Dispatch Deviations

FLIGHT OPERATIONS ENGINEERING

Dispatch Deviations

Brian J. Borthwick Performance Engineer Operations Course Boeing Commercial Airplanes September 2009

For Training Purposes Only

Copyright © 2009 Boeing

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Dispatch Deviations

Objectives • Understand the concept • Be aware of the development process • Become acquainted with the supporting documents • Consider the concept in practice • Appreciate the benefits



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Dispatch Deviations

Agenda • Introduction - Dispatch Deviation – Definition / Purpose - Benefits of Deferred Maintenance - Authorization for MEL Dispatch

• MEL Development / Approval Process • Document Overview - Master Minimum Equipment List (MMEL) - Dispatch Deviations Guide (DDG) - Airline's Minimum Equipment List (MEL)

• Performance Considerations For Training Purposes Only


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Dispatch Deviation – Definition / Purpose What is a Dispatch Deviation? • Approved revenue operation with inoperative or missing equipment



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Dispatch Deviation – Definition / Purpose The Minimum Equipment List (MEL) is the authorizing document • The MEL allows safe continued revenue operation with specific items of equipment inoperative (deferred maintenance) (All items related to airworthiness and not included in the list are required to be operative)



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Dispatch Deviation – Definition / Purpose Safety is maintained by: • Appropriate operational limitations • Transfer of the function to another operating component • Reference to other instruments • Limited repair interval



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Dispatch Deviation – Definition / Purpose NOT intended to allow continued operation for an indefinite period of time with inoperative equipment • Repair of deferred items should occur as soon as conditions permit



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Dispatch Deviations • Introduction - Dispatch Deviation – Definition / Purpose - Benefits of Deferred Maintenance - Authorization for MEL Dispatch




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Benefits of Deferred Maintenance The ability to defer maintenance is essential for continuity of operation • Offers Economic benefits due to optimization of: – Maintenance staff – Spares inventory – Maintenance facilities

• Helps Operators Maintain Dispatch Schedule – Minimizes mechanical delays – Minimizes disruption

• Improves Customer Schedule Convenience For Training Purposes Only


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Benefits of Deferred Maintenance Deferred Maintenance is vital to operations • Scheduled ground-time is based on minimum delays • Aggressive turnaround schedules preclude correcting discrepant items at the gate



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Benefits of Deferred Maintenance MEL Dispatch is Performed Often • Typical number of flight segments with deferred maintenance per the MEL: Yearly average = 20 to 50% Peak season = 50% or more (Items accumulate during the day and are cleared during overnight or next maintenance)



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Authorization for MEL Dispatch MEL Legal Authorization • FAR 121.628: Inoperable Instruments and Equipment “No person may takeoff an airplane with inoperable instruments or equipment installed unless the following conditions are met: (1) An approved Minimum Equipment List exists for that airplane.



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Authorization for MEL Dispatch The MEL and the Type Certificate • Airplane Type Certificate is not compromised by the MEL (FAR 121.628) – Adoption of a MEL item does not require re-certification of the design – The MEL is considered to be an approved change to the type design



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Authorization for MEL Dispatch The MEL and the Airworthiness Release • An airworthiness release is not compromised by the MEL (FAR 121.628) • Mechanic is not in violation of the FAR’s when deferring maintenance under the MEL – Airworthiness release states the work was done in accordance with the Operator’s manuals – MEL is one of the Operator’s approved manuals



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MEL Development / Approval Process Purpose / Benefit / Authorization

? s n o i t s e u Q For Training Purposes Only


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MEL Development / Approval Process Document Relationship Master MEL (MMEL) FAA Controlled

Configuration Deviation List (CDL)

Dispatch Deviations Guide (DDG)

AFM Appendix

Boeing Document

FAA Approved

Airline MEL Company Procedures

Company Policies Standards

Flight Ops

Coordination For Training Purposes Only


Maintenance

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MEL Development / Approval Process Process

Master MEL (MMEL) FAA Controlled



AFM Appendix

Boeing Document

FAA Approved



Flight Ops Maintenance



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MEL Development / Approval Process Master Minimum Equipment List (MMEL) Organizational Relationships

FAA

Manufacturer

Certification

Boeing Engineering

(FAR Part – 25)

FAA Engineering (ACO)

Operations (FAR Part – 121)

Boeing Flight Operations Engineering

FAA Aircraft Evaluation Group

(FLOE)

(AEG)

