Final answer:
If hydraulic pressure is lost in flights, there could be indications such as a loss of functionality in flight control systems or difficulties in braking. Modern aircraft often have backup systems to mitigate the effects of pressure loss.
Step-by-step explanation:
If hydraulic pressure is lost in flights, there could be a number of indications which may depend on the specific aircraft system. One indication could be a loss of power or functionality in certain flight control systems. For example, if hydraulic pressure is lost in the landing gear system, the landing gear may not be able to be deployed or retracted properly. Another indication could be a loss of power or responsiveness in the aircraft's brakes, leading to difficulties in slowing down or stopping the aircraft.
It is important to note that in modern aircraft, hydraulic systems are often redundantly designed and have backup systems in place to ensure safety in the event of pressure loss. These backup systems might include alternative hydraulic sources, such as auxiliary power units or accumulators, or even manual backup systems that can be activated by the pilot.