Possible Bug:
250/10000 speed restriction not honored (during cruise phase). 757 and 767

Flight Phase:
Level-off to cruise (below 10,000ft)

Manual Reference:
No manual needed

Issue:
When cruise altitude is below 10,000, at level off, the CS 757/767 ignores the SPD TRANS of 250/10000 and accelerates to cruise speed (well above 250KIAS).

Can any one with a little more real world experience chime into whether or not it's a bug? It's not written in my airline manual anywhere at all, I've read all the VNAV chapters today and no clue, it's rare you'll be in CRZ phase below 10000 (except lately lots super short of repo flights IRL!), but now I wonder. I know every other plane I've flown IRL has honored any climbing restrictions to cruise if the restriction is lower than the cruise speed.


https://i.imgur.com/3dMQrVI.jpg

I've had this problem since day one with the 757 not surprised to see it's in the 767.

The B744 has a similar thing where by if you don't put in the speed restriction under speed trans then it will speed away.

Aussiesix8 wrote on Apr 28^th, 2020 at 9:44pm:

The B744 has a similar thing where by if you don't put in the speed restriction under speed trans then it will speed away.

Not quite the issue here, let me explain more.

On all Boeing FMCs: 737,747,757,767,777 nothing needs to be entered into SPD TRANS, unless it needs to be different than 250/10000 on climb or 240/10000 on descent for a specific company/atc/performance reason.

The question I'm asking is this: There's obviously no way to enter a speed restriction on the VNAV CRZ page, there is no box for SPD TRANS or SPD REST or anything. So, if the airplane changes to the CRZ phase, will it honor either the restriction from the climb, or the Descent, or none at all? If the real plane won't honor one (sounds crazy but I could see this being the case), then Captain sim got it right. That's what we're trying to figure out here.

Alex T wrote on Apr 28^th, 2020 at 10:17pm:

Aussiesix8 wrote on Apr 28th, 2020 at 9:44pm: The B744 has a similar thing where by if you don't put in the speed restriction under speed trans then it will speed away. Not quite the issue here, let me explain more. On all Boeing FMCs: 737,747,757,767,777 nothing needs to be entered into SPD TRANS, unless it needs to be different than 250/10000 on climb or 240/10000 on descent for a specific company/atc/performance reason. The question I'm asking is this: There's obviously no way to enter a speed restriction on the VNAV CRZ page, there is no box for SPD TRANS or SPD REST or anything. So, if the airplane changes to the CRZ phase, will it honor either the restriction from the climb, or the Descent, or none at all? If the real plane won't honor one (sounds crazy but I could see this being the case), then Captain sim got it right. That's what we're trying to figure out here.

It's been quite a while since I have cruised below 10k so I can't really recall what the FMC did in CRZ... I'm pretty sure I didn't even operate in VNAV that low.

However, the "fix" or way to cope would be to enter 250 in the ECON SPD.  That will honor the speed of 250 below 10.  In VNAV CRZ there is not speed/altitude constraint since you would be in level cruise flight.

I'll have a chance to play with the plane this weekend, so I'll check to see what it does with a cruise below 10.

logan3db wrote on Apr 29^th, 2020 at 12:08am:

Alex T wrote on Apr 28th, 2020 at 10:17pm: Aussiesix8 wrote on Apr 28th, 2020 at 9:44pm: The B744 has a similar thing where by if you don't put in the speed restriction under speed trans then it will speed away. Not quite the issue here, let me explain more. On all Boeing FMCs: 737,747,757,767,777 nothing needs to be entered into SPD TRANS, unless it needs to be different than 250/10000 on climb or 240/10000 on descent for a specific company/atc/performance reason. The question I'm asking is this: There's obviously no way to enter a speed restriction on the VNAV CRZ page, there is no box for SPD TRANS or SPD REST or anything. So, if the airplane changes to the CRZ phase, will it honor either the restriction from the climb, or the Descent, or none at all? If the real plane won't honor one (sounds crazy but I could see this being the case), then Captain sim got it right. That's what we're trying to figure out here. It's been quite a while since I have cruised below 10k so I can't really recall what the FMC did in CRZ... I'm pretty sure I didn't even operate in VNAV that low. However, the "fix" or way to cope would be to enter 250 in the ECON SPD.  That will honor the speed of 250 below 10.  In VNAV CRZ there is not speed/altitude constraint since you would be in level cruise flight. I'll have a chance to play with the plane this weekend, so I'll check to see what it does with a cruise below 10.

Exactly what I was thinking! There's always a workaround haha. Thanks so much, please report back with some info, that would be cool!

You just lost me) Is there a bug or not?  :-?

Captain Sim wrote on Apr 29^th, 2020 at 1:22am:

You just lost me) Is there a bug or not?  :-?

Not sure!  ;D it's never something we deal with in real life so it could just be a Boeing quirk, so our friend will have to do some investigation on the real airplane soon and report back.