Airlines



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MEL Development / Approval Process Master Minimum Equipment List (MMEL) • FAA Document – Lists items of equipment which may be inoperative in revenue service – Published for a given airplane type (e.g., 767 MMEL covers –200/300/400ER, GE/PW/RR)

• Operators create and use their own Minimum Equipment List (MEL) based on the MMEL



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MEL Development / Approval Process MMEL For example…



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MEL Development / Approval Process Master Minimum Equipment List (MMEL) How does an item get in the MMEL? • The FAA Flight Operations Evaluation Board (FOEB) is responsible for the development and control of the Master MEL • No set interval for the FOEB to meet – Usually yearly for a new airplane type – As required for more mature designs



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MEL Development / Approval Process Master Minimum Equipment List (MMEL) FOEB members: • Chairman - typically the FAA Part 121 pilot assigned to the airplane • FAA Flight Test pilot most familiar with the airplane • FAA Air Carrier Maintenance and Avionics Specialist assigned to the Maintenance Review Board for the airplane • FAA Air Carrier Operations Specialist • Any other personnel deemed necessary by the chairman (often including another chairman) For Training Purposes Only


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MEL Development / Approval Process Master Minimum Equipment List (MMEL) Submittal of proposals: • U.S. Operators – Submit candidate items to FAA through their Principal Operations Inspector (POI)

• Non-U.S. Operators – Submit items through the airplane manufacturer



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MEL Development / Approval Process Master Minimum Equipment List (MMEL) Approval process: • FOEB meeting – Evaluate proposed items – Open to public

• FOEB Approval • Final review by FAA Headquarters (Washington) to ensure adherence to FAA policy • Entire revision process generally takes 6-8 months



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MEL Development / Approval Process Master Minimum Equipment List (MMEL) • FAA publishes the MMEL – Electronic Bulletin Board and Web (http://fsims.faa.gov)

• Distribution – Manufacturer typically distributes at least one copy to each Operator (Available on MyBoeingFleet.com) – U.S. Operators may also get a copy from their POI



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MEL Development / Approval Process Master Minimum Equipment List (MMEL) • Other regulatory agencies may issue MMEL supplement which modifies the FAA MMEL: – EASA (Europe) – Transport Canada – Aviation Register (CIS) – Others



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MEL Development / Approval Process Master Minimum Equipment List (MMEL) Fundamental Qualification Criterion: • An “acceptable level of safety” must be maintained considering the next critical single failure or event – Effect(s) on other systems/components and flight crew workload is considered – This does not mean the same standards for FAR Part 25 certification need to be met References: • FAA Engineering Order 8900.1, Flight Standards Information Management System (FSIMS) • MMEL Preamble



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MEL Development / Approval Process Master Minimum Equipment List (MMEL) Assessment Criteria: • Consequences of the Next Critical Failure (NCF) after dispatch with an inoperative system, component or function – Probability of occurrence for NCF is considered = 1.

• Interrelationships of inoperative system functions during the dispatch period, accounting for overall operational effects including pilot workload • Operational and engineering judgment of the consequences of dispatching the airplane with inoperative equipment is always considered and applied For Training Purposes Only


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MEL Development / Approval Process Master Minimum Equipment List (MMEL) General Criteria: • More restrictive operating limitations may be required • Airplane performance penalties may be required if performance is affected • Transfer of function to another operating component may be required • Additional or modified flight crew procedures may be required



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MEL Development / Approval Process Master Minimum Equipment List (MMEL) Limiting Factors: • Items will NOT be included in the MMEL if they: – Obviously compromise airworthiness – Obviously are not related to airworthiness

• The MMEL may not deviate from: – AFM Limitations – AFM Emergency Procedures – Airworthiness Directives (ADs)



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MEL Development / Approval Process Master Minimum Equipment List (MMEL)



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AFM Appendix

Boeing Document

FAA Approved






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MEL Development / Approval Process Configuration Deviation List (CDL) • FAA approved Appendix to the Airplane Flight Manual (AFM) • Allows operation with secondary airframe and engine parts missing • Alternate certification - No repair interval



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MEL Development / Approval Process Configuration Deviation List (CDL) Legal Authorization • FAA approved under Part 25 (certification) • Applicable to multiple configurations (minor models, different engine types)



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MEL Development / Approval Process Configuration Deviation List (CDL) Purpose: • The CDL allows safe continued operation with specific items of equipment missing (deferred maintenance) • Safety is maintained by: – Appropriate operational limitations – Performance penalties



