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uhntissbaby111

Green flap speed bugs

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From what I understand, the green speed bugs display the maneuvering speed for the indicated flap position. And maneuvering speed is the maximum speed at which the aircraft will stall with full control deflection before structural failure occurs, in theory at least. And it seems standard SOP on approach to select the the next flap setting at the current flap setting bug. For instance, when you hit the green 1, you select 5, so on and so forth. My question is, if the bugs show maneuvering speed, why would you select the flap when you are above that speed?

 

Adam

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I don't have access to the manuals at the moment but iirc the green placards are only used for flap retraction on departure.

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I believe, and don't quote me here, but:

 

During descent, the green pointers indicate their respective flap extension speeds (as preferred by the FMC). Sure, you could extend them above than the green pointer (e.g Flaps 1 is anywhere below 270 knots, but the pointer might be sitting well below that), but it would be most efficient (again, I'd rather not be quoted, I'm here to learn too) if you used the green pointers. That's AFAIK anyway, I may be completely and utterly wrong for all I know :P

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I believe you are confusing design maneuver speed (Va) with flap maneuver speeds. The green bugs are flap maneuver speeds and not design maneuver speed...

 

The flap maneuver speed is the recommended operating speed.

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The flap manoeuvre speed is the minimum speed for that flap setting. It allows for the higher stall speed while manoeuvring. You can fly higher speeds.

 

It has nothing to do with the use of full control deflections or structural limits.

I don't have access to the manuals at the moment but iirc the green placards are only used for flap retraction on departure.

They are used for flap extension too.

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I believe you are confusing design maneuver speed (Va) with flap maneuver speeds. The green bugs are flap maneuver speeds and not design maneuver speed...

 

The flap maneuver speed is the recommended operating speed.

Flap maneuvering speeds are speeds that you are recommended to not fly slower than for the given flap configuration. This speed provides adequate stall protection while performing "full bank" turns.

I quoted the other person because his response is a good one.

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From what I understand, the green speed bugs display the maneuvering speed for the indicated flap position. And maneuvering speed is the maximum speed at which the aircraft will stall with full control deflection before structural failure occurs, in theory at least. And it seems standard SOP on approach to select the the next flap setting at the current flap setting bug. For instance, when you hit the green 1, you select 5, so on and so forth. My question is, if the bugs show maneuvering speed, why would you select the flap when you are above that speed?

 

Adam

 

I believe you have to take into account the travel time of the flaps as well...

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Flap maneuvering speeds are speeds that you are recommended to not fly slower than for the given flap configuration. This speed provides adequate stall protection while performing "full bank" turns.I quoted the other person because his response is a good one.

  

I believe you are confusing design maneuver speed (Va) with flap maneuver speeds. The green bugs are flap maneuver speeds and not design maneuver speed...

The flap maneuver speed is the recommended operating speed.

Both good answeres and here is link on how to use the flap schedule:

 

http://forum.avsim.net/topic/371793-typical-777-flaps-selections/

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The flap manoeuvre speed is 1.3x stall speed for that setting. This allows to be in a 30 degree bank and still have room for vertical changes.

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The flap manoeuvre speed is 1.3x stall speed for that setting. This allows to be in a 30 degree bank and still have room for vertical changes.

Nope, you are talking about the MINIMUM flap maneuver speed = top of amber bar = 1.3x Vstall.

From the top of the amber bar downward, maneuver capability starts to reduce from where 40 degrees of bank (25 + 15 overbank protection) would activate the stick shaker down to the black/red bar where zero bank even activates the stick shaker

 

The green flap symbols are "flap maneuver speeds" (not minimum flap maneuver speeds) and like Charles Carter said they provide a much greater margin to stall speed.

 

See FCTM (flight crew training manual)/General/Maneuver speeds and Margins for more detail.

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