MEL DDG CDL confusing!?

[sky-738]

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 ...........

[sky-738]

I only know DDG stand for dispatch deviation guide.thanks!

[john_tullamarine]

Some reading material.

(a) MEL/CDL (http://fsims.faa.gov/WDocs/8900.1/V04%20AC%20Equip%20&%20Auth/Chapter%2004/04_004_001.htm)

(b) DDG is an OEM animal. Some Boeing information can be found here (http://www.boeing.com/commercial/aviationservices/brochures/ddg.pdf)

[Static in the Attic]

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.

[de facto]

DDG also allows you to make sure maintenance did the proper securing...ie CB pulled and collared,INOP sticker and whatnot:E

Not like i couldnt pull and secure a CB myself:p

[sky-738]

I can't pull and reset CB either. Only can see CB pop up by itself .

[de facto]

sky-738 I can't pull and reset CB either. Only can see CB pop up by itself .


Just like pop corn:E

[Piper19]

Whether you use the combined DDG, or MEL and CDL, they have 1 thing in common, it's always written for "interpretation":oh:

[nitpicker330]

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..

[nitpicker330]

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. :ok:

[flyboyone]

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

[claraball]

To Static in the Attic:DThat was one of the best answers to a question I've read. Thanks for that.:D

[Skyjob]

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.

[Piper19]

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?

[Intruder]

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.

[spannersatcx]

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.
and therein lays one of your problems, because that simply is not true. 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?

[yotty]

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! :ok:

[Intruder]

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?
AFAIK, if the DDG gives no relief, you cannot fly without a special Engineering Order approved by the FAA (N-reg).

[FE Hoppy]

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.

[Miles Magister]

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.

[spannersatcx]

AFAIK, if the DDG gives no relief, you cannot fly without a special Engineering Order approved by the FAA (N-reg).
Its allowable iaw with the AMM, as yotty says it can be deferred nothing special needed.

[Piper19]

Correct, and many companies have two sorts of sheets for deferring defects. MEL and CDL go to one kind (often labelled performance related items or DDG items), and others like AMM, SRM, ... go into the second kind (labelled non-performance or non-MEL related items).
Missing brake wear indicators happen and I have never grounded a ship for that.

[Intruder]

Its allowable iaw with the AMM, as yotty says it can be deferred nothing special needed.
The AMM is not made available to pilots at my company, so I'd have to see it in writing first...

[yotty]

Intruder, I assume you have appropriately Licenced and Authorised Engineers that look after your aircraft. These people will sort it for you. :ok:

[spannersatcx]

That's why we can sign a CRS IAW AMM and raise a DD IAW the AMM, fortunately we have a delay code for flt crew querying DD's!

[TURIN]

That's why we can sign a CRS IAW AMM and raise a DD IAW the AMM, fortunately we have a delay code for flt crew querying DD's!

Priceless!:}:D

[Intruder]

What's a CRS and a DD? Is that CAA or EASA spec? What's the FAA equivalent - the EO I mentioned earlier?

[TURIN]

CRS..Certificate of Release to Service. The signature sign off from the Eng/Mech to legally certify that all work performed was done so IAW the relevant Procedures and documentation using the correct parts and tooling etc.
DD..Deferred Defect. Often referred to as a Hold Item or ADD Acceptable Deferred Defect.

[Exup]

Intruder, CRS = AWR, DD = DMI not to difficult really.

[Intruder]

Yes, and a DMI requires a MEL/CDL item or Engineering Order for reference...

There may be some esoteric exemptions somewhere, but I am not aware of them.

