Circling below circling MDA at night.
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Did the chieftain driver in young decsend below 1000ft agl on downwind? and continue a steady descent on base? Genuinely interested in the answer to that.
Your point is well made centaurus and I have to admit I have always believed that if it is a circling area and you are in a normally spaced circuit then you can descend on a normal profile. I am still not quite convinced that this is not the case as I had thought they would have made it a 'no circling' area if you couldn't descend like that.
I am sure that what you have written from the books is spot on but can you provide an example of an airfield where turning base at 1000agl and making a normal 3 degree descent to the threshold within a circling area results in busting obstacle clearance. If you can then I am going to have to rethink my techniques! Cheers.
Your point is well made centaurus and I have to admit I have always believed that if it is a circling area and you are in a normally spaced circuit then you can descend on a normal profile. I am still not quite convinced that this is not the case as I had thought they would have made it a 'no circling' area if you couldn't descend like that.
I am sure that what you have written from the books is spot on but can you provide an example of an airfield where turning base at 1000agl and making a normal 3 degree descent to the threshold within a circling area results in busting obstacle clearance. If you can then I am going to have to rethink my techniques! Cheers.
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Don't know the answer to the chiefain Qn.
As a general rule I maintain MDA until turning onto finals, I have found this gives me the required obstacle clearance, and the profile I need to make good a normal approach and landing.
Haven't been to a strip yet that in doing this has caused my profile to be too steep.
As a general rule I maintain MDA until turning onto finals, I have found this gives me the required obstacle clearance, and the profile I need to make good a normal approach and landing.
Haven't been to a strip yet that in doing this has caused my profile to be too steep.
I can't understand why this still causes so much grief.
By day if you can see the obstacles, you can descend to the OCA. If not maintain the MDA until you can descend using normal rates to position the aircraft for landing, be it downwind, base or final.
At night, maintain the MDA until you can descend using normal rates to position the aircraft for landing, be it downwind base or final.
In other words for a CAT B prop aircraft, MDA = 1500' AGL, start descent on downwind to position aircraft turning base at an appropriate altitude depending on the aircraft position.
MDA = 700' AGL, start descent mid base.
MDA = 400' AGL maintain until established on final.
Whilst it is a visual manoeuvre, it should be flown with close reference to the altimeter.
I think you've obviously thought a lot about your answer Centaurus, and not wishing to belittle you, but I think your fundamental premise is wrong.
As a hypothetical, how would you safely circle a CAT A aircraft at an aerodrome with an MDA of say 1500' AGL if you were not able to descend below the MDA until aligned with the landing runway as you say you would do? In this case an average RoD of nearly 1000'/min is required assuming a GS of only 60 kts - assuming you're aligned with the landing runwy right at 1.6Nm. Pretty hard to do, and do safely, I'm sure you would agree.
One thing this thread does prove however, is how ineffectually the recommendations of the then BASI following the Young accident, have been implemented by CASA. I believe I'm correct, as obviously does Centaurus!! It is apparent that this issue needs to be revisited and the publications clarified further, and further training material published, to remove any doubt as to the correct way to perform this critical manoeuvre.
By day if you can see the obstacles, you can descend to the OCA. If not maintain the MDA until you can descend using normal rates to position the aircraft for landing, be it downwind, base or final.
At night, maintain the MDA until you can descend using normal rates to position the aircraft for landing, be it downwind base or final.
In other words for a CAT B prop aircraft, MDA = 1500' AGL, start descent on downwind to position aircraft turning base at an appropriate altitude depending on the aircraft position.
MDA = 700' AGL, start descent mid base.
MDA = 400' AGL maintain until established on final.
Whilst it is a visual manoeuvre, it should be flown with close reference to the altimeter.
I think you've obviously thought a lot about your answer Centaurus, and not wishing to belittle you, but I think your fundamental premise is wrong.
As a hypothetical, how would you safely circle a CAT A aircraft at an aerodrome with an MDA of say 1500' AGL if you were not able to descend below the MDA until aligned with the landing runway as you say you would do? In this case an average RoD of nearly 1000'/min is required assuming a GS of only 60 kts - assuming you're aligned with the landing runwy right at 1.6Nm. Pretty hard to do, and do safely, I'm sure you would agree.
One thing this thread does prove however, is how ineffectually the recommendations of the then BASI following the Young accident, have been implemented by CASA. I believe I'm correct, as obviously does Centaurus!! It is apparent that this issue needs to be revisited and the publications clarified further, and further training material published, to remove any doubt as to the correct way to perform this critical manoeuvre.
