Revolutionizing Flight! The Amazing Potential of the CFM RISE Engine.

[@MentourNow]

Go to curiositystream.thld.co/mentournow_0123 and use code MENTOURNOW to save 25% off today. Thanks to Curiosity Stream for sponsoring today’s video.

[@haylieg2780]

I am amazed at how quiet the CFM Leap engines I versus the CFM 56 engines. That is even a big difference. And since the only airline I fly is Southwest I get a Lotta time in 737s.

[@typxxilps]

What does Boeing and Airbus have updated the engine mean in reality, only new planes or are they even upgrading older engines ? I have no clue if those jet engines are swapped like in tanks or heavy trucks or ships or if the jet turbines are only refurbished . I think I have seen an Airbus engine swap during a major inspection but that had been a Luftwaffe / Airforce airbus where things might be different. I was wondering if the airplane manufacturer also offer a kind of technical upgrade packages like the interior updates that these plane usually get, but in this case on the technical side. Maybe a topic for another video about the life circle of a plane from its delivery over maintenance and second / third hand to final destination as a standby reserve in the desert, scrapyard or spare part donator and also how the manufacturers do upgrade the airplaines for a longer life and therefore higher sustainability. Can not remember to have heard about except all the mandatory upgrades if the FAA forces the manufacturer to replace parts or change things. Maybe too much for 1 video so maybe a mini series but I have not seen a full life cycle video and especially how long such planes are used that we do not see anymore but are still used in third world countries - and of cause the effort to update a plane. We went from 0 and ground in spring of 2020 to back to a full speed ahead and some of the retired planes also have returned like A380 which had been considered to unefficient back then. Sorry, just a bloody amateur and hobby glider.

[@dimitri1515]

No way will open fan blade engines will ever be safer than the encased engines.

[@Wannes_]

I wouldn't be surprised if this engine ended up on the Boeing/NASA high braced wing "demonstrator"

[@alielabdimarras7965]

@@dimitri1515 How often is a blade off event happening and chance of hitting fuselage is also what ? 15%?? I sat a few times in the line of flight of a blade in ATRs and chances are bigger I get overrun on my bike or motorbike than a blade shaving me. Just asses your life risks right, and if you smoke or are overweight don't even make the effort to consider this.

[@jeffberner8206]

I am a retired Boeing engineer here who worked on 7J7 program when I first hired into the company in 1985. This is a good summary of what happened. But one thing which is left out is the generally unforeseen business success of the 737-300 using the CFM-56 engine and the use of hub-and-spoke. With both low fuel prices and the success of the 737-300, there was not need for the technology of the 7J7 to meet the requirement of Delta's RFP for a 150 passenger aircraft. There was quite a bit of government and industry focus on fuel efficiency in the 1970s due to the oil crisis. Methods of design and certification of advanced composite materials, which would have been used on the 7J7, were initial researched during this time as part of NASA's effort to reduce fuel use. The use of composite materials in primary structure on 7J7 was pursued in fact to address the high sonic environment of the unducted fan. One other reminder is that the cruise speed of the 737 Classic family of aircraft (737-300, -400, and -500) is between M = 0.74 - 0.78. So the lower cruise speed of a CFM RISE engine is not that out-of-the-ordinary in comparison.

[@MentourNow]

Thanks! That’s great insight

[@w8stral]

Yea, your memory is a bit faulty: What killed the ultra fan was... the ultra fan and its abysmally LOW mach speed required. Who is going to pay $$$ to fly in a Mach 0.6 aircraft instead of Mach 0.82-->0.85? No one. Noise was just the nail in its coffin.

[@jeffberner8206]

@@w8stral I might not have known about any findings from flight test as this was not my engineering discipline, but the 7J7 was most certainly designed to be a Mach 0.83 airplane.

[@jimmygee3219]

@@w8straldid…. did you really just try to tell an engineer who worked on that aircraft he’s wrong?

[@Dirk-van-den-Berg]

Dear mr Berner, are you saying effectively that Boeing chose the short term commercial profits over developing a modelengine for years when oilprices would go up?

[@philsurtees]

I never really had an interest in flying, but I'm an engineer who has spent more than 30 years solving problems - it's my passion - so I have always loved videos about aircraft accident investigations, so I started watching your videos, and now I am fascinated by the airline industry as a whole, which is my round-about way of saying that your videos are fantastic - Thank You - and are so good that you have converted someone who had no interest, and no intention of becoming interested, in the topics you discuss. That's how brilliant your videos are... Keep up the great work!

[@MentourNow]

Wow! That’s really nice to hear Phil 💕

[@abhishek9354682116]

@@MentourNow Expecting video on crash in Nepal.

[@hs5632]

Exact same for me. Engineer with no interest in flying but I love the Mentour analytical videos and look forward to new ones.

[@jlgood89]

same story here, just not an engineer!

[@gaetanguimond7213]

Hi, you should have a look at Samson switchblade flying car or Samson motors. You will probably like it.

[@airbus7373]

It’s worth noting that the US tried their hand out at supersonic propellers as well with the XF-84 “Thunderscreech”. That plane was also ridiculously loud

[@easy_eight2810]

We're gonna devolve back to noisy flying after just finding the perfect sweetspot between cost/noise reduction

[@StrikeWyvern]

FUCK YES I WANNA SEE THUNDERSCREECH 2.0

[@WalrusWinking]

@@StrikeWyvern You maybe want to see it but you don't want to hear it.

[@richardlahan7068]

​@@StrikeWyvernThe sound was so intense, it had ground crews upchucking.

[@nigeldepledge3790]

Even if you could find a former Tu-95 pilot to ask him what that plane was like to fly, he wouldn't be able to hear you asking the question . . .

[@GasPipeJimmy]

Yes, unfortunately nobody here gets the reference. The Tu-95 was the loudest production aircraft ever built as its propeller tips were almost always supersonic.

[@DavidSmith-vr1nb]

@@GasPipeJimmy Well, we get it now because you have conveniently explained it for us.

[@Raminagrobisfr]

@@GasPipeJimmy yet it was modified into an airliner (Tu-114)

[@MartinMizner]

I think Americans also had modified Thunderstreak named thunderscreech with propeller and it was also very noisy

[@godfreypoon5148]

This problem is easily solved by giving the question in written form. 🤓

[@colinw7205]

25 years ago I discussed why the Propfan didn't get any traction with a dear friend who was a professor at a aviation college. He said the biggest thing that killed the Propfan wasn't only the noise. It was the marketing focus groups. The public was turned off by the appearance of the open fan blades which made the aircraft looked like the one that that parents and grandparents flew in. I remember at the time there were designs floated around that had a massive duct around the fan with the core of the out in front for underwing widebody plane i.e. the 747 to give Propfans a more "jetlike" look.

[@IxnayMalarkavitch]

Yea. I’m not an aviation person. The engine in the video looks frightening.

[@ProctorsGamble]

The public wants planes ✈️ that go whoosh 💨 and not buzz 🐝 and don’t want to see things moving 😆

[@jackstheraptor2791]

For me it's not about the look but that open fan blade design. It's dangerous even with those reinforcements. the reliability cannot be 99.99% but 100%. A simple fan blade hit during the flight can rip the plane apart, while the same failure in modern engines may not even notice by some passengers! Its a huge gamble IMO.

[@MrCJHamill]

I can see how that might be the case. I personally feel that traditional jet engines do look much better cosmetically speaking. Though I also reckon the turbo props on a Beechcraft King Air for example look quite amazing as well.

