Dear all,The cause abusive VNAV disconnect because of TOC TOD calculation failure has been identified, thanks to all your supporting posts and emails. Of course, the 0 fuel predictions are a direct consequence of no TOC TOD.You are in this situation if you entered a valid FP, a valid - and reasonable - cruize alt and have no TOC TOD showing on ND and fuel predictions are 0 on PROG page, along with no alt predictions on LEGS page.I am in the process of fixing it (initial fix and initial testing done, some needed code reorganization not done yet), and after that we will go through internal and external testing. Please don't just yet ask when a patch will be produced, we will post this information in due time.Now, under "normal" conditions, this is when VNAV will not engage / disconnect- PATH : speed is over 20 knots above current target (real life : 15, but I relaxed it a bit). You will get the DRAG REQUIRED when speed is more than 10' knots above target.- Bear in mind than in VNAV PATH the aircraft will follow the path in priority. The speed *is to be managed by the pilot* with the airbrake - real life, throttles also, impossible here -, if configuration implies the aircraft speeds above target.- if the angle to be flown (inserting an alt constraint for instance) in greater than 7 degrees, VNAV should and will disconnect- if there is a wpt with a speed restriction and no alt restriction- if next alt (constraint or MCP) to be reached is under the AC in CLB or above it in DES- if because of entering a too high cruize alt the path can not be constructed (no time to climb and descent etc.)Other considerations on DES PAGE- VB is relative to the next wpt, not the angle the aircraft should fly at all times. It will only be the same on a leg where there is no decel, because decel implies a shallower angle in time to decel before wpt.- VS is VS to take you to next wpt, not current VS target, for same reasons as just aboveOK, stay tuned !anthonyanthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

Hi AnthonyGreat to see you have narrowed down the problem. I would like to hear your opinion about the VNAV disconnetion though. As it is right now, it will disconnect to NO pitch mode. As I understand the A/P should, in case of above mentioned violations, disconnect to CWS. If so, is this something you can implement in the fix?TGIF :-beerchug

Hi Anthony,Great a/c! On the V-NAV issue, are there settings or limitations that we can use temporarily (even if they are unrealistic) until you get this patched, that would allow us to fly with V-NAV in the meantime without the concern of a disconnect?Thanks,Bruce.

>- if because of entering a too high cruize alt the path can>not be constructed (no time to climb and descent etc.)this could be avoided by implemeting the OPT/ECON Cruiselevel calulations on the FMC. Then the pilots can see what altitude the FMC recommend for the flight programmed into FMC.Jan Roar R

BruceMake sure no alt constraints in saved flightplans and your safe! (I think) + all above restrictions of course applies ;-)TGIF, :-beerchug

Hi Anthony and all!on my last flight (LIRF-EGBB) I had a strange behaviour of the FMC.I had no porblems of with VNAV disconections, however, the fuel predictions for TOD were zero while at the destination it was > 0.The distances were correct though (i.e distance to TOD < Destination).At some point (about 150nm from EGBB) the predictions reversed (fuel @ TOC > DEST) as they should.Additionaly I almost always have "ERR AT..." for my first wpt on the CLB page.Is this due to that calculation error or is it a separate issue?Did anybody else notice anything similar?best rgrds.//Michael

hi,hmmmmm the only probs Ive had so far are that the autopilot seems sloppy, rough and not as smooth as it was in fs2002, and the descents are a little steep (probably due to the descent calculation bug) but nothing spoilers can't handle.Andrew

Thanks, Mats.Bruce.

Quite right !But we can't - and thus haven't - model CWS for the time being.:-(anthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

no descent calculation bug---anthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

Anthony, what do you mean???I've been testing the CWS with good results! Push the CWS CMD button and the CWS cue lights up on the FMA and it works!! I remember the discussion here a while ago. And you were saying that it's not possible. But when I tried it and it worked I thought you guys wanted to surprise us? Maybe someone has surprised you as well? I can't be wrong here, I've actually flown using CWSConfused regards, :-hmmm

Michael"ERR AT..." I think usually means there is something wrong in the SID or STAR file (SID in this case). Can you please attach the file here so we can test it? And please share the flightplan as well and we can fiddle on our own machines as well. Cheers,

Based on the info in here, I`ve had a lot of successful VNAV flights. I hope it`s not mentioned before, but when the plane has initiated its descent mode, I still miss the "DES" inicated on the EICAS.

That is corrected now, no problem.It was a gremlin in the system.anthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

Some more info :In the coming patch (no, dont' ask), I've reduced target IAS VNAV speeds as follows on request of Vangelis.climb 290 .755cruize 295 .755descent 280 .755Later on (no don't ask) we'll have a comprehensive and very realistic cost index function that will affect those numbers very realistically.cheers,anthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com