Short definition: ILS, or Instrument Landing System, is a radio-based approach aid that provides lateral and vertical guidance to help an aircraft align with the runway and descend safely during an instrument approach.
Detailed explanation: An ILS uses two main signals: the localiser, which guides the aircraft left and right to the runway centreline, and the glideslope, which guides it on the correct descent path. Pilots fly the published ILS procedure using cockpit instruments or an autopilot if fitted and authorised. The system is designed to support approaches in reduced visibility, but it does not remove the need to follow published minima, monitor aircraft configuration, and confirm runway environment requirements before landing. Approach charts also include associated information such as frequencies, inbound course, decision altitude or height, and missed approach instructions.
Key considerations:
- A practical limitation is that ILS performance can be affected by signal interference, terrain, or vehicles and aircraft near the aerials.
- A common mistake is failing to identify and set the correct frequency and inbound course before intercepting the approach.
- A real-world impact is that ILS allows more reliable arrivals in poor weather, which can improve safety and reduce diversions.
