Sign in to follow this  
Guest Andrea

PMDG 737-700 takeoff and climb speed

Recommended Posts

Hi PMDG,here it is a question for you:At Heathrow airport (EGLL 09R) with an aircraft load of ZFW=50845 Kg, Fuel=9400 Kg and flaps 5, I've the following calculated takeoff and climbing speed values:FMC N1 LIMITTO-1 DERATE activeCLB-1 DERATE activeFMC TAKEOFF REFFLAPS 5VR=133 KnotsV2=135 KnotsFMC CLBSPD REST 173/FLAPS (which is the climbing speed restriction with flaps 5)MCPSPEED 155 Knots (which is V2+20 Knots, manually set by me)and have the following behaviour:a) imediately after takeoff (positive climb rate) MCP SPEED value is hold at 155 Knots (manually set) and so does indicate PFD magenta Speed Bug.:( when I press A/P ENGAGE CMD A: SPEED value changes to 175 Knots and so does indicate PFD magenta Speed Bug (from where does FMC take this value I don't know)c) when I press VNAV: SPEED value changes to 173 Knots (which is the speed restriction with flaps 5 SPD REST 173/FLAPS) in PFD magenta Speed Bug and MCP SPEED indicator becomes dark.The question is: from where does FMC take the value of 175 Knots when I press A/P ENGAGE CMD A ??? Shouldn't it be equal to 173 Knots which is the SPD REST 173/FLAPS ???Andreahttp://www.precisionmanuals.com/images/forum/800driver.jpg

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

>The question is: from where does FMC take the value of 175>Knots when I press A/P ENGAGE CMD A ??? Shouldn't it be equal>to 173 Knots which is the SPD REST 173/FLAPS ???When you engage the autopilot on takeoff the first thing it does is bump up your MCP speed by 20 knots. You should have set your MCP speed to V2, not V2+20.Finally, only VNAV mode offers flap speed adjustment. So when you went to VNAV, your FMC commanded the 173 knots.What you should have done was set MCP speed at v2 - 135.Then when you hit CMD A, it would have automatically gone to 155. Then when you hit VNAV, it would adjust to 173 and so on as you retract the flaps.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this