The Toolbox — Charts

Aviation

Standard V-speeds, US airspace classification, ATC light gun signals, METAR cloud cover and weather codes, and wake turbulence categories.

Standard V-Speeds

Generic definitions — consult the specific aircraft's POH/AFM for actual published speeds.

Speed	Name	Notes
V1	Takeoff decision speed	Last speed at which a rejected takeoff can be initiated within the runway distance available
Vr	Rotation speed	Speed at which the pilot begins rotation to takeoff attitude
V2	Takeoff safety speed	Minimum speed to maintain climb performance with one engine inoperative
Vx	Best angle of climb speed	Maximum altitude gain per unit of horizontal distance — used for obstacle clearance
Vy	Best rate of climb speed	Maximum altitude gain per unit of time
Vfe	Maximum flap extended speed	Top of the white arc — do not exceed with flaps extended
Vno	Maximum structural cruising speed	Top of the green arc — exceed only in smooth air
Vne	Never exceed speed	Red line — must never be exceeded in any condition
Va	Design maneuvering speed	Maximum speed for full, abrupt control deflection without structural damage; decreases with weight
Vs1	Stall speed, specified configuration	Typically clean configuration — bottom of green arc
Vs0	Stall speed, landing configuration	Gear and flaps down — bottom of white arc
Vmc	Minimum control speed	Multi-engine — minimum speed to maintain directional control with critical engine inoperative
Vle	Maximum landing gear extended speed	Do not exceed with gear extended
Vlo	Maximum landing gear operating speed	Do not exceed while extending or retracting gear
Vg	Best glide speed	Maximum glide distance per unit of altitude lost — engine-out emergency speed

Vertical limits and specific entry requirements vary by location — always check current sectional charts and the AIM for the airspace in question.

Class	Typical Vertical Limits	Entry Requirement	VFR Minimums (day)
A	18,000 ft MSL – FL600	IFR only — ATC clearance and instrument rating required	VFR not permitted
B	Surface – 10,000 ft MSL (varies)	ATC clearance required to enter; around the busiest airports	3 SM visibility, clear of clouds
C	Surface – 4,000 ft AGL (varies)	Two-way radio contact established before entry	3 SM visibility, 500 ft below / 1,000 ft above / 2,000 ft horizontal from clouds
D	Surface – 2,500 ft AGL (varies)	Two-way radio contact established before entry	3 SM visibility, 500 ft below / 1,000 ft above / 2,000 ft horizontal from clouds
E	Varies — often 700/1,200 ft AGL to 18,000 ft MSL	No clearance or radio contact required for VFR	3 SM / 500-1,000-2,000 below 10,000 ft MSL; 5 SM / 1,000 ft above and below, 1 SM horizontal above 10,000 ft MSL
G	Surface up to the floor of overlying controlled airspace	Uncontrolled — no ATC clearance or radio contact required	Varies by altitude and day/night — as low as 1 SM and clear of clouds by day below 1,200 ft AGL

Used by the tower to communicate with aircraft or ground vehicles without functioning radios (FAA AIM 4-3-13).

Signal	Meaning
Steady green	Cleared for takeoff
Flashing green	Cleared to taxi
Steady red	Stop
Flashing red	Taxi clear of the runway in use
Flashing white	Return to starting point on the airport
Alternating red and green	Exercise extreme caution

Signal	Meaning
Steady green	Cleared to land
Flashing green	Return for landing (to be followed by steady green at the proper time)
Steady red	Give way to other aircraft and continue circling
Flashing red	Airport unsafe — do not land
Alternating red and green	Exercise extreme caution

Standard abbreviations used in METAR and TAF reports.

Code	Meaning
SKC	Sky clear — 0/8 coverage (manually reported)
CLR	Clear below 12,000 ft — automated station, no clouds detected
FEW	Few — 1 to 2 oktas coverage
SCT	Scattered — 3 to 4 oktas coverage
BKN	Broken — 5 to 7 oktas coverage
OVC	Overcast — 8 oktas coverage
VV	Vertical visibility — indefinite ceiling, e.g. fog or heavy precipitation

Used by ATC for separation standards and radio phraseology — e.g. a Boeing 777 identifies as "Heavy" on initial contact.

Category	Weight	Notes
Super	Aircraft specifically designated by the FAA (e.g. A380-800, An-225)	Requires the greatest wake turbulence separation
Heavy	Max certificated takeoff weight > 300,000 lbs (136,000 kg)	Uses "Heavy" callsign suffix on initial contact — e.g. B747, B777, A330
Large	Max certificated takeoff weight 41,000 – 300,000 lbs	Most narrow-body airliners — e.g. B737, A320
Small	Max certificated takeoff weight ≤ 41,000 lbs	Most general aviation and regional aircraft