The horizontal stabiliser tail tanks on the 747-8 are to be 'deactivated' to comply with FAA regulations. With fuel laden tail tanks, the 747-8 Intercontinental manages to excite a structural mode 'under a certain regulatory-required structural failure scenario'.
I'd love to know what kind of scenario this occurs under. I'm betting it's some sort of longitudinal manoeuvre that sets off the empennage. Guess we'll know if and when Boeing decides to reveal details from their flight test report.
From source: "The 747-8 programme has faced vibration concerns before, after a 2.3Hz limit cycle oscillation (LCO) in the wings prompted Boeing to develop the Outboard Aileron Modal Suppression (OAMS) system to dampen out vibration with the aircraft's fly-by-wire ailerons."
Original article: http://www.flightglobal.com/news/articles/boeing-locks-out-747-8-tail-fuel-tanks-on-flutter-concerns-367148/
I'd love to know what kind of scenario this occurs under. I'm betting it's some sort of longitudinal manoeuvre that sets off the empennage. Guess we'll know if and when Boeing decides to reveal details from their flight test report.
From source: "The 747-8 programme has faced vibration concerns before, after a 2.3Hz limit cycle oscillation (LCO) in the wings prompted Boeing to develop the Outboard Aileron Modal Suppression (OAMS) system to dampen out vibration with the aircraft's fly-by-wire ailerons."
Original article: http://www.flightglobal.com/news/articles/boeing-locks-out-747-8-tail-fuel-tanks-on-flutter-concerns-367148/
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