White pointer on speed tape question

[Bobsk8 12,722]

On the NGX speed indicator I always see a white pointer when I am on approach. It is somewhere around 140-150 knots, and seems to stay at one speed. I cannot find anywhere in the documentation the meaning of the pointer, and I have looked everywhere. Any help would be appreciated. 

[downscc 1,327]

Try FCOM pg 10.11.8 Item #8 VREF+20.  Keep trying and eventually it gets easier to find things.

[Alpha Floor 237]

 

 

Keep trying and eventually it gets easier to find things.

 

Sometimes it's difficult to find what you're looking for, you don't know at first if you have to check FCTM, FCOM V1, FCOM V2... And within FCOM V2 if it's System Components or System Description etc..

 

It is intimidating at first of course. As Dan says, takes some practice to get used to. That or Ctrl+F, hehe.

[Bobsk8 12,722]

Try FCOM pg 10.11.8 Item #8 VREF+20.  Keep trying and eventually it gets easier to find things.

 

Thanks, I tell you, I am good at reading and searching, but somehow I missed this........I totally forgot about the FCom.....

[Guest]

Hi Bob

 

That white pointer can represent two different things.

 

On take off the white bug represents V2+15. After take off and above this speed you'll have maximum manoeuvrability (Up to 40 degrees bank angle) for all take off flap settings. FCTM also advises to limit bank angle to 15 degrees if below V2+15. Also if you take off with F25 the white bug (V2 +15) is the flap retraction speed for selecting F15.

 

 

As everyone else has told you correctly on approach the white bug represents VREF+20. FCTM and our operator states this should be our maximum allowable airspeed for the approach. For a stabilised approach one of our criteria at the landing gate (500ft in VMC, 1000ft in IMC) is for the speed to be between VREF and VREF+20 and if not correcting to that speed we go-around. 

 

Hope this heled!

[Driver170 42]

V2+15. Also if you take off with F25 the white bug (V2 +15) is the flap retraction speed for selecting F15.

 

So what relationship has the white bug got with the flaps?

[Bobsk8 12,722]

Hi Bob

 

That white pointer can represent two different things.

 

On take off the white bug represents V2+15. After take off and above this speed you'll have maximum manoeuvrability (Up to 40 degrees bank angle) for all take off flap settings. FCTM also advises to limit bank angle to 15 degrees if below V2+15. Also if you take off with F25 the white bug (V2 +15) is the flap retraction speed for selecting F15.

 

 

As everyone else has told you correctly on approach the white bug represents VREF+20. FCTM and our operator states this should be our maximum allowable airspeed for the approach. For a stabilised approach one of our criteria at the landing gate (500ft in VMC, 1000ft in IMC) is for the speed to be between VREF and VREF+20 and if not correcting to that speed we go-around. 

 

Hope this heled!

 

Excellent. I was trying to figure out why the Vref plus 20, and now you explained it. 

[Driver170 42]

You should retract flaps to f15 and maintain white bug + 5kts this 5kt margin is required to obtain an approach speed equal to vref F15 in order to provide adequate maneuver margin. To avoid tail strike and incase of go around.

 

Found this...

 

 

The “white bug”.

 

On takeoff the white bug is automatically set to V2 +15 and on approach to Vref +20.

 

At takeoff and speeds above white bug, the aircraft has FULL maneuverability and is provided when the airplane has accelerated to the recommended maneuver speed for the selected flap position. This means up to 40° AOB, i.e. 25° AOB + 15 overshoot upset. When below white bug, it has LIMITED maneuverability to 30° AOB i.e. 15° AOB + 15 overshoot. The bug disappears at the initial flaps retraction after takeoff or when VREF is selected in the CDU.

 

On approach, when at normal landing flaps are set and above Vref, the aircraft has full maneuverability. However in the event of a G/A, and the Flaps are retracted to 15, the full maneuverability & limited maneuverability criteria apply to the white bug again. This is because Vref 30 (& Vref 40 + 5) = V2 F15, and thus the white bug is V2 F15 + 15, and equals the takeoff case as if a F15 takeoff. (This is also why the magenta CMD speed bug automatically moves above the white bug as the Flaps are retracted to F15 for a 2 engine G/A).

 

In the case of a single engine approach Vref 15 = V2 F1. Thus in the G/A the same limits on Bank Angle apply as the Flaps are retracted from F15 to F1. In this case the magenta speed bugs stays at Vfly to give best Rate of Climb up to1000 ft. (Note the QRH saying bank angle limited to 15° for a single engine G/A until at safe speed)