Visual Approaches
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Visual Approaches
After having a look at the AIP definition of Visual Approach and the requirements, someone has pointed out that it may not be as clear cut (or in reality as convoluted) as one expects.
THe definition or requirements say (AIP 1.1 -21 Para 11.5 and 1.5-9 Para 1.14)
For IFR, by day /night within 30nm of the Aerodrome
....
...
Tracking, by day within 5nm of the Aerodrome
or night withn the circling area or within 5nm (7nm ILS) of the aerodrome aligned with RWY C/L etc , or within 10nm (14nm RWY 16L/34L) of the Aerodrome etc...
(I undertsnad this to be based on the surveys of the approach areas..)
The AIP Definition of Aerodrome is (AIP gen 2.2-1)
A defined area of land or water (including any buildings, installations and equipment) intended to be used either wholly or in part for the arrival, departure and movement of aircraft.
So my question therefore is (a) where do we find the dimensions of the aerodromes we operate into to apply these distances
(b)from experience most people use the distances based on RWY threshold. Whilst this would be conservative - is using the RWY threshold really suitable (legally) for using the 5nm/7nm/10nm
THe only reason i ask, is that there are some pedantic so & so's out there, who apply the rules as they interpret them, not necessarily (and i dont necessarily know either) as they are intended.
THe definition or requirements say (AIP 1.1 -21 Para 11.5 and 1.5-9 Para 1.14)
For IFR, by day /night within 30nm of the Aerodrome
....
...
Tracking, by day within 5nm of the Aerodrome
or night withn the circling area or within 5nm (7nm ILS) of the aerodrome aligned with RWY C/L etc , or within 10nm (14nm RWY 16L/34L) of the Aerodrome etc...
(I undertsnad this to be based on the surveys of the approach areas..)
The AIP Definition of Aerodrome is (AIP gen 2.2-1)
A defined area of land or water (including any buildings, installations and equipment) intended to be used either wholly or in part for the arrival, departure and movement of aircraft.
So my question therefore is (a) where do we find the dimensions of the aerodromes we operate into to apply these distances
(b)from experience most people use the distances based on RWY threshold. Whilst this would be conservative - is using the RWY threshold really suitable (legally) for using the 5nm/7nm/10nm
THe only reason i ask, is that there are some pedantic so & so's out there, who apply the rules as they interpret them, not necessarily (and i dont necessarily know either) as they are intended.
Well Loo, in 30 years of aviation, I have not come across anyone pedantic enough to bring up that one!
Now back to the Sunday papers with you, and stay away from those AIPs for a while.
Now back to the Sunday papers with you, and stay away from those AIPs for a while.
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First time i heard about it was yesterday from a mate, i agree pedantic.....but it is an interesting issue....sometimes it helps to be prepared and have some return ammuntion when you have to fly with a pedantic person.
Other times it's just nice to try to figure out the real meaning.
Especially when you hear about people being failed on checks because they used PAPI distances (7nm) on an ILS surveyed RWY (Perth rwy 03) yet they are failed because the use of the ILS is not yet approved.
Other times it's just nice to try to figure out the real meaning.
Especially when you hear about people being failed on checks because they used PAPI distances (7nm) on an ILS surveyed RWY (Perth rwy 03) yet they are failed because the use of the ILS is not yet approved.
blueloo It is VERY unlikely that the reason you give is the reason that they failed!
Answer (a) DAP Plates but not really required.
Answer (b) Use the ARP.
blueloo Can I suggest that you apply some perspective here and try to apprecite what the "rule" is trying to achieve. This will usually but not always
provide some insight in to the requirement and more importantly how to apply it in operations.
Answer (a) DAP Plates but not really required.
Answer (b) Use the ARP.
blueloo Can I suggest that you apply some perspective here and try to apprecite what the "rule" is trying to achieve. This will usually but not always
provide some insight in to the requirement and more importantly how to apply it in operations.
I agree with Icarus.
I believe Distance within aerodrome is based on the ARP (not VOR/DME).
However distance of circling area (based on threshold is a hard one).
To play it safe, it I say, if we are within the circling area based on the ARP, then we are within the circling area based on the threshold (just in case someone wants to be pedantic).