[@therandomytchannel4318]

Prop Jet technology has come quite a ways since that zombified 727 with that experimental prop jet engine on it, I remember it sounding pretty much like a flying weed wacker 😂

[@kevinmahoney9205]

Around three decades ago I was a student at Embry-Riddle Aeronautical University. We were shown a video of the "un-ducted fan engine" and it sounded promising. I always wondered what happened to it. Now I know. Thanks for this video.

[@Juanxlink]

Was about to say, distincly remember reading way back when about it, propfan 727 no less.

[@ErvinandMFantasyFootball]

This is why I love YT and the internet. Incredible.

[@kevinmahoney9205]

@Jaxon B. I wish you the best! ERAU is very expensive, so make sure you do your best.

[@markortiz1506]

I worked on it directly back in 85-86. My memory was that, as expected, there were tech challenges but the deal killer was the precipitous drop to $10/barrel oil. This was much more expensive of an engine than normal engines (2.5 X) and the value prop fell through. The value was fuel savings. With ultra cheap fuel, it didn't make sense. Tech was compelling. Business case wasn't.

[@sharoncassell9358]

My lady cousin went to EM too. Became a pilot for United. Retiring by now. Bye to 747 for her. Sad.

[@joewiddup9753]

I didn't know the Tupelov Tu-95 Bears were noisy because of the tip speed, I always thought it was a straight fluid dynamics issue. After the end of the cold war, the American Navy admitted they could identify them with submarines in the Arctic Ocean with Sonar microphones. An aircraft so loud they could hear it at cruising altitude from below sea ice.

[@davidlindburg1921]

That makes sense: the achilles heal of the world's fastest turboprop aircraft! 👍🤭

[@johniii8147]

The Russians ( USSR) were never able to match the US in technology. That's no surprise.

[@statinskill]

@@johniii8147 You do realize that these planes laumch state of the art hypersonic nuclear-tipped cruise missile? Weapons we have no real defense against. Nearly every cruise missile on those planes will hit and destroy its target.

[@johniii8147]

@@statinskill Not really worried. They can't even take down Ukraine at this point. We have plenty of defense against them since they are clearly spotted coming. And they may 10 of those missiles actually active.

[@grizzlygrizzle]

Maybe some complementary research should be done on acoustic isolation for fuselages. That would make flights quieter for passengers, if not for neighbors of airports.

[@NicoWings]

This episode hits home! In 2013-2014, I worked on the design of the engine mount system for that Safran SAGE2 open rotor engine demonstrator under Cleansky EU initiative. I learned a lot as a younger Aerospace Stress Engineer. Proud to have been part of it 🙂

[@EzaneeGires]

Fellow Clean Sky grunt here. Good to see you

[@michaelkugler8620]

As a young engineering working at Pratt & Whitney Aircraft back in the late 1980's & early 1990's, I sat in a presentation from the President & CEO of P&W revealing how the engineering efforts were going to be totally dedicated to developing the counter rotating fan engines. Extensive work had already been done on blade and gearbox development. It was an exciting time to be working on the projects to support this effort. The Applied Mechanics lab an experimental engine development was running wide open and the test cells were always running full scale tests around the clock. However, world economics (as mentioned) and the Desert Storm conflict brought all the development (and the commercial aircraft industry in general) to an abrupt halt. It amazed me to observe how this effort disappeared almost overnight. Flight testing was well underway and there were talks about achieving FAA certifications and establishing goals to meet them. Great video!

[@adb012]

2 things not mentioned here: 1- The casing also adds drag. 2- These new-generation open rotor engines moved the rotor to the front (they are puller rather than pusher). Pusher propellers (or rotors in this case) are much noiser because they encounter uneven "dirty" air. Uneven because the engine must be supported somehow and that creates an area of "shadow". And dirty because they are in the wake of turbulent boundary layers at least from the engine and from the pylon. Puller props on the other hand receive a very even flat and laminar profile of oncoming air, which makes them less noisy. 1 thing mentioned here wrong: Turboprops are not required to keep a severed prop blade from penetrating the fuselage. And they don't. In every instance where a prop blade separated at operating RPMs and flew in the direction of the fuselage, they penetrated the fuselage, sometimes killing people, some times damaging critical systems (like control cables or hydraulic lines), and sometimes even exiting the fuselage at the opposite wall.

[@Hikari_Sakurai]

maybe the solution could be to increase structural strenght in those areas so they wouldn't get penetrated in such scenario.

[@hydra70]

@@Hikari_Sakurai That's not necessarily possible. Everything in an aircraft design is balanced against weight. You can only add so much weight in reinforcement and it might not be enough.

[@Hikari_Sakurai]

@@hydra70 actually you're wrong. he mentioned it in the video that some of those aircraft had reinforcement in the areas close to the rotors. I wasn't that far in the video when I commented on it.

[@miscbits6399]

@@Hikari_Sakurai the reinforcing is there for ice protection. Chunks thrown off the blades can penetrate the fuesleage otherwise

[@AmbientMorality]

@@MattyEngland This is so heavily dependent on the car and the grid production sources that it's kind of a meaningless claim. If the grid is purely fossil fuel you won't see much of a benefit, but obviously if it's heavily renewable that changes a lot

[@throughthoroughthought8064]

I saw this propeller design in the mid-late 80s, probably in Popular Mechanics. I've thought about it many times. It's been a long wait to see it in action.

[@miscbits6399]

As mentioned, it was REALLY FRICKING LOUD The gearless blades were directly attached to turbines and spun at very high speed because that's the only way to efficiently extract work from the exhaust airflow. The bigger problem was simply that nobody wanted the 7J7(*) and the DC9/MD80 was "good enough" as-was for the kind of routes it was flying (*) Remember this was when deregulation happened. Traditional airlines had mostly been happy to run fleets of differing aircraft but the only thing that 737 budget airlines wanted was "more 737s" - anything else needed pilots and maintenance crew qualified to fly them (expensive)

[@CaveJohnsonAperture]

Yup I was thinking of that exact issue that also said in only a few years these would be on every airliner. Propfans etc. are super cool but remains to be seen

[@Mantek430]

I had similar feeling that it's relatively old design.I first saw it on soviet aircraft and thought that such idea started in USSR. It also looks similar to Kamov principle on few russian helicopters.

[@CaveJohnsonAperture]

@@Mantek430 The principle of contra rotating props alone isn't what a duct fan necessarily is limited to

[@belperflyer7419]

My main concern about this type of engine is blade containment - or lack there-of. In the 1990s I was heavily involved in fan blade containment tests at Rolls-Royce when we were testing the use of a Kevlar bandage as a lighter alternative to a metallic casing. It was successful but the destructive potential of a free blade (which we blew off with an explosive charge at the appropriate speed and position for the high speed film cameras to capture) was chilling to watch. I wrote the s/w and designed the electronic h/w that controlled the test. I was also involved in the design of the h/w and s/w to measure blade untwist which needed probes fitted in the casing. Presumably these blades untwist under load too but positioning the probes might be a challenge :) My only aviation interest after retirement is model aircraft. It's considered that fewer blades in a propeller are the most efficient (in fact speed control line models have single blades with a balance weight). I wonder how that affects the oddly shaped blades on these engines.

[@MikeRodent]

Haha. Yes, those seats in the cabin level with the blades will be cheaper: problem solved.

[@subtropicalken1362]

Being an engineer I give you kudos for saying “0.xx”. Whether written or spoken it is a good example of minimizing potential errors. Well done.

