Originally Posted by
SoulFlyer
As it is impossible to prove a negative, if someone who happens to know the FAA regulation could post a link to it, I'd love to have the knowledge and stop spreading lies.
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/b5c85ae8e38df676862571da00529da4/$FILE/AC%2091.21-1B.pdf
This appears to cover the subject.