That will vary by aircraft certifying authority.<p>For the FAA part 23 certified aircraft, the basics are here (for Federal laws, these are written in fairly plain English, but you need to hop around a bit at times): <a href="http:&#x2F;&#x2F;www.ecfr.gov&#x2F;cgi-bin&#x2F;retrieveECFR?n=pt14.1.23#se14.1.23_1301" rel="nofollow">http:&#x2F;&#x2F;www.ecfr.gov&#x2F;cgi-bin&#x2F;retrieveECFR?n=pt14.1.23#se14.1....</a><p>For FAA part 25 certified aircraft (transport category aircraft): <a href="http:&#x2F;&#x2F;www.ecfr.gov&#x2F;cgi-bin&#x2F;text-idx?rgn=div5;node=14%3A1.0.1.3.11#se14.1.25_1301" rel="nofollow">http:&#x2F;&#x2F;www.ecfr.gov&#x2F;cgi-bin&#x2F;text-idx?rgn=div5;node=14%3A1.0....</a>