FAR Ninety-One Point Two Thirteen, the Four-Step Inoperative Equipment Decision, and the Placard That Can Ground an Aircraft or Free One for Flight

FAR 91.213 governs how pilots legally operate an aircraft with inoperative equipment. The rule requires working through four specific questions in order - Minimum Equipment List, Kind of Operations Equipment List, FAR 91.205 required equipment, and applicable Airworthiness Directives - before making a go/no-go determination. Skipping this process in favor of instinct about how serious a broken item seems is how pilots end up on the wrong side of an airworthiness determination.

What Happens When You Find Something Broken on Preflight?

Consider this scenario: it is 6:50 a.m., you have a fuel stop 200 miles out, a passenger meeting you at the ramp in an hour, and a forecast that holds only through early afternoon. You complete your preflight, climb in, flip the master - and the right fuel gauge reads full while the left reads zero. You fueled both tanks the night before. You know that left tank is full.

Do you go?

The answer requires working through a defined decision process, not a judgment call about what you think you can manage.

What Are the Four Steps of the FAR 91.213 Decision?

FAR 91.213 requires four sequential questions before a pilot in command may legally operate an aircraft with inoperative equipment. Each question must be resolved before moving to the next.

Step 1: Does the Aircraft Have a Minimum Equipment List (MEL)?

An MEL is a document specific to the aircraft, developed by the operator and approved by the FAA. It specifies exactly which items are required and which can be deferred - and under what conditions. Some items may be deferred only for VFR operations, not IFR. Others carry dispatch conditions: a required placard, a maintenance action within a set number of days, or an operational restriction.

MELs are common in Part 121 airline operations and Part 135 air taxi work. Most small general aviation aircraft - Cessna 172s, Piper Cherokees, Beechcraft Bonanzas - do not have an FAA-approved MEL. If your aircraft does have one, the MEL is the controlling document.

Step 2: What Does the Kind of Operations Equipment List (KOEL) Say?

The KOEL lives in the aircraft’s Pilot’s Operating Handbook (POH) and Airplane Flight Manual (AFM). It is the manufacturer’s list of required equipment broken down by operating category: required for VFR day, VFR night, and IFR.

The KOEL is part of the aircraft’s type certificate data - not optional and not a recommendation. If the manufacturer specifies an item as required for the kind of flight you are planning, the aircraft is not airworthy for that flight. No placard changes that.

Step 3: Is the Item Required by FAR 91.205?

FAR 91.205 is the regulatory minimum equipment list for civil aircraft operating under Part 91. It specifies what is required for VFR day, VFR night, and IFR operations. These are regulatory minimums - not suggestions.

For VFR day operations, the mnemonic A-TOMATO-FLAMES is commonly used as a study tool:

• Airspeed indicator
• Tachometer for each engine
• Oil pressure gauge
• Manifold pressure gauge (altitude engines)
• Altimeter
• Temperature gauge (liquid-cooled engines)
• Oil temperature gauge
• Fuel gauge for each fuel tank
• Landing gear position indicator (retractable gear aircraft)
• Anti-collision lights
• Magnetic direction indicator
• Emergency locator transmitter (with specific exceptions)
• Safety belts

Mnemonics are a starting point. The actual regulatory text of 91.205 controls, and the list contains nuance. Know the mnemonic to get oriented; know the regulation to make the call.

For night operations, 91.205 adds position lights, a landing light if the aircraft is operated for compensation or hire, and an adequate source of electrical energy for all required lighting. Additional instrument requirements also apply.

If the inoperative item appears on the required equipment list for the kind of flight you are conducting, you cannot go. Your belief about whether you actually need it on that specific flight is not a factor in the regulatory determination.

Step 4: Is the Item Required by an Airworthiness Directive or Type Certificate Data Sheet?

Airworthiness Directives (ADs) are mandatory requirements issued by the FAA. An AD may require certain equipment to be installed and operational as a condition of flight. If an applicable AD covers the item in question, that directive controls.

The Type Certificate Data Sheet (TCDS) for the aircraft can also specify equipment required for the type certificate to remain in force. This is less common but it exists. If you are unsure whether an AD applies, your mechanic is the right resource - the FAA’s AD database is also publicly searchable.

What Does “Deactivated and Placarded Inoperative” Actually Mean?

If you work through all four questions and every answer is no, FAR 91.213 permits you to deactivate the equipment, placard it as inoperative, and fly.

Deactivating an inoperative item does not mean ignoring it. It means the item is confirmed non-functional and secured so it cannot interfere with other systems. An intermittent radio that cuts in and out can be more operationally problematic than one that is simply switched off and secured. The intent is that the item positively will not affect the safe operation of the aircraft.

