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psolk

Weird VNAV issue in air from ksfo-kewr right now

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OK,Thanks for reading,I have done a few long hauls already without any issue. Last night I did YSSY-KSFO with no issues at all, 14 hours total. Today I loaded up for the trip from KSFO back to KEWR. I have seen the posts on retracting and then extending flaps 1 but I had normal flap retraction. I engaged VNAV passing 10000 and nothing happened. I looked down and noticed VNAV was on the PFD but in white and V/S was still in green. No matter what I did I could not get VNAV to engage. I have now performed a manual climb to 350 using v/s but no matter what I do I can not get VNAV to engage. On the VNAV page of the CDU the speed is in white and will not go magenta. Right now my PFD shows SPD LNAV and ALT in green with VNAV under ALT in white. I have never seen this before. Anyone got any suggestions? Obviously I can fly how I am right now but something is wrong for me to not be able to get that speed to go magenta in the CDU and VNAV not to engage?Any help would be appreciated, I have tried disco of the F/D A/P and A/T but as soon as I re-engage the F/D it automatically sets ALT active.Thanks in advance,-PaulEdit: On the Prog page, ECON SPD is blank and I have no T/D as well... I went through my usual 45 minute startup procedures and checklists without any variation.

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So I tried everything and finally fixed it. I had no discos and my legs pages were complete, however I took my CF04R waypoint and inserted it before the sweet waypoint and all of a sudden everything worked. ECON SPD went magenta and VNAV engaged. I promise and swear I did not have a disco. That was one of the first things I checked and it was repeatedly checked during my troubleshooting. I wonder if there is something with the f/p? This is the second time it happened with this plan and like I said, I have done a bunch of other long hauls without any issues. If I can replicate would someone on the PSS team take a look at the flightplan?Thanks,-Paul

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obviously this is a known issue, probably one of the major shortcomings of this ac, this VNAV issue, till its address the 777 is sitting in my hangar.

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Hey Clayton, I have done a bunch of flights with her and this is only the second time I have run into this. (both with the same flightplan) I know there is the flaps retraction issue but this was different. I am going to see if I can replicate it again today with the same flight plan. If so, I would guess it is something to do with NavData and a waypoint in that plan. It does appear you can workaround the VNAV issue by moving your CF waypoint up in the flightplan. That is what did it for me, VNAV re-engaged and I flew the rest of the flight flawlessly with VNAV engaged. It had something to do with the legs and the flightplan in my case...-Paul

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OK, I was able to reproduce it again. I am still flying the route, I once again was able to resolve the issue by moving CF04 up a few spots on the legs pages. This time VNAV kicked in as soon as I moved CF04 to the HAYDEN waypoint. It is like you can jump-start VNAV again by moving the final two waypoints up a few spots. I am really thinking it is something to do with a waypoint on this flightplan. Possibly VNAV has a problem if there is a waypoint it does not recognize. Can I send my F/P to someone at PSS for them to try?Thanks in advance,-Paul

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CF04 was the last waypoint before my ILS4R approach. You would not actually move the CF04 waypoint but whatever that waypoint is in your f/p. Just move it forward a waypoint at a time until the VNAV can compute again. I have been able to re-establish VNAV every single time by manipulating the f/p in flight.-Paul

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Hey Clayton,Just an FYI, I just had this happen again and confirmed this is a definite work-around. Move a leg up one in the cdu, it will re-compute and VNAV will re-engage.Just thought I would let you know,-Paul

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Hi Paul,I was searching this forum for issues like what I had yesterday when I saw your posting.I had the same issue but with a possible additional issue (which is already in the list of bugs). My issue is slightly different though:I was flying from Vancouver Intl CYVR to Mexico City Benito Juarez Intl MMMX with the 772LR with a flightplan made in FS2004 and imported into the CDU. I have previously reported that altering the FIRST waypoint on the CDU caused a complete lockup of FS2004 but now, altering SEVERAL waypoints near the end of the flight plan to introduce altitude and speed restrictions locks up FS (not the first one - I don't touch this knowing of the freezing issue it already has). However, it does NOT lockup after altering the first waypoint alt/spd but after altering a particular waypoint - CD05. Here is my flight plan with the altered waypoints marked with an asterix:CYVR YVR RADDY YKM(116.00) PDT(114.70) TWF(115.80) TCH(116.80) JNC(112.40) FMN(115.30) TCS(112.70) DEL(113.50) TRC(116.40) SLP(117.20) D250G*** THEN THE DESCENT PORTION OF FP WITH SPEED/ALTITUDE RESTRICTIONS WHICH I ENTERED SHOWN IN SQUARE BRACKETS:*PTJ(114.50) [270/16000]*RADEL [260/14800]*SMO(112.10) [250/12000]*MALPA [200/10000]***CD05 [180/9000]*** ==> LOCKS UP FS2004 modifiying here*MW(370.0) [160/8300]MMMX (the airport)No matter WHEN I modified the above-mentioned waypoints in the descent portion marked by asterix * , no problems occurred UNTIL I got to CD05 which is not even the last waypoint. I thought modifying any waypoint except the first one was working until yesterday. I did NOT use the DEP/ARR button in the CDU but manually inserted these waypoints into the flightplan made in FS2004 using the FS flightplanning map. I lost a good 60 minutes restarting FS2004 3 times and then another problem occurred: VNAV would not engage and I had the same issue as already reported on this thread. I could manually vary speed using the MCP but TOP OF DESCENT disappeared after I had entered restrictions on the above legs BEFORE the CD05 leg at which the CDU froze - so modifying the leg speed/alt caused VNAV to disengage permanently.I had flown two ultra long-haul flights last week with the 772LR from Montreal to Hong Kong (CYUL - VHHH) and I am pretty sure I had modified the speed/altitude restrictions on the final legs without any problems at all.I hope the above info is of some help to PSS in resolving what looks like major CDU issues on the 777 series.John

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I just tried a test flight with no weather at all, using FS2004 clear weather theme, from Buenos Aires Ezeiza SAEZ to Miami Intl KMIA with the 772LR and here are the results:FS2004 froze when altering CDU LEGS paramets for the last ILS approach legs. I had initially entered different legs for the ILS approach to runway 30 at KMIA and changed the speed/altitude restrictions without any issues. During flight, after passing several of my waypoints and accelerating simulation to 16X without any problems of bobbing up&down, I slowed acceleration to normal time, climbed from 34,000 to 36,000 feet and leveled-off at FL360, to continue my step climb to my final cruise altitude of 38,000 ft. Then decided to change the final legs for the ILS approach to the runway 27 approach legs, simulating a change in weather and winds. I deleted the first of the legs and FS2004 froze.That's it. The last time my flight froze, the route was a completely different one with real weather using ACTIVE SKY 6, from Vancouver to Mexico City so this proves that this freeze when manipulating CDU legs is not route-dependent.Furthermore, I had done a flight last week from Mexico City MMMX to Buenos Aires SAEZ with the PMDG 744 and altered and added LEGS in the FMC many times without any issues. The LEGS added on the 744 FMC were also the same final ILS approach waypoints...so this only happens with the PSS 772.Does anyone from PSS know if this is a known issue which will be addressed in the patch?John

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