MEL DDG CDL confusing!?
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MEL DDG CDL confusing!?
dear all pilot ,
I searched this forum and there isn't any clear explaination of MEL DDG and CDL.
What I used most is MEL , and when can I use DDG and CDL as a pilot ? do I need to ?
also have the confuse of when you use MEL. just say examples .
After door close , you have one pack inop.
do you have to use MEL? I mean HAVE TO.
After engine start , you have one pack inop. do you have to use MEL?
and under the examples above , when you need to use CDL or DDG?
I know CDL is for configuration , so i think we can ignore it .
still confusing of this three ...........
I searched this forum and there isn't any clear explaination of MEL DDG and CDL.
What I used most is MEL , and when can I use DDG and CDL as a pilot ? do I need to ?
also have the confuse of when you use MEL. just say examples .
After door close , you have one pack inop.
do you have to use MEL? I mean HAVE TO.
After engine start , you have one pack inop. do you have to use MEL?
and under the examples above , when you need to use CDL or DDG?
I know CDL is for configuration , so i think we can ignore it .
still confusing of this three ...........
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My understanding... & using a B767. And of course re-emphasising the above post to read the introductory notes to your aircraft / Airline's DDG.
The DDG, is a "Dispatch Deviations Guide", and covers ALL issues with aircraft airworthiness, ie Minimum Equipments required, and deviations from normal configuration. In other words, the DDG is the overall document, and within that there are two 'sub' documents, specifically the MEL and CDL.
The MEL is used for EQUIPMENT failures (eg Pack inop, FMC, Rad Alt etc) and specifies the Minimum Equipments you can depart with.
The CDL is applicable to physical parts of the airframe - service panels, flap seals, static wicks etc - and will inform you how far you can 'deviate' from a complete airframe in order to depart. (forgive the over simplification.)
IF you cannot find any reference to your 'missing part' - eg Left Wing Detached - then that deviation is not allowed & dispatch not possible until rectification complete.
Ok - so when to use which, bearing in mind you ALWAYS refer to the 'DDG' (seeing as it is made up of both the MEL & CDL)
(1) On the walk-around you spot a pylon access panel missing. You open up the DDG, and go to the CDL within that & locate the info respective to said missing panel. Be sure to read all the introductory notes to the CDL, as >1 issue may be cumulative, ie have an ever-degrading effect on aircraft performance. (or eg a max of 3 related CDLs may only be allowed)
(2) An equipment (MEL) issue is not so straight forward, and divided into whether you're at:
- gate
- start (or moving under your own power)
- T/O thrust set
- less than 80 kts
- less than V1
- ie in line with the various EICAS Messages.
In essence:
(a) On the gate you note a STATUS MSG. These ARE relevant at this point in your 'flight', and WILL need reference to the MEL to ascertain whether you may depart or not.
After Engine start (or moving under your own power (dependant upon which definition your MEL uses) STATUS messages no longer require reference to the MEL and you may simply continue.
(b) Whilst taxing out you get an ADVISORY EICAS eg "L Pack Inop" - ie a higher level message than Status. Stop, and first carry out the appropriate (QRH) drill, and thence you MUST refer to the MEL. If it says "No Dispatch" - return to gate. If it allows dispatch but with Operational (O) considerations then you, as a pilot must apply those, eg limit your subsequent flight to FL350 and continue the taxi & take-off. (or return to gate for eg more fuel if that if the Flight level too limiting). If it allows dispatch but with Maintenance (M) considerations then you MUST return to stand for applicable engineering works to be performed (eg inhibiting valves.... whatever). No options here (M), as only a qualified engineer may do this work and subsequently sign off the aircraft as fit for flight.
(c) After T/O thrust is set you get ADVISORY (eg) PACK INOP. Do nothing, continue the take off, and only at a safe time, clear of terrain, high workload etc action the QRH. No need to consult the MEL as once T/O thrust was set you had 'dispatched' in terms of ADVISORY messages. Airmanship may suggest you 'educate' yourself by reference to the MEL when time is spare - but you certainly don't have to.
(d) Anytime below 80kts you get an EICAS CAUTION (eg FWD CARGO DOOR). Stop the aircraft (including reject the T/O) and then apply the appropriate QRH. With that out the way you then MUST open up the MEL to confirm whether the flight can continue or whether a return to stand is required. (it'll be obvious!)
(e) Anytime below V1, you get a WARNING EICAS. Stop the aircraft (inc reject if on the T/O roll), apply MEMORY / Reference items, and thence you MUST open up the MEL to determine whether dispatch is subsequently allowed. (it'll be obvious!)
Summarising...between..
Gate & Engine start / Taxy - all EICAS Status & above need MEL reference
Eng start / Taxy & Takeoff thrust set - all EICAS Advisory & above need MEL ref.