[@john_hind]

But then he spoils it by saying 'zero point twenty-two', for example. I would always say 'zero point two two'. Trouble is, how do you say 0.03? If you say 'zero point three' it sounds less than 'zero point twenty-two' and could easily be heard as '0.3' or '0.30'.

[@subtropicalken1362]

@@john_hind can’t speak to pilot speak but I would say zero point zero three for 0.03.

[@john_hind]

@@subtropicalken1362 Sensible, but I guess you'd also say 'zero point two two' not 'zero point twenty-two'?

[@subtropicalken1362]

@@john_hind agreed!

[@freshname]

@@john_hind in other languages it's ta"zero point (coma in some languages) thirty three" or "zero point zero three". I don't know how pilots say, it's just how everyday people say it on the street because that's how it is taught in schools in 4th grade when different fractions are in focus. Whatsoever it doesn't constitute a problem. Everybody understands the difference between "zero point thirty three" and "zero point three" and "zero point zero three".

[@tyrotrainer765]

I was flying in a UK E3-D, with CFM-56s, in 1994. On take off we had multiple birdstrikes to the port wing and engines 1 & 2 suffered uncontrolled destruction, with blades flying in all directions. I was sitting right next to engine 2. None of the fragments hit the fuselage, but both cowlings were trashed. When those engines are at takeoff power there is a vast amount of energy. How I'm still here is a miracle.

[@mjmulenga3]

Did the aircraft take off successfully?

[@tyrotrainer765]

@@mjmulenga3 Hi, yes, just! We were Max all-up weight and were lucky to have the best pilot in the fleet as Pilot Flying. He had to actually bank slightly in order to clear a church steeple a few miles from base. It took us 20 minutes to reach 1500ft, very tense to say the least!

[@bryanbryan2968]

@@tyrotrainer765Umm wow! Your airplane incident sounds very similar to what happened in the movie, ‘Flight’, with Denzel Washington and John Goodman. Perhaps ‘Flight’ was based upon the incident you described and experienced.

[@tyrotrainer765]

@@bryanbryan2968Hehehe well, our Captain wasn't drunk, and we never went inverted!

[@bryanbryan2968]

@@tyrotrainer765 Heh, interesting. Was your flight well known to the public? Glad no one was hurt.

[@scotty2307]

The Russian "Bear" bomber is exceptionally loud, but is also a really cool looking aircraft. When I was stationed on the USS Carl Vinson in the early to mid 80s we had to intercept a Bear bomber with F-14s and "escort" them around the fleet. They were allowed to pass close by, but not directly over the fleet, so they were quite close and easy to see from the flightdeck.

[@ShadeAKAhayate]

Literally any flyable aircraft is cool-looking. At least in its way :)

[@korana6308]

I agree. Pretty cool looking.

[@DonnerPassWhisky]

Great information. In the 1980's I was in the USAF as a 316X3 (instrumentation mechanic). Most of us worked in AF systems command that was the R&D department of the USAF and at that time there was a lot of talk about propfans. Then it just ended with the noise issue being the reason given. Thanks

[@williambunting803]

I think the CFM Rise design brings some clever aero dynamics, by incorporating what I think is a Goldschmeid drag reduction feature. The bulbous housing after the stators might seem counter productive, but it likely has a lower air pressure on the leading side relative to the trailing side where the general body of air collapses around the housing induced in part by the engine exhaust higher velocity flow, and the collapsing higher pressure on the housing squeezes the engine forward cancelling some leading end drag. It’s pretty clever. Engineers have been trying to incorporate this feature for decades with only a few successes.

[@freetrade8830]

That sounds almost like getting something for nothing. Making the housing extra bulbous should come with a drag penalty, it seems.

[@freetrade8830]

@@MattyEngland Shut up

[@williambunting803]

@@MattyEngland I think that they covered that in the script, ME. The fix for that problem is to reinforce the fuselage in line with the propeller to prevent penetration. Also there would be an additional safety factor in the balde and hub design.

[@miscbits6399]

@@MattyEngland How often do turboprop blades fail? The stress on the blade root goes up with the square of the rotational speed. If you're not spinning at insane speeds it's a lot easier to hold things together - that's why gearboxes have been a critical step for big fans (turbines only couple efficiently into exhaust flow at high speed whilst fans only couple efficiently into air at relatively low ones) The shielding is mostly there to prevent damage from ice being thrown off the props

[@williambunting803]

@@MattyEngland Hi ME. Do you have any figures to back that notion up? It is not me saying this, it is the engineers themselves, people who have done the assessment. It’s not necessarily extra metal to penetration proof an area, it is more likely mixtures of materials such as are used for the nose cone of the A380 which uses glass reinforced aluminium. It is more likely to be using Titanium (strength of steel with similar weight to aluminium, and possible composite reinforcement as well. So most likely extra cost without extra weight. Then there are the fuel savings which were not specified but indicated to be huge.

[@captainobvious9188]

I love, LOVE how quiet the leap engines are. So I hope things just continue to become quieter.

[@michaeld5888]

Is the name because they leap out in front of the wings of those old time expired Boeing airframe designs?

[@jsmariani4180]

Unducted fans are going to be noisy.

[@tuank624]

@@michaeld5888of course not

[@jackstheraptor2791]

Why quieter? Do you really want to hear burps and farts? To me, the leap amount of quiet is quiet enough :)

[@davecrupel2817]

Not if they pursue this glorified propeller.

[@joetaylor486]

Very interesting developments. Lots of clever aerodynamics going on to permit a tipped fan blade to derive thrust at mach 0.8 without punishing noise problems...

[@gordonborsboom7460]

I’m glad you brought up the historical developments of this tech. I saw the thumbnail and recalled from decades ago these external fan developments.

[@codykinney7590]

I work for the ge composites plant that makes parts for the leap and 9x engines. This is very interesting to see and I wonder if our plant will make something for the RISE. Very cool

[@buckhorncortez]

At 2:32, the plane is flying out of the Albuquerque, NM airport. GE had an engine production facility in ABQ and the test plane was at the airport for a number of months. I lived near the airport and my house was less than a mile from the end of runway 17-35 (now closed), directly under the flight path. I will personally guarantee that the noise from the unducted fan on the test plane was not "exaggerated."

[@MentourNow]

Ah, thank you.

[@buckhorncortez]

@@MentourNow I told my wife about this comment on the engine's noise, and she reminded me that the plane could be tracked on its landing path to the airport by the car alarms being set off as the plane passed overhead.

[@YouScroob]

I owned a tool and die shop in the late 80s and actually built some bond fixtures for GE's carbon-fiber parts. GE-ABQ was the research plant for carbon -fiber tech. As I recall, most parts were nacelle pieces and fan blades.

[@buckhorncortez]

I'll give a relative noise level. At that time, the NM Air National Guard ("The Tacos") flew F4 Phantoms. Some days they would be practicing touch-and-go maneuvers on runway 17-35. The joke was we could stand on the backyard deck and wave at the pilots and sometimes they'd see us and wave back. The F4s did not set off the car alarms...

[@chrisn7188]

My father worked for the props division for Hamilton Standard and worked on this project as more than likely HS would have supplied the propellers. The issues were noise, speed and a bit more discomfort inside the cabin versus a turbofan. Both my father and brother helped design the A-400M euro transport shown in your video as well. Point being, HS - now Raytheon- played a huge role in the development of the counter-rotating prop effort and would be worth a look if one is really interested in this topic or propellers in general.

[@douglascunningham6319]

You sound like a person to ask or point out. If 2nd set of blades doesn't move but seems to channel air flow. Wouldn't a partial or solid ring at blade tips help better direct thrust?

