Air Law

• The transition altitude is the altitude at or below which aircraft use the local QNH setting. Above this point, they switch to standard pressure (1013.25 hPa or 29.92 inHg).
  → It is used during climb.
  → It is fixed for each airport (e.g. always 18,000 ft in the US and Canada).

• The transition level is the lowest usable flight level at or above which aircraft operate on standard pressure. Below this point, they must use the local QNH setting.
  → It is used during descent.
  → It usually varies depending on the current QNH, but may be fixed at some airports.

• The airspace between the transition altitude and the transition level is called the transition layer.

Note: Level flight is not permitted within the transition layer.
For example, if the transition altitude is 5000 ft and the transition level is FL070, an aircraft would not be cleared to maintain FL060 or 6,000 ft within that layer.

Aircraft approach categories are based on the aircraft’s V_AT, which is the indicated airspeed at threshold.
Vat is defined as 1.3 × V_SREF (stalling speed in landing configuration) at the maximum certified landing weight.

The 5 categories are:

Note: These categories are used to determine approach minima, obstacle clearance requirements, and procedure design.

The number of stripes painted at the runway threshold provides a visual indication of the runway width:

Note:
Each white stripe is 3.75 meters wide.
This method allows pilots to quickly assess runway width, especially at unfamiliar airports.

The ICAO maximum holding speeds depend on the holding altitude and aircraft category:

Note: These are standard ICAO limits. Local procedures or ATC instructions may specify lower values.

ICAO wake turbulence categories are based on an aircraft’s Maximum Certified Takeoff Weight (MTOW) and are used by ATC to apply appropriate separation minima to mitigate wake turbulence risk.

Note:

• The “Super” category is not based solely on MTOW, but on ICAO designation found in Doc 8643.
• Wake turbulence categories are filed in the ICAO flight plan (Item 9) using the codes J, H, M, or L.

The ICAO airspace classes (A to G) determine the level of ATC services, separation, and communication requirements provided to aircraft.

Summary of services by airspace class:

Notes:

• Separation = active ATC responsibility to maintain distance between aircraft.
• Traffic information = ATC provides position info, but separation is not ensured.
• Classes F and G are uncontrolled airspace.

Important: The exact usage of each class may vary depending on the state’s AIP.