4 Biggest Propeller Myths Explored - Long v Short & 2 v 3 Blade

[@LetsGoAviate]

Single Blade Propeller Explained : kzbin.info/www/bejne/o6qahqV-aLtrgaM Propeller Effects on an Aircraft : kzbin.info/www/bejne/jZ-tqaV-otmHlcU The Only Video Needed to Understand Airplane Propellers : kzbin.info/www/bejne/nqfFoJxsrJaNb6M

[@Vmaxfodder]

Now do court nozzles!

[@markwhittington5020]

Most impressive. Thank you for the detailed presentation. I worked as an Aerospace Engineer for over 31 years and never have seen all these issues presented so concisely in one presentation.

[@vladkudrya9615]

The more blades, the safer it is in case of loss of one of the blades. when you have two blades and lose one, you will no longer be able to continue flying, and if you have three blades and you lose one, then you will be able to continue flying with limitations. for this reason you will not see two blades on civil and military transport aircraft.

[@MrSpikebender]

I build and fly Quadcopters. This is a topic than none of the Drone related channels cover. So thank you most of my propeller questions are answered.

[@makantahi3731]

the max revolutions of the propeller (280m/s) must match the revolutions of the max power of the engine, then you can combine the pitch and the number of blades, more blades less pitch and vice versa

[@LightRealms]

Phenomenal video, I've never seen anyone discuss propellers so well!

[@Cletrac305]

The Corsair and P47 originally had 3 bladed narrow blade props. It was said that going to the 4 bladed "paddle prop" was like adding 1,000 hp in a climb! One pilot in Britan said that his P47 was faster and would tangle well with spitfires untill they pulled up and climbed they always did this to him in mock dogfights until his plane got the 4 blade paddle prop and water injection, at which point he pulled up with them and passed them blowing their minds!

[@vascoribeiro69]

P-47 always had four blade props unlike the Corsair. But, later versions had more power and got paddle blade propellers increasing their performance in the climb.

[@judydupont5601]

@@vascoribeiro69 thank you for that comment.

[@331SVTCobra]

Did you read Juggernaut, by Robert Johnson?

[@331SVTCobra]

@@vascoribeiro69 I always wondered about the German propellers being smaller diameter and much larger chord that allied aircraft. (The propellers of the FW 190 and Me 264, for example)

[@vascoribeiro69]

@@331SVTCobra yes, they had a lower aspect ratio. I don't know the reasons or trade offs. I think they stuck with three blade propellers for some reason (productivity?) and, with increasing engine power, they just augmented the blade area. We can discuss blade drag, but they were very well designed, being elliptical, thus reducing induced drag.

[@smacfe]

Fantastic explanation. Most people get three bladed props because "they look cool". I just put a new 2 blade prop on my TR182 because it is just flat out faster with the 2 blade prop. If you maintain the prop as well as you should, the 2 blade will be every bit as smooth as the 3 blade prop as well. Just an aside, in the old days, model airplanes used to use one bladed props with a counterweight as they were even more efficient.

[@jonahloughren9067]

There’s a few J3 cubs still out there with one bladed props too! Performs noticeably better than a two blade

[@jubuttib]

You'd think the thrust imbalance would cause issues on a one-bladed prop... =/

[@grafhilgenhurst9717]

If you buy a Cirrus SR-22, you can order a 4 bladed prop as an option (standard is 3 blades). It's a $22,000 option, but it looks great!

[@kevwills858]

Ive never seen a one blade prop .. a strange concept/mind indeed 😄

[@billwendell6886]

Fun facts 1. The Wright Brothers' real innovation was realizing a propellor blade was a wing turning in a circle. They were the only ones getting full efficiency from the engine. 2. An early misconception was that multi bladed props would aerodynamically interfere with each other.

[@LetsGoAviate]

☝️

[@senseisecurityschool9337]

That's not entirely a misconception, because drag exists. In a world with no drag and spherical cows, where the aircraft is not accelerating, they wouldn't interfere.

[@WardenWolf]

It's not much of a thought stretch in the modern world to think that if you invert a ramp and drag it forwards by the tip fast enough it'll levitate. The simplest wing is literally just an upside-down ramp that's having forward thrust applied to it in such an angle that it ramps itself up in the airflow. The electric fan was invented just over 20 years before the first flight, so the basics of propellers were already known, at least. The biggest challenge was getting an engine with a sufficient power-to-weight ratio, as early engines were rather weak.

