MELs and the Part 91 King Air Owner-Operator

MELs and the Part 91 King Air Owner-Operator

Figure 1: FAR 91.213 (partial)

You are looking forward to taking your King Air out for a flight – the weather is clear, and your passengers are just as excited to get in the air as you are. However, during your preflight walkaround, you notice that one of your strobe lights is not working. Uh oh! There’s a possibility you won’t be making this flight after all. You start wondering if you are even legal to depart with this inoperative item. We’ll come back to this dilemma, but first let’s dust off the Federal Aviation Regulations and see what they have to say about flying with inoperative equipment.

A quick review of FAR 91.213 (see figure 1) reveals that “no person may take off in an aircraft with inoperative instruments or equipment installed unless the following conditions are met: (1) An approved Minimum Equipment List exists for that aircraft. (2) The aircraft has within it a letter of authorization, issued by the FAA Flight Standards district office…”

You’re probably wondering … “Even for a King Air?” Yes! FAR 91.213 further states that the only time you don’t need to have a Minimum Equipment List (MEL) and still be able to legally fly with inoperative equipment is if you are operating a nonturbine-powered small airplane (see figure 2). The King Air is definitely a turbine-powered airplane, so in order to fly with an item that is inoperative, you’re going to need to operate our aircraft with an MEL.

Figure 2: FAR 91.213 (partial)

“MEL” is short for Minimum Equipment List, but the name is a little misleading because an MEL comprises of many different items besides just a list. It makes more sense to refer to an MEL as a system used to obtain relief from the Federal Aviation Regulations which require that all installed equipment be operative for flight. An MEL will ultimately consist of a Letter of Authorization from the FAA allowing you to utilize an MEL, a list of equipment that may be inoperative, and other documents (Definitions, Preamble, Discrepancy Sheets and Placards) required for a complete MEL system.

For a Part 91 owner-operator, it’s quite common and expected to utilize a Master Minimum Equipment List (MMEL) as an MEL. The MMEL contains the items that may be inoperative yet still allow your aircraft to be considered airworthy. The MMEL is developed for a specific make and model of aircraft (i.e., B90, B200) and not for a specific aircraft. It lists the required procedures that must be followed to operate with the inoperative equipment. The bulk of the MEL is contained in this document.

Figure 3: An example of an MMEL that can be found by searching
Figure 4: In the MMEL, under section 33, inoperative cabin lights requires “Sufficient lighting is available for crew to perform required duties …”

MMELs can be found at by doing a simple search for “MMEL” (see figure 3). For many pieces of equipment listed in the MMEL, if the equipment is inoperative the item is deferred (or “MEL’d” in pilot speak) in a pretty straightforward manner. But, for others, there may be some “O” and/or “M” procedures that must be followed before the inoperative item is MEL’d. “O” is short for “Operator” and, in most cases, will be the pilot. The “O” symbol indicates a requirement for a specific operations procedure which must be accomplished in planning and/or operating with the listed item inoperative. An example would be cabin lights that may not be working. In the MMEL, under section 33, we see that inoperative cabin lights requires that “Sufficient lighting is available for crew to perform required duties…” (see figure 4). This would be left to the flight crew to decide if the lighting is adequate and there would need to be a procedure on how that determination is made. Similarly, there is the “M” symbol that indicates a requirement for a specific maintenance procedure which must be accomplished prior to operation with the listed item inoperative. An example of this would be an inoperative fuel flow indicator. Under section 73, in the MMEL, we find “May be inoperative provided both Fuel Quantity Indicating Systems are inoperative” (see figure 5). This procedure would involve maintenance personnel having to make this evaluation. In addition, there are sometimes inoperative items that involve both “O” and “M” procedures (see figure 6, opposite page).

Figure 5: An example from the MMEL with an “M” symbol that indicates a requirement for a specific maintenance procedure which must be accomplished prior to operation with the listed item inoperative.

The MMEL states that appropriate procedures for the “O” and “M” items are to be published as part of the operator’s MEL. Forewarning that this is the part of developing an MEL which requires the most legwork! While the MMEL tells us we may need to perform an “O” and/or “M” procedure, the MMEL doesn’t tell us how to do that. The how will be in our very own “O” and “M” procedures document that is part of the MEL system. These “O” and “M” procedures must be created by the operator. If you fly a relatively newer King Air, you may be in luck! At a recent King Air Gathering a Textron Aviation representative informed the attendees that “O” and “M” procedures exist that have already been created for newer King Airs (I’m sorry he wasn’t specific on years and/or serial numbers) that are yours for the taking. Just contact Textron with that request. For earlier King Airs, you’re on your own in having to create the “O” and “M” procedures. The operator procedures should be fairly straightforward for the pilot, but the maintenance items may require you to work closely with your maintenance technician/department in creating any of those procedures.

Figure 6: Some inoperative items involve both “O” and “M” procedures, and the MMEL states that appropriate procedures for the “O” and “M” items are to be published as part of the operator’s MEL.

Lastly, the MEL needs to contain a method of documenting any discrepancies that are deferred. The method doesn’t need to be too fancy, but it must be a written entry describing the inoperative item. Once all written documentation is complete, all “O” and “M” are complied with (if applicable), and the PIC has made a final safety of flight determination, a placard is placed on or near the inoperative item’s switch or other prominent location where the pilot may see that an item is being deferred. The placard can be something as simple as a sticker with a legible “INOP” written on it.

To summarize, a complete MEL will contain the following items (hopefully in a nice binder):

  • Letter of Authorization (LOA) from the FAA allowing you to operate with an MEL
  • Definitions (Policy Letter 25)
  • Preamble (Policy Letter 36)
  • Master Minimum Equipment List (MMEL)
  • Operator and Maintenance Procedures
  • Discrepancy Log Sheets
  • Placards

(Note: The Policy Letters and MMEL are free to download from

Back to the Original Question …

Returning to whether you can fly with your inoperative strobe light. An MEL Decision Making Tree is always helpful in guiding you through the process (see figure 7). Luckily for you, you do fly with an MEL! You consult your MMEL and see that the inoperative strobe light is allowed to be deferred, and it’s actually a simple one involving no “O” or “M” procedures. With a little magic of your pen, you’re able to “write up” the strobe light and decide that the lack of a strobe will present no safety of flight issues. With a placard in place next to the strobe light switch, you let your passengers know that you’ll be well on your way in no time!

Figure 7: MEL Decision Making Tree

In conclusion, remember that unless every installed item is working on your King Air, your aircraft is not considered airworthy. To get the ball rolling on operating with an MEL, you’ll need to contact your local FSDO and let them know your intent. The FAA inspector will then be able to let you know the next step in your request. It’s certainly my hope that this article takes out some of the mystery of MELs and gives you a head start on utilizing one. Having an MEL simplifies your operation in the long run and you’ll find that the MEL allows you the flexibility to fly with inoperative equipment while staying safe and legal.

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