Inoperative Equipment
Summary
Updated 4/8/2022 Read time: 10 min
A Minimum Equipment List (MEL) Letter of Authorization (LOA) is necessary for a turbine aircraft to depart with inoperative instruments or equipment. A Special Flight Permit is needed if the item cannot be deferred via a MEL. The primary source of information is AC 91-67.
Details
Inoperative Equipment Options
Can you fly with inoperative equipment on your aircraft?
That depends on the type of aircraft you’re flying, the kind of operation, what broke, when it broke, and what authorizations you have.
There are three main buckets that operators can dip into to address inoperative instruments and equipment that are not essential to safe flight:
Kinds of Operations Equipment List (KOEL)
Minimum Equipment List (MEL)
Ferry Permit
Regardless of the bucket, all three only address inoperative equipment when on the ground. Once you are airborne, this all goes out the window. When that happens, refer to CFR 91.3 and 91.7.
In summary, a Pilot in Command can deviate from the regulations in an emergency (if necessary), and if an aircraft becomes un-airworthy in flight, discontinue the flight.
Additionally, all three maintenance deferral processes are just that: deferred maintenance. None of them are solutions to operate indefinitely with broken equipment. The idea is to allow a flexible means of getting the aircraft into maintenance.
Finally, “inoperative” is a technical term that has a different meaning than missing or out-of-date equipment. You will have to dive into the details of your aircraft regarding missing equipment. Out-of-date items (like databases) are not broken, so they are beyond the scope of these procedures.
KOEL
A KOEL is a shorthand description of a process to ensure all necessary equipment works before a flight. You need to consult several sources of information in this process, one being the KOEL published by the manufacturer in the Aircraft Flight Manual. All the sources to consult are:
KOEL (AFM or POH). Lists equipment required for VFR day, VFR night, IFR, Icing, and RVSM operations.
CFR 91.205. A TOMATO FLAMES, FLAPS, GRABCARD, the lesser-known VOR (if using radio navigation), and DME/ RNAV above FL240.
Airworthiness Directives (ADs) applicable to the aircraft that prescribe necessary equipment.
Once you have determined that what is inoperative or missing is not required by any of the above, you remove or deactivate it and placard it inoperative.
Most pilots learn to use a KOEL before a MEL because of the type of aircraft they start out flying, but the KOEL is an exception to the MEL in the regulations. The source material is CFR 91.213.
This exception lists aircraft that it applies to in 91.213 (d)(1):
(1) The flight operation is conducted in a –
(i) Rotorcraft, non-turbine-powered airplane, glider, lighter-than-air aircraft, powered parachute, or weight-shift-control aircraft, for which a master minimum equipment list has not been developed; or
(ii) Small rotorcraft, non-turbine-powered small airplane, glider, or lighter-than-air aircraft for which a Master Minimum Equipment List has been developed
Translation: you can only use a KOEL on piston airplanes, not turboprops or jets. If you want the flexibility to fly with inoperative equipment, you need a MEL.
Why do Pilatus and other turbine aircraft manufacturers publish KOELs in their Aircraft Flight Manuals? Regulations are different around the world, so they produce it to fly anywhere.
MEL
While a KOEL tells you what needs to be working to fly, a MEL tells you what can be inoperative and still fly. Like the KOEL, a MEL is a compilation of documents, one of which is the MEL. It is specific to an aircraft’s make, model, and serial number series.
The FAA works with aircraft manufacturers to produce and publish a Master Minimum Equipment List (MMEL). YOU CAN LOOK UP YOUR AIRCRAFT HERE. Think of an MMEL as a list of equipment with the FAA’s blessing of not working (assuming conditions are met and procedures are followed). The number one condition is that the aircraft operator acquires a letter of authorization from the FAA to conduct operations with a MEL.
Aircraft Operator is another technical term for someone who has operational control of an aircraft for any given flight. The aircraft operator may differ from the aircraft owner, as is typical when a separate LLC owns an airplane. A smell test to determine who the operator is: Who pays for the pilots and fuel?
Some aircraft have multiple Aircraft Operators, such as a dry lease agreement with several lessees. In this case, each operator must get a separate MEL LOA. There is a lot of paperwork, but it brings up a good point: an LOA is authorization for the operator, not the aircraft. The FAA wants to ensure the people utilizing a MEL understand the procedures.
The two MEL LOA types are D095 (MMEL) and D195 (MEL). A D095 is simpler because it uses the published MMEL as the operator’s MEL. The D195 MEL is a customized document, so it requires more FAA FSDO research to ensure operators meet an acceptable level of safety. What you gain in customization, you lose in time, not only the additional research but the backlog of applications due to foreign aviation authorities.
EASA (Europe’s FAA) disapproves of using D095 MELs for several reasons:
An MMEL is designed for a type, not a specific serial number, and may not address equipment installed on a particular aircraft.
MMELs list items " as required by CFR 14” that may be unfamiliar and need to be made explicit.