I believe Distance within aerodrome is based on the ARP (not VOR/DME).
However distance of circling area (based on threshold is a hard one).
To play it safe, it I say, if we are within the circling area based on the ARP, then we are within the circling area based on the threshold (just in case someone wants to be pedantic).
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I am not sure that it is the ARP. More likely these distances would have to be based at least on Threshold (aside from the circling area reference which is based on this)
For example - Sydney 34l - the furthest point of the aerodrome is essentially the threshold (other than the extra bit of grass out to the break water). The aerodrome reference point is around 2 km away!
For example - Sydney 34l - the furthest point of the aerodrome is essentially the threshold (other than the extra bit of grass out to the break water). The aerodrome reference point is around 2 km away!
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Put yourself in 'that pedantic' person's position. How could they measure you were 7.1nm instead of 7.0nm? By DME? There's your answer. By GPS? Tell it to go to YABC and there's your answer. Mark 1 eyeball? I doubt it. And I agree, you would not fail on that alone.
I still believe distances (apart from circling area) are based on the Aerodrome Reference Point (ARP).
Take a look at some definitions.
In the AIP, the definition for ARP is :
For those who use Jeppesen's, take a look at "Introduction page 2".
To me this is a bit like the Centre of Gravity, where we assume the entire weight of the aeroplane acts through, even though the weight acts through it all the way from the nose to the tail.
The perimeter of an aerodrome may be spread out several miles from the ARP but I believe the ARP is used the same as the aircraft C of G. (assumed to act/be at one point)
Take a look at some definitions.
In the AIP, the definition for ARP is :
The designated geographical location of the aerodrome
ARP = A point on the airport designated as the official airport location
The perimeter of an aerodrome may be spread out several miles from the ARP but I believe the ARP is used the same as the aircraft C of G. (assumed to act/be at one point)
Why go any further then the actual definition of an aerodrome itself as in the AIP.
"Aerodrome: A defined area of land or water (including any buildings, installations and equipment) intended to be used either wholly or in part for the arrival, departure and movement of aircraft."
So I guess you are all right
I guess there is nothing wrong with using the threshold as this is an installation which will be used for part of the arrival... Mind you when is the ARP used for the arrival?!
lol
"Aerodrome: A defined area of land or water (including any buildings, installations and equipment) intended to be used either wholly or in part for the arrival, departure and movement of aircraft."
So I guess you are all right
I guess there is nothing wrong with using the threshold as this is an installation which will be used for part of the arrival... Mind you when is the ARP used for the arrival?!
lol
More Definitons
Lets look up some more in a :
dictionary
reference = act of refering
refer = To direct to a source for information
Therefore I interpret an "Aerodrome Reference Point" being to the "point" to which your refer to the exact location (latitude, longitude) of the aerodrome.
regitaekilthgiwt
You ask :
What is so funny here ? You don't believe the ARP is ever used ?
I use the ARP all the time, with the IFR GPS set up on the ARP (or am I doing something wrong now).
For example, I quite often use the ARP at night to make a visual approach.
The requirements being -
- established within 5nm of aerodrome
- on runway centreline
- not below slope
etc...
dictionary
reference = act of refering
refer = To direct to a source for information
Therefore I interpret an "Aerodrome Reference Point" being to the "point" to which your refer to the exact location (latitude, longitude) of the aerodrome.
regitaekilthgiwt
You ask :
Mind you when is the ARP used for the arrival?! lol
I use the ARP all the time, with the IFR GPS set up on the ARP (or am I doing something wrong now).
For example, I quite often use the ARP at night to make a visual approach.
The requirements being -
- established within 5nm of aerodrome
- on runway centreline
- not below slope
etc...
Moderate, Modest & Mild.
Answer to Q(a) - A Jeppessen chart of the aerodrome concerned will display the ARP. If you can't find a Jepp. contact the Dept of Transport (Aviation section), or the local council for the area where the airport is located. They will provide you with a map indicating where the ARP is located.
Answer to Q(b) - The fact that "most people use the distances based on RWY threshold" does not make it correct, and it is NOT correct.