[@AmBush2048]

That's interesting that they needed props of engines like that

[@operator8014]

My uncle worked in the props department of universal studios. Doesn't mean he knows anything about airplane stuff. Stay in your lane, sir.

[@chrisn7188]

@@operator8014 in my lane? My father worked on the design of the propellers used in the counter rotating prop effort? Which lane do you speak of?

[@sir_vix]

@@chrisn7188 Nathan Lane

[@turdpike]

Great content- although for FWIW, as a turboprop mechanic you don’t get much in the way of “blade out” protection. What you pointed out on that ATR72 at 14:37 is an ice plate. Common on most turboprops, just a sacrificial layer to absorb ice being flung off. I’ve replaced them on the ATR and they are literally just a chunk of additional aluminum double sided taped to the fuselage. Will in no way stop a blade from coming through.

[@philipheyes607]

Saw the UDF engines fly at the Farnborough air show on a trade day. It sure had a distinctive sound.

[@MentourNow]

I can imagine!

[@chrissmith2114]

Sound normally means wasted energy.... The vortices around the end of blades waste energy and produce noise,

[@TheGecko213]

Maybe they should take a leaf out of Nuclear Submarine propellar technology which has resulted in a soundless propulsion.

[@alexlo7708]

@@chrissmith2114 But why it has less fuel zipped than the less noise turbofan.

[@johnarnold893]

@@TheGecko213 Modern Nuclear Subs use pump jets almost like modern day Turbo fans but since they turn much much slower they obviously make less noise. Still, a sub has to slow it's engines if it wants to be quiet, not something you can do with a jet plane.

[@MarcusWolfWanders]

I'm union labor for a company that casts aerospace/turbine blades and vanes, etc. We occasionally trial-run casting blueprint changes for LEAP, so learning about LEAP and CFM RISE, etc is really helping add context and understanding for where the things I help make end up, and what they do.

[@shawnbottom4769]

@@daveymcc1421 Apparently it has to do with triggering you. Lighten up a little.

[@jordanlarson6488]

@@daveymcc1421 Union labor builds the parts/airplanes you trust and rely on, that's what.

[@psalm2forliberty577]

I would imagine that casting process & the Quality Control is very very demanding, considering the high stress loads upon those fans & vanes in operation.

[@godfreypoon5148]

@@jordanlarson6488 I think I'll take the train next time.

[@misterserious3522]

@@daveymcc1421 Raising costs for everyone, like always.

[@John-hj2mv]

I remember sitting through my A&P classes learning about the inducted fan design and thinking about how much further along most companies are in their R&D than their current products would indicate. It's interesting to learn what factors ultimately decide if and when those new technologies and techniques get introduced to the market. Thank you for your video!

[@clevelandaeromotive]

I saw these engines premiered on a 727 on an episode of That’s Incredible in 1981. Amazing that they’re back after 4 + decades.

[@PistonDriven]

Hey Mentour. Lifetime airhead, here. I've enjoyed most of your videos on crash investigation, and still will, if you continue with these, I'm sure. However, I must really give you kudos for your new line of videos, where you explore technologies and the business, in general. Highly instructive, even for an armchair expert, like me ;-) Thank you and keep the blue side up, as the other guy would have it

[@Dirk-van-den-Berg]

I watch Kelsey's videos too. Too bad he dismissed Petters reaching out to him.

[@seriouscat2231]

@@Dirk-van-den-Berg, what happened? Or where can I see the story? I've been watching both but been too busy lately.

[@rogerpearson9081]

I thought the UDF concept was just an oddity from the 80s but now it springs up as a likely future candidate. Interesting to see the latest designs have a stationary row behind the rotating blades. Must be a lot of energy in the airflow spiralling off the front blades but a lot simpler than contra rotating blades. The Russian Bear aircraft were unique for their mode of operation where they were in a steep pitch close to a feather position which was why they could fly so fast. Quite a talking point at the time.

[@ArneChristianRosenfeldt]

I wonder if the shroud could be more minimalistic and made of moveable blades similar to the static row. So depending on speed they would form a more concave or convex duct ( or each segment variable to account for angle of attack). Apparently, we don't care much about tipp losses or gaps anyways. Then the propeller tips could reach through the aft-loaded low-velocity part of the shroud wings.

[@spiderzvow1]

this just keeps reminding me of the Republic XF-84H Thunderscreech. which had the honor of turning a lot of fuel into a lot of noise. It was so loud it allegedly caused people on the ground to get sick. It also could not fly without the Ram Air Turbine extended IIRC.

[@srinitaaigaura]

Thunderscreech.... It must have been something special to get such a name.

[@andrewtaylor940]

@@srinitaaigaura Just starting it up would physically incapacitate the ground crew out to a radius of several hundred feet. Vertigo, Nausea, etc. Ear protection did nothing. It's viewed as the loudest airplane ever built.

[@nate0765]

@@srinitaaigaura Its interesting to read about, the supersonic propeller it used produced continuous sonic booms. The plane could be heard 25 miles away and it made people nearby sick, an engineer even suffered a seizure.

[@aredub1847]

@@nate0765 Thats like Warhammer 40k stuff. delicious.

[@TianarTruegard]

There's gotta be a way to use some sort of noise cancelation effect on the props, or in the way the props are designed to allow for supersonic props without as much noise.

[@alihosseinmardi5672]

It is also worthy to mention An_70 as one of few propfan aircraft built and tested.

[@PasleyAviationPhotography]

I was surprised this wasn't mentioned, glad I'm not the only one who thought this as well.

[@Sajuuk]

Slava Ukraini 🇺🇦😁

[@constantinosschinas4503]

Mentour pilot is a known boeing fanboy. Even supporting the company after the criminal MAX accidents.

[@bombappetit]

It's unfortunate that An70 did not get much fanfare or orders. It is an awesome aircraft.

[@mrvwbug4423]

Bizarre sounding engines too, also quite loud if I recall. Hopefully Ukraine was able to get the prototypes out of Ukraine to avoid the same fate as the AN-225

[@10p6]

About 40 years ago, when I was 10, I came up with a design for a fan engine with about 75 percent bypass. Maybe one day I should 3D model that. I called it the CLM.

[@jimiraybeckton]

I’m a big fan of your channel, and I look forward to every new video! I’m also an employee of GE Aviation here in Cincinnati, so I love hearing you talk about “us”! We’ve definitely got some great things going! Can’t wait for the next one!

[@Zach-td5mb]

Can I ask how you got on their? I’m graduating from Miami next year in ME, and I was looking to intern there this past year but it said you needed previous GE experience to be considered.

[@jimiraybeckton]

@@Zach-td5mb hmmm…I’ve never personally heard of that policy. It’s a really big place though, so it’s certainly possible that those policies differ from one area to another. It usually just comes down to being around at the right time. When they’re looking for someone that does what you do. My best advice would be to be a little flexible, because there’s a lot of movement internally, so get yourself in the door and then maneuver to get exactly what you’re looking for! Good luck!

[@ShauriePvs]

You mean ultra fan of this channel😅

[@JoeHamelin]

I'm proud to be an employee of Safran. It's great working for such an innovative group of companies.

[@pizzablender]

The French always have these beautiful company names. I guess it is Societe Anonyme Francaise Auerto Nautique or something like that?

[@sjorsangevare]

@@pizzablender When I heard the name "Snecma" in this video I almost burst out laughing, that one is definitely an exception to beautiful French names 😂

[@CountingStars333]

@@pizzablender Satanic France. Sa Fran

[@avroarchitect1793]

ok can you explain to me how this is any different than a turbofan that just spins faster than normal?

