320,why do we hardtune;greendot'

[m&v]

Forgive the 'stale'320 question!!!
Why do we 'hardtune' the G/D speed on the 'Perf' page for takeoff???I can't find the reference immediately in the FCOM.
I only know we've always done it-is it to protect the 'speed'if one suffers a failure of the SRS programme after liftoff???

cheers up LBA :rolleyes:

[jetboy]

The managed speed looks after the takeoff (V2+10 knots) during SRS until acceleration altitude (CLB). If left in managed, the aircraft would then accelerate (through pitch down) to the SPD LIM (250<10,000 ft). Pre-selecting green dot speed allows the autopilot to automatically open the window for you at acceleration altitude and climb out at green dot, which is your best lift/drag ratio speed, and your minimum maneuver speed. This also gives you the best climb gradient, which should be used until minimum safe altitude (MSA). After MSA, pushing for managed allows for acceleration to 250 knots, until 10,000 feet and then it automatically bugs for ECON SPD. The pre-selection on the PERF page only saves you the trouble of manually setting green dot for best climb angle. Does that help you?

[320DRIVER]

Usually we leave the managed profile. We select the GD speed manually when we have have a turn greater than 90 degrees in the SID as we would be flying fast in the wrong direction!

There may be other situations were selecting GD manually may be beneficial but for standard ops, I think the standard acceleration profile is just fine.

Is there any reason why you guys select GD manually as the norm? Thanks for any feedback.

[mcdhu]

m&v, checkout Fcom 3.03.06 P9 'Climb, Cruise, Descent Speed Preselection'. It says there that you..'may preselect GD speed on the PERF CLB page.. for close in turn or close in alt constraint'. Equally, of course, you could always hit EXPEDITE once the flaps are running in to achieve the same result. Are you saying that it is in your SOPs to enter GD in the Perf Clb page until above safe alt?
Cheers,
mcdhu

[m&v]

Thanks for the info guys(it's been so long since I last looked it up),a recent quiery to me caused the question.
Jetb,wouldn't the FMS g/d climb the a/craft at g/d.until one selected 'managed speed'thence it would accelerate to 250/10000?????
I appreciate your reference,Mcdhu,to the FCOM...Our Airbus SOP's stipulate that one 'may preselect the g'/d(perf page)for the 'close in' turn/alt constraint'(3.03.06P7)..
For the last ten years or so we've always Hardtuned it....

Thanks again.....:)

[m&v]

Sorry Mcdhu,I didn't notice that we'd used the same reference until after posting.....Thanks again:(

[manuel ortiz]

m&v

In addition ...

Does your SOP call for managed speed at 3000 feet ?

If so it could be tied to a noise abatement procedure ( ICAO B / NADP 2 )

Rgds

Manuel

[m&v]

Your on the right track Manuel,I've since found out that the only reason we retained the G/D speed was for noise abatement,generally climb to 3000'agl prior to acceleration....
The 'other' way to do it was to reset the ACC alt to comply with 'VNAV a'
But selecting G/D(hard tune)seemed the simplest way!!!!
I'm not sure which profile is ICAO or not??
The FAA are stipulating a 'climb thrust'at 800'agl,then continue the climb about V2+to 3000'agl....Is ICAO the same...
we select climb at 1500'agl anyway(FCOM):D

[mcdude]

We handle noise abate through the THRUST RED/ACC entry and apply the FCOM in preselecting a climb speed (for close-in turn or altitude contraint)

In fact when preselecting is required we often select green dot +10 (not SOP) particuarly when heavy and A321, as the FAC calculated GDS increases by about 1 knot per 700feet (guess) and doesn't look pretty to have that pink triangle below the little green circle. Rgds

[Jamie320200]

Down in Australia we have noise abatement types A and B, A was thrust reduction at 1500 and accel at 3000 which works well simply by setting up the altitudes at the bottom left and right of the perf page. B required a reduc+accel at 1000' but stopping at green dot, some guys were starting to hard tune GD for that one just so you didn't have to push expd airbourne.
All the stuff in your posts was pretty applicable too.

(Unfortunately Ansett doesn't exist any more so it's academic for me)

[airbuslad]

I realize its probably a difference of only a knot or two but is in not better to let the FAC calculate the Green Dot speed once it the aircraft is airborne. I believe that the FAC will calculate the real Green Dot speed by figuring out the actual weight of the aircraft (by calculating aircraft climb performance) at the time not by the weight entered out on the ground via the init page b (ZFW entry & Block Fuel) since we all know that standard numbers are usually lighter than actual.

Taken from FCOM:

The principle of the speed computation is as follows : First, the FAC computes VS1G (stall speed). From VS1G it computes the gross weight which is also sent to the Elevator Aileron computers :

When the aircraft is below 14500 feet and 250 knots, it computes this from current angle of attack, speed/Mach, altitude, thrust, and CG.

When the aircraft is above 14500 feet or 250 knots, it computes this out of the GW, which it has memorized and updated with a fuel consumption model set in the FAC.


Let me know if I am misinterpreting this.
Cheers

[airbuslad]

Hiya Silky,
If I understand you correctly, if you leave the "Climb Spd" blank in the CLB Perf on the ground, the FAC will compute green dot via the numbers entered in the init page. Once you are airborne, until slat retraction the FAC will use init page numbers and when the slats are retracted then the FAC will compute greed dot via the actual performance of the aircraft?

Cheers
P.S. Where in the FCOM can I find the commentary about the slat retraction.

[manuel ortiz]

m&v

They go something like this :

ICAO A , oriented to alleviate noise for areas close to the airport and basicaly calls to keep flaps and ~ V2+10 to+20
to ~ 3000 feet.

ICAO B is used for distant noise sensitive areas and calls to clean up to climb at Vzf to ~ 3000 feet and then accelerate.
Easiest way to comply with this I feel is by preselecting G dot , agree with you.

For both procedures power should not be reduced before 800' .

Brgds. manuel