[@bbgun061]

The Wright Brothers had other innovations too. They were the first to use a wind tunnel to test airfoil designs. They developed the first system to control their airplane in all 3 axes.

[@voornaam3191]

Ehm, not interfere? Okay, not many pilots do a tail slide. That means, flying up vertically, until the plane comes to a fool stop and.... starts falling down, tail first. At that moment of hanging still, you bet the prop blades get into each others wash. But again, this is aerobatics. And a dangerous one too, you can break the rudder. Do not try this at home. This is KZbin, it's loaded with crash video's.

[@nickcaci7238]

Genius, well explained. So glad you didn’t mix it up on this tutorial with the additional engineering of variable pitch pitch props

[@gendaminoru3195]

or scimitar prop tips, or Q-tips

[@AtomicKepler]

You actually explain this stuff so well!!!

[@RizVPeter]

Excellent explanation!

[@duanewood2329]

Great video. Thank you. I owned a Comanche 250. I replaced the Hartzell 2 blade with a McCauley 3 blade. A friend replaced his original 2 blade Hartzel with a compact hub Hartzell 2 blade at considerably more expense. He claimed his would be faster than mine so I challenged him to a comparison. So at 4500 ft, we both fire walled the throttle and prop controls. I walked away from him by several knots. Haha, faster and several thousand dollars cheaper. As a side note, my takeoff roll was considerably shorter and the engine/prop combo much smoother but my power off glide suffered considerably due to the extra drag. All in all, the 3 blade was a great improvement.

[@wingmanjim6]

EXCELLENT presentation ! Thank you, sir !

[@mr.frederickson329]

I like this video. VERY informative.

[@w.peterroberts9624]

What a terrific video. Reinforces that aero engineers are smart! Thanks.

[@vincentrobinette1507]

You missed an important example, The P-51 mustang. They used propellers with 4 very long blades, driven by enormous V-12 cylinder liquid cooled engines. They were arguably the fastest open-propeller planes ever made.

[@hifinsword]

At the 3:45 mark of the video I agree the same length blade on a 3-blade or 2-blade prop would create the same amount of noise PER BLADE. So wouldn't 3 blades creating the same amount of noise PER BLADE, be 50% louder than the 2-blade prop? IOW doesn't each blade produce its own equal amount of noise?

[@Pekopekope]

The volume is generated at the same amplitude per blade but at a higher frequency. You would perceive it as being higher pitched and depending on your hearing that could be louder or quieter

[@foreverpinkf.7603]

Very interesting and well explained. Thank you very much.

[@malcolmmarzo2461]

Excellent presentation and content.

[@TexasEngineer]

Years ago my father purchased an airboat from a NASA engineer. It had a 6 cylinder Corvair engine. My father and I were both engineers and my father was a WW II B25 bomber pilot. The airboat would do 40+ mph at 4000 rpm. We wondered if the boat had the correct prop. We looked up the engine specs, 140 hp at 4200 rpm and measured the prop diameter. We calculated the speed of sound at sea level, about 1100 ft/sec. We calculated the prop tip speed, just under the speed of sound. We concluded the NASA engineer had selected a good prop for the boat. It would require a major engine and prop change to get the boat to go 50 mph. The flat bottom John boat was not built for the job. After a few years, a weld cracked on the front of the boat from the pounding of the water. Conclusion, the engine and prop were very noisy and care was needed leaving and returning to shore not to disturb others.

[@TexasEngineer]

@bidenisasnake9932 Boats also have a hull speed and maximum engine power, which we had exceeded. They are also worthless in choppy water that rips the welds apart. Don’t overload with ice and beer and throw back the large hammerhead sharks. But they are a lot of fun flying on glass smooth water at 40+mph in 6” deep water that no other boat can go. To go where no man has gone before.

[@eprops]

A video that clearly explains propellers, well done ! 😀

[@yl9154]

Excellent presentation, as usual. But the cat in the background steals the show!

[@zap5936]

25 years ago, I did a lot of Test flying of Piper Lance's with Lycoming IO-540 300 horsepower. With all sorts of different speed mods. The 2 bladed propellers consistently had shorter Take off runs and higher top speeds. 3 bladed propellers were always smoother. I always get a laugh when I read or see Propeller companies selling 3 bladed propellers With all sorts of faults claims. Great video!