[spannersatcx]

from the MEL:
For the sake of brevity, the MEL does not include all the obviously required items such as wings, rudders, flaps, engines, landing gear, etc. or any structural damage.
However, some of the obviously required items are included to remove any doubts regarding their importance of their being operative.
The MEL does not include items which do not affect the airworthiness if the aircraft such as galley equipment, entertainment systems, passenger convenience items, etc.
It is important to note that;
“ALL ITEMS WHICH ARE RELATED TO THE AIRWORTHINESS OF THE AIRCRAFT AND ARE NOT INCLUDED ON THE LIST ARE REQUIRED TO BE OPERATIVE AT ALL TIMES”.
Exceptions are items which have serviceability specifications contained in the manufacturer's Aircraft Maintenance Manual (AMM), Structural Repair Manual (SRM) or other approved manufacturer's manual/drawings. In this case Engineering will advise dispatchability of such items with the relevant extracts from AMM, SRM or other approved manufacturer's manual/drawings.

[Intruder]

That statement does not appear in our DDG. Instead,
Equipment not required by the operation being conducted and equipment in excess of FAR requirements are included in the MEL with appropriate conditions and limitations. The MEL must not deviate from the Aircraft Flight Manual Limitations, Emergency Procedures or with Airworthiness Directives. It is important to remember that all equipment related to the airworthiness and the operating regulations of the aircraft not listed on the MMEL must be operative.
There IS a process to defer Nonessential Equipment and Furnishings (NEF) that do not appear in the MEL, CDL, or NEF list:
Controller will use the Maintenance Control Evaluation Process flow chart in conjunction with the Maintenance Controllers NEF Check list (T2091) to determine if the item can be deferred as an NEF item (see “Maintenance Control Evaluation Process” on page 4.00-01-00.4.) If the item meets the criteria to be deferred as an NEF item per the flow chart, then the Maintenance Controller will add the item to Form M2006 (see form sample, “Sample New NEF Item Record Form (M2006)” on page 4.00-01-00.6), and obtain the Maintenance Control Duty Managers approval. The item will then be deferred as an NEF item with a category as applicable.
The end items on the checklist that apply are:
Step 5
Can source (underlying cause) of the discrepancy affect equivalent levels of safety?
UNCERTAIN or NO

Step 6
If applicable, can source of the discrepancy be isolated from other systems with maintenance procedures?
YES or NOT APPLICABLE

Step 7
Defer the item in accordance with the approved NEF program and add item to NEF list
So (at least in FAA land), while a deferral per the AFM might be accomplished as you suggested, it must be done per the approved NEF listing procedure. It is NOT simply up to the mechanic/engineer on the scene.

I realize that procedures may differ in other jurisdictions.

[yotty]

We are not saying it is up to the mechanic/engineer on the scene. We interpret the various documentation and certify accordingly. You sound as if we make it up as we think fit! This is not the case. At least that how it happens in EASA land!

[spannersatcx]

We also have NEF's in our MEL/DDG, but no requirement to call MC. If it is outside the MEL/DDG/CDL/AMM/SRM then we would go to our MC and get a DOI/Concession if allowable otherwise it gets fixed.
The difference I guess between the FAA way and EASA way is we are allowed to think for ourselves and use the rules/regulations/processes and procedures without the need to call MC, once we've exhausted all avenues we would call and take it from there.

[framer]

fortunately we have a delay code for flt crew querying DD's!
We need to remember that we are all on the same side.
I have worked as both Engineer and pilot, ( currently 737 skipper) and I really appreciate it when the Engineer understands me querying the resultant "fix" and takes time to explain his or her actions and point of view. We aren't privy to the same training and information and any non ATPL Engineer who thinks they understand the Captains role inside out is dreaming. ( and vice versa). Sometimes, before we elect to accept an aircraft and all that that entails we need to align information from the Engineer with knowledge we have ( eg fog forecast at destination, Lithium batteries in the hold, training taking place, notams regarding lighting/ Nav aids) and that may come across as pedantic to the Engineer sitting beside us in daylight with blue skies doing zero miles a minute.
Another element is that we may not know you. There are people ( Engineers & Pilots) who quite simply have sh1tty attitudes and only look ahead to the end of their shift rather than to the end of their career. Initially, we don't know if you are one of those ( it only takes a short conversation to determine if you are one of the true professionals, but determining if you're a drop kick can take a bit longer).
My point is, we are on the same side and any ' us v's them' attitudes are a waste of time and energy. It is easy to say fortunately we have a delay code for flt crew, but it is equally easy to say " I'm sick of having to radio for the Engineers to come to the plane and sign off the Maintenance Log correctly".
There is no point however. We just need to accomodate each others needs/ requirements while getting the job done.
Rant over. Time for another beer :)

