Hi,

 

I'm having problems flying tutorial 1.5.  Can anyone out there offer some advice.

 

I've managed to complete the flight and land successfully at EDDM, but not without a lot of button pushing and intervention.

 

My main problem seems to be that I cannot get the T7 to descend at TOD even though I am in VNAV and have reset the ALTITUDE to 5000ft.

 

I suspect that the reason is that the FMA thrust mode is still in climb (CLB) from the first step climb and not cruise (CRZ).

 

If I let the FMC control the step climb is self by entering the new altitude of FL370, the thrust mode changes to CLB and then back to CRZ when the new altitude is reached as I would expect, but if I use SPD INT/FLCH climb as described in the Tutorial, thrust mode changes CLB and stays at CLB for the rest of the flight.

 

Anyone have any suggestions??

 

Colin Brown.

One thing at a time... your thrust limit will not be a problem. Some airlines such as AAL have CLB as a limit during cruise instead of CRZ. No significant difference.

 

First thing to look at when she doesn't respond as expected is the FMA.  The top of the PFD provides an indication of what the automatics are doing. Thrust, pitch and roll modes.  What are you seeing on the FMA after she flies past the TOD?

 

 

Anyone have any suggestions??

 

Yeah. The dude who wrote it is an idiot and probably could've been a little more clear:

 

"Prior to reaching TUDEP, request a climb to FL370 from the controller. To make the climb easier on the passengers and crew, roll the altitude up to 37000, press in on the SPD knob to enter SPD INT, press the IAD/MACH button above the speed window, adjust the MACH to .830, and then press FLCH. FLCH will climb less aggressively than VNAV would in this short of a climb. As the aircraft levels out at FL370, FLCH will drop to ALT HOLD. Leave the autopilot out of VNAV until crossing TUDEP, otherwise, as soon as VNAV is selected, the FMC will re- command the ECON speed. The goal is to be established on both altitude and speed when crossing the fix, and not beginning to adjust to both as the fix is crossed."

 

The bold part is the important part, but it wasn't conveyed in the best way. Basically, you have to re-select VNAV, and I'm guessing you just forgot, or didn't realize it because it wasn't explicitly stated that you should press VNAV again.

 

Basically, you need to climb to FL370 prior to TUDEP, so we used FLCH to do so. FLCH uses a set speed (M.830) to make the climb and it will remain on that set speed and in ALT HOLD until you reselect another mode. While the document states "leave the autopilot out of VNAV until crossing TUDEP," it should also have said that VNAV should have been re-selected at that point.

 

The reason you do this is that VNAV will assume that you want the ECON speed up until TUDEP, but we want to be established on altitude and on speed prior to TUDEP. VNAV doesn't see a speed restriction until TUDEP itself, so since we're already established at M.830, we wouldn't want to hit VNAV too early, have it recapture ECON, and then have it try to pick M.830 back up. There are other ways to do this, but I wanted to get people out of VNAV and off of the FMC to learn different things.

 

This is also the reason you're not descending: you didn't reselect VNAV after TUDEP. A little careful reading goes a long way, but a lot of careful typing on the author's part would've been better.

Hi Kyle,  Thanks for taking the time for your very full response.  However,...   I am in VNAV at TOD,  having reselected it, as you say,  when past TUDEP.   My problem seems to be that the thrust mode stays in climb (CMB) after obtaining FL370 and after I have reselected VNAV.

 

Colin Brown.

 

 

My problem seems to be that the thrust mode stays in climb (CMB) after obtaining FL370 and after I have reselected VNAV.

 

The thrust mode isn't going to prevent the descent, though. That's just the limiter. There's no descent mode for the A/T (as descents are usually made at idle, at least in the initial portion).

 

What is your A/T override setting? Are you pulling your hardware thrust levers back to idle before descending (or T/D)?

One of the "Equipment Options" accessible through the PMDG sub-menu in the FMC, is "FMS CRZ PHAS  THR LIM", which can be set to either CLB or CRZ.  Are you sure you don't have it at CLB ?

 

And, just as Kyle just pointed out, if you have an option to override the A/T set to on HOLD or Allways, then you have to retard your controller throttles to idle.

 

Although not directly 777-related, this excellent video tutorial by Captain "Britjet" is good to watch, for better understanding the "Boeing VNAV" logic

 

Pay attention to the portion starting around 05:19, where "HOLD" becomes announced, and throttles can now be adjusted at your will to set the required rate of descent. The same transition happens in the PMDG 777, and if you have the option to always or "on-Hold" override the A/T system ** AND ** your controller throttles are still pushed forward, you will have a problem ...

 

One of the "Equipment Options" accessible through the PMDG sub-menu in the FMC, is "FMS CRZ PHAS  THR LIM", which can be set to either CLB or CRZ.  Are you sure you don't have it at CLB ?

