Lesson 302.2 and 302.3

Air Traffic Control: Airport Structure and Routing Philosophies

• Airport Categorization and Complexity:

  • Structured vs. Non-structured Airports: In the past, Halifax functioned as a "busiest non-structured airport," often described as the "wild wild West" because aircraft arrived and departed from all runways simultaneously.
  • Tier 1 Structured Airports: Montreal, Toronto, Vancouver, and Calgary are explicitly structured. This involves routing aircraft to specific gates or fixes to maintain order.
  • The Problem with Gate Dabbing: Attempting to force "gates" on previously non-structured airports (like Halifax) often creates "clustered bog," where moving one aircraft into place creates a conflict for another.
  • Coordination on the Hotline: In structured environments, controllers use hotlines to coordinate positioning (e.g., "Where do you want this guy?" or "I'll put him up there, you put him down there").

• Navigation Capabilities and Flight Planning:

  • Modern GPS Capabilities: Approximately $98\%$ to $99\%$ of airline customers are GPS-capable and can be routed "direct to any fix."
  • Exceptions: Smaller aircraft like Navajos may have limited capabilities.
  • Flight Plan Indicators: Codes such as $/s$, $/g$, or $/f$ indicate a specific aircraft's navigational equipment and capabilities.

Proactive vs. Reactive Control Strategies

• Philosophy of Control:

  • Reactive Controlling: Represented by the mantra "Smoke them all. Watch it. If it's not working, we'll fix it." This is deemed an unsustainable and dangerous strategy in modern ATC.
  • Proactive/Pre-planned Controlling: Controllers must look into the future to project where an aircraft will be. A proactive controller looks for traffic above their "toker" or before the handoff from other sectors (like HHS) occurs.

• The Transition Decision:

  • When managing the intersection of two flight paths, the controller makes a fundamental choice: "Do I snap him in front?" or "Do I take him off [the path]?"
  • Matter of Technique: Instructors note that while they may prefer one method (e.g., letting an aircraft run behind a Speedbird rather than cranking an Air Canada in front), a student will not be marked down as long as they maintain separation and the execution is efficient.

Managing Arrivals and Departures

• Flight Management Systems (FMS) and Descents:

  • Arrivals are on highly regulated descent profiles calculated by the FMS. The FMS might dictate an unrestricted descent from cruise to $3,000\,\text{feet}$ to pick up the glideslope.
  • Performance Constraints: It is difficult for jets to slow down and descend simultaneously. If an arrival is held high (e.g., at $24,000\,\text{feet}$ when they should be transitioning lower), they will "hump the red line" trying to catch up, making it impossible for Terminal to manage speed (e.g., reducing to $240\,\text{kts}$ or $210\,\text{kts}$).

• The Priority Hierarchy:

  • The descent of an arrival is generally more important than the climb of a departure. It is considered "less egregious" to level off or stop a departure's climb because departures are still establishing their en route phase.

• Visualizing the Solution:

  • Stop and Pop: A method where an aircraft is momentarily leveled off to allow another to pass vertically or laterally.
  • Parallel Offsets: Offsetting a departure to the west or east to allow a line of arrivals to pass through a corridor.
  • Endpoint Coordination: Every plan should have an endpoint, such as the final vector back on course or a hand-off to the next sector.

Aviation Weather and Forecasting

• Standard Weather Tools:

  • ATIS (Automatic Terminal Information Service): Provides the "canned" info, including the METAR, active runway, and altimeter settings.
  • METAR vs. SPECI: METARs are hourly reports; SPECIs are issued when significant changes occur.
  • TAF (Terminal Area Forecast): A forecast for a 24-hour period, broken into blocks of time.

• Weather Reporting Terms:

  • TEMPO: Temporary fluctuations in weather conditions.
  • PROB: Probability (e.g., $30\%$ probability of light snow/fog).
  • BECMG: Becoming (transitional weather periods).