Takeoff thrust set & 80 kts - all EICAS Caution & above need MEL reference.
Above 80kts & <V1 - only EICAS Warning need MEL reference
>v1 the aircraft has dispatched in all events & nil reference to the MEL required.
So... a bit of a minefield? No, .... not if you apply your knowledge of EICAS message philosophy versus Boeings advices on continuing / rejecting flight. Hope this helps.
The DDG, is a "Dispatch Deviations Guide", and covers ALL issues with aircraft airworthiness, ie Minimum Equipments required, and deviations from normal configuration. In other words, the DDG is the overall document, and within that there are two 'sub' documents, specifically the MEL and CDL.
The MEL is used for EQUIPMENT failures (eg Pack inop, FMC, Rad Alt etc) and specifies the Minimum Equipments you can depart with.
The CDL is applicable to physical parts of the airframe - service panels, flap seals, static wicks etc - and will inform you how far you can 'deviate' from a complete airframe in order to depart. (forgive the over simplification.)
IF you cannot find any reference to your 'missing part' - eg Left Wing Detached - then that deviation is not allowed & dispatch not possible until rectification complete.
Ok - so when to use which, bearing in mind you ALWAYS refer to the 'DDG' (seeing as it is made up of both the MEL & CDL)
(1) On the walk-around you spot a pylon access panel missing. You open up the DDG, and go to the CDL within that & locate the info respective to said missing panel. Be sure to read all the introductory notes to the CDL, as >1 issue may be cumulative, ie have an ever-degrading effect on aircraft performance. (or eg a max of 3 related CDLs may only be allowed)
(2) An equipment (MEL) issue is not so straight forward, and divided into whether you're at:
- gate
- start (or moving under your own power)
- T/O thrust set
- less than 80 kts
- less than V1
- ie in line with the various EICAS Messages.
In essence:
(a) On the gate you note a STATUS MSG. These ARE relevant at this point in your 'flight', and WILL need reference to the MEL to ascertain whether you may depart or not.
After Engine start (or moving under your own power (dependant upon which definition your MEL uses) STATUS messages no longer require reference to the MEL and you may simply continue.
(b) Whilst taxing out you get an ADVISORY EICAS eg "L Pack Inop" - ie a higher level message than Status. Stop, and first carry out the appropriate (QRH) drill, and thence you MUST refer to the MEL. If it says "No Dispatch" - return to gate. If it allows dispatch but with Operational (O) considerations then you, as a pilot must apply those, eg limit your subsequent flight to FL350 and continue the taxi & take-off. (or return to gate for eg more fuel if that if the Flight level too limiting). If it allows dispatch but with Maintenance (M) considerations then you MUST return to stand for applicable engineering works to be performed (eg inhibiting valves.... whatever). No options here (M), as only a qualified engineer may do this work and subsequently sign off the aircraft as fit for flight.
(c) After T/O thrust is set you get ADVISORY (eg) PACK INOP. Do nothing, continue the take off, and only at a safe time, clear of terrain, high workload etc action the QRH. No need to consult the MEL as once T/O thrust was set you had 'dispatched' in terms of ADVISORY messages. Airmanship may suggest you 'educate' yourself by reference to the MEL when time is spare - but you certainly don't have to.
(d) Anytime below 80kts you get an EICAS CAUTION (eg FWD CARGO DOOR). Stop the aircraft (including reject the T/O) and then apply the appropriate QRH. With that out the way you then MUST open up the MEL to confirm whether the flight can continue or whether a return to stand is required. (it'll be obvious!)
(e) Anytime below V1, you get a WARNING EICAS. Stop the aircraft (inc reject if on the T/O roll), apply MEMORY / Reference items, and thence you MUST open up the MEL to determine whether dispatch is subsequently allowed. (it'll be obvious!)
Summarising...between..
Gate & Engine start / Taxy - all EICAS Status & above need MEL reference
Eng start / Taxy & Takeoff thrust set - all EICAS Advisory & above need MEL ref.
Takeoff thrust set & 80 kts - all EICAS Caution & above need MEL reference.
Above 80kts & <V1 - only EICAS Warning need MEL reference
>v1 the aircraft has dispatched in all events & nil reference to the MEL required.
So... a bit of a minefield? No, .... not if you apply your knowledge of EICAS message philosophy versus Boeings advices on continuing / rejecting flight. Hope this helps.
Last edited by Static in the Attic; 11th Jun 2012 at 14:09.