On all my flights where I've had to level off below 10,000' (after the descent), I have never had a problem with the 767 holding the speed around the 240-250 knots.

Markoz wrote on Apr 29^th, 2020 at 1:28am:

On all my flights where I've had to level off below 10,000' (after the descent), I have never had a problem with the 767 holding the speed around the 240-250 knots.

Exactly, you were in CLB mode, we're talking about CRZ mode; seems to be the time the plane accelerates to above 250 below 10,000.

Alex T wrote on Apr 29^th, 2020 at 1:29am:

you were in CLB mode

I didn't think it was, but I'll check on the next flight that that happens on.

Alex T wrote on Apr 29^th, 2020 at 1:25am:

it could just be a Boeing quirk

Most likely :)

Markoz wrote on Apr 29^th, 2020 at 1:28am:

On all my flights where I've had to level off below 10,000' (after the descent), I have never had a problem with the 767 holding the speed around the 240-250 knots.

I think the question was when you're in cruise mode below 10k does the plane command 250 to adhere to the requirement or will it want to do over that.  Like you, I've never seen the plane command above 250 below 10 in the descent mode (or climb for that matter).

I did a flight from ONT to LAX and I never even looked to see what VNAV ECON Cruise had in store for us.  Once off the ground we were held low with crossing traffic so I used V/S to avoid any TCAS issues so we never even entered VNAV cruise. 

I DO know on my previous plane the FMC wouldn't adhere to the 250 below 10 in cruise unless we intervened. 

As for this being a bug or not, standby and I'll have an answer soon!

I have done flights where I've cruised at 9000'-10000' before, but that's usually when I'm testing something else, and have no need for the flight to exceed 10000'. I haven't done that in the 767 II yet, but that's easy enough to do.

Do you remember if your Cruise page gave you 250, or another number above that? 

logan3db wrote on Apr 29^th, 2020 at 2:54am:

Do you remember if your Cruise page gave you 250, or another number above that?

It gave me 315KIAS or something to that effect

The aircraft should not accelerate above 250kts below 10000' in VNAV if you have that speed restriction entered on the Climb page. (SPD Trans/SPD Restr).   
The FMC Legs page should not show a speed higher than 250/10000'.
The speeds on the legs page are wrong below 10000'.
One waypoint has a speed restriction on the arrival of 210/5000. The next waypoint is showing 307 kts etc.

Secondly when going direct to a waypoint with a speed restriction on the FMC Legs page,  the Captain Sim 757/767 immediately decelerates/accelerate to that speed irrespective of the distance to that waypoint. Also not correct.

I also notice when selecting an STAR on the arrival page on the FMC the first waypoint seems to missing from the STAR.
Tried a few airports and several different STARS, first waypoint was always missing on my system. Newest Airac installed from Navigraph.

LNAV is also a bit inaccurate. Has a tendency to turn early and undershoot the turn on an SID etc. Resulting in left and right turn oscillations.

I see the 757 got the same speed issues etc. Been reported numerous times. Bit surprised this had not been addressed. 

Offset capability?
FMC ALTN page?
FMC COMM page?
RNP Entry?
EICARS, for weather/atis uplinks etc?

Would be nice if Captain sim also incorporated an IPAD/TABLET on the window bracket for performance calculations and charts etc.
Most serious developers seems to be adding this feature nowdays :).

Chris

Eurosky wrote on Apr 29^th, 2020 at 5:35am:

The aircraft should not accelerate above 250kts below 10000' in VNAV if you have that speed restriction entered on the Climb page. (SPD Trans/SPD Restr).    The FMC Legs page should not show a speed higher than 250/10000'. The speeds on the legs page are wrong below 10000'. One waypoint has a speed restriction on the arrival of 210/5000. The next waypoint is showing 307 kts etc. Secondly when going direct to a waypoint with a speed restriction on the FMC Legs page,  the Captain Sim 757/767 immediately decelerates/accelerate to that speed irrespective of the distance to that waypoint. Also not correct. I also notice when selecting an STAR on the arrival page on the FMC the first waypoint seems to missing from the STAR. Tried a few airports and several different STARS, first waypoint was always missing on my system. Newest Airac installed from Navigraph. LNAV is also a bit inaccurate. Has a tendency to turn early and undershoot the turn on an SID etc. Resulting in left and right turn oscillations. I see the 757 got the same speed issues etc. Been reported numerous times. Bit surprised this had not been addressed.  Offset capability? FMC ALTN page? FMC COMM page? RNP Entry? EICARS, for weather/atis uplinks etc? Would be nice if Captain sim also incorporated an IPAD/TABLET on the window bracket for performance calculations and charts etc. Most serious developers seems to be adding this feature nowdays :). Chris

Entering a custom RNP works just fine on the 757/767 I use it often on ETOPS routes and RNP approaches.
I’ve also noticed the first waypoint is always missing on an approach if you choose a transition. You should post your concerns on the bug tracking page with the proper photos and information.

