Dec 132009
An early 1960’s flyign crane proposal, utilizing turbojets at the tips of the rotors. This would virtually eliminate torque. However, tip turbojets were always problematic due to the sideways loads imparted by the centrifugal forces.
4 Responses to “Hiller Type 1108”
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Wonder if this idea should be revisited today, with the advances in materials and lighter, more powerful engines.
When I worked doing SFX, the company built a model of a military concept of a helo that used the thrust from its turbine to duct air thru heavy composite blades with the exhaust blowing out the tip of the blade pushing the rotor forward. i think rotation was controlled be ducting some of the thust near the rear of the body, but it had no tail boom.
This person built two flying prototypes, the first was about the size of a one person gyrocopter and the second was a larger two person version. The last was a converted MD-500 and looked pretty nifty, unfortunately that version crashed and killed the designer when the rotors delaminated.
The earlier proto’s worked well. In the promo video i saw, the two rotors got up to speed on the ground and the copter could jump straight up with no hands on the stick, it was super stable. The momentum from the heavy blades spinning fast lifted it quickly. It could fly backwards and do some interesting tricks.
The IR signature was pretty low since the exhaust from the turbine was split three ways and spread thin by the rotor. i wish I could remember their names, it could probably be built today, the main problem was the composite blades and the connections to have the blades rotate like a normal helo.
Today they could use a fixed blade like that Red Bull stunt helo that can do inverted loops and rools.
If anyone remembers the Fairy Rotodyne, the eventual fate of ducted rotor or even engine tipped rotor helos is written there. Interesting idea, several advantages, but structural problems as noted by Scott plus noise enough to wake the dead three counties over. The Rotodyne’s noise problem was minimised by the fact that the tips were powered only for takeoff, the turboprops doing most of the work for that convertaplane. This design uses the tip engines all the time and they are tiny screaming turbojets to boot. I can guarantee that no-one would be staning near it with unprotected ears! 🙂
I wonder what the structural loads would be on the rotor blades in an engine out situation? Specifically the rotor with one or more engines out.
Paul
The Rotodyne flew several inter-city to inter-city test runs and her takeoff and landing loudness didn’t elicite any complantes, IIRC. It helped that the tip jets ran only a short time but I think there was a program to get the noise down going before Fairley had to fold in the face of the Socialistes Centeral Planning.
Still, I found this not to long ago, air is pumped down the rotor blades to the tip jets:
http://www.flightglobal.com/pdfarchive/view/1955/1955%20-%201478.html