Why Doesn't The GE9X Have Chevrons?
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- เผยแพร่เมื่อ 21 ก.ย. 2024
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Also does anyone ever read this stuff? If so let me know by telling me a joke in the comments section (airplane jokes preferred but not required)
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The Boeing 787 has a bold design. With it’s raked wingtips, aerodynamically contoured nose, and flexible wings, its elegance is unmistakable. But arguably its most distinct feature can be found on its engines, which sport a sawtooth pattern on their trailing edges. The 787 was the first commercial jet that saw widespread adoption of this feature, and over the years it’s found its way onto other Boeing jets - including the 747-8 and the 737max.
It was no surprise, then, that when Boeing launched the 777x, its engine - the GE9x - also sported serrated edges. But a few years into development, Boeing quietly removed this feature from renders and promotional material. And, sure enough, once the 777x made its debut, they were nowhere to be found. So, why would Boeing start rolling this feature out across their entire commercial lineup, only to remove it from their latest flagship? Let me explain…
#Boeing777 #GE9X #GE90 #777x
Did I accidentally swap the words "compressor" and "turbine"? You bet! Always remember to proofread, folks :)
how DARE you make such a mistake! You should be have you channel banned! lol 😂
I believe you also swapped the words titanium and inconel . Titanium is heat resistant enough for aircraft firewalls and components that separate the engine from the airframe, but it cannot take exhaust levels of heat for more than a few hours before developing metallurgical conditions of alpha-case and hydrogen embrittlement. Which as the name suggests, weakens the metal. I don't know about other manufacturers, but I know Boeing likes to use inconel-718 as the metal choice for exhaust ducting.
I hope I don't sound like a dick correcting you, I am instead hoping to share some information and maybe make you curious enough to learn more about these kinds of metals and their applications. Cheers!
rolls royce new engine with blue fan blades???
Alcino Vilela Belluzzo Filho this joke will be outdated in a few months once it’s flying again.
@@alphamalegold Air is not compressed in the high pressure turbine. Air is compressed in the compressor. In fact compressed air after combustion drives the High pressure turbine ( turbine blades).
Titanium is not very heat esistant material and its alloys, Alpha, beta and alpha + beta are not very heat resistant. They are considered semi high temperature alloys and employed in the applications when the so called homologous temperature is about 0.5. TiAl must also be used which is of very good oxidation behaviour but again is not high temperature structural alloys.
You meant nickel based super alloys which are structural alloys and employed in high pressure turbine. The "operating temperature" of the Nickel based super alloys is somehow around its melting point , sometimes higher , due to its oxidation behaviour, alumina formation, and TBC.
Some
I asked this same question back in 2018 to one of the chief test pilots for the GE9x, Jon Ohman. This was his response: “The chevrons seen on the nacelles of (the GEnx and LEAP-1B) reduce noise, but with a slight drag penalty. The use of new ceramic matrix composite materials on the GE9X allows us to do some things with combuster hardware to meet our acoustic requirements without a drag penalty.”
With that answer, I think a mixture of theory two and three is the correct answer to the question posed in the video.
Thanks. Saved me 10 minutes of my life.
Thanks bro!
Welp, I was 7 mins in when I started reading comments .
So he was right in his theory .
I think the Chevrons look cool and more futuristic, giving the plane a better look .
But the chevrons do look pretty sexy though
Engines with chevrons looks so cool.
Yea they really do
Oppie
Agreeable
I know. when I see other engines now they look boring and outdated
My question is…. When did DreamLand get wi-fi access?
Coby, you need to make a flight review channel. It can be called Coby Complanes :D
Haha love this, the last review he made was pretty complain-ey
That’s actually such a good name
Hahaha love it. Got any ideas for a potential flight sim channel as well??
@@cobyexplanes How about Coby Re-Planes xD (like replays, or reviews) sorry it's not my mothertongue haha
First review on a 747-8 to FRA plz
@@Lukatz Ive actually been thinking of doing that - I really want to fly on the -8 before they're all retired
My guess is that large bypass ratio makes the engine quieter. The GE9X engine has larger bypass ratio and less number of fan blades which already makes the engine quieter that renders chevron nozzle unnecessary.
