Weird display of glide slop in attitude indicator
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Dear JF team,
I spotted a strange behavior on the attitude indicator while flying ILS, To be specific, on the glideslope indicator;
80% of the time, when flying ILS, intercepting from BELOW (standard). The glide indication will show the opposite; showing it self as if I was above the glide (officially telling me that I am too high). When reaching the interception point, glide indication will start moving from bottom to top until getting intercept by GLIDE mode and being maintain in the middle of the slope indicator by the autopilot.
Initially I thought it was a Fokker 28 "old school thing".
Then I realize sometime (20%) I get the classic display too; when flying ILS, intercepting from BELOW (standard). The glide indication will show above. Reaching interception point, glide indication will start moving from top to bottom until getting intercept by GLIDE mode...
Is it something normal? It feels weird, especially for hand flying as you have to do opposite correction to what the glide indicator is showing you (example; glide showing above, you have to descent faster... can of unnatural). Even worst for descent anticipation purpose...
In the mean time, I spotted a regular slight deviation to glideslope, I will try to find out how much exactly, but regarding charts and DME checkpoint on slope, I am always a little bit lower than what expected. I will say around 300ft-400ft deviation. Then close I get to the threshold, better it becomes.
Alex
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@AlexEtz This isn't something I persaonlly recall seeing in the F28. Could you confirm if you are have the GNS530 enabled or disabled when this issue occurs?
If you do have it enabled, has the GNS530 been programmed for an ILS/RNAV approach? I'm wondering if there may be a certain situation where if you have an RNAV approach programmed in the GNS530 and an ILS frequency tuned into the analogue NAV radios then there might be some sort of conflict.
Would you be able to provide any examples of the flights/airports where you have seen this issue? We can then try and replicate this on our end.
Mark - Just Flight
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@Mark Hey Mark, thanks for your answer. I will try to screenshot this next time and share it here. If I recall well, it happens to me in EGFF ILS 30 for sure, I had to go around because the glide wasn't behaving normally. All GNS options are disable for me.
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I've just tried an ILS approach onto runway 30 at EGFF and the glideslope was indicating correctly for me with both GS AUTO and GS MAN modes.
If this issue occurs again, could you try switching the NAV radio that the frequency is turned into, and maybe switch between GS AUTO and GS MAN Flight Director modes? Just to see if that corrects itself?
Mark - Just Flight
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Hey Mark, I tried to understand where this error of display was coming from, I think I have some clues, but I still have to investigate... it might come from GS AUTO FD mod, and VHF TUNING before ILS receiving, I will come back to you if I find anything more precise.
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Hey, I made an other occurrence with this display issue. This time the weather even made the aircraft go a little bit bellow the glide and you can see that the display is showing the opposite.
It really seems to be a very random issue... sometimes it occurs, sometimes not.
https://youtu.be/NxoX7zCqwIY?si=KI1YY0LaQ_H4VgT0
weather in LFQQ that day: LFQQ 191030Z AUTO 28015KT 9999 SCT019/// BKN025/// OVC038/// ///CB 11/08 Q1013 TEMPO 32015G25KT 3000 SHRA BKN012 BKN020TCU
