Enroute Climb Limit Weight

[JABBARA]

Surely the point of the CDL penalty is that you start with normal planning and then simply apply the weight and fuel penalty. That does not need a computer, even though it will be done on one. The penalty is crude and conservative, therefore the penalised aircraft will in reality perform better but less efficiently than one dispatched at normal weight/configuration.

Fuel Penalty application is crystal clear but weight is not. I am not mentioning FMS calcualtion, I am talking about planning calculation. How to use weight penalty for planning purpose? Adding CDL penalty weight to actual weight is not a solution, That only helps to figure out what will be the capability of gross ceiling with this CDL penalty, which new gross ceiling is always less than the actual weight. But this has "NO RELATION" with NET CEILING. This calculation never gives an idea about driftdown NET CEILING path and NET CEILING VALUE, therefore we may not be aware whether this new NEt CEILING path and vaue is conflicting with enroute terrain/obstacles or not.

[oggers]

Originally Posted by JABBARA

Fuel Penalty application is crystal clear but weight is not. I am not mentioning FMS calcualtion, I am talking about planning calculation. How to use weight penalty for planning purpose? Adding CDL penalty weight to actual weight is not a solution, That only helps to figure out what will be the capability of gross ceiling with this CDL penalty, which new gross ceiling is always less than the actual weight. But this has "NO RELATION" with NET CEILING. This calculation never gives an idea about driftdown NET CEILING path and NET CEILING VALUE, therefore we may not be aware whether this new NEt CEILING path and vaue is conflicting with enroute terrain/obstacles or not.

The net flight path data must be in your AFM (or approved supplement of) because it is the law:

b) Each Airplane Flight Manual must contain the performance information computed under the applicable provisions of this part.......25.123. En route flight paths. The one-engine-inoperative net flight path data must represent the actual climb performance diminished by a gradient of climb of 1.1 percent for two-engine airplanes [etc]

Fuel Penalty application is crystal clear but weight is not. I am not mentioning FMS calcualtion, I am talking about planning calculation. How to use weight penalty for planning purpose? Adding CDL penalty weight to actual weight is not a solution,

Nobody is saying to add weight. You determine the enroute limit weight using the AFM performance data (for net flight path, it must be there). But you won't be able to achieve that performance given the extra drag of the missing item, so you reduce actual weight by the amount stated in the CDL and your net flight path will still be okay. I don't understand why that is not clear for you.

[JABBARA]

I don't understand why that is not clear for you.

But I understand why you do not understand, because it is complex

Let me answer again to clarify"

The net flight path data must be in your AFM (or approved supplement of) because it is the law:

Yes but it is not in the form of pilot usable or pilot friendly and AFM is not an operational manual which normally distrubuted to pilots.

That is the extarct from A 330 AFM:
For en route net flight path (single engine cruise) performance determination, the Performance Engineer's Programs/AFM_OCTO approved FM module at the latest approved revision must be
used. Refer to PERF-OCTO Performance Database.

What I remeber at 90's, the B 737 AFM (which is not distrubuted to pilots but I grabbed one set somehow), used to consist of big, thick 2 or 3 binders (thousands pages) including NET FLIGHT PATH charts as well. But not anymore at least in AIRBUS AFM.

You determine the enroute limit weight using the AFM performance data (for net flight path, it must be there). But you won't be able to achieve that performance given the extra drag of the missing item, so you reduce actual weight by the amount stated in the CDL and your net flight path will still be okay.

Since as a pilot we cannot reach NET FLIGHT info or enroute limited weight values because it is not available for us (as I mentioned above paragraphs), the above quotation becomes void. I mean "reduce actual weight by the amount stated in the CDL" becomes void. There is no meaning of reducing the actual weight by amount of penalty Suppose our initial Actual TO weight before CDL was 200 t, so what should we do with CDL? Off loading payload by penalty? No way!
The penalty amount should be reduced from Enroute Limiting Weight, but There is no info about that in our hand.