[@JoeHamelin]

@@avroarchitect1793 Nope. I'm in IT.

[@novo6462]

4:45 Gotta love that design with the Center stick and and FMC just below the PFD. Someone with experience in making FS mods needs to create this! 😁

[@michaelkugler8620]

My first job while at Pratt & Whitney was in the Project Materials Control department. We were the liaisons between Engineering, & Experimental Test/Assembly. I was the person who wrote the work order to begin the development of the "Fly By Wire" Engine Controls, to be developed by the P&W Willgoos Engine Controls Development lab. Back in 1986 the initial budget was $1.5 million.

[@leebee1100]

@@michaelkugler8620that’s incredible! Thank you for that

[@aaronsmith4746]

Great video! I remember reading about open fan engines in Popular Science in the 80's. Thanks for including the history of these designs.

[@mdhazeldine]

Excellent video. You answered all my questions. Mainly the blade out one, which was the most obvious concern. Also the size and fitting under a low wing.

[@cavscout1739]

The big problem, as I see it, is blade separation during flight. Since, this does happen in the current ducted nacelles as a result of various things that can happen in flight.

[@BruceCarbonLakeriver]

Well that issue also is a thing on todays "regular" turbo prop aircrafts. And it doesn't seem like an issue.

[@ryanaegis3544]

What was that Southwest flight a few years ago that flung a blade into the cabin? A passenger got sucked up against the hole, plugging it with their body? I think they died like two weeks later? I worked on Rolls Royce engine casings at the time, and it caused quite a stir. No matter how well you can protect people from the engine, you still need openings at the back and front to let air through.

[@tommytwotacos8106]

IIRC, this is also why we'll likely never see miniature turbines offered as power plants in commercial automobiles, despite the potential for amazingly long engine life. Again relying on my memory, the turbo lag issue was solved by the inclusion of a small electric motor to give the wheels an initial kick while the turbine would spin up.

[@oldesertguy9616]

I am not an aeronautical engineer, nor even an engineer of any kind, but it makes me happy to see that there are brilliant people working on problems that I didn't know existed. I find this sort of thing fascinating, and you really explain it well.

[@shlomster6256]

Very informative. It'd be "interesting" to sit by a window beside one of those beasts.

[@mbryson2899]

It's odd that I don't think twice about sitting next to a turbofan prop but this new design gives me the jitters. Most likely it's because standard props have been around so long that they seem totally normal so I don't even notice them.

[@cosmicinsane516]

Considering we still have uncontained failures of both turbofans and turboprops I try to make it a point never to sit beside the engines on any flight.

[@mbryson2899]

@@cosmicinsane516 I do the same. I trust all machinery only so far.

[@marcellkovacs5452]

I flew on an ATR 72 directly next to the propeller, it was not an experience I would like to repeat. It doesn't matter if it's rational or not, the fear is the same.

[@Cynsham]

@@cosmicinsane516 It doesn't matter how robustly you design a system or how many space-age special alloys and forging techniques you use for the materials during construction, It is fundamentally impossible to design ANY system that is absolutely foolproof and incapable of failure, especially on such a complicated mechanical structure as in a modern turbofan engine. That being said, modern aircraft engines are extremely robust and extremely reliable, the incidence rate of engine failures on modern aircraft is about 1 in 100,000 flight hours, which makes it beyond extremely rare.

[@SkyChaserCom]

Amazing presentation and nice seeing these UDFs coming back. The design of the blades is crucial too to become a "supercritical airfoil" at high tip speeds - Hopefully reducing the sonic "clatter" that makes props so noisy as well as wave drag. CFD modeling has come a long way, not to mention engine core design.

[@Chris_at_Home]

I thought one of the reasons everyone ditched turboprops was because of maintenance. I was in a patrol squadron many years ago and the mechanics worked on the prop’s system more than working on anything in the engine core itself.

[@marcelb3645]

Glad you addressed the question of turboprop vs open fan... the similarity is getting impossible to ignore.

[@paulsullivan3291]

Thanks!

[@EdwardRLyons]

Thanks for this update. I followed the UDF/Propfan saga back in the day when I was a regular reader of Flight International. It's interesting to see the concept being revived for a new generation.

[@thetowndrunk988]

Very fascinating stuff. You do such a great job of explaining issues of the past, and future solutions.

[@MentourNow]

That’s what we are trying to do! Glad you liked it!

[@thetowndrunk988]

@@MentourNow I’d love to see high efficiency engines burning hydrogen. I think it’ll open up some interesting ideas going forward.

[@brianmillerthomas]

As someone who has a general interest in technology, the first thing I would have liked to have heard in this video is what CFM stands for. We're not all aircraft engineers. FYI in this video CFM is the name of an American aerospace company, and they named their company after the 3-letter abbreviation for CUBIC FEET per MINUTE. Suddenly everything makes sense.

[@wilmarbarrick3194]

🤣 I'm still watching but just from the thumbnail, I said to myself I remember engineers working on counter-rotating unducted fans 20 or 30 years ago. First thing I hear in your video... "almost had it 30 years ago".... you're really on top of your game Mentour.👍

[@MentourNow]

I have a great team! 💕👍🏻👍🏻

[@chrisworthen1538]

I remember the Pratt & Whitney program from my time in the aero engine industry. Thirty years ago sounds about right.

[@hungryhedgehog4201]

WHat's the difference between an unducted turbofan and a turboprop? Isn't it basically the same idea?

[@philippedefechereux8740]

You are always extremely well-informed - including visuals - and always smiling, because you love airplanes! I like your shows.

[@MarkiusFox]

Man, it'd be interesting to see a commuter plane with the RISE, and how that might effect the flight range.

[@madman671000]

There was a GE 36 (I think) setting in the proving grounds at the GE facility in Ohio when I was there in 09, I was also told that other than the noise issue, the pusher blades were not contained in the event of catastrophic failure/blade out, they may enter the fuselage, so the FAA frowned on this design at that time. Just what I was told. Throwing the E-6 in there was nice.

[@MVargic]

What if the engines were located at the back of the plane where the blades cannot hit any passengers, like in 727?

[@madman671000]

@@MVargic It was still an issue with compromising structural integrity and flight safety, this is why all engines now are required to have a very strong FWD fan case in the event of a blade out, the fan case must protect the fuselage. These were tests that we ran at the GE proving grounds for the GENX engine development.

[@aeckler01]

As a cooperative engineering student, I worked at Allison Gas Turbine during the time when they were developing this technology with Pratt and Whitney. I think it was around 86 through 88.

[@timengineman2nd714]

Problem with the "unducted" Fans, just like the piston and turboprop engines, is propeller "slap" where the air coming off of the tips impacts ("Slaps") the fuselage of the airplane. In fact in the heyday of large propeller driven aircraft, First Class was in the rear of the airplane to be far as possible from the "slap"!

[@ericpaul4575]

I wonder if some kind of active noise canceling could be used.

[@timengineman2nd714]

@@ericpaul4575That's why several of the designs had them mounted at the rear of the plane as pushers! (Even a Beechcraft turboprop called "Starship" had it's turboprops back there and as pushers!)

[@martinwilliams9866]

What if the blades had bent tips like some wings have?

[@timengineman2nd714]

@@martinwilliams9866 Perhaps something like how some 1920's planes had a ring around their radial engines, but not a true cowling. This helps with the. thrust of underwater propellers as well as reduce propeller noise... Don't see why it wouldn't work for aircraft propellers.

