Before the FAF fix When I enter a value for flap/Vref value for wind correction of half headwind, when selecting flaps 1 the managed speed drops from 19x to 18x as if its subtracting the wind component. I thought it was supposed to add the wind component of the flap/Vref speeds ? Can anyone confirm or have I mis understood something here ?

 

Thanks

Voj

Not exactly. Vref is determined by FMC according to estimated landing weight. Nothing to add or subtract here. Most normal weight landings use Flap 30 and its corresponding Vref. Short field or heavy weights may need to use Flap 40 and its correspondingly lower Vref.

 

Now then the final approach Vapp is calculated FROM Vref as follows:

 

Vapp = Vref + 1/2 headwind component + gust but Vapp never to exceed Vref+20 or be less than Vref+5.

 

Vapp is held throughout the approach (minor adjustments for variable wind) until aircraft is over threshold at which time it is slowed to Vref for touchdown.

 

You were close but just had Vapp confused with Vref. Hope that helps.

Vapp is held throughout the approach (minor adjustments for variable wind) until aircraft is over threshold at which time it is slowed to Vref+Gust Factor for touchdown.

Small point, but great explanation.

Oops! Thanks, Matt. I originally put that in but I went back to edit a misspelled word and retyped that line inadvertently leaving it out and never noticed. Glad we have you around.

ok, thanks for that info.

So when I enter Flaps 30/1xx for landing in FMC, should I not edit the flap30/1xx speed value ?

I am confused with what the default +05kt correction does or whats it displayed for.

 

Is that the value that is changed for correction and not the flap/speed FMC data ?

or

Would I just enter the correction for speed on the MCP speed window which then overides the FMC value ?

When I enter flaps 30 for landing on FMC and dont edit anything in the FMC for any correction, flying the approach in Vnav selecting Flaps 1 a see a managed speed on speed tape of around 19x.

If I enter/change the flap30 speed in FMC to add the corrections, that's when I see the speed tape drop to 18x for flaps 1.

What am I doing wrong when entering the wind corrections ?

I enter the correction as per this vid. And when I do this, I get a decreased value displayed on the pfd speed tape when left in managed mode and working down with the flaps until landing flaps are selected.

Is that correct ?

 

http://www.youtube.com/watch?v=_y2CIqQpt7A

the subject is well explained into Flight Crew Training Manual that gives you also some examples...

 

Ciao

 

Andrea B.

Don't do what that video was doing.

 

Simply hit the LSK for the Flap setting twice. That should fill the Ref box. If your wind correction is greater than 5knots, fill in the wind correction box.

Don't do what that video was doing.

 

Simply hit the LSK for the Flap setting twice. That should fill the Ref box. If your wind correction is greater than 5knots, fill in the wind correction box.

Ok, will give that a go next time.

Cheers