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MEL Development / Approval Process Configuration Deviation List (CDL) Purpose (Cont’d): • CDL items are typically airplane exterior components such as: – Non-structural Fairings – Access Panels – Small Doors – Aerodynamic Seals – Light Lenses

• CDL items typically affect airplane drag or stall speeds



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MEL Development / Approval Process Configuration Deviation List (CDL) Submittal of proposals: • No regular, defined process • Operators submit items through the airplane manufacturer • Revised on as-needed basis



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MEL Development / Approval Process Configuration Deviation List (CDL) Approval process: • Boeing technical review • FAA Aircraft Certification Office (ACO) approval • AFM CDL Appendix revised



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MEL Development / Approval Process Configuration Deviation List (CDL) Part 25 Certification Criteria: • Airplane structure, systems, flying qualities not compromised • More restrictive operating limitations may be required • Performance penalties for missing items: – Takeoff limit weight – Landing limit weight – Enroute climb limit weight – Possible cruise fuel burn adjustment (DDG) For Training Purposes Only


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MEL Development / Approval Process Configuration Deviation List (CDL) • General Limitations – AFM Limitations are applicable except as amended by the CDL – Placards must list associated limitations for the pilot – Unless specified, parts from different subsystems may be missing – Penalties are cumulative – A 100 lb penalty will be applied for each “negligible” penalty in excess of three For Training Purposes Only


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MEL Development / Approval Process Configuration Deviation List (CDL) • General Limitations

(Cont’d)



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MEL Development / Approval Process Configuration Deviation List (CDL)



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AFM Appendix

Boeing Document

FAA Approved






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MEL Development / Approval Process Dispatch Deviations Guide (DDG) • The DDG is a guidance document published by the airplane manufacturer • The DDG is intended to assist airlines in developing procedures required to operate the aircraft in nonstandard configurations allowed by the MMEL and the CDL – A reference for development of the airline MEL



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MEL Development / Approval Process Dispatch Deviations Guide (DDG) Provides: • Suggested Operations (O) and Maintenance (M) procedures to meet MMEL requirements • Can include suggested position and content of placards • EICAS message list to assist in determination of possible MEL relief (except 737) • Can include drawings and pictures to assist in the location and identification of MMEL/CDL items



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MEL Development / Approval Process Dispatch Deviations Guide (DDG) Maintenance (M) and Operations (O) Procedures: • Technically correct to the best of Boeing’s knowledge; not FAA approved • Guidance information only; Operator must review for adequacy



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MEL Development / Approval Process Dispatch Deviations Guide (DDG) Maintenance (M) and Operations (O) Procedures (Cont’d): • Not necessarily the only valid procedures; – Operator may develop alternate procedures which better meet their unique needs (subject to local regulatory approval)

• If DDG information conflicts with the AFM, MMEL, or CDL, the FAA approved documents take precedence



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MEL Development / Approval Process Dispatch Deviations Guide (DDG) • Boeing publishes the DDG – Revision within 45 days after MMEL revision

• Distribution – Immediately available on MyBoeingFleet.com – Printed copies available upon request



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MEL Development / Approval Process Dispatch Deviations Guide (DDG)



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AFM Appendix

Boeing Document

FAA Approved

Airline MEL

Company Procedures





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MEL Development / Approval Process Airline Minimum Equipment List (MEL) • FAA requires each Operator to develop their own MEL – Fundamentally based on the MMEL (and DDG)

• The Master MEL is not intended for operational use – MMEL (and DDG) is a generic, reference document

• Operator’s MEL frequently differs in format and content from the MMEL/DDG



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MEL Development / Approval Process Airline Minimum Equipment List (MEL) • Customized for the airline’s specific configurations and operations: – Remove references to equipment that is not in the Operator’s fleet (e.g., engine types) – Specify equipment required by operating rules

• May be more restrictive than the FAA requirements • May contain equipment, which for administrative control reasons, are best placed within the MEL section of the Operator’s manual



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MEL Development / Approval Process Airline MEL Development and Approval Process (Typical) AIRLINE STANDARDS AND POLICIES

