Efficacy of EGPWS
Join Date: Dec 2007
Location: the land of redemption
Age: 53
Posts: 250
Likes: 0
Received 8 Likes
on
1 Post
Sunnywa,
as long as I know YOU aussies are using NVG hardware for some operations, is that correct?
At time now in Italy we are not operating in Hems/sar at night performing primary resgues (e.g.: get people down from a mountain or go to an highway accident); by night we are only flying HAA hospital transfers.
My personal opinion: I would like to use NVG as civilian pilot doing Hems in mountain environment.
It will take some time, maybe 20 years
!!!
as long as I know YOU aussies are using NVG hardware for some operations, is that correct?
At time now in Italy we are not operating in Hems/sar at night performing primary resgues (e.g.: get people down from a mountain or go to an highway accident); by night we are only flying HAA hospital transfers.
My personal opinion: I would like to use NVG as civilian pilot doing Hems in mountain environment.
It will take some time, maybe 20 years
!!!
Join Date: Jun 2006
Location: Perth, Australia
Posts: 94
Likes: 0
Received 0 Likes
on
0 Posts
G'day Maeroda,
We have only recently started using NVG for helos in Australia. I use mine for Law Enforcement, SAR, EMS (though not actually used it for that yet but we are a backup aircraft). They are absolutely unbelievable in that you can be 500ft above the ground in valleys (even with no moon and overcast) and quite happily see everything. Use of white light out the front also illuminates everything to a better extent.
Go and see your bosses, and tell them NVG is a must for night ops (even pad to pad) especially in that scary terrain from your photos.
Fly safely and hope you get them soon.
Sunnywa
We have only recently started using NVG for helos in Australia. I use mine for Law Enforcement, SAR, EMS (though not actually used it for that yet but we are a backup aircraft). They are absolutely unbelievable in that you can be 500ft above the ground in valleys (even with no moon and overcast) and quite happily see everything. Use of white light out the front also illuminates everything to a better extent.
Go and see your bosses, and tell them NVG is a must for night ops (even pad to pad) especially in that scary terrain from your photos.
Fly safely and hope you get them soon.
Sunnywa
Again it surprises me what I get out of pprune! What maeroda is doing is so very different from what my experience has been. Your use of the system reminds me of the NZ NVFR accident a couple of years ago when the pilot was following an electronic track in a valley at night, missed a waypoint by not very much at all and clipped a bit of terrain. Fortunately the pilot did a great job bringing the aircraft and all the pax home despite some injuries and was able (and humble enough) to share the experience with all of us.
This accident raised the debate to which JimL refers and to which should be again stimulated here: can such systems be used to ensure terrain clearance?
Would you do the same thing in total IMC? What is the difference between total IMC and dark night VFR?
Methinks that unless you can see the ground, get above LSALT. I cannot yet bring myself to rely on my own skills to follow what almost amounts as a form of terrain following radar.
I have often wondered what the procedure would be if you had a GPS or radar failure in those circumstances? (they never fail do they?)
For my money, below LSALT means you must see the ground. Enhanced vision systems (uncooled IR) weigh in at less than 2kg, cost less than $15,000 US and require no training. NVG should be added for night at $40,000 per cockpit and $24,000 for 2 X sets of NVG and weight less than 5kg combined. Cheap, light, no "bitchin", and you see the actual ground, not some software engineers perception of it!!!
Different to off-shore. EVS and a sensibly used RadAlt warning system would suffice I think - but I have no offshore night experience so may be talking crap. As usual!
This accident raised the debate to which JimL refers and to which should be again stimulated here: can such systems be used to ensure terrain clearance?
Would you do the same thing in total IMC? What is the difference between total IMC and dark night VFR?
Methinks that unless you can see the ground, get above LSALT. I cannot yet bring myself to rely on my own skills to follow what almost amounts as a form of terrain following radar.
I have often wondered what the procedure would be if you had a GPS or radar failure in those circumstances? (they never fail do they?)
For my money, below LSALT means you must see the ground. Enhanced vision systems (uncooled IR) weigh in at less than 2kg, cost less than $15,000 US and require no training. NVG should be added for night at $40,000 per cockpit and $24,000 for 2 X sets of NVG and weight less than 5kg combined. Cheap, light, no "bitchin", and you see the actual ground, not some software engineers perception of it!!!