Here, read this about when to "use" the MEL.:---
CRITERIA FOR DISPATCH (COMMANDER RESPONSIBILITY) MEL conditions and limitations do not relieve the Commander from determining that the aircraft is in a fit condition for safe operation with specific unserviceablities. If a failure occurs after the start of taxi and before the start of the take off roll, any decision to continue the flight shall be subject to the Commanders judgment and good airmanship. The applicable ECAM/Operations Manual procedures shall be consulted and the Commander should refer to the MEL before any decision to continue the flight is taken. It is within the authority of the Commander to accept a defect without consulting a ground engineer after the doors are closed provided the defect does not require a maintenance (M) specific procedure and it is covered in the MEL. No flight shall take place with any item of aircraft equipment inoperative or outside the requirements of the Operations Manual, if in the opinion of the Commander the lack of such equipment or the relaxing of an Operations Manual requirement will jeopardize the safe conduct of the flight. The decision of the Commander to have allowable inoperative items corrected prior to flight will take precedence over the provisions contained in the MEL. The Commander may request requirements above the MEL, whenever in his judgement such added equipment is essential to the safety of a particular flight under the conditions prevailing at the time. The MEL does not take into account multiple unserviceabilities. Therefore, before dispatching an aircraft with multiple inoperative MEL items, it must be assured that any interface or interrelationship between inoperative items will not result in a degradation in the level of safety and/or unduly increase crew workload. When assessing the effect of multiple unserviceabilities, in particular those involving related systems, it is essential for the Commander to exercise good judgement based on the specific circumstances at the time, including en-route airport availability, navigation facilities and weather conditions. The Commander must be aware of the operational and technical consequences of a given failure and must satisfy himself that the failed component or system is properly isolated..
CRITERIA FOR DISPATCH (COMMANDER RESPONSIBILITY) MEL conditions and limitations do not relieve the Commander from determining that the aircraft is in a fit condition for safe operation with specific unserviceablities. If a failure occurs after the start of taxi and before the start of the take off roll, any decision to continue the flight shall be subject to the Commanders judgment and good airmanship. The applicable ECAM/Operations Manual procedures shall be consulted and the Commander should refer to the MEL before any decision to continue the flight is taken. It is within the authority of the Commander to accept a defect without consulting a ground engineer after the doors are closed provided the defect does not require a maintenance (M) specific procedure and it is covered in the MEL. No flight shall take place with any item of aircraft equipment inoperative or outside the requirements of the Operations Manual, if in the opinion of the Commander the lack of such equipment or the relaxing of an Operations Manual requirement will jeopardize the safe conduct of the flight. The decision of the Commander to have allowable inoperative items corrected prior to flight will take precedence over the provisions contained in the MEL. The Commander may request requirements above the MEL, whenever in his judgement such added equipment is essential to the safety of a particular flight under the conditions prevailing at the time. The MEL does not take into account multiple unserviceabilities. Therefore, before dispatching an aircraft with multiple inoperative MEL items, it must be assured that any interface or interrelationship between inoperative items will not result in a degradation in the level of safety and/or unduly increase crew workload. When assessing the effect of multiple unserviceabilities, in particular those involving related systems, it is essential for the Commander to exercise good judgement based on the specific circumstances at the time, including en-route airport availability, navigation facilities and weather conditions. The Commander must be aware of the operational and technical consequences of a given failure and must satisfy himself that the failed component or system is properly isolated..
Last edited by nitpicker330; 14th Jun 2012 at 11:06.
The above came from the front pages ( introduction ) to our companies approved Airbus MEL document.
The Boeing DDG has basically the same words at the front.
So, get a copy of your MEL/DDG and read it.
The Boeing DDG has basically the same words at the front.
So, get a copy of your MEL/DDG and read it.
Last edited by nitpicker330; 14th Jun 2012 at 11:08.
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MEL, CDL an DDG
Well spoken Nitpicker, you are correct. If I may be so bold to add to your comments the MEL is a based on the Master MEL which is FAA approved. The CDL is part of a Boeing AFM and again is FAA approved. The Dispatch Deviation Guide from Boeing is NOT FAA approved, but does give you much more info, especially with regards to maintenance requirements and Flight Operations requirements. You can use the DDG for the aircraft if so approved by your authority, but you need to know your aircraft as the DDG covers the entire series of say the B747 classic. MEL justs give the minimum required for dispatch. Most companies will allow flight crew to reference it prior to takeoff, but you are correct in the fact that the FCOM procedures dictate.
Safe flying
Safe flying
That was one of the best answers to a question I've read. Thanks for that.Join Date: Jan 2000
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Static in the Attic provides a very comprehensive answer.
Although in our type of Operation, reference is made first to MEL.
This is because the CDL refers to operational variations and only lists those defects which have them. There thus can be MEL items without CDL reference (think of a single Nav Position Light Bulb u/s), which in turn is why the CDL is contained behind the MEL in the DDG or DDPG.
If an MEL item has remarks starting with (M) it requires engineering to do some things.
If an MEL item has remarks starting with (O) it has an operational effect, thus a matching CDL item.
If it has merely text there is no maintenance to be performed, no operational effects, thus can be recorded and deferred without further action until the repair interval is due as per MEL.
