technical standard order
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technical standard order (TSO)
A standard established by the U.S. FAA (United States Federal Aviation Administration) for outlining technical specifications in avionics, instruments, and other airborne equipment. If it complies, equipment is said to be “TSO'd” and is more expensive than similar non-TSO equipment. Original installed equipment may not be replaced by non-TSO equipment, nor may commercial operators use non-TSO equipment for minimum requirements.