FAR Ninety-One Point Two Thirteen, the Four-Question Test That Determines Whether a Broken Airplane Is Still a Legal Airplane, and the Judgment Call That Lives Beyond the Regulation

When you find something broken during preflight, FAR 91.213 gives you a structured, four-question test to determine whether the flight is legal without it. This framework applies to aircraft without a Minimum Equipment List - the category that covers most small general aviation aircraft. Each question is a gate: fail any one of them and the airplane stays on the ground until the item is repaired.

Does Your Airplane Have an MEL?

FAR 91.213 begins by splitting all aircraft into two categories. The first category covers aircraft with a Minimum Equipment List (MEL) - an FAA-approved document, specific to a particular make, model, and registration number, that defines exactly which items can be inoperative, under what conditions, and for how long. Airlines and corporate operators typically have them.

The second category is aircraft without an MEL. This is where the regulation’s four-part test applies, and it’s the category most general aviation pilots operate in. The flight school Cessna 172 almost certainly does not have an MEL.

What Is the Four-Question Test Under FAR 91.213?

For aircraft without an MEL, FAR 91.213(d) gives the pilot in command a decision framework. If the inoperative equipment passes all four questions, flight is legal - with conditions. If it fails any single question, the airplane is grounded until the item is fixed.

The four questions are:

1. Is the equipment required by FAR 91.205?
2. Is the equipment required by the Type Certificate Data Sheet or any Airworthiness Directive?
3. Is the equipment required for the specific operation being conducted?
4. Does the inoperative equipment create a safety hazard?

Question 1: Is It Required by FAR 91.205?

FAR 91.205 lists the instruments and equipment that must be operational before a legal departure. The list changes depending on the type of operation.

For day VFR, the required equipment is taught through the mnemonic A TOMATO FLAMES:

• A - Airspeed indicator
• T - Tachometer (one per engine)
• O - Oil pressure gauge (each engine using a pressure system)
• M - Manifold pressure gauge (each altitude engine)
• A - Altimeter
• T - Temperature gauge (each liquid-cooled engine)
• O - Oil temperature gauge (each air-cooled engine)
• F - Fuel gauge (each fuel tank)
• L - Landing gear position indicator (retractable gear aircraft only)
• A - Anti-collision lights
• M - Magnetic compass
• E - Emergency Locator Transmitter
• S - Safety belts for each occupant

If the broken item appears anywhere on that list and a day VFR flight is planned, the analysis ends at question one. No further questions needed - the airplane doesn’t go.

Night VFR adds to A TOMATO FLAMES: approved position lights, an adequate source of electrical energy for all installed electrical and radio equipment, and one spare set of fuses or three spare fuses of each kind required. Flying for hire at night also requires an approved landing light.

Question 2: Is It Required by the TCDS or an Airworthiness Directive?

The Type Certificate Data Sheet (TCDS) is the FAA document that defines what an aircraft was originally certified to include. Airworthiness Directives (ADs) are mandatory inspections or modifications issued when a known safety issue exists. Both carry legal weight and can require equipment beyond what 91.205 lists.

For most items on a typical training aircraft, question two passes quickly. But the question is worth asking, because some manufacturers include requirements in their certification that go beyond the general regulation.

Question 3: Is It Required for the Specific Operation Being Planned?

This is where the analysis gets route- and operation-specific. Some equipment isn’t required for day VFR but becomes required the moment the flight enters certain airspace or conditions.

A transponder isn’t in A TOMATO FLAMES. But FAR 91.215 requires one for Class B airspace, Class C airspace, or above 10,000 feet MSL in Class E. A broken transponder passes question one, but fails question three the moment the planned route touches any of that airspace.

GPS is not required for VFR flight. But on an IFR flight where GPS is the planned navigation source for approaches, a broken GPS navigator changes what approaches remain legal. Whether it fails question three depends entirely on the specific route and what navigation equipment is still functional.

Question three requires knowing the airspace, the route, and the operation before stepping to the ramp.

Question 4: Does the Inoperative Equipment Create a Safety Hazard?

This question is different from the first three. It requires judgment, not just knowledge. The regulation does not define “hazard” - that determination belongs to the pilot in command.