[@GryffieTube]

The T-6 makes such a beautiful noise! I did a photo assignment at CFS Dunnotar once and flew in Harvard 7111. Thanks for the great video and the trip down memory lane! Liked and subscribed, please keep 'em coming! :)

[@flyfaen1]

But the most important part is having "constant speed" propellers for high speed, so the blade angle always remains at the optimal angle regardless of airspeed, and enough torque (and thus power) to overcome the ever-increasing drag in addition to the trust-vector (the "lever-arm") of the blades shortening up fast as the blade angles moves past 50° angle. The fastest mass produced prop (sustained high speed) is the old Tu-95 "bear", nearly cruising at the same speed as your typical domestic jet. But it does infact have huge diameter propellers (nearly 6m / 20ft) and fairly skinny blades, but they are also contra-rotating in addition to being constant speed. Contra-rotating is also what gives it a bit of an "edge" as the main job of the rear-most propeller of the contra-rotating pair, is to recupe and straighten the induced swirl of the main propeller, and ad a bit more velocity to the core stream as to narrowing the cone of the slipstream, conserving even more of the imparted thrust.

[@Pootycat8359]

Here's an interesting phenomenon that anyone who has flown little airplanes, or hung out in hangers that contain them, knows. That "buzzing" sound that an airplane makes when it flies overhead isn't heard, when you're up close. A Cessna 150/152 is a good example. If you're next to it, or in the cockpit, the propellor makes a "whooshing" sound, like a window fan. The high/low pressure cycles that constitute a sound apparently only form, some distance away. Little airplanes aren't necessarily quiet, up close, though. I had a T-Craft BC-12D, which lacked a muffler, and its little 65 HP Continental roared like a big semi-truck, climbing a steep grade!

[@dukecraig2402]

Fly in a sail plane, they're real quiet, that was probably the most thrilling and unique flight of my life.

[@madmarkstoys]

Awesome information

[@johnmarkey4862]

Very well made

[@thomasward4505]

It would be very helpful for us non-engineer types to have a conclusion at the end with maybe a chart that shows the basics that you went over

[@Damorann]

As an engineer in a completely unrelated field, I love that the typical way to debunk simplistic claims is always boiled down to the same concept : the more you optimize one item, the more you compromise another, which means you have to BALANCE your specs out to meet all the requirements.

[@speedomars]

What about pushers? there is no prop slipstream drag. what size blade should they have?

[@makantahi3731]

a similar situation because the turbulence from the fuselage(boundary layer) affects the operation of the propeller, which does not capture clean air, and it is better if the propeller is larger in order to capture as much clean air as possible

[@speedomars]

@@makantahi3731 In the case of the Avanti Piaggio and the Velocity XL the fuselage is pod like and both prop planes. In the case of the Simitar four bladed (shorter blades) velocity I have seen, it cruise at 240kts at 12k feet with a 310hp Continental. I know of no tractor configured single engined prop plane that can come close to that in cruise.

[@makantahi3731]

@@speedomars regardless of the fact that you have found exceptional airplanes that are well designed, the principle is the same, only with a smaller impact, as it would be with an airplane with a pulling propeller, where the fuselage is very narrow and aerodynamic

[@neurofiedyamato8763]

While I didn't believe in these myths, it was still immensely educational and easy to understand so I really appreciate it and will be subscribing.

[@user3141592635]

When I started glow engines as a kid, I learned that all propellers could mess up my fingers, so my father gave a starter-motor, so I could continue to play the piano :)

[@markpacey1009]

thank you. Very well explained

[@skycop56]

I fly a Vans RV6 with a Hartzell CS prop and a Lycoming O-360. I like to cruise with the prop at 1800 rpm and manifold pressure at 22”. IAS is about 125krs and fuel flow about 5.8 gph. Very efficient. Less engine wear with lower friction and more time for complete combustion. Engine temps are lower. Noise is lower too.

[@raywhitehead730]

Very sensible. And intelligent.

[@feman43]

Nicely done. Most people really don't understand propellers.

[@annelavrand390]

Very interesting video. Thank you !

[@KO-pk7df]

Thanks for this video getting out there. I can't remember how many times I've tried to explain things like this. I think people get something in their head and they just don't like someone bringing math and facts to replace it with new or better information. Often, I start off by stating that almost everything in this world is not 1:1 then try to correct them with nonlinear thought.

[@Coops777]

Thankyou!! So interesting!

[@Thunderchops1984]

This is very information dense and requires further study! Thanks for the informative lecture.

[@John-ih2bx]

Great information. Thank you.

