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Autopilot engagement in FMC mode

Printed From: Just Flight Forum
Category: Just Flight Products
Forum Name: L-1011 TriStar
Forum Description: Discussion area for L-1011 TriStar
URL: http://forum.justflight.com/forum_posts.asp?TID=31059
Printed Date: 28 Mar 2024 at 10:18am


Topic: Autopilot engagement in FMC mode
Posted By: r_ast
Subject: Autopilot engagement in FMC mode
Date Posted: 19 Oct 2016 at 3:17am
Hi! I´m a TriStar enthusiast and I didn´t find in the manual about Autopilot engagement in FMC mode. 
When I reach the correct ALT and HDG (the FMC was configured correctly, with the legs, as POST INIT ok), the autopilot tabs don´t engage. 

Any suggestions? 



Replies:
Posted By: FactionOne
Date Posted: 20 Oct 2016 at 3:20am
I'm not sure this will be of any help to you, but I've just completed my first 'proper' flight (point-to-point with full navigation); and I didn't have any difficulty with the FMC, so I thought it might be worth recording my 'workflow'.

At the gate, I got the aircraft powered-up on the APU, then programmed the FMC as follows:

1) RTE page (1):
Entered departure airport (EGCC), arrival airport (LEVC), and a flight number (1011 - it wouldn't let me have BAW1011 Unhappy).

2) DEP/ARR page:
Selected departure airport, scrolled through (NEXT/PREV) and selected the SID I was cleared for (LIST2Y).

3) When the SID was selected, I was returned to the RTE page (2), with a DCT leg to LISTO (the end of the SID) now in the plan. From there I added my airways and intersections up to & including the final waypoint where the STAR begins. I clicked the LSK(R) for 'ACTIVATE', which illuminated the Execute Annunciator (indicating the FMC had a new plan in memory, but not yet set to be followed).

4) I went to the DATA page, and saved the flight plan for future use; then hit the EXEC button (which extinguished the annunciator), so the FMC was now 'following' my route.

Next, I set-up the autopilot:

5) I turned-on the captain's Flight Director.
6) I selected a climbout speed: 220 IAS (don't select the autothrottle yet).
7) I selected my initial cleared altitude (5000'), and hit the 'arm' button for it.
8) I armed the V/S mode, and I selected an initial rate of climb (+2400fpm).
9) I selected the FMC source for NAV (the green-lit button toward the bottom left), and then armed the NAV mode (toward the far end of the panel).

I got my taxi clearance, then take off; after I rotated and stowed the gear, I stabilised my climb and then selected the autothrottle on.

LIST2Y has a pretty severe turn almost immediately, so I selected AP1 to CMD, and the aircraft started the left turn according to the SID. After that it was just selecting altitudes* all the way to FL380; the FMC was following the route nicely.

Crossing into Spain, I went back to the DEP/ARR page, and selected my STAR, approach, and transition; the Execute Annunciator light lit up, I hit EXEC, and then I was just selecting altitudes* all the way to the ILS. Big smile

Hope that's useful (apologies if not!)

Happy landings!

Rob.

*(and enjoying the general ambience, old-school gauges, and the altitude horn. LOL)


Posted By: r_ast
Date Posted: 20 Oct 2016 at 5:03pm
Thank you very much, Rob! I'll follow yours instructions. 
In the landing, have you set the correct ILS frequency or auto land do all I need?


Posted By: r_ast
Date Posted: 20 Oct 2016 at 5:05pm
Other question: I only move AP1 to CMD? In the manual (in INS mode) I saw AP1 e AP2 moved up... 


Posted By: FactionOne
Date Posted: 21 Oct 2016 at 3:26am
You're very welcome... Hopefully you had a good flight :)

To answer your questions:

To set-up for the ILS: While I was still flying the STAR with the FMC, I selected the ILS frequency* at the left of the autopilot panel, and the runway heading in the course* window toward the first officer's side.

*[I'm sure you're aware, but these can be found in the Map View or if your add-on airports/stock navaids are up-to-date, aerodrome charts.]

Once I was ready to continue down the ILS (actually, I get clearance from Pro-ATC/X, but you should see the localiser and glide slope indicators come alive when the ILS is received, even with the Flight Director bars being driven by the FMC), I switched the NAV source from FMC back to RADIO (the green-text button again), and made selections for LOC / APPROACH accordingly.

And for the AP CMD switches: Indeed, I only had AP1 in CMD for the entire flight (I couldn't engage AP2 when I tried; perhaps it would've let me when it was receiving ILS, to allow CAT III auto-land).

Best regards,

Rob.



