When i go to put in my V Speeds for a flight, it sometimes wont show up automaticlly, but after i change the weight and the ZFW, the V Speeds appear. Whats wrong?

Likely (more-so on a de-rated takeoff) the speeds needed would be outside the parameters for the combination of runway length, weight, and temp.

 

Since there is no Topcat profile for the T7 yet I play with the settings for de-rated takeoff/climbs and if I de-rate and I get no V-Speeds its because there wouldn't be enough runway for the takeoff at reduced thrust.  And if not de-rated then simple the runway could be to short.

Likely (more-so on a de-rated takeoff) the speeds needed would be outside the parameters for the combination of runway length, weight, and temp.

 

Since there is no Topcat profile for the T7 yet I play with the settings for de-rated takeoff/climbs and if I de-rate and I get no V-Speeds its because there wouldn't be enough runway for the takeoff at reduced thrust. And if not de-rated then simple the runway could be to short.

Not true. Calculated Vspeeds does not take runway length into account. Make sure the initial pages are re-executed.

You need your performance data entered and the departure runway selected. Furthermore, T/O speeds don't show until the ADIRS is fully aligned.

Not true. Calculated Vspeeds does not take runway length into account. Make sure the initial pages are re-executed.

 

Eh? How are balanced field calculations done without it? And the PERF INIT page doesn't require execution.

 

 

How are balanced field calculations done without it?

 

Balanced field calculations are always done without it... by definition.

 

Balanced field is such a field, that in case of V1 cut, go-distance and stop-distance are the same. For every given set of ATOW and actual available thrust (incl. derates and enviro factors), there is only one such V1 and field length. 

You need your performance data entered and the departure runway selected. Furthermore, T/O speeds don't show until the ADIRS is fully aligned.

 

This is the post that answers the OP.

• Performance Data (Weight, temp, derates, flap selection etc)
• Departure runway selected
• ADIRS Alligned

any one of those 3 missing, the Vspeed autofill will be missing.

 

This is different from NGX, where the IRS didn't have to be completed alignment for the data to be inserted.

Balanced field calculations are always done without it... by definition.

 

Balanced field is such a field, that in case of V1 cut, go-distance and stop-distance are the same. For every given set of ATOW and actual available thrust (incl. derates and enviro factors), there is only one such V1 and field length.

Whoops. I was thinking derate.

 

So why does the FMC need a runway selection?

It's all about filling the correct info into the FMC.  If info is missing or the execute not executed then there will be problems with V Speeds and configuration settings.

 

Read the manuals that accompanied the aircraft.

 

Rob

Whoops. I was thinking derate.

 

So why does the FMC need a runway selection?

 

At least for heading information that combined with wind info will affect v speeds.

At least for heading information that combined with wind info will affect v speeds.

 

*face palm* thanks, should have known.