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Originally Posted by Act700
That’s why local ATC make a point to verbalise it, ManaAdaSystem!
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How do you local guys fly this ILS approach in minima weather? VS and if the GS suddenly dips down, you continue i VS? Or do you go around? 1 in 10 approaches end up with a go around? This is an accident waiting to happen. |
Originally Posted by Capn Bloggs
(Post 10331077)
Are you serious?? TURN IT OFF and FIX IT! This industry is dangerous enough as it is without known and accepted traps like this. Rediculous.
It's quite likely the 747 lining up for departure is causing the GS distortion. So you can't just "fix it", you need to adjust ATC procedures. (I'm not sure about different antenna types though i believe there are types that are less prone to distortion) See the following pictures looking at the 20th October at 22:13 UTC https://cimg5.ibsrv.net/gimg/pprune....624015ec49.png https://cimg4.ibsrv.net/gimg/pprune....1ea34f5587.png |
Possible, but I think this would have been looked into a long time ago. ILS systems are flight tested on a regular basis. Don’t know the source for the NOTAM, pilot reports or test results? |
1) Move the holding point before the U-turn, and introduce "Line up behind" [ICAO standard since long ago].
I was actually about to say a bit in defence of the crew, but seeing the graph by wiedehofp, now I am glad I did not. |
This is not an inherent problem with the GS equipment at VHHH. It is due to departing aircraft on the ground proceeding into the ILS Critical Area and interfering with the GS signal.
Clearly well-known to the authorities, since they have carefully painted an ILS HOLD line on taxiway K, abeam the GS antenna (see top image, post #43, and the airport diagram). And not uncommon at other airports. If the ceiling is below 800' and/or visibility is below 2 miles, and an aircraft is on the ILS inside the OM, ATC should not permit an aircraft (or other vehicles) to pass that hold line. because it is well-known that that can make the GS reception unreliable. However, on this day, the weather was well above those requirements, and ATC was not required to protect the GS signal. Therefore it is up to landing crews, well-informed by charts, NOTAMs, and ATC verbal warnings that the GS could be unreliable as departing aircraft interrupt it periodically in good weather, to use common sense and not be automation-dependent. Use the ILS for guidance if you wish, but be prepared for a honking great 747F to pass in front of the antenna and foul up the GS signal. Be ready to hit the VS HOLD button, or cancel the A/P altogether and hand-fly the rest of the approach manually and visually. |
Originally Posted by pattern_is_full
(Post 10331205)
This is not an inherent problem with the GS equipment at VHHH. It is due to departing aircraft on the ground proceeding into the ILS Critical Area and interfering with the GS signal.
Clearly well-known to the authorities, since they have carefully painted an ILS HOLD line on taxiway K, abeam the GS antenna (see top image, post #43, and the airport diagram). And not uncommon at other airports. If the ceiling is below 800' and/or visibility is below 2 miles, and an aircraft is on the ILS inside the OM, ATC should not permit an aircraft (or other vehicles) to pass that hold line. because it is well-known that that can make the GS reception unreliable. However, on this day, the weather was well above those requirements, and ATC was not required to protect the GS signal. Therefore it is up to landing crews, well-informed by charts, NOTAMs, and ATC verbal warnings that the GS could be unreliable as departing aircraft interrupt it periodically in good weather, to use common sense and not be automation-dependent. Use the ILS for guidance if you wish, but be prepared for a honking great 747F to pass in front of the antenna and foul up the GS signal. Be ready to hit the VS HOLD button, or cancel the A/P altogether and hand-fly the rest of the approach manually and visually. Then they will fix it. |
Originally Posted by pattern_is_full
(Post 10331205)
Therefore it is up to landing crews, well-informed by charts, NOTAMs, and ATC verbal warnings that the GS could be unreliable as departing aircraft interrupt it periodically in good weather, to use common sense and not be automation-dependent. Use the ILS for guidance if you wish, but be prepared for a honking great 747F to pass in front of the antenna and foul up the GS signal. Be ready to hit the VS HOLD button, or cancel the A/P altogether and hand-fly the rest of the approach manually and visually.