[@valuedhumanoid6574]

I loved the 727. Of all the passenger jets that one pushed you into your seat at take off like no other. The 747-400 would make you do that, but that was a rare plane to fly on for me. The short/medium range planes are what I flew the most. The 727 and the MD80. That one too was a rocket ship.

[@userPrehistoricman]

Have you flown in an E190?

[@valuedhumanoid6574]

@@userPrehistoricman Not sure. If I have I don't remember it specifically. Why? Will it pin you to the seat as well?

[@userPrehistoricman]

@@valuedhumanoid6574 It has better acceleration than the 737, that's for sure. You can find videos of them climbing steeply on normal passenger flights. I calculated thrust to weight ratio using max thrust and MTOW and the E190 is about 50% higher than the 727.

[@valuedhumanoid6574]

@@userPrehistoricman So...have YOU actually been in one to feel that yourself?

[@awuma]

Twin engine planes have a lot of reserve power in case one engines quits. The pilots usually take it easy on take off to save fuel, make less noise and not to scare the passengers. When the 737 was introduced to New Zealand circa 1970, some pilots couldn't resist the temptation to show what they could do, given that in Wellington both the approach and climb-out are over water and the air is usually very turbulent. Three engine planes generally had less reserve power, which made them more vulnerable to microbursts on approach (e.g. Delta 191, an L-1011), but I believe the 727 was designed to operate out of small airlields, hence its power. It took a few years for smaller regional airports to lengthen runways for jets in the 1960's.

[@robertrossman3703]

I worked at Hamilton Standard (later Hamilton Sundstrand, later Collins, now Raytheon) and served as the FAA DMIR on the Pratt project. The system was only a bit noisier than a turbofan, but the pitch was quite annoying. I grew up in Chicago, and the noise was significantly quieter than the old turboprops flying into Midway.

[@davidbeckenbaugh9598]

We had a Bear visit as part of an air show maybe 25 years ago. I remember being outside when it flew over at about 200 mph (a total guess). I heard it coming and told my friends that, whatever it was sounded just plain weird. The I saw the swept wings with props. Dang! These days, nearly all of us carry a camera with our phones. Wish I had it back then. How often do you see a Soviet warplane flying low over WA state? But, yes, noisy, even at low speed. These engines seem like they are going to be very nice? Whodda thunk a prop plane would be the efficiency booster of the early part of the 21st century? Not even Duck Dodgers (in the 24th and a half century) would have been onboard with that one.....

[@dex6316]

That old Soviet aircraft’s engines towards the end really seems like the open-air design they were testing in the 80s, but more primitive. Really impressive design for its time.

[@SJR_Media_Group]

The Russian Tupolev Tu-95 Strategic Bomber has used this blade arrangement since 1956. It is one of the fastest propeller driven aircraft in history.

[@agentcrm]

@@SJR_Media_Group Contra-rotating propellers where used in WW2. A quick check reveals it was patented in 1907.

[@SJR_Media_Group]

@@agentcrm Thanks for correction, I always mess that one up.

[@kenoliver8913]

The British Fairey Gannet was an even earlier successful design of a contra-rotating turboprop. As a carrier-borne search plane loiter time mattered, so efficiency was much more important than top speed. You could actually turn off and feather one of those props to loiter longer.

[@agentcrm]

@@SJR_Media_Group All good. The Tu-95 is the most well known of the early turboprops. But the contra rotating props where used on a few piston aircraft earlier.

[@johnford5568]

ok, so as far as thrust, how much is provided by the prop blade pushing air back and how much is provided by the pressure vacuum created behind the wing, or bernulli's effect if you will? It seems ducted fans have to spool up before a push is felt where as props immediately pull.

[@fr89k]

It is a good example for the point which I recently made about another technology: A technology is only dead once every aspect and possible solution has been explored and once no new material or methodologies is popping up to fix the known problems. This engine design was sitting on the shelf for over 40 years and now it has a come-back, because some companies were constantly working on it (though with little budget I assume).

[@johnnunn8688]

No, no it wasn’t. Do try and keep up 🤦‍♂️.

[@DanielBrotherston]

I'm really not understanding what differentiates these engines from turboprop engines. Seems like both function as an un-contained un-ducted propeller driven by a gas turbine engine through a gearbox. So what makes them different other than a different evolutionary path?

[@baarni]

These high efficiency engines might go well it’s the upcoming Truss-Braced Wing airliner design that Boeing is currently developing… I hope mentor talks about these at some point… Scott Manley recently did a good video about them but would like to see Mentor Pilot add to this…😊

[@kentslocum]

And now he has!

[@waynep343]

I saw the udf flying and it was insanely loud. But it was the same blade count and the shock waves from the primary prop slamming into the second prop leading edge. Reducing secondary blade count fixed the issue. I had a talk with willis hawkins about this and he agreed but he and lockheed were not involved in any of this. Willis hawkins was an inlaw and a lot of fun to talk to at the few family gatherings we both attended.

[@mrvwbug4423]

If I recall there was a fighter tested in the late 40s called the Thunderscreech that was so loud that it could generate lethal shock waves within a certain distance of the props and those same shockwaves were destroying test equipment and damaging the aircraft. Like the TU-95, counter rotating props with supersonic tip speeds.

[@waynep343]

@@mrvwbug4423 i laughed so hard reading that air and space magazine. X15s coming in for landings at edwards use to leave echoing sonic booms in lockwood valley in the 60s when i grew up there.

[@jacquesparadis6756]

As always Mentor, you’re killing it with an excellent and well researched topic. Q: Would the function of the stator vanes be to redirect the helicoidal flow coming off the main rotor? This would represent a significant gain in effective trust. Thanks. Jacques an avid listener of your channel.

[@RichyRichTu]

great question! I was wondering the same thing ...

[@Yeshua-Is-Lord-7]

Yes. The lower speeds require a shallower blade angle to get the air and vehicle moving. This means the rotational air flow is more perpendicular to the intended direction of the aircraft at lower speeds. Consequently, the stator blades cannot be too close to straight at lower speeds, otherwise, the rotating prop wash will smack them, causing turbulence. Directional flow correction provided by the stator blades is accomplished by mirroring the angle of the propeller blades in relation to the axis. Both sets of blades will get increasingly straight-looking as air speed increases. This genius concept is the moment we’ve been waiting for!

[@jacquesparadis6756]

@@Yeshua-Is-Lord-7 Brilliant explanation! Thank you! I understand from your explanation that tying to fully compensate (redirect) the helicoidal air flow at lower speed would be detrimental to performance. The stator vanes would absorb to much energy bringing the ship to yaw. Counter rotating engines could solve the yaw factor but at the cost of loosing dynamic efficiency.

[@Yeshua-Is-Lord-7]

Thank you! My guess is the stators maintain around a 15 degree greater pitch angle relative to whatever is the propeller blades’ angle. The stators just auto adjust at this 15 greater angle of attack to improve the straightness of flow. Although not complicated, it’s hilarious that it took over a century of aviation for anyone to think of this. I certainly didn’t. Face palm.

[@jacquesparadis6756]

@@Yeshua-Is-Lord-7 Sometimes, when things are to obvious, we go right pass them without noticing ;-) Thanks for the exchanges...🙂

[@keithfreitas2983]

Worked for MDC in Long Beach as one of the Licensed Aircraft Dispatchers and the UHB was one of the programs we supported in Flight Test / Production. The UHB was based in Long Beach initially, then went toYuma AZ continuing the flight test program. Main pilot on that program was Captain Phil Battaglia. Great pilot.