Last edited by DirectAnywhere; 26th Apr 2005 at 04:12.
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Direct Anywhere' , I am of the same opinion but if there are examples of airports where doing this will kill you then I will re-think it. I don't think there will be though because the approach planners will have made them 'no-circlining areas.
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Several thoughts ..
(a) the critical obstruction for circling is not published but is available if you track down the right people .. however, one needs to know a bit more about the general set of obstacles in the circling area as there may be only the one significant obstacle .. or there may be a number, of which one is the critical concern for the published limits. Getting this data is done routinely by those of us who play with performance scheduling work as it is useful for OEI recovery planning in the published takeoff procedure for a particular runway. Normal scale topos are pretty useless and relying on the IAL spot heights is foolhardy .. keeping in mind that they may not be exhaustive and reflect ground rather than clearance heights.
(b) local knowledge is critical for low vis circling approaches. If you know the runway well and can positively locate yourself throughout the exercise, clearly the situation is much more comfortable than if you have never been to the place before.
(c) many pilots on their first trip to an aerodrome in other than day VMC conditions will ALWAYS shoot a published runway letdown (where available) to remove a bunch of worries from the immediate flightpath management considerations.
(d) having frightened myself in earlier years in that, after arriving at an aerodrome for the first time in the dark and then looking at it in the harsh reality of the next day's light .. I will choose not to wing a circling approach unless I can work on the basis of descending on final .... conservative perhaps but comforting .. CBR is a good example and I never really liked running down the approach to 17 in the dark and seeing the lights above us to the side ...
(a) the critical obstruction for circling is not published but is available if you track down the right people .. however, one needs to know a bit more about the general set of obstacles in the circling area as there may be only the one significant obstacle .. or there may be a number, of which one is the critical concern for the published limits. Getting this data is done routinely by those of us who play with performance scheduling work as it is useful for OEI recovery planning in the published takeoff procedure for a particular runway. Normal scale topos are pretty useless and relying on the IAL spot heights is foolhardy .. keeping in mind that they may not be exhaustive and reflect ground rather than clearance heights.
(b) local knowledge is critical for low vis circling approaches. If you know the runway well and can positively locate yourself throughout the exercise, clearly the situation is much more comfortable than if you have never been to the place before.
(c) many pilots on their first trip to an aerodrome in other than day VMC conditions will ALWAYS shoot a published runway letdown (where available) to remove a bunch of worries from the immediate flightpath management considerations.
(d) having frightened myself in earlier years in that, after arriving at an aerodrome for the first time in the dark and then looking at it in the harsh reality of the next day's light .. I will choose not to wing a circling approach unless I can work on the basis of descending on final .... conservative perhaps but comforting .. CBR is a good example and I never really liked running down the approach to 17 in the dark and seeing the lights above us to the side ...
Last edited by john_tullamarine; 23rd Apr 2005 at 03:36.
Pertinent extracts from the ATSB report on the Piper Chieftain accident at Young NSW,which killed all on board:
Paragraph 2.3 (f):
"At night in the absence of extensive ground lighting or other means of seeing the ground or water, the investigating team considered that descent below the minimim circling altitude is not practicable until the aircraft is aligned with the runway to be used."
Paragraph 3.2: "The aircraft descended below the minimum circling altitude without adequate monitoring of obstacle clearance by the crew, and the visual cues available to the flight crew were insufficient as a sole source of height judgement."
"The flight test at night replicating the flight of VH-NDU suggests that a pilot could not visually assess aircraft height over obstacles along the flight path of the aircraft during a right downwind or turn on to base. The crew of the test aircraft reported they were unable to ensure adequate visual reference along the flight path during downwind and turn on to base."
I recommend that readers examine the various approach plates for Mudgee, NSW as an example of a high circling MDA. In this cae it is 1975 ft above aerodrome level for a Category C aircraft and 1485 ft AAL for category A and B. Circling to the west of the aerodrome is permitted but if the visibility is at the circling minima in either case, it would be almost impossible to land due to the high angle and rate of descent required if descent below the MDA is delayed until established on final approach.
Therefore an early descent starting at downwind and continuing on base would be needed in order to maintain a normal descent profile. There is no guidance on the various approach charts at Mudgee to indicate the critical obstacle therefore it's position in the circling area is unknown except to the chart designer.
The dangers involved with descending below the circling MDA in order to meet a desired descent profile is graphically described in the earlier quotes by ATSB in relation to the Chieftain fatal accident at night at Young, NSW.
