Safety Publications/Articles

CFI to CFI: Can we go?

Minimum equipment lists

It was one of those moments during a checkride when one relies more on blind luck than pure knowledge. I had just started both engines of the Piper Seminole I was flying for my multiengine rating, and I was scanning the engine instruments: oil pressure in the green; fuel pressure in the green; vacuum pressure - left OK, right - I>not OK. The right vacuum pump was out. The examiner looked at me and said those infamous words, "Can we go?"

My mind went blank. This wasn't supposed to happen; mechanical failures don't happen on checkrides, they happen in briefing rooms with my instructor. But there I was, faced with a real mechanical failure and two possibilities: Either we're legal to fly or we aren't. I remembered that this aircraft operated with a minimum equipment list (MEL). I told the examiner that I would need to check the MEL before I could give a definite answer to his question. With his approving nod, I shut the aircraft down and proceeded to verify if we could continue the flight.

I ended up switching aircraft and passing the checkride. However, if my instructor hadn't explained operations with an MEL, the outcome would have been very different. Operations with inoperative equipment is a topic of utmost importance that doesn't always receive proper coverage during instruction. When a piece of equipment is found to be inoperable, there are two paths to determine if the aircraft is airworthy - using an approved MEL or FAR 91.213. Let's examine both options.

Operations with a MEL

An MEL is a list of equipment that must be installed and operable for the aircraft to be considered airworthy. It is aircraft-specific and spells out which pieces of equipment may be inoperable while maintaining airworthiness. If something is found to be inoperative, the pilot goes to the MEL, finds the entry for that item, and determines if the airplane must be grounded until that piece of equipment is fixed.

An MEL for a specific aircraft originates from a master minimum equipment list (MMEL). The MMEL is a list of all equipment on an aircraft type; it details which equipment is allowed to be inoperative without grounding the aircraft. (Think of a MMEL as a general, broader MEL.) The FAA has developed and has on file MMELs for most of the type-certificated aircraft in use today. The owner/operator who wishes to obtain an MEL for his or her specific aircraft will first contact the local flight standards district office and request a copy of the MMEL for that aircraft type. At that point it is the responsibility of the owner/operator to use the MMEL in conjunction with the airplane flight and maintenance manuals to create a specific procedures document for the aircraft.

The procedures document outlines the actual procedures to make the aircraft airworthy in the event of the failure of a specific piece of equipment. There are two categories of procedures: maintenance procedures (M) and operations procedures (O). An authorized mechanic must complete "M" procedures, but the pilot or flight crew can do "O" procedures. If an "O" procedure is required, it will be accompanied by a detailed action list for that particular piece of equipment.

Once the owner/operator has created the procedures document, it is presented to the FAA for approval. If granted, the FAA inspector will issue a letter of authorization (LOA). When this letter is received the MEL is complete and the aircraft may be operated within the guidelines of the MEL rather than the procedures outlined in the regulations. This formula will help you remember: MMEL + Procedures Document + LOA = MEL.

When a part of the aircraft is found to be inoperative the pilot will refer to the MEL. If the item is not in the procedures document, the aircraft is grounded. If the item is found, the pilot will take the appropriate actions required by the procedures document. Once the procedures are completed the aircraft is ready to fly.

An MEL is equivalent to a supplemental type certificate and is required to be on board the aircraft during flight. The MEL is only valid for a specific aircraft and cannot be transferred to another.

Operations under FAR 91.213

For those aircraft operating without an MEL, FAR 91.213 describes the process of determining the airworthiness of an aircraft with inoperative equipment. Use these four questions to verify whether or not your aircraft is legal to fly under 91.213.

  1. Is the affected equipment part of the VFR-day type certificate (91.213 [d][2][i])? If yes, the aircraft is grounded. If no, go to the next question.
  2. Is the affected equipment listed as required on the aircraft's equipment list or kinds of operation list (91.213 [d][2][ii])? If yes, the aircraft is grounded. If no, go to the next question.
  3. Is the affected equipment required by any other regulation, i.e. 91.205, 91.207, etc. (91.213 [d][2][iii])? If yes, the aircraft is grounded. If no, go to the next question.
  4. Is the affected equipment required to be operative by an airworthiness directive (91.213 [d][2][iv])? If yes, the aircraft is grounded. If no, go to the final step.

The final step is that the affected item must be removed from the aircraft or deactivated and placarded inoperative (91.213 [d][3][ii-iii]).

The go/no-go decision is one of the most fundamental decisions that a pilot will make, and an integral part of that decision is determining the airworthiness of the aircraft. Understanding how to make that determination is crucial to a student¿s development. No one needs to be sweating bullets next to an examiner who asks the simple question, "Can we go?"

David Wright is director of training for the AOPA Air Safety Foundation. A former pilot for US Airways Express, he is a CFI with more than 2,000 hours

By David Wright

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