This makes waaaaaay more sense.
Exactly this was my guess as well.
I was thinking the bypass and larger diameter also make them less effective.
@@yolo_burrito As bypass ratio (BPR) increases the overall efficiency of the engine increase which is a primary factor that yields lower TSFC for the turbofan engine. Additionally high bypass ratio engine can produce a greater amount of thrust while consuming the same amount of fuel as a lower BPR engine. Basically the additional weight added by bigger engines is negated by less fuel consumption due higher BPR. The engine doesn't need to spin as fast as it would to create the same amount of thrust at a lower BPR.
eWorkx I probably should’ve been more clear. I meant it makes the chevrons less effective not the engines. The negligible improvement of the chevrons along with larger diameter and higher BPR makes chevrons less effective.
The 777x flew over my head at about 3000 Ft. It was descending on a right base to Boeing Field in Seattle with the power probably at idle. The only noise I heard was a very quiet swishing sound probably from airflow over the air frame and engines. It was so quiet that I was startled when I looked up and saw this really large airplane so close. BTW, the reason for the quiet treatment on the engines is for noise reduction as perceived from the ground. There are lots of noise restrictions around airports around the world particularly at big city airports where this large airplane will operate. Boeing would love to be able to gain noise exemptions for landing during "quiet periods" at some place like LHW.
I am really wondering if Boeing wanted a 777X or an A380neo/747X
You didn't hear anything because it was descending. It's already the case of most airplanes nowadays : you don't hear anything when they are descending at idle thrust.
@@noah9130 Protruding landing gears do create massive turbulence though, which should create lots of noise. I haven't done plane-spotting for a while now, and I clearly did not pay attention to the noises landing gears on inbound planes made during my last spot. Would love to do further comparisons on noise levels between outbound and inbound flights in the future.
@@paulshi5974 That's true. I live 5 miles away from an airport and when they are flying above my house at fast speed like 180 knots with their landing gear deployed, it creates a lot of noise especially when they are deploying it right above my house.
@@noah9130 Wow you can actually hear the moment landing gears deploy? I honestly don't know how to react haha. For one thing that's some perfect timing for ya, but I don't know if hearing landing gear noises every day has driven you mad or not...
787 without Chevrons will look way less beautiful
I couldn’t even imagine...
No duh. Its not even a 787 then
Chengyou Jiang the chevrons do look pretty cool, the 747-8 GEnX engines even cooler with the exhaust scalloped as well
If there was a plane with the face of an A350, and the wings and engines of a 787, that would be amazing, with the APU outlet of a 777.
I don’t think so. Looks cooler with the chevrons, yes. Still a beauty airplane.
I flew 787-8 and it was very comfortable, the cabin noise is a lot lower than in older airplanes. It was one of the best flights Ive ever made and it was a 12 hours flight!
Can’t be that it’s expensive. Would have made it uneconomical to put on the 737 Max. GE doesn’t build the nacelle. Boeing/UTC designs them, UTC builds them. This is the first thrust reverser that Boeing is fully designing and then building with Spirit. Could be the result of a closer collaboration of between GE and Boeing on propulsion integration.
Exactly, it would only add slight cost to the aircraft in general. They aren't even replaced when the engine is replaced. They're just part of the reverser doors.
Boeing usually does the engineering but, in the case of the 787, Rohr, Inc. (owned by UTC) put a decent percentage of a billion dollars into the the design and tooling for the 787 nacelles for both the GE & RR engines (at the same time they had the engineering group for the A350 nacelles working on the next floor down in the same engineering building.)
First time I flew on a 787 the takeoff engine noise inside the cabin was so low that I was worried the pilot hadn't throttled up the engines sufficiently and quickly started verifying the closest emergency exit location.