[TURIN]

Fair points framer. It was just a bit of banter.

To continue.. my own personal experience regarding the different regs are that with FAA registered aircraft any maintenance/pilot write up has to be reported to the Maint Control Centre (MCC) and it is they who determine what action should be taken. The Mechanics do as they are told. In the rest of the world (EASAland and others that use the same system) the Engineer/Technician has been authorised to use the full range of documentation to certify and release the aircraft. That includes SRM, AMM, MEL/CDL etc. Of course if it's something very unfamiliar and finding the correct reference document is proving difficult and time consuming then a courtesy call to MCC is in order as they can offer advice and between yourselves can isolate the correct documention to use. That is why ALL action taken has to be recorded with a reference. That enables anyone further down the line to refer to the same documentation if clarification is required by a pilot or eng/tech etc.
Anything that is outside the limits of SRM/AMM/MEL etc will require an EO or other dispensation from a suitably authorised source such as the manufacturer or national regulator. Or we get our toolbox out and fix it.

[craftsman_fb]

First of all, there are only two manuals for any airplane that approved by the state's authority.
- Master Minimum Equipment List (MMEL)
- Airplane Flight Manuel (AFM)

FAA publishes the MMEL on their FSIMS website.
Flight Standards Information System (FSIMS) (http://fsims.faa.gov/PICResults.aspx?mode=Publication&doctype=MMELByModel)


(FAA) Operators use the MMEL as a reference for creating their own Minimum Equipment List (MEL), which is provided to their flight crews, line maintenance personnel, and/or flight operations personnel.

An Operator’s MEL cannot be less restrictive than the MMEL.

Both the MMEL and the MEL are legal documents that are either approved by Airworthiness Authorities.

The Configuration Deviation List (CDL) is a reference document that enables the aircraft to be dispatched, even if some secondary airframes, or engine, parts are missing. These parts may be detected during maintenance checks, or pre-flight exterior inspections.

The CDL is included in the Airplane Flight Manual (AFM) an appendix, and is approved by Airworthiness Authorities.

The Dispatch Deviations Guide (DDG) is intended to assist airline operations and maintenance organizations in developing the procedures required to operate the airplane in the various nonstandard configurations allowed by the Federal Aviation Administration (FAA) Master Minimum Equipment List (MMEL) and the Airplane Flight Manual (AFM) Appendix Configuration Deviation List (CDL).

From Boeing's DDG:
"Background;
The FAA publishes an MMEL for each airplane model that is written in a brief format that does not include the detailed procedures necessary to properly prepare and operate the airplane. The AFM Appendix CDL does not include illustrations for positive identification of secondary airframe and engine parts that may be missing for dispatch. Historically, operators have found difficulty in developing procedures and identifying missing parts. They have often consulted Boeing for guidance in these areas and as a result, this document was prepared for reference."

[raazaero123]

To Static in the Attic:That was one of the best answers to a question I've read. Thanks for that.

[Boeingchap]

There is a fundamental difference between Engineers releasing an aircraft under the MEL and Pilots consulting the MEL.
The engineer signs a CRS in the tech log , the CRS is for an INSPECTION and that the defect complies with the MEL.
Its the inspection that is the most important part of the process , and its this part that is missing when the pilot / maint control are involved without an engineer present .
99% of pilot /MEL situations are without an inspection being done - This creates the largest problem when using the MEL