ATOMATOFLAMES: The Required Equipment for Day VFR Flight (91.205b) Explained Item by Item
Updated: Sep 26
Before any flight, pilots are responsible for ensuring their aircraft is airworthy and properly equipped for the type of operation planned. For day VFR flight, the FAA specifies a minimum list of required instruments and equipment in 14 CFR 91.205(b), and most pilots memorize it with the acronym ATOMATOFLAMES. But the acronym has a couple of genuinely tricky points that trip up pilots and examiners — the two temperature-related items aren't redundant (one is for liquid-cooled engines, the other for air-cooled), several items are conditional (only required if the aircraft has certain features), and knowing what to do when a required item is inoperative is its own skill. Understanding ATOMATOFLAMES item by item — not just reciting it — is a foundation of legal, safe VFR flight and a guaranteed checkride topic.
This post covers day VFR required equipment in practical depth: what ATOMATOFLAMES stands for with each item explained, the crucial liquid-cooled versus air-cooled temperature distinction, which items are conditional, what's NOT required, and exactly what to do when required equipment is inoperative under 91.213.
Study this full length lesson (video, podcast, flashcards, and quiz) here: Full Length Lesson >
What ATOMATOFLAMES Is
ATOMATOFLAMES is a memory aid representing the required equipment for day VFR flight under 14 CFR 91.205(b).
The regulatory basis:
14 CFR 91.205 lists the instruments and equipment required for various operations
91.205(b) is the DAY VFR list (the baseline)
Night VFR (91.205(c)) and IFR (91.205(d)) ADD to this list
ATOMATOFLAMES covers the day VFR baseline
The layered structure:
Day VFR: ATOMATOFLAMES (91.205b)
Night VFR: ATOMATOFLAMES + FLAPS (the additional night items, 91.205c)
IFR: all of the above + GRABCARD (the additional IFR items, 91.205d)
Each operation builds on the previous
The consequence of missing equipment:
If any required item is missing or inoperative, the aircraft may not be legally flown
Unless properly deferred per the regulations (91.213 — below)
The equipment requirement is part of airworthiness for that operation
Know the list and the deferral rules
ATOMATOFLAMES Explained, Item by Item
Here's each letter with what it requires and the condition attached.
A — Airspeed Indicator:
Displays the aircraft's speed relative to the air
Critical for safe takeoff/landing speeds, avoiding stalls, managing performance
Always required
T — Tachometer (for each engine):
Displays engine RPM
One for EACH engine (twins need one per engine)
Essential for managing power and monitoring the engine
Always required (one per engine)
O — Oil Pressure Gauge (for each engine using pressure system):
Indicates engine oil (lubrication) pressure
Low oil pressure signals imminent engine trouble
One of the most critical engine instruments
Required for each engine using a pressure oil system
M — Manifold Pressure Gauge (for each altitude engine / constant-speed prop):
Displays engine intake manifold pressure
Used with RPM to set power on aircraft with a constant-speed (controllable-pitch) propeller
Required for each "altitude engine" (and in practice, aircraft with controllable-pitch props)
Conditional (not required for fixed-pitch, non-altitude engines)
A — Altimeter:
Shows altitude above mean sea level (with the current setting)
Essential for terrain clearance and airspace compliance
Must be set to the current altimeter setting
Always required
T — Temperature Gauge (for each LIQUID-COOLED engine):
A temperature gauge for each LIQUID-COOLED (liquid/coolant-cooled) engine
Monitors the coolant temperature
Required ONLY for liquid-cooled engines
Most training aircraft are AIR-cooled, so this "T" often doesn't apply to them
The key nuance: this is the LIQUID-cooled engine item
O — Oil Temperature Gauge (for each AIR-COOLED engine):
An oil temperature gauge for each AIR-COOLED engine
Monitors oil temperature (critical for air-cooled engines that rely on oil for cooling)
Required for air-cooled engines
Most trainers ARE air-cooled, so this "O" DOES apply to them
The counterpart to the liquid-cooled "T"
The critical T-vs-O distinction:
These two are NOT redundant
T (temperature gauge): for LIQUID-cooled engines (coolant temp)
O (oil temperature gauge): for AIR-cooled engines (oil temp)
An air-cooled trainer needs the oil temp gauge (O), not the liquid-coolant gauge (T)
A liquid-cooled engine needs the coolant temp gauge (T)
