"THE ACUG 2025" - STUDY GUIDE #3

It’s a government-operated service that provides pre-flight, in-flight, and emergency assistance to pilots.

It is a clearance that allows a pilot to fly visually within controlled airspace even when the weather is below standard VFR minimums.

• The name of the airport, usually bold and all caps. Example: “SANTA ROSA (STS)”

• The 3-letter (or 4-letter) Code (right of the name) is assigned by the FAA,(*not ICAO)
  Example: LAX, JFK, DFW.
• 
  

• “CT” followed by a frequency means a control tower is present and that’s the Tower frequency.
  Example: “CT 118.3” = Control Tower 118.3 MHz.

• The control tower does not operate continuously, it’s part-time. The control tower is not open 24 hours.

• When no tower, “CTAF” (Common Traffic Advisory Frequency) shows the frequency pilots use to self-announce in the traffic pattern. Blue symbol means the CTAF os the CT Frequency. when the tower is closed. Example: “CTAF 118.3.”

• ATIS: Automatic Terminal Information Service (for towered airports). it’s a continuous, pre-recorded broadcast of the current weather and airport information at high-activity towered airports and terminal areas.

Example: ATIS 123.8 Mhz

⭐️AWOS/ASOS: Automated Weather Observation (provides current weather).

Height of the airport’s highest runway point above mean sea level (MSL).Example: “1287” means the field elevation is 1,287 ft MSL.

Indicates the airport is lighted in operation during sunset to sunrise. (*L) The asterisk (*) before the L means that lighting limitations exist, such as the lights not operating continuously (for example, they might only be on part-time, pilot-controlled, or on request).
 

72 indicates the length of the  Longest runway at the airport is 7,200 ft (multiply by 100)
 

UNICOM stands for Universal Communications. It is a non-governmental, non-towered airport frequency used at general aviation airports for pilot-to-pilot and pilot-to-ground communications.

• Usually 122.7, 122.8, or 122.95 MHz. At airports without a control tower, UNICOM acts as the main frequency for traffic advisories.
  

⭐️ RP = Runway Pattern 23, 34
The number(s) that follow = runway(s) this applies to Sometimes it’s accompanied by L or R to indicate left-hand or right-hand traffic patterns. If there’s no L or R, assume left-hand traffic pattern (standard).

Example RP L23, R34 

• Runway 23-When landing or taking off, turn left in the traffic pattern.
• Runway 34-When landing or taking off, turn right in the traffic pattern.

👉"Solid Blue Lines"

Surrounds the nation’s busiest airports (like LAX, ATL, etc.).
Typically shaped like an upside-down wedding cake (multiple tiers). Requires: ATC clearance before entry
Mode C transponder (ADS-B Out also required. Shown with altitude limits (e.g., “SFC – 100” means surface to 10,000 ft MSL). *Always Referenced in MSL.

👉"Solid Magenta Lines"
Surrounds medium-size airports with control towers and radar approach (like Tucson or Boise).
Two rings: Inner core: 5 NM radius, Surface to 4,000 ft MSL
Outer shelf: 10 NM radius, 1,200 ft to 4,000 ft MSL
Requires radio contact before entry (“ATC says your call sign back”).
Mode C transponder and ADS-B Out required. *Always Referenced in MSL.

👉"Dashed Blue Line"
Smaller towered airports (e.g., Santa Monica). Generally surface to 2,499 ft MSL. Must establish two-way communication before entry.
May have a "boxed ceiling number" like [25] = up to 2,500 ft MSL.

Boxed numbers such as [-25] means the
airspace extends "up to and including" 2,500 feet MSL, which equals (2,499 MSL) (technically just below 2,500 MSL).
 

⭐️When tower closed, it reverts to Class E (dashed magenta) or Class G.

