Federal Aviation Regulation Ninety-One Point Two One Three, the Inoperative Equipment Decision, and the Decision Tree Every Pilot Needs When Preflight Finds Something Broken

The discovery of a broken instrument or failed system during preflight doesn’t automatically ground an aircraft - but it doesn’t automatically clear one either. FAR 91.213 provides a structured decision framework that determines whether an aircraft with inoperative equipment is airworthy and what steps must be taken before flight. Working through this framework in order is a regulatory requirement and a core pilot skill.

What Is FAR 91.213 and How Does It Work?

Federal Aviation Regulation 91.213 governs inoperative instruments and equipment in aircraft operating under Part 91. The regulation establishes that inoperative equipment doesn’t automatically render an aircraft unairworthy - but it requires pilots to work through a specific sequence of questions before making that determination.

The framework functions as a decision tree. Each question either stops the process with a no-fly answer, or passes the determination to the next question.

Step 1: Is the Inoperative Item Required by an Airworthiness Directive?

Airworthiness Directives (ADs) are mandatory orders issued by the FAA when an unsafe condition is identified on a specific aircraft type. If an applicable AD requires a piece of equipment to be operational on your specific aircraft and that equipment is broken, the aircraft is not airworthy. The flight does not happen. Call maintenance.

Check the aircraft’s AD compliance log before drawing any conclusions. Most flight school rental aircraft have AD compliance maintained by the school’s maintenance department, but knowing where to find that log and how to read it is part of understanding your airplane’s airworthiness status. If no applicable AD covers the broken item, move to the next question.

Step 2: Is the Item Required by the Kinds of Operations Equipment List (KOEL)?

The Kinds of Operations Equipment List - universally shortened to KOEL, pronounced like the name Joel with a K - lives in your Pilot Operating Handbook (POH), typically in Section 2 or Section 7 depending on the aircraft. It lists installed equipment and specifies whether each item is required for particular categories of operation: Day VFR, Night VFR, IFR, and so on.

The point students most often miss: the KOEL doesn’t declare an item required for all flying. It specifies whether the item is required for the specific kind of operation you’re about to conduct. Position lights may be required for night VFR on most general aviation aircraft, but that same KOEL may not list them as required for day VFR - meaning a burned-out position light that grounds a night cross-country may not affect a daytime flight completed well before sunset.

The KOEL in your POH is a manufacturer document. The FAA’s own required equipment list lives in FAR 91.205, which most pilots memorize via the ATOMATOFLAMES mnemonic for day VFR, with additional items required for night operations and IFR flight. Both sources must be cross-referenced. If the inoperative item is required by either the regulatory minimums or the manufacturer’s KOEL for the operation you’re planning, the flight is grounded until repairs are complete.

Step 3: Does the Aircraft Have an Approved Minimum Equipment List (MEL)?

A Minimum Equipment List (MEL) is an FAA-approved document that specifies which items of equipment may be inoperative, under what conditions, and sometimes with what crew procedures or operational restrictions attached. MELs are most common in Part 135 and Part 121 commercial operations, but some Part 91 operators have them as well.

If your aircraft has an approved MEL, that document governs the determination - and it supersedes the baseline Part 91 rules. Use it, follow it completely, and meet any documentation requirements it specifies. If no MEL exists, continue to the next question.

Step 4: Is the Item Required by the Aircraft’s Type Certificate Data Sheet?

Every certificated aircraft has a Type Certificate Data Sheet (TCDS) defining the approved configuration of that airframe. Equipment required by the type certificate to be installed and operational is relevant to the airworthiness determination. This layer of the analysis is more technical than the others; consult a qualified Airframe and Powerplant (A&P) mechanic when there’s any uncertainty about whether a specific item is type-certificate-required for your aircraft.

Step 5: Can the Item Be Properly Deactivated and Placarded?

If the inoperative item clears all four prior questions, FAR 91.213 permits continued operation provided the equipment is:

• Properly deactivated, and
• Marked with a placard in clear view of the pilot stating the item is inoperative, or
• Physically removed from the aircraft

The placard is not a formality. It tells every subsequent pilot who climbs into that cockpit not to rely on that instrument or system. A broken fuel quantity gauge with no placard can contribute to a fuel management error in a high-workload moment in flight.