 

And, just as Kyl just pointed out, if you have an option to override the A/T set to on HOLD or Allways, then you have to retard your controller throttles to idle.

 

Although not directly 777-related, this excellent video tutorial by Captain "Britjet" is good to watch, for better understanding the "Boeing VNAV" logic

 

As far as the first part goes, if he's flying the PMDG-liveried 777 (as recommended by the tutorial), it should indicate CRZ at cruise, per the default options for our livery.

 

Good point, though, because he could be flying a different livery.

Hi Dan, Thanks for your reply also, and when researching your questions I've found the answer to my problem.

 

As I was approaching TOD my FMA was showing SPD | LNAV | VNAV ALT , my Altitude was set at FL390 and power mode was CLB.

 

When I rolled the Altitude down to 5000ft I noticed that the power mode changed to CRZ but nothing changed in the FMA.

 

Passed TOD nothing happened and I did not descend until if click-on the centre of the Altitude select knob, where upon I descended like a stone and got an 'Over Speed' warning and a 'Drag required' message on the FMC.

 

I re-ran and noticed that as I cross TOD the displacement from vertical path bar immediately showed that I was 4000ft to high.   Check the legs page on the FMC and spotted that the entry for HAREM read .826/FL350.  Check the VNAV page and found the Cruise height was set to FL350.

 

Re-ran and set the FMC, VNAV cruise height to FL390 and the power mode changed to CRZ and the FMA VNAV status changed to VNAV PTH.  Reset the Altitude to 5000ft and at TOD I started a gentle decent.  PROBLEM SOLVED.

 

Not sure how the Cruise height got set to FL350 as a step climb to FL390 was signified at the appropriate point.  However, this begs a question.

If I'm flying above my planned cruise height because of weather or on ATC's instructions,  do you need to go in and reset the FMC cruise level??

 

Anyway.  Thanks for the response.  learnt some more of the T7. 

 

Cheers  Colin Brown

Hi Jose,  Thank for the heads up on Capt Britjet video.  Brilliant,  explains thing very well.  I'll have to re-watch a few times and track down his other videos.

 

Thanks a lot,

 

Colin Brown 

 

 

If I'm flying above my planned cruise height because of weather or on ATC's instructions,  do you need to go in and reset the FMC cruise level??

 

It seems that you're never updating the CRZ ALT during this whole flight in the FMC. Again, this could have been made a little more clear in the tutorial, but this being a more advanced tutorial, it was assumed that knowledge of the step climb process was already known.

 

This is why your aircraft remained in the CLB throttle mode - it never knew it was at the new cruise alt. This is also why the VNAV descent was 4000 feet off - you climbed to FL370 and then FL390, which ended up putting you above your original FL350 cruise alt.

Hi Kyle,

 

Yes, interesting.  I've saved my flight at various stages so that I can re-run it after I've made the inevitable mistake.  When I re-run after I've climbed to the initial cruise height of FL350 and look at the legs page of the FMC it has FL350 out to TUDEP where a step climb to FL370 was added, then FL370 to MORAG where there's a step to FL390.  FL390 continues to BOMBI.  Following BOMBI no other fixes have speed or height settings presumable because there's no STAR or runway selected for arrival.

 

When I re-run the save of the flight when I just made the step climbs by dialling in the new altitude and clicking the altitude select button at the appropriate points, at TOD I find I'm VNAV PTH mode, power mode is CRZ, and the FMC VNAV page has the cruise height at FL390.  I'm not aware that I changed these manually.  At TOD the T7 descends in VNAV PTH as I was expecting.

 

Must do some more research and read up some more on step climbs.   Still that's what a 'Study Sims' all about.

 

Thank once again for your assistance.

 

Regards   Colin Brown. 

 

 

Must do some more research and read up some more on step climbs.   Still that's what a 'Study Sims' all about.

 

The normal procedure of things - if we weren't making it more difficult with different modes (FL CH, with a speed restriction after the climb) - would go like this:

1. Roll the altitude up to the next altitude
2. Go to the VNAV page (CRUISE - it should automatically pop up when you press the VNAV button)
3. Line select the STEP ALT (LSK 1R) and place it in the CRUISE ALT (LSK 1L)
   • Alternate: Type in the altitude you want to step to and place it in the CRUISE ALT (LSK 1L)
4. Press EXEC

Thanks Kyle.

 

Colin Brown

Thanks Kyle.

 

Colin Brown

 

Welcome! Post back if you have any issues!

Easier yet:

1. Roll the altitude up to the next altitude
2. Press ALT knob, which sets FMS altitude to new value and initiates VNAV SPD climb

Not as complicated as the NGX.  See FCOM STEP CLIMB 11.32.23 and CRUISE CLIMB 11.42.22. Note that if you manually enter a STEP TO value you override the FMS calculated step point.