Instrument Rating Study Guide — Pass the IRA Written Test

About the Instrument Rating Written Test

The FAA Instrument Rating Airplane (IRA) knowledge test is a 60-question, multiple-choice exam that you must pass before taking your instrument rating practical test (checkride). The test is administered at FAA-approved testing centers (PSI or CATS) and costs approximately $175. Here are the key details every applicant needs to know:

The test covers nine broad knowledge areas. The FAA draws questions from a large test bank, so no two exams are identical, but the topic distribution is consistent. Below is the approximate weight of each area:

Weather and navigation consistently make up the largest portion of the exam. Plan to dedicate extra study time to these areas. Your test report will show which areas you missed questions in, and your examiner will probe those areas during the oral exam.

IFR Regulations (14 CFR Part 91)

IFR regulations form the legal framework for instrument flight. The FAA tests your knowledge of specific regulatory requirements extensively. The bulk of IFR-specific rules are found in 14 CFR 91.167 through 91.193. You must know these cold.

IFR Currency Requirements

Under 14 CFR 61.57(c), to act as pilot-in-command under IFR or in weather conditions less than VFR minimums, you must have performed and logged the following within the preceding 6 calendar months:

If you fall out of currency, you have an additional 6 months to regain it by performing the required tasks. After the full 12 months, you must pass an instrument proficiency check (IPC) with an authorized instructor or examiner before you can fly IFR again.

IFR Fuel Requirements (91.167)

No person may operate a civil aircraft in IFR conditions unless it carries enough fuel to complete the flight to the first airport of intended landing, then fly from that airport to the alternate airport (if an alternate is required), and after that, fly for 45 minutes at normal cruising speed. This is different from VFR fuel requirements (30 minutes day / 45 minutes night). For IFR, it is always 45 minutes regardless of time of day.

IFR Alternate Requirements (91.169)

You must file an alternate airport in your IFR flight plan unless the weather forecast at your destination, from 1 hour before to 1 hour after your estimated time of arrival, indicates:

• Ceiling at least 2,000 feet above the airport elevation
• Visibility at least 3 statute miles

The memory aid for this is 1-2-3: 1 hour before/after ETA, 2,000-foot ceiling, 3 SM visibility. If the destination forecast does not meet all three criteria, you need an alternate. The alternate itself must meet separate weather criteria depending on whether it has a precision or non-precision approach.

Required Equipment and Instruments

For IFR flight, your aircraft must have all the instruments and equipment required by 14 CFR 91.205(d), in addition to the standard VFR-day and VFR-night equipment. The classic memory aid is GRABCARD:

IFR Minimum Altitudes

Under 91.177, when operating under IFR in controlled airspace, you may not operate below the published minimum IFR altitude (MEA, MOCA, MRA, or other applicable altitude). In mountainous terrain, if no applicable minimum altitude is prescribed, you must maintain at least 2,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles. In non-mountainous terrain, the clearance is 1,000 feet.

IFR Flight Planning & Procedures

IFR flight planning is more structured than VFR planning. You must file a flight plan, receive a clearance, and follow specific departure and arrival procedures. The FAA tests your understanding of the entire IFR planning process.

Filing an IFR Flight Plan

IFR flight plans can be filed through Flight Service (1-800-WX-BRIEF), online via 1800wxbrief.com, or through ForeFlight and similar EFB applications. You should file at least 30 minutes before your proposed departure time. Key elements of the IFR flight plan include: aircraft identification, aircraft type and equipment suffix (e.g., /G for GPS), true airspeed, departure point, proposed time, cruising altitude, route of flight, destination, estimated time en route, fuel on board, and alternate airport (if required).

