Please follow http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2091-67/$FILE/Chap1-2.pdf.

Please follow http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2091-67/$FILE/Chap1-2.pdf.