[@Gabepedaler]

Always so informative and easy for us laymen to understand! Thanks P

[@sleeplessindefatigable6385]

Okay, if nothing else, the livery on that Embraer plane is absolutely gorgeous and I wish more planes looked THAT pretty.

[@nick9277]

What’s the thoughts on safety then? I know we have prop planes but I’ve never seen them with bird strikes or something of that nature. How would this be different if it’s a turbo fan without a shroud, what stops it from hurling itself into the cabin where the other just guts itself and sends parts out the back?

[@jerseymetalmike5111]

I specifically remember an air disaster (Southwest 737 in 2018) threw a blade killing a passenger; fortunately, the plane was able to land safely. In this case the nacelle was unable to contain the blade failure. It makes me question whether it's possible to protect the cabin, avionics and fuel tanks on this new propfan design, with it's larger blades, from a blade failure.

[@johnmorrison2226]

The story of GE's 727 was quite interesting. Being cost conscious, GE sought out the cheapest aircraft that they could find. The found an abandoned 727 in South America that was home to some monkeys. After performing the minimum amount of maintenance to get the plane to fly, the 727 was flown to the US. Once the pilots landed, the entire aircrew refused to get back in the plane, as they thought it was too dangerous to fly again.

[@miscbits6399]

That's rather fitting for a company founded by Thomas Edison

[@brodriguez11000]

Sounds like a Madagascar movie.

[@horai1]

This seems to be the biggest advances in a very long time and if it pans out it will be incredible. Thanks for a most informative video on the subject.

[@grizzlygrizzle]

This kind of innovation demonstrates the kind of human adaptability that indicates that Bjorn Lomborg should be taken more seriously on climate issues than the moral underwear-skidmarks meeting in Davos, whose underlying motive is to use climate panic to implement centralized global fascism. -- Censorship kills honest peer review, which kills scientific advancement. And incidentally, it often results in mass murder. Davos is the epicenter of evil on Earth.

[@Breenild]

It would be nice to know the advantages/disadvantages of a pusher model compared to the traditional engine mount!

[@arg31ify]

As the planes come in nose up and the engines are really far forward of the wings they're quite clear of the ground. A big pusher engine and prop would be very low to the ground on landing and take off and probbaly need much higher and heavier landing gear

[@kenoliver8913]

The big problem with pusher designs, right from the dawn of aviation, has always been avoidng the disturbed airflow from the wings which can drastically lower propeller efficiency. If on the tail you have to put the engines high up - but this tends to push the nose down, which can be dealt with but may lower aerodynamic efficiency. It also complicates maintenance. Careful design can minimise these problems so you get the advantages of pushing rather than pulling (including leaving lots of the noise behind) - but only minimise, not completely remove, them.

[@ryanaegis3544]

Pushers historically have overheating problems, as they do not have sufficient airflow over the engine to cool the engine except in flight.

[@Gremlack13]

It’s good to know that turboprop designs reinforce the fuselage. I was recently seated at the prop of an atr in India. Wondering deeply what would happen if the crop came apart.

[@drumnotdrum9262]

You get a free shave and complimentary underpants.

[@roichir7699]

It will kill you. These reinforcements are there to handle ice flying from propeller blades, not the blades.

[@miscbits6399]

You wouldn't know about it when it happened I won't sit on those rows. In the case of even a mild wingbending incident it's almost always where the first (or even only) fatalities happen. 3 people I know died that way when a Dash-8 crew got so busy trying to get gear down they forgot to pay attention to altitude

[@roichir7699]

@@miscbits6399 Which accident was this?

[@miscbits6399]

@@roichir7699 Ansett New Zealand flight 703, 9 June 1995

[@michaelscanlan8188]

I was in Long Beach CA when MD was flight testing the MD- 80 with the open prop-fan on one engine. The noise was tremendous, kinda like 1000 chainsaws gone wild. Would never pass any noise restrictions. Maybe next time.

[@freeculture]

That's long in the past, these new things are much quieter, same as other current jet engines. The first plane designed and manufactured to take advantage of this engine is going to change the industry (Is it the Embraer?). It may be more practical to go back to rear mounted engines, even if its not strictly needed, i can see the benefits of having more ground clearance during ground operations and take off landing.

[@PersimmonHurmo]

Why use a stator vane behind the front fan if it doesn't do any compression? It just adds extra resistance. Is it because of some aerodynamic or turbulent properties? We did use stator vanes behind turboprops. Seems really weird.

[@zapfanzapfan]

Interesting idea with a variable stator instead of a second fan. I saw another interesting idea a few years ago from what used to be Volvo Aero having the blades of the second fan being loops to prevent noise from tip vortices. Hope they make something with that.

[@kenoliver8913]

Wouldn't it be simpler to have miniature winglets on the end of the propeller?

[@zapfanzapfan]

@@kenoliver8913 I think that was the inspiration for the idea, the loop makes it sort of an infinitely long winglet.

[@oystercatcher943]

This is really fascinating and exciting to see, with a beautiful new design and significant improvements in fuel efficiency. btw. watch out for Scott Manley who it branching out from space into aviation. I think there is space for both of you excellent producers!

[@MrRexquando]

The dynamics problems haven't changed. The reason the TU-95 is limited to 350KTS because of the increasing aerodynamic penalties on the prop spinning faster+incoming air speed. While a 737 is typically at 460KTS. There is a loss of efficiency and exponential torque required above 350KTS equating over 1 hour longer on a trip from Miami to Chicago. Additionally the high by-pass turbine is more efficient in the thin air at 410000 feet where the weather will always be smoother.

[@Rrgr5]

You mentioned Tupolev, they actually had a ducted version of that engine as a propfan, the bypass is ridiculously large, and as it seems the engine was indeed good, problem was, the USSR collapsed and the project was abandoned, still amazes me how ridiculously large those were.

[@Янус_Ырт]

Nah, it was continued in Russia, but them closed, due to high levels of noise and abundance of airframes that can carry it

[@Rrgr5]

@@Янус_Ырт D-27? Yep, it was revised, they changed some stuff to make it more compliant with the noise levels, but I'm talking about the NK-93, the ducted propfan.

[@Янус_Ырт]

@@Rrgr5 NK-93 is also too loud

[@Rrgr5]

@@Янус_Ырт I still think the problem is the gearing, without the tips and ducted the engine should not make that much noise, I think that's the reason why CFP abandoned the counter rotating props, the GE one had a counter rotating prop moved by thrust because of that.

[@Янус_Ырт]

@@Rrgr5 even ducted, it still was above levels of noise, allowed by regulations, sadly

[@Aleksandr_N]

Hey, but what is intrinsic difference of these “revolutionary” new engines and good old turboprops? Same hot core, same rotating blades (a bit wider and more by count)

[@13374me]

It’s a fan blade shape, not just more of them. They focus more on air movement in general rather than thrust specifically, so they induce a lot more swirl or rotational energy into the airflow. This is why it has the stator blades in a second row, to take that wasted (in this case) energy and regain efficiency by converting it into a pressure change.

[@Aleksandr_N]

@@13374me thank you! Btw I saw similar shape of the propeller blades on Airbus A400 ...and some submarine

[@eottoe2001]

I was working near CVG in the 1980s and happened to see the plane with the GE-36 engine. It wasn't much louder than regular jets. It had a different sounds than jet or standard prop plane. If that is the same plane, I was told that prop flew off and hit ground in Indiana somewhere and that stopped the program. TY for the video.