[@skitairone]

Excellent explanations and graphics! I would love for you to make a video killing the myth that a fixed pitch windmilling propeller creates more drag than the same propeller on a stopped engine. Airflow thru a propeller creates drag and torque. With a lower (negative) angle of attack the windmilling propeller has less aerodynamic drag while producing enough torque to overcome the friction and compression in the engine. When airflow decreases enough that torque can’t turn the engine, both propeller and engine stop. The relative wind thru the stopped propeller becomes equal to the flight path, and the angle of attack thru the stopped propeller increases drag without generating enough torque to turn the engine. The (inversely) stalled prop has more drag than the windmilling prop, and that drag increases geometrically as the pilot accelerates back to best glide speed. The effect of this increased aerodynamic drag thru a stalled/stopped propeller has been demonstrated many times. Yet I still hear people advocate the dangerous practice of slowing down enough to stop the propeller, because they believe energy used to turn the motor decreases their glide distance, when in fact it decreases glide performance. I think that you could do an excellent job of explaining that to people who might be inclined to test the theory, or not accept the data that shows that the practice makes their glide worse.

[@fabiofarias5334]

Very good explanation, thank you,

[@kibrickj]

More on propeller theory!!! Fantastic

[@rokuth]

A few things to mention - 1] The P-47D propeller diameter actually increased in later production aircraft, and went to paddle-blades to improve the aircraft's performance. The propeller manufacturer also changed going from Curtis Electric to the larger diameter Hamilton Standard propellers. 2] On the F4U Corsair, it was design choices. True that they used a 13ft 4in 3 bladed diameter propeller, but in use, they found that the shorter landing gear made the fighter bounce too much when landing on the carrier decks. The oleos had to be modified to reduce this effect. By comparison, the contemporary F6F Hellcat, with the same engine as the Corsair, used a 13ft 1in 3 bladed propeller. It was a mid-wing design with long landing gear that actually allowed the Hellcat to be relatively easy to land on a carrier deck. 3] The British Hawker Tempest Mk V & Mk VI and Typhoon Mk I, both low winged designs powered by the Napier Sabre engines, had 14ft diameter propellers. The Typhoon had both 3 bladed and 4 bladed propellers, whereas the later Tempest Marks mention were standardized on the 4 bladed propeller. 4] Someone did some research on the the Westland Whirlwind on why its Rolls-Royce Peregrines were so unreliable at over 20,000ft. Apparently the prototype Whirlwind managed quite well at those altitudes but production aircraft were not able to do so. It turns out that the actual culprit were the propellers. Although they remained the same diameter, the manufacturer switched from Rotol, which used thinner wooden composite propeller blades, to De Havilland (licensed built Hamilton Standard) that used slightly thicker metal propellers. It turns out that at higher altitudes, the thicker blades caused an earlier onset sound barrier compression which caused a cascade effect of reducing power, changing pitch angle of the propellers, which in turn caused unexpected extra stress on the Peregrine engines leading to early failures of the engines.

[@makantahi3731]

4) nice

[@josephpacchetti5997]

Excellent Video, Thank You Sir.👍🛩

[@macky4074]

Excellent video, new subscriber 👍

[@BlueMax333]

well explained

[@Bob-sk6xq]

Brilliant. Thanks for sharing.

[@GregoryZucco-z6m]

Great Presentation, glad you mentioned the F4U Corsair, would like to know how when the Corsair got a more powerful engine they went to a 4 bladed prop. Also I would like to know why the C46 Commando went from a 4 bladed prop to a 3 bladed prop. My Dad worked 4 bladed prop C46's in the Philippines but most pictures show C46's with 3 bladed props.

[@hitriyzhuk9879]

Wow. That guy knows the propellers theme for sure.

[@mikemc330]

Well done video.

[@MartiA1973]

Oddly fascinating - thank you

[@robinconnelly6079]

Really interesting. I didn't know there was so much in the propeller choice of an aircraft

[@benpeirce2531]

I liked your video. A very Basic and simple theory of props. Your next video should be on a steped up props. Pull vs Push, prop wash, Hi speed props, F-1 racing props, Twin rotating props, Reverse rotating props and then less Do some Hi speed turboprops.

[@AGM796]

As a Zenith flyer I appreciate the multiple pictures of Zenith aircraft when discussing slow planes

[@LetsGoAviate]

🤣

[@123cp8]

Great video!

