Originally Posted by Groundloop
Boeing managed to get the 737NG certified as a variant of previous 737s, even with a completely new wing. If they had had to meet the latest requirements significant changes would have had to have been made to the fuselage to meet emergency exit requirements. Compare the exits on an A321 (certified under newer requirements) with those on the 737-800 and 737-900 which used old 737 "grandfather rights".
Not true. The B737-800 met the same standards as the A321 albeit not in the same way. The regulations in an attempt to permit novel or new concepts, do accept alternate means of compliance as long as there is no loss of comparitive safety. However, where new and novel design approaches are employed, such alternate means or equivalency may have to be published beforehand for public comment. This was done via the Federal register and coments for and against were recieved. After review of these coments the FAA found that the equivalent or alternate means of compliance met or exceeded the basis of the rule for the B737-800.