Mudgee is therefore a good example of where a circling approach at night is hazardous and should not be attempted in visibility at the circling minima. Mareeba in North Queensland is another example where in this case the VOR approach plate reveals a circling minima of 1700 ft above aerodrome elevation with 2.4 kms vis limit for category A and B. Potentially deadly at night.
From all this emerges one stark fact of life and that is you should never contemplate going below the circling MDA at night until you are aligned with the landing runway. If you cannot land safely because the final approach is too steep - then stiff! Divert to your alternate.
Paragraph 2.3 (f):
"At night in the absence of extensive ground lighting or other means of seeing the ground or water, the investigating team considered that descent below the minimim circling altitude is not practicable until the aircraft is aligned with the runway to be used."
Paragraph 3.2: "The aircraft descended below the minimum circling altitude without adequate monitoring of obstacle clearance by the crew, and the visual cues available to the flight crew were insufficient as a sole source of height judgement."
"The flight test at night replicating the flight of VH-NDU suggests that a pilot could not visually assess aircraft height over obstacles along the flight path of the aircraft during a right downwind or turn on to base. The crew of the test aircraft reported they were unable to ensure adequate visual reference along the flight path during downwind and turn on to base."
I recommend that readers examine the various approach plates for Mudgee, NSW as an example of a high circling MDA. In this cae it is 1975 ft above aerodrome level for a Category C aircraft and 1485 ft AAL for category A and B. Circling to the west of the aerodrome is permitted but if the visibility is at the circling minima in either case, it would be almost impossible to land due to the high angle and rate of descent required if descent below the MDA is delayed until established on final approach.
Therefore an early descent starting at downwind and continuing on base would be needed in order to maintain a normal descent profile. There is no guidance on the various approach charts at Mudgee to indicate the critical obstacle therefore it's position in the circling area is unknown except to the chart designer.
The dangers involved with descending below the circling MDA in order to meet a desired descent profile is graphically described in the earlier quotes by ATSB in relation to the Chieftain fatal accident at night at Young, NSW.
Mudgee is therefore a good example of where a circling approach at night is hazardous and should not be attempted in visibility at the circling minima. Mareeba in North Queensland is another example where in this case the VOR approach plate reveals a circling minima of 1700 ft above aerodrome elevation with 2.4 kms vis limit for category A and B. Potentially deadly at night.
From all this emerges one stark fact of life and that is you should never contemplate going below the circling MDA at night until you are aligned with the landing runway. If you cannot land safely because the final approach is too steep - then stiff! Divert to your alternate.
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Thanks for that centaurus. I see that the investigation chaps recomoend staying up at mda until finals but I still suspect that that pilot went below a normal circuit profile. Same with Mudgee, if you started your descent from 1500ft half way along downwind and kept it at 3 degrees..monitoring ie not below 1000ft on downwind and established on finals by 600ft...would you bust obs clearance? thats the only question really and I don't believe the planners would leave it as a circling area if you did.
Cheers
Cheers
Just a couple of issues with your post regarding the Young accident Centaurus.
The aircraft initially impacted trees, while on a right base for the aerodrome, at a straight line distance from the threshold of 2215 metres. These trees were at a height of only 275 feet above the threshold elevation which indicates the aircraft was grossly low for a normal approach at the time - obviously. It indicates that little regard was given to flying a normal approach path. Had the aircraft been at a normal altitude at this time with roughly 2Nm to travel to the threshold, it would have been some 800' above threshold elevation, or 500+ feet above the terrain, and there would have been no issue.
Also, in this case, the PIC, once visual, deliberately descended to 2000', some 400' below the circling minima and some 750' AAL to maintain "visual". This was not at a point in the circuit where the aircraft would intercept a normal approach path - hence the subsequent change in the documents.
Not forgetting also the Captain's RMI and HSI were U/S forcing the Captain to scan across to the FO's instruments. It is considered "likely" that the final descent to 275' AAL was unintended and may have gone unnoticed. This cannot be defended against if both crew miss it.
The PIC was also not qualified for the route to be flown and had not been checked in to Young.
Based on your comment
then you should not be at the airport in the first place! It should be determined preflight that this approach will be too steep to allow a safe descent when the aircraft is aligned with the runway and the aircraft should not be flown there at night.
Try telling that to any Chief Pilot when the AIP gives adequate guidance to safely conduct a circling approach, when adequate consideration is given to the terrain within the circling area.
John_Tullamarine's advice is good advice. I would not want to turn up somewhere for the first time at night, in IMC, and attempt to circle without having a good idea of the terrain below me. That said, I am happy, having been there before, and given adequate consideration to the terrain, to descend in accordance with the AIP.
