Propellers: less blades vs. more blades
Ideally, you want a two blade prop - just as a long, thin wing is more efficient, a long propeller blade is more efficient. But at some point practicality comes into play. Long blades require greater ground clearance (the 'gull wing' on the F4U Corsair was to get ground clearance without needing huge landing gear with it's big prop), long props tips go supersonic sooner (noise and loss of efficiency). Adding blades means you can deliver more power to the airstream, and go faster without supersonic tip speeds, but the shorter blades are less aero efficient and you lose efficiency due to the interaction of the additional blades as they pass through the leading blade vortices.
Modern, 'swept' blade props have lessened the penalty of additional blades, but you can't eliminate physics.
I've found it personally interesting that wind turbines have pretty much settled on a three blade configuration. With wind, I figured more blades the better since you're not as concerned with efficiency as much as over all power absorption - but apparently the additional cost and weight of more blades offsets any power increase from adding more prop blades.
Modern, 'swept' blade props have lessened the penalty of additional blades, but you can't eliminate physics.
I've found it personally interesting that wind turbines have pretty much settled on a three blade configuration. With wind, I figured more blades the better since you're not as concerned with efficiency as much as over all power absorption - but apparently the additional cost and weight of more blades offsets any power increase from adding more prop blades.
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But at some point practicality comes into play!
Td, I think You summed up Aviation Design in a short and sweet sentence!
May I use it in the future?
Not that that has ever stopped the USSR. I think they have the record on power and propeller complexity. The Tupolev Bear comes to mind. An engineering delight, I am sure.
Long time since I did props, but the sound of a C185 with 300hp and standard two blade as it takes of , makes a wonderful sound as it passes abeam.
Tips chasing M1.
I also had the pleasure of flying nr 29 Beech 200 with pod and standard 3 blade. The fastest in the fleet and a delight to land. An old rented Ken Borek machine.
The 4 bladed was less forgiving in the flare if you thought you had a 3 blade, the drag was about twice.
The 6 bladed Dornier 328 was rather quiet in the cabin for a high wing, one of its selling points.
Anyway
Back to my 30% Jet with 24 blades, fixed pitch. ( CFM 56)
Regards
Cpt B
May I use it in the future?
Not that that has ever stopped the USSR. I think they have the record on power and propeller complexity. The Tupolev Bear comes to mind. An engineering delight, I am sure.
Long time since I did props, but the sound of a C185 with 300hp and standard two blade as it takes of , makes a wonderful sound as it passes abeam.
Tips chasing M1.
I also had the pleasure of flying nr 29 Beech 200 with pod and standard 3 blade. The fastest in the fleet and a delight to land. An old rented Ken Borek machine.
The 4 bladed was less forgiving in the flare if you thought you had a 3 blade, the drag was about twice.
The 6 bladed Dornier 328 was rather quiet in the cabin for a high wing, one of its selling points.
Anyway
Back to my 30% Jet with 24 blades, fixed pitch. ( CFM 56)
Regards
Cpt B
Back to subject, the model blades operate in a sonic tip velocity frequently, and more or less only the Thunder Screech did that on full scale. Almost all blades have some normal shock formation in flight, but oblique shocks are avoided where possible by limiting tip velocity. Sweep reduced the normal shock intensity...
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From MT....
Looks like reduced noise is a significant benefit:
World's first 7-bladed Quiet Fan Jet Aircraft Propeller MTV-47 is now supplemental type certified by EASA STC 10014953 R3 on the Pilatus PC-12 powered by a Pratt & Whitney PT6A-() propeller turbine.
The installation of the 7-blade MTV-47 on the Pilatus PC-12 reduces Ground roll distance by approx. 10% and Take-off distance over 50 ft obstacle by approx. 15%. It reduces also the inside and outside noise significant and complies with the strict German Noise regulations.
5 balded prop:
Looks like reduced noise is a significant benefit:
World's first 7-bladed Quiet Fan Jet Aircraft Propeller MTV-47 is now supplemental type certified by EASA STC 10014953 R3 on the Pilatus PC-12 powered by a Pratt & Whitney PT6A-() propeller turbine.
The installation of the 7-blade MTV-47 on the Pilatus PC-12 reduces Ground roll distance by approx. 10% and Take-off distance over 50 ft obstacle by approx. 15%. It reduces also the inside and outside noise significant and complies with the strict German Noise regulations.
5 balded prop:
- Applicable Aircraft: Quest Aircraft Design LLC Kodiak 100 Series
- Engines: Pratt & Whitney PT6A-34 Engine
- Best vibration damping characteristics for almost vibration free propeller operations!
- Bonded on nickel alloy leading edge for superior erosion protection of the blades!
- Take-Off improvement by 20%!
- No propeller speed restrictions on ground while operating in low idle!
- Unlimited blade life and FOD repairable blades!
- More ground clearance = less FODs!
- Lower ITTs during start-up for less engine wear!
- Unbeatable esthetic ramp appeal!
- Significant cabin noise [up to 5 dB(A)]and vibration reduction!
- Comply with the strict German noise regulations 2010 - „Landeplatz Lärmschutz Verordnung“ for unrestricted airport operation in Germany and other European Countries!
- Max. RPM reduction to 2000 RPM with increased torque for 750 shp!