Different to off-shore. EVS and a sensibly used RadAlt warning system would suffice I think - but I have no offshore night experience so may be talking crap. As usual!
Join Date: May 2004
Location: UK
Posts: 109
Likes: 0
Received 0 Likes
on
0 Posts
It is worth reading the Honeywell Pilot Guide for EGPWS XXII. From earlier posts it seems as if the equipment is being relied on when it is not designed for that purpose. The Pilot Guide says:
• The MK XXII is a Situational Awareness tool, and an alerting and
warning device. It is not to be used for navigation of the aircraft.
If you blindly follow EGPWS you could have an accident because it is not designed as an IFR low level (below Safety Altitude) navigation system.
RI
• The MK XXII is a Situational Awareness tool, and an alerting and
warning device. It is not to be used for navigation of the aircraft.
If you blindly follow EGPWS you could have an accident because it is not designed as an IFR low level (below Safety Altitude) navigation system.
RI
One of the issues that we have to face is that the term ‘Controlled Flight into Terrain’ (CFIT) includes accidents which result from ‘loss of control’ (does anyone else think this is a contradiction in terms?) – not exactly what was being considered when GPWS was first thought of.
When Don Bateman started his quest to reduce CFIT, he was probably seeking to reduce/eliminate accidents that were occurring in scheduled services (the term CFIT was developed at Boeing) – mainly in the ‘approach/landing’ and ‘take-off/initial climb’ phases. To see why this is important it is necessary to look at the statistics; the following is from FAA AC 61-134:
To reduce the complexity of the algorithm to assess closure rates to the edge of the safe envelope, the solution is provided in six classic modes (to find out more about the modes read the manual or see a discussion of the practical application to helicopters between Nick Lappos and Helicomparitor on the S92 thread).
Having already made an impressive impact on the accident rate, and because GPS and terrain data bases were becoming available, it became possible to address the en-route accidents - in most cases caused by loss of situational awareness. Hence the introduction of the enhanced mode – i.e. EGPWS. This added synthetic vision displays, and additional algorithms to assess closure rates based on the GPS position and point of conflict in the terrain map in the digital data-base (the accuracy of which may vary in different parts of the world – the US being the most accurate). This accuracy is not usually an issue because it is IFR separation that has to be maintained (1,000ft or 2,000ft in mountainous areas).
Because of this potential lack of accuracy; as stated by ‘running-in’, EGPWS “...is not designed as an IFR low level (below Safety Level) navigation system” nor should it be used as one.
When flying VFR, it is important that the helicopter remains in an environment where the ‘available visual cues’ exceed the ‘required visual cues’. This is not easy to quantify because it will be dependent both upon the handling qualities of the helicopter and skill of the pilot. VFR limits are set to provide the average pilot in the average helicopter with safe margins of operation (and is the reason why there are increments for pilots in training and those with less experience).
It has been known for some time that, as the available visual cues decrease, the pilots attention is inexorably drawn outside the cockpit and handling becomes progressively more difficult until loss of control occurs. This can happen slowly: if the visibility decreases as the flight progresses (or as the light cues reduce at night); or quickly if the helicopter inadvertently enters cloud (or the light cues disappear at night e.g. when cross country or operating in mountains). At the point where control is lost, it is extremely difficult for an experienced test pilot, and almost impossible for an inexperienced pilot, to come back into the cockpit and transition to instruments in an un-stabilised platform.
Obviously a stabilised platform will provide the handling qualities that permit flight in a much reduced visual cue environment; however, adequate handling qualities result not from the basic certification process but from compliance with Appendix B of Parts 27/29. A helicopter that has been certificated for flight in IMC will already have stability and all of the required equipment for IFR flight.
When there are insufficient visual cues to permit visual contact flying, there is no substitute for flight on instruments; but, flight on instruments requires planning, and compliance with the Instrument Flight Rules - which are provided to ensure obstacle clearance. There is no in-between state; either flight can be achieved with visual contact or it cannot; if it cannot, flight should be conducted in accordance with the Instrument Flight Rules.