FLIGHT OPERATIONS PROCEDURES

MAINTENANCE OPERATIONS PROCEDURES

ADMINISTRATIVE

FLIGHT CREW

SECURING ITEMS

CONTROL

DISPATCH/FLIGHT FOLLOWING

PLACARDING

PREPARATION

PERFORMANCE PENALITIES

DEFERAL

DISTRIBUTION

ENROUTE EFFECTS

TRACKING

DOWNLINE NOTIFICATIONS

DOWNLINE NOTIFICATIONS

CLEARING

FAA MASTER MEL

MANUFACTURER’S RECOMMENDATIONS (DDG)

© 1999, 2001 J. Hessburg

AIRLINE MEL (DRAFT)


FAA APPROVAL


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Coordination

GENERAL PROCEDURES

AIRLINE MEL

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MEL Development / Approval Process Airline Minimum Equipment List (MEL) • Principal Operating Inspector (POI) or appropriate government agency will review the draft MEL for: – Nothing less restrictive than MMEL – Nothing contradicts AFM – Nothing violates AD’s – (O) and (M) procedures required by MMEL are adequate – There is a defined management process for the use and control of the MEL – Suitable training curriculum exists – Suitable manual material for use exists For Training Purposes Only


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MEL Development / Approval Process Airline Minimum Equipment List (MEL) At conclusion of review: • POI approves/signs the Operator’s MEL • Signs appropriate revision to the Operations Specification



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MEL Development / Approval Process Airline Minimum Equipment List (MEL)



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Document Overview Master Minimum Equipment List (MMEL) • Documentation • Usage



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Document Overview MMEL Definitions



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Document Overview MMEL Definitions 4. Each inoperative item must be placarded to inform and remind the crewmembers and maintenance personnel of the equipment condition. NOTE: To the extent practical, placards should be located adjacent to the control or indicator for the item affected; however, unless otherwise specified, placard wording and location will be determined by the Operator.



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Document Overview MMEL Definitions 5. "-" symbol in Column 2 and/or Column 3 indicates a variable number (quantity) of the item installed. . . . 9. "Flight Day" means a 24 hour period (from midnight to midnight) either Universal Coordinated Time (UCT) or local time, as established by the Operator, during which at least one flight is initiated for the affected aircraft.



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Document Overview MMEL Definitions 12. "Inoperative" means a system and/or component malfunction to the extent that it does not accomplish its intended purpose and/or is not consistently functioning normally within its approved operating limit(s) or tolerance(s). . . . 14. Inoperative components of an inoperative system: Inoperative items which are components of a system which is inoperative are usually considered components directly associated with and having no other function than to support that system. (Warning/Caution systems associated with the inoperative system must be operative unless relief is specifically authorized per the MMEL). For Training Purposes Only


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Document Overview MMEL Definitions 15. "(M)" symbol indicates a requirement for a specific maintenance procedure which must be accomplished prior to dispatch. Normally these procedures are accomplished by maintenance personnel; however, other personnel may be qualified and authorized to perform certain functions. Procedures requiring specialized knowledge or skill, or requiring the use of tools or test equipment should be accomplished by maintenance personnel. The satisfactory accomplishment of all maintenance procedures, regardless of who performs them, is the responsibility of the Operator. Appropriate procedures are required to be published as part of the Operator’s manual or MEL. For Training Purposes Only


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Document Overview MMEL Definitions 16. "(O)" symbol indicates a requirement for a specific operations procedure... Normally… accomplished by the flight crew; however, other personnel may be qualified and authorized … The satisfactory accomplishment of all procedures… is the responsibility of the Operator. Appropriate procedures are required to be published as a part of the Operator’s manual or MEL.

NOTE: The (M) and (O) symbols are required in the Operator’s MEL unless otherwise authorized by the Administrator. For Training Purposes Only


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Document Overview MMEL Definitions

Repairs should be made at the first opportunity …additional malfunctions could ground the airplane For Training Purposes Only


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Document Overview MMEL Definitions 23. Electronic fault alerting system – General a. BOEING (B-757/767, B-747-400, B-777) Boeing airplanes equipped with Engine Indicating and Crew Alerting Systems (EICAS), provide different priority levels of system messages (WARNING, CAUTION, ADVISORY, STATUS and MAINTENANCE). Any messages that affect airplane dispatch status will be displayed at a STATUS message level or higher. The absence of an EICAS STATUS or higher level (WARNING, CAUTION, ADVISORY) indicates that the system/component is operating within its approved operating limits or tolerances. System conditions that result only in a maintenance level message, i.e. no correlation with a higher level EICAS message, do not affect dispatch and do not require action other than as addressed within an Operator’s standard maintenance program. For Training Purposes Only