• Hazardous Weather Phenomena:

  • Low-Level Wind Shear (LLWS): Sudden changes in wind speed/direction. An "Advisory" indicates a detected change, but an "Alert" is often an automatic go-around trigger for pilots.
  • Microbursts: Intense downdrafts that splay out. Pilots initially experience a headwind (increased performance), then a downdraft, then a tailwind (drastic performance loss).
  • Case Study (Delta 191): An L-1011 (often misremembered as a DC-10) crashed in Dallas due to wind shear. Simulators later proved that the only way to survive was full power immediately upon the initial airspeed increase.
  • Icing Types:
    • Rime: Granular ice, often found on windshields.
    • Clear: Sheet-like ice, potentially the most hazardous.
    • Mixed: A combination of rime and clear ice.
  • Arrow Air (Gander) Tragedy: A DC-8 crashed due to ice on the wings deforming aerodynamic quality, raising the stall speed (e.g., needing $163\,\text{kts}$ but only having $143\,\text{kts}$).

• OIDS (Operational Information Display System): Provides real-time updates on altimeter settings, ILS in use, RVR (Runway Visual Range updated every $7$ to $10\,\text{seconds}$), and surface conditions (RSC/CRFI).

Wake Turbulence and Aircraft Categories

• Categorization by Weight:

  • Super (J): Airbus A380 or Antonov An-225 ($AM-225$).
  • Heavy (+): Large jets like Boeing 747 or 777. The Boeing 757 is treated as a Heavy specifically when leading Medium aircraft.
  • Medium: Standard commercial jets (e.g., Embraer 190, Boeing 737).
  • Light (-): Small aircraft like the Citation ($C-550$) or Beech 1900.

• Separation Minimums (Distance in Miles):

  • Light behind Super: $8\,\text{miles}$.
  • Medium behind Super: $7\,\text{miles}$.
  • Heavy behind Super: $6\,\text{miles}$.
  • Light behind Heavy: $6\,\text{miles}$.
  • Medium behind Heavy: $5\,\text{miles}$.
  • Super behind Super: $4\,\text{miles}$.

• Operational Rules for Wake Turbulence:

  • Vortices are a byproduct of lift; they start at rotation (takeoff) and end when the wheels touch down.
  • The "Daylight" Rule: Even if there is visual "daylight" between departing aircraft, you cannot climb an aircraft through the wake of a preceding heavy/super until the distance requirements are met.

Speed Control Techniques

• General Rules:

  • "Vectors to achieve, Speed to maintain": Use vectors first to get the spacing, then use speed to hold it.
  • The One-Way Street: Speed control is typically a reduction (decreasing speed). Increasing speed after already assigning a slow speed is considered a controller error and poor technique.
  • Lead vs. Trail: Never speed up the lead aircraft to fix a spacing error; always slow down the trailing aircraft.

• Speed Assignment by Altitude:

  • Above $FL250$: Use Mach numbers.
  • Below $FL250$: Use Indicated Airspeed ($IAS$).
  • Common Speeds: $290\,\text{kts}$ in the high teens, $250\,\text{kts}$ (jet speed limit below $10,000\,\text{feet}$), and $210\,\text{kts}$ to $170\,\text{kts}$ on final approach.

Questions & Discussion

• Student Question: In a situation with many lateral climbers, would you coordinate a "stop and pop" with Jazz, or would they know?

  • Instructor Response: You tell them "Vectors for traffic." Once you say that, they are informed. If they see the traffic on TCAS (Traffic Collision Avoidance System) $35\,\text{miles}$ ahead, they can do the "pilot math" and adjust their power/climb rate (e.g., to $500\,\text{feet/minute}$) to make the transition smoother.

• Student Question: Regarding the diagram showing "less than minimum" distance behind a heavy—why is that?

  • Instructor Response: The distance laterally (north/south) might technically be less as a crossing track, but as they pass behind, they must still meet the categorical minimums. You protect the "6 o'clock position" of the heavier aircraft.

• Student Question: Can you clear an aircraft for a visual approach if you don't see them?

  • Instructor Response: Use caution. An anecdote involves a Navajo and an Air Canada jet; the controller cleared the jet for a visual while it was doing $230\,\text{kts}$ in the trail. The jet caught up to the Navajo, causing a massive argument about visual approach standards. Many units now won't clear visual approaches until aircraft are within a certain range or visually identified by the tower.