The use of Synthetic Visual Systems (SVS) are no panacea for scud running or flight without visual contact (adequate light sources) at night; control cannot be maintained by using an SVS as the sole means of attitude orientation. Where they perhaps have their use is where they are provided as part of the instrument suite to provide situational awareness (as an additional safety benefit). That benefit is also limited to those areas where the terrain data-base adequately describes the obstacles; for offshore operations, SVS is of limited use, as its ‘quality’ picture does not adequately describe all obstacles that may be in the area of operation. What would improve the efficacy of the unit would be the addition of an enhanced visual function provided by real time sensors (such as a LiDAR).
EGPWS does not provide solutions for other than IFR flight; it is, as stated by ‘running in’, “...a situational awareness tool and an alerting and warning device”. When used in its correct context – i.e. IFR onshore flying in accordance with the Instrument Flying Rules, it is extremely effective.
Loss of control accidents can be addressed by improving the handling qualities of light helicopters – particularly for flight at night. If that is not possible then addressing the safety culture of pilots and operators – i.e. the HF solution – is the only way. My preference would be to address the handling qualities; compensating for human nature is much too difficult and is rarely sucesssful.
Could EGPWS in helicopters be improved? Well some of us think it could. How? By revisiting the classic mode algorithms and comparing them against the helicopter flight envelopes that can be distilled from the Megabytes of data that has been collected as part of the FDM/HOMP program. A distinction might have to be made between offshore (which as was previously stated is somewhat less complex) and onshore operations.
If this is done we might be able to provide a protection envelope that could have prevented a number of offshore accidents that resulted from flight outside the safe envelope. The ones that immediately come to mind are: the S76 accidents in the GOM and the Dutch section of the North Sea; the AS365 accidents in the Bombay High and Morecombe Bay (although the results of that accident are still awaited), Cormorant Alpha and several accidents in the Far East.
However, that is just my view.
Jim
When Don Bateman started his quest to reduce CFIT, he was probably seeking to reduce/eliminate accidents that were occurring in scheduled services (the term CFIT was developed at Boeing) – mainly in the ‘approach/landing’ and ‘take-off/initial climb’ phases. To see why this is important it is necessary to look at the statistics; the following is from FAA AC 61-134:
According to the CFIT, Education and Training Aid, about 25.0 percent of all accidents occur during the takeoff and initial climb segment of flight.
Approximately 7.0 percent of the accidents occur during the climb portion. Only about 4.5 percent occur during cruise.
About 19.5 percent occurs during descent and initial approach. But 41.4 percent of the accidents occur during final approach and landing.
Takeoff, initial climb, final approach, and landing represent only about 6.0 percent of the total flight time of a given flight. But as these numbers point out, that 6.0 percent of a flight's total time can be deadly.
Ground proximity warning systems and the newer terrain awareness and warning systems using GPS have the potential to reduce CFIT accidents on takeoffs and landings. These systems provide one more tool for pilots to use to increase their safety margin when operating close to terrain and obstacles.
However, every pilot must know the limitations of his or her database and what objects are included in the database.
In order to address these accidents, it was necessary to define the envelope of safe flight so that excursions outside could be signalled to the pilot. Because the statistics indicate that the landing and take-off phases are the most exposed, rate of closure with the terrain must be measured – hence the use of RADALT in GPWS.To reduce the complexity of the algorithm to assess closure rates to the edge of the safe envelope, the solution is provided in six classic modes (to find out more about the modes read the manual or see a discussion of the practical application to helicopters between Nick Lappos and Helicomparitor on the S92 thread).
Having already made an impressive impact on the accident rate, and because GPS and terrain data bases were becoming available, it became possible to address the en-route accidents - in most cases caused by loss of situational awareness. Hence the introduction of the enhanced mode – i.e. EGPWS. This added synthetic vision displays, and additional algorithms to assess closure rates based on the GPS position and point of conflict in the terrain map in the digital data-base (the accuracy of which may vary in different parts of the world – the US being the most accurate). This accuracy is not usually an issue because it is IFR separation that has to be maintained (1,000ft or 2,000ft in mountainous areas).
Because of this potential lack of accuracy; as stated by ‘running-in’, EGPWS “...is not designed as an IFR low level (below Safety Level) navigation system” nor should it be used as one.