The engine sound at full throttle reminded me of the sound of a vacuum cleaner.
clrd4tkf the same thing happened to me except i got out of my seat and started opening up the cabin door screaming “we are all going to die!!!”
I like the 757 at takeoff, you hear and feel that power, like a race car.
@@mytech6779 I think the 757 is what happens when the fighter design group gets bored and designs an airliner. :) Personally, though, from a sound perspective, the GE90 is my favorite engine spool sound.
As far as being surprised at the lack of sound on takeoff, this is also my experience with the geared turbofan on the C-Series (now A220.) Those things are amazingly quiet, even when sitting right beside the engine at takeoff power.
I've been on both the 747-400 and 747-8I, I can clearly hear the difference in cabin noise induced by the engines.
But how much of the difference is the chevrons itself vs the fact the GENx is 20 years newer?
CF6 vs GEnx. Not a fair comparison regardless of chevrons.
The difference is because of the difference between difference in bypass ratios of those 2 engines rather then chevrons.
Agree. The fair comparison would be the B787 vs the A350 or A330neo.
@@youngtimer964 could be rolls royce or pratt & whitney engines too than the ge cf6
No one:
Literally no one:
Coby: let me explane
Bad pun...
@@classicjoker2008 If you're saying bad pun for the "explane" that's literally what this channel is called
C-
You tried.
I did not know that I need to know about chevrons until this video :D
Lame meme.
This hurts my head. GE makes the engine not all of the composite structure around it. Just like the classic 777, Boeing designed the Nacelle. Boeing built the 777 Nacelle in Wichita.
That same facility builds the 777x is now Spirit. Boeing designs the Nacelle to meet specific noise requirements. Once the requirements are met, you keep the design as simple as possible. K. I. S. S.
Chevrons? I call them Shark teeth. !:- )
Bio mimicry
I do agree
And rightly so!
I was on a flight with the 787 and then my connecting flight right after was a 777. The difference was pretty great with the 787 being much more quiet.
Well explained... and produced! Good audio, including non-intrusive music, voice level and great video clips.
I think I've only been on one 737 with chevrons. Screaming babies on the flight cancelled out any noise reduction of the engines.
Glad you enjoyed :)
I agree, 787 takeoff was so quite. I also flew 737 Max on Southwest, very quite also. I kind of miss the loud engines at takeoff, though. My first jet flight was an Eastern Airlines B720. Such power & noise. In addition, I love the 757 takeoff power.
Some of this is down to the runway and initial climb slope. They calculate the minimum power setting needed for a location and gross weight to avoid stress on the engines and get longer life. A long runway followed by a good clearway with dense air and low fuel(short flight) can call for a very low takeoff power. The 757 was designed specifically for medium haul from difficult airports with low density air so it has extra power available. The MAX and 787 did not have this design target.
@@mytech6779: Actually, the 757 is my favorite plane as a passenger, reminds me of the B720, which was also designed for shorter runways & smaller airports--from what I have read.
787- I flew on....was by far...and I mean BY FAR the quietest ride I've ever been on. Even on take-off, I could hold a conversation at normal volume. That blew my mind.
The mixer thing, as he pointed out, makes no sense given that it's an unmixed design. Overall the outer nacelle chevrons aren't because of mixing between core and bypass flow, it's bypass and ambient flow. My understanding is it's not about temperature so much as velocity, fast air coming out and mixing with slow surrounding air, with a shear layer, makes the noise, and chevrons help to break up that shear layer and cause quicker, thus quieter, mixing between the fast and slow air. The slower the bypass air, the less this is needed, which is why high-bypass turbofans are quieter than low-bypass or turbojets. As others point out, maybe the bypass ratio is so huge, the outlet velocity so low, that they just aren't needed. The other possibility, somewhat related to the mixer idea, is that there's some other technological solution being used instead. Maybe something secret (trade secret, not as in classified) which is why Boeing and GE haven't made the reasoning public.
Its possible that the ge9x exhaust outlet, with its almost rounded octagonal shape, does the same thing as the chevrons for less drag penalty.
