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B777 eng inop NNC: flaps 30 or 20 with G/A gradient?

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B777 eng inop NNC: flaps 30 or 20 with G/A gradient?

Old 13th May 2019, 14:56
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Grrr B777 eng inop NNC: flaps 30 or 20 with G/A gradient?

Hi everyone,

In the B777 Eng Fail (or shutdown) NNC, at some point the C/L asks to choose between Flaps 20 or Flaps 30 (if perf. permits) for landing.

The obvious answer is: Choose Flaps 30, and if needed for example for G/A climb gradient, use Flaps 20 (with G/A flaps 5).

So I just had a simulator with a diversion to BGSF, where the approach, on RWY 09 requests a climb gradient (not an ATC climb gradient) of 5%.

My question is: How do I check if I can land using flaps 20?

-If I do a landing distance calculation with no failure in the OPT (or using the Performance dispatch of the FCOM), I can check that, landing flaps 30 with a Flaps 20 G/A, the plane will be able to follow a specified climb gradient when going around with one engine failed. Of course, if this is OK flaps 30, it will be ok flaps 20.

-But what should I do if the OPT tells me that the plane won't sustain a 5% climb gradient with flaps 30/GA flaps 20? How do I check if the performance will permit to get a 5% climb gradient (or any other CLB gradient) with the option to use Flaps 20 / GA Flaps 5?

Because a G/A with flaps 5 has a better climb gradient than one with flaps 20 doesn't mean that it will be a sufficient climb gradient.

Thanks in advance for your help!
Romfour is offline  
Old 14th May 2019, 02:22
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To check your MLW climb gradient on one engine, have a look in FCOM OPS section under "Approach with Engine Failed". Its gives an OAT and pressure altitude maximum to achieve gradients from 2.5% through 7% (Only at max landing though).
I imagine your OPT (if you have one) will throw out the calculation if unable at the given weight (this may be company selectable option??). Options would be to raise the minima (HKG has a 2.5% grad. minima listed for example), or to fly the engine out departure profile (if there is one), or land elsewhere.

Hope this helps.
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Old 14th May 2019, 06:10
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The answer lies somewhere in your FCOM and/or QRH where hopefully you should find a table cunningly labelled “ Go-Around Climb Gradient......”

Originally Posted by Romfour View Post
Hi everyone,

In the B777 Eng Fail (or shutdown) NNC, at some point the C/L asks to choose between Flaps 20 or Flaps 30 (if perf. permits) for landing.

The obvious answer is: Choose Flaps 30, and if needed for example for G/A climb gradient, use Flaps 20 (with G/A flaps 5).
Broadening the question slightly the fact you use the word "obvious" is interesting, because I guess whether it is obvious to use F30 or not might boil down to local/training department policy

FWIW we approach this question the other way around, so to speak: because of possible issues with performance on a SE Go-Around our "obvious answer" when running that checklist is very much one of "choose Flap 20”, unless there are compelling reasons such as stopping distance to use anything more.

If we have to use Flap 30 (e.g. contaminated runway, etc) and that compromises climb gradient then the solutions would be the sort of things RubberDogPoo has come up with.


Last edited by wiggy; 14th May 2019 at 07:08.
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Old 14th May 2019, 07:23
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Originally Posted by RubberDogPoop View Post
To check your MLW climb gradient on one engine, have a look in FCOM OPS section under "Approach with Engine Failed". Its gives an OAT and pressure altitude maximum to achieve gradients from 2.5% through 7% (Only at max landing though).
I imagine your OPT (if you have one) will throw out the calculation if unable at the given weight (this may be company selectable option??). Options would be to raise the minima (HKG has a 2.5% grad. minima listed for example), or to fly the engine out departure profile (if there is one), or land elsewhere.

Hope this helps.
Thanks for your answer.
The only table I can find in my FCOM, which also was referred to me by the technical section of my company, is the "go around climb gradient", which has only the "go around flaps 20" part and nothing else.
The OPT cannot do that unfortunately. It has the option to input a G/A clb gradient, but only for a "normal operation" with flaps 30 or 25, not 20.

Originally Posted by wiggy View Post
The answer lies somewhere in your FCOM and/or QRH where hopefully you should find a table cunningly labelled Go-Around Climb Gradient......



