Hi all,

A problem that's been annoying me for a while, any help would be great.

I'm flying on LNAV and have a STAR and ILS all set up in FMS. Annoyingly and for some random reason LNAV puts me on a very acute interception course on the ILS, so much so that if I left it alone I would basically intercept the localiser at the runway threshold. Obviously this makes pushing the LOC or APP switches irrelevant as I'm not on an intercept course.

There are fixes and waypoints plotted in but the LNAV seems to just ignore these even though they are in the FMS.

Hope I've been clear enough.

Any help?
Cheers

If I have a situation like that in a STAR/Approach, I use Heading Select and fly at around 180 degrees to the ILS runway heading, then when the Glide Slope rises above the 757, I fly for about 60-90 seconds, before turning back to a 45 degree intercept of the ILS runway heading. There are other things that need to be considered when doing this (like hills/mountains), otherwise I would crash, so I would change it a bit to take them into account.

Can you follow what I mean? If not, give me the details of the Route, STAR, Approach and Runway, and I'll look into what I would do to avoid this from happening.

I would love to hear how Lou deals with these situations, because he knows exactly how it is/was done in real life. ;D

Mark,

This is indeed a common problem. In the ATC environment the controller would never let this happen. They would vector you for a reasonable intercept angle. Most times YOU are the controller so make it happen!

Since you are most likely flying in just YOUR simulator, you have the ability to vector your aircraft to whatever heading you want. In the example of the ILS to RW 12R in KSTL you can alter your flight plan in the CDU to make the approach better for you. Let's say the CDU or STAR heads you at the end of the runway. All you need to do is add a few points to make the angle better.

If in this case, the STAR had you from FTZ to some point close to the end of the runway, you could add PAULY after FTZ or even NAIRN or the OM OBLIO. All would make the approach angle smoother.

Does that make sense?  :-?

Lou

http://img20.imageshack.us/img20/3203/d4n9.png

Uploaded with ImageShack.us

Thanks for that Lou.

That's pretty much what I do. After all it's not a "real" flight, and the FSX ATC is not involved. ;)

connoan wrote on Jul 26^th, 2013 at 8:07pm:

A problem that's been annoying me for a while, any help would be great. Any help? Cheers

Have you solved your problem? If not, please post the flightplan including departure/arrival airports with runways used and I will see if there is any additional help that I can provide.

Michael Cubine

DAL191 wrote on Jul 29^th, 2013 at 2:43pm:

connoan wrote on Jul 26th, 2013 at 8:07pm: A problem that's been annoying me for a while, any help would be great. Any help? Cheers Have you solved your problem? If not, please post the flightplan including departure/arrival airports with runways used and I will see if there is any additional help that I can provide. Michael Cubine

Hi Michael, no problem still exists. Seems strange as no one else has this problem so suspect it something I'm doing. Ill try and post my route and even capture a screen grab of the problem as it occurs.

Thank

connoan wrote on Aug 2^nd, 2013 at 5:17pm:

DAL191 wrote on Jul 29th, 2013 at 2:43pm: connoan wrote on Jul 26th, 2013 at 8:07pm: A problem that's been annoying me for a while, any help would be great. Any help? Cheers Have you solved your problem? If not, please post the flightplan including departure/arrival airports with runways used and I will see if there is any additional help that I can provide. Michael Cubine Hi Michael, no problem still exists. Seems strange as no one else has this problem so suspect it something I'm doing. Ill try and post my route and even capture a screen grab of the problem as it occurs. Thank

Hi Michael or anyone.

Below is my flight plan. I've also taken 4 screenshots to show the problem as it occurs but am not allow to post images yet :-/

The problem is that the waypoint DME12 is ignored by LNAV and instead heads straight for the next waypoint, UW which because it is at the runway threshold, means I don't intercept the localiser until I'm pretty much at the edge of the runway.

Any thoughts?
Cheers


FLIGHTPLAN

EGLL (Heathrow) 27L DEPARTURE

SID CPT3F

LEGS INCLUSIVE OF SID AND STAR

-D25BB
-D258G
-D262K
-WOD
-CPT8
-CPT
-TNT
-POL
-RIBEL
-SHAPP
-MARGO
-TAR35
-ESKD0
-TLA10
-TLA
-D323K
-D323O
-D323U
-DME12
-UW
-RW06

STAR TWEED1A TRANSITION TLA

EGPH (Edinburgh) ILS06

DME12 isn't so much a waypoint, but more of a reference of 12 nautical miles, using DME, from either a VOR or the ILS, but most probably the ILS.
At least that's how I read it. :-/

What AIRAC cycle are you using? The SID out of EGLL is associated with another runway. Probably 27R and not 27L. I don't even see a DME12 in the approach to runway 6 at EGPH. The attached image shows the last the last four waypoints before the runway and cover a distance of 32 miles. So I would think DME12 would be in there. However, you are correct about the plane not following the flight plan.  The plane is heading to the northwest based upon the first two waypoints. Prior to those two wapoints it turns to the northeast and flys directly to the airport and doesn't intercept the ILS LOC. So it's land by manual flight or nothing. I could use the same runways and try a different route. How would that be?

