Comparing the Aeroflex IFR-3550R with IFR-4000: Which Radio and Nav/Comm Test Set Fits your Aviation Needs? 31 October 2025 AvionTEq Blog Compare the Aeroflex IFR-3550R and IFR-4000 aviation test sets. Discover key differences, specs, and features to choose the best Nav/Comm tester for your needs. Read more. [More] Share