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Document Overview MMEL Definitions 25. "***" symbol in Column 1 indicates an item which is not required by regulation but which may have been installed on some models of aircraft covered by this MMEL. . . . 27. "Day of Discovery" is the calendar day an equipment/instrument malfunction was recorded in the aircraft maintenance log and or record. This day is excluded from the calendar days or flight days specified in the MMEL for the repair of an inoperative item of equipment. This provision is applicable to all MMEL items, i.e., categories "A, B, C, and D." For Training Purposes Only


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Document Overview MMEL Definitions 28. “Considered Inoperative”, as used in the provisos means that item must be treated for dispatch, taxi and flight purposes as though it were inoperative. The item shall not be used or operated until the original deferred item is repaired. Additional actions include: documenting the item on the dispatch release (if applicable), placarding, and complying with all remarks, exceptions, and related MMEL provisions, including any (M) and (O) procedures and observing the repair category.



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Document Overview MMEL Definitions 29. “Is not used” in the provisos, remarks or exceptions for an MMEL item may specify that another item relieved in the MMEL “is not used.” In such cases, crewmembers should not activate, actuate, or otherwise utilize that component or system under normal operations. It is not necessary for the Operators to accomplish the (M) procedures associated with the item. However, operational requirements must be complied with, and an additional placard must be affixed, to the extent practical, adjacent to the control or indicator for the item that is not used to inform crewmembers that a component or system is not to be used under normal operations.



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Document Overview MMEL Definitions 30. “Nonessential Equipment and Furnishings (NEF)” are those items installed on the aircraft as part of the original certification, supplemental type certificate, or engineering order that have no effect on the safe operation of flight and would not be required by the applicable certification rules or operational rules. They are those items that if inoperative, damaged or missing have no effect on the aircraft’s ability to be operated safely under all operational conditions.



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Document Overview MMEL Preamble

• The FAA MMEL is used as the basis for development of the Operator’s specific MEL • The Operator’s MEL may differ in format but cannot be less restrictive than the FAA MMEL



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Document Overview MMEL Preamble

(Cont’d)

• Operator’s MEL must provide suitable Placard, Operations and Maintenance procedures to maintain safety • Repairs shall be made at earliest opportunity • Operator is responsible for determining airplane condition is safe for operations • Operator is responsible for exercising the necessary operational control: Go/No-Go For Training Purposes Only


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Document Overview MMEL Example

• Maintenance action • Procedure change • Other equipment required • Other systems affected



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• Crew verification requirement • Flight restriction • Other equipment required • Same as above, plus: Maintenance verification requirement For Training Purposes Only


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Document Overview What about ETOPS, Cat I/II/III, RVSM, RNP, etc? • MMEL is not the sole source for all operational equipment requirements • MMEL contains some explicit operational restrictions: – “Except for ER…” – “…flight remains within 120 minutes of landing at a suitable airport”

• Many MMEL restrictions require further review for operational applicability: – “…approach minimums do not require its use” – “…enroute operations do not require its use” – “…other procedures do not require its use” – “…required by FAR” For Training Purposes Only


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Document Overview MMEL Example • Flight restrictions • Performance penalties • Minor model specific entries • Operational limitation • Other equipment required



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• Maintenance action – verification requirement • Use of other equipment required • Operational procedure • Operational limitation



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Document Overview MMEL Example • Operational implications: – ETOPS – Outstation facilities – Other inoperative items



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Document Overview Master Minimum Equipment List (MMEL)



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Document Overview Dispatch Deviations Guide (DDG) • Documentation • Usage



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Document Overview DDG Organization



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Document Overview DDG What is EICAS? • The Engine Indicating and Crew Alerting System (EICAS) is the primary means of displaying airplane system information to the flight crew • EICAS consolidates engine and subsystem indications and provides a centrally located crew alerting function • EICAS displays System Alerts (Warning, Caution, and Advisory), Communication Alerts, Memo messages, and Status messages



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Document Overview DDG EICAS Display



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Document Overview DDG EICAS Message Cross Reference List: • Provided as a “Quick Reference” between EICAS messages and Master Minimum Equipment List (MMEL) items which may provide dispatch relief • Applicable to 757, 767, 747-400, and 777



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Document Overview DDG EICAS Message Cross Reference List • None: No MMEL item (relief) for the failure condition indicated by this message • N/A: No MMEL item listed since message does not indicate a failure



