M-T Propellers says its 11-bladed design delivers increased thrust with “an impressive noise and sound signature.” The German propmaker says it put the turbine-like device on a Piper Cheyenne fitted with P&W PT6A-135A engines and flew it a couple of months ago. “The very promising results in static thrust, 15% increase over the standard certified 5-bladed propeller, and the jet-noise signature showed another time what could be possible in the propeller developments,” the company said in a statement. Hear that “jet-noise signature” in the company video.
It seems unlikely the prop will be offered as an STC on existing aircraft, however. “The propeller system, combined with a low RPM power supply from a turbine or an electric engine, opens new possibilities for performance, efficiency, and noise,” the company said.
If you didn’t have the video, I would have sworn it was a Photoshopped image for April Fool’s Day.
We are getting closer to the unducted fan concept.
Because 12 blades would have been overkill.
That was the funniest post all year. Now let me clean the cofee off my screen! Thanks for the laugh.
More details: “… The 11-blade prop is recommended to be installed on one engine only, due to the necessity of replumbing that side’s wing tank for deicer.”
well…I listened to the company video, obviously recorded on a cell phone, and while there was turbine noise, I didn’t hear any prop noise! Maybe they’re onto something here!
Bought a Hartzell 3 blade Top-Prop for my 182. Hartzell factory rep said it’s about all they sell for 182’s, and if they made a 5 blade he said they wouldn’t be able to make enough of them. :7)
Funny when thinking back and some planes had a 1 blade prop. Look it up.
True story about the one blade prop. Some years ago at my airport west of OSH, some guy trailered in an old Cub from WA to assemble then fly into the show. It had one of those single bladed props but he wasn’t planning on flying it with it. I told him that he should take it and the tools to install it after he took it to Airventure where he’d wind up wowing the crowd. Instead, he just displayed it. It was supposed to be MORE efficient but — in practice wasn’t. In place of a second blade, it had a stubby lead weight. It was certificated for the 40hp and 65hp engines. It was made by Everel. I think PB needs one.
BITD the fastest racing line control model airplanes used 1 blade props.
Makes me dizzy remembering them!
Ok, higher static thrust and lower noise. What about cruise fuel efficiency? That’s a lot of prop blade tips, no?
Not a problem; you simply trim the blade tips off.
LOL!
Now imagine the cost of a prop strike or repair !
If repair of a two bladed prop is enough to cause a heart attack, repair of this thing would cause a world-wide depression.
… or it could drive the economy of a medium sized town. 😉
This prop goes to 11!
Extra credit for the Spinal Tap reference.
Matt C.
… or it could drive the economy of a medium sized town.
And just where would you put it? Jiffy Lube? “Get your oil changed and a prop wash”?
I would hate to be the one flying this on an airplane without an auto feather system when an engine quits. The amount of drag created with 11 unfeathered blades would be interesting.
Agreed. I have limited experience with constant speed props, but my Pitts had a 2 blade MT on it when I bought it. Even with just two blades, it was like hitting a wall when I pulled the power back on downwind, compared to a fixed pitch prop on the same airframe.
For efficiency, isn’t it still the case that the fewer blades, the better? If so, this design surely only has limited applications.
Few, or even a single, blades has less tip effects (induced drag) than more blades (raw count of blade #). This would make a single blade of infinite length more “efficient” from an induced drag perspective. But there is more to propeller disc efficiency than just minimizing induced drag. The blades have weight, and the longer the blade, the more it has to weigh to support the extra length. The propeller also has to trade off length with Mach effects at the tips. The propeller has to trade off the change in profile from the hub (low speed) to the tip (high speed) – the shape has to be rigid enough to not deform under flight loads. The blades also have to be short enough (or mounted high enough) not to hit the ground or the aircraft.
Think of that 11-blade prop as the turboprop answer to a turbofan’s fan section – they are trying to transfer the maximum amount of energy into the air around the disc of the propeller’s existing sweep.
There have been a few articles about these MT propellers in some german aviation magazines.
According to these more blades make sense if you can reduce prop speed. Around 1700 to 2000 rpm for a turbine engine. Piston engines operating at around 2500 to 2700 rpm are to fast for more blades.
There is an MT 7 blade propeller certified for the Pilatus PC-12. I have seen one landing and it was amazingly quiet. MT claims a reduction in cabin noise by more than half and shortened take off roll.
The 11 blade prop is supposed to increase static thrust by 15% and decrease noise even more. Part of it is also a reduction in diameter which will lead to even lower tip speed.
Single blade props have high efficiency because the blade runs mostly in undisturbed air and not in the vortex of the other blade(s). There are a few in use on powered gliders with retractable engines, where they reduce required space for the engine+prop box in the fuselage. Single blade propellers are counter balanced by a weight and have an articulating mount to remove bending moment on the drive shaft. Imagine a Bell 206 rotor with one blade cut off and replaced by a weight.