That not what I asked "what" about.Dennis and Tina, the autogyro is older (first flight in 1923) than helicopter (first real flight in 1936). But once the helicopter was a fact, just at the end of WWII, all the investigation efforts were directed to helicopters and the gyro was entirely forgotten. Mr. Bensen found a new application to an existing technology; by really he didn’t created anything.
Our gyro blades are not innovations, in fact the airfoil (everybody uses the same one) was developed a lot of years ago and there are not investigation and development programs in benefit of autogyros. This is a very different history from helicopters. Isn't it?
Maybe this is where your misconception is derived. You see, depending on gross weight, a tail-rotor uses 20% to 25% or even more of the power needed to hover. Not 8%. We wish it were 8%!Dennis, we are comparing helicopter versus gyro performances. Obviously the rotor tail sucks more power hovering than at cruise speed (8% versus 4%). But it still sucks a 4% of the required power in cruise. And tail rotor’s drag is bigger (much bigger) than vertical fin’s one. And helicopters have vertical fins too. But this is only part of the story.
Sure I have, that is why I design the mast to lean sideways 2.5 degrees, to compensate for tail-rotor thrust when the tail-rotor centerline of thrust is lower than the main-rotors disk. This also allows for the helicopter to take off and land level on both skids, while others have to lift off or set down on one skid then the other.Have you ever heard about inherent side slip? The tail rotor is always producing a lateral thrust, in order to compensate main rotor torque over fuselage. But you cannot compensate a torque (what main rotor is doing) with a moment (what tail rotor is doing). The undesired result is sideways translating tendency that must be compensated by tilting the main rotor. In other words, all conventional helicopters are always flying whit a side slip. And this creates more drag and reduces overall efficiency.
I'm working that out now on a new project. Looks like around 4 to 5hp.Dennis,
Thanks for sharing your experience.
How much power do you think would need to be applied directly to the gyro rotor (i.e. PPR) to achieve the same cruise efficieny as a helicopter? That is, assuming all other things being equal (weight, drag, etc.)
I'm sure it's entirely possible that you would find it hard to believe. It requires a good deal of experience to understand something as complex as a helicopter.I'm not questioning anyone's credentials, but I find it hard to believe that Dennis Fetters' statement on tail rotor power needs:
depending on gross weight, a tail-rotor uses 20% to 25% or even more of the power needed to hover
is perhaps too general. Good performance in hovering flight is a key feature of rescue helicopters, and the fact is that the conventional 'Sikorsky', i. e. main + tail rotor configuration has been used for S&R helicopters, both light and heavy ones. I find it hard to believe that S&R helicopters may need such a big fraction of its power for the tail rotor while hovering.
Perhaps there are other factors here, apart from gross weight, like boom length and tail rotor diameter.