No u are wrong
Nope
I flew on a 787-9 and the noise reduction was extremely significant. Made the whole trip more relaxed. Easily the quietest plane I have ever flown on.
Yes I have flown onboard the b787 the engines aren't noisy during take off and landing
Same with 737 max
Much quieter than a350
I have also flown on a 787, it was a Boeing 787-9 and it is not that loud during takeoff and landing
alaska airlines 001 I was on an a350 and 787 back to back and 787 was much quieter during takeoff
@@AntonLoves737 are you sure which airlines
Always a pleasure watching your videos. I've flown the 787-8 and 78-9 and I must admit it is a very "silent" aircraft.
I've been flying airliners for over 30yrs, and I have to thank you for your proper use of terminology and clarity in explaining the subject matter. There are many TH-cam content producers that can learn from your high-level graphics and proper nomenclature.
I saw the 777-9 takeoff from the Yuma Arizona airport while standing just outside the FBO. It's very quite, especially compared to the other jets flying in and out of there. Don't think it really needs the chevrons.
Hi Coby, just flew in a 737 Max-9 from Iceland to Seattle. It was the quietest and smoothest flight I can recall ever having.
Nice .. I like the Chevrons :) wish they werw continued in the 777x too
The mixer sits where...?
Glad someone else heard that
@@koenbaglien5276 I guess it's easy to mix up(no pun intended) compressor and turbine. But still they do very different tasks!
... somewhere in the cabinet under the kitchen sink.
01:32 is also pretty bad :’)
@@HermesBird11 Why? Seemed pretty accurate to me.
Well, I have been on a 787-8 once before, and I can definitely say it is VERY quiet in comparison with other aircraft, such as the 777 or 767, even the A350.
Good question
- Shrek
If you look at the GEnX on the 747-8, the primary exhaust is also scalloped
Excellent video. Thanks for taking the time to film and edit it and of course for positing it for our benefit. Keep up the good work! -Migs
Finally someone talked about the B777x chevrons! And tbh i got to the same conclusions but i heard(i don't remember where) that the chevrons make the engine 2% less efficient, and on a plane like B777 this would be a big problem.
Having flown on a 747-8, the plane was easily the quietest I've been on. The normally loud roar on takeoff was a dull rumble and during cruise, you couldn't even hear the engines over the air conditioning. My guess is that the GE9X was "good enough" in terms of noise, and adding chevrons offered no significant noise benefit, so they cut them out for the slight drag reduction.
You should try flying on an A380 or A350 bro
This question is always in my mind. Thank you for explaining this!
You mean his theories
@@tripleceven no, i always thought why ge9x doesn't have cheverons
@@alaybey9771 you said thank you for explaining this like what he said was factual. He clearly said they were theories.
@@tripleceven well, this is some sort of explanation
@@alaybey9771 i see
i flew on a Virgin Atlantic Boeing 787-9 from LHR-JFK last month, then returned on a Delta Boeing 767-400. And in 2016, a Virgin Atlantic Boeing 747-400 from LHR to MIA, and returned on the exact same plane. On takeoff, the 787 was significantly quieter than the 767 and the 747, but, the 767 and 747 brought much more excitement to me and was more fun overall. i think that chevrons are effective, but planes that dont have them are better imo, just because of how loud the roar is on takeoff
I flew on both A350 and B787, both times sat near the trailing edge of the wing. The 787 was definitely quieter. But I like the A350 better..
Think it depends allot of where you are sitting, I found the A350 to be more quiet, and I just got the feeling of it being cutting edge, The 777 Is so noisy it's insane, but I can live with it because the engines are so impressive, esp starting up.
Flew round trip on Air Canada, YVR to Incheon/Seoul in 2017, and those 787-9 were VERY quiet and comfortable in Premium Economy. Fantastic flights!!
Boeing jets aren’t the only planes with Chevrons. The Embraer 170-195 have hot section chevrons and so do some CFM equipped A320 series aircraft.