Posted By: r_ast
Date Posted: 22 Oct 2016 at 10:58pm
Dear Rob! Greetings from southern Brazil!
Thank you for your patience and goodwill. I could do all the flight planning and FMC worked perfectly with autopilot. 

However, I still can not run the landing by Company Instrument (ILS). The last coordinate FMC me indicates an altitude and understand that from this last passage, I switch to FMC Radio. The frequency and angle of the runway were entered correctly, but the plane falls not alone and comes to stalling. 

I was used to the FMC 737 PMDG and this one's TriStar seems to be a little different. Ideally have a video of an ILS landing to get a sense of what commands should I run this time of descent, because until the end of the cruise, I'm dominating perfectly.


Posted By: FactionOne
Date Posted: 24 Oct 2016 at 2:41am
Hello again (and thank you! (you're most welcome!)),

I'm not sure I understand exactly at which point you're having difficulty (but please don't worry - your English is infinitely better than my Portuguese!); so I'll go with a general description of (how I understand) the procedures from top of descent to capture of the ILS - and how it likely (I'm not a regular Boeing pilot) differs to the same in a late-model 737. (I'll try to make a video in future.)

The key difference between the TriStar and a 737NG, I imagine, is that a 737NG's FMC/autopilot supports (I guess) full VNAV - that is to say you could select the altitude of the FAP for the ILS at the top of your descent, and it'll come down on its own making adjustments for altitude & speed constraints on the way, and bring you to the ideal spot to capture the ILS. The TriStar's VNAV of course is advisory only, so you get some guidance of where you need to be and when, but you're more involved in making sure it happens according to plan.

I'll use (a slightly tweaked version of) the flight plan I used to get to Valencia (LEVC) as an example. Actually, flying with ATC, I had instructions for altitude so I didn't worry too much about guidance from the FMC; but anyway...

I was cleared via SAURA3D to ILS-Z RWY 12. I won't post the charts in the forum (but they are available free from https://eadbasic.ead-it.com/cms-eadbasic/opencms/en/login/ead-basic/" rel="nofollow - Eurocontrol EAD Basic ); hopefully I can describe things clearly enough without.

The STAR begins at SAURA, which is 48.2 DME on the 017 radial FROM the Valencia (VLC) VOR/DME. We continue toward VLC along the 017 radial, the STAR requiring that we're at or above FL80 until 32.2 DME VLC, and at or above FL65 until 20.0 DME VLC. There, we make a right turn to fly an 18.0 DME arc of VLC, until we make a left turn on to the 301 radial FROM VLC (in reality, course 121 TO VLC), where at 16.0 DME we're at waypoint OPERA - which is the IAF for the ILS-Z RWY 12 approach. Minimum altitude all the way around the arc, and at OPERA, is 5000 feet.

From OPERA we make a gentle right turn to 138 degrees, until 13.2 DME VLC, where we make a left turn to align with the runway, 116 degrees; descending to the FAP altitude, which is 2800 feet. We need to be at 2800 feet at or before 7.7 DME [ILS], so that we intercept the glide slope from below, and when we select APPROACH mode (which we plan to do at or just before 7.7 DME [ILS]), the autopilot captures and descends down the GS (remember: you need always to intercept a glide slope from below (effectively you fly 'into' the slope which extends back above you)).

Here's what the FMC came up with when I selected the STAR and approach:



You can see that its computed VNAV has us in the cruise until somewhere between SEROX and CASPE, and if we descend according to its path we'll reach SAURA at FL183, which should have us comfortably above the FL80 and FL65 restrictions at the beginning of the STAR. You can also see that we're well above the 5000' minimum on the arc as we cross the waypoints at various radials of the VOR/DME. The computed path reaches OPERA at 4700 feet (which is a little below the minimum permitted altitude on the chart, but not so much that it'll be a problem to correct on the way). I would say that the path in the FMC is pretty good, so we could 'ding' the cabin crew to stow the trolleys just short of SEROX and begin descending around there.

I'd select 5000 feet as the target altitude and begin the descent; when you leave your cruise altitude, you should be able to monitor your deviation from the computed vertical path on the FMC PROGRESS page, making corrections to your vertical speed as necessary to keep the deviation as close to 0 as possible. By doing that, you should reach 5000 feet just short of OPERA. On the way to OPERA, prepare the autopilot for the ILS (NAV1 radio to 111.50MHz, COURSE to 116).

