Aviation Mechanic - General, Airframe, and Powerplant › II. Airframe › Task F. Hydraulic and Pneumatic Systems

AM.II.F.R5

Risk management

Compatibility between hydraulic seals and hydraulic fluids.

Study note

Get a short, cited explanation of this element written from the FAA handbooks: the core idea, the numbers that matter, common test traps, and a quick self-check.

From the FAA library

Aviation Maintenance Technician Handbook - Airframe p. 12-3
Chapter 12: Hydraulic & Pneumatic Power Systems › Types of Hydraulic Fluids › Compatibility with Aircraft Materials
compatible with the hydraulic fluid. Appropriate seals, gaskets, and hoses must be specifically designated for the type of fluid in use. Care must be taken to ensure that the components installed in the system are compatible with the fluid ... polyester, which are used extensively in most aircraft. Petroleum oil hydraulic system seals of neoprene or Buna-N are not compatible with phosphate ester-based fluids and must be replaced with seals of butyl rubber or ethylene-propylene elastomers…
Aviation Maintenance Technician Handbook - Airframe p. 12-36
Chapter 12: Hydraulic & Pneumatic Power Systems › Seals › Seal Materials
Seal Materials Most seals are made from synthetic materials that are compatible with the hydraulic fluid used. Seals used ... hydraulic fluid are not compatible with phosphate ester-based fluids and servicing the hydraulic system with the wrong fluid could result in leaks and system malfunctions. Seals for systems that use MIl-H-5606 are made of neoprene…