IFR Clearances — CRAFT

Before departing IFR, you must receive and read back your ATC clearance. Use the CRAFT acronym to copy it:

SIDs and STARs

Standard Instrument Departures (SIDs) and Standard Terminal Arrival Routes (STARs) are published procedures designed to simplify clearance delivery and reduce radio congestion. SIDs provide a transition from the departure airport to the en route structure. STARs provide a transition from the en route structure to the approach environment at the destination. Both include altitude and speed restrictions that you must comply with unless explicitly amended by ATC. If you cannot accept a SID or STAR, you must advise ATC by writing "NO SID" or "NO STAR" in the remarks section of your flight plan.

IFR Cruising Altitudes

Under IFR in controlled airspace, ATC assigns your cruising altitude. In uncontrolled airspace (which is rare for IFR), the hemispheric rule applies: magnetic courses 0-179 degrees use odd thousands (3,000, 5,000, 7,000), and magnetic courses 180-359 degrees use even thousands (4,000, 6,000, 8,000). Above FL180, IFR flights operate in Class A airspace and altitudes are assigned by ATC.

IFR Weather Theory & Reports

Weather is the single largest topic area on the IRA knowledge test, representing approximately 18% of all questions. You must understand weather theory, be able to decode weather reports and forecasts, and know the hazardous conditions that affect IFR flight.

Structural Icing

Structural icing is one of the most dangerous weather hazards for IFR flight. It occurs when an aircraft flies through visible moisture (clouds or precipitation) at temperatures at or below freezing. There are three types:

• Rime ice — Rough, milky, opaque ice that forms when small supercooled water droplets freeze rapidly on contact. Most common in stratiform clouds. Relatively easy to remove with deice equipment.
• Clear ice — Smooth, glossy, transparent ice that forms when large supercooled water droplets spread and freeze slowly. Most common in cumuliform clouds and freezing rain. Hardest to remove and most dangerous.
• Mixed ice — A combination of rime and clear ice. Forms in complex cloud environments with varying droplet sizes.

The most hazardous icing condition is freezing rain, which produces rapid, severe clear ice accumulation. If you encounter freezing rain, you are likely below a temperature inversion — a layer of warm air above you is melting precipitation, which then supercools as it falls into subfreezing air. The immediate action is to climb (if possible) to get above the inversion into warmer air, or descend below the freezing level.

Thunderstorms

Thunderstorms contain virtually every weather hazard known to aviation: severe turbulence, icing, hail, microbursts, wind shear, lightning, and poor visibility. Thunderstorms develop in three stages: cumulus (building, updrafts only), mature (most dangerous, both updrafts and downdrafts, heavy precipitation), and dissipating (mostly downdrafts). The FAA recommends avoiding thunderstorms by at least 20 nautical miles. Never fly under a thunderstorm anvil or attempt to fly between cells that are less than 40 NM apart.

Fog Types

Fog is simply a cloud at ground level. Understanding how different types form helps you predict when visibility will deteriorate at your departure or destination:

• Radiation fog — Forms on clear, calm nights when the ground radiates heat and cools the air above it to its dewpoint. Burns off after sunrise. The most common fog type in the continental US.
• Advection fog — Forms when warm, moist air moves over a cooler surface. Common along coastlines. Can occur with wind (unlike radiation fog) and can persist day or night.
• Upslope fog — Forms when moist air is forced up a sloping terrain and cools adiabatically to its dewpoint.
• Steam fog — Forms when cold, dry air moves over a warmer water surface. Common over lakes in autumn.

Weather Reports & Forecasts

You must be able to decode METARs (routine observations), TAFs (terminal forecasts), PIREPs (pilot reports), AIRMETs, SIGMETs, and Convective SIGMETs. Key things the exam tests:

• METARs — Current surface conditions. Updated hourly or as SPECI when conditions change significantly.
• TAFs — Forecast for a 24-30 hour period. Uses FM (from), TEMPO (temporary), PROB (probability), and BECMG (becoming) change groups.
• PIREPs — Real-time reports from pilots. The only reliable source for actual icing and turbulence conditions aloft.
• AIRMETs — Advisories for moderate icing (AIRMET Zulu), moderate turbulence and low-level wind shear (AIRMET Tango), and IFR conditions/mountain obscuration (AIRMET Sierra).
• SIGMETs — Significant meteorological information for severe conditions: severe icing, severe or extreme turbulence, volcanic ash, dust storms reducing visibility below 3 SM.
• Convective SIGMETs — Issued for embedded thunderstorms, lines of thunderstorms, thunderstorms with severe turbulence/hail, or any tornado. Valid for 2 hours.