The placard requirement is specific: it must be visible to the pilot and must read “INOPERATIVE.” A piece of masking tape, a laminated card, marker on paper - all satisfy the regulation as long as the placard is in the pilot’s view and uses that word.

One critical distinction: FAR 91.213 covers installed equipment that is not working - not equipment that has been removed. If an item has been physically removed from the aircraft, that is a maintenance action. It changes the aircraft’s approved configuration, requires a logbook entry, and requires a certificated mechanic to make an airworthiness determination. That is a different process entirely.

How Does the Fuel Gauge Scenario Resolve?

Back to the early morning preflight. Left fuel gauge reads zero; you know the tank is full.

There is no MEL on the aircraft. The POH’s KOEL does not list fuel quantity gauges as specifically required for VFR day operations. That clears steps one and two.

FAR 91.205 requires a fuel gauge for each fuel tank for VFR day operations. The decision stops at step three. The aircraft is not legally airworthy for that flight.

The fact that you personally filled both tanks the night before does not substitute for a functioning instrument. The purpose of a fuel gauge is ongoing awareness of fuel state during flight - not just at preflight. A broken gauge cannot tell you if a fuel cap is loose, a vent is clogged, or a tank is draining faster than expected. Cancel the flight. Get the gauge fixed.

When Does FAR 91.213 Work in Your Favor?

Same aircraft, different preflight finding: the panel clock is not working. Wrong time, does not illuminate, does not function.

No MEL. Not listed as required equipment in the POH. Not on the 91.205 required equipment list for VFR day. For IFR, 91.205 does require a clock displaying hours, minutes, and seconds - but for a VFR day flight, it does not apply. No applicable AD or TCDS requirement.

Placard it inoperative. Fly. The four-step process produced a legal, reasoned answer.

How Should You Answer an Inoperative Equipment Question on a Checkride Oral?

When an examiner presents an inoperative equipment scenario, the first move is not to immediately announce whether you go or stay. The first move is to describe the process.

Walk the examiner through it: start with the MEL if the aircraft has one; if not, check the KOEL in the POH; if the item is not listed as required there, check FAR 91.205 for the category of operations planned; and if it clears all of that, check for applicable ADs and the TCDS. Then arrive at the answer.

That response demonstrates an understanding of the regulatory framework, knowledge of where to find answers, and a reasoned determination - exactly what the Airman Certification Standards expects of a pilot in command.

What About Degraded GPS and Glass Cockpit Systems?

As glass cockpits become standard in training aircraft, a related question arises: what if the primary GPS navigator has entered a degraded mode - still providing position information but flagging a satellite integrity issue?

For a VFR day flight where the GPS is supplemental navigation and not on any required equipment list for that operation, FAR 91.213 may not apply at all because the device is still functioning, just degraded. The more relevant question becomes whether you are comfortable using it in that state for your intended operation.

For an IFR flight where that GPS is the navigation source for an approach, a satellite integrity flag changes the picture significantly. The Airplane Flight Manual (AFM) supplement for that navigator, the approach procedure requirements, and the specific integrity standard required for that approach all become relevant. A navigation database that is out of date, or a receiver flagging signal integrity, is not treated like a broken panel clock.

Knowing whether a system is on or off is not the same as knowing its operational limits. Both matter.

Should You Document a FAR 91.213 Deferral?

FAR 91.213 does not explicitly require a pilot logbook entry for a deferral on a privately operated aircraft. However, general airworthiness requirements do require that defects be addressed in a timely manner and that the aircraft be maintained in an airworthy condition.

Recording the discrepancy in the aircraft maintenance log establishes a record, protects you as the pilot in command, and ensures the next pilot who flies that aircraft knows exactly what they are dealing with. It takes two minutes and removes all ambiguity.

Key Takeaways

• FAR 91.213 is a four-step decision process - not a gut check. Work through MEL → KOEL → FAR 91.205 → ADs/TCDS, in that order, every time.
• If the item appears on FAR 91.205’s required equipment list for your category of operations, the aircraft is not airworthy for that flight. A placard does not change this.
• A legal deferral requires the item to be deactivated (not just broken and ignored) and placarded “INOPERATIVE” in view of the pilot.
• FAR 91.213 applies to installed inoperative equipment only - a removed item is a maintenance action requiring a mechanic’s airworthiness determination.
• On a checkride oral, demonstrate the process first. Arrive at your go/no-go answer only after walking the examiner through each step.