A dead cockpit clock on a local day VFR flight, with a functioning watch on the wrist, is probably not a hazard. A fuel gauge stuck on full when the last departure logged that a tank is running low is a hazard regardless of what the first three questions said - even if the gauge were somehow absent from every required list.

Question four is the safety valve in the system. It’s where the regulation explicitly hands authority and responsibility back to the pilot.

What Happens When Equipment Passes All Four Questions?

FAR 91.213(d) permits flight with inoperative equipment if three conditions are met.

First, the equipment must be removed from the aircraft or deactivated. For a dead clock, the item is already non-functional. For other equipment, deactivation may mean pulling a circuit breaker or physically disconnecting the unit.

Second, the cockpit instrument or control must be placarded “INOPERATIVE” in a location visible to the crew. This placard is not a formality - it is a legal requirement. Flying with inoperative equipment under this provision without a placard is not protected.

Third - and frequently skipped - the inoperative item must be entered in the aircraft’s maintenance log. The pilot in command can make this entry without a mechanic. It must state what is inoperative, reference FAR 91.213, and document when the determination was made. The next pilot who flies the airplane needs to know that a placard was reviewed against the regulation, not just that something is broken.

How Does the Four-Question Test Apply to Real Scenarios?

Attitude indicator. For day VFR, the attitude indicator does not appear on the required list. Questions one through three may pass. But question four demands honest self-assessment: a student pilot who has never trained for partial-panel flight, flying with no functioning attitude reference, faces a genuine hazard. An instrument-rated pilot flying a local pattern on a clear morning with a solid outside horizon faces a different risk profile. The regulation does not make that call - the pilot does.

Inoperative pitot heat. Pitot heat is not in A TOMATO FLAMES. It may pass questions one, two, and three on a standard VFR flight. But if icing conditions are possible, flying without pitot heat makes question four a hard no. The absence of a specific regulatory requirement does not override a sound judgment that the flight is unsafe.

Broken position light. For a day-only flight, position lights are not on the A TOMATO FLAMES list and the test passes easily - placard it and go. But the same broken light fails question three the moment a night flight becomes possible. Same inoperative item, different answer, entirely dependent on when the flight lands.

Alternator warning annunciator. If that light is the only indication that the electrical system is failing, flying single-engine IFR, at night, or far from the departure airport introduces a scenario where an alternator failure could drain the battery before the problem is even detected. Question four may stop the flight where questions one through three did not.

How Does FAR 91.213 Appear on a Checkride?

The Airman Certification Standards include knowledge of required instruments and equipment under Area of Operation One, Preflight Preparation. Examiners routinely present a preflight scenario in the oral: something is broken - what do you do?

The examiner is looking for two things: knowledge of what FAR 91.205 requires (A TOMATO FLAMES and the night VFR additions), and the ability to walk through the decision framework for equipment that isn’t on the required list.

A strong answer sounds like this: “Is it required by 91.205? No. Is it required by the TCDS or any AD? No. Is it required for the specific operation I’m planning? No. Does it create a safety hazard? No. Then I placard it inoperative, make a maintenance record entry, and the flight is legal.”

That walk-through - not just a conclusion - is what the examiner wants to hear.

What Are the Options If the Equipment Fails the Test?

If the inoperative item fails any of the four questions, the options are repair or a ferry permit. FAR 91.61 governs ferry permits, which allow an aircraft to be flown to a maintenance facility under specific conditions when repair isn’t available on-site. Ferry permits are issued for specific flights with specific conditions - they are not a general workaround and are not issued quickly.

Key Takeaways

• FAR 91.213 provides a four-question test for determining whether an aircraft without an MEL can legally fly with inoperative equipment.
• Know A TOMATO FLAMES well enough to run through question one mentally in under 30 seconds. For night VFR, know the additions too.
• Question three is route-specific - a broken transponder may pass question one but fail question three if the route crosses Class B or Class C airspace, or goes above 10,000 feet MSL.
• Question four requires judgment. The four-part test tells you what is legal; it does not tell you what is wise. Those are different questions.
• If equipment passes all four questions, three steps are required: deactivate or remove the item, placard it “INOPERATIVE” in view of the crew, and make a maintenance log entry - which the pilot in command can write.