Right. The Boeing ones are the only ones with the more distinctive chevrons on the nacelles, though.
That is wrong but very close
Amazing to think Geoffrey De Havilland was trying similar noise reduction measures on the Avon's in the comet 4 nearly 70 years ago.
They were fluted jet pipes rather than chevron on the cold section but same idea.
Hi, I think you got mixed up between compressor and turbine, at 1:37 you mentioned that air go through turbine to be compressed and mixed with fuel which is wrong, air goes through compressor first to get compressed then it mixes with fuel and ignition takes place, later in the clip , at 5:35 you said “mixer sit behind the high pressure compressor” actually you meant sit behind the turbine
i was going to say the same!, it was not the turbine, it was the low and high compressor
Yep you're right, this is why you always ned to proofread your work! lol
Actually my dad helped design the engine and he said that they don’t have chevrons because the nozzle is a whole different design from like the 787 or 737 max
@@InForTheLonghaul because that is how far technology has come ;)
Adding chevrons on the GE9X would have reduced its thrust and Boeing didn't see the need. This is actually the reason as to why Airbus planes have no chevrons
Also don't forget, the Embraer 190 has some small chevrons on its engine exhaust.
I've seen chevrons on the Antonov 124
@@aarondynamics1311 yeah that too
Actually some A320s with CFM engines have chevrons (it's hard to see but they do).
Chevrons are designed to enhance mixing between the different flows and not to smooth the flow. Forced mixers are only effective for lower bypass ratio engines and become too heavy on large engines and ineffective at high bypass ratios. They are typically fabricated from sheet metals and are not as expensive as you may think. Chevrons were originally intended to reduce community noise (what the people on the ground experience). The B787 Chevrons are aimed at reducing shock cell noise in flight which is caused by shock waves in the exhaust flow interacting with the shear (mixing) layer which can then propagate upstream and into the cabin. Composite fuselages are not good at attenuating noise created in this way and either you need to reduce the noise at source (disrupt the shockcells in the flow) or absorb the noise. The Chevrons on the B787 are not very good at reducing noise and increase fuel burn due to the drag on the Chevrons from the high-speed flow on the inside of the nozzle. They also change the amount of flow through the nozzle at low pressure ratios which is bad for the fan. Based on experience of Chevron design and testing, it is more effective to add sound absorbing to the fuselage than add a fuel burn penalty to the engines. So, answer 2. A competitor to Boeing doesn't have Chevrons on their nacelles for this reason. Shame really, the aerodynamics are interesting!
An aerodynamicist who worked for years on Chevrons and forced mixers for an engine manufacture.
5:38 "..not only are these materials heavy and expensive.." - isn't titanium actually quite light, considering its strength?
It's much lighter than steel but much denser than aluminum. I'm sure it would be some alloy, and that makes it hard to know what its weight would be. But it wouldn't need to be super strong as a mixer, just heat resistant.
@@CodeKujo Exactly. And it's gonna be thick, too.
787 is so quite its my new most favourite plane, the noise so low, the lighting is futuristic, the cabin is amazing and looks brand new every time. Really the best plane for flying.
*quiet
I must agree with KP Barbee. The A350 is quieter than the B87.
Someday I hope to fly on the A380 and can see if that aircraft is as quiet as they say in these posts.
I have been on the Qantas Dreamliner, and you can barely hear the engines when inside the plane
Mixers don't sit behind the high pressure compressor. They sit behind the low pressure Turbine, which is a huge difference. The Temps are high nonetheless, so i get your point. (Edit: Spelling)
Coby, You are such a handsome stud! - I really look forward to watching your videos...you do a great job of making complicated things seem simple!.. P.S. I love bears!
I flew on a 787-9 for around 5 hours. I'm not sure if it's because I don't fly often but, when the plane took off, I barely heard the engine spooling up. I took a flight a few hours after on a 777, and the engine sound was much more noticable. This was back in 2019, but I still remember it quite well.