Subsequent amendments to the AIP have cleared up many of the issues identified during this report. I still believe the 300/400' is not relevant at night with respect to visual clearance, provided an adequate study of the terrain has been made - and no that doesn't merely include reference to the aerodrome diagram and approach plate. Out of interest, isn't it about time the chart provider gave information on those obstacles or is it merely another case of bureacratic arse covering at the expense of flight safety?
The aircraft initially impacted trees, while on a right base for the aerodrome, at a straight line distance from the threshold of 2215 metres. These trees were at a height of only 275 feet above the threshold elevation which indicates the aircraft was grossly low for a normal approach at the time - obviously. It indicates that little regard was given to flying a normal approach path. Had the aircraft been at a normal altitude at this time with roughly 2Nm to travel to the threshold, it would have been some 800' above threshold elevation, or 500+ feet above the terrain, and there would have been no issue.
Also, in this case, the PIC, once visual, deliberately descended to 2000', some 400' below the circling minima and some 750' AAL to maintain "visual". This was not at a point in the circuit where the aircraft would intercept a normal approach path - hence the subsequent change in the documents.
Not forgetting also the Captain's RMI and HSI were U/S forcing the Captain to scan across to the FO's instruments. It is considered "likely" that the final descent to 275' AAL was unintended and may have gone unnoticed. This cannot be defended against if both crew miss it.
The PIC was also not qualified for the route to be flown and had not been checked in to Young.
Based on your comment
If you cannot land safely because the final approach is too steep - then stiff!
Try telling that to any Chief Pilot when the AIP gives adequate guidance to safely conduct a circling approach, when adequate consideration is given to the terrain within the circling area.
John_Tullamarine's advice is good advice. I would not want to turn up somewhere for the first time at night, in IMC, and attempt to circle without having a good idea of the terrain below me. That said, I am happy, having been there before, and given adequate consideration to the terrain, to descend in accordance with the AIP.
Subsequent amendments to the AIP have cleared up many of the issues identified during this report. I still believe the 300/400' is not relevant at night with respect to visual clearance, provided an adequate study of the terrain has been made - and no that doesn't merely include reference to the aerodrome diagram and approach plate. Out of interest, isn't it about time the chart provider gave information on those obstacles or is it merely another case of bureacratic arse covering at the expense of flight safety?
Last edited by DirectAnywhere; 23rd Apr 2005 at 23:10.
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Thanks 'Direct Anywhere', that clears up what happened at YOUNG for me. Can someone with access to Mudgee plates answer my second question which was
"if you started your descent from 1500ftagl half way along downwind and kept it at 3 degrees..monitoring ie not below 1000ftagl on downwind and established on finals by 600ft...would you bust obs clearance?"
With respect to the young accident, does anyone think that working out AMSL heights to be at turning base and turning finals, prior to being there, is important? It is something I like to do. Even though the calculation is simple I find it reassuring to have done it with no pressure so that when the workload is high I have faith in those figures.
Is it possible that in the YOUNG accident, with a high workload situation that SA was lost with respect to height agl because of the height above sea level?
Cheers
"if you started your descent from 1500ftagl half way along downwind and kept it at 3 degrees..monitoring ie not below 1000ftagl on downwind and established on finals by 600ft...would you bust obs clearance?"
With respect to the young accident, does anyone think that working out AMSL heights to be at turning base and turning finals, prior to being there, is important? It is something I like to do. Even though the calculation is simple I find it reassuring to have done it with no pressure so that when the workload is high I have faith in those figures.
Is it possible that in the YOUNG accident, with a high workload situation that SA was lost with respect to height agl because of the height above sea level?
Cheers
How many times does one have to repeat the mantra before it sinks in. If you cannot see the terrain below you because it is too dark (read the ATSB report on the Young accident) then never go below the MDA at night until you are aligned with the runway. Even ATSB says that.
The so called profile descent discussed in both AIP and in previous posts has absolutely nothing to do with obstacle clearance on a night circling MDA. Once you decide to fly into the No Mans Land below MDA at night, then you put yourself and your passengers at significant risk of running into a rock sticking up from the terrain you cannot see. This is especially relevant at some overseas airports where the circling area is much smaller in design than Australian airports.
The profile is an aircraft type thing, and the chart designer couldn't care less if the pilot chooses to fly inverted on downwind and base during the whole procedure - or indeed whether the pilot calculated descent "profile" flown is a three degrees, six degrees, or even a helicopter ninety degree descent vertically. It will never guarantee you obstacle clearance - only the MDA will do that for you which is why the chart designer publishes it for all to see. The old adage: "There's none as blind as those who will not see", comes to mind here.
