How is QNE used in aviation?

In aviation, QNE (altimeter setting) refers to the pressure adjustment value used to set the barometric altimeter in aircraft to obtain the correct altitude indication relative to the elevation of the surrounding terrain. Here are the key aspects of how QNE is used in aviation:

1. Altimeter Setting: QNE is one of the two most commonly used altimeter settings, along with QNH. It is used when air traffic is operating in the terminal control area (TCA) of an airport or in close proximity to the airport.

2. Reference Level: QNE uses the elevation of the airport or the designated aerodrome reference point (ARP) as the reference level for altitude measurements. When the altimeter is set to QNE, it indicates the aircraft's altitude above the airport or ARP.

3. Barometric Pressure Adjustment: To set the altimeter to QNE, the pilot inputs the current local atmospheric pressure (QNH) as well as the elevation of the airport (QFE) into the altimeter. The altimeter then calculates the appropriate atmospheric pressure setting to display the aircraft's altitude relative to the reference point.

4. Transition from QNH to QNE: When an aircraft is approaching an airport and entering the terminal control area, ATC (Air Traffic Control) will typically issue a QNE altimeter setting. This ensures that all aircraft in the vicinity have a consistent and standardized reference point for their altitude measurements.

5. Landing and Departure: QNE is particularly important during takeoff and landing phases of a flight. By setting the altimeter to QNE, the pilot can accurately determine the aircraft's height above the runway and the terrain, ensuring a safe approach and landing.

6. Instrument Approach Procedures: QNE is used in conjunction with instrument approach procedures, allowing pilots to safely follow predetermined flight paths and descend towards the runway. The proper altimeter setting is crucial for accurate altitude indications during approaches and missed approach procedures.

7. Communication and Safety: To maintain safety and prevent collisions, all aircraft operating within the TCA must use the same altimeter setting. ATC plays a vital role in providing accurate QNE altimeter settings to pilots to ensure consistency in altitude measurements.

In summary, QNE is an essential altimeter setting used in aviation for accurate altitude measurements relative to a designated reference point, typically the airport or aerodrome reference point. It is used during takeoff, landing, instrument approaches, and when operating within the terminal control area to maintain safety and ensure standardized altitude measurements among aircraft.