Performance A320F

[StrIA]

Why speeds are greater on FLEX, then on TOGA? (take off phase)

[vilas]

Are you sure?

[tubby linton]

Sample performance-
Conf 1+f IAE powered A321 TOW 80T
Toga V1 134 Vr146 V2 154 MRG 1152 Lim TOW Vmu
Flex 52 V 154 Vr 154 V2 156 MRG 1 Lim TOW-OBS

[Cough]

When you flex, the performance computation will use the spare runway to achieve higher speed (think improved v2 climb) to get further reductions in flex temp.

When you use TOGA there isn't any point as there is ample performance for everyday use. Hence you simply get fast enough to takeoff and then do just that!

ps. Why your V1 is low on the TOGA case may be a company preference...

[StrIA]

FLYSMART WITH AIRBUS (appstore)
For ex.
A321-211 TOW 78, wind-60/14,OAT-4,RWY-wet, CONF 2, AIRCOND-Off, A-ICE-Off
FLEX-52 153/161/161
TOGA 142/152/152

[compressor stall]

As Vilas says, it's not the case that they are always greater.

Does your flysmart app have just the TOGA and max flex option? If so, then you might get that assumption.

But if your admin has it set up so that you can see all the flex variants, pick a runway at low weights and good conditions and run it.

For my local airport on a 2300m runway, I have the V1,Vr,V2 speeds at TOGA, F43,F45,F47,F49 and F51 all the same, and all VMCG limited.

Then F53 and F55 have same V1, but the Vr and V2 start to increase (Vmcg limited)

F57 and F59 have V1,Vr,V2 higher than Flex (Obstacle clearance limited).

Remember also that the Flysmart app chooses a V1 that gives the greatest margin (unlike the old LPC where you could pick a higher V1 and reduced margin, which was handy in some locations).

[Lantirn]

Sample performance-
Conf 1+f IAE powered A321 TOW 80T
Toga V1 134 Vr146 V2 154 MRG 1152 Lim TOW Vmu
Flex 52 V 154 Vr 154 V2 156 MRG 1 Lim TOW-OBS

Nice example.

In this airport with those conditions you became obstacle limited in this flex 52.
To clear those obstacles the speeds were increased to facilitate obstacle clearance probably for the second segment of the takeoff flight path.

Improved climb.

But you have to know the limited codes.

[underfire]

A321-211 TOW 78, wind-60/14,OAT-4,RWY-wet, CONF 2, AIRCOND-Off, A-ICE-Off

Curious, OAT -4, RWY wet, and ice off?

Working on performance profiles for obstacles, I am curious as a guide, when you turn ice on.

[FlightDetent]

SAT 10 or less, visible moisture.

Wet with -4 entirely possible on a sunny morning after treatment had been applied overnight. Not so uncommon in StrIAs are of operation with high pressure airmass, late February.

[underfire]

ok, well, its November...

one could guess, or one could provide details on the assumptions.

Cheers