[@dwaynemcallister7231]

I think a big factor in the choice of a long prop on the P-47 is the fact that it needed high efficiency at high altitude. Otto Koppen who designed the Helio Courier wanted a long as possible prop for the H-391B, it used a 101inch two blade propeller and GO-435 Lycoming. In the prototype Helio they used a 11 foot prop behind a 145 hp engine, three point landing and take off was required. One design factor not often talked about is twist, if you want efficiency, the correct amount of twist is required for the intended speed.

[@feedingravens]

Well-covered. what is missing is blade thickness and blade camber as parameters. There are so many parameters that all interact - like most technical problems.

[@LetsGoAviate]

Thanks. Yeah blade thickness is the least changable parameter (relatively speaking). Changing thickness changes camber, and that changes lift/drag ratio of the blade (which changes more things down the line, like optimum lift/thrust spinning speed). There's is not a whole lot of room to "play" with thickness and camber to cater for more or less horsepower.

[@googlefuuplayad9055]

Super nice video! ☺️👍👍 Thank you 🐈🐾🐾

[@bobrose7900]

There are some interesting bespoke air frames that have been modified for speed(what else!) that demonstrate all your points perfectly. I don't think cost was mentioned which is a major factor at the design stage for most aircraft, as with any other machinery. Great video.

[@IBRAHIMSERNO]

Hi, do you have any cast off aviation related items for sell please? Ibrahim from Cameroon.

[@Pootycat8359]

10:29 I LOVED those "wheel landings." So EASY! I think there's a reason your instructor teaches you stall landings, first. If you learn wheel landings first, you wouldn't be motivated to learn the 3-point kind!

[@acompletelynormalhuman6392]

The air from a propeller being faster and contributing to drag makes wing mounted engines and pusher set-ups make a lot of sense also i assume wing mounted engines would contribute to lift so that would be interesting

[@karlpeterson9334]

How do you know that on an AT-6 Texan, that sound doesn't primarily come from the exhaust pipes?

[@LetsGoAviate]

That isn't how a radial engine exhaust tone sounds. They make a low-pitch rumbling/gargling sound, not a high pitch "screaming" noise like in the clip in the video. When the T6 is in cruise, and the propeller pitch is set coarser, i.e. slowing down the propeller speed and thus the tip speed, it doesn't make that sound anymore.

[@RobFeldkamp]

Would a 3 bladed prop not actually make MORE (in stead of the same amount of) noise as a 2 bladed one (given everything else is the same)?

[@bryanst.martin7134]

@00:03, that looks familiar. C130 Later model, yet not 6 or 8 blades. I miss their Sigh. As a single shaft, they were nice powerplants.

[@44R0Ndin]

Given a fixed geometry of 2 bladed propeller, you said that if you switch to a same-diameter 3 bladed propeller you can reduce blade width (chord), prop diameter, or blade pitch to allow the same engine power output to spin the propeller at the same speed. However I don't think you covered the effect of changing blade the blade's maximum thickness, and aside from my understanding that wings with a lower thickness are needed for aircraft that intend to travel at transonic and supersonic speeds, I am unsure if this would have any meaningful effect on allowing the propeller to spin any faster. I do know that it would in theory reduce thrust, which should reduce drag, so a sufficiently lower thickness of blade airfoil profile might allow for the propeller as a whole to spin at the same speed as the 2-bladed propeller, however I am unsure if it would produce the same amount of thrust or not. I'd appreciate some info on this and other things like blade camber, since they seem to have not been covered in this video!

[@LetsGoAviate]

That's a very good observation. Indeed I didn't cover changing blade thickness as a method of adjusting power absorption. While blade thickness can easily be change by also changing blade chord length, the two can't really be changed independently from each other, because changing blade thickness without changing chord length changes camber, which is a very important property for the blade's thrust producing properties, as well as determining a blade's stall characteristics. While it can probably be changed slightly to increase or decrease the load on the blade (power absorption), I strongly suspect manufacturers don't change blade thickness after initial design, i.e. a manufacturers propeller range from 65" to "75" diamater blades (as an example) will have the exact same camber shape. Camber also contributes to blade strength, i.e. a thicker blade has more material and thus more strength. So blade thickness can also not be freely reduced as it has an impact on the strength of the blade, which is important. Manufacturers thus probably (I guess) choose the thinnest camber shape they can get away with material strength-wise. Thus changing blade thickness (and thus camber) afterwards would change the aerodynamic properties of the blade throughout it's speed range, requiring propeller design to start from scratch. There is probably even more factors I didn't mention (propellers are extremely complex aerodynamically), but hope that helps as a start.

