FAR 21.618 — TSO Deviation Approval
FAR 21.618 explains how manufacturers request FAA approval to deviate from a TSO performance standard by showing an equivalent level of safety.
FAR 21.618 governs how an article manufacturer can get permission to deviate from a TSO (Technical Standard Order) performance standard. A TSO is a minimum performance specification the FAA sets for certain aircraft articles (like avionics, seats, or life vests). Sometimes a manufacturer's design can't meet a specific TSO requirement exactly — but it can still be just as safe through other means.
To get a deviation approved, the manufacturer must:
- Show equivalent safety. Other factors or design features must compensate for the standard being deviated from, providing an equivalent level of safety.
- Submit the request to the FAA with all pertinent supporting data.
- Route foreign requests through the civil aviation authority of the country or jurisdiction where the article is manufactured, which then forwards the request to the FAA.
Why it matters operationally: this rule keeps the TSO system flexible enough to allow innovation and alternative designs while ensuring the equipment installed in your aircraft still meets a safety bar equivalent to the original standard.