Loss of power.

Hi, I have two novice questions. - What happens in the event of loss of power or an engine stall when the boom is extended. We rented 600AL. How does hydraulic system maintain pressure and/or would bring platform down? - On the platform, when operator selects tower telescope and jib, i noticed there was considerably delay about 3 to 7 seconds every time before hydraulic extended. Is that expected? thank you