Who can perform the deactivation? If pulling a circuit breaker that the aircraft maintenance manual authorizes the pilot to pull is all that’s required, the pilot may handle it. If deactivation requires opening panels, removing components, or any maintenance action, a certified A&P mechanic must perform and log the work. Pilots and renters who decide informally that something isn’t required and fly anyway - without proper deactivation and placarding - are not legal, and they’ve defeated the safety purpose the regulation was designed to serve.

How Does the FAR 91.213 Decision Tree Apply to Real Preflight Scenarios?

VSI stuck during preflight. The vertical speed indicator is pegged at -200 feet per minute with the engine off. Work the questions: applicable AD? Check the log. Required by the KOEL for day VFR? On most Cessna 172s, no. Required by FAR 91.205 for day VFR? No - the VSI is not on the required instrument list for day VFR operations. The decision tree clears. An A&P deactivates and placards the instrument, and the flight proceeds without relying on it.

Altimeter reading significantly off. The altimeter is set to the current ATIS setting but reads well outside the known field elevation - more than the normal few feet of variation. The altimeter is required for both day and night VFR under FAR 91.205. An inoperative or significantly inaccurate altimeter makes the aircraft unairworthy for VFR flight. Notify maintenance. Do not fly.

Landing light burned out, morning departure. Landing lights are not required for day VFR operations under FAR 91.205. Confirm the same in your specific aircraft’s KOEL. If the item clears, with proper deactivation and placarding, the daytime flight may be legal. But consider the judgment call: a morning departure is a decision that shapes your options for the entire flight. If weather delays your return and you’re arriving at dusk, you’ve already committed to flying without that light. Legal and operationally wise are not always the same thing.

Transponder failure discovered away from home base. A Mode C transponder is required when operating in Class B airspace and its associated shelves. If your planned route transits that airspace and the transponder has failed, you cannot proceed on the filed routing. Options include contacting approach control to request handling as a non-transponder aircraft, routing around or under the airspace, or obtaining a Special Flight Permit from the nearest FAA Flight Standards District Office (FSDO) to ferry the aircraft to a maintenance facility. Special flight permits exist for exactly this situation - they are not routine, but knowing they’re available keeps a stuck-at-an-airport situation from becoming a crisis.

What Documentation Is Required After Flying with an Inoperative Item?

If a flight proceeds with an inoperative item, the item’s status must be recorded in the aircraft maintenance records - a logbook entry by an authorized person. For renters and student pilots, the flight school typically manages this. Confirming that it has been done is part of acting as a responsible pilot in command.

When Should Uncertainty Ground a Flight Entirely?

If the right section of the POH can’t be located. If the AD compliance log doesn’t give a clear answer for your specific aircraft serial number. If there’s genuine uncertainty about whether the broken item falls under a required equipment category. The aircraft is grounded until there is a clear, documented answer. “I think it’s probably fine” is not a regulatory determination.

On an oral exam, an examiner who describes a broken instrument and asks how you’d handle it is looking for the logic, not the regulation citation. Walk through each question in order: AD? KOEL and FAR 91.205 for this specific operation? MEL? Type certificate? If it clears, what’s the deactivation path, who performs it, and what gets documented? That’s the answer examiners are looking for - and the same thinking that makes a sound decision on the ramp.

FAR 91.213 is a decision framework, not a loophole. Used honestly - consulting the right documents, bringing in maintenance when maintenance is needed, making a conservative call when genuinely uncertain - it’s one of the most useful regulations in Part 91. It replaces ramp-side guesswork with structure and authority.

Key Takeaways

• FAR 91.213 provides a five-question decision framework; each question must be answered in order before the next applies
• Cross-reference both FAR 91.205 (regulatory minimums) and the aircraft’s KOEL (in the POH) - if the broken item is required by either source for the planned operation, the flight is grounded
• An item that clears the decision tree must still be properly deactivated and placarded - informally ignoring a broken instrument is not legal
• Any deactivation requiring maintenance work must be performed and logged by a certified A&P mechanic; pilots may only take actions explicitly authorized by the maintenance manual
• Uncertainty is not an acceptable operational status - if there’s no clear answer in the documents, the flight waits until there is one