Approaches PMDG 777

Posting this query here since I cannot for some reason get access to the Avsim PMDG forum.

I am trying to work out consistent autolands on the PMDG 200 777. I am using the FMC to build routes with SIDs and STARs navigating on LNAV and VNAV AutoPilot.

The route is followed well by the plane, making the correct descents at the indicated times on the LEGS page. On Approach the plane follows the VPATh descent, indicating on the CDU that the glide slope is being tracked, but I cannot get the LOC and APP buttons to respond, and the G/S indicator never comes on either in white or green, despite repeated attempts all the way down to the airport. The result is a Terrain warning as I approach the strip, and I have to manually land.

In many attempts, only once has the LOC and G/S facility worked.

I have lowered dialled in altitude to zero before arriving at T/D, and reduced radio altitude to 50 early on in the flight.

Any ideas where I am going wrong?

Common reasons why you cannot track the ILS glideslope:

 

1) There's isn't one for the runway you have selected. The FMS is just following the programmed descent profile for the conditions (airport, terrain, runway, weather and altitude) according to the onboard approach charts for the airport.

This seems the most likely reason you cannot activate APP mode.

 

2) You are above the GS when you activate APP mode. This will prevent the AP from tracking the GS. This one is not likely because your APP mode is not available.

 

3) You are activating the APP mode while too far away and outside the range of the GS.

By default, FS will go into ILS mode only and will not track a valid GS (even if it is available) if APP mode is activated outside the range where the GS needle appears. At most locations, the upper range is about 21.5 miles, but can be as low as 19 miles.

 

4) You have not tuned the Nav radio 1 to the ILS frequency of the runway you chose. Some valid ILS transmitters do not have a GS.

 

Note: There are several ways to discover if the runway of your choice has an ILS and/or GS.

 

-Pv-

Did you try out the provided tutorial flight from VRMM-OMDB. You could use it to compare it to what you're doing wrong.

I'd bet $10 it's #4 what pvarn said.

a runway must be entered to FMS so it knows what frequency to tune to.

It can be entered manually too on RAD/NAV page.

Thanks for the replies.I had been through the tutorial prior to posting. Today I have been through the tutorial flight twice more, following it word for word. The plane followed the route all the way to the airport. After turning onto finals, at 20 DME I tried to activate LOC and then APP, and also later closer to touchdown. On the first occasion the altitude was dialled in at 0, and the plane descended to the strip, but never locked onto the glide slope. On the second try, altitude was set at 2000 ft for final leg. Again no response on trying to lock onto the glide slope. The plane flew over the airport at 2000 ft. The PFD as the plane turned into finals showed SP, LNAV and VPATH. Nav radio showed the correct frequency of 110.10.

I have also tried a flight from Heathrow to Manchester, UK. Definitely an ILS landing with correct frequency dialled in. The whole route was constructed in the plane's FMC including departure and arrival airports. The Manchester STAR was entered into the FMC. Same result- no response from LOC and APP on finals.I even tried taking finals at a lower height than calculated by the FMC to try to get under the glide slope and then make contact.

I am running out of ideas. Any help greatly appreciated.

With mine, after pressing APP, I imediately press both CHD's!

Peter Sydney Australia

Sorry, Peter, but what are CHDs?

Does the 777 have a single ILS tuning head like the 767 does? If so, that may be your problem, since the ILS would need to be tuned on that tuner, and not VOR 1 or VOR2 (in the 767 you actually cannot tune ILS frequencies on the VOR head)

A picture would help...

RADNAV page, autopilot set up and etc...

Ok, here we go with some pics of a route landing at EGCC, Manchester airport. These images are taken as plane levels out for final approach. Again LOC and APP inoperative.

From picture 3, it looks like you are above the GS. Bottom right of the artificial horizon on the PDU, magenta arrow is at the bottom of the scale. Your DME shows you are 6.8 miles from the runway and altitude is 2900ft, if you look at the chart for EGCC RWY23R, ( http://www.ead.eurocontrol.int/pamslight/pdf/4e415453/EG/C/EN/Charts/AD/EG_AD_2_EGCC_8-9_en ), at 6.8 miles, you should be at about 2500ft.

 

Hope that helps a little, you need to be lower and intercepting the GS from below.

Exactly, there you go with ILS being operable as seen from the pictures posted. Too high.

Thanks for the responses.

So, dialling a STAR into the FMC, will not automatically bring the plane in at the correct altitude to intercept the glide slope, as I had assumed? The tutorial gave no indication that height needed to be manually modified as per the position of the magenta arrow.

Presumably the vertical path deviation indicator on the navigation CDU serves the same purpose as the magenta arrow on the PFD.

One has to monitor the vertical path deviation and if it deviates, override the autopilot and lose or gain height as appropriate?

No. The STARs purpose is to reduce controller workload to sequence and space inbound aircraft into the airport from the Enroute system. Some STARs do have transitions that do link up to approaches, but not all. Mostly are a vector segment where at that point you would get a vector to the final or get further vectors for sequencing behind traffic.