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Document Overview DDG EICAS Message Cross Reference List • Message types



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Document Overview DDG EICAS Messages • Status messages indicate equipment faults which affect dispatch capability but are not necessarily identified by higher level EICAS messages • Maintenance messages do not affect dispatch but must be corrected in accordance with the Operator’s approved maintenance program • Normal crew procedures require checking status messages during cockpit preparation to determine airplane dispatchability For Training Purposes Only


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Document Overview DDG EICAS Messages

(Cont’d)

• Boeing philosophy: After engine start it is not necessary to check status messages – Operators may establish different policy for economic reasons

• Any message adversely affecting safe continuation of the flight or requiring crew attention, will appear as an EICAS alert message (WARNING, CAUTION, or ADVISORY)



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Document Overview DDG EICAS Messages

(Cont’d)

• What about a failure after engine start, but before takeoff ? – After engine start and prior to takeoff, any alert message requires accomplishment of the appropriate non-normal procedure by the crew – Upon completion of the non-normal procedure and prior to takeoff, the DDG or airline equivalent (company MEL) should be consulted to determine if dispatch relief is available



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Document Overview DDG EICAS Message Cross Reference List: • What do you do following display of a status message prior to engine start, or an alert message prior to takeoff ? – Determine if dispatch relief available

– Yes:

Apply MEL procedures and dispatch the airplane

– No:

Fix the problem



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Document Overview DDG Section 2 - MEL • Organized just like the MMEL • Duplication of FAA Definitions and Preamble • Items numbered same as MMEL



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Document Overview DDG Section 2 - MMEL • Top part is duplicate of MMEL • Followed by suggested placards and (M) and (O) procedures as appropriate



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Document Overview DDG Section 2 – MMEL • Duplicate of MMEL • Suggested (M) procedure (note engine-specific steps)



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Document Overview DDG Section 2 - MMEL • Suggested (O) procedure (note model-specific penalties)

• ETOPS planning information • Advisory information for flight crew



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Document Overview DDG Section 3 - CDL • Organized similar to the CDL AFM Appendix • Section contains a repeat of the AFM CDL limitations plus additional information on trip fuel adjustments for items



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Document Overview DDG Section 3 - CDL

Fuel burn adjustment (Increase flight planning fuel by 0.25%/1000 lb enroute climb weight penalty)



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Document Overview DDG Section 3 - CDL • General Locations



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Document Overview DDG Section 3 - CDL • Duplicate of AFM CDL Appendix information • Performance penalties if applicable • Location illustration • Illustration of item



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Document Overview DDG Section 4 - Miscellaneous



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Document Overview Dispatch Deviations Guide (DDG)



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Document Overview Airline MEL • In development and application of your MEL, coordination is the key



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Document Overview Airline MEL

Deferral Process (Typical) ITEM IN MEL?

LOGBOOK ENTRY

NO

FIX THE ITEM

YES

NOTIFY MAINTENACE

NOTIFY DISPATCH

NOTIFY PIC

YES

NO

DEFER?

MAINTENACE CONTROL

STATION MAINTENANCE

DISPATCH/FLIGHT FOLLOWING

NOTIFY MAINTENANCE PLANNING & RECORDS

DISARM SYSTEM

ROUTE PENALTIES

START THE CLOCK

PLACARD

PERFORMANCE PENALTIES

SCHEDULE WORK

TRANSFER ITEM TO DMI LOG & RELEASE AIRPLANE

Coordination

CLEAR DEFERRED LOG

RELEASE FLIGHT

© 1999, 2001 J. Hessburg



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Performance Considerations • Operations Impact • Method of Performance Adjustments • MEL Dispatch Example: Inoperative AC Pack(s) – 777

• MEL Dispatch with Multiple Inoperative Items



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Performance Considerations Airline Operations The required operations procedures may include: • Operations restrictions / limitations • Airplane performance adjustments



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Performance Considerations Airline Operations MEL dispatch configuration may affect: • Engine thrust – Decreased or Increased – Non-standard bleed air configuration or higher minimum idle

• Airplane drag - Increased – Delayed flap retraction, tail skid extended

Continued



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Performance Considerations Airline Operations MEL dispatch configuration may affect: (Cont’d) • Fuel burn – Increased from APU running, non-normal bleed configuration, etc.

• System operating times – Alternate flap retraction, manual spoilers, etc.

• Braking characteristics – Spoiler deployment, wheel brakes, thrust reversers, etc.



