Glideslope callout on take off

[Christopher Low 5,368]

I have selected 23L as the departure runway, and 23R as the arrival runway. I am not sure why there is interference from 05L, but the flightplan takes me to final approach for 23R (and I am cleared to land on that runway).

[downscc 1,327]

2 hours ago, Christopher Low said:

I have selected 23L as the departure runway, and 23R as the arrival runway. I am not sure why there is interference from 05L, but the flightplan takes me to final approach for 23R (and I am cleared to land on that runway).

Most likely 05L uses same frequency as 23R, so yeah your solution is to click on the GS Inhibit button, lost track of it's exact label.  As I found and noted from the FCOM, the GPWS does not inhibit the GS warning so it's doing what it is supposed to do.

[Christopher Low 5,368]

Yes, the ILS frequency for 05L is the same as 23R (109.50). I do not recall it ever happening with the 737, but I need to try the 777 again to see if it happens with that aircraft.

[berts 97]

2 hours ago, Christopher Low said:

I have selected 23L as the departure runway, and 23R as the arrival runway. I am not sure why there is interference from 05L, but the flightplan takes me to final approach for 23R (and I am cleared to land on that runway).

Christopher,

What scenery are you using at EGCC? 

Looking at your image files and the answers to everyone's questions (including mine) it seems there is nothing obvious so far which will explain why you are getting a false Glideslope warning after takeoff at EGCC.  Before you Inhibit the EGPWS G/S as Dan has suggested, it might be worth your while eliminating as many variables as possible; for example by using the same runway for take off and landing and see what happens. 

I suggest you program the FMS so that you can complete a circuit on each Runway and in both directions (i.e. 23L for T/O and Landing, then 23R, 05L and 05R) and see what warnings, if any, you get. You will need to remember to manually tune the ILS prior to takeoff each time with the correct frequency and inbound course. Due to the higher terrain to the East of Manchester you might want to fly each circuit at 3,500ft QNH and use the A/P as if you were carrying out an autoland.  This will give you plenty of time to monitor the aircraft and watch for anything unusual - like your false G/S warning.

Bertie

 

[downscc 1,327]

1 hour ago, Christopher Low said:

Yes, the ILS frequency for 05L is the same as 23R (109.50). I do not recall it ever happening with the 737, but I need to try the 777 again to see if it happens with that aircraft.

Because the simulator will always select the nearest ILS, in this case when depart 23L the simulator (not PMDG) selects the 23R ILS components regardless of the fact that you have selected 05L.  So basically, the only way around this is to either inhibit GS aura or park the ILS frequency until you are on the downwind.

[berts 97]

29 minutes ago, downscc said:

Because the simulator will always select the nearest ILS, in this case when depart 23L the simulator (not PMDG) selects the 23R ILS components regardless of the fact that you have selected 05L.  So basically, the only way around this is to either inhibit GS aura or park the ILS frequency until you are on the downwind.

Dan,  it is not normal practice to inhibit the G/S on the B744 prior to takeoff and shoudn't be necessary to fix Christopher's problem at EGCC with FSX or P3D.  This applies irrespective of whether the Departure RWY ILS is auto or manually tuned in the FMS.  The only place I can recall where inhibiting the G/S for takeoff was routinely used for real was departing on RWY 13 at Kai Tak, where the RWY 31 ILS would be manually tuned and the LOC used for accurate track guidance until passing the TD VOR and the aircraft was well clear of the nearby terrain on HKG Island.  On some older aircraft (e.g. the B747/100 series but not the B744) this would also require the selection of a 'Backbeam' mode.

I have just flown a few circuits on 23R and 05L in the QOTS 744 and never got a G/S warning after takeoff.  If Christopher wants to fly circuits then I recommend he uses the same runway for takeoff and landing, manually tunes the correct ILS into the FMS and constructs a simple Route around the airfield to the FAF.  This should cure his false warnings - we hope!

Bertie 

[Qavion2 39]

I believe the key is found in the arming conditions for this mode. The aircraft must descend through 1000ft ra (with the gear down)

The GPWS computer probably monitors the changing altitudes and only arms this mode if the aircraft is seen to be descending through 1000'. Similarly, the altitude callouts need to be armed by the aircraft climbing above a certain height. This prevents nuisance height callouts during climb.

The maintenance manual checks for the G/S aural begin by simulating a starting altitude of 1500ra.

Reference 747-400 AMM 34-46-00-865-099-001 Section (i) Mode 5/Mode 6 Configuration Test.

Hope this helps.

 

(I don't know if this arming is modelled in QOTSII)

[Christopher Low 5,368]

Quote

What scenery are you using at EGCC?

The latest version of UK2000 Manchester Xtreme.

[Johannvr 3]

I have done a similar circuit at EGCC (UK2000 EGCC Extreme V2), departing 23L for ILS approach 23R and same here. At about 300ft the "glideslope" warning. On the PFD strangely the ILS Ident also IMM (for rwy05L) although rwy23R selected for approach. If I depart without an approach selected, problem solved, and (obviously) no "glideslope" warning. The system for some reason sense "below GS for rwy05L" as also indicated on the PFD. If I depart rwy23R for an ILS approach on rwy23R, then ILS Ident INN on the PFD and no "glideslope" warning.

