View Full Version : MEL DDG CDL confusing!?
11th Jun 2012, 11:06
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 ...........
11th Jun 2012, 11:18
Not sure what DDG is?
The CDL would only be used before dispatch; if something falls off your aircraft you will be going back to the gate!
The MEL stops being applicable once the aircraft moves under its own power so there is no legal requirement to refer to it once you've started taxiing. However good airmanship suggests you should refer to it...
11th Jun 2012, 11:21
I only know DDG stand for dispatch deviation guide.thanks!
11th Jun 2012, 11:50
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
11th Jun 2012, 13:08
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:
- 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.
(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!)
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.
11th Jun 2012, 14:10
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
12th Jun 2012, 04:40
I can't pull and reset CB either. Only can see CB pop up by itself .
12th Jun 2012, 08:57
sky-738 I can't pull and reset CB either. Only can see CB pop up by itself .
Just like pop corn:E
13th Jun 2012, 16:08
Whether you use the combined DDG, or MEL and CDL, they have 1 thing in common, it's always written for "interpretation":oh:
14th Jun 2012, 11:01
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..
14th Jun 2012, 11:08
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:
15th Jun 2012, 15:49
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.