FAR Ninety-One Point Two Thirteen, the Four Questions for Flying with Broken Equipment, and the Preflight Discovery That Trips Up Pilots at Every Level

When a broken instrument turns up during preflight, FAR 91.213 - “Inoperative Instruments and Equipment” - provides a structured, legal framework for deciding what happens next. The answer depends entirely on whether the item is required for the specific operation planned, and the regulation provides four questions to work through in sequence. Getting this wrong goes in both directions: grounding unnecessarily or flying when you shouldn’t.

What Is FAR 91.213 and Why Does It Exist?

FAR 91.213 lives in Title 14 of the Code of Federal Regulations, Part 91, Section 213. Its purpose is to give the pilot in command a legitimate decision-making process when something on the aircraft isn’t working.

The FAA knows aircraft break. Instruments fail, lightbulbs burn out, gauges stick. This regulation distinguishes between discrepancies that genuinely ground the aircraft and those that don’t - replacing guesswork with a methodical process grounded in regulatory logic.

What Equipment Is Required for VFR Day Flight?

Before working through what to do when something is broken, you need to know what’s actually required. FAR 91.205 covers required instruments and equipment for powered civil aircraft, organized by operation type: VFR day, VFR night, or IFR.

For VFR daytime flight, the standard mnemonic is ATOMATOFLAMES:

• A - Altimeter
• T - Tachometer (each engine)
• O - Oil pressure gauge
• M - Magnetic compass
• A - Airspeed indicator
• T - Temperature gauge (liquid-cooled engines only - does not apply to most training aircraft)
• O - Oil temperature gauge
• F - Fuel gauge (each tank in use)
• L - Landing gear position indicator (retractable gear aircraft only)
• A - Anti-collision lights (rotating beacon or strobe)
• M - Manifold pressure gauge (altitude engines only - typically does not apply to normally aspirated trainers)
• E - ELT, emergency locator transmitter (governed by FAR 91.207)
• S - Safety belts and shoulder harnesses

For a Cessna 172 on a standard VFR day flight, the practical required equipment list is: altimeter, tachometer, oil pressure gauge, magnetic compass, airspeed indicator, oil temperature gauge, fuel gauges, anti-collision light, ELT, and safety belts.

What Additional Equipment Is Required for VFR Night?

Night VFR adds another layer on top of the daytime list. The mnemonic FLAPS covers the additions:

• F - Fuses (a spare set, or circuit breakers if equipped)
• L - Landing light (only if flying for hire)
• A - Anti-collision lights (also required for day)
• P - Position lights (red, green, and white nav lights)
• S - Adequate source of electricity

The landing light requirement surprises many students. The landing light is only required at night if flying for hire. A student or private pilot on a personal night flight has no legal obligation to carry a working landing light. Flying without one isn’t advisable on practical safety grounds - but the regulation says what it says.

What Are the Four Questions for Flying with Broken Equipment?

For aircraft without a Minimum Equipment List - which covers most training aircraft and light general aviation planes - the process is found in paragraph D of FAR 91.213. When an inoperative item turns up, work through these four questions in order. A “yes” at any step means the aircraft needs maintenance before flight.

Question 1: Is the equipment required by the aircraft’s type certificate data sheet?

The type certificate data sheet is the FAA document certifying what the aircraft must have as part of its original approved design. If an item is listed there as required, it cannot be placarded around - it needs to be fixed.

Question 2: Is the equipment required by an applicable airworthiness directive?

Airworthiness directives are mandatory compliance documents. If an AD requires a piece of equipment to be functional, the inoperative equipment rule provides no path around it. These are not optional.

Question 3: Is the equipment required by FAR 91.205, or any other applicable FAR, for the kind of flight operation planned?

This is where ATOMATOFLAMES pays off. Cross-reference the broken item against the required equipment list for the specific flight being planned. The answer may differ between VFR day, VFR night, and IFR operations.

Question 4: Is the equipment required by the POH, or identified on a placard or marking, as necessary for the planned operation?

Some aircraft have POH notes or panel placards specifying that certain equipment must be operative for certain flight types. If the broken item falls into that category, it needs attention before departure.