I suspect this is a flightsim issue, FSX in my case.

[Christopher Low 5,368]

Quote

I suspect this is a flightsim issue, FSX in my case

I agree, and it is P3D v3.4 in my case.

I have seen other curious issues elsewhere with respect to ILS approaches. One such example would be FlyTampa EKCH Copenhagen Kastrup. I take off on runway 22R at that airport (with runway 22L selected for the approach and landing), but for some odd reason the FMC shows runway 22R as the selected approach. Most of the AI planes also try to land on runway 22R (even though landings are disabled on that runway). Strangely enough, I am fairly sure that I saw the selected runway on the FMC "switch" during the approach from 22R to 22L, but by then ATC was expecting me to land on 22R.....

I am going to experiment with a few things to see if I can "force" landings on 22L (even though this should happen automatically when landings on 22R are disabled). It bugs the hell out of me, and I want to sort it out!!

Edited July 23, 2018 by Christopher Low

[downscc 1,327]

2 hours ago, Johannvr said:

I suspect this is a flightsim issue, FSX in my case

Ditto.  The NAV radio ILS selection and the FMS approach selection are not in sync in these special cases.  In the real aircraft, you would not have this problem.  It is a simmism in my opinion.

5 hours ago, Qavion2 said:

The GPWS computer probably monitors the changing altitudes and only arms this mode if the aircraft is seen to be descending through 1000'. Similarly, the altitude callouts need to be armed by the aircraft climbing above a certain height. This prevents nuisance height callouts during climb.

Maybe, but I'd expect the FCOM warning systems section that has many pages of a table that defines when and why specific warnings are inhibited to include something on the GS aural.  It doesn't, so I'm not quick to adopt the opinion that maybe it does inhibit.  Could I be wrong?  You bet I could.

[Qavion2 39]

Even if the logic didn't need to be armed by the aircraft reaching 1000', there will be no usable glideslope signals in that scenario because of ground antenna design and fuselage/gear signal sheilding. The glideslope ground antenna (near the start of the runway) is designed to only work in one direction and even if it wasn't, since the aircraft receiving antenna is mounted on the nose, the ground station signal would have to go through up to 70 metres of metal fuselage when the aircraft is flying in the wrong direction.

Not applicable in this case, but my books say that the warning logic needs to see the aircraft flying on an ILS front course. If, for example, you are using a runway where the ILS frequency is the same in both directions, you will need to be flying in roughly the same direction as the runway course you have selected on the Nav Rad page before you get warnings.

 

 

[Christopher Low 5,368]

Just out of curiosity....would this problem vanish if I disabled the back course option on 05L?

[JRBarrett 3,095]

11 hours ago, Qavion2 said:

Even if the logic didn't need to be armed by the aircraft reaching 1000', there will be no usable glideslope signals in that scenario because of ground antenna design and fuselage/gear signal sheilding. The glideslope ground antenna (near the start of the runway) is designed to only work in one direction and even if it wasn't, since the aircraft receiving antenna is mounted on the nose, the ground station signal would have to go through up to 70 metres of metal fuselage when the aircraft is flying in the wrong direction.

Not applicable in this case, but my books say that the warning logic needs to see the aircraft flying on an ILS front course. If, for example, you are using a runway where the ILS frequency is the same in both directions, you will need to be flying in roughly the same direction as the runway course you have selected on the Nav Rad page before you get warnings.

 

 

The signal level reaching the glideslope antenna from behind the aircraft would be less than optimal, but might still be sufficient to give an indication, especially when still close to the transmitter.

There may well be a bug in the EGPWS code in the PMDG 744 that is causing this. Part of the problem though is related to the way that FSX/P3D determines the active ILS transmitter on a runway that uses the same frequency on both ends of a particular runway. It depends on the aircraft position. The active transmitter will be whichever one is closest to the aircraft’s current position.

You can taxi onto the threshold of such a runway in any FSX/P3D aircraft equipped with a nav radio and tune the ILS frequency while monitoring the Morse code identifier for the ILS. If you then taxi slowly down to the opposite end of the runway, you will hear the identifier switch as you pass the 50 percent point of the runway’s total length.

So during the climb phase after takeoff, there is no way to avoid passing through the glideslope beam for the opposite end of the runway, penetrating it from above, then ending up below unless the climb angle is quite steep.

The EGPWS should not respond to the glideslope of course in a takeoff/climb scenario.

X-Plane has an option where you can automatically disable the ILS transmitters for any runway that is downwind based on the current surface METAR reports. This works no matter what the aircraft’s position is in relation to the runway.

[downscc 1,327]

4 hours ago, Christopher Low said:

Just out of curiosity....would this problem vanish if I disabled the back course option on 05L?

No because in the simulator world, which ignores all real world rules of radio propagation and antenna location, your 05L is the same frequency as 23R.  Your choices have already been explained, use the same runway for your local circuits or inhibit GS on departures.  As Jim pointed out and I have pointed out twice, this is a simmism.

Edited July 24, 2018 by downscc