What computer controls the outflow valve?

The correct choice for identifying which computer controls the outflow valve is the IASC, or Integrated Airborne Systems Controller. This system is crucial because it manages various aircraft systems, including environmental controls and pressurization. The outflow valve is an essential component of an aircraft's pressurization system, as it regulates cabin pressure by allowing or restricting the escape of air from the pressurized cabin.

The IASC’s role in controlling the outflow valve ensures that the cabin pressure is maintained at a safe and comfortable level for passengers and crew, especially during different phases of flight, such as ascent and descent. By effectively managing the outflow valve, the IASC helps maintain the aircraft's overall safety and operational efficiency.

Other options like FMS (Flight Management System), GCS (Ground Control Station), and ATS (Air Traffic Services) handle different functions in aviation operations. For instance, the FMS focuses on navigation and flight planning, the GCS is more involved with controlling unmanned aerial systems from the ground, and ATS is centered around the management of air traffic. Therefore, while these systems play critical roles in aviation, they do not directly control the outflow valve, which is why IASC is the correct choice.