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A_Pilot

Takeoff V-Speed problem

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I'm befuddled at the function of automatic v-speed calculation because for a full power take-off, flaps 20, on a 14,000 ft runway it's not giving me any V-speeds suggestions. Or am I asking too much of the plane?

 

Luc

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Are you filling out all of the take off pages? Did you identify a departure runway?

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Yeah, as far as I can tell, I'm filling them in just like in the tutorial, but for my own flights now. It's hit or miss whether it works or not. Runway winds and everything. What I have changed since it worked was use the ActiveSky 2012 wind request feature. Additionally, when this happens, the Route page prompts me directly to the Takeoff page, and not the Thrust Limit page, and subsequently the Takeoff page prompts me to the POS INIT page

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Yup. I choose my takeoff thrust setting on Thrust Limit first, then input runway winds on page 2 like the FCTM suggests, then the flaps (usually 20 while I try to get this to work, but I've also tried 15 with no luck), then the CG using the double-click of L3 technique. Sometimes it works, sometimes I get "V SPEEDS UNAVAILABLE" (which to me means it's working, i just suck at guessing derated takeoffs), and sometimes I get nothing


A full flightsim reset does make it work again, as I just found out. But that's kind of a nuisance what with how FSX works with AS2012. Maybe I just get to learn to deal

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Does it calculate Vspeeds at other flap settings?

 

If not....you need to press "ON" (on the CDU page where the Vspeeds are displayed) so that the FMC actually caculates those speeds.

Otherwise it will not.

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If you fill out the departure Rwy and performance pages she will calculate V speeds. Have you double checked? OAT (Temp) is a calculation component that is often overlooked. Also, Flap 5 & 15 are normal settings for the 777- not 20.

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Just remember that one of the conditions for auto v-speeds is that the ADIRU is alligned (as someone mentioned above).

 

 

Displays dashes when:
• required information not entered
• performance calculations are inhibited
• ADIRU is not aligned

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Does it calculate Vspeeds at other flap settings?

 

If not....you need to press "ON" (on the CDU page where the Vspeeds are displayed) so that the FMC actually caculates those speeds.

Otherwise it will not.

 

 

+1: You have to confirm the calculated v-speeds by clicking on the corresponding LSKs on the right hand side. By confirming them they are transferred to the PFD speed tape.

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As James says above...make sure the ADIRU is on/aligned (overhead panel).

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Sometimes it works, sometimes I get "V SPEEDS UNAVAILABLE" (which to me means it's working, i just suck at guessing derated takeoffs), and sometimes I get nothing

 

It hasn't been clear in your posts, so I'll point this out anyway:

Ensure that you are entering the runway on the DEP/ARR page, regardless of if you are flying a SID.

 

Also:

You may be getting this because the aircraft is calculating that you cannot take off in the available amount of runway, due to weight.  If you're trying to take off with the default load, and default fuel (full tanks), this will probably often be the case.

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I had the same issue, because I was attempting to use a fixed de-rate AND assumed temp on a fully loaded 15 hour flight out of OMDB.  I changed the de-rate from TO1 to TO and left the assumed temp in and it computed the V speeds. 

  • Upvote 1

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I just had this issue when using TOPCAT 2.74Beta to calculate my derate.  On the Flaps -> Optimum setting, it recommended Flaps 20 for me, which the 777 doesnt like apparently.  I had TOPCAT recalculate using Flaps 15 specifically and the FMC gave me v-speeds.  

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Which B777? TOPCAT does not have 300ER performace tables, which is the reason I ask.

 

I've used F-20 TOPCAT and 200LR on several occasions with no problem.

 

By the way, please use your full name in posts to the PMDG forum, thanks.

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