. References to all aspects of these updates are in the Honeywell website.
EGPWS also includes optional ‘peeks’, geometric altitude, and obstacle modes, each offering major safety advantages; other new and revised operating modes are being developed.
The obstacle mode is available in all EGPWS ‘boxes’ although not all aircraft have been configured. Operators should seriously consider activating the obstacle mode (minor mod – wire change); there has been at least one large commercial aircraft ‘save’ due to an obstacle warning – and at least two near misses without the mode activated.
No. The ‘old GPWS’ modes still work even if the Enhanced terrain functions are inhibited. The enhanced databases are comprehensive, highly reliable and updated regularly; the Honeywell web site has the technical details. If a new airport/runway is not in the database then report it to Honeywell. If you get an alert or warning, report those also – air safety report. All events are recorded in EGPWS memory and can be downloaded to assist with an investigation. All events must be investigated to establish the reasons for the alert. Follow the philosophy that there are ‘no false warnings’ with EGPWS; there is always a reason, and considering the alternatives in the air is not an option.
EGPWS uses advanced technology, is highly reliable, and provides excellent safety displays in normal operation – always display the terrain on one EFIS during take off and particularly during descent and approach; this may prevent an alert that you did not expect – and a visit to the Chief Pilots Office.
chornedsnorkack EGPWS does not provide protection on the ground; some versions might warn of windshear during take off.
However, associated equipment - Runway Awareness and Advisory System (RAAS) will provide warnings to alert crews of an incorrect runway, taxiway, etc. The Honeywell system is described in their web pages. It would have given an alert at Lexington, but a warning at Taipei would have required the NOTAM of runway closure to be included in the RAAS database.
However, associated equipment - Runway Awareness and Advisory System (RAAS) will provide warnings to alert crews of an incorrect runway, taxiway, etc. The Honeywell system is described in their web pages. It would have given an alert at Lexington, but a warning at Taipei would have required the NOTAM of runway closure to be included in the RAAS database.
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Captaincy means:
The captain can decide to override a GPWS warning when the aircraft is:
The captain can decide to override a GPWS warning when the aircraft is:
- 1000 ft vertically clear of clouds
- 1km horizontally clear of clouds
- In 8.5 km of clear visibility
- Flying in daytime
- Obviously not in danger
The definition of captaincy above is quite reasonable; arguably, its application during the early years of GPWS enabled crews to discount obvious system faults. However as the system reliability improved (sensor inputs - dual / monitored rad alts or rain protected rad alt) then the use of captain’s discretion could have been reduced; I would argue (perhaps with hindsight) that it should have been removed as demonstrated by several accidents where GPWS warnings were ignored or the pull up commenced too late.
The underlying issue is that as systems improve and new technology is employed, SOPs are rarely reviewed.
EGPWS is at least ten times more reliable than the early GPWS and for those systems configured with the most accurate navigation sensor inputs (embedded GPS) the reliability may be 100 times better. Thus the installation of EGPWS probably crosses the boundary where the human is more likely to make a mistake than the ‘machine’ is, even with the safeguards of captaincy.
Whilst the TAWS events reported above (FSF European Air Safety Seminar Athens Mar 06) met the captaincy definition except they were at night, the crew could have experience increased mental workload due to recalling the rule and deciding if it applies to the situation (day/night); immediate situation assessment is high workload and unnecessary if a pull up is always flown.
Current safety thinking on threat and error management is to avoid hazards and opportunities for error i.e. the captaincy judgment on the conditions existing at the time of the warning.
In addition to the need to change SOPs as technology improves, there is also a need to change the way we think about alerting and warning equipment. GPWS alerted the crew to the threat of terrain closure; the enhanced modes of EGPWS could be considered to alert the crew to an error. Either their error or someone else’s error, but whatever the reason the aircraft is not where it should be. Thus, EGPWS is a form of active Flight Ops Quality Assurance / Flight Data Monitoring (FOQA/FDM). The use of the terrain display during those flight phases where the threat of terrain is most likely adds a further safety layer by providing the crew with the ability to detect an impending FDM event without an event being recorded.
Whatever our viewpoint of EGPWS, it is a major step forward in flight safety. We should not degrade this by allowing pilots opportunity for erroneous behavior with unnecessary captaincy.
The underlying issue is that as systems improve and new technology is employed, SOPs are rarely reviewed.
EGPWS is at least ten times more reliable than the early GPWS and for those systems configured with the most accurate navigation sensor inputs (embedded GPS) the reliability may be 100 times better. Thus the installation of EGPWS probably crosses the boundary where the human is more likely to make a mistake than the ‘machine’ is, even with the safeguards of captaincy.
Whilst the TAWS events reported above (FSF European Air Safety Seminar Athens Mar 06) met the captaincy definition except they were at night, the crew could have experience increased mental workload due to recalling the rule and deciding if it applies to the situation (day/night); immediate situation assessment is high workload and unnecessary if a pull up is always flown.
Current safety thinking on threat and error management is to avoid hazards and opportunities for error i.e. the captaincy judgment on the conditions existing at the time of the warning.