Broadening the question slightly the fact you use the word "obvious" is interesting, because I guess whether it is obvious to use F30 or not might boil down to local/training department policy

FWIW we approach this question the other way around, so to speak: because of possible issues with performance on a SE Go-Around our "obvious answer" when running that checklist is very much one of "choose Flap 20, unless there are compelling reasons such as stopping distance to use anything more.

If we have to use Flap 30 (e.g. contaminated runway, etc) and that compromises climb gradient then the solutions would be the sort of things RubberDogPoo has come up with.
Thanks for your input
As above, this table exists but helps only to say if it will be ok flaps 30.

And for the second part, you are indeed totally right. I probably saw the "if perf permits" as a way to say "this is preferential if possible", but there is no reason for that

To explain a bit more:
On that simulator training, we couldn't get the answer to that.
So I wrote to the technical office (a service in my airline you can write to if you have technical questions), and their answer basically confirms that it's not posible to know the G/A gradient with flaps 20 and you just have to use your "airmanship" to decide...
So I'm wondering if something is missing in our documentation, but it seems not as they asked Boeing and were told that there is no way to know it...
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Old 14th May 2019, 09:12
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Originally Posted by Romfour View Post
Thanks for your answer.
The only table I can find in my FCOM, which also was referred to me by the technical section of my company, is the "go around climb gradient", which has only the "go around flaps 20" part and nothing else.
The OPT cannot do that unfortunately. It has the option to input a G/A clb gradient, but only for a "normal operation" with flaps 30 or 25, not 20.


FWIW our reference is OPS.29 (not that I expect it to match yours) and gives max temps and PA for both a F20 and F5 go around. Id be surprised if a customer would elect to not have that info available.

Im with wiggy, starting point would be F20 unless runway length/stopping performance was in question.
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Old 14th May 2019, 09:24
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Originally Posted by RubberDogPoop View Post

FWIW our reference is OPS.29 (not that I expect it to match yours) and gives max temps and PA for both a F20 and F5 go around. Id be surprised if a customer would elect to not have that info available.

Im with wiggy, starting point would be F20 unless runway length/stopping performance was in question.
Thanks.
What is OPS.29? Can it be found anywhere online?

For information, here is the answer my airline got from Boeing when asking about a question similar, which actually doesn't answer at all about the flaps 20 / GA Flaps 5 question.
As XXX (airline) has stated, the Go-Around climb gradient is not used in the Non-Normal Configuration landing distances calculation since there is no information available to evaluate the go-around climb gradient for each failed system configuration. That is, there is lack of source data. The go-around gradient capability could actually be determined by doing another OPT landing calculation without selecting the NNC because the 'ENGINE SHUTDOWN' NNC with landing flaps 30, for example, is essentially the same as the approach climb gradient with landing flaps 30. Additionally, the 'Engine Inop Go-Around Climb Gradient' table presented in the Performance Dispatch (PD) chapter of the FCOM-QRH can also be referenced. Please be advised these data only represent the particular point in the go-around maneuver at which the assumptions provided exist. For example, for the attached 777-300ER/GE90-115BL table, the conditions are Flaps 20, Gear up, packs on, wing anti-ice off. Corrections are presented for packs and anti-ice variations, but otherwise these data do not represent any other condition or configuration.
​​​​​​​Thanks
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Old 14th May 2019, 12:41
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If in any doubt fly the special engine failure procedure prescribed for take off.
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Old 14th May 2019, 13:57
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Originally Posted by Cough View Post
Our 787 OPT allows us to select a 5/20 option as a landing flap (20for landing, 5 for G/A- for a normal approach as the OP notes) so we can indeed compare the F5 G/A gradient to the F20 one. I've sometimes found the F5 one to be more limiting...
Seems the option is not there on 777 ;-)
Can you elaborate on situations where it would ne "more limiting" to use F20/F5? Do you mean in any of a G/A phase or for landing?

Originally Posted by gatbusdriver View Post
If in any doubt fly the special engine failure procedure prescribed for take off.
That's indeed the solution recommended by a friend.
The other solution would be to dump fuel until at a weight where the G/A clb gradient can be ensuredusing flaps 30 but well, it's not really an answer
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