This distinction is commonly tested — don't blur them
F — Fuel Gauge (for each tank):
A fuel quantity indicator for each tank
Helps prevent fuel exhaustion
Required to be installed and functional (indicating usable fuel — recall the gauge must indicate usable quantity)
One per tank
L — Landing Gear Position Indicator (if retractable gear):
Confirms landing gear position (up/down)
Helps prevent gear-up landings
Required ONLY if the aircraft has retractable landing gear
Conditional (fixed-gear aircraft don't need it)
A — Anti-Collision Lights:
Rotating beacon and/or strobe lights
Enhances aircraft visibility
Required for aircraft certificated after a certain date (most modern aircraft)
May be turned off if their operation would be unsafe (the pilot judgment provision)
Note: for aircraft certificated after March 11, 1996, anti-collision lights are required equipment
M — Magnetic Compass:
Provides heading information independent of electrical power
The basic backup navigation instrument
Required even with advanced avionics (it needs no power)
Always required
E — Emergency Locator Transmitter (ELT):
Used to locate the aircraft after an accident
Must be installed and operational (per 91.207)
Subject to inspection and battery requirements
Required (with the limited exceptions covered in ELT rules)
S — Safety Belts (and shoulder harnesses where required):
A safety belt (seat belt) for each occupant
Must be installed and usable
Shoulder harnesses are required for certain seats/aircraft (front seats of aircraft certificated after specific dates)
Required for each occupant
Which Items Are Conditional
A key understanding: several ATOMATOFLAMES items are only required IF the aircraft has certain features. Knowing which are conditional is important.
The conditional items:
M (Manifold pressure gauge): only for aircraft with a constant-speed (controllable-pitch) propeller / altitude engine
T (Temperature gauge): only for LIQUID-cooled engines
O (Oil temperature gauge): for AIR-cooled engines (so this applies to most trainers)
L (Landing gear position indicator): only for retractable-gear aircraft
The always-required items:
A (Airspeed indicator)
T (Tachometer — for each engine)
O (Oil pressure gauge)
A (Altimeter)
F (Fuel gauge — each tank)
A (Anti-collision lights — for aircraft so certificated)
M (Magnetic compass)
E (ELT — with exceptions)
S (Safety belts)
Why the conditional nature matters:
A fixed-gear, fixed-pitch, air-cooled trainer doesn't need the manifold pressure gauge (M) or the liquid-cooled temp gauge (T) or the gear indicator (L)
But it DOES need the oil temp gauge (O)
Know which items apply to YOUR aircraft
The conditional items depend on the aircraft's configuration
The typical trainer:
A Cessna 172 (fixed-gear, fixed-pitch, air-cooled): needs airspeed, tach, oil pressure, altimeter, oil temp (O), fuel gauges, anti-collision lights, compass, ELT, safety belts
Doesn't need manifold pressure (M — no constant-speed prop), liquid temp (T — air-cooled), or gear indicator (L — fixed gear)
Understanding this makes the acronym practical
What's NOT Required for Day VFR
Clearing up common misconceptions about what you DON'T need.
NOT required for day VFR:
Radios (com/nav): not required for day VFR (unless operating in airspace that requires them, like Class B/C/D communication)
GPS: not required
Transponder: not part of ATOMATOFLAMES (but required by airspace rules — Class A/B/C, veil, above 10,000)
ADS-B: not part of ATOMATOFLAMES (but required by airspace rules — 91.225)
Attitude indicator, heading indicator, turn coordinator: these are IFR items (not required for day VFR)
Vertical speed indicator: not required
The radio misconception:
Day VFR in Class E or G (uncontrolled/no comm requirement): no radio required
But entering Class B, C, or D requires communication (a radio)
The airspace drives the radio requirement, not 91.205
ATOMATOFLAMES doesn't include a radio
The transponder/ADS-B clarification:
These are required by AIRSPACE rules (91.215, 91.225), NOT by 91.205
They're not in ATOMATOFLAMES
But you may still need them for the airspace you're flying in
Separate requirements
The gyroscopic instruments clarification:
The attitude indicator, heading indicator, and turn coordinator are for IFR (part of GRABCARD)
NOT required for day VFR
A day-VFR aircraft doesn't legally need them
They're IFR equipment
What If Equipment Is Inoperative? (91.213)
Knowing what to do with inoperative equipment is a critical, tested skill — the flip side of knowing the list.