Having said that, a vertical helicopter descent from the circling MDA situated directly above the landing threshold ie a 90 degree profile, is probably the safest way of descending below the circling minima on a dark and stormy night. But then helicopters frighten the hell out of me
The so called profile descent discussed in both AIP and in previous posts has absolutely nothing to do with obstacle clearance on a night circling MDA. Once you decide to fly into the No Mans Land below MDA at night, then you put yourself and your passengers at significant risk of running into a rock sticking up from the terrain you cannot see. This is especially relevant at some overseas airports where the circling area is much smaller in design than Australian airports.
The profile is an aircraft type thing, and the chart designer couldn't care less if the pilot chooses to fly inverted on downwind and base during the whole procedure - or indeed whether the pilot calculated descent "profile" flown is a three degrees, six degrees, or even a helicopter ninety degree descent vertically. It will never guarantee you obstacle clearance - only the MDA will do that for you which is why the chart designer publishes it for all to see. The old adage: "There's none as blind as those who will not see", comes to mind here.
Having said that, a vertical helicopter descent from the circling MDA situated directly above the landing threshold ie a 90 degree profile, is probably the safest way of descending below the circling minima on a dark and stormy night. But then helicopters frighten the hell out of me
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I did my first 100 instructing hours at Mudgee (and quite a few more than that, later in my career), with many hours in the circuit at night. Having flown there so much by day and night, I was comfortable in establishing a normal circuit height on a close mid-downwind, with normal descent on base to setup a normal final approach.
That was before VASIS, but not before I was very familiar with the place. I wouldn't do the same thing on a first-up visit somewhere else, with similar challenges. There is simply no substitute for local knowledge for those black-hole approaches at night.
cjam... there are places here in PNG where the designated "no circling" area is only marginally worse than the area that's available for circling. Many of the places, where night operation is permitted, are complete black holes (ie no ground lights anywhere except the runway itself).
As part of the job that I've held for a total of 14 years so far, I design instrument approaches in PNG. I can tell you that there are many instances where the "critical obstacle" is only minimally higher than other obstacles, so it does not improve safety to simply identify that one obstacle. And it's impractical to identify all of the obstacles.
Here, perhaps even more than most places in Australia, local knowledge is everything. This is as true of day operations, when the weather is marginal, as it is of night operations in any weather conditions.
That was before VASIS, but not before I was very familiar with the place. I wouldn't do the same thing on a first-up visit somewhere else, with similar challenges. There is simply no substitute for local knowledge for those black-hole approaches at night.
cjam... there are places here in PNG where the designated "no circling" area is only marginally worse than the area that's available for circling. Many of the places, where night operation is permitted, are complete black holes (ie no ground lights anywhere except the runway itself).
As part of the job that I've held for a total of 14 years so far, I design instrument approaches in PNG. I can tell you that there are many instances where the "critical obstacle" is only minimally higher than other obstacles, so it does not improve safety to simply identify that one obstacle. And it's impractical to identify all of the obstacles.
Here, perhaps even more than most places in Australia, local knowledge is everything. This is as true of day operations, when the weather is marginal, as it is of night operations in any weather conditions.
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ok I'm getting the idea that some experienced pilots out there would be uncomfortable with my take on what is safe with regard descending below MDA within the circuit and on a normal profile. I am all for adjusting ones ideas and am contemplating refining my take on this.
That said, I would still like an answer to that Mudgee question even if it is just to confirm that I need to rethink my approach.
the question for all you folks with access to Mudgee maps and plates;
"if you started your descent from 1500ftagl half way along downwind and kept it at 3 degrees..monitoring ie not below 1000ftagl on downwind and established on finals by 600ft...would you bust obs clearance?"
Also, can anyone think of any airport (NZ or Aus) that has a circling area in which obs clearance would be busted by descending on a normal 3 degree profile, within a normal circuit .
Cheers
That said, I would still like an answer to that Mudgee question even if it is just to confirm that I need to rethink my approach.
the question for all you folks with access to Mudgee maps and plates;
"if you started your descent from 1500ftagl half way along downwind and kept it at 3 degrees..monitoring ie not below 1000ftagl on downwind and established on finals by 600ft...would you bust obs clearance?"
Also, can anyone think of any airport (NZ or Aus) that has a circling area in which obs clearance would be busted by descending on a normal 3 degree profile, within a normal circuit .
Cheers
Cjam,
Cairns, Ballera, Strahan, Ballina, Kununurra, Cobar, Coffs, Cooly, Learmonth, Brewarrina, Cooktown, Dysart, Paraburdoo, Barimunya, Wyndham, Bronzewing, Jundee, Argyle and Rottnest Island come to mind.
