Title Page Prey Page Next Page TOC GULFSTREAM IV MAINTENANCE MANUAL PRESSURIZATION CONTROL SYSTEM - SYSTEM DESCRIPTION 1. Description A. General The pressurization control system operates on the outflow side of the airflow path to control the level of compartment pressurization. The Gulfstream IV pressurization system is classified as a variable isobaric, fixed differential, selective rate-of-change system. The pressurization control devices, together with associated components, control compartment pressurization by allowing air to flow at a controlled rate from the occupied areas to atmosphere through the outflow valve. Cabin altitude and ambient altitude are sensed and through automatic electronic devices, establish control over the outflow valve in accordance with predetermined programming by crew. The pressurization control system functions in the following manner: • Isobaric pressurized operation with cabin altitude as selected by crew and performed by system • Maximum pressure differential operation, where system normal control devices limit maximum cabin to ambient differential to a fixed, predetermined amount. This function is not under control of crew • Safety pressure relief operation, wherein system will prevent any further buildup of cabin to ambient differential beyond a fixed, predetermined amount, even if normal regulating (normal pressure differential) devices fail • Selective rate-of-change operation, as determined by crew, within the fixed differential limits • Vacuum (negative) pressure differential control which is a fixed value and is not under control of crew. This prevents buildup of a negative differential between cabin to ambient beyond a fixed value • Barometric correction of programmed landing field elevation by manual means • Landing field altitude preprogrammed by crew to establish descent pressurization profile • Manual control over outflow valve by crew (if desired) with visual outflow valve position i