IFR Navigation Systems

Navigation systems are the backbone of instrument flight. The IRA exam tests your understanding of both ground-based and satellite-based navigation. While GPS/RNAV is becoming dominant, the FAA still tests extensively on VOR, ILS, and NDB systems.

VOR Navigation

VOR (VHF Omnidirectional Range) stations transmit 360 radials from the station. A VOR receiver displays your position relative to a selected radial using the CDI (Course Deviation Indicator). Key concepts:

• Each dot on the CDI represents 2 degrees of deviation from the selected course.
• Full-scale deflection (5 dots) = 10 degrees off course.
• The TO/FROM indicator tells you whether the selected radial would take you toward or away from the station.
• VOR accuracy must be checked every 30 days before IFR flight (91.171). Allowable error: +/-4 degrees on a ground checkpoint, +/-6 degrees on an airborne checkpoint, or +/-4 degrees on a dual VOR check.
• Standard VOR service volume: 40 NM within 1,000-14,500 ft AGL for a Low-altitude VOR.

Practice VOR navigation with our interactive VOR simulator. It lets you set courses, identify radials, and practice CDI interpretation — the exact skills the written test requires.

GPS and RNAV

GPS (Global Positioning System) and RNAV (Area Navigation) have become the primary navigation method for IFR flight. WAAS (Wide Area Augmentation System) provides enhanced accuracy for precision-like approaches (LPV). Key GPS/RNAV concepts for the test:

• RAIM (Receiver Autonomous Integrity Monitoring) — Required for non-WAAS GPS IFR navigation. Must be checked before departure. Requires a minimum of 5 satellites (6 for fault detection and exclusion).
• WAAS — Uses ground stations to correct GPS signal errors. Provides vertical guidance for LPV approaches. WAAS-equipped receivers do not require RAIM.
• CDI Scaling — GPS CDI sensitivity changes automatically: en route (+/-5 NM full scale), terminal (+/-1 NM), approach (+/-0.3 NM).
• Database currency — GPS database must be current (updated every 28 days) for IFR flight. You can use an expired database for en route and terminal operations if you verify waypoints, but approaches require a current database.

ILS Components

The Instrument Landing System (ILS) is the standard precision approach system. It consists of:

• Localizer — Provides lateral (left/right) guidance. Transmits on 108.10-111.95 MHz (odd tenths). Course width is 3-6 degrees (adjusted so full-scale deflection = 700 ft at the threshold).
• Glideslope — Provides vertical guidance. Typically 3 degrees. Transmits on 329.15-335.00 MHz (paired with localizer frequency). Full-scale deflection = 1.4 degrees (0.7 degrees per dot).
• Marker beacons — Outer marker (blue, dashes, 4-7 NM from runway), middle marker (amber, alternating dots and dashes, 3,500 ft from runway at ~200 ft on glideslope), inner marker (white, dots, at DA on CAT II approaches).
• Approach lighting — ALSF-1, ALSF-2, MALSR, and others. Approach lights with sequenced flashers extend 2,400-3,000 feet from the threshold.

IFR Charts & Approach Plates

Reading and interpreting IFR charts is a critical skill tested on the knowledge exam. You need to understand enroute low-altitude charts, approach plates (IAPs), SID and STAR charts, and the symbology used on each.