At 6.8 miles and 3,000 ft you are indeed TOO CLOSE to the runway to capture the ILS.

 

At that altitude you should be closer to 10 miles and the purple arrow on the right side needs to be above the center line before capture.

In your image it's at the bottom which means the GS crossed the center line long ago. It's now too late and nothing you can do about it.

 

You will have more success if you are between 15 and 20 miles from the runway while level at the approach capture altitude waiting for the GS marker to drop. This isn't particular to the model you are flying. ALL FS planes work this way and just basic technique and learning to interpret your instruments.

 

-Pv-

Hope folks don't mind if I pursue this.

So I shouldn't leave it to the autopilot to follow the FMC down to the airfield. At say 30 miles from the field, I should feed in some vertical ascent or descent via the V/S section of the autopilot if needed to keep centralised or a little above neutral on the glide slope needle down to approx 20 DME when I should attempt to apply LOC and APP to lock onto the G/S. Is that how it works?

Disclaimer

This is a general explanation about default aircraft,of the glideslope and how to catch it. I know nothing of the PMDG FMC, and it's particular autopilot modes.

This text just explains how to catch the glideslope in a default aircraft (like the b747_400 or 737_800 for example).

 

The glide slope has an angle of 3.3 degrees. This is also called 5% slope.

This is the relation between distance travelled vertically, and distance traveled horizintally. ( across a sloping track.

Explaining more would take too far.

 

However, there is a simple relationship between distanc vertical and distance horizontal on the glide slope.

"300ft down for every NM forward"

 

So, 10 NM from the touchdown zone, the glide slope is at 3000ft.

20 NM from the touchdown zone the glideslope is at 6000 feet.

 

I imagine a point 10NM from TDZ, at 3000ft where I want to end up. There I want to have the plane follow the glideslope down.

 

I usually come flying in at 3000ft above the ground.

20 NM from the RW I recieve the glideslope, at that distance the glideslope is above me.

getting closer I start to see the glideslope indicator moving down when I'm 14-13 NM from the TDZ.

That is the point I engage approach mode.

For a few seconds the plane keeps flying straight on.

Then, at exactly 10NM it intercepts the glideslope and starts to follow the signal down. Towards the TDZ.

 

I keep a close eye on alt vs distance. Expecting:

9NM -- 2700ft

8NM -- 2400ft

7NM -- 2100ft

So, 300 ft descent per NM

 

This is not only so in FS(X), it is how a glideslope works in real life too.

 

Note(1): Not every glideslope is 3.3 degrees in real life, but I think in fsx most are that angle.

Note(2): A glideslope is a signal that is sent up into the air from a transmitter that is located at the runway. The signal is recieved by the aircraft and the autopilot the follows that signal.

 

hope that helps.

(did you learn the default aircraft first, or jumped right in with the PMDG?)

"Hope folks don't mind if I pursue this.

So I shouldn't leave it to the autopilot to follow the FMC down to the airfield."

 

Alternatively, if you want to follow the pre-programmed FMC solution, there is no problem with that, but it may not be as accurate.

 

I do this sometimes when flying in Multiplayer ATC and I get too busy to tune radios and such and just let the FMC take me in closer while I deal with other stuff. If you know all the ways to get into a good landing configuration, then you have the flexibility to choose the best when you get in a jam. The FMC can certainly help when there isn't a GS. I do that sometimes too when the wx is socked in with no GS and I cannot see the terrain.

 

If you WANT an autopilot glideslope capture down to decision height, the autopilot in FS is completely capable of performing this un-aided as long as:

 

1) You have a valid ILS frequency tuned in your nav1.

2) The runway ILS you have chosen HAS a glideslope.

3) Your plane is level and heading the right direction far enough out that when the GS marker appears on our Attitude Indicator ( FS has a distance limit of 19-21 miles) the marker is above the center line on the gauge.

4) You have APP mode selected AFTER the GS marker appears. If you turn on APP mode BEFORE then, the APP program ASSUMES you want an ILS only approach and will NOT capture the GS even if you have done EVERYTHING ELSE RIGHT.

Added:

Just for completeness I'll also add the obvious:

5) The Autopilot and Avionics master switches have to be on with battery and/or generators.

6) The Nav/GPS switch HAS to be in NAV mode. If not, the APP mode will turn you away from the ILS.

 

If your speed and flaps settings are not correct for the flight profile, the computer may lose lock on the GS.

 

-Pv-

Thanks for all the replies. Il88pp and pvarn, thanks for the explanation which is very helpful. I think the 'autoland' title I has been deceptive for me and should perhaps be more accurately called successful glide slope capture. I will practice the technique.

I have been flight simming for a couple of years but concentrating on GA aircraft and NDB/VOR navigation until my more recent purchase of of the PMDG 777.

 

P.S "If you turn on APP mode BEFORE then, the APP program ASSUMES you want an ILS only approach and will NOT capture the GS even if you have done EVERYTHING ELSE RIGHT." EUREKA!!!