At OPERA, resume descending to 2800 feet as the FMC commands LNAV to turn for the FAP. Just short of the FAP (7.7 DME, 2800 feet), switch the autopilot back to RADIO, and select APPROACH mode. All being well, the aircraft will capture the glide slope and begin descending toward the TDZ. [Approaching the FAP, the glide slope indicator on the Attitude Direction Indicator should be moving down toward the centre of the gauge, and when it gets there, the aircraft should pitch down to follow the GS].

One important thing to note... I'd probably use more conservative speeds than indicated in the FMC screenshots. 250kts at OPERA wouldn't leave much distance to dissipate energy off the airframe enough to be configured correctly and stabilised on the the ILS. It'd probably make for a far calmer approach to be at flaps 10 or 18 crossing OPERA.

Sorry to have given you so much to read, hopefully it's useful; I'm pretty sure you'll find flying it will be the easy part! :)

Best regards,

Rob.



Posted By: r_ast
Date Posted: 25 Oct 2016 at 4:52pm
Dear Rob, I do not know how to thank such generosity on your part to be detailed and patient with my problem. I just made a successful landing (still need to improve the flare) with ILS. The TriStar really is a little different from NGX regarding the FMC but now, thanks to your kindness, I managed to achieve my goal. A big hug from here in Brazil and God bless you.


Posted By: FactionOne
Date Posted: 27 Oct 2016 at 8:52am
I'm very glad to read that you were able to complete the flight Thumbs Up

Thank you for your generous reply; my advice is by no means expert - I'm still learning every time I fly the TriStar; but it's very pleasing to think that I might've helped even a bit.
(I worried after my reply that the autopilot might need LOC before APPR (good practice) to properly capture - so I checked and it was OK here too Geek)

I'm looking forward to learning more about this interesting old machine; and wish you more happy landings too.

Best regards,

Rob.


Posted By: G-BANJO
Date Posted: 31 Oct 2016 at 10:01pm
Hi, Rob.    Looks like you've got everything working very nicely. I am fairly new to FSX SE and am using the Tristar to attempt learning about working with the FMC. Problem is it appears not to be functioning with no data showing at start up and when I hit the 'DATA' key the FMC screen goes blank, allowing me to go no further. I have uninstalled, redownloaded and reinstalled with the identical result.

I wonder if I am missing something simple like the need to initialise everything first?

Any ideas or guidance much appreciated, please.

Thank you,

Brian


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Thank you for your help,

Brian


Posted By: G-BANJO
Date Posted: 01 Nov 2016 at 1:03pm
Hello, again

May have solved this. I checked for FAQs at JF Support to see that Windows 10 is missing a font (Latha) used for the FMC display. I will download/install the fix and try again later.

That'll teach me to check there first in future!

Regards,

Brian


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Thank you for your help,

Brian


Posted By: G-BANJO
Date Posted: 02 Nov 2016 at 8:44am
Yes, that was it then. Font installed and FMC displaying fine.

Onwards with the FMC training.

Brian


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Thank you for your help,

Brian


Posted By: FactionOne
Date Posted: 08 Nov 2016 at 3:20pm
Hi Brian,

I saw your first couple of posts together, so figured I'd give you a day or two to try the font thing before checking-back/replying; unfortunately it's only now I've had chance to sit down and do it - my apologies.

I'm glad to read the font fixed it - when you mentioned it I remembered reading that FAQ item, but I wouldn't like to guess how long it'd have take for me to think of it otherwise as I'm clinging-on to Windows 7 - I only use Windows on two machines for two packages (one being P3D), and I'm trying to avoid the new UI(s) with their (imho) worse UX and increased data-harvesting as long as I possibly can!

Anyway, I hope you're having fun learning the FMC - I've found that while it's not without its quirks, it's a pretty good one - it seems to deal with STARs & Transistions pretty well, and a lot better than some others out there.

Happy landings!

Rob.


Posted By: G-BANJO
Date Posted: 11 Nov 2016 at 1:01pm
Thanks, Rob

I have a brand new PC with Windows 10 preinstalled. Once settled, FSX SE runs pretty well. However, some Windows updates have caused havoc with addon aircraft all but disappearing and requiring reinstallation.

Things also became pretty screwed up following an nVidia driver update back in the Summer. By trial and error I discovered that rolling back to the previous driver version put it straight again.

As far as Tristar is concerned, I'm having a lot of fun learning how to handle it, bit by bit. Certainly, a long straight run up to the landing approach, speed bled off and hitting the GS at just the right time seems essential. Otherwise, a buckaroo ride would seem guaranteed!

Steadily getting familiar with the FMC capabilities but, thankfully, still lots to keep my old brain active.

Thanks again,

Brian


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Thank you for your help,

Brian



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