This advisory circular (AC) describes an acceptable method to demonstrate compliance with Title 14, Code of Federal Regulations (14 CFR) §§ 23.2620(a)(1), 25.1583(b)(1), 27.1583(b)(1), 29.1583(b)(1), 33.7(b)(2), and 33.7(c)(2) regarding the requirements for the approval and use of Fuel System Icing Inhibitors (FSII) in engines and aircraft.

It does not
address aircraft-level fuel system icing effects or compliance.
2.

This advisory circular (AC) provides guidance to support the development of technical data needed to show that an engine or APU replacement part complies with the airworthiness requirements under test and computation, per Title 14, Code of Federal Regulations (14 CFR) 21.303, using the comparative test and analysis approach. This guidance also supports the development of technical data needed for major repairs performed in accordance with 14 CFR Part 43.13(b), where parts fabrication and their implementation must be accomplished “in such a manner that the condition of the aircraft engine or appliance worked on will be at least equal to its original or properly altered condition.

Although the main focus of this AC is on engine inlet probes, the methodology can also be applied toevaluate temperature probes, combined pressure and temperature probes, and static pressure probe behavior regardless of installation location.
2.