Some aerodromes like Wyndham require CASA approval to operate into at night, or dont permit normal night operations like Rottnest.
I just think circling at night is silly esp with the number of runways aligned approaches available.
Cairns, Ballera, Strahan, Ballina, Kununurra, Cobar, Coffs, Cooly, Learmonth, Brewarrina, Cooktown, Dysart, Paraburdoo, Barimunya, Wyndham, Bronzewing, Jundee, Argyle and Rottnest Island come to mind.
Some aerodromes like Wyndham require CASA approval to operate into at night, or dont permit normal night operations like Rottnest.
I just think circling at night is silly esp with the number of runways aligned approaches available.
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Ballina?
All circling is to the south (RH CCT RWY 06) with no significant obstacles and plenty of ground lighting; circling MDAs are 780'. Perhaps you are thinking either of somewhere else - or you too have witnessed the occasional Dash-8 and 737 do LH CCTs onto 06 in contrvention of ERSA (not to mention the direct entries onto base in the circuit by the Saabs)
All circling is to the south (RH CCT RWY 06) with no significant obstacles and plenty of ground lighting; circling MDAs are 780'. Perhaps you are thinking either of somewhere else - or you too have witnessed the occasional Dash-8 and 737 do LH CCTs onto 06 in contrvention of ERSA (not to mention the direct entries onto base in the circuit by the Saabs)
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swh,
I have been thinking about those runways and all the ones I have been to (three)are not answers to my question. I am starting to think that there are no airports where...
if you started your descent from 1500ftagl half way along downwind and kept it at 3 degrees..(monitoring ie not below 1000ftagl on downwind and established on finals by 600ft.).and you are in a normal circuit within a circling area, you would bust obs clearance.
I guess you missed the bit about being in a circling area or something swh, Please can someone give me an example with some figures ...how much do you bust obs clearance by? cheers
I have been thinking about those runways and all the ones I have been to (three)are not answers to my question. I am starting to think that there are no airports where...
if you started your descent from 1500ftagl half way along downwind and kept it at 3 degrees..(monitoring ie not below 1000ftagl on downwind and established on finals by 600ft.).and you are in a normal circuit within a circling area, you would bust obs clearance.
I guess you missed the bit about being in a circling area or something swh, Please can someone give me an example with some figures ...how much do you bust obs clearance by? cheers
Centaurus, I just think we're hoing to have to agree to disagree. You're still here, I'm still here so neither of us have hit any hills yet.
The BASI, it wasn't the ATSB in the days this report was written (1993), clearly advocated maintaing the MDA until aligned with final. That said, it's worth noting the significant amendments, in the ensuing 12 years, with respect to circling, to the then AIP DAP IAL and current AIP ENR.
These documents have not remained static over the last 12 years. It is my firm belief, that these amendments completely change the intent of these documents. The current documents simply do not allow an aircraft to be at 275' AAL on early base in IMC or at night. The old documents didn't either but were so poorly written it was a common misconception.
These poor people were the victims of serious organisational failures within the then CAA - that ultimately resulted in its breakup to form CASA and AsA, and Monarch. In additon poor maintenance and poor check and training standards were also identified.
I respect your view but we're going to have to agree to disagree.
SWH, Cairns has got a lot of big hills but so long as you remain inside the designated circling area - east of the field and north of Trinity Inlet, there's nothing to run into. I believe this is one of CJAMs and my main conjectures.
The BASI, it wasn't the ATSB in the days this report was written (1993), clearly advocated maintaing the MDA until aligned with final. That said, it's worth noting the significant amendments, in the ensuing 12 years, with respect to circling, to the then AIP DAP IAL and current AIP ENR.
These documents have not remained static over the last 12 years. It is my firm belief, that these amendments completely change the intent of these documents. The current documents simply do not allow an aircraft to be at 275' AAL on early base in IMC or at night. The old documents didn't either but were so poorly written it was a common misconception.
These poor people were the victims of serious organisational failures within the then CAA - that ultimately resulted in its breakup to form CASA and AsA, and Monarch. In additon poor maintenance and poor check and training standards were also identified.
I respect your view but we're going to have to agree to disagree.
SWH, Cairns has got a lot of big hills but so long as you remain inside the designated circling area - east of the field and north of Trinity Inlet, there's nothing to run into. I believe this is one of CJAMs and my main conjectures.
cjam,
Your question was "Also, can anyone think of any airport (NZ or Aus) that has a circling area in which obs clearance would be busted by descending on a normal 3 degree profile, within a normal circuit ."
