The DFC rotorhead - just for looks?
The DFC heads must be one of the most debated topics this year. How come? I guess there are a lot of self-claimed engineers out there not being able to tell the difference between theory and real life experiences. So what is the story behind this “new” type of rotor heads? I first heard of them a few years ago when I was on the Compass team. Sebastian Zanjons was the designer to first (at least in the past years, maybe they been used during the 90´s) to give the design a try. He used flexible rods made of delrin to allow some flex. Nobody really said any bad things about them. I got a DFC head on my 6HV and never really saw any bad things. We used the same dampeners as with traditional FBL heads. Sometimes I had some wobbles during spool down but it could be fixed with loosening the blades and make them sit loose in the grips. All Compass pilots used this head and they flew them the various head speeds without any boom strikes and bad flight tendencies. In the beginning of 2012 Align released their DFC head witch was an upgrade for their existing head. Two bad things have to mention. The screws was in the beginning was made of too soft metal and easily got bent. They addressed the issue and shipped stronger bolts to all shops. The other thing was that a lot of pilots tried to fly the DFC head with traditional rubber dampeners. The whole idea with Aligns DFC head is that no flex should be allowed in the head. Because of the fact that they used the wrong dampeners some pilots reported that they had boom strikes. But after bolts been upgraded and the super hard dampeners was installed no more reports of mishaps was to seen on the message boards. A few months later SAB released their Goblin. The helicopter gain a lot of popularity and many picked one up. And shortly after the model was released plenty of boom strikes was showing on forums all over the world. Bert Kammerer made a YouTube video and addressed the problem. His advised was to use some tape on the boomblock to get the correct clearance between the blades and the boom. I have no idea if this was the fix for their problem, but the discussion started. Most of the pilots suffering from boom strikes claimed the problem was the design of the DFC head. The boards where flooded with loudly debates about how bad this design was. Then SAB released their 630 version of the Goblin and once again the boards got filled with reports about oscillations when using normal head speed, only super high head speed solved this problem. And the DFC head design was once the thing to blame. They released the HPS (high precision system) to allow pilots to use lower headspeed. The all the Goblin pilots where all happy and cheering that the DFC era was over!
The one thing I find very ironic is that during this year when all this debates has been the hot topic, Align and Compass pilots has been flying the shit out of their helicopters at all kind of head speeds. If you talk to Compass pilots and ask them if they have a lot of problems with boom strike I´m sure no one will answer yes. Ask pilots with Align helicopters if they can´t fly with low head speed without wobble?
My reflections regarding the DFC head is that is such a shame that all companies get a bad name because a few brands have problems. I have been flying my TREX 700 DFC V3 for more than 150 fights without a single issue. No wobbles, no parts been worn out and no boom strikes. And to be honest, with the low and stiff head which DFC is I got an amazingly connected feeling. I prefer this design over traditional one and wouldn´t stop use it no matter how much chatter it is on the message boards. So to all of you skeptical ones, holla at me at any fun fly or competition next year and you can try my helicopter. Fly it as hard as you like and if you boom strike it I will eat my words. I know DFC stands for Direct Flight Control, but to me it´s more Don´t Fucking Care…