PAPI vs Glidepath

[Michael Moe 497]

Hi again . I was flying the ENTC ILS18 with G/S and LOC captured and the warning sound for the Glideslope. Normally i would be to low as shown in the PFD by the magenta diamond on top 5 degree, but the PAPI had 4 white which showed i was to high . The PAPI was correct. I was to high.

Thanks Michael Moe 

[Michael Moe 497]

2 minutes ago, Michael Moe said:

Hi again . I was flying the ENTC ILS18 with G/S and LOC captured and the warning sound for the Glideslope. Normally i would be to low as shown in the PFD by the magenta diamond on top 5 degree, but the PAPI had 4 white which showed i was to high . The PAPI was correct. I was to high.

Thanks Michael Moe 

Maybe the reverse( false)ils happened ?

Michael Moe

Edited November 17, 2022 by Michael Moe

[SAS443 1,749]

1 hour ago, Michael Moe said:

The PAPI was correct. I was to high.

Do you cross-reference the published altitudes along the glideslope with your altimeter?

For example ENTC ILS 18,
At 4.5DME your altimeter should indicate roughly 1934 ft.

Keep in mind G/S angle at Tromso is 4.00 degrees. Estimated rate of descents are published for various groundspeeds on the charts and You can easily cross reference by displaying the FPV donut in the 737NG. It should rest at -4 degree angle obviously.

Edited November 17, 2022 by SAS443

[Michael Moe 497]

6 minutes ago, SAS443 said:

Do you cross-reference the published altitudes along the glideslope with your altimeter?

For example ENTC ILS 18,
At 4.5DME your altimeter should indicate roughly 1934 ft.

Keep in mind G/S angle at Tromso is 4.00 degrees. Estimared rate of descents are published for various groundspeeds on the charts and You can easily cross reference by displaying the FPV donut in the 737NG. It should rest at -4 degree angle obviously.

Thanks gonna check it out 

Michael Moe

[Fiorentoni 4,483]

2 hours ago, SAS443 said:

LLZ antennas for an ILS approach are located on the opposing end of the runway (hence the ability for an autopilot to track it during roll-out). G/S antennas roughly abeam the aiming point markers (usually co-located with DME and the PAPI installation).

Yes but is that also the case in MSFS, that‘s the question. I usually fly visual from 500-1000 ft, but if I don‘t, the GS mostly keeps me much too high IIRC, which led me to my conclusion, that it‘s tracking the LLZ antennas in front of the runway (opposite end) instead of the GS antennas.
I can‘t find any other explanation, I mean how else can a straight beam lead to the wrong location if not for the emitter being located at the wrong place?

[Fiorentoni 4,483]

Double post. Please delete.

Edited November 17, 2022 by Fiorentoni

[BerndB 349]

Only in very rare or few situations the Glidepath of an ILS match with the guidance by PAPI. These are two complete different stories. If you do an ILS approach, which is the usual most common approach for commercial flying, you must ignore the PAPI anyway, beacause only the ILS Glidepath is the reference you must rely on. PAPI is reference is for visual approaches, which is a different  approach type itself.   

Having that said, i. ex. while an ILS approach you allowed to refer to the Glidepath information of the ILS ONLY until you reach the Minimum if it´s an CAT I approach. At this point, or shortly after, usually at "hundred above" latest, you take over and diconnect the autopilot. Then this short last sequence of the approach is flown manually where you refer to visual informations like the centerline, touchdown zone markings, threshold marking or shifted treshholds etc. and may be PAPI if it´s applicable, which is usually not, becasue you should focus the touchdown marker on the runway at that short moment. 

Edited November 17, 2022 by BerndB

[SAS443 1,749]

1 hour ago, BerndB said:

Only in very rare or few situations the Glidepath of an ILS match with the guidance by PAPI. These are two complete different stories.

However both EASA (CS-ADR-DSN) and ICAO (ANNEX 14 and/or doc 9157 part 4)  has extensive design guidelines for harmonising PAPI and G/S indication to pilots, irrespective of EAH (eye-to-antenna heights)

ICAO ANNEX 14 vol 1 ch 5:

Quote

Where a PAPI or APAPI is installed on a runway equipped with an ILS and/or MLS, the distance D1 shall be calculated to provide the optimum compatibility between the visual and non-visual aids for the range of eye-to-antenna heights of the aeroplanes regularly using the runway. The distance shall be equal to that between the threshold and the effective origin of the ILS glide path or MLS minimum glide path, as appropriate, plus a correction factor for the variation of eye-to-antenna heights of the aeroplanes concerned

This usually has a consequence of moving the PAPI slightly to upwind side. I work at a large intl. Airport and our PAPIs are some 25 odd meters behind the GP antennae installations for this purpose. The ambition is to have the G/S and PAPI indications coincide to the pilots as much as practically possible while not be incompliant with wheel over threshold height minimums for larger acft.

On a sidenote: The aiming point markers are governed by PAPI placement, and not ILS GP location (ref EASA CS ADR-DSN.L.540)

Edited November 17, 2022 by SAS443

[Michael Moe 497]

I might think i just had the A318 episode in France AFR 7512.

Reversed ILS 90/150HZ episode

Michael Moe

[z06z33 781]

It's extremely common for the Glide path and the Papi not to line up. I would say about 90% of the approaches I shoot at the airlines have Non Coincident Glide paths