2.1 14 CFR 91.205 Required IFR Instruments & Equipment

14 CFR 91.205 Required IFR Instruments & Equipment

Operating an aircraft under Instrument Flight Rules (IFR) demands a higher level of instrument redundancy, navigational capability, and electrical reliability than visual flying. Because an instrument pilot cannot rely on external visual horizons or ground references for spatial orientation, federal aviation regulations establish strict baseline equipment mandates to ensure the safety of flight in Instrument Meteorological Conditions (IMC).

Under 14 CFR § 91.205, equipment requirements are structured in a cumulative, layered hierarchy: IFR operations require compliance with standard VFR Day equipment, plus VFR Night equipment (if operating at night), plus specialized IFR instruments and equipment, and high-altitude requirements when operating at or above Flight Level 240.

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1. The Regulatory Equipment Hierarchy

Federal regulations treat airworthiness as a cumulative pyramid. You cannot operate under IFR without first satisfying the foundational airworthiness baselines for visual flight.

+-----------------------------------------------------------------------------+
|                   14 CFR 91.205 EQUIPMENT HIERARCHY                         |
|                                                                             |
|   [FL240+ OPERATIONS]     ---> 14 CFR 91.205(e): DME / Suitable RNAV        |
|                                          +                                  |
|   [IFR DAY & NIGHT]       ---> 14 CFR 91.205(d): GRABCARD                   |
|                                          +                                  |
|   [VFR NIGHT (If at night)]---> 14 CFR 91.205(c): FLAPS                     |
|                                          +                                  |
|   [VFR DAY BASELINE]      ---> 14 CFR 91.205(b): ATOMATO FLAMES             |
+-----------------------------------------------------------------------------+

• VFR Day (91.205(b)): Mandatory for all civil aircraft operations.
• VFR Night (91.205(c)): Mandatory if operating at night (between evening civil twilight and morning civil twilight, or sunset to sunrise for specific equipment like position lights).
• IFR Flight (91.205(d)): Mandatory for all IFR operations, whether in visual meteorological conditions (VMC) or instrument meteorological conditions (IMC), day or night.
• High Altitude (91.205(e)): Mandatory at and above FL240 (24,000 feet MSL) if VOR navigation equipment is required.

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2. VFR Day Foundation: 14 CFR 91.205(b)

For standard powered civil aircraft with standard category airworthiness certificates, visual day operations require the equipment remembered by the mnemonic ATOMATO FLAMES (or A TOMATO FLAMES):

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3. VFR Night Layer: 14 CFR 91.205(c)

If the IFR flight is conducted at night (between the end of evening civil twilight and the beginning of morning civil twilight), the aircraft must also be equipped with FLAPS:

• F - Fuses: One spare set of fuses, or three spare fuses of each kind required immediately accessible to the pilot in flight (applies to aircraft using replaceable cartridge/glass fuses; not required if equipped entirely with circuit breakers).
• L - Landing Light: Required only if the aircraft is operated for hire (e.g., commercial passenger-carrying or flight training operations for hire). If flying privately/non-commercial under Part 91, a landing light is not strictly mandated by 91.205(c), though strongly recommended for safety.
• A - Anti-Collision Light System: Approved aviation red or white anti-collision light system.
• P - Position Lights: Navigation lights consisting of red (left wingtip, 110°), green (right wingtip, 110°), and white (tail, 140°).
• S - Source of Electrical Energy: Adequate battery, generator, or alternator to power all connected electrical equipment for the duration of the flight.

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4. IFR Specific Requirements: 14 CFR 91.205(d)

In addition to VFR day (and night, if applicable) equipment, 14 CFR § 91.205(d) mandates specialized equipment for IFR flight. The standard FAA mnemonic is GRABCARD (or GRAB CARDD):

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|                        14 CFR 91.205(d) - GRABCARD                          |
|                                                                             |
|   [G] Generator or Alternator of adequate electrical capacity               |
|   [R] Radios: Two-way communications & navigation suitable for route        |
|   [A] Altimeter: Sensitive type, adjustable for barometric pressure         |
|   [B] Ball: Slip-skid indicator (inclinometer)                              |
|   [C] Clock: Installed, displaying hours, minutes, seconds (sweep/digital)  |
|   [A] Attitude Indicator: Gyroscopic artificial horizon                     |
|   [R] Rate-of-Turn Indicator: Gyroscopic turn-and-slip or turn coordinator   |
|   [D] Directional Gyro: Gyroscopic heading indicator                        |
+-----------------------------------------------------------------------------+

Detailed Breakdown of GRABCARD Components

1. Generator or Alternator (G)

• An engine-driven electrical power source of adequate capacity to supply all required flight instruments, avionics, and electrical systems while simultaneously maintaining battery charge.
• FAA Exam Focus: A battery alone is insufficient for IFR flight; a primary generating source (alternator or generator) must be operational.