Enroute Low-Altitude Charts

IFR Enroute Low-Altitude (IFR-L) charts cover the airway structure from the surface up to but not including FL180 (18,000 feet MSL). Key elements include:

• Victor airways — VOR-based airways identified by "V" followed by a number (e.g., V16). Airway width is 4 NM either side of centerline.
• MEA (Minimum Enroute Altitude) — Lowest altitude on an airway segment that provides adequate navigation signal coverage and obstruction clearance. Printed above the airway line.
• MOCA (Minimum Obstruction Clearance Altitude) — Provides obstruction clearance for the entire airway segment but only guarantees navigation signal coverage within 22 NM of the VOR. Marked with asterisk and "T".
• MRA (Minimum Reception Altitude) — Lowest altitude at which a crossing radial can be received to define a fix.
• MCA (Minimum Crossing Altitude) — Minimum altitude at which you must cross a fix when proceeding in the direction of a higher MEA.
• MAA (Maximum Authorized Altitude) — Highest usable altitude on an airway segment.

Approach Plates (IAPs)

Instrument Approach Procedure (IAP) charts contain all the information you need to fly an instrument approach. Every approach plate has five standard sections:

1. Margin identification — Procedure name, airport name, city/state, and amendment date. Also shows approach category minimums and any special notes.
2. Plan view — Top-down view showing the approach course, fixes, holding patterns, missed approach track, and terrain/obstacles. Includes the MSA (Minimum Safe Altitude) circle, which provides 1,000 ft obstacle clearance within 25 NM of the navigation facility.
3. Profile view — Side view showing the vertical descent path, step-down fixes, glideslope intercept altitude, and final approach fix (FAF). The FAF is marked with a Maltese cross for non-precision approaches.
4. Minimums section — Lists DA/DH (precision) or MDA (non-precision) and required visibility for each aircraft approach category (A through E, based on 1.3 x Vso stall speed).
5. Airport diagram — Shows runways, taxiways, lighting, and elevation.

SID and STAR Charts

SID charts show the departure route from the airport to the en route structure. They include required climb gradients (standard is 200 ft/NM unless otherwise noted), altitude restrictions, and transition routes. STAR charts show the arrival route from the en route structure to the approach environment. Both may have speed restrictions (e.g., "250K" means maintain 250 knots). Any altitude followed by an underline means "at or above"; an overline means "at or below"; both means "at exactly."

Holding Patterns

Holding patterns are a fundamental IFR skill, and the FAA tests them extensively. You must understand standard and non-standard holds, entry procedures, timing, wind correction, and protected airspace.

Standard vs Non-Standard Holding

A standard holding pattern uses right turns. The inbound leg is flown toward the fix on the holding course. A non-standard hold uses left turns and is specified in the ATC clearance or on the approach plate. Unless otherwise instructed, all holds are standard (right turns).

Entry Procedures

There are three entry procedures, determined by your heading relative to the holding fix:

• Direct entry — When approaching the fix from the holding side. Simply fly to the fix and turn to enter the hold. The most straightforward entry.
• Teardrop entry — When approaching from the non-holding side at an angle. Fly to the fix, turn to a heading 30 degrees on the holding side of the reciprocal of the inbound course, fly for 1 minute, then turn to intercept the inbound course.
• Parallel entry — When approaching from the non-holding side nearly parallel to the inbound course. Fly to the fix, turn to fly the reciprocal of the inbound course (outbound parallel), fly for 1 minute, then turn toward the holding side to intercept the inbound course.

Timing and Leg Length

Standard holding pattern timing: 1 minute inbound leg at or below 14,000 feet MSL, 1.5 minutes inbound leg above 14,000 feet MSL. If ATC specifies a leg distance (DME or RNAV), use that instead of timing. You begin timing the outbound leg abeam the fix or upon completing the outbound turn, whichever comes later.

Holding Speeds

Maximum holding airspeeds protect against the aircraft leaving the protected airspace:

• Up to 6,000 ft MSL: 200 KIAS
• 6,001 to 14,000 ft MSL: 230 KIAS
• Above 14,000 ft MSL: 265 KIAS

You should start speed reduction 3 minutes before reaching the holding fix. If your aircraft cannot slow to the maximum holding speed, advise ATC and request a non-standard hold.