As example A 330 CDL 57-04 FLAP TRACK FAIRING missing penalties

- Fuel consumption is increased by 3.42 %.
- Enroute performance Limiting Weight is reduced by 5 240 kg (11 553 lb)

First one is crystal clear : Example new trip fuel = TRIP FUEL x 1.0342

Second one is not clear: 5240 Kg? To subtract from which value? We do not know that. To find this value, we need the software mentioned in AFM and Route Obstacle Information.



I hope now you understand.

[oggers]

JABBARRA

Since as a pilot we cannot reach NET FLIGHT info or enroute limited weight values because it is not available for us (as I mentioned above paragraphs), the above quotation becomes void. I mean "reduce actual weight by the amount stated in the CDL" becomes void. There is no meaning of reducing the actual weight by amount of penalty Suppose our initial Actual TO weight before CDL was 200 t, so what should we do with CDL? Off loading payload by penalty? No way!
The penalty amount should be reduced from Enroute Limiting Weight, but There is no info about that in our hand.

As example A 330 CDL 57-04 FLAP TRACK FAIRING missing penalties

- Fuel consumption is increased by 3.42 %.
- Enroute performance Limiting Weight is reduced by 5 240 kg (11 553 lb)

First one is crystal clear : Example new trip fuel = TRIP FUEL x 1.0342

Second one is not clear: 5240 Kg? To subtract from which value? We do not know that. To find this value, we need the software mentioned in AFM and Route Obstacle Information.

I hope now you understand.

Yes I understand that you cannot do it because the pilots at your company do not have the information to hand. Nonetheless it remains a fact that knowing how to check your enroute climb limit weight is required knowledge for professionals. Your dependence on a third party to do those calculations is no answer to the question posed by this thread.

[FullWings]

If you are given an aeroplane and told to fly from A to B and have nothing but the FCOM, DDG, QRH, etc. then I could see it being an issue. Who does that? Every outfit I’ve heard of that flies large transport aircraft has some sort of flight planning system that takes account of en-route performance (in my case LIDO). If there is a problem with MEL items that compromises MSA, drift down, etc. then it will be flagged up or it simply won’t produce a plan.

From a safety POV, your plan will be OK as long as the correct inputs have been made. Now you want the information presented to you in flight to be representative of operating with the particular defect: a simple way is to add the performance weight penalty to the ZFW in the FMC so things like OEI ceiling are displayed correctly (and probably reasonably conservatively). Job done.

[8che]

Am I hearing an echo ?

[FullWings]

IMO it’s very easy to over-think these kind of things. Yes, as a performance engineer you have to cover all the angles and use the most accurate calculations possible. If you’re operating the aeroplane, especially past the point of dispatch, it’s big-picture stuff...

[JABBARA]

Does anybody know how to apply penalties to Enroute Climb Limit Weight. (According to MEL/CDL). And what this weight mean itself? B737

My interpretation of this thread: As a worst case scenario, you are in the cockpit to fly back to home base but you found out just a new CDL is added to Tech Log Book effecting Enroute Performance Limiting weight with a penalty of 5000Kg; What I can do with this 5000kg?

If my interpretation is incorrect, yes dear Oggers, my answers may not be a solution.
But if my interpretation is correct, then I consider my answers are correct; besides they reveals a factuality: I repeat again, in that scenario 5000kg value is useless in the purpose at which it is given.

However, as advised at previous threads (including mine) and latest by FullWings, adding this value to actual ZFW or Actual weight to optimize FMS calculation is a better than nothing improvisation by pilot (not by any regulation or operation manuals including MEL, as far as I know) and I agree.
But emphasize again this is not the intended usage of 5000kg by CDL, but good enough to see what could be our real performance capability for Max Climb Altitude or related predictions.

Who does that? Every outfit I’ve heard of that flies large transport aircraft has some sort of flight planning system that takes account of en-route performance (in my case LIDO) .

