How are the hydraulic systems designated in the B737?

The hydraulic systems in the Boeing 737 are designated as A, B, and standby to facilitate systematic identification and management of the hydraulic functions throughout the aircraft. The primary systems, A and B, are used for critical flight controls and other essential aircraft operations. Having a specific designation allows maintenance personnel and pilots to effectively communicate about which system they are addressing or troubleshooting.

The standby system serves as a backup to ensure that in the event of a failure in either the A or B system, there is still hydraulic power available to maintain control of the aircraft. This clear designation helps in operational safety, allowing crew members to quickly understand which system is functioning normally and which might need attention in case of abnormalities.

Other designations like primary, secondary, and backup or main, auxiliary, and standby may suggest a hierarchy or function that doesn't precisely reflect the actual configurations of the hydraulic systems in the B737, leading to potential confusion during operations or maintenance discussions.