In addition to the need to change SOPs as technology improves, there is also a need to change the way we think about alerting and warning equipment. GPWS alerted the crew to the threat of terrain closure; the enhanced modes of EGPWS could be considered to alert the crew to an error. Either their error or someone else’s error, but whatever the reason the aircraft is not where it should be. Thus, EGPWS is a form of active Flight Ops Quality Assurance / Flight Data Monitoring (FOQA/FDM). The use of the terrain display during those flight phases where the threat of terrain is most likely adds a further safety layer by providing the crew with the ability to detect an impending FDM event without an event being recorded.
Whatever our viewpoint of EGPWS, it is a major step forward in flight safety. We should not degrade this by allowing pilots opportunity for erroneous behavior with unnecessary captaincy.
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It still leaves the problem, alf, of when the navigational accuracy of the FMS/Map is suspect - eg INN, where only 1 DME is available for a 737 Classic to obtain an update on position in the valley - ie it cannot update, and the FMS position will 'wander' towards the INS position, which may be far enough away from reality to assume a mountain where one does not exist. All the clever terrain maps/call-outs are of no use if the a/c does not know where it is. Thus the VMC over-ride option is required.
Once we get to a state where the nav accuracy is practically guaranteed then I agree with you.
Once we get to a state where the nav accuracy is practically guaranteed then I agree with you.
The ‘captaincy’ solution degrades the effectiveness of EGPWS by amending its intended use to alleviate the deficiencies of a navigation system.
If a navigation error exists or is likely to exist then the enhanced part of EGPWS can be switched off (previous FAA solution). The aircraft is then exposed to the hazards of the ‘unacceptable’ risks of CFIT. [Unacceptable because EGPWS is mandated equipment.]
Alternatively if it is not known that the navigation accuracy is degraded, then in day/VMC you could exercise ‘captaincy’, but in night/IMC the only option is to pull up.
Many of these aspects were considered in the initial operational certification - and before the ‘what if’ replies appear, turning flight was (is) not an option after a warning, and any additional risk from a pull up is nil, it is safe flight.
Operators could improve the navigation system; map shifts have contributed to CFIT incidents.
Alternatively adding a GPS module to EGPWS has many advantages including providing CFIT protection with a map shift, and although the cost of GPS may not balance, it would offset the commercial damage of a CFIT accident. Thus the debate might be one of economics and safety culture, but of course the bean counters suffer the same ‘risk aversion’ and error proneness that the crew do.
A cheaper solution which maintains the current ‘EGPWS level of safety’ is to remove the captain’s option. I do not have data on the number of unnecessary pull ups flown, but from about 15 reports of EGPWS ‘saves / ‘near misses’, in a significant proportion (5/15) the crew either did not pull up or they reacted incorrectly. Retaining the ‘captaincy’ option encourages crews to violate SOPs (human nature), and additionally increases workload as discussed previously.
The industry has been very fortunate not to have suffered a CFIT accident with an aircraft fitted with EGPWS; the dominant contribution in the incidents so far has been human error – perception, which is a component of ‘captaincy’. I believe that operations are safer without the EGPWS captaincy opt-out.
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PWS Is a radar function and (A'bus) the FAC gives the windshear wng.
In the Boeing hasn't it got something to do with the FDs???
FlapsOne Perhaps I could have clarified my post; ‘during take-off’ is from rotation onwards. The following description is from the Honeywell EGPWS pilots guide.
“Mode 7 is designed to provide alerts if the aircraft encounters windshear. Two alerting envelopes provide either a Windshear Caution alert or a Windshear Warning alert each with distinctive aural and visual indications to the flight crew.
EGPWS windshear is provided for certain (not all) aircraft types and is a function of certain additionally required input signals and enabled internal detection algorithms. These are established during the initial installation and addressed in the appropriate Airplane Flight Manual (AFM) or EGPWS Airplane Flight Manual Supplement (AFMS).
Mode 7 Windshear alerting is active under the following conditions:
• During takeoff; from rotation until an altitude of 1500 feet AGL is reached,
• During approach; From an altitude of 1500 feet down to 10 feet AGL,
• During a missed approach; until an altitude of 1500 feet AGL is reached.”
EGPWS does not provide predictive windshear warning (PWS), which as you state is normally a radar function.
“Mode 7 is designed to provide alerts if the aircraft encounters windshear. Two alerting envelopes provide either a Windshear Caution alert or a Windshear Warning alert each with distinctive aural and visual indications to the flight crew.
EGPWS windshear is provided for certain (not all) aircraft types and is a function of certain additionally required input signals and enabled internal detection algorithms. These are established during the initial installation and addressed in the appropriate Airplane Flight Manual (AFM) or EGPWS Airplane Flight Manual Supplement (AFMS).
Mode 7 Windshear alerting is active under the following conditions:
• During takeoff; from rotation until an altitude of 1500 feet AGL is reached,
• During approach; From an altitude of 1500 feet down to 10 feet AGL,
• During a missed approach; until an altitude of 1500 feet AGL is reached.”
EGPWS does not provide predictive windshear warning (PWS), which as you state is normally a radar function.