The basic rule:
If a required item is inoperative, the aircraft is generally NOT airworthy
UNLESS the inoperative equipment is properly deferred
Two paths to deferral: an MEL, or the 91.213(d) provisions
Path 1 — Minimum Equipment List (MEL):
Some aircraft operate under an approved MEL
The MEL specifies what can be inoperative and under what conditions
If the aircraft has an MEL, it must be followed for inoperative equipment
More common in commercial/complex operations
Path 2 — 91.213(d) (without an MEL):
For aircraft without an MEL (most GA), 91.213(d) provides the deferral process
A four-step determination (below)
The common path for GA
Allows flight with certain inoperative equipment
The 91.213(d) process:
To fly with inoperative equipment (no MEL), the equipment must NOT be:
Part of the VFR-day type certification requirements (91.205b — ATOMATOFLAMES items)
Indicated as required on the aircraft's equipment list or KOEL (Kinds of Operation Equipment List) for the kind of flight
Required by 91.205 (or other rule) for the specific operation
Required by an Airworthiness Directive
If it passes those checks:
The inoperative equipment must be removed or deactivated and placarded "INOPERATIVE"
A determination made (by a pilot or mechanic, as appropriate) that it doesn't constitute a hazard
Then the aircraft can be flown with the item inoperative
Properly deferred
The key point about ATOMATOFLAMES items:
The ATOMATOFLAMES (91.205b) items generally CANNOT be deferred for day VFR
They're required by the VFR-day certification/operation
An inoperative ATOMATOFLAMES item usually grounds the aircraft (for day VFR)
The deferral process is for equipment NOT required by 91.205
The placard requirement:
Inoperative equipment (that's deferred) must be placarded "INOPERATIVE"
And deactivated/removed as appropriate
The placard alerts everyone the item is inop
Required for deferral
Who makes the determination:
For simple deferrals, the pilot can determine (and placard) per 91.213(d)
Some situations require a mechanic
The determination that it's not a hazard is required
Follow the process
The Airworthiness Connection
How ATOMATOFLAMES ties to the broader airworthiness picture.
The equipment requirement is part of airworthiness:
For day VFR, the aircraft must have the required equipment (91.205b) operational
Missing/inoperative required equipment (not deferred) = not airworthy for day VFR
The pilot verifies this before flight (91.7)
Part of the airworthiness determination
The pilot's responsibility:
The PIC determines the aircraft is airworthy before flight
This includes verifying the required equipment is present and operational
Checking for inoperative equipment
Deferring properly if needed
The preflight check:
Verify the ATOMATOFLAMES items (as applicable to the aircraft)
Check they're operational
Address any inoperative equipment (deferral or no-go)
A standard part of preflight
Common Misconceptions
"The two temperature gauges are the same thing."
No — T is the temperature gauge for LIQUID-cooled engines; O is the oil temperature gauge for AIR-cooled engines. They apply to different engine types.
"Radios are required for day VFR."
Not by 91.205. Radios are required by airspace rules (Class B/C/D communication), not for day VFR generally.
"A transponder is part of ATOMATOFLAMES."
No — transponders and ADS-B are required by airspace rules (91.215, 91.225), not by 91.205.
"Every item in ATOMATOFLAMES is always required."
Several are conditional: manifold pressure (constant-speed prop), the liquid temp gauge (liquid-cooled engines), and the gear indicator (retractable gear).
"I can defer any inoperative instrument."
