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Landing Climb Limit Weight

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Landing Climb Limit Weight

Old 29th Apr 2014, 10:12
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Landing Climb Limit Weight

Hi

Regarding B777 Landing Climb Limit Weight

A) Performance Dispatch => Gear Down => With Temp 30 C & Airport Pressure Altitude 0 => Landing climb limit weight is 335.7

B) Performance In flight => Advisory Information => With Temp 30 C & Airport Pressure Altitude 0 => Landing climb limit weight is 376.6

Both (A) and (B) are valid for approach with flaps 20 and landing with flaps 30.

According to the regulation the Landing climb gradient charts are calculated for go-around with the aircraft in the landing configuration where all engines are operating and the landing gear is extended.

Why is there a weight difference between (A) and (B). Is it something to do with the gear doors or it is something else?

Thanks
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Old 1st May 2014, 22:37
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I don't fly the 777 or know which country you're in, but Dispatch performance and Inflight performance usually have different factors applied. One being on the ground for planning and one being in flight (usually the actual diastase with no or a just a small factor applied).

Probably a good place to start! Hope it helps..
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Old 2nd May 2014, 00:43
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Dispatch performance and Inflight performance usually have different factors
thats what i want to know in this case

usually the actual diastase
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Old 2nd May 2014, 08:49
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Maybe this helps -

From Boeing Jet Transport Performance Methods:
approach regulatory requirements
There are two separate regulatory requirements that are included in the climb-limited landing
weight. The first of these two is referred to as the approach climb requirement, the second is
called the landing climb requirement.
The airplane’s landing weight must be low enough to meet the legal requirements specified for
whichever is the more restrictive case of the two.
. For twin-engined airplanes the approach climb requirement is usually more limiting than the landing climb requirement. There is no 'factor' on the climb-limited landing weight, and I can't think of anything that would create a difference between the 'dispatch' and 'in-flight' limits
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Old 2nd May 2014, 09:28
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Hazelnut,


With respect you are answering a question Haroon didn't ask. Approach climb has nothing to do with this.


To answer the question why the different figures for A) and B) with regards landing climb weight limit.

Well normally all figures from dispatch data will differ from inflight data because relevant dispatch data
includes the regulatory extra factors to the data that are required to legally dispatch whereas B) is simply what the aircraft will physically do when inflight hence the name. Remember once you have moved under your own power the dispatch figures are meaningless and the unfactored "inflight" data is all you need to legally land.


Having said all of that you might want to check your data again because with regards Landing climb weight limits for 30c with PA 0 there is no difference on my manuals. Both dispatch and inflight show 376.6 and that's also for both FAA and JAA.

Last edited by 8che; 2nd May 2014 at 09:53.
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Old 2nd May 2014, 09:44
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8che,

I'm fully aware that I didn't answer the OP's question, thank you. I thought by providing related information he might discover that he didn't ask the right question.

Since you are so well informed, can I ask you to explain the requirement that determines the 'in-flight' climb-limited landing weight?
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Old 2nd May 2014, 09:53
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regulatory extra factors to the data that are required to legally dispatch
thanks 8che, do you know of any write up or document with details on this one. the weight difference is so much that I am interested to know more about the factors involved here.

you might want to check your data again -- there is no difference on my manuals.
"Landing Climb Limit Weight" given in the Landing section of "Performance Dispatch and Performance In flight" is same but I am referring to Performance Dispatch > Gear Down Section and not Performance Dispatch > Landing section.

Last edited by Haroon; 2nd May 2014 at 10:14.
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Old 2nd May 2014, 10:10
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Hi Haroon,


Not to hand. Its 376.6 for both according to my charts. That's 777/300ER FAA and JAA. B777-200LR is 378.7 for both again FAA and JAA.


Hazelnut - sure- 3.2% climb gradient from a min of 50ft agl while fully configured to land. (all engines)

Last edited by 8che; 2nd May 2014 at 10:21.
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Old 2nd May 2014, 10:25
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Hi 8che,

FCOM Vol 1

Performace Dispatch

777-300 ER

Takeoff
Enroute
Landing (Landing Climb Limit Weight - 376.6)
Gear Down (Landing Climb Limit Weight - 335.7)
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Old 2nd May 2014, 10:56
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Got it now Haroon.


You are looking at Gear down section as well.


Remember you have dispatch data and inflight (or enroute). Well on top of that you have a non-normal gear down performance section included in both of these. This is to of course help dispatch and fly with the gear locked down for technical reasons etc.


The gear down section only shows the lower 335. Makes sense as it assumes you will never be able to retract on a baulked landing.