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Performance Considerations Method Adjustments are determined by Aerodynamics Engineering analysis with emphasis on: • Full range of the flight envelope − Temperature, altitude, wind, etc.

• Flight configurations − Flap setting, weight, etc.

• Airport characteristics − Runway length, slope, obstacles, etc.



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Performance Considerations Method Performance calculated using approved Airplane Flight Manual methods for the affected Flight segment: • Takeoff field length • Takeoff Climb • Obstacle clearance profile • Third segment distance • Maximum level off height • Enroute Climb • Approach/Landing Climb For Training Purposes Only


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Performance Considerations Method Boeing performs parametric analysis to determine how airplane performance limited weight requirements are affected



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Performance Considerations Method Performance adjustments are published in Boeing DDG as decrements to the performance limited weights • Most conservative weight decrement is identified for affected flight phase − Takeoff − Enroute Climb − Approach/Landing



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Performance Considerations Method In some cases, Operators may calculate and use less conservative performance adjustments for their specific operation when using Boeing performance analysis software, such as the Onboard Performance Tool (OPT)



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Performance Considerations Method Some adjustments require a more sophisticated model than is available in Boeing performance software and the Operator cannot improve on the DDG performance adjustment • Bleed or fan-air extraction • Drag increases



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Performance Considerations Example MEL Dispatch with inoperative AC Pack • Airplane: 777-200ER / GE90-94B / Under 632.5k lb • PACK L Status message displayed – Status message indicates a fault detected in left air conditioning pack



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Performance Considerations Example Cont’d Use EICAS Message Cross Reference List Cross Reference for PACK L Status Message is MMEL Item 21-51-01



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Performance Considerations Example Cont’d MMEL Item 21-51-01 • Flight Restriction • Operational Limitation • Performance Adjustment



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Performance Considerations Example Cont’d • Flight Restriction: – Restricted to an altitude of 35,000 ft to maintain an acceptable smoke clearance capability

• Operational Limitation: – NCF analysis indicates that if the remaining pack fails, it is possible for flight deck temperatures to reach levels that are unacceptable for extended flight beyond 60 minutes

• Performance Adjustment: – Reduced thrust when operating in single pack configuration.



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Performance Considerations Example Cont’d • Two factors result in reduced airplane thrust capability: – Single pack operating on higher flow schedule draws additional bleed air from the associated engine and reduces the associated engine's thrust capability. The Thrust Mode Computer (TMC) resets the thrust limit within the opposite engine's Electronic Engine Control (EEC) to maintain symmetric airplane thrust. – Single pack "works harder" on a high flow schedule so the ASCPC commands FAMV fully open. Associated EEC reduces thrust limit to protect EGT margin. Opposite engine EEC's thrust limit is reset by the TMC to maintain symmetric airplane thrust.



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Performance Considerations Example Cont’d • Operator required to ensure airplane meets all applicable performance requirements • Airplane performance adjustment expressed as: – Takeoff limited weight decrement (obstacle limited or climb limited) – Enroute Climb limited weight decrement – Landing limited weight decrement (approach climb or landing climb)

• Boeing DDG denotes adjustments to be considered in the airplane performance analysis For Training Purposes Only


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Performance Considerations Example Cont’d DDG Item 21-51-01 (O) Reduce performance limited weights by the amounts given in the table, or use packs off takeoff.



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Performance Considerations Multiple Inoperative Items • MEL dispatch with multiple inoperative items is potentially problematic – Complex system interrelationships and compounded effects – Affect on crew workload

• Dispatching with multiple inoperative items may be symptomatic of poor airplane maintenance – FAA MMEL Preamble requires reducing MEL items to a minimum



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Summary • Introduction - Dispatch Deviation – Definition / Purpose - Benefits of Deferred Maintenance - Authorization for MEL Dispatch




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Summary • Airplanes can be legally dispatched for revenue operations with inoperative equipment • MEL dispatch capability improves airline economics, operations, schedule • Safety is maintained by appropriate application of restrictions, limitations, and performance adjustments • Proper application of the MEL requires a thorough understanding of integrated airplane systems architecture – Incorrect application of performance adjustments could adversely affect safety, or over-penalize airplane performance adversely affecting airline economics For Training Purposes Only


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FLIGHT OPERATIONS ENGINEERING

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Dispatch Deviations

Performance Engineer Operations Course Boeing Commercial Airplanes



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Dispatch Deviations

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