The ATOMATOFLAMES (91.205b) items generally can't be deferred for day VFR. The 91.213(d) deferral is for equipment NOT required by 91.205.
"Inoperative equipment just needs a placard."
It must be placarded AND deactivated/removed as appropriate AND determined not to be a hazard AND not required by 91.205, the equipment list, or an AD.
Why ATOMATOFLAMES Matters
Understanding it helps pilots:
Ensure legal compliance for day VFR
Make sound go/no-go decisions
Handle inoperative equipment correctly
Prepare for checkrides and flight reviews
Conduct thorough preflight inspections
Failing to comply with equipment requirements can lead to enforcement action, insurance complications, and increased risk. ATOMATOFLAMES is more than a memory aid — it's the foundation of legal day VFR flight. And knowing the nuances (the liquid-cooled versus air-cooled temperature distinction, the conditional items, the deferral rules) is what separates reciting the acronym from actually applying it.
On the Written Test and Checkride
Day VFR required equipment appears consistently on tests and checkride orals. The most commonly tested topics:
The ATOMATOFLAMES items (91.205b)
The liquid-cooled (T) vs. air-cooled (O) temperature distinction
Which items are conditional (manifold pressure, gear indicator, etc.)
What's NOT required (radios, transponder, gyros for day VFR)
The inoperative equipment process (91.213)
The layered structure (day VFR + FLAPS for night + GRABCARD for IFR)
Quick Reference
ATOMATOFLAMES (Day VFR — 91.205b):
A — Airspeed indicator
T — Tachometer (each engine)
O — Oil pressure gauge
M — Manifold pressure gauge (constant-speed prop / altitude engine)
A — Altimeter
T — Temperature gauge (each LIQUID-cooled engine)
O — Oil temperature gauge (each AIR-cooled engine)
F — Fuel gauge (each tank)
L — Landing gear position indicator (if retractable)
A — Anti-collision lights (if certificated after 3/11/96)
M — Magnetic compass
E — ELT
S — Safety belts (+ shoulder harnesses where required)
The T vs. O Distinction (KEY):
T — temperature gauge for LIQUID-cooled engines
O — oil temperature gauge for AIR-cooled engines
NOT redundant — different engine types
Most trainers are air-cooled (need the O)
Conditional Items:
Manifold pressure (M): constant-speed prop / altitude engine
Liquid temp (T): liquid-cooled engines only
Gear indicator (L): retractable gear only
NOT Required for Day VFR:
Radios (unless airspace requires)
GPS
Transponder/ADS-B (airspace rules, not 91.205)
Attitude indicator, heading indicator, turn coordinator (IFR)
VSI
Layered Requirements:
Day VFR: ATOMATOFLAMES (91.205b)
Night VFR: + FLAPS (91.205c)
IFR: + GRABCARD (91.205d)
Inoperative Equipment (91.213d, no MEL):
Equipment can be deferred only if NOT:
Required for VFR-day certification (ATOMATOFLAMES)
On the equipment list/KOEL as required
Required by 91.205 for the operation
Required by an AD
Then: remove/deactivate, placard "INOPERATIVE," determine not a hazard
Key Point on Deferral:
ATOMATOFLAMES items generally CANNOT be deferred for day VFR
Deferral is for equipment NOT required by 91.205
Key Principle:
ATOMATOFLAMES is the day VFR required equipment (91.205b). Several items are conditional — manifold pressure (constant-speed prop), the gear indicator (retractable), and critically, the two temperature items are NOT redundant: T is for liquid-cooled engines, O (oil temp) is for air-cooled engines (most trainers). Radios, transponders, and gyros aren't required for day VFR by 91.205. Inoperative required equipment grounds the aircraft unless properly deferred under 91.213.
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Author: Nathan Hodell
CFI, CFII, MEI, ATP, Creator and CEO
Nathan is an aviation enthusiast with thousands of hours of flying and dual instruction over the past 15+ years. Through his aviation career he has been able to earn his ATP, fly as an airline pilot, own/operate flight schools, and create and host wifiCFI.