If all four answers are “no”: the item may be deactivated, placarded with the word “inoperative,” and the flight may proceed - provided a certificated pilot or mechanic determines the item does not constitute a safety of flight hazard for the proposed operation. Deactivation may be as simple as pulling a circuit breaker, or it may require a certificated mechanic, depending on the item and aircraft.

How Do These Rules Apply in Real Preflight Scenarios?

Scenario 1: VSI stuck during VFR day preflight

The vertical speed indicator is not on the ATOMATOFLAMES list. It is generally not required by the type certificate data sheet or an applicable AD on standard trainers, and the POH typically does not list it as required for VFR operations. All four questions come back “no.” Placard it inoperative, confirm it’s not a safety hazard, and the flight is legal.

Scenario 2: Expired ELT battery

This one is not a standard inoperative equipment scenario - it’s a maintenance compliance issue. FAR 91.207 requires the ELT battery to be replaced when it has been used for more than one cumulative hour, or when 50% of its useful life has expired (as indicated on the battery itself), whichever comes first. The inoperative equipment rule doesn’t provide a clean path around this. The battery needs to be addressed before flight.

Scenario 3: Panel clock stopped working

A clock is not on the required equipment list for VFR day flight. In most general aviation trainers, it is not required by the type certificate data sheet or POH for VFR operations. Placard it inoperative and fly. For IFR operations, precision timing carries more significance - particularly for certain approaches - and warrants a closer look.

Scenario 4: Nav light burned out

Position lights are on the night list, not the daytime list. A burned-out nav light does not ground the aircraft for a daytime VFR flight. It must be logged as a discrepancy and fixed before any operation where position lights are required.

What Does the Safety of Flight Hazard Determination Actually Mean?

The hazard determination is the step most likely to be treated as a formality. It isn’t. Even after all four questions come back “no,” a certificated pilot or mechanic must make a genuine determination that the inoperative item doesn’t constitute a hazard for the specific proposed operation.

A stuck VSI on a clear VFR day in uncontrolled airspace is probably not a hazard. The altimeter is there, the horizon is visible, and vertical awareness can be managed the way pilots managed it before the VSI existed. That same stuck VSI on an instrument training flight in actual IMC is a different calculation. The item may technically clear the four-question framework, but the hazard determination should prompt a harder look.

Pilot in command authority means the right to make a conservative call always exists. The regulation establishes a floor for legal operations. It places no ceiling on caution.

What About Aircraft with a Minimum Equipment List?

Aircraft operating under an FAA-approved Minimum Equipment List (MEL) follow a different path. An MEL is an operator-specific, FAA-approved document that identifies which items can be inoperative under defined conditions - often with specified alternative procedures or operational limitations. Airlines and many corporate flight departments operate under MELs.

If the aircraft has an approved MEL, that document governs instead of the paragraph D framework. For most pilots flying training aircraft or personally owned light planes, paragraph D is the applicable process.

How Should This Topic Be Approached on a Checkride Oral?

The inoperative equipment regulation is fair game for the private pilot oral exam. An examiner can hand you a preflight scenario - something isn’t working - and ask what you do. The examiner wants the process, not just a conclusion.

Walk through each question out loud: Is it required by the type certificate data sheet? Is there an applicable airworthiness directive? Is it required by FAR 91.205 for this operation? Is it required by the POH or a placard? Then address deactivation, placarding, and the hazard determination. The answer isn’t “I won’t fly” or “I’ll fly anyway” - it’s structured, regulatory thinking applied to a specific scenario.

The inoperative equipment rule is not a loophole. It’s a deliberate framework the FAA built to acknowledge that real-world aviation involves imperfect airplanes and that grounding for every minor discrepancy would be neither practical nor universally safer. Use it honestly and methodically.

Key Takeaways

• FAR 91.213 gives pilots a legal, structured framework for making inoperative equipment decisions - not a workaround, but a tool designed for real-world operations.
• Whether a broken item grounds the aircraft depends on whether it was required in the first place - under the type certificate, an applicable AD, FAR 91.205, or the POH.
• The four-question decision tree must be worked in sequence; a “yes” at any step means maintenance is required before flight.
• The safety of flight hazard determination is a substantive evaluation - the same broken item may be acceptable on a clear VFR day and unacceptable in IMC.
• ELT battery expiration is a maintenance compliance issue under FAR 91.207, not a standard inoperative equipment scenario, and generally cannot be resolved by placarding alone.