Our holding pattern entry tool lets you practice determining the correct entry (direct, teardrop, or parallel) for any inbound course and heading. Use it to build the spatial awareness these questions demand.

Approach Procedures

Understanding instrument approach procedures is essential for both the written test and real IFR flying. You must know the difference between precision and non-precision approaches, how to read minimums, and what to do at the missed approach point.

Precision vs Non-Precision Approaches

The key distinction is vertical guidance:

• Precision approaches — Provide both lateral and vertical guidance. Include ILS and PAR (Precision Approach Radar). Use a Decision Altitude (DA) or Decision Height (DH) — the altitude at which you must decide to land or execute the missed approach.
• Non-precision approaches — Provide lateral guidance only. Include VOR, NDB, LOC, RNAV (LNAV). Use a Minimum Descent Altitude (MDA) — you descend to MDA and level off until you see the runway environment or reach the missed approach point.
• APV (Approach with Vertical Guidance) — A newer category that provides both lateral and vertical guidance but does not meet precision approach standards. Includes LPV and LNAV/VNAV. Uses a Decision Altitude (DA).

Common Approach Types

Missed Approach Procedures

Every instrument approach has a published missed approach procedure. You must execute the missed approach if:

• You reach DA/DH (precision) or MAP (non-precision) without the required flight visibility or visual references.
• You are not in a position to make a normal approach and landing at any point.
• ATC instructs you to execute a missed approach.

The required visual references to descend below DA/DH or MDA include: approach lights (with red terminating bars or red side-row bars allows descent to 100 ft above TDZE), the runway threshold, threshold markings, threshold lights, REIL, VASI/PAPI, touchdown zone or markings, or the runway itself. If any of these are not distinctly visible, you must go missed.

Circle-to-Land Approaches

A circling approach allows you to land on a runway other than the one aligned with the instrument approach. Circling minimums are higher than straight-in minimums and are based on aircraft approach category. You must remain within the circling approach protected area (1.3-4.5 NM from each runway end, depending on category). If you lose visual contact with the runway during the circling maneuver, execute the missed approach for the approach you just flew — make an initial climbing turn toward the landing runway, then follow the published missed approach.

ATC Procedures & Communications

Working with ATC is integral to IFR flying. The written test focuses on clearances, communication procedures, and the critical topic of lost communications.

Lost Communication Procedures (91.185)

Lost communication is one of the most tested topics on the IRA exam. If you lose two-way radio communications in IMC, you must follow 14 CFR 91.185. The rules are straightforward once you know the framework:

Route: Fly the route in this priority order —

1. Assigned — The last route ATC assigned you
2. Vectored — If being vectored, fly direct to the fix or route ATC was vectoring you to
3. Expected — The route ATC told you to expect
4. Filed — Your filed flight plan route

Altitude: Fly the highest of —

1. The altitude assigned in the last clearance
2. The minimum IFR altitude (minimum — MEA)
3. The altitude you were told to expect

The memory aid is AVEF for route and AME (highest of) for altitude. For the "expected" altitude, you use it only after the point/time ATC told you to expect it. Before that fix or time, fly the highest of assigned or minimum.

Approach Timing on Lost Comm

When to begin your approach with lost communications: leave the clearance limit (usually your destination) to begin the approach as close as possible to the expected approach time (EAT) if one was given, or if no EAT was issued, as close as possible to your estimated time of arrival (ETA) from your filed or amended flight plan. If you arrive at the fix early, hold until your EAT or ETA.

Departure Procedures

Obstacle Departure Procedures (ODPs) and SIDs both provide obstacle clearance during the departure phase, but they serve different purposes. ODPs are designed solely for obstacle clearance and are textual or graphical. SIDs are ATC procedures designed for system efficiency and flow management. If a departure procedure is not assigned and no SID is filed, you are responsible for your own obstacle clearance after takeoff. The standard climb gradient for obstacle clearance is 200 feet per nautical mile, unless a greater gradient is specified.

