FAR Ninety-One Point Two Thirteen, the Four-Question Test Every Pilot Needs Before Departing With a Broken Instrument, and the Line Between Legal Flight and Smart Flight

Finding an inoperative instrument during preflight does not automatically ground your aircraft. FAR 91.213 establishes a structured four-question process for determining whether a flight is legal with a specific item inoperative. Understanding this process is required knowledge for the private pilot checkride and essential for every certificated pilot who will eventually face a squawk on a flying day.

What Is FAR 91.213 and When Does It Apply?

FAR 91.213 governs inoperative instruments and equipment. The FAA wrote this regulation acknowledging a practical reality: not every system failure grounds an aircraft. Maintenance is imperfect, parts fail between scheduled service, and some squawks have no bearing on the safety of a specific flight.

The regulation offers two pathways. The first applies to aircraft operating under a Minimum Equipment List (MEL) - an FAA-approved document specific to a particular aircraft’s registration number that specifies which items may be inoperative, under what conditions, and for how long before repair is required. Airlines and Part 135 charter operators commonly use MELs.

Most general aviation aircraft do not have an MEL. Without one, paragraph (d) of FAR 91.213 is your framework.

Does My Aircraft Have a Minimum Equipment List?

The rental Cessna 172 at a local flight school almost certainly does not have an MEL. Most Piper Cherokees, Beechcraft Bonanzas, and similar GA aircraft are in the same position. Without an MEL, FAR 91.213(d) governs the decision.

This distinction matters before you start the four-question process. If an MEL exists for your specific aircraft, it governs the analysis. If it doesn’t, paragraph (d) applies.

How Does the Four-Question Test Under FAR 91.213(d) Work?

Work through the four questions in order. A single “yes” answer means the aircraft cannot depart until the item is repaired, removed by a mechanic, or deactivated with proper documentation and a maintenance logbook entry. Only when all four questions return “no” is there a legal basis to continue.

The questions are:

1. Is the inoperative item required by FAR 91.205 for the type of operation planned?
2. Is the inoperative item required by an Airworthiness Directive?
3. Is the inoperative item listed in the aircraft’s Kinds of Operations Equipment List (KOEL)?
4. Does the aircraft’s POH or Approved Flight Manual specifically prohibit flight with the item inoperative?

Question 1: Is the Item Required by FAR 91.205?

FAR 91.205 lists the required instruments and equipment for day VFR, night VFR, and IFR flight. The day VFR list is commonly taught with the mnemonic ATOMATOFLAMES:

• A - Airspeed indicator
• T - Tachometer
• O - Oil pressure gauge
• M - Manifold pressure gauge (altitude engines)
• A - Altimeter
• T - Temperature gauge (air-cooled engines)
• O - Oil temperature gauge
• F - Fuel quantity gauges
• L - Landing gear position indicator (retractable gear)
• A - Anti-collision lights
• M - Magnetic compass
• E - Emergency locator transmitter (ELT)
• S - Safety belts for each occupant

Consider a scenario: an attitude indicator placarded inoperative on a day VFR cross-country. The attitude indicator does not appear on the day VFR required equipment list - it is required for IFR flight. For day VFR, question one returns no.

Flip the scenario: same inoperative attitude indicator, but the planned flight is IFR. Now the attitude indicator is required under FAR 91.205. Question one returns yes, and the aircraft does not fly IFR until it is repaired. Same item, completely different outcome based on the planned operation. This is exactly the kind of flip examiners use on checkrides.

Question 2: Is the Item Required by an Airworthiness Directive?

Airworthiness Directives (ADs) are legally binding maintenance requirements the FAA issues when a known unsafe condition is identified in a specific aircraft type, engine, or component. Some ADs specifically require that certain equipment be operational for the aircraft to remain airworthy.

Verify AD compliance by reviewing the aircraft’s maintenance records - a step that is especially important when renting or borrowing an unfamiliar aircraft. If an AD requires the broken item to be functioning, the answer is yes and the aircraft stays on the ground.

Question 3: Is the Item Listed in the KOEL?

The Kinds of Operations Equipment List (KOEL) is a table found in some aircraft Pilot Operating Handbooks that specifies which equipment is required for each category of operation: day VFR, night VFR, VFR over the top, and IFR.

Not every GA aircraft has a KOEL - many older POHs simply do not include one. If your aircraft’s handbook has a KOEL, check it. If the inoperative item is listed as required for your planned operation, the answer is yes.

Question 4: Does the POH Prohibit Flight With the Item Inoperative?