[@Major_Tamre_Colby]

I'm a fighter pilot, specifically I drive a F-16 which of course has no need for a propeller. But before the Airforce I was a stunt pilot with a degree in aeronautical engineering. Because of that this little gem caught my attention so I tuned in. And without going into different minor debates about fluid dynamics vs. air flow over curved surfaces, high level physics stuff I wanted to listen as it I had little or a more layman level knowledge of what was involved. I.E. your general causal viewer. What grabbed me almost immediately baring the formula mumbo jumbo was how I immediately grasped what he was trying to relate yet I could also do so without a lengthy explanation of the math involved, which thankfully he bypassed. What I came away with is what the quality of what makes for the best pilots which we call "feeling the air", not necessarily understanding why what you are doing with your aircraft's air surfaces are doing what they do but instead just feeling how to make your aircraft flow in a dance through the air. The first quality I look for in new pilots to the squadron I command whether they were a high school dropout or had a PhD. And to this extent I found his simple explanation made me "feel the air" as he went along. And considering he bypassed the winded explanations which would have turned off your casual viewer but instead would make then "feel the air" I have to rate this video a double bravo! And for the stuffy critiquers out there you can take high vectored noses to your local Red Barron bar and debate it among yourselfs but in the end that doesn't mean squat whether or not you're a cloud dancer or a clumsy gomer behind the stick or yoke. But a video like this might grab the imagination of some rookie high school cloud dancer enough to intice them to "feel the air" for themselves. And because of that once my congratulations to this video directly because of it's understandable simplicity. Bravo! Bravo! 🙂👍 Слава Україні! Слава його героям! Deus Vero Honorat et Sacrificium, Maj. Tamre' "Vixen" Colby Cmdr. 347th Bravo CAS/AS USAFE/NATO SOCOM EPAF (P.S. Please excuse any spelling or semantic mistakes but duty calls and I get the guilty pleasure of setting off a klaxon that will make most of the base jump out of their pants. Maybe that's why they gave me the callsign "Vixen". As in the adjective not as the noun. Ta! Ta! 😇😅)

[@LetsGoAviate]

Thanks for the great comment. I'm very happy when it get's through as intended, I deliberately try not to go too deep into math's and formulas, and rather try to have the viewer visualise it. Some love it, some hate it. But I maintain that you don't need an aeronautical engineering degree to be able to "visualise" many aerodynamic concepts. Thanks again!

[@Major_Tamre_Colby]

@@LetsGoAviate And you're very welcome, it's a pleasure to find someone who can invoke enthusiasm among beginners and ignore bragards who only want to show off how brilliant they are even though they would probably be a danger to themselves and a menace to society behind the stick of a Piper Cub. I have no tolerance for their kind no matter what the subject. Implied insults by self aggrandizing superiority only serves the egotistical and not those seeking knowledge. So bravo five by five and don't pay attention to those desk sitting tango foxtrot ground burrowing Gomers. You've got the right stuff to be an instructor. Carry on. Bravo Joy, Deus Vero Honorat et Sacrificium, Maj. Tamre' Colby

[@joseveintegenario-nisu1928]

Good Work! Any comment about things as Coanda Propulsors, Variable Pitch propellers, and Ducted Fans?

[@Steven-p4j]

I would be very interested in learning about the new scythe looking propellers, and the new hydrodynamic propellers as well.

[@maxheadrom3088]

In Helicopters - and I'm not sure the thing on the top is called propeller, btw - do get quieter with more blades because most of the noise comes from the blades crossing over the tail. Of course that together with less rpm makes it even quieter.

[@mrcat5508]

Nice video. Suprised you only have 10k subs. Thoughts you had like 100k before I looked

[@pleappleappleap]

3:49 This can't possibly be right. This implies that, as long as you hold the speed and blade length constant, the noise doesn't increase with number of blades. So a 2-blade propeller with a 1 meter long blade turning at 2000 RPM produces the same amount of noise as a 7-bllade propeller with a 1 meter long turning at 2000 RPM? I would expect each blade tip in both configurations to be producing the same noise, and so the 7-blade propeller should produce 3.5x as much noise as the 2-blade propeller.