I've been on the 787-8 before, and it's much quieter than the A330.
nah then
Generational difference in engines, my friend
Well d'oh!
That's like saying B737-800 is more efficient than B727. Obviously.
@@youngtimer964 GE CF6 to GEnx
Aviation Channel okay, and so you’re agreeing with me? CF6-80E1 vs GEnx-1B 1970’s vs 2000’s. Biggest difference relative to noise would be wide chord fan blades.
Thanks for your concern about sound quality and pronunciation, this makes it easy for a non-native English speaker to understand. Good job.
Before I clicked on this video, I thought the answer could be stated in 30 seconds. But you did a great (9 minute) job of explane'in the reasons 👍
It's not as simple of an answer as I originally thought. Before doing research for this video I thought it'd be 4 minutes tops but alas
Learn something every day. I always thought they were just decorative. Thanks.
Yes 789 I was on was really quiet was disappointing because I love jet noise!!
I flew on a Virgin Atlantic 787-9 overnight. I had never been able to sleep on a flight until then! Really made a difference
First 787 flight I took was on a Virgin 787-9 - I think I slept like 6 hours straight it was awesome
r..emember the old 707's they had something at the engine exhaust, that looked suspiciously like these "new" 'mixers'!
No those are the reverse thrusters
I work at Boeing in Everett right next to Paine field. We have planes taking off all day and night. The only ones you really notice in the building and go to look at outside at are the Dreamlifters and the random UPS freighter 747’s and C-17’s doing touch and go’s. The 67’s 87’s 777’s and X all sound the same from a quarter mile away.
Does this engine have a greater bypass ratio? If so, perhaps the resulting change in ratio between hot and cold flows creates less turbulence-noise.
Before Boeing, it’s the Embraer E series first use chevron’s to commercial flight. But it’s Boeing who first use chevron for wide body jets.
Pretty surprised you say that chevrons are on their way out. They wer introduced just 13 years ago,that is surprisingly young.
I live near the airport and often planes pass depending on which runway they are assigned to land. One thing I notice is, when a B787 is approaching to land the engine is a bit quieter compared to the common A320 & A330 that passes near our house.
They design for noise at takeoff thrust, that is where you will get the real difference.
I wish I had an airplane joke! 😅
1:49. Coby, the source says Safran, but the video is from Pratt and Whitney.
Simple it doesn’t need one for noise reduction
Right
I’ve flown the 787-8 twice and it wasn’t noticeably quieter than the 777 200ER or the 747 400.
also potentially the benefit of the chevrons is reduced as the engine size increases because of the reducing ratio of circumference vs. cross section area as the engine increases in size, so on the huge 777 engines it had more drawbacks and less benefits
737max I was on was not only the quietest I've been on, but the noise it produces was also far less "annoying". it is one heck of a plane
I found the A350 even quieter than the 787 to be honest.
This is the question I was asking myself. Thank you.
As someone who lives under the approach for Paine Field and Boeing Field, where they are testing the 777x out of (you can see it take off from Boeing Field at 4:20), I've seen the 777x fly over on a few test flights as it's departing, and I gotta say, it's really quiet for it's size. It's absolutely nothing compared to the usual ups and FedEx md11s, 747s, and 757s that fly over. Those will make my house shake and wake me up at 5am when they fly out. The 777x and the 737 max, back when they were testing it, are barely audible over the usual sounds of cars and such. So they definitely figured out a way to cut down noise without chevrons.
I appreciate the theories, you could have just included the T word in the title.
As a passenger on the 787, I thought it was a much noisier get than the quiet interior of the A350.
787 was definitely a lot quitter compared to 777!! N much more peaceful
I found the 787 quieter but more impressive to me was the smooth ride due to the flexibility of the composite wings.
Coby is always getting hotter. Love the cub beard😍
He's flippin’ adorable. Glad to see a perception that aligns with mine.
As a person who worked in design at the time of the new cowling shapes being introduced, from what I heard quietly, pun intended, it was implemented to cut decibels realizing the new much larger windows on the 787 would make for a smaller insulated area.