So to recap my data shows normal dispatch and inflight agree with 30c and O PA at 376.6 but are different for the GEAR DOWN section which is also contained in both dispatch and inflight performance chapters showing 335.7.
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Old 2nd May 2014, 11:09
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but the landing climb limit weight is also calculated with gear down

so whether a gear can be retracted or not should not affect the values unless there is a difference between the methods of calculation in case a gear cannot be retracted at all. that's what i want to know
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Old 2nd May 2014, 11:18
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Originally Posted by 8che
Hazelnut - sure- 3.2% climb gradient from a min of 50ft agl while fully configured to land. (all engines)
That is the landing climb gradient requirement for dispatch. I was asking you to explain the equivalent requirement for 'in-flight' which you claimed to be different.

P.S.
The gear down section only shows the lower 335. Makes sense as it assumes you will never be able to retract on a baulked landing
Since the 'landing climb' gradient requirement is always with gear down, would that be the weight limited by the one-engine-inoperative 'approach climb' requirement with the gear down?

Last edited by HazelNuts39; 2nd May 2014 at 11:38. Reason: P.S.
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Old 2nd May 2014, 11:39
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ok guys the argument now is not between in flight and dispatch data.

just want to know the following:

FCOM Vol 1

Performace Dispatch

777-300 ER

Takeoff
Enroute
Landing (Landing Climb Limit Weight - 376.6)
Gear Down (Landing Climb Limit Weight - 335.7)

Gear down performance means gear cannot be retracted.

But landing climb limit weight is also calculated with gear down.

So what factor creates a difference in the limits.

Thanks both of you
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Old 2nd May 2014, 12:07
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Originally Posted by Haroon
So what factor creates a difference in the limits.
Doesn't my post #4 above answer that question?
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Old 2nd May 2014, 13:00
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Common guys, a landing climb assumes you retract the gear while going around..
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Old 2nd May 2014, 17:21
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Doesn't my post #4 above answer that question?
Sorry Hazel I am unable to understand from that. Approach climb is not an issue here. Both conditions are in Performance Dispatch and related to Landing Climb.

landing climb assumes you retract the gear while going around
Hi Latetonite, landing climb is with gears down unlike approach climb. In comparison with Gears Down performance in which gears will not be retracted at all, gears can be retracted after a landing climb but is this fact considered while establishing its performance? I don't have any document that mentions this, if you have anything on this please share.

I can confidently say that I still don't have a clue
me too OK465
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Old 2nd May 2014, 17:27
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Haroon, use your common sense. A landing climb performance requirement is basically normal go- around performance, to meet obstacle clearance.
You ever heard about performance requirements with the gear remaining down, if it is retractable? Anywhere?
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Old 2nd May 2014, 18:09
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My apologies, the landing climb gradient is measured with the gear still down, flaps in landing config, and vref.

The missed approach climb requirements is another issue.

Getting tired I guess.
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Old 2nd May 2014, 18:25
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initial and temporary condition
Thanks KBP, that gives me a clue

According to Jet Transport Performance Methods:

By default, the Boeing software assumes that descent ends 1500 feet above the landing airport, and approach begins at 1500 feet and continues to the runway threshold. This definition isnít contained in any sort of regulatory material, itís a purely arbitrary definition that the software uses in the absence of some other definition that may be provided by the user of the software.

Since generally gears are down before 1500 feet, I was under the impression that the approach climb performance was calculated with gears down as an initial condition and then retracted. But it seems perhaps approach climb performance is calculated with initial conditions of gears as retracted. This would answer the landing climb issue in which initial condition is gear down and "gear down performance" in which they will permanently remain down.

Is that what you mean KBP?
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Old 2nd May 2014, 19:42
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Originally Posted by Haroon
Sorry Hazel I am unable to understand from that. Approach climb is not an issue here. Both conditions are in Performance Dispatch and related to Landing Climb.
I'm suggesting that the term "Landing Climb Limit Weight" is a misnomer. The correct term would be "Maximum Landing Weight Limited by Climb Requirements", or in short "climb-limited landing weight".

As explained in post#4 the climb-limited landing weight must meet two separate climb requirements (*):

(a) The all-engines-operating landing climb requirement is not affected by the inability to retract the gear.

(b) The one-engine-inoperative approach climb requirement, with the flaps 'one notch up' from the landing configuration, is normally met with gear up, but that changes to gear down if the gear cannot be retracted. Since that requirement is more restrictive than the landing climb requirement, the climb-limited landing weight is lower than in the normal configuration.

Apparently '8che' has withdrawn his assertion that the approach climb requirement is never limiting on the triple-7.

(*) Each of the two requirements has its own specification of configuration, airspeed and thrust. It is not correct to assume a change of configuration between the two conditions.
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