[@syncronisity1]

Maybe I'm not thinking about this clearly, but it seems to me that a prop works by essentially making a circle (spinning 360 degrees), so I am wondering if the more blades you have on a prop, would make it more efficient? (if physical size, and weight were not a consideration). I would think that a 3 bladed prop (so each blade only having to move 120 degrees) would be more efficient and offer better performance than a 2 bladed prop (each blade having to mode 180 degrees) that is the same weight, and diameter. Am I not thinking about this clearly, or is there some logic to my though process?

[@cjespanola5574]

When the tip of the rotating propeller reaches more than the speed of sound, it creates shockwave. The molecules of the air compacted in the shockwave. The adjacent propeller have not enough air molecule to grab to create thrust.

[@honzareality]

I love the fact that in WWII the planes got too powerful engines and they were not able to use all the power so the 3 and 4 bladed props were born. You lose efficiency gain speed.

[@philiphumphrey1548]

What to make of counter rotating propellers like some late Spitfires and the Tupolev Bear bomber? Supposed to be very efficient but also very noisy. And then there is the CFM Rise "open rotor" engine being developed for jet liners with its variable rotating and static blades. Presumably it must be more efficient than standard turbo props, faster (and equally quiet or quieter), otherwise they wouldn't bother.

[@excellenceinanimation960]

Another fantastic video about something I woner about all the time! The only question I have is what about short thick props? Can not this move larger volumes of air at lower RPM? (:

[@LetsGoAviate]

Thanks. It difficult to move a similar amount of air with smaller diameter props, even with thicker blades turning faster. There is much efficiency in length, if you consider that a roughly 40% increase in blade length doubles propeller area (when spinning).

[@RobFeldkamp]

Why would one use a shorter three bladed prop on an engine that can only provide adequate power for a longer two bladed one? Would a 2 bladed one not be more efficient? A reason would seem to be too high RPM, but your example states 2600 RPM, That's (usually) not too high is it?

[@MyFabian94]

Short Propellers are used in Air Racing Appliacations where Rate of Climb and High Altitude Performance don't matter. In Air Racing with fixed Pitch Props you want to fly with a coarse Pitch Propeller that doesn't have a lot of RPM change through the Speed Range of the Aircraft.

[@gendaminoru3195]

For STOL though, it should also be appreciated that the prop stream accelerated flow is enhancing to high lift devices; slats and flaps.

[@LetsGoAviate]

Yeeees! Since the equation of drag is the same as lift, the faster propeller slipstream not only increases drag as a function of V^2, but also lift. In the context of the video however, that faster propeller slipstream of the smaller diameter, faster spinning propeller is more concentrated over the fuselage that creates very little lift, and misses most of the wings, flaps and slats. A slower spinning, larger diameter propellers slipstream is slower, but spread out over a wider area, and will go over a larger portion of the airplanes wings, flaps and slats. So there is no real increase in lift by going for a faster spinning, slower diameter prop. On STOL one would want the largest possible diameter prop spinning right up to the max tip speed of mach 0.8, even closer to 0.9, to make use of this increased lift from the propeller slipstream.

[@larryblanks6765]

Easy way to remember 3 for show 2 for go!

[@ghostshadow9046]

Engine shaft HP/torque is a big factor in what prop you can use, You need the torque to spin the prop to optimal RPM

[@spindash64]

12:30 in theory, it sounds like you could get even lower scrubbing drag AND some nice bonus lift if you could find a way to stick 2 massive propellers at the wingtips. Obviously, structural concerns say otherwise for most cases...

[@mattp6089]

There's a reason most (not all!) fans, be it ceiling, standing, computers, laptops... have an odd number of blades. I'm pretty sure that jitter on opposing blades can introduce resonance across the pair, and increase noise as a result. So there's an odd number so that you don't have opposing blades resonating and making noise if the balance isn't great. I would imagine on an aircraft, where you could pay more attention to the balance, it wouldn't matter too much, but it might still be a factor.

[@zlm001]

Thanks.

[@petrvalkoun4539]

Also, larger prop means more air is pushed with lower speed, which is more efficient becasue of fact that the kinetic energy of the air raises by square of speed but the momentum depends on the speed linearly.

[@Freesavh1776]

Go check out the Thunderskreech YF plane in the 50's. Now that was noisy. It made the ground crew throw up & become sick.

[@andreaslack8379]

You say with same rpm, blade length and shape perfectly balanced a two blade and three blade prop would make the same noise. It seems to me that in that scenario the three bladed propeller should make more total noise because there are three noise sources instead of two. That what is really equal is the noise generated per blade. Am I understanding correctly?