Circling distances are based on the Aerodrome Reference Point, as are those used for prescribing aerodrome limitations (such as noise abatement procedures), and for the defining of each airports boundaries.
Answer to Q(b) - The fact that "most people use the distances based on RWY threshold" does not make it correct, and it is NOT correct.
Circling distances are based on the Aerodrome Reference Point, as are those used for prescribing aerodrome limitations (such as noise abatement procedures), and for the defining of each airports boundaries.
Sorry Kap.
Circling areas are definitely based on the runway threshold NOT the ARP - OLD Criteria charts excluded.
AIP ENR 1.5.1.7.3 - Note 3
Circling areas are definitely based on the runway threshold NOT the ARP - OLD Criteria charts excluded.
The circling area is determined by drawing an arc centred on the threshold of each useable runway and joining these arcs by tangent
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Agree with DA.
For Jepp Terminal 3.16.1 paragraph a. subparagraph (4) and paragraph b. subparagraph (4), "within the circling area" the definition of circling areas from paragraph 3.13.3 NOTE 3 is used, as per DirectAnywhere's post.
As for the rest of para 3.16.1, every other limiting distance for visual procedures into an aerodrome uses the phrase "Within x NM of that aerodrome".
When the AIP wants to talk about a distance from the threshold, it says so. Here it does not. When the AIP talks about an area defined by distances from thresholds, that is circling areas, it says so. Here it does not. When the AIP talks about distance from the aerodrome boundary, it says so. Again, here it does not.
So where "is" the aerodrome? The aerodrome "is at" the ARP.
So "Within 30NM/5NM/7NM/10NM/14NM of that aerodrome" is within that distance of the ARP.
For Jepp Terminal 3.16.1 paragraph a. subparagraph (4) and paragraph b. subparagraph (4), "within the circling area" the definition of circling areas from paragraph 3.13.3 NOTE 3 is used, as per DirectAnywhere's post.
As for the rest of para 3.16.1, every other limiting distance for visual procedures into an aerodrome uses the phrase "Within x NM of that aerodrome".
When the AIP wants to talk about a distance from the threshold, it says so. Here it does not. When the AIP talks about an area defined by distances from thresholds, that is circling areas, it says so. Here it does not. When the AIP talks about distance from the aerodrome boundary, it says so. Again, here it does not.
So where "is" the aerodrome? The aerodrome "is at" the ARP.
So "Within 30NM/5NM/7NM/10NM/14NM of that aerodrome" is within that distance of the ARP.
Moderate, Modest & Mild.
With reference to an Instrument approach, followed by a circling approach to a specific runway, I agree with you, Direct Anywhere.
I took blueloo's Q & A in the context of a VFR pilot making a Visual Approach.
Jeppessen notes that there there are 2 possibilities for defining the ARP (depending on the type of approach) - one is when the ARP is "Off runway" Center of cross positioned at exact location. In this case a "CIRCLE-TO-LAND" chart (followed by an instrument approach) uses the ARP which is non-runway specific.
The other is "Located on runway centerline. Arrow points to exact location" In this case, the circling minima specifies which runway it applies to.
Cheers.
I took blueloo's Q & A in the context of a VFR pilot making a Visual Approach.
Jeppessen notes that there there are 2 possibilities for defining the ARP (depending on the type of approach) - one is when the ARP is "Off runway" Center of cross positioned at exact location. In this case a "CIRCLE-TO-LAND" chart (followed by an instrument approach) uses the ARP which is non-runway specific.
The other is "Located on runway centerline. Arrow points to exact location" In this case, the circling minima specifies which runway it applies to.
Cheers.
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Just to keep the thread going a bit longer - a question for those REALLY pedantic people...........
- Are the distances based on slant range or distance over the ground from directly underneath the aircrafts present position???
- Are the distances based on slant range or distance over the ground from directly underneath the aircrafts present position???
Crash & Burn
You ask :
Slant error does not apply to a GPS derived distance (or I don't believe it does - as its not measuring a radio signal on a slant angle the way the DME does).
But lets look at this slant error anyway (just in case you are using a DME to determine your distance).
