vhrob

V Speeds will not populate

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I am trying to fly the 1.5 tutorial in FSX SE.

I have followed pages 32 and  37, requesting and accepting the Perf Init data, inserting flaps and confirming CG. However, the V speeds are blank and do not appear when clicking the LSKs. Also, it will not allow me to manually insert the V speeds. "Invalid Entry" is the message.

Is there any possible thing I have overlooked?

Rob

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Have you selected a Departure RWY and also entered the ZFW, Cost Index in the Perf Page?

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Tony,

Yes the ZFW and the CI have been entered. Departure runway has not been entered because the tutorial specifically says not to enter this until later.

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I have just entered the runway on the Dep/Arr page so my CDU looks exactly the same as p 37 of the tutorial, but V speeds still not there.

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4 minutes ago, vhrob said:

Tony,

Yes the ZFW and the CI have been entered. Departure runway has not been entered because the tutorial specifically says not to enter this until later.

You should enter a runway for the V speeds to be available. The tutorial says that rnw 30 is assigned via the PDC message

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1 minute ago, vhrob said:

I have just entered the runway on the Dep/Arr page so my CDU looks exactly the same as p 37 of the tutorial, but V speeds still not there.

You are definitely missing a step. Without pictures of the various FMC pages we can only guess

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My browser won't allow pasting of screenshots! 😠😠😠

I will start the whole thing over again and see what happens.

 

 

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As others have stated you MUST have the departure runway entered to get auto v speeds. The FMC needs to know runway direction to calculate speeds from prevailing winds. 

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2 hours ago, sloppysmusic said:

As others have stated you MUST have the departure runway entered to get auto v speeds. The FMC needs to know runway direction to calculate speeds from prevailing winds. 

More importantly it needs to know runway length to calculation V1 for Vgmc

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1 hour ago, downscc said:

More importantly it needs to know runway length to calculation V1 for Vgmc

That's interesting as I didn't think it made a difference to the actual speeds. I've done a few hundred take offs recently and in the same plane with max load v2 has been the same each time regardless of runway length. I know v2 is engine out climb speed and v1 is last chance to quit the takeoff but I've never seen v1 higher than v2 which it surely would be on a long runway with a light load. V1, vr and v2 always seem very close and in same ratio and order. In fact on some runways it's possible to take off and land TWICE in a lightly loaded jet. I've always thought v1 was not actually related to runway length because of this but instead was the last speed before the plane starts to lift and brakes would have little effect until slats had slowed plane down again. Will have to do some more testing. Another issue is that in the sim at least it's perfectly possible to select a runway you have no chance of taking off from. Like a 2000 ft runway in a 737-700. You will get your v1 speed as usual but you will never get up to it! There is never any warning at all that runway length is too short to take off from. 

This is one of those grey areas I always wondered about. 

Edited by sloppysmusic

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I've not played with it directly and others are much more versed on this than I. The minimum V1 is set by either the ground minimum engine out control speed Vgmc (any slower and you loose control in event of engine out) or the balanced field length defined in regulation. V1 can equal Vr in certain conditions and it will never be greater than Vr.

Hopefully if the runway is too short the FMS fails to provide V speeds.  I've seen this occur such as when I've guessed at too much derate (if my memory is correct, which is not an even bet).

 

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Another reason for the OP's issue could be that the IRS are not aligned.
I believe that FMC will not calculate takeoff speeds until the IRS are fully aligned.

  • Upvote 2

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52 minutes ago, Budbud said:

Another reason for the OP's issue could be that the IRS are not aligned.
I believe that FMC will not calculate takeoff speeds until the IRS are fully aligned.

correct

 

Rob,

even if the alignment time has run make sure that you enter the GPS position (or last position) on the POS INIT page. 

I believe you need to go to this page manually as soon has you've entered the RTE or PERF page once. 

INDEX --> POS

Edited by Ephedrin

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