Several types of boundaries:

• Dashed Magenta line Class E starting at the surface. 
• Faded Magenta boundary Class E starting at 700 ft AGL (shaded side = inside the Class E).
• Faded blue vignette — Class E starting at 1,200 ft AGL.
• No Faded Magenta, Class E starting at 14,500 ft MSL (up to but not including 18,000 ft MSL). Used for controlled airspace that supports IFR traffic and controlled transitions from en route to surface areas. 

Class E Altitude Reference: 

Starts at surface, extends up (the ceiling can either be referenced in AGL or MSL).

So Class E can begin at surface, 700 AGL, 1,200 AGL, or 14,500 MSL, depending on the type and location.

👉Uncontrolled Airspace (no shading or dashed lines). Exists wherever Class E doesn’t begin. Starts at the surface and goes up to: 700 ft AGL (under magenta boundary) 1,200 ft AGL (under faded blue boundary)
 

Class G could extend higher in remote areas, but you are only allowed to fly at or below 400 feet AGL. 

*Always Referenced in AGL.

Airspace in the U.S. is divided into Classes A, B, C, D, E, and G, each with different rules and altitude ranges. Class A (18,000–60,000 ft MSL) is for IFR traffic only. Class B surrounds the busiest airports, shaped like an upside-down wedding cake, requiring ATC clearance for all aircraft. Class C covers medium airports with control towers and radar; you must establish two-way radio communication before entry. Class D surrounds smaller towered airports and also requires two-way communication. Class E is controlled airspace that fills in the gaps between the others, starting at 700 or 1,200 ft AGL up to 18,000 ft MSL. Class G is uncontrolled airspace below Class E, usually near the surface in rural areas, where pilots operate without ATC communication.

Refer to the Chart Supplement for more information about Chart Symbols. 

⭐️ Obstructions

On a sectional chart, obstructions represent man-made objects that could pose hazards to aircraft, such as towers, antennas, wind turbines, and buildings. They are critical for pilots, especially those flying at low altitudes (like drone pilots or general aviation).

*Notice the lightning bolts which indicate the obstruction has high-intensity lights.

👉Review the symbols under the Miscellaneous section; Glider, Parachute Jumping, ect.

Obstructions will be numbers next to it; a Top number over a Bottom number. 

Top Number represents the height of the tower referenced in MSL, and the bottom number represents the height of the tower in AGL. 

⭐️ Magenta Flag Symbol 

You see on the sectional chart there magenta flag called a "VFR Checkpoint."

It's a visual reference point used by pilots for VFR (Visual Flight Rules) navigation and communication with ATC.

When flying visually (not relying on instruments), pilots report their position to Air Traffic Control (ATC) using easily identifiable ground features.
When ATC wants a position report, a pilot might say:

“Los Angeles Approach, Cessna 23A, over Pomona Fairgrounds, 2,500 feet, inbound for landing.” Here, “Pomona Fairgrounds” would be a VFR checkpoint (magenta flag).

Notice in the legend there is a blue zipper-like symbol line is officially called:

“Class E Airspace Boundary with Varying Floors”
or more specifically,
“Class E airspace with floor other than 700 ft or 1,200 ft AGL.”

Notice on the legend: 2,400 feet MSL on one side, and 4,500 feet MSL on the other side. The blue zipper line separates areas of Class E airspace that begin at different altitudes. 

• The floor values (like 700 ft, 1,200 ft, or a specific MSL altitude such as 7,000 ft) are labeled next to the boundary in hundreds of feet MSL (for example, “10,500” or “7000”).
   
• These airspace areas are not transition zones around airports, but rather en-route Class E designed to contain IFR operations between controlled areas.

• Blue: Towered (has an operating control tower). Magenta: Non-towered airports. 
•  

⭐️ Private or Restricted Use“R” or “Pvt” indicates restricted or private use.Example: “Pvt” = Private airfield. 

⭐️ VOR or Other Navaid SymbolIf there’s a small hexagon or compass rose nearby, that airport has a VOR or NDB on the field.

Review all symbols in the legend for more details and information about Chart Symbols.