After receiving a D095 MEL, the operator needs to develop M&O procedures, but ramp checks reveal that this is not always being done.
Generic MMELs do not address the specific kinds of operations conducted, special approvals and authorizations, or the operating environment of MEL holders.
The FAA’s stance is that once you have a D095, you can remove non-applicable items from the MMEL, spell out CFR references, create your M&O procedures, and remove procedures not relevant to your kind of operation. You are authorized to do everything EASA wants, but in practice, EASA is finding these are not being completed. The FAA has rewritten AC 91-67, but EASA and the FAA have agreed to disagree regarding D095 MELs meeting ICAO standards.
A D195 MEL is preferred for operators traveling internationally. Since these applications are backlogged, a D095 MMEL can get you up and running while the D195 is in process.
Back to what documents make up a MEL:
FAA MEL LOA paperwork (the actual FAA LOA approval)
Either an FAA MMEL or Custom MEL document
FAA MMEL Policy Letter 25: MEL Definitions (Part 91 operators)
FAA MMEL Policy Letter 36: MEL Approval and Preamble (Part 91 operators)
MEL Operations Manual
Maintenance and Operations Procedures Document (M&O)
Discrepancy Log
Getting a MEL
The good news is that most of the above documents are produced for you. The FAA issues its MEL LOA paperwork upon approval. The FAA MMEL (D095 applications), FAA Policy Letter 25, and 36 are publicly available. What remains involves writing heavy technical manuals.
A good MEL operations manual can show the FAA that you, as the operator, understand how to utilize the documents, potentially streamlining LOA approval. It will also be a good reference source for ongoing operations.
In a MEL document, some items reference additional maintenance or operating procedures that need to be accomplished. This is what the M&O document is for. It fleshes out specific tasks to complete before dispatch. The M&O document is unnecessary for the LOA application, but any item with these procedures is not deferable until the operator develops the procedures.
The discrepancy log becomes part of the aircraft’s permanent maintenance records. On a more day-to-day level, it is the primary means of communicating the aircraft’s maintenance status to any crewmember at their station.
Once your documents are in place, the next step to getting your MEL LOA is to apply to YOUR LOCAL FAA FSDO. You submit the documents, and the Principle Operations Inspector (POI) assigned to you will review the application documents in the order they receive them. Some FSDOs have a 1-2 week turn time, while others have the queue backlogged for 6-8 weeks.
The POI may want revisions to a document and may wish to discuss over the phone with the operator to ensure they understand the LOA responsibilities. Once satisfied, they will issue the FAA MEL LOA paperwork to the operator. The operator needs to sign and return the document, and then they are ready to start deferring equipment.
Using a MEL
Once you have received MEL LOA approval, you, as the operator, are responsible for keeping the document current. For example, personnel or aircraft base changes must be communicated with the LOA's POI. Additionally, if the FAA issues a revised MMEL or Policy Letter, it should be updated in LOA documents.
Finally! What do you need to do when things are inoperative?
When you discover inoperative instruments or equipment, it can fall into one of four buckets.
Not included on the MEL. Your aileron fell off. The yoke is missing, etc. Items not addressed in the MEL are non-deferrable. Write it up in the discrepancy log, placard it as necessary, and arrange for maintenance or a ferry permit (if able).
MEL procedures item. The MEL contains all the necessary procedures to defer the item. Comply with the stated procedure, write it up in the discrepancy log, and placard it as required.
As Required by CFR 14 item. When the MEL specifies “As Required by CFR 14,” additional research is necessary to determine if you can fly without violating the regulations. For example, you can’t use your MEL to fly into a towered airport if you don't have two-way radio communication equipment. Comply with the stated procedure and applicable regulations, write it up in the discrepancy log, and placard it as necessary.
M&O Procedures document. The MEL has an (M) or (O) reference. Look up the appropriate procedure in the M&O document, comply with the stated procedure in the MEL and M&O document, write it up in the discrepancy log, and placard it as necessary.
One final bit of good news for Part 91 operators: MMELs list A, B, C, and D repair category intervals, but they are not applicable for 91 Operations. However, you must comply with the stated limitations on flights, legs, cycles, hours, days, etc.
Special Flight Permit
The remaining deferral option, Ferry Permit, can still be used if you have a MEL. This is the final resort if your inoperative item is not on the MEL, your annual is out of date, or there is some other unique situation. The goal is to fly the aircraft to maintenance legally and safely.
Working directly with a DAR (Designated Airworthiness Representative) or VIA AN ONLINE APPLICATION, you detail the situation and plan of action. The SFP application needs to be sent to the local FSDO of the airport from which you plan to depart. There will usually be limitations on the operations, such as crew only, daytime only, specific routes to maintenance, and expiration on the permit.
Some MORE GOOD FAA INFORMATION ABOUT THE PROCESS IS HERE.
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SEARCH FOR YOUR AIRCRAFT’S FAA MMEL HERE
