What is the best practice for making major adjustments to equipment like regulators and inverters?

The best practice for making major adjustments to equipment like regulators and inverters is on test benches with necessary instruments. This approach ensures that the adjustments are made in a controlled environment where all relevant parameters can be accurately monitored and modified. Test benches are specifically designed to replicate operating conditions and provide the necessary diagnostic tools, which allow for precise tuning and testing of the equipment's performance.

By conducting adjustments on test benches, personnel can ensure that the equipment operates as intended before it is placed back into service, thereby safeguarding safety and functionality. In contrast, making adjustments in the cockpit with minimal tools can lead to incomplete or incorrect modifications, potentially putting the aircraft at risk. Making adjustments during flight or only after takeoff is not advisable, as it can create distractions and safety hazards.