What is it?
What is an MEL?
The Minimum Equipment List (MEL) enables the dispatch of an aircraft in a condition that ensures both safety and airworthiness, even when a specific system, functions, or equipment may be temporarily unavailable or inoperative.
Operational Flexibility
- Maintains revenue-earning operations without compromising flight safety.
- Allows deviation from the type certificate requirement of 100% functional equipment.
Key Limitations Without MEL
- Without the document, Air Carriers cannot deviate from the type certificate of the aircraft.
- Requires all equipment to be 100% functional, limiting operational adaptability, in other words, you can not apply 91.205 logic to a Part 135 operation.
MEL's Strategic Role and Operational Impact
- The MEL’s intent is not to grant permission to fly a broken or un-airworthy airplane to skirt around required maintenance. It is simply a method to safely defer the maintenance to another time to allow for relocation of the aircraft, parts to be delivered, and work to be scheduled, all without interrupting revenue service.
Supporting Documents
MEL Variations and Complimentary Documents
There are several differences in how each MEL is created and approved. MELs can be tail-specific or may apply to a whole fleet. In addition, MELs may be used for Part 121/135 purposes (to be accepted onto OpSpec D095), or they may be used for Part 91/125 operations, which is usually required by other international governing bodies (in which case LOA D195 is applicable).
The Minimum Equipment List does not constitute all equipment of the aircraft. Non-Essential Furnishings (NEF) is another document that accompanies the MEL. The NEF allows for the deferral of interior aircraft parts, such as broken coffee makers, microwaves, gasper valves, trim pieces, etc.
Another often confused document is the Configuration Deviation List (CDL). This document is separate from the MEL and deals with exterior parts that may affect the aircraft's performance. These include fairings, flashing and seals, wheel hub covers, etc. The aircraft manufacturer writes the CDL, where each missing item must be independently tested and often included in the Aircraft Flight Manual (AFM).
The Minimum Equipment List does not constitute all equipment of the aircraft. Non-Essential Furnishings (NEF) is another document that accompanies the MEL. The NEF allows for the deferral of interior aircraft parts, such as broken coffee makers, microwaves, gasper valves, trim pieces, etc.
Another often confused document is the Configuration Deviation List (CDL). This document is separate from the MEL and deals with exterior parts that may affect the aircraft's performance. These include fairings, flashing and seals, wheel hub covers, etc. The aircraft manufacturer writes the CDL, where each missing item must be independently tested and often included in the Aircraft Flight Manual (AFM).
Issues
Common Compliance Issues
Addressing compliance issues in aircraft operations is paramount for ensuring safety and regulatory adherence. The points below highlight these common pitfalls, offering insights to enhance operational compliance and safety.
- Keeping records and closely monitoring the due dates of each deferred item is vital. Updates should be made daily to the aircraft status sheet to ensure compliance and to avoid overflying any required maintenance. Many maintenance software on the market today automate the process and provide alerts.
- One often neglected aspect of deferring items is forgetting to adjust the aircraft equipment suffix on the Flight Plan. Dispatchers and Pilots should understand the applicable suffix to each aircraft. For example, a differed autopilot system will mean that flight into RVSM is prohibited, and thus, the “W” suffix must be removed from Block 10 of the ICAO flight plan.
- Another common issue stems from failing to understand aircraft systems and systems' interconnectivity. New aircraft are very complex machines, and seemingly unrelated systems can drastically affect each other. For example, a Radar Altimeter is connected to the aircraft’s E-GPWS system, which may be connected to the auto-throttle system and the weight-on-wheels sensor. Although you may be allowed to defer the two systems independently, it is imperative to understand the specific aircraft systems, as you might not be able to defer two interconnected systems if they are inoperative simultaneously.
- Write ups. The FAA continues to audit for poor, inaccurate, or completely missing maintenance write-ups; an issue that very much plagues the industry. A common problem with MEL usage is pilots see that an item is deferrable, assume that it carries no safety risk to fly with it inoperative, and fail to create a maintenance discrepancy write-up. This practice is illegal and goes against basic safety management concepts. For some operators that perform CASS (Continuing Analysis and Surveillance System), proper documentation and tracking of equipment is vital, as it ensures the aircraft receives the proper maintenance it needs.
MEL Order Form
Fill out the request form, and someone from our team will reach out for a quote. We will follow up with an additional questionnaire specific to your aircraft type.
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