Although in our type of Operation, reference is made first to MEL.
This is because the CDL refers to operational variations and only lists those defects which have them. There thus can be MEL items without CDL reference (think of a single Nav Position Light Bulb u/s), which in turn is why the CDL is contained behind the MEL in the DDG or DDPG.
If an MEL item has remarks starting with (M) it requires engineering to do some things.
If an MEL item has remarks starting with (O) it has an operational effect, thus a matching CDL item.
If it has merely text there is no maintenance to be performed, no operational effects, thus can be recorded and deferred without further action until the repair interval is due as per MEL.
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I don't think a MEL has matching CDL items?
Static in the Attic has it right; CDL is just physical deviations from a standard airframe.
The (m) means maintenance needs to do a procedure (e.g. physically lock a valve closed) and the (o) means there is an operational procedure to be done by either maintenance if available and/or crew. An example of an (o) is to switch off HF radios if equipment cooling is not working; how can this have a matching CDL item?
Static in the Attic has it right; CDL is just physical deviations from a standard airframe.
The (m) means maintenance needs to do a procedure (e.g. physically lock a valve closed) and the (o) means there is an operational procedure to be done by either maintenance if available and/or crew. An example of an (o) is to switch off HF radios if equipment cooling is not working; how can this have a matching CDL item?
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To put it simply, MEL + CDL = DDG.
MEL = Minimum Equipment List. It has to do with internal systems and configurations.
CDL = Configuration Deviation List. It has to do with external parts [missing].
Your airline likely has a DDG (Dispatch Deviation Guide). It has sections for MEL and CDL. Seldom do they overlap. Both have to be checked if you lose something prior to takeoff.
MEL = Minimum Equipment List. It has to do with internal systems and configurations.
CDL = Configuration Deviation List. It has to do with external parts [missing].
Your airline likely has a DDG (Dispatch Deviation Guide). It has sections for MEL and CDL. Seldom do they overlap. Both have to be checked if you lose something prior to takeoff.
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IF you cannot find any reference to your 'missing part' - eg Left Wing Detached - then that deviation is not allowed & dispatch not possible until rectification complete.
Here's one, B744 - brake unit has 2 wear indicators, on your walkaround you find 1 missing, it's not in the MEL/CDL/DDG, can you depart without having to lock out or replace the brake, after all it's not in the DDG?
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Deferment.
Looks like we're going to have to include the AMM and possibly the SRM as well eh Spanners? It's going to need a "B" licence to sort it out though, it's beyond the remit of the drivers!
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The MEl/CDL/DDG does not cover everything, just because its not in there does not mean you can not fly.
Here's one, B744 - brake unit has 2 wear indicators, on your walkaround you find 1 missing, it's not in the MEL/CDL/DDG, can you depart without having to lock out or replace the brake, after all it's not in the DDG?
Here's one, B744 - brake unit has 2 wear indicators, on your walkaround you find 1 missing, it's not in the MEL/CDL/DDG, can you depart without having to lock out or replace the brake, after all it's not in the DDG?
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I concur with Intruder.
If it isn't in the CDL/MEL then you need a release.
CDL covers bits missing MEL covers bits not working. Both are applicable before the aircraft taxis under it's own power with the intention of taking off.
Your company may have other more restrictive definitions in your approved manuals.
If it isn't in the CDL/MEL then you need a release.
CDL covers bits missing MEL covers bits not working. Both are applicable before the aircraft taxis under it's own power with the intention of taking off.
Your company may have other more restrictive definitions in your approved manuals.
EASA land rules
GM1 ORO.MLR.105(a) Minimum equipment list
GENERAL
The MEL is a document that lists the equipment that may be temporarily inoperative, subject to certain conditions at the commencement of flight.
AMC1 ORO.MLR.105(d)(3) Minimum equipment list
EXTENT OF THE MEL
The operator should include guidance in the MEL on how to deal with any failures that occur between the commencement of the flight and the start of the take-off . If a failure occurs between the commencement of the flight and the start of the take-off , any decision to continue the flight should be subject to pilot judgement and good airmanship. The pilot-in-command/commander may refer to the MEL before any decision to continue the flight is taken.
GM1 ORO.MLR.105(a) Minimum equipment list
GENERAL
The MEL is a document that lists the equipment that may be temporarily inoperative, subject to certain conditions at the commencement of flight.
AMC1 ORO.MLR.105(d)(3) Minimum equipment list
EXTENT OF THE MEL
The operator should include guidance in the MEL on how to deal with any failures that occur between the commencement of the flight and the start of the take-off . If a failure occurs between the commencement of the flight and the start of the take-off , any decision to continue the flight should be subject to pilot judgement and good airmanship. The pilot-in-command/commander may refer to the MEL before any decision to continue the flight is taken.