A320 V speeds

[Boyington]

Why is it that in the Octupus speed charts of the A320, the V Speeds for a lower Takeoff weight is higher than that for a higher takeoff weight, all other conditions and limitation codes being the same.

[MD80rookie]

Could you attach the chart for reference?

[tubby linton]

To improve performance the speeds are adjusted/optimised to give a higher V2 . at higher weights you are seeing the "real" speeds.
http://www.pprune.org/tech-log/413214-a320-optimized-v-speed.html

[Boyington]

In the Octopus charts for some fields on the A320 the V speeds for a lower weight are higher than that for a higher Take off weight, all other conditions like limitation codes etc remaining the same. Why is it so?

[Cough]

Briefly - Increased V2 climb.

Having a higher V2 can lead to greater flex temps. When you are light you can accelerate to the higher speeds in the runway length hence use a greater flex.

When heavier, you can't accelerate as quickly, so the flex temp falls rapidly as engine thrust compensates for aerodynamic inefficiency.

[vilas]

Boyington
In this case you are obstacle and brake energy limited.


To reduce take off distance you should increase V1 but V1 is limited by MAX brake energy speed.
The brake energy limitation depends on weight and thrust.
When OAT increases the weight and the thrust decrease.
When OAT increases, MAX V1 limited by MAX brake energy speed increases.