Weight is the most important thing besides strength/longevity/manufacturability/cost/serviceability... It's a balancing act. It was a fun challenge when I started in design, that if you as a designer were able to redesign a part or small assembly to shave 1 pound in two line numbers without adding any additional costs (ie It had to pay for itself in two planes) you got a 25k bonus. I only know a handful who have done it. That two planes without increasing the manufacturing cost is the challenge.
So everyone who takes a big sh!t in the airport is actually doing their part to reduce global emissions.
John Ohman (GE test pilot for the GE9x) confirmed to me on Twitter several years ago that the use of “the use of new ceramic matrix composite materials on the GE9X allows us to do some things with combuster hardware to meet our acoustic requirements without a drag penalty.”
I’m think theory three is actually correct.
I once asked this exact same question on a Boeing factory tour, and the guide said they found something better than chevrons, but it's a secret.
When you said the classic roar of a turbo fan I heard that from the nearest airport and when I’m writing this comment
Myself living in the Everett area! I woukd say the 777X engines compete with the noise level of the late Gruman A6 or EA6B's as something certainly had to replace them in the otherwise noiseless northwest skies! Easily the loudest jet engine produced in decades whether it be from its sheer size or otherwise its noise is at times is undeniable! Sometimes having you look for the ghost of an aircraft seemingly right on top of you when in fact it could possibly be just spooling up infact miles away, having them be that of deceptivly and incredibly loud engines indeed!!! They have proved to be louder than I ever would have imagined them to be, especially after as you said the technology and attention put into the mitigation of noise on the 787's and 747's most recent engines! These new engines are said to be the largest ever made as so may be that of their volume level maybe the largest level in all of commercial aviation! Substantally louder than I would have anticapated by far... Perhaps noise mitagation may be something Boeing and GE are planning on addressing at a later date, I do not know? I would have to say so far it has been completely over looked for of whatever reason that maybe! I'm sure one could be left to speculate with out specifity like you were here in this here video blindly speculating of different senerios as to what may see to be of plausable reasons for the ommission of noise mitagation as your guess is as good as mine. Lack of concern perhaps after spending of the time and effort to accomplish of amazing results in such a feild to then see to loose of interest or even acknowledge of its in anyway further need? I dont know but it certainly has one scratch of their head as to what is or may be going on, for sure! I'd surely be interested in of any information you may see to gleen on the subject! My suspect is that there may just not be any information to be had. Hence the noise level of the largest jet engine ever made seeing to have of the noise level that it does just being what it is! A product of the largest jet engine in the world! What else would anyone see to expect? Rendering it a non-issue, I guess... You said that GE's design made for a quieter noise level in itself and maybe it does but from my ears experience I would further guess that of any such thing went by the way side along with the cheverons, but i have no idea as to its design other than large and loud being of the present results!
My first flight on a boeing a/c was on a B738M back in Dec 2021. It was significantly quieter than any other a/c I had travelled in before. Then I had travelled in a B738 in April 2022, and boy that was loud(I enjoyed it more though). So ya, Chevrons really do make a substantial difference imo.
I flew a 787 for the first time in 2016, flying to/from Hawaii from Australia - roughly a 10 hour flight. However, I opted for the Economy Plus seats (directly behind Business class) which was forward of the main entry doors. I was incredibly impressed by the smoothness of the flight & remember a reduction in "flight noise". But it's hard to provide an objective interpretation when you're significantly forward of the wings/engines...
I've always wondered about that serrated engine design, glad to have stumbled on this 👍
Having flown on both, I feel the inside cabin noise is less on the Airbus A350s than the Boeing B787s. These are both quieter than all the other wide and narrow body jets I've travelled on.
I agree, but the absolutely quietest is the A380! Probably because it’s the most modern 4 engine plane.
FYI: you said, the mixer is made out of titanium for its heat resistance. But titanium is not heat resistant at all. Everything behind the combustion chamber is made of nickel base alloys. And they can be forged, bent and welded like steels can.
