Ok, thanks for the information. Appreciate the insight from someone in the industry. BLTA might fall under this regarding the engines what do you think?: C. Materially Altered Airplane. Applicants must conduct at least 50 hours of proving tests when the type of aircraft to be used has been materially altered in design. Examples of materially altering an aircraft design include: · Installation of engines that are a different type from those originally installed on the aircraft for type certification (for example, reciprocating powered engines to turbine powered engines, or low bypass jet engines to high bypass jet engines), or · Any design alterations that significantly affect flight characteristics, (principal operations inspectors (POI) may contact the appropriate certification directorate). http://fsims.faa.gov/wdocs/8900.1/v03%20tech%20admin/chapter%2029/03_029_003.htm