2. Radios for Communication and Navigation (R)

• Two-Way Radio Communications System: Capable of continuous communication with Air Traffic Control (ATC) on all assigned VHF frequencies along the intended route.
• Navigational Equipment: Appropriate to the ground-based facilities or space-based systems to be used (e.g., VOR, LOC, ILS, or IFR-certified GPS/RNAV).

3. Sensitive Altimeter (A)

• Unlike a rudimentary visual pressure altimeter, IFR operations legally require a sensitive altimeter equipped with an adjustable barometric subscale (Kollsman window) that allows setting the local altimeter setting in inches of mercury (inHg) or hectopascals (hPa).

4. Ball / Slip-Skid Indicator (B)

• An inclinometer (curved liquid-filled glass tube containing an agate or steel ball) to indicate aerodynamic coordination (slip or skid). Can be an independent instrument or integrated into the turn coordinator / turn-and-slip indicator.

5. Clock (C)

• 14 CFR 91.205(d)(6) Mandate: An installed clock displaying hours, minutes, and seconds with a sweep-second pointer or digital presentation.
• Critical Regulatory Nuance: The clock must be permanently installed in the aircraft. Portable wristwatches, smartphones, yoke-mounted timers, or flight bag stopwatches do NOT satisfy 14 CFR 91.205(d)(6).
• Operational Purpose: Required for timing holding pattern legs, missed approach timing from the Final Approach Fix (FAF) to the Missed Approach Point (MAP) on non-precision approaches, and timed instrument turns.

6. Attitude Indicator (A)

• A gyroscopic or electronic (AHRS-driven) artificial horizon displaying pitch and bank attitudes throughout 360° of roll and pitch.

7. Rate-of-Turn Indicator (R)

• A gyroscopic or solid-state rate-of-turn indicator (such as a standard 2-minute turn-and-slip indicator or an electrically driven turn coordinator).

8. Directional Gyro / Heading Indicator (D)

• A gyroscopic heading indicator or Horizontal Situation Indicator (HSI) that provides stabilized directional guidance without the dip and acceleration errors inherent in magnetic compasses.

[!NOTE] Gyroscopic Instrument Redundancy: In traditional "six-pack" steam-gauge aircraft, safety is enhanced by splitting power sources: the Attitude Indicator and Heading Indicator are typically powered by an engine-driven pneumatic/vacuum pump, while the Turn Coordinator is powered electrically by the 14V or 28V DC bus. In modern glass cockpits, an Attitude and Heading Reference System (AHRS) provides digital attitude and heading information, backed up by an independent electronic standby instrument with a dedicated emergency backup battery.

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5. High-Altitude DME & RNAV Requirements: 14 CFR 91.205(e)

Under 14 CFR § 91.205(e), specific navigational equipment is mandated for high-altitude operations:

• Flight Level 240 (FL240) Threshold: If IFR flight is conducted at or above 24,000 feet MSL (FL240) and VOR navigational equipment is required for the route, the aircraft must be equipped with approved Distance Measuring Equipment (DME) or a suitable RNAV (Area Navigation) system (such as an IFR-certified TSO-C129/C145/C146 GPS system).

In-Flight Failure of DME / RNAV at or above FL240

If DME or RNAV equipment fails while operating at or above FL240:

1. The pilot must notify ATC immediately.
2. The flight may continue to the next airport of intended landing where repairs or replacement equipment can be obtained.
3. ATC will accommodate the aircraft using radar vectors and alternative surveillance separation.

+-----------------------------------------------------------------------------+
|                  14 CFR 91.205(e) DME / RNAV DECISION MATRIX                |
|                                                                             |
|   Cruising Altitude >= FL240 (24,000' MSL) + VOR navigation required?       |
|         |                                                                   |
|         +---> YES ---> DME or suitable TSO-certified RNAV/GPS MANDATORY     |
|         |                                                                   |
|         +---> In-Flight DME Failure at FL240+?                              |
|               1. Notify ATC immediately                                     |
|               2. Continue to destination airport for maintenance            |
+-----------------------------------------------------------------------------+

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6. Summary Comparison of Required Instruments