Some manufacturers included explicit prohibition language in the Limitations section of their handbooks. If the POH states clearly that the aircraft cannot be operated with a particular system inoperative, that is a binding limitation. The answer is yes and the aircraft does not fly.

What Has to Happen Before Departing With an Inoperative Item?

When all four questions return “no,” the aircraft is not automatically cleared to depart. Two specific requirements under FAR 91.213(d) must be satisfied:

1. The inoperative item must be removed from the aircraft or deactivated.
2. The item must be placarded as inoperative, with the placard visible to the pilot in flight.

The placard is the easy part to verify. But any physical change to the aircraft’s configuration - including deactivating a piece of equipment - requires a certificated mechanic, plus a logbook entry documenting what was done and confirming the aircraft is airworthy for the intended operation.

If you arrive at a rental aircraft and find an inoperative placard on the panel, ask to see the corresponding logbook entry. A placard without a proper maintenance release means the squawk was not handled under the process the regulation requires. That is a conversation to have with the FBO before accepting the aircraft.

What Do Common Inoperative Equipment Scenarios Look Like?

ELT battery expired. ELTs appear on the day VFR required equipment list. A functional ELT requires a serviceable battery. An expired battery effectively renders the ELT inoperative. Question one returns yes - the battery must be replaced before the aircraft flies.

Navigation lights inoperative. Position lights are not on the day VFR required equipment list, but they are required for night VFR. Daytime flight with inoperative nav lights: question one returns no. Work through the remaining three questions. If all return no and documentation is in order, there is a legal path to fly in daylight. Night flight with the same inoperative nav light: question one returns yes.

Turn coordinator or turn-and-slip indicator inoperative. Required for IFR, not for day VFR. Same framework, same analysis.

Transponder acting up. A transponder does not appear on the general day VFR required equipment list under FAR 91.205, so question one may return no. However, FAR 91.215 separately requires an operating transponder in Class B airspace, Class C airspace, certain surface areas, and above 10,000 feet MSL. If the route passes through any of that airspace, a working transponder is required regardless of what FAR 91.213(d) permits on the equipment question.

This is the deeper skill the checkride tests: understanding how regulations interact, not just applying one in isolation.

What If Something Breaks Away From Home Base?

You land at a fly-in 200 miles from home, and the next morning’s preflight reveals a problem - an oil temperature gauge that isn’t moving, a circuit breaker that won’t reset.

Even if the four-question process shows the item is not required for the return flight, a documented maintenance action is still required before departing. Many small airports have an A&P (airframe and powerplant) mechanic on call or reachable nearby. Make the call, get the sign-off, and get the logbook entry before flying.

If the item is required and no mechanic is available, FAR 21.197 provides an option: a special flight permit allowing an aircraft that is not currently airworthy to fly specifically to reach a maintenance facility. Apply through the Flight Standards District Office (FSDO) or, in some cases, through a designated airworthiness representative. It is not an everyday tool, but knowing it exists means a remote-field breakdown is not a dead end.

Is Legal the Same as Safe?

The four-question test defines the legal floor, not the ceiling. It sets the minimum threshold for a lawful flight - not whether that flight is actually a good idea.

If all four questions return “no” but something about the broken instrument is still bothering you - if you don’t understand why it failed, or if you suspect it signals a larger system problem - your judgment as pilot in command has the final vote. The regulation was designed as a practical tool for real-world maintenance situations, not as a rationalization mechanism for flying with unclear squawks.

Use the process honestly. Get the documentation completed properly. If the airworthiness picture isn’t clear, get a mechanic on the phone before making any decisions.

For the checkride, examiners present this as a scenario, not a knowledge question. They want to see the framework applied in order: check FAR 91.205, check for applicable ADs, check the KOEL, check the POH limitations. The Airman Certification Standards address this under the preflight preparation area. Know what is required, know where to look, and make the decision like a pilot in command.

Key Takeaways

• FAR 91.213(d) provides a four-question test for aircraft without an MEL to determine whether flight is legal with an inoperative item.
• A single “yes” to any of the four questions means the aircraft cannot depart until the item is repaired, removed, or properly deactivated with mechanic documentation.
• The same inoperative item can return “no” for day VFR and “yes” for IFR - the planned operation determines the entire analysis.
• Any deactivation or removal requires a certificated mechanic and a logbook entry; a placard alone does not satisfy the regulation.
• Multiple regulations can apply simultaneously - FAR 91.213(d) may permit flight while FAR 91.215 still requires a working transponder for the planned airspace.