How to know if you can make required climb gradient?
 

Firstly, just to confirm, on almost all the charts, I see the climb gradient required, and then also ROC in feet per minute. Basically all the calculations are done.
Are there any formulas anyone uses or is needed?
IF in the case Roc wasn't given, just multiply GS by required climb gradient which should give you the required ROC, if I'm not wrong..

Secondly, chart says for example if with a GS of 150 knots, You will need 800 FPM, do you use common sense to know if you can make that?
How do you even know what your GS wil be before you've taken off?

Some silly questions, I apologize.
Appreciate the input :D

How to know if you can make required climb gradient?
 

Formula is correct but I don't think you need to be so accurate. Just round your numbers on the safe side and average out your GS figures and if your result is too close to the minimum ROC required then calculate more precisely or re-think the departure. That's what I do anyway...

In the majority of cases you will be taking off into wind, so use of your indicated speed for the climb, this will give a you a close approximation of GS with a small buffer.

GS is not the worst "unknown". The hard one is the rate of climb. How do you know what rate of climb you will be able to maintain? Other then wild guessing.

Thanks for the replies guys.

Romasic,
Honestly not sure.. Do tell please :O

I have no idea except the above mentioned wild guess...
So, the whole thing is a double wild guess. You can plan departure performance based on personal experience, improve gradient by keeping flaps, thrust and not accelerating until clear of restrictions and inform ATC if you actually see, that the aircraft is not able to keep the required gradient. That's what I do, and would be glad to see if someone has a more scientific way to do it.

On a Jet you would usually refer to your QRH/AFM/Performance manual where you will find tables with gradient limiting weights for given outside conditions.

if u wanna guess the g.s its about to be a bit less or more depending upon your ias ( initial climb out phase), just to be one the safe side u can add 10kts to your ias to calculate min roc.

r.o.c= angle required * g.s * 100
divide by 60

root:

Well, sounds logical, but I'm not aware about such tables in my aircraft FCOM (A330). Only general climb tables suitable for calculating climb at far bigger altitude and distance scale. Nothing about gradient just after departure:confused:

This will not answer your question but i can tell you how I'm sure of making a climb gradient.

In my company, (i'm sure a similar procedure is used in most airlines) we use RTOW tables to compute the flex / assumed temperature. These tables will guide you to take the minimum power setting to meet all regulatory requirements as well as performance factors, such as Field limit, obstacle limit, climb limit and a few others.

Knowing that the assumed temperature, (or full power as the case may be) was computed correctly, I know that we can meet the climb gradient for that particular departure under the ambient conditions.

Airline man:

These tables end at acceleration altitude, but in many, if not the most cases, the requirement to maintain the gradient goes much higher (just check CDG for example: up to FL150 or until the SID limit). By the way, here we come to another issue: what to do with this gradient during acceleration and flap retraction?

Aeroncaman:

We are discussing how to determine before departure what vertical speed we will be able to maintain in given conditions.

A check of the FMC altitude predictions at each waypoint should be adequate to the task.

In the USA, the maximum climb gradient for ODP's/SID's is only 500'/nm -- typically not a problem for jets.

aeroncaman
Oh?

Please provide the pertinent cite.

Why would anyone want to fly a SID with OEI all the way to say, FL150 at CDG?

Aeroncaman:

I also now these words:) But the thing is that they are empty in our case. I bet you won't be able to point the exact location of this information in any Airbus FCOM. Even with the help of any Airbus pilot, if you are not one of us. At least up to date nobody I asked was able to.:ugh:

and to disregard the limits is no good idea...
 

pilots tend to take sop more important than jeppesen limits and this happened in a company with thrust reduction and acceleration 800ft:
departure with an early right turn due hills ahead and minimum gradient 6% up to 1700ft:
using aircraft with enhanced gpws (looking ahead with terrain database) hard warnings "pull up" before starting turn as this system does not look around a planned corner...
myself I use normally flight path vector dialing in corresponding angle instead of doing an "open acceleration" and our airbus fms preflight gives good reference altitude when changing acceleration altitude to upper end of restriction...

Aeroncaman:

"Must" doesn't help. It's not there. No matter how strange it sounds.
And, BTW it wasn't there on 757/767/747 I have previously flown...

Seriously? We have airline pilots in here that get a SID with a gradient requirement and have no clue on whether their aircraft can meet it or not?