A320 After Takeoff Climb Gradients

[Bula]

I'm doing a little bit of book work and have come up empty.

Looking at the net climb gradient charts of FCOM 2 I was wondering if someone will be able to help.

One procedure I fly has a net climb gradient of 6.6%. My performance data allows for the 2.4% and obstacle clearance and I know from personal experience the A320 can make the 1000 - 1200 fpm (of there abouts) to meet the 6.6%, easily.

My question is, using the Quick Reference and Net Takeoff climb charts is that a 6.6% seems to become highly restrictive, up to a 31t weight reduction for 8%. Can anyone give me some advice as to where else I might be able to find the relevant information to tell me the aircraft climb gradients at specific weights and density heights.

[potkettleblack]

Not sure if the following is any help to you as it more relates to how we deal with climb gradients in relation to a missed approach. In our paper performance manual on each aircraft there are pages for Landing Mass Climb Limits. As most of our approaches are made Config full we use this page most of the time. I think there is a page for Config 3 as well. It helps us to work out if we are able to fly whatever the missed approach gradient is should we need it.

The table is set up for the standard 2.5% climb gradient and assumes a/c is off, anti ice off, and 1.23vs. You enter the table at a given pressure altitude and temperature to get a gross weight. Then apply corrections (deductions) for a/c, anti ice, engine and wing anti ice, and for each 0.5% above the standard 2.5% climb gradient. After applying all the corrections you are left with a corrected aircraft weight and you compare it to your planned weight. Hopefully you are under it and hey presto.

[ppppilot]

For the 330/340 we have the chapter 4 at the OM regarding to performances. 4.01.20 is for TO performance
There are some charts at "4.01.40 Certification performances", named obstacle limited weight and there you have quick reference charts with the TO climb gradient up to 20000 ft distant from the end of the rwy for close and remote obstacles up to 5600' height.
I don't know if you are talking about that charts.
Hope this helps

[MD11forever]

Hi
I'm facing the same problem as Bula.
How would you guys check if you are able to comply with a 10% required climb gradient on a SID?
FCOM/QRH/LPC, nothing seems to answer my question.

How to use the tables in FCOM 2.2.50?
Let's say "Remote Obstacle Clearance Conf 1+F":
5400ft obstacle at 30000m -> Gradient 6.4% = weight decrement of 24t.
So I take now the weight from the LPC which I'm able to fly out of the RWY with TOGA and subtract 24t and I'll meet the 6.4%?
This is more than wrong I suppose, but how to answer my initial question?
Thanks in advance for everybody helping.

[OPEN DES]

A climb-gradient on an SID is an AEO (all engines operative) scenario. You check compliance by looking at the FMGS predictions/pre-select climb speed as req.. This is where inserting the history (climb)winds comes in handy.

[john_tullamarine]

A climb-gradient on an SID is an AEO

indeed ... now, what do you intend to do when the noise stops on one side ?

If you wish to fly a SID without consideration of alternative escape paths for the OEI case then you probably ought to make sure that you can fly the SID OEI. In the case of the high gradients cited above, that will involve a significant payload loss.

[9.G]

Bula, I've stumbled across the same problem and it seems the answer to that question doesn't have solid grounds as the TAKEOFF performance is calculated based on the OEI scenario to avoid the weight penalties. Deductive experience and sound airmanship might be of a help. Predictions in the FMGC aren't reliable and are for information only let alone some modification even provide erroneous data, see relevant OEB. One way of doing so, would be a rule of thumb as follows: for a ground speed of 150 KT a climb rate of 1500 ft/min would make round 10% of climb gradient. Out of experience A320 can make up to 15% in normal configuration tops. In case of a engine failure follow OESID.
Enjoy the search :ok: