How is the main gear emergency extension operated during a hydraulic system failure?

The correct method for operating the main gear emergency extension during a hydraulic system failure is through a handcrank manual driver system. In the event of a hydraulic failure, the use of a manual method allows crew members to extend the landing gear without relying on the primary hydraulic system, which is crucial for safety in emergency situations.

The handcrank system provides a direct mechanical means of extending the gear, ensuring that pilots can manage the extension process even if hydraulic pressure is lost. This approach offers a reliable backup solution to maintain control over the aircraft's landing gear—vital for a successful landing.

In contrast, while other methods like using an auxiliary power source or a backup electronic controller might be applicable in different systems, they do not provide the same level of immediate mechanical response as a handcrank does. Automatic systems could fail to engage in emergencies, whereas the manual system is designed specifically to operate when other methods are unavailable.