[@varshneydevansh]

subbed immediately

[@djg6015]

My former employer ferried a BE58 Baron with one two blade and one three blade propeller. It apparently flew in a straight line.

[@erickborling1302]

This is for the consideration of aircraft designers only. Your existing airworthy aircraft's propeller is limited by the type certificate data sheet, so you DON'T get to experiment with propellers on an aircraft with a type cert.

[@LetsGoAviate]

You can experiment as you like as long as there is an STC for each prop you fit. Take a look the STC's for the Cessna 172 for example, you have 2 and 3 blade options, of various blade lengths. Depending on the engine and model of Cessna 172, you can fit certain Hartzell, McCauly, MT prop, Sensenich and possibly more. That's certified aircraft. On most experimental there are virtually no propeller legal restrictions.

[@airmecher]

​@@LetsGoAviate You are exactly right with an exception. If you place the aircraft in experimental for a short time while experimenting you can do whatever you wish. Then bring it back to normal with a certificated prop installed. But I bet you knew that too! I have done this many times with different engines and such doing research for mods.

[@sidecarbod1441]

Some model aircraft use a single blade prop, they spin them at 30,000 rpm, having two blades would mean that they are almost spinning in a vacuum. I think they are F2A control line planes. (The spinner has a counter weight so that the single blade is still balanced)

[@LetsGoAviate]

There are some single blade propellers for full size airplanes too, like the Everel single blade prop for the Piper J3 cub, and some motor gliders have them too. Very interesting, did a video about it some time ago.

[@GeneralSirDouglasMcA]

My grandfather was a crop duster and he flew an Ayer’s Thrush Commander with a 600 hp radial that had a 2-blade prop. Talk about loud. We would always hear him for miles.

[@core_of_winter]

Interesting video. What about blade width (or chord length)? I've always liked the look of scimitar props that have very wide blades. I imagine they are draggy though in top speed, but perform well clawing the air during climbs?

[@realvanman1]

I have long wondered how much extra drag is created by having the fuselage within the propeller slipstream... Almost like it would be better to have the propeller(s) mounted out on the wings... 😉

[@MrDino1953]

Is there an equation that captures all these factors? If so, it could have made the video more concise and added a quantitative aspect that appears to be missing.

[@LetsGoAviate]

Thanks for the constructive criticism. There are many equations for each argument, all requiring aerodynamics/aeronautical degree (or degrees in related fields) to understand, and many which are worthy of a Masters degree thesis. The ethos of this channel is to use as little equations as is possible so that anyone can understand it, not just engineers and scientists. My argument is those who understand the equasions don't need a KZbin video to show them the equation. Perhaps a bit presumptuous but that is why I opt for using as little as possible formulas and equasions in my videos.

[@flyer5769]

Maybe you can help me! Why is it so taboo to manipulate the flaps just before landings. As a former Alaska 135 pilot. The first of two thing I was told to learn. Was to get comfortable pulling the flaps before you touched the runway. Cessna 207's and grand Caravan had the same kind of flaps. Wherever you moved the indicator, the flaps will move to match it. You're not going all fall out of the sky because you're right in the middle of ground effect. Your stall speed is way low. I'm not trying to argue about this. This is what I did for four years. I just want to know why it's such a big deal.

[@larryweitzman5163]

One thing I didn't hear is that a single bladed prop is most efficient as it runs in less disturbed air, as a two blade is more efficient than a three blade again because the blades run in less disturbed air or blade wake and so on. Could you comment on this issue.

[@LetsGoAviate]

Single blade is more efficient, but not because of less disturbed air. The propeller pushes the wake backwards, so by the time the 2nd or 3rd blade gets to that point, it hits new undisturbed air. So perhaps a myth that I will cover in the next one. Blades has efficiency losses, noise, bending etc, so less blades is more efficient. But this is fairly minor compared to the fact that more blades have more power absorbtion potential. Someone said it's thrust that pushes the plane, not efficiency, and 1 blade has very limited power absorbtion or thrust, regardless of higher efficiency.

[@larryweitzman5163]

@@LetsGoAviate Hey its exactly what I said, the single blade runs in less disturbed air, or cleaner air. The plane moves forward, so it runs is less disturbed air.

[@valentinfelsner277]

Why are then winglets not more common on propellers? They should be a nice compromise, keeping blade length short while aerodynamically presenting a long blade. This should give high efficiency?