Michael Cubine

---

I tried a different route between EGLL and EGPH.  It was WOBUN3G WOBUN DCT  WELIN UT420 TNT UN57 POL UN601 MARGO TWED1A. Unfortunately it made no difference. At ESKDO the 752 skipped four waypoints that were in the FMS and shown on the HIS and turned from a northwest to a northeast heading straight to the airport. I decided to land manually but realized I was too high. So I did a 180 out to about 18 miles from the airport where I did another 180, picked up the localizer and landed. So there is a localizer and glideslope signal and the 752 picks it up. But doing a LNAV to capture the signal is not going to work. I have no idea what the solution is. Maybe someone else does. Until then you fly the balance of the STAR and the Approach using heading select mode rather than LNAV. Your route is on the HSI and if you fly that you should intercept the localizer. Or you could land manually or do a VFR.

Michael Cubine

When you select ILS Rwy 06 you are presented with two IAFs - TLA and UW. Select UW and then you can use LNAV. Once you are on inbound course, press LOC, dial 40 degrees in heading window, right click center select button and the plane should capture the localizer. When localizer is captured press  the APP buttton. Set your altitude to 2000 feet. 4000 is too high. By the time you capture the localizer you will be above the glideslope. Don't rely on VNAV for any of this. You need V/S to control the rate of descent to 2000. And go slow because you are doing all this in 12 miles.

Michael Cubine

First off so sorry it's taken me so long to respond, have a new baby so simming time is much less frequent these days.

Appreciate you looking into this Michael and your replies. I never even knew what an AIRAC cycle was until you mentioned it but after your post I went to Navigraph and downloaded FMS data update and I also went elsewhere to update navaids in FSX think therefore I'm on 13.08 update.

As I'm sure you know this hasn't solved the Edinburgh VNAV approach issue for me (and its good to know its not just me that's experiencing it).

Like you said I can use Heading select to get me on intercept with the ILS, and I have done in the past but it just kinda bugs me (no pun intended) that I can't use vnav.

Is this just s general fault with LNAV or is this something specific to my home airfield EGPH? Does your LNAV intercept work ok at other aerodromes?

Finally is this something I should raise with captainsim for a fix?

Cheers
Alan

LNAV works ok at other airports but I don't think there is anything wrong at EGPH. The 752 is just turning too soon and rolling out of the turn before it should. The turns must be precise if you are going to intertercept a localizer as soon as the turn is completred. The LNAV in the 752 is too sloppy to execute a precise turn. A 90 degree turn to intercept a localizer is difficult. However it can be done. I flew an additonal flight maybe two nights ago from EGLL-EGPH in the 737 NGX. Following the route, the turn to final, intercept, capture, and landing went like cllockwork. So there is nothing wrong with your home airport.

If you want to waste your time you could report this to CS support. The 752 has flown like this for the four versions that I have had. You just have to be ready for anything at anytime.


Michael Cubine

Edit – One of the things I find helpful is to draw a line on the HSI that shows the airport and the runway headings per the attached image. I can use this as a reference point if I end up doing a go around because of missing the localizer or glideslope. I fly parallel to this line on the outbound leg and follow it inbound. This can be tricky at large airports because the line runs thru the center of the airport and is not in anyway tied to a particular runway so you are going to be a hair to the right or left of the line but you will still intercept the localizer of the runway.
http://imageshack.us/a/img29/7899/ltod.jpg

The problem are the four points between TLA and UW.
@Mark : This is what I wrote about Navigraph at the 777 forum :) . In Europe Navigraph has to many iusses, means it is a wrong coding of the waypoints.

The approach is (Jeppsen): TLA VOR , after that you have four points :
TLA DME 11/15/20 and then at DME 21  you make a right turn to intersept the ILS at 4000 ft. Interseptionpoint is 12 DME IVG .

At NavDataPro it reads:
TLA , TLA11,TLA15,TLA20, OVFY TLA21 ,IVG12,IVG46

If i find a way to post pictures ,i put the chart and the FMS screenshot to show what i mean.

cheers Galskiman

i rarely use Vnav to intercept  usualy atc sends me vectors using flight chg and heading select to intercept once localizer captures arm app and sends me down the correct glidescope no problems,