If as you said , this only applies in good weather, then say " G/S unserviceable "during that period. You protect yourself as ATC and it is clear for all crews. Because if as ManaAdaSystem prediction above do materialize one day , the guys that authorized this will most likely end up somewhere very unpleasant. . |
1. HK runs single runway ops overnight into the early morning. You can expect to land on 07R on certain days. 2. If the weather is good, ATC will not protect the ILS sensitive areas. 3. There is no need to fly an ILS in good weather, other approaches are available. 4. The GS fluctuations are reported via a Digital ATIS....you can get this outside of VHF coverage unlike other airports...so you can spend the 2-15hrs of your flight inbound coming up with a plan...there is no surprise here. 5. If you still choose to fly an ILS, you have accepted the risk, best have a plan if you encounter an aircraft upset event. Your decision. 6. If anything needs fixing in HK, it is the extremely inefficient airspace....particularly for arrivals from the north....and there is a 3rd runway under construction. 7. GS fluctuations during single runways ops in the late night period in VMC is a minor issue easily managed by experienced crew....ie don't fly the ILS! |
Indeed, if the instructions above are too hard to follow, then maybe flying isn't for you and you should consider another career choice.
It's not that bloody difficult snowflakes. |
We have holding points right in the beam and I've never had a duck-dive on final. Something cockeyed here...
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Originally Posted by Capn Bloggs
(Post 10331486)
We have holding points right in the beam and I've never had a duck-dive on final. Something cockeyed here...
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Does the fluctuation, in anyone's opinion, explain what we see on the profile as recorded on FR24? I experienced some G/S fluctuations at SVO for the very same reason of GP antenna shielding, but the overall effect was very different.
The second approach, just starting the final descent https://cimg5.ibsrv.net/gimg/pprune....973133b109.png Same position but on the first approach. Already well below profile, -2000 fpm and keeps descending https://cimg6.ibsrv.net/gimg/pprune....acbe12550d.png First approach, 5 miles out: 400 ft AFE and still -2000 fpm https://cimg3.ibsrv.net/gimg/pprune....3790d5ce7d.png And the correction is … creepy. https://cimg7.ibsrv.net/gimg/pprune....28fb6ca142.jpg |
Originally Posted by ManaAdaSystem
(Post 10331232)
It’s OK then. Until an aircraft nosedives into the ground. Then they will fix it. |
Fluctuating ILS glidepath signals are not uncommon. Usually always caused by large lumps of metal (ie aircraft on the ground) moving between you and the transmitter. I’ve seen it at VHHH, KLAX & YSSY. In all cases it has been in VMC and ATC therefore are not required to protect the ILS signals. Pilots are expected to use airmanship and commonsense. Call me old fashioned, but when it has happened to me I (shock, horror) disconnected the autopilot, looked out the window and hand flew a visual approach. |
GS fluctuating.
A wise man (Murphy?)once said , “ If something can go wrong , it will” . Knowing that there’s a deficiency in the system and “hoping” the end user will be able to hack it is OK in some industries but not in aviation IMHO. As boeing have recently found out with their MCAS , don’t make a hole in the cheese and cover it up with tape , someone’s gonna find a way to line up the holes 😳😳 masalama👍👍 |
Originally Posted by masalama
(Post 10331744)
A wise man (Murphy?)once said , “ If something can go wrong , it will” . Knowing that there’s a deficiency in the system and “hoping” the end user will be able to hack it is OK in some industries but not in aviation IMHO. As boeing have recently found out with their MCAS , don’t make a hole in the cheese and cover it up with tape , someone’s gonna find a way to line up the holes 😳😳 masalama👍👍 https://cimg6.ibsrv.net/gimg/pprune....79d209b765.jpg |
Originally Posted by nike
(Post 10331406)
1. HK runs single runway ops overnight into the early morning. You can expect to land on 07R on certain days. 2. If the weather is good, ATC will not protect the ILS sensitive areas. 3. There is no need to fly an ILS in good weather, other approaches are available. 4. The GS fluctuations are reported via a Digital ATIS....you can get this outside of VHF coverage unlike other airports...so you can spend the 2-15hrs of your flight inbound coming up with a plan...there is no surprise here. 5. If you still choose to fly an ILS, you have accepted the risk, best have a plan if you encounter an aircraft upset event. Your decision. 6. If anything needs fixing in HK, it is the extremely inefficient airspace....particularly for arrivals from the north....and there is a 3rd runway under construction. 7. GS fluctuations during single runways ops in the late night period in VMC is a minor issue easily managed by experienced crew....ie don't fly the ILS! Glide slope blanking by aircraft taking the runway is common. As is LOC fluctuations as a plane clears the runway. This isn't new. Are those sink rates and altitudes correct? 2,600 FPM at 1350'? 1,900 FPM at 525'? Who's minded the store? If the ILS signal, or autopilot, gets twitchy it's taken out of the loop ASAP. |
Originally Posted by nike
(Post 10331406)
7. GS fluctuations during single runways ops in the late night period in VMC is a minor issue easily managed by experienced crew....ie don't fly the ILS! |
It can't be "fixed" if it is a taxiing airplane blocking the GS transmitter during good weather |
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