I gave you an answer to that question, the airports I listed have circling areas, they also have obstacle clearance issues, the designated IFR circling area may not be permitted within the "normal circuit" of the aerodromes I previously listed.
If it didnt answer the question you wanted, could you pose the question differently to get the answer you are seeking.
Also can think of many "no-aid" aerodromes which also have a circling area which have a "normal circuit" which also have obstacle clearance issues.
Your question was "Also, can anyone think of any airport (NZ or Aus) that has a circling area in which obs clearance would be busted by descending on a normal 3 degree profile, within a normal circuit ."
I gave you an answer to that question, the airports I listed have circling areas, they also have obstacle clearance issues, the designated IFR circling area may not be permitted within the "normal circuit" of the aerodromes I previously listed.
If it didnt answer the question you wanted, could you pose the question differently to get the answer you are seeking.
Also can think of many "no-aid" aerodromes which also have a circling area which have a "normal circuit" which also have obstacle clearance issues.
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Please consult a topo!!!
This post seems to spark up enormous debate and the variation in opinion probably is evidence that the current AIP rules still lack enough guidance for some readers. Nonetheless – I have no gripes with the rules as they stand and believe I am safely conducting night circling approaches (when absolutely necessary) including descent below MDA prior to reaching final.
I posted a reply on page 2 of this thread (21st Apr 01:10). I think a couple of points from that reply could do with reiteration…
Centaurus:
Re: Your reply on this thread on 20th Apr 18:47 (page 2 of this thread). You asked:
Absolutely. AIP ENR 1.5 para 1.7.2 states "Before commencing an instrument approach, pilots should familiarise themselves with the location and altitude of obstacles in the circling area by studying an appropriate topographic map".
Based on this rule, your comments immediately following your question concern me a little:
In a later reply (22nd Apr 23:38, page 3 of this thread), you state:
Well – I would tend to agree if you are going to ignore the AIP rule of making reference to a topographic map as required by para 1.7.2 above. THIS RULE IS CRITICAL TO THE SAFE CONDUCT OF NIGHT CIRCLING APPROACHES.
If a topographic map of the airfield is available, the obstacles surrounding the airfield should never be known only to the approach designer.
The approach plate is an INSTRUMENT APPROACH plate designed to safely get you to the minima (hopefully) before the MAPP. From there, the pilot needs to have done some solid homework with a topo regarding the terrain before flying a night circling approach. No – I would not expect someone to do this airborne – this is a preflight preparation task. During the approach brief, the topo can be revisited briefly to refamiliarise oneself with the orientation gained during preflight preparation. Your method of maintaining MDA until on final, whilst seeming to be on the safe and conservative side of the rules, may in some cases lead you to require a high rate of descent on final after just flying over possibly flat and featureless terrain on downwind and base. Seems a bit silly and a less safe approach overall.
Then again – if during your preflight study of the topo you had identified an obstacle under the base turn flight path which would infringe your expected glidepath by more than 300’/400’, you might choose to modify your base turn position and/or your vertical profile (rate of descent) to maintain your 300’/400’ clearance until on final when you could then use a slightly increased rate of descent early on final. I have needed to plan and fly such a modified profile on several occasions, although granted I did have the help of obstruction lighting to help me identify the obstacles.
Sorry to harp on but I feel that the need to consult a topographic map has been largely neglected by you and others on this thread.
DirectAnywhere:
Re : Your reply on this thread on the 23rd Apr at 10:36
You mention that the 300’/400’ terrain clearance requirement is inapplicable to the night case.
ENR 1.5 para 1.7.3 d) "by night or day ...intercepts a position on the downwind, base or final leg of the landing traffic pattern, and, from this position, can complete a continuous descent to the landing threshold using rates of descent and flight manoeuvres which are normal for the aircraft type and, during this descent, maintains an obstacle clearance along the flight path not less than the minimum for the aircraft performance category until the aircraft is aligned with the landing runway "
In light of the fairly clear guidance above, I’m not sure where you’re coming from.
CJAM:
You wee requested responses from anyone regarding airfields at which a standard circuit will not work.