Practice ATC communications with our ATC practice scenarios. It includes 30 real-world scenarios covering departures, arrivals, approaches, and emergency communications.

Human Factors & Aeronautical Decision Making

Human factors questions may represent only 5% of the test, but the concepts are critical for safe IFR flight. The exam focuses on spatial disorientation, visual illusions, and crew resource management.

Spatial Disorientation

Spatial disorientation occurs when the body's sensory systems provide conflicting information about the aircraft's attitude and motion. In IMC, your vestibular system (inner ear) is unreliable. The three primary types:

• The leans — The most common illusion. After a prolonged, unnoticed bank, a correction back to wings-level creates a sensation that you are banking in the opposite direction. Pilots may re-enter the original bank to "feel" level. Remedy: trust the instruments.
• Graveyard spiral — An unnoticed gradual bank tightens into a descending spiral. The pilot senses only the descent (not the bank) and pulls back on the yoke, tightening the spiral. This is a leading cause of VFR-into-IMC fatalities.
• Coriolis illusion — Caused by moving the head during a constant-rate turn. The semicircular canals are stimulated in two planes simultaneously, creating a sensation of tumbling. Extremely disorienting.
• Somatogravic illusion — Rapid acceleration (takeoff) creates a sensation of pitching up, which may cause the pilot to push the nose down. Rapid deceleration creates the opposite effect.

Visual Illusions During Approach

Several visual illusions can cause dangerous approach errors, especially during the transition from instruments to visual flight:

• Narrow runway — A runway narrower than usual creates the illusion of being too high, leading to a dangerously low approach.
• Wide runway — Creates the illusion of being too low, leading to a high approach and potential overshoot.
• Upsloping runway or terrain — Creates the illusion of being too high, leading to a low approach.
• Downsloping runway — Creates the illusion of being too low, leading to a high approach.
• Rain on the windscreen — Refracts light, making the runway appear farther away than it is, leading to a steep approach.
• Featureless terrain (black hole approach) — No visual references on approach over water or dark terrain. The pilot may descend below the glidepath without realizing it.

Aeronautical Decision Making (ADM)

ADM is the systematic approach to risk assessment and decision making. Key frameworks tested:

• IMSAFE checklist — Illness, Medication, Stress, Alcohol (8 hours bottle-to-throttle, 0.04 BAC limit), Fatigue, Emotion/Eating. Personal fitness check before every flight.
• PAVE — Pilot, Aircraft, enVironment, External pressures. Risk categories for preflight decision making.
• DECIDE model — Detect, Estimate, Choose, Identify, Do, Evaluate. In-flight decision-making process.
• Hazardous attitudes — Anti-authority, impulsivity, invulnerability, macho, resignation. Each has an antidote.

Interactive Study Tools

Reading about IFR concepts is just the start. The best way to internalize holding entries, VOR interpretation, and approach procedures is through hands-on practice. We built these free interactive tools specifically for instrument rating students:

Further Reading

This study guide covers all the knowledge areas, but the FAA publishes the definitive reference material. These are the primary sources the test questions are drawn from:

• FAA Instrument Flying Handbook (FAA-H-8083-15B) — The core textbook for instrument training. Covers flight by reference to instruments, navigation systems, approach procedures, and emergency operations.
• FAA Instrument Procedures Handbook (FAA-H-8261-1A) — Detailed coverage of departure, en route, arrival, and approach procedures. Essential for understanding the IFR system from a practical standpoint.
• Aeronautical Information Manual (AIM) — The pilot's guide to air traffic control, airspace, weather services, and procedures. Chapters 1, 4, 5, and 7 are especially relevant for instrument students.
• 14 CFR Part 91 (Subpart B, IFR rules) — Sections 91.167 through 91.193 contain the specific regulatory requirements for IFR flight that are tested on the exam.

For a complete overview of the instrument rating — requirements, costs, training timeline, and career benefits — see our Instrument Rating Complete Guide.

Frequently Asked Questions