Good night! Guys, I'm having problems with the PATH DESCEND. The plane descends to a particular waypoint where the FMC programmed with the speed is 170kt for example, but it does not reduce to 200kt, sometimes even increases the speed. What can be?

Got any FMC messages beforehand?

The FMC INFOM shows a message that a certain sum shall be accomplished in kts X, and also gives a message every hour DRAG REQUIRED.

The 800 model is very "slippery" and often is difficult to slow and if drag required is show then use the speed brakes.

Good night! Guys, I'm having problems with the PATH DESCEND. The plane descends to a particular waypoint where the FMC programmed with the speed is 170kt for example, but it does not reduce to 200kt, sometimes even increases the speed. What can be?

VNAV Path DescentAn E/D point must be defined in order to accomplish a path descent. It may bedefined manually or by the selection of an arrival procedure.The FMC defaults to the path descent mode for planning purposes. If thenecessary information for a path descent is not available by the time the airplanereaches the T/D point, the FMC will revert to the speed descent mode.The path descent normally begins automatically at the calculated T/D point,provided the MCP altitude is reset for the descent. If descent is not initiated by theT/D, a path descent may not be achievable. At the T/D, the FMC commands idlethrust and pitch to follow the descent path.The descent complies with waypoint altitude restrictions by following thecalculated vertical path.Note: A path descent uses the target speed for planning purposes only. There isno attempt to maintain the target speed during the idle portion of thedescent.Note: When descending in VNAV PTH, the FCC will disengage VNAV andswitch to LVL CHG if actual speed becomes equal to or slightly less thanthe minimum speed, denoted by the underspeed limiting symbol in theMCP IAS/Mach window. This can also happen in turbulence or gustyconditions when the minimum speed may momentarily increase due to Gloading. See section 4.20, Minimum Speed Reversion.