Canberra is a classic. Have a look at the VTC and the RW17 VOR plate. Although there is a no-circling restriction beyond 4nm west of Canberra (I think this may be based on Black Mountain Tower), a standard circuit can be flown in almost any aircraft type inside 4nm. Inside 4nm, however, there is some very significant terrain (Mount Ainslie and Mount Majura which is probably the limiting obstacle). The circling MDA for a Cat C aircraft to RW17 is 3530’AMSL on accurate QNH (about 140’ above a 1500’AGL circuit altitude for a jet). If a standard jet circuit is flown with descent just before the base turn point (MDA 1640’AGL), not only will the 400’ obstacle clearance requirement until on final be breached, but the aircraft will probably hit Mount Majura (highest marked elevation 3036’AMSL). Modifying the base turn ground track and glidepath (within circling area and aircraft limits) is required and results in an acceptable circuit. With some local knowledge and good obstruction lighting, I have done this at night but would strongly discourage it without adequate obstruction lighting. Obviously, a left hand circuit is preferable.
Is this what you’re after?
I am really interested to know if people think this topographic map awareness stuff is all hot air.
VI
I posted a reply on page 2 of this thread (21st Apr 01:10). I think a couple of points from that reply could do with reiteration…
Centaurus:
Re: Your reply on this thread on 20th Apr 18:47 (page 2 of this thread). You asked:
Once you leave the protected altitude which is the published circling MDA, am I right in saying you become responsible for your own terrain clearance?
Based on this rule, your comments immediately following your question concern me a little:
Have you got time to drag out a WAC or Military Survey chart to plot the position of the critical obstacle? Of course not.
Notwithstanding the provisions of the AIP with regard to intercepting a "normal" profile for the type of aircraft, in order to make a continuous descent to land from downwind, it should be clear that if this involves deliberately ignoring the MDA, the pilot does this at his (and his passengers), peril.
If a topographic map of the airfield is available, the obstacles surrounding the airfield should never be known only to the approach designer.
The approach plate is an INSTRUMENT APPROACH plate designed to safely get you to the minima (hopefully) before the MAPP. From there, the pilot needs to have done some solid homework with a topo regarding the terrain before flying a night circling approach. No – I would not expect someone to do this airborne – this is a preflight preparation task. During the approach brief, the topo can be revisited briefly to refamiliarise oneself with the orientation gained during preflight preparation. Your method of maintaining MDA until on final, whilst seeming to be on the safe and conservative side of the rules, may in some cases lead you to require a high rate of descent on final after just flying over possibly flat and featureless terrain on downwind and base. Seems a bit silly and a less safe approach overall.
Then again – if during your preflight study of the topo you had identified an obstacle under the base turn flight path which would infringe your expected glidepath by more than 300’/400’, you might choose to modify your base turn position and/or your vertical profile (rate of descent) to maintain your 300’/400’ clearance until on final when you could then use a slightly increased rate of descent early on final. I have needed to plan and fly such a modified profile on several occasions, although granted I did have the help of obstruction lighting to help me identify the obstacles.
Sorry to harp on but I feel that the need to consult a topographic map has been largely neglected by you and others on this thread.
DirectAnywhere:
Re : Your reply on this thread on the 23rd Apr at 10:36
You mention that the 300’/400’ terrain clearance requirement is inapplicable to the night case.
ENR 1.5 para 1.7.3 d) "by night or day ...intercepts a position on the downwind, base or final leg of the landing traffic pattern, and, from this position, can complete a continuous descent to the landing threshold using rates of descent and flight manoeuvres which are normal for the aircraft type and, during this descent, maintains an obstacle clearance along the flight path not less than the minimum for the aircraft performance category until the aircraft is aligned with the landing runway "
In light of the fairly clear guidance above, I’m not sure where you’re coming from.
CJAM:
You wee requested responses from anyone regarding airfields at which a standard circuit will not work.
Canberra is a classic. Have a look at the VTC and the RW17 VOR plate. Although there is a no-circling restriction beyond 4nm west of Canberra (I think this may be based on Black Mountain Tower), a standard circuit can be flown in almost any aircraft type inside 4nm. Inside 4nm, however, there is some very significant terrain (Mount Ainslie and Mount Majura which is probably the limiting obstacle). The circling MDA for a Cat C aircraft to RW17 is 3530’AMSL on accurate QNH (about 140’ above a 1500’AGL circuit altitude for a jet). If a standard jet circuit is flown with descent just before the base turn point (MDA 1640’AGL), not only will the 400’ obstacle clearance requirement until on final be breached, but the aircraft will probably hit Mount Majura (highest marked elevation 3036’AMSL). Modifying the base turn ground track and glidepath (within circling area and aircraft limits) is required and results in an acceptable circuit. With some local knowledge and good obstruction lighting, I have done this at night but would strongly discourage it without adequate obstruction lighting. Obviously, a left hand circuit is preferable.
Is this what you’re after?
I am really interested to know if people think this topographic map awareness stuff is all hot air.
VI