What happens to the aircraft upon losing PRGB oil pressure?

When the aircraft loses pressure in the Power Reduction Gearbox (PRGB) oil system, the correct outcome is that the Engine Loss System (ELS) activates. The ELS is an important safety feature designed to respond to critical issues within the engine systems, specifically to prevent damage from insufficient lubrication. Upon detecting low oil pressure, the ELS activates to safeguard the engine and transmission systems from potential failure, which could be catastrophic.

This automatic response helps ensure that the crew receives vital operational warnings, allowing them to take appropriate action to manage the situation and maintain control of the aircraft. The ELS may engage systems to reduce engine load or alter engine settings to minimize the risk of failure, thus prioritizing safety in flight operations.

In contrast, the other choices do not accurately represent the function of the aircraft systems in response to PRGB oil pressure loss. Ignoring the fault would be dangerous, immediate failure of the primary system is unlikely unless conditions worsen significantly, and continuing operation without a fault response would undermine safety protocols.