C-FXFX Posted December 21, 2007 Report Share Posted December 21, 2007 G'day to all! A few day ago i saw a photo of a 407 with no FRAHM and beanie (top hat) on the rotor head,I wonder what is the avantage (maybe less weight!). any advise on that? Guy Quote Link to comment Share on other sites More sharing options...
Jan Pluemer Posted December 21, 2007 Report Share Posted December 21, 2007 According to technical bulletin 407-03-51 the operator can remove the aerodynamic cover with the frahm damper underneath. The advantage is that you have circa 25 kilogramms more payload, but you then have more vibrations especially in the rear-cabin. I photographed this 407 in Canmore in 2005 - it had the cover removed: Merry Christmas, Jan Quote Link to comment Share on other sites More sharing options...
rainman Posted December 21, 2007 Report Share Posted December 21, 2007 Our 407 has had the frahm removed as long as I've been flying it. I've flown others with it and it's much smoother. I suppose just a weight thing. Makes me wonder if certain components don't quite make their life when it's removed? Quote Link to comment Share on other sites More sharing options...
koalaa119 Posted December 22, 2007 Report Share Posted December 22, 2007 I have seen the frahm removed in the process of balancing the a/c. It was smoother without it. Maybe an issue with the frahm but the end result was a smoother a/c without it installed. cheers Quote Link to comment Share on other sites More sharing options...
AutoMate Posted December 25, 2007 Report Share Posted December 25, 2007 Ok guys, I'll be the one to reveal my ignorance. I take it the FRAHM is a vibration absorbing device or damper, but could you enlighten me at to what the acronym actually means, and what method it uses to do it's job? thanks, and Merry Christmas AutoMate Quote Link to comment Share on other sites More sharing options...
47G Posted December 25, 2007 Report Share Posted December 25, 2007 Ok guys, I'll be the one to reveal my ignorance. I take it the FRAHM is a vibration absorbing device or damper, but could you enlighten me at to what the acronym actually means, and what method it uses to do it's job? thanks, and Merry Christmas AutoMate The FRAHM damper is named after Herman Frahm who invented tuned mass dampers. Basically you take a specific mass and tune it to vibrate in opposition to the natural frequency of a vibrating object. In addition to helicopter applications, the tuned vibration mass is used in high rise buildings to minimize the effects of vibration due to wind currents. Many of the world's high rise buildings incorporate this technology. In the case of the 407 the FRAHM is used to minimize the effect of the natural 4/rev vibration from the main rotor. That being said, each helicopter is sufficiently different that the FRAHM is not really a requirement for most. You can remove the FRAHM and if the 4/rev vibration levels are acceptable to the pilot and passengers, then it need not be installed. As mentioned it saves about 50 pounds of empty weight, not to mention removing the operating cost of the FRAHM itself. Merry Christmas to all!! Quote Link to comment Share on other sites More sharing options...
Guest Angry Egg Driver Posted December 25, 2007 Report Share Posted December 25, 2007 I've heard that its easier to track & balance the main rotor? Quote Link to comment Share on other sites More sharing options...
AutoMate Posted December 25, 2007 Report Share Posted December 25, 2007 The FRAHM damper is named after Herman Frahm who invented tuned mass dampers. Basically you take a specific mass and tune it to vibrate in opposition to the natural frequency of a vibrating object. In addition to helicopter applications, the tuned vibration mass is used in high rise buildings to minimize the effects of vibration due to wind currents. Many of the world's high rise buildings incorporate this technology. In the case of the 407 the FRAHM is used to minimize the effect of the natural 4/rev vibration from the main rotor. That being said, each helicopter is sufficiently different that the FRAHM is not really a requirement for most. You can remove the FRAHM and if the 4/rev vibration levels are acceptable to the pilot and passengers, then it need not be installed. As mentioned it saves about 50 pounds of empty weight, not to mention removing the operating cost of the FRAHM itself. Merry Christmas to all!! Many thanks 47G, I learned something new today. (Never too old !) Merry Christmas AutoMate Quote Link to comment Share on other sites More sharing options...
MEOB Posted January 6, 2008 Report Share Posted January 6, 2008 All of our 407s have the FRAHM removed. Theres a little vibe difference with it off. But then again if the engineers put the time in to strobing it they can be as smooth as glass and you wont notice it. Quote Link to comment Share on other sites More sharing options...
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