Flight Critical Control Valves, Military Aircraft
ARP5796
This SAE Aerospace Recommended Practice (ARP) provides guidance in the design, development, qualification test, process control and production acceptance test for flight critical control valve (FCCV) design used in military flight control servoactuators where loss of single valve control could cause a catastrophic failure resulting in death, permanent total disability, and/or financial loss exceeding a defined contractual limit. The FCCV, which is one element of a flight control actuator servo control loop, is a variable position control valve which modulates fluid into and out of the servoactuator power stage cylinders. The FCCV may be mechanically driven by either a mechanical flight control system as shown in Figure 1 or hydraulically driven from electro-hydraulic servo valve (EHSV) modulation control flow as shown in Figure 2. This type of control valve is not an EHSV or a direct drive valve (DDV). The FCCV is used in military hydraulic systems which conform to AS5440.
Rationale: Based on 5 year review, update scope (abbreviate), update references (inactive, etc.), add new seal materials, clarify shear stress calculation, identify industry documents to perform Repeatability and Reproducibility evaluation and incorporate Bob Eisenberg comments form original document review.
Formal Rationale to be used in Rev A:
AIR5796 has been updated to Revision A for the following reasons:
Additional technical information has been introduced.
The references called up in the document have been updated.