At 5 DME, at 1500', your actual distance from the DME will be 4.99nm !!
At 30 DME, at 9000', your actual distance from the DME will be 29.96nm !!
As you can see, the slant error is negligible, as its less than 0.1nm.
At 5 DME, the error os 0.01 nm !! Can any DME read the distance to 0.01 nm ?? I never seen one. Is the average DME accurate to 0.1 or 0.01 nm !!
At 250 knots on descent, it will only take to 1.5 seconds to fly this 0.1nm.
Its worth taking note of the fact the the DME measured slant distance will actually put you closer to the aerodrome than the DME reads.
For example, DME reads 30 DME, you are actually at 29.96 nm.
So if anyone wants to be pedantic, you can just reassure them of the fact that you are (0.1 nm at worst) closer then you think you are.
You ask :
Lets imagine your aircaft is 70m long, and the DME is measured in the nose but you want to ensure that the entire aeroplane (tail) is contained within the required distance.
Well 70m works out to be 0.038 nm !!
So if you want to be pedantic, you can now delay your descent for a visual approach by 0.04nm (or 0.1nm to be safe).
If you are still doing 250 knots on descent, it will take you 0.55 seconds to fly the length the aeroplane.
So if you want to really pedantic, just delay your descent by 0.1nm or 1 second just to keep you safe.
- Are the distances based on slant range or distance over the ground from directly underneath the aircrafts present position???
But lets look at this slant error anyway (just in case you are using a DME to determine your distance).
At 5 DME, at 1500', your actual distance from the DME will be 4.99nm !!
At 30 DME, at 9000', your actual distance from the DME will be 29.96nm !!
As you can see, the slant error is negligible, as its less than 0.1nm.
At 5 DME, the error os 0.01 nm !! Can any DME read the distance to 0.01 nm ?? I never seen one. Is the average DME accurate to 0.1 or 0.01 nm !!
At 250 knots on descent, it will only take to 1.5 seconds to fly this 0.1nm.
Its worth taking note of the fact the the DME measured slant distance will actually put you closer to the aerodrome than the DME reads.
For example, DME reads 30 DME, you are actually at 29.96 nm.
So if anyone wants to be pedantic, you can just reassure them of the fact that you are (0.1 nm at worst) closer then you think you are.
You ask :
another very valid question - which part of the aircraft is it measured from ?!?!?!
Well 70m works out to be 0.038 nm !!
So if you want to be pedantic, you can now delay your descent for a visual approach by 0.04nm (or 0.1nm to be safe).
If you are still doing 250 knots on descent, it will take you 0.55 seconds to fly the length the aeroplane.
So if you want to really pedantic, just delay your descent by 0.1nm or 1 second just to keep you safe.
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Thanks for going to all that trouble John - I feel much better now knowing that effectively the DME slant error cancels out the aircraft length error. I can now descend with confidence!
One less thing to get busted for!
(And yes I am also of the belief that the GPS is not showing slant range but ground range.)
Cheers
C & B !
One less thing to get busted for!
(And yes I am also of the belief that the GPS is not showing slant range but ground range.)
Cheers
C & B !
Don't get too relaxed just yet.
The GPS is a little'dodgey' for determining the descent (visual approach), full of errors. For example; satellite clock error 0.5m, satellite ephemeris error 0.5m, atmospheric propagation error 4.0m
, instrument/receiver error 1.0m and finally satellite geometry error but I don't want to get started on GDOP,TDOP,PDOP,VDOP and HDOP it's getting too late
.
Just wanted to warn you guys for planning your descents especially on Checks be careful and have your story ready when the Checky starts to give you a hard time in the de-brief .
The GPS is a little'dodgey' for determining the descent (visual approach), full of errors. For example; satellite clock error 0.5m, satellite ephemeris error 0.5m, atmospheric propagation error 4.0m
, instrument/receiver error 1.0m and finally satellite geometry error but I don't want to get started on GDOP,TDOP,PDOP,VDOP and HDOP it's getting too late .Just wanted to warn you guys for planning your descents especially on Checks be careful and have your story ready when the Checky starts to give you a hard time in the de-brief
.