Hi guys! I need help regarding on my descent. As i start my descent using VNAV from ToD, my speed getting increase more and more and end up into overspeed. I tried to avoid using speedbrakes unless there's a tailwind. Can anyone help me how to control my descent speed and without using speedbrakes? And one more question! At what altitude is the most suitable to start extending the flaps? Thks!

 

Joel

Again I suggest you read the manual.

 

PMDG have their own forum right here on AVSIM under the 'Commercial' section.  Therefore any specific questions you have would best  be posed there.

There are two types of VNAV descent....PATH and SPEED.

 

VNAV SPEED is very similar to Level Change and will use pitch to maintain the speed selected in the VNAV page.

 

VNAV PATH will follow a vertical path that is calulated and will observe any altitude constraintsset in the Legs pages. Although it projects a descent speed, and will add power if speed drops, it is up to you to monitor any overspeed, and use spoilers if neccesary.

 

For the PATH to be accurate you need to enter the descent wind projections in the DES page.

 

It is also important for your descent profile to be accurate. If you have unrealistic altitude constraints in the legs pages, the aircraft will be unable to both follow the path and stay at the desired speed. It is simple physics.

When your descent speed tends to be too much, are you sure your engines are idling?

 

Sometimes it is necessary to anticipate a short descent route and request from ATC a lower altitude earlier than anticipated. Also plan on reducing speed earlier. Use the descent ARCs on the Enhanced Nav Display (EHSI - Enhanced Horizontal Situation Indicator) and take over vertical nav using the V/S on your MCP.

 

A steep descent may be necessary when there are obstacles in your flight path.

 

Are you getting the message DRAG REQUIRED on the FMC CDU?