That is I mean

[gearpins]

Here is My 2 cents worth. the steps are detailed below the chart:

[oggers]

My interpretation of this thread: As a worst case scenario, you are in the cockpit to fly back to home base but you found out just a new CDL is added to Tech Log Book effecting Enroute Performance Limiting weight with a penalty of 5000Kg; What I can do with this 5000kg?

JABBARRA, see the above worked example by gearpins of how easy it is to achieve this task. It is absurd to interpret the question of "how is this done?" as "how is this done if I don't have the net performance data which must by law be provided to the operator and used to accomplish this task".

[JABBARA]

Oggers, as you make comment you are revealing your ignorance in this issue.

The fake (but better than nothing) solution which was recommended by you was as below and be sure most of the people used to know before you.

If you give the FMC an 'assumed' ZFW equal to the actual weight plus penalty, then the ceiling and fuel burn data will become conservative (you will actually do better)

This quotation shows, unfortunately, you were not aware, neither the way you mentioned was the real solution nor, in fact, there is a real regulative solution.
However, I have to confess there is some progress: At least now you have learned CDL penalty application is not at the way as you recommended before. And I hope you understand it should be at the way I mentioned or by the way as in gear pins thread.

But still it looks you are away from understanding the real concept as considering it is very simple. No, it is not. Slowly read maybe you can get it.

First of all, that table is not particularly for CDL penalty correction. Theoretically you have to use that table for all flight regardless you have CDL penalty or not, to evaluate the obstacles through the route. I do not know how many pilots are doing this before every flight.

This practical solution advised by the table maybe only good for a short range flight; probably as in the operation area of the Airplane (likely to be Boeing) of the subjected Operator of which the given table belongs (e.g from table: For our operations this penalty is s never limiting)

To visualize what this table means, I write this sample (even without CDL): Consider a scenario; Departing from somewhere in Middle East and reaching TOC (single cruise level) after half an hour, then after another 5 hours crossing Himalayas, then arriving somewhere in Far East. If there is no escape route, Let´s say from a similar table (and with another additional table to calculate drift down fuel) we calculated weight to cross Himalayas should not be more than 190 t. This tables assumes you will be at 190t after only 30 minutes from departure or with another word, 5 hours before Himalayas. Therefore, TO weight should be adjusted as guaranteeing TOC weight should not be more than 190T. I guess in such a scenario, for example A 330, it can be implemented only at a Ferry Flight. Besides, if there is CDL penalty, you have to subtract this penalty (let´s say 5000Kg) from 190T, MTOW is 185t. If all these are digestible, yes calculation, either with CDL penalty or not, is very simple.

Let me detail for you: If you understand, for a route of which the highest obstacle is towards the end of route which maybe thousands NM away, according to this table, you have to limit your initial TOC weight, this table only recommends this. Therefore, simplified way may seriously affect your TOW limit so your payload. Consequently, this may be good only for the kind of operations for table´s owner; as they mentioned e.g For our operations this penalty is s never limiting.

To consolidate what I write above: For a true solution you have to find worst case of multiple weight vs obstacle height combinations as including the earlier obstacles effect. And this is not possible with a single table. Opposite the methodology of table (in fact), along the route, the highest obstacle (let´s say 16000) may be less critical or limiting if its location is towards the end of the route because of less demanding critical combination of weight vs obstacle height, because of reduced airplane weight along the route. As oppose the table recommendation, in this case no need to limit TOC weight.

Besides, an obstacle which lower but at the earlier phase of flight (were airplane is heavier) could be giving a more demanding weight vs obstacle height combination. If you want to be really legal and optimized you have to done this evaluation for all obstacles through the route. In this case that appreciated (and better than nothing ) table solution is not enough.

Additionally, This was from me:

The penalty amount should be reduced from Enroute Limiting Weight, but There is no info about that in our hand”

Above the light of all above, since -for example- Airbus is not distributing Net Flight Path data for pilots, then – although my English may not be so good as yours- but I guess, commenting my interoperation like
"how is this done?" as "how is this done if I don't have the net performance data which must by law be provided to the operator and used to accomplish this task"
itself is really absurd.