Also another theory is the following: I heard rumors, that Airbus also thought about chevrons but didn’t use them cause they couldn’t really find a big benefit.
My only experience is with the 787 so it's difficult to say, and that plane is significantly quieter than anything, bar the a350 (which doesn't have the chevrons). I need to try the 747-8i to give you a definitive answer:)
When I flew in an American Airlines 737 MAX 8 I couldn’t help but notice it was the quietest jet I’ve ever flown on! Way quieter that the older 737-800 I also flew on that trip so I think that Chevrons really do help… They also look so futuristic & cool!
Hey, Coby, can you answer a quick question? At about 4:18, I see "something" trailing the top of the vertical stabilizer, akin to a toy balloon being dragged along behind the 777x. I looked through some of the comments, but perhaps I missed a previous reply. Thanks!
4:40 yes there is. take the difference in drag coefficient due to the increase in AoA required due to the weight difference throughout the flight profile. Can be approximated easily in steady level flight, but there's also a benefit when climbing.
What a convenient video, cause I was just learning about mixers the moment I noticed them on base airplanes. The real curiosity came when I noticed Dassault Falcons had normal tubes when several American jets didn’t. Its crazy that sound dampening was what they are for, cause I always note how much quieter Falcons are compared to any other plane lol
Sitting front of the engine vs back of the engine is the right question with it . Where you sit makes a huge difference in the same aircraft .
Oh wait Mixers can also be seen on the back of the RB211s on the B747-400. I went to the HARS aviation museum and saw it for myself!
Forgive me if I’m confused. But what is stopping Boeing from canceling the noise out using speakers. Like turning the compressed cabin into a sound cancelled headphone
We don't want "reduced jet engine noise!" We (on the ground) love hearing a jet roar over. If the people living around the airports don't appreciate this beautiful sound.....they can move.
sitting behind the engines on a 777 then 787 on a layover. the 787 was significantly quieter and more confortable overall
2:10 "This mixing [of distinct co-axial hot and cool airstreams] results in a turbulent flow that produces the classic roar of a turbofan. Chevrons help to smooth this mixing of hot and cool air in turn reducing engine noise ..."
Way more 'splainin needed here Coby. Maybe a whole 10-minute episode on the thermal-acoustic phenomenon.
As a former employee of United I had the opportunity to ride a 777 and 787 relatively close together. Admittedly I didn’t notice a whole lot of difference in the amount of ambient cabin noise between the two. However, in hindsight, I can recall that my wife & I didn’t lean over our daughter as much to speak to each other in the 787 as we did in the 777. Maybe that meant it was easier to hear each other in the 787 giving the claim of a quieter cabin some credence?
Those Chevrons were probably causing excess vibrations that later lead to reliability issues. At then end of each of the chevrons is a vortex forming a curtain of vortices, overtime fatigue would set and cracks would probably start in between the "fingers" in. The fatigue probably occured faster or degree of was more than they accounted for and just ended up nixxing the chevrons all together when it came to costs keeping and dealing with consequence vs getting rid of.
I got to fly on a 747-8i with Lufthansa in 2016 from Frankfurt to Washington. The trip to Frankfurt was on a 747-400, and I could definitely hear the difference between the two planes!
There is also the competitor of the geared turbofan that both cuts inherent engine noise and also on paper reduces fuel burn. In a era of increasing fuel costs and emission reduction targets, airport engine noise is not facing the same pressure to cut local noise impacts. 3D printing is also offering the material weight reductions with composite materials cutting weight elsewhere (wings, tails, shell body). Pratt and Whitney have had big geared turbofan "challenges" but the value is there if you can solve it and up in the skies, you can always recommend noise cancelling earphone to passengers (forget the staff going deaf). Perhaps GE saw nobody else offering them. No sign of them on private jets where engine noise is even more noticeable. Until synthetic "green" engine fuel is mainstream, fuel burn will be paramount (and even more so once Kerosene is taxed like any fuel).