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 |
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.. |
Dispatch performance and Inflight performance usually have different factors usually the actual diastase |
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. |
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. |
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? |
regulatory extra factors to the data that are required to legally dispatch you might want to check your data again -- there is no difference on my manuals. |
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) |
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) |
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. |
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 |
Originally Posted by 8che
Hazelnut - sure- 3.2% climb gradient from a min of 50ft agl while fully configured to land. (all engines)
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 |
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 |
Originally Posted by Haroon
So what factor creates a difference in the limits.
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Common guys, a landing climb assumes you retract the gear while going around..
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Doesn't my post #4 above answer that question? landing climb assumes you retract the gear while going around I can confidently say that I still don't have a clue |
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? |
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. |
initial and temporary condition 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 isn’t contained in any sort of regulatory material, it’s 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? |
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.
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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