They clearly know what is not correct with this airplane. Lots of reports relating to the Vnav speed management etc.
I see the same issues on the 757 and that aircraft have been on the market for a while without any attempts to fix this basic Boeing FMS management.
I like realism and the simulation should get the basics correct as a minimum. 
It has potential, but it is far behind when it comes to correct speed management and accurate and precise flight path management.

Eurosky wrote on Apr 29^th, 2020 at 2:12pm:

The clearly know what is not correct with this airplane. Lots of reports relating to the Vnav speed management etc. I see the same issues on the 757 and that aircraft have been on the market for a while without any attempts to fix this basic Boeing FMC management. I like realism and the simulation should get the basics correct as a minimum.  It has potential, but it is far behind when it comes to correct speed management and accurate and precise flight path management.

For sure lots of things to be fixed with VNAV, I posted VERY detailed issues yesterday on the bug forum. They've acknowledged and thanked me for the reports and said they're working on it. We will see my friend!

Alex T wrote on Apr 29^th, 2020 at 4:05am:

logan3db wrote on Apr 29th, 2020 at 2:54am: Do you remember if your Cruise page gave you 250, or another number above that?  It gave me 315KIAS or something to that effect

Alright, I had a chance to load this up and try it out.  Granted both of these pictures were taken while on the ground, both times the FMC defaulted to a speed of 250 for the cruise.  I didn't get a chance to see what would actually happen in cruise flight, so unfortunately this was as good as I could get.

I loaded the same scenario in the FMC on the ground and I get a speed above 250 as well.  A quick edit of the ECON speed on VNAV CRZ fixes it to the way it should be.  The real FMC will perform this edit on it's own. 

I know that it goes back to my original post for a work around, but as far as I can tell this is indeed a bug.  Hope this info helps!

RW FMC 8000' cruise: https://imgur.com/a/1joQKRk
RW FMC 5000' cruise: https://imgur.com/a/MCAPD8Y
P3D FMC 5000' cruise no edit: https://imgur.com/a/bofbopL
P3D FMC 5000' cruise speed edit:https://imgur.com/a/hTHb4px

logan3db wrote on May 1^st, 2020 at 7:17pm:

Alex T wrote on Apr 29th, 2020 at 4:05am: logan3db wrote on Apr 29th, 2020 at 2:54am: Do you remember if your Cruise page gave you 250, or another number above that?  It gave me 315KIAS or something to that effect Alright, I had a chance to load this up and try it out.  Granted both of these pictures were taken while on the ground, both times the FMC defaulted to a speed of 250 for the cruise.  I didn't get a chance to see what would actually happen in cruise flight, so unfortunately this was as good as I could get. I loaded the same scenario in the FMC on the ground and I get a speed above 250 as well.  A quick edit of the ECON speed on VNAV CRZ fixes it to the way it should be.  The real FMC will perform this edit on it's own.  I know that it goes back to my original post for a work around, but as far as I can tell this is indeed a bug.  Hope this info helps! RW FMC 8000' cruise: https://imgur.com/a/1joQKRk RW FMC 5000' cruise: https://imgur.com/a/MCAPD8Y P3D FMC 5000' cruise no edit: https://imgur.com/a/bofbopL P3D FMC 5000' cruise speed edit:https://imgur.com/a/hTHb4px

That's awesome, thanks for taking the time to check it out! I'll post this on the bug tracker and I'm sure it's a relatively quick fix in logic for them.

The speed restriction of 250/10000ft is only set during climb, it is on VNAV CLB page. When the plane reaches the desired cruice altitude, preselected on PERF or VNAV CRZ page, it changes his performance to the one entered on that page. It is part of the preflight to analyze and set the speed that you want to be set on cruise.

Michel wrote on May 1^st, 2020 at 8:25pm:

The speed restriction of 250/10000ft is only set during climb, it is on VNAV CLB page. When the plane reaches the desired cruice altitude, preselected on PERF or VNAV CRZ page, it changes his performance to the one entered on that page. It is part of the preflight to analyze and set the speed that you want to be set on cruise.

Not exactly, apparently when CRZ is below 10k, the plane knows to keep it at 250Kt

Michel wrote on May 1^st, 2020 at 8:25pm:

The speed restriction of 250/10000ft is only set during climb, it is on VNAV CLB page. When the plane reaches the desired cruice altitude, preselected on PERF or VNAV CRZ page, it changes his performance to the one entered on that page. It is part of the preflight to analyze and set the speed that you want to be set on cruise.

Or is this from real qorld experience? I know the 737 doesn't do that and the FMSs are somewhat similar.

Planned decels have been a little bit of an issue (on my end). I was approaching a fix with a 250kt restriction (had to manually input -  FLASK.OZZZI1 27L @ ATL) and it kept an adequate descent but leveled off with just 2nm to go and 50kts of speed to bleed (no "drag required" annunciation on FMS). Thoroughly enjoying the product, glad there finally is a [decent] 767 for P3D v4. I put a lot of time on the FSX version as well as some other devs.