Which system can be affected by a hydraulic pump failure?

The landing gear system relies heavily on hydraulic power to function. In the CRJ550, the landing gear is deployed and retracted by hydraulic actuators, which are powered by the hydraulic pumps. Therefore, if there is a failure in the hydraulic pump, the hydraulic pressure needed to operate the landing gear system can be compromised. This failure could result in an inability to extend or retract the landing gear properly, leading to potential safety concerns during takeoff and landing.

The other systems mentioned do not depend on hydraulic power to the same extent. The electrical system operates independently via electrical power sources, the fuel system is primarily managed by mechanical and electrical controls rather than hydraulic ones, and the cabin air system utilizes air conditioning packs and pneumatic systems, which also do not rely on hydraulic function for their operation. Thus, a hydraulic pump failure directly impacts only the landing gear system among the options provided.