FAR Ninety-One Point Two Zero Five, the Required Equipment List, and the Mnemonic Every Student Memorizes But Never Actually Learns to Use

FAR 91.205 organizes required aircraft instruments and equipment into three tiers: day VFR, night VFR, and instrument flight rules. Each tier builds on the previous one. The regulation shows up on nearly every private pilot oral exam, but its real value is on the ramp on a Tuesday morning when something on the panel isn’t working and you need to decide whether the flight is legal.

What Are the Three Tiers of FAR 91.205?

The structure of 91.205 is straightforward once you see it as a layered system. Day VFR is the foundation. Night VFR adds to it. IFR adds to that. Mnemonics like A TOMATO FLAMES, FLAPS, and GRABCARD can scaffold the memorization, but they don’t survive contact with an actual inoperative-equipment scenario. The regulation does.

What Equipment Is Required for Day VFR Flight?

Paragraph (b) of 91.205 sets the day VFR baseline. Every item has a specific reason for being there.

Airspeed indicator. Required to know how fast the aircraft is moving through the air.

Altimeter. Required to know altitude above sea level.

Magnetic direction indicator. This is the compass. The regulation uses the term “magnetic direction indicator” - it does not require a gyroscopically-driven heading indicator, only a device that points north.

Tachometer for each engine. Displays engine RPM for power setting and confirming the engine is running within limits. Pilots transitioning to constant-speed propeller aircraft sometimes overlook this one because it feels redundant, but the requirement still applies.

Oil pressure gauge for each engine using a pressure system. Nearly every reciprocating engine in general aviation uses a pressure-based oil system, making this effectively universal. A failed oil pressure gauge is an emergency in progress.

Temperature gauge for each liquid-cooled engine. Lycoming and Continental engines - the powerplants in most trainers - are air-cooled, so this specific item does not apply to them. It becomes relevant if you ever fly a liquid-cooled aircraft.

Oil temperature gauge for each air-cooled engine. This one does apply to the standard trainer. Oil temperature climbs on hot days after long ground runs, and monitoring it matters.

Manifold pressure gauge for each altitude engine. An altitude engine is a supercharged or turbocharged engine. Normally aspirated engines don’t require this gauge because power isn’t set by manifold pressure on those aircraft.

Fuel gauge for each tank in use. Note the precise language: in use. Not every tank on the aircraft - only each tank being drawn from. The regulation requires the gauge to indicate quantity and permits it to read empty when the tank actually is empty. That is the complete standard.

Landing gear position indicator, if the aircraft has retractable landing gear. Not required on fixed-gear aircraft. On a Mooney or Beechcraft Bonanza, an inoperative gear position indicator grounds the aircraft.

Anti-collision light system. For aircraft certified after March 11, 1996, an approved anti-collision light system is required for all flight operations, including daytime. For aircraft certified before that date, the daytime requirement is less clear-cut, but an installed system must be functional - it cannot simply be switched off and treated as optional.

Safety belts and shoulder harnesses where required. Required for each occupant. Shoulder harness requirements vary by aircraft type and seat position, but every person on board must have restraints.

The mnemonic A TOMATO FLAMES is widely taught. Different instructors use slightly different versions, and the letters don’t map perfectly to every item. Verify that whatever version you’re studying actually reflects the current regulation.

What Additional Equipment Is Required for Night VFR?

Paragraph (c) requires everything from the day VFR list, plus five additions. The mnemonic FLAPS covers the structure: fuses, landing light (if for hire), anti-collision lights, position lights, source of electrical power.

Position lights. The red, green, and white navigation lights. Red on the left wing, green on the right, white at the tail.

Approved anti-collision light system. At night, this requirement applies to any aircraft regardless of certification date.

One electric landing light, if the aircraft is operated for hire at night. The for-hire qualifier is important. A student pilot on a solo night cross-country does not require a functioning landing light. A flight school billing a customer for that same flight does.

An adequate source of electrical energy for all installed equipment. Night operations draw on the electrical system continuously - navigation lights, radios, transponder, GPS. The system must sustain all of it.

One spare set of fuses, or three spare fuses of each kind required, accessible to the pilot in flight. This one surprises students every time. Spare fuses, reachable from the cockpit, are a legal requirement for night flight.

What Equipment Is Required for IFR Flight?

