Max Glideslope Angle for Autoland
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Max Glideslope Angle for Autoland
It says 3.25 degrees for the aircraft I fly. But there is one approach that we do where the Jeppesen chart says the GS angle is 3.2° but the FMC says it is 3.3 degrees. Which is the restricting number.
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Denti you would be correct had the chart been published at 3.25 degree.
FMC can only display one decimal and chart publishes two. It's then a rounding error and the FMC displays 3.3 degrees.
However it appeared to m the question is he other way around this case...
Seems like a possible incorrect coding and should be reported to NavData provider for verification.
Next time you fly, temporarily select airfield again and runway with these details, verify that you posted this info correct (capture it on camera) then if need be send to Operations for verification.
Alternatively, post the image here so other's can assist in finding cause for your concerns (unofficially of course)
FMC can only display one decimal and chart publishes two. It's then a rounding error and the FMC displays 3.3 degrees.
However it appeared to m the question is he other way around this case...
Jeppesen chart says the GS angle is 3.2° but the FMC says it is 3.3 degrees
Next time you fly, temporarily select airfield again and runway with these details, verify that you posted this info correct (capture it on camera) then if need be send to Operations for verification.
Alternatively, post the image here so other's can assist in finding cause for your concerns (unofficially of course)
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If you supply the airport and runway info i'll check my LIDO and can crosscheck next time i fly (which isn't all that often since my secondary job takes up too much time). There are sometimes differences between chart suppliers about stuff like that as well.
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JammedStab I think an uploaded image would benefit those in the know, but it certainly seems to be an incorrect coding in the FMC which should be brought to the attention of Flight Operations if found to be the case.
An uploaded image should show the database coded angle and approach type selected
An uploaded image should show the database coded angle and approach type selected
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As the promulgated GP is 3.2 then this is the actual ILS Glidepath so it can be flown within the 3.25 maximum limit for autoland.
However when conducting a LOC approach the "calculated" Path will be as per FMC, thus 3.31 will be flown.
However when conducting a LOC approach the "calculated" Path will be as per FMC, thus 3.31 will be flown.
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RWY 15 ILS Interesting to note:
ILS 15 3.20° TCH 58
VGSI 3.20° TCH 75 (?!?!)
ILS 15 3.20° TCH 58
VGSI 3.20° TCH 75 (?!?!)
VGSI and ILS glidepath not coincident
The certification regulations might assume a maximum of 3.5 deg, but I cannot find a reference. Also 3.5 deg may the margin which a manufacturer has to show as being safe via development simulation, whereas the AFM value probably matches that demonstrated by flight tests.
An ‘ultimate’ limit depends on the aircraft type – aerodynamics, the flight guidance control laws, and the means of establishing a GS beam. RAE flight tests demonstrated 6 deg autoland with a BAC 111 and 5.5 deg with a HS748, flying MLS glidepaths.
An ‘ultimate’ limit depends on the aircraft type – aerodynamics, the flight guidance control laws, and the means of establishing a GS beam. RAE flight tests demonstrated 6 deg autoland with a BAC 111 and 5.5 deg with a HS748, flying MLS glidepaths.
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Jammed, while you can use autoland on RWY 15, it is not really set up for that.
As OK noted, depending on your brand and number of sig digits avail, results may vary. The FMS will always round up, never down.
I cant look it up right now, but there are some pretty good geoidal ref differences up there, so this will contribute to differences as well, depending on your brands use of the ellipsoid.
As OK noted, depending on your brand and number of sig digits avail, results may vary. The FMS will always round up, never down.
I cant look it up right now, but there are some pretty good geoidal ref differences up there, so this will contribute to differences as well, depending on your brands use of the ellipsoid.
RWY 15 ILS Interesting to note:
ILS 15 3.20° TCH 58
VGSI 3.20° TCH 75 (?!?!)
ILS 15 3.20° TCH 58
VGSI 3.20° TCH 75 (?!?!)
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I think it's odd that Jammed Stab has thus far refused to reveal what equipment he's on beyond "the aircraft I fly", despite being asked more than once (at least twice just by me). I certainly don't think he'll tell us what box he uses.
Why might someone be reticent about something so seemingly innocent?
Why might someone be reticent about something so seemingly innocent?
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Your are flying an ILS approach not a FMC RNAV approach . So the glide slope displayed on your FMC is irrelevant , as you will be flying a glide . The autopilot / FD is coupled to the ILS frequency , not to the FMC database.
The limiting factor is the offical document like AIP, jeppesen ...
The limiting factor is the offical document like AIP, jeppesen ...
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Back to the original question regarding what ILS angle can be flown, it is safe to say the one published is the one promulgated by the equipment, thus can be flown at the promulgated angle of 3.20.
The FMC coded angle is NOT used for the ILS as the G/S and LOC signal are followed, thus the check for angle would only be 'required' when conducting a VNAV approach. In case of a NPA, where the angle disagrees in FMC from published, DO NOT USE VNAV but use V/S.
The FMC coded angle is NOT used for the ILS as the G/S and LOC signal are followed, thus the check for angle would only be 'required' when conducting a VNAV approach. In case of a NPA, where the angle disagrees in FMC from published, DO NOT USE VNAV but use V/S.
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OK,
Quite a bit appears to be in transition right now. The more that the ac use RNAV, LPV, and RNP approach procedures, the more these sorts of issues will come to the forefront.
The geoidal differences in the FMS, baro-vnav temp issues, and others will need to be addressed.
In working with several FMS systems, the associated coding, and the programming, there are significant differences, many of which, are now being realized.
With tailored procedures, the FMS rounding has always been a significant issue.
Quite a bit appears to be in transition right now. The more that the ac use RNAV, LPV, and RNP approach procedures, the more these sorts of issues will come to the forefront.
The geoidal differences in the FMS, baro-vnav temp issues, and others will need to be addressed.
In working with several FMS systems, the associated coding, and the programming, there are significant differences, many of which, are now being realized.
With tailored procedures, the FMS rounding has always been a significant issue.
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Standard Honeywell Boeing FMC.