VNAV does NOT keep Speed (overspeed or below 200 kt)

[Guest romano]

VNAV engaged, while flying at cruise ALT (..say at FL350),at cruise speed according FMC (ex.M 0.86),after 10/15 minutes of cruise, it starts OVERSPEED ALARM (over 340 kt) or in some othet cases,using airbrakes, speed drops below 200 kt ,befor stalling allarm..IMPOSSIBLE to fly it.ByeRomano

[Guest NormanB]

Romano,The real 777 also is subject to overspeed.A couple of things for you. * What Cost Index are you using?* Whats your ECON Cruise set as?* Which version of FSUIPC are you using? (A new version came out yesterday fixing a winds bug)

[Guest romano]

Cost Index 90Econ Cruise ...?not touched!Fsuipc 3.53In Flight wind 40-60kt (head / side) At cruise level, after 10-15 min ,SPEED becames very UNSTABLE, ups and downs of 20kt...and starts OVERSPEED alarm ,when overtake limits.In the other way round, SPEED can drops to 220kt or more( while cruising at FL350!!)down to STALL warning.In this conditions it is NOT flyable.Thanks for answer anyway.

[Guest romano]

Is it possibly due to Force feedback Joystick (Logitec Wingman Force 3D)???byeRomano

[psolk 3,037]

Are you using ASV? If so make sure you are using ASV6 and have the force constant temperature and pressure features enabled. The only time I have ever seen this was with ASV and it was the FSUIPC issue that Norman mentioned earlier and has since been resolved.-PaulLiquid CooledAMD 4000 San Diego2 Gigs Kingston Corsair XMS CL2Dual 7800 GTX 24 inch widescreen dual 19 inch LCDRaid-0

[Guest romano]

Yesss, I'm using ASV 6.I'll try your suggestion to enable "force constant temp and press"thank you romano

[psolk 3,037]

You should also use a registered version of FSUIPC. Under wind smoothing the magic settings are 0 in the top field 5 in the middle and 8 in the bottom. This tells FSUIPC to apply 1 kt wind change every 5 seconds opposed tot he default which is 5 kt wind shift per second. Slowing it down helps tremendously,-Paul