Paragraph (d) adds to the day VFR list again. The mnemonic GRABCARD covers the additions: generator, radios, altimeter (sensitive), ball, clock, attitude indicator, rate of turn, directional gyro.

Two-way radio communication system. Separate from navigation equipment. You must be able to communicate with ATC.

Navigation equipment appropriate to the ground facilities being used. The regulation ties the requirement to the approach or facility planned. A VOR approach requires a working VOR. A GPS approach requires an IFR-approved GPS. You cannot legally plan an approach that requires equipment you don’t have functioning.

Gyroscopic rate-of-turn indicator. The turn coordinator. Indicates the rate at which the aircraft is turning and is critical when flying in instrument meteorological conditions.

Slip and skid indicator. The ball. Some turn coordinators include one; some do not. Either way, it is required for IFR.

Sensitive altimeter adjustable for barometric pressure. Must have a Kollsman window for setting the current altimeter setting as pressure changes across regions.

A clock displaying hours, minutes, and seconds, with a sweep second hand or digital equivalent. Timing drives holding patterns, approach timing, and missed approach procedures. The clock must be readable to the second.

Gyroscopic pitch and bank indicator. The attitude indicator.

Gyroscopic direction indicator. The heading indicator.

What Happens When an Instrument Is Inoperative?

This question is answered by a separate regulation: 91.213, Inoperative Instruments and Equipment. Most pilots have a working understanding that goes something like “placard it inoperative and go fly.” That is partially right - and partially a path to a violation if applied incorrectly.

The actual decision process moves through four checks.

Check 1: Does the aircraft have an approved Minimum Equipment List (MEL)? If yes, follow it. An approved MEL tells you exactly which items can be inoperative and under what conditions. Most light general aviation aircraft do not have one.

Check 2: Is the item required by an Airworthiness Directive? If an AD mandates the equipment be working, the flight does not happen. Full stop.

Check 3: Is it required by the Type Certificate Data Sheet or the aircraft’s Pilot’s Operating Handbook? If the manufacturer requires it for airworthiness, you don’t fly.

Check 4: Is it required by 91.205 for the type of operation you’re planning? This is where the equipment list applies directly. If the item appears on the required list for your planned flight conditions, it must be working.

If all four checks come back no, paragraph (d) of 91.213 permits you to placard the item inoperative, log the discrepancy, and depart. Any item that could affect airworthiness must be removed or deactivated, and it must be clearly placarded so the next pilot knows the status.

How Does This Play Out in Practice?

Scenario one. You arrive for a day VFR local flight. During preflight, the outside air temperature gauge is dead. No MEL on the aircraft. The POH doesn’t list OAT as required equipment. Paragraph (b) of 91.205 doesn’t include OAT on the day VFR list. All four checks come back no. Placard it, log it, go fly. Legally.

Scenario two. Same morning, but the turn coordinator is inoperative. No MEL. Not required by the Type Certificate Data Sheet. Check paragraph (b) of 91.205: the turn coordinator does not appear on the day VFR list. It appears in paragraph (d) under IFR requirements. For a day VFR flight, all four checks come back no. The regulation permits you to depart.

Whether you should is a different question entirely. If weather is marginal and instrument meteorological conditions are anywhere in the picture, an inoperative turn coordinator is a serious risk factor. The regulations establish the legal floor. Pilot judgment sets the actual floor.

Why Each Item Is on the List

Every instrument on these lists exists because someone needed it and didn’t have it. Fuel gauges are required because aircraft ran dry. The slip and skid indicator is required because spatial disorientation in the clouds has killed pilots. The clock is required because approach procedures depend on precise timing. When you understand the engineering rationale behind each requirement, you stop treating this as a memorization exercise. You start treating it as a set of protections built from experience.

That shift changes how you answer the examiner’s question. Instead of reciting, you’re reasoning. That is what the Airman Certification Standards are actually measuring.

Key Takeaways

• 91.205 has three tiers: day VFR (paragraph b), night VFR (paragraph c), and IFR (paragraph d). Each adds to the previous.
• The fuel gauge standard only requires accuracy down to empty - a gauge that reads zero when the tank is actually empty is legally compliant.
• Anti-collision lights are required for all operations (including daytime) on aircraft certified after March 11, 1996.
• Inoperative equipment decisions follow a four-check process under 91.213, not a simple “placard and go” rule.
• The regulation sets the legal floor. Pilot judgment - especially in marginal conditions - sets the real one.