[@pauljs75]

Something similar to this has been used to update a lot of turboprop aircraft. Those used by the U.S. military seem to have changed to this with various platform updates within the previous decade or so. They don't seem to have the noise issue concerns like that of jets, where ducted high-bypass fans still seemed to be preferred.

[@itsmebatman]

The Soviets even turned that Tubroprop bomber into a civilian airliner and had it fly from Murmansk to Cuba. Imagine being on a cruise ship somewhere in the Atlantic and that incredibly loud thing would fly over. That must have been a bizarre experience.

[@awuma]

The Tu-114 was both successful and had a good safety record (unlike a number of Soviet aircraft). It was succeeded by the Il-62, a Soviet take on the VC-10, with a bad safety record (Polish Airlines LOT lost two around Warsaw in the 1980's due to uncontained engine break-ups).

[@thisaccounthasbeensuspended]

@@awuma it wasn't a take on the vc-10. Both Vickers and Ilyushin had similar design tasks so they just happened to make the most fitting configuration

[@Skyfighter64]

Considering that most jets of the time were Turbojets, I would actually guess the Bear bomber, and subsequent developments of it, were actually very much on the quiet side of 1960's-1970's large aircraft.

[@eadgarswainsbury2738]

The Bristol Brabazon was first flown in 1949 and had contra rotating props. As did the Fairey Gannet also first flown in 1949.

[@fritzwrangle-clouder6033]

And the Metrovick F5 open rotor development was underway in 1945 and I think there was a proposal for an open rotor engine a couple of years before at Armstrong Sisdeley by TP de Paravicini.

[@tommytwotacos8106]

One of the really nice features on the Fairey Gannet was the ability to shut down one of the propellers and maintain altitude on just a single set of blades. This was done as a way to conserve fuel and was accomplished by separating the engines that drove each prop. That plane was ugly as sin, but it sure got the job done and didn't cost too much while doing it.

[@MarinCipollina]

Thanks for this timely episode, as I've been curious as to your take on this design since you teased it during the future plans for Boeing episode, as you referenced in this one. I find all of this quite fascinating, the journey should be interesting.

[@seldoon_nemar]

If you ever want to know what happens when you push propeller tips past mach 1, look up the XF-84H "thunderscreach". the propwash hits the ground and the supersonics turn into subsonic waves and they would cause everything from ground crew to pass out, soil themselves, and have instinctual fear caused by it, along with cracking glass and concrete. Someone did a re-creation of what one would sound like at 17,000ft and it would still be 101 db at the ground, as a howling screech. It had a top speed somewhere been 520mph and 670mph... with a single prop.... it's basically a war crime with wings at that volume...

[@347Jimmy]

Provided your troops had ear protection, training to get used to it and a heads up, that would make for the greatest air support ever

[@joeh8784]

@@347Jimmy Ear protection would not be enough. That level of subsonic waves vibrates bodies as a whole, shaking internal organs and the rest of the body.

[@347Jimmy]

@@joeh8784 that's what you would train for The ear protection is just there to keep from going deaf

[@joeh8784]

@@347Jimmy That kind of subsonics is not something you can train for

[@347Jimmy]

@@joeh8784 whatever you say 🤣

[@Fazeshyft]

My dad did work on the GE36. That design always fascinated me.

[@jacobmoses3712]

I'm glad you mentioned the Bear bomber. Even now it's a demonstration of how far you can push a turboprop. Much more efficient in fuel use than a B-52

[@mandandi]

Wow! Imagine this engine being of the right size for an A380 NEO! I know the A380 is discontinued, but its good to dream sometimes.

[@AsbestosMuffins]

I had the pleasure of touring their Evansville plant some years ago, they had a display of the GE engine

[@loveisall5520]

I still miss the 727 and the various DC9/MD80 variants. I really liked the rear engined powerplants, always wished I could have flown on a VC10.

[@adrianpeters2413]

The V.C.10 to this day is the only air craft ,that , I felt just wanted to fly by design... went up to 53000 feet ( military version , can see the curvature of earth ) , no problem, and up front it was so quite, and smooth ... the only reason that this design was not carried further on .....was....service / acessability of the installation of engines ( 2 side by side pods at rear) ..sorry you never will experiance this ...as the old saying goes ...if it looks correct ,it usually is ....note I am ashamed at never flying Concorde ,my greatest regret in life ....period .....

[@loveisall5520]

@@adrianpeters2413 Yeah, I started flying on business in the early 80's for the next 30 years. Lots of 727's flying back then and I loved them. Lots of SW Airlines 737-200's as I live in TX but also lots of DC/MD's also. But then, I still love the look of Goldfinger's Jetstar!

[@adrianpeters2413]

@@loveisall5520 yeah , the rear engines design was absolutely the best ,

[@kadabarVIM]

I can already imagine the A320 "newer engine option" and B737 "next-next generation" family line

[@vbscript2]

I kind of doubt there will be another generation of 737. I think it's more likely to be replaced by something with a transonic truss-based designed.

[@toriwatson9655]

I find it very interesting that finally a propfan engine might go into production. I must be missing something, but I can't quite understand what the second non rotating propellers are doing? Also would the new quiet Toroidal propellers work with turboprops or prop fans?

[@marlinweekley51]

Question: do these props/blades throw up more (runway/ramp)debris? And is the debris directed toward or away from the fuselage? 🤔

[@happyhalfwit8862]

Excellent video. This was all first announced back in 2010ish where Airbus an Easy jet proposed developing the rear engined shape for them . Speed figures were exactly as you mentioned with Vmo .82 Ceiling 42000 approximately. Of course very cheap fuel for the decade basically killed th project but am glad to see it back on the table. Interestingly the PW150a is actually deemed as a non ducted fan though i would actually call it 13.5 feet of noisy Ba*$£rd.

[@ElectricUAM]

Great video. Embraer already worked on unducted propellers similar to Safran's in the late 90s. One question, why are the second fans not spinning? ;)

[@AndrewTubbiolo]

1st gen jet transports were freaking loud. The noise was so intense that as a child I'd always leave a flight with my ears ringing from the intense noise. I'll never forget my first 757 flight. What a revelation. So quiet and the climb rate so steep. For the first time I got pressed into my seat in a big way. Shortly after that I flew in a new 737 and knew Boeing had really improved things. But I have to say I preferred the DC-10 to the 767. 767 is a great plane too.

[@jeanettewest]

The props are beyond loud, they are in a new category even. Back in the '80's when the Soviets would regularly skirt U.S. airspace over Alaska (I live along the coast of Southwest), the F-15 interceptor pilots noted the Tupalev prop noise was obscene. And these men were in a jet a couple hundred yards from the bomber, with a tightly fitted flight helmet on, let alone only a few feet away separated by only a sheet of aluminum and some insulation. Hope it works.

[@cryolabs]

I have always wondered why there is only one rotating propeller and not three possibly counter-rotating inner cores since the outermost edge of the propeller is rotating at a much faster speed than the inner core of the propeller. So if the propeller was 7 feet in radius it would be divided by infusing a second propeller within the 2.5 feet to 5.5 feet possibly counter-rotating within the outer faster moving propeller blades extending from 5.6 feet to the outer edge of 7 feet and another inner core which extends from the center of the propeller to the second counter-rotating blade extending to 2.4 feet. This way the innermost core propeller blade can rotate at an exponentially faster speed than the second blade blade which can rotate at 12x faster than the outermost blade allowing a steady air flow rate throughout the surface area of the propeller and possibly increasing it's efficiency?