Fail-Operational Automatic Landing System:

A fail-operational automatic landing system ensures that if part of the system fails during landing, the remaining components can still guide the aircraft safely through the approach, flare, and landing phases automatically. It’s like having a backup plan in place to ensure a smooth touchdown even if something goes wrong with the automated landing process.

This status is displayed as LAND 3 for Boeing aircrafts and CAT 3 DUAL for Airbus.

Fail-Passive Automatic Landing System:

In contrast, a fail-passive automatic landing system ensures that even if a failure occurs, there won’t be any significant deviations in the aircraft’s trim, flight path, or attitude. However, unlike the fail-operational system, it won’t be able to complete the landing automatically. Instead, it alerts the pilot to take over manually to ensure a safe landing.

This status is displayed as LAND 2 for Boeing aircrafts and CAT 3 SINGLE for Airbus.

Fail-Operational Hybrid Landing System:

A fail-operation hybrid landing system is designed with two main components: a primary fail-passive automatic landing system and a secondary independent guidance system.

The primary system, known as fail-passive automatic landing, ensures that in the event of a failure, there won’t be any significant deviations in the aircraft’s trim, flight path, or attitude. However, it does not complete the landing automatically.

The secondary guidance system acts as a backup, providing the pilot with independent guidance to complete the landing manually if the primary system fails. This dual-system setup offers redundancy and enhances safety by allowing the pilot to take over control and safely land the aircraft even if the primary system encounters issues.

Note. — A fail-operational hybrid landing system may consist of a fail-passive automatic landing system with a monitored head-up display which provides guidance to enable the
pilot to complete the landing manually after failure of the automatic landing system.