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NicholasB

Glideslope intercept very violent

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Hi gang,I did see a thread about this issue in the forum some time back, however, after scouring the forum tonight i could not find it.As procedure states, I always engage the LOC on the MCP prior to engaging the APP function, and always from a lower altitude than the glideslop intercept altitude (flying into the glideslope and not over it) After acheiving LOC and still at a lower level than the glideslope, I then engage APP.Eventualy the aircraft does settle into a nice and balanced Fianl approach profile, however, the initial intercept is very violent with the aircraft unatrualy pitching up and climbing, then sharply pitching down again once established. The engines also react just as violently while trying to compensate for these sharp changes in pitch. This seems to happen regardles of my speed and flap setting at the time and is not an isolated incident. Happens everytime.By no means is this a fatal flaw as the aircraft does always settle into a smooth final, but if there is a quick fix available or an upcoming service pack for the 747X, I do sincerely hope that this glideslope capture modeling issue will be addressed.How many opther people are experiencing this?, and if so have you found any suitable work around? or am i just missing something entirely?Thanks and looking forward to some feedback!NicholasB

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The only time I've experienced this is not due to GS intercept but wind gusts. Otherwise, the approach segment is always very smooth.If you're sure that the problem is not weather related, please post a screen shot during such an incident. Maybe we can figure it out.This behavior is not the norm.


Dan Downs KCRP

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It is not weather related. I have it everytime I intercept the GS. I would not call it violent though. The nose does pitch up once the intercept is close and engines do come up to speed (more so than the FS9 version ever did) until the intercept at which point everything settles again. If you are low and intercept close to the runway the descent is not really smooth as it takes a bit to stablise.Never noticed this in the FS9 version but is noticable in the FSX version.John Veldthuishttp://www.virtualpilots.org/signatures/vpa475.png


John Veldthuis

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Hi dan,here are two pics, trying to capture the sensation i described above. Unfortunately the pics realy dont express what i mean too well, but i hope it helps.Cheers,NicholasB

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I'm only an armchair pilot, but at first appearance it seems your intercept angle is excessive.My understanding is, and I can always be corrected, the ILS intercept should be about 30 degrees.From the screen dumps you appear to be well into the intercept, still 45 degrees to go.It may be worthwhile trying to intercept the ILS at a more acute angle.CheersGraham McAllister


Cheers, Graham McAllister - Melbourne, Australia

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Hi Graham,Thanks for your post and I do see your point. Nevertheless, when I do approach the Glideslope intercept point even from a literal straight in front course, I still get these sharp pitch fluctuations at the intercept point.A good example for anyone who wants to do some testing is the RNAV TRANSITION RWY25 L/R FOR FRANKFURT EDDF. If you follow transition and profile GPS/FMC as published you will be aligned with the runway heading several NM before glideslope capture. As you mention excessivie bank will certainly reflect pitch changes, but i still dont think it is related to the glideslope capture issue Im experiencing.for anyone who wants to do download the chart for the above, here is the link.http://www.edff-fir.de/files/charts/eddf/E...ITION_RWY25.pdfThanks for the suggestion. well noted too.Regards,NicholasB

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The CRT I'm using at work doesn't show much detail, but it looks like your speed is >200 kts. The VSI doesn't seem to be excessive. You're turning to final course above glideslope.I recommend turning to final course about 3 nm beyond glideslope intercept (although it's not always possible this is normally what ATC will provide as a minimum), and the speed/flaps being one notch above final approach configuration. In other words, if you're going to landing with flaps 30 then have flaps 25 and the corresponding speed when you are lining up on final.Maybe your high speed and being right on the GS when turning to the LOC is causing the pitch response. The FAF is about 5 nm and 1800 agl from touchdown, try to be established on final in a stable descent at the FAF. Even if things are rushed, this is a requirement to continue the approach at 1000 agl.EDIT: If you are shooting a RNAV then the discussion on GS is moot. I always try to set up an RNAV approach such that my descent throughout the approach is constant, this means being higher than the published at-or-above altitudes for all but the FAF fixes. Use 318 ft vertical per nm as a guide for 3 deg descents.


Dan Downs KCRP

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Thanks for the link Harry!I know this is by no means a fatal flaw in the 747X, it just niggles me a bit when you feel like you have completed a perfect flight and then on final you get this very unattractive glideslope intercept.After all, approach and landing is the climax for us simmers right?Judging by the other threads and the responses to my messages, I do realy hope that the groundswell regarding this issue will be looked into by the powers that be. I do beleive that at some point in time there will be a hot fix available and or a service pack. At that time lets hope this glideslope capture modeling can be smoothed out a bit.I look forward to what the experts may say about the screenshots you posted.Cheers,NicholasB

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Maybe I'm mistaken here, but it appears to me that in your two screen shots you haven't yet intercepted the LOC as the color indicator under the PFD (horizontal guide) is still way to the right. I don't engage the APP until the craft has captured the LOC and is on approach but still below the GS as would show on the indicator to the right (vertical guide)of the PFD.But maybe I'm wrong.Jim

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Hi NicholasJim is correct in his observations. Your magenta GS indicator is already below the line, and you have not yet captured the localiser, so I wouild guess that when the app captures, then it will be a violent occurence. I have got used to using fsnavigator for data, as when I put my mouse over the end of the runway in that programme it tells me the glideslope capture altitude. For example at my favorite airport it tells me that the glideslop is at 1900 ft at 5nm, so I try and hit the localiser at 10-12 nm away at say 2500-3000 ft and the magenta GS indicator is "hollow diamond" at the top when I intercept the localiser, then when the diamond indicator comes down the screen as a solid diamond i am well established on the localiser, and at 1 mark above GS capture i drop the gear and I am fully established by then. and it is a very smooth occurence. If you tell me the airport you were landing on in those pics then I will look up the data for you and tell you the gs capture altitude for that airport.best regardsJohn Calleja


John Calleja

Picture6.jpg

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Hi John,that would be kansai International airport Japan RJBBthanks. When i made these pics i did programe the FMC for ILS approach runway 6R. Altitude restraints in the FMC for the ILS arrival was 4500 feet for the first waypoint in the arrival. forgot the name of this way point but you will find it right next to the TOMO VOR on FS nav.I agree with you and Jim on the above, But on times i give my self plenty of space and already have LOC with severl NM untill capture i still have the same pitch sensations.Thanks,NicholasBIll try to repost some pics as soon as i can following the correct procedures!

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Guest Just747-400

Dear Nicholas,Don

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