When flying VFR, it is important that the helicopter remains in an environment where the ‘available visual cues’ exceed the ‘required visual cues’. This is not easy to quantify because it will be dependent both upon the handling qualities of the helicopter and skill of the pilot. VFR limits are set to provide the average pilot in the average helicopter with safe margins of operation (and is the reason why there are increments for pilots in training and those with less experience).
It has been known for some time that, as the available visual cues decrease, the pilots attention is inexorably drawn outside the cockpit and handling becomes progressively more difficult until loss of control occurs. This can happen slowly: if the visibility decreases as the flight progresses (or as the light cues reduce at night); or quickly if the helicopter inadvertently enters cloud (or the light cues disappear at night e.g. when cross country or operating in mountains). At the point where control is lost, it is extremely difficult for an experienced test pilot, and almost impossible for an inexperienced pilot, to come back into the cockpit and transition to instruments in an un-stabilised platform.
Obviously a stabilised platform will provide the handling qualities that permit flight in a much reduced visual cue environment; however, adequate handling qualities result not from the basic certification process but from compliance with Appendix B of Parts 27/29. A helicopter that has been certificated for flight in IMC will already have stability and all of the required equipment for IFR flight.
When there are insufficient visual cues to permit visual contact flying, there is no substitute for flight on instruments; but, flight on instruments requires planning, and compliance with the Instrument Flight Rules - which are provided to ensure obstacle clearance. There is no in-between state; either flight can be achieved with visual contact or it cannot; if it cannot, flight should be conducted in accordance with the Instrument Flight Rules.
The use of Synthetic Visual Systems (SVS) are no panacea for scud running or flight without visual contact (adequate light sources) at night; control cannot be maintained by using an SVS as the sole means of attitude orientation. Where they perhaps have their use is where they are provided as part of the instrument suite to provide situational awareness (as an additional safety benefit). That benefit is also limited to those areas where the terrain data-base adequately describes the obstacles; for offshore operations, SVS is of limited use, as its ‘quality’ picture does not adequately describe all obstacles that may be in the area of operation. What would improve the efficacy of the unit would be the addition of an enhanced visual function provided by real time sensors (such as a LiDAR).
EGPWS does not provide solutions for other than IFR flight; it is, as stated by ‘running in’, “...a situational awareness tool and an alerting and warning device”. When used in its correct context – i.e. IFR onshore flying in accordance with the Instrument Flying Rules, it is extremely effective.
Loss of control accidents can be addressed by improving the handling qualities of light helicopters – particularly for flight at night. If that is not possible then addressing the safety culture of pilots and operators – i.e. the HF solution – is the only way. My preference would be to address the handling qualities; compensating for human nature is much too difficult and is rarely sucesssful.
Could EGPWS in helicopters be improved? Well some of us think it could. How? By revisiting the classic mode algorithms and comparing them against the helicopter flight envelopes that can be distilled from the Megabytes of data that has been collected as part of the FDM/HOMP program. A distinction might have to be made between offshore (which as was previously stated is somewhat less complex) and onshore operations.
If this is done we might be able to provide a protection envelope that could have prevented a number of offshore accidents that resulted from flight outside the safe envelope. The ones that immediately come to mind are: the S76 accidents in the GOM and the Dutch section of the North Sea; the AS365 accidents in the Bombay High and Morecombe Bay (although the results of that accident are still awaited), Cormorant Alpha and several accidents in the Far East.
However, that is just my view.
Jim
Last edited by JimL; 30th Jun 2008 at 15:31.
Join Date: Sep 2001
Location: In the Haven of Peace
Age: 79
Posts: 600
Received 0 Likes
on
0 Posts
As usual Jim, an informed and informative post. I think anjouan summed up much of what I have found to be the case with EGPWS so far and Honeywell will definitely have to do something along the lines you have suggested if it is to have any real use or relevance in helicopters operating offshore.
There is no in-between state; either flight can be achieved with visual contact or it cannot; if it cannot, flight should be conducted in accordance with the Instrument Flight Rules.
I certainlyt wish the FAA and the US EMS industry would grasp that concept!
The most intense flying with the greatest risk is the flying that is done VFR in IMC Conditions.
