Why Doesn't The GE9X Have Chevrons?

Рет қаралды 639,390

3 жыл бұрын

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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

Пікірлер: 997

@cobyexplanes 3 жыл бұрын

Did I accidentally swap the words "compressor" and "turbine"? You bet! Always remember to proofread, folks :)

@alphamalegold 3 жыл бұрын

how DARE you make such a mistake! You should be have you channel banned! lol 😂

@OvoJeGovno 3 жыл бұрын

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!

@classicwheels4275 3 жыл бұрын

rolls royce new engine with blue fan blades???

@superskullmaster 3 жыл бұрын

Alcino Vilela Belluzzo Filho this joke will be outdated in a few months once it’s flying again.

@MrGhadnaz1 3 жыл бұрын

@@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

@andrewsamuelson3275 3 жыл бұрын

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.”

@andrewsamuelson3275 3 жыл бұрын

With that answer, I think a mixture of theory two and three is the correct answer to the question posed in the video.

@rogeronslow1498 Жыл бұрын

Thanks. Saved me 10 minutes of my life.

@Poop-nu1so Жыл бұрын

Thanks bro!

@zabercrombie24 Жыл бұрын

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 .

@reelmsy3831 Жыл бұрын

But the chevrons do look pretty sexy though

@samuelwhaley6658 3 жыл бұрын

Coby, you need to make a flight review channel. It can be called Coby Complanes :D

@pilotpeter8850 3 жыл бұрын

Haha love this, the last review he made was pretty complain-ey

@charliemolda297 3 жыл бұрын

That’s actually such a good name

@cobyexplanes 3 жыл бұрын

Hahaha love it. Got any ideas for a potential flight sim channel as well??

@Lukatz 3 жыл бұрын

@@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

@cobyexplanes 3 жыл бұрын

@@Lukatz Ive actually been thinking of doing that - I really want to fly on the -8 before they're all retired

@Waddle_Dee_With_Internet 3 жыл бұрын

Engines with chevrons looks so cool.

@jessenaber2648 3 жыл бұрын

Yea they really do

@ajb229 3 жыл бұрын

Oppie

@leMiG31 Жыл бұрын

Agreeable

@MrBibi86 8 ай бұрын

I know. when I see other engines now they look boring and outdated

@ericchen6096 3 жыл бұрын

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.

@giths19 3 жыл бұрын

This makes waaaaaay more sense.

@deth3021 3 жыл бұрын

Exactly this was my guess as well.

@yolo_burrito 3 жыл бұрын

I was thinking the bypass and larger diameter also make them less effective.

@giths19 3 жыл бұрын

@@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.

@yolo_burrito 3 жыл бұрын

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.

@chengyoujiang6076 3 жыл бұрын

787 without Chevrons will look way less beautiful

@alphamalegold1 3 жыл бұрын

I couldn’t even imagine...

@alphabravoindia5267 3 жыл бұрын

No duh. Its not even a 787 then

@MegaWingman7 3 жыл бұрын

Chengyou Jiang the chevrons do look pretty cool, the 747-8 GEnX engines even cooler with the exhaust scalloped as well

@schumi246 3 жыл бұрын

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.

@mikemontgomery2654 3 жыл бұрын

I don’t think so. Looks cooler with the chevrons, yes. Still a beauty airplane.

@wfviewer 3 жыл бұрын

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.

@alexibm2477 3 жыл бұрын

I am really wondering if Boeing wanted a 777X or an A380neo/747X

@noah9130 3 жыл бұрын

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.

@paulshi5974 3 жыл бұрын

@@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.

@noah9130 3 жыл бұрын

@@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.

@paulshi5974 3 жыл бұрын

@@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...

@claudioavia 3 жыл бұрын

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!

@samtobio3045 3 жыл бұрын

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.

@CheapBastard1988 2 жыл бұрын

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.

@ThatBoomerDude56 Жыл бұрын

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.)

@cshan2313 3 жыл бұрын

I've been on both the 747-400 and 747-8I, I can clearly hear the difference in cabin noise induced by the engines.

@pilotpeter8850 3 жыл бұрын

But how much of the difference is the chevrons itself vs the fact the GENx is 20 years newer?

@youngtimer964 3 жыл бұрын

CF6 vs GEnx. Not a fair comparison regardless of chevrons.

@hp2084 3 жыл бұрын

The difference is because of the difference between difference in bypass ratios of those 2 engines rather then chevrons.

@chingweixion621 3 жыл бұрын

Agree. The fair comparison would be the B787 vs the A350 or A330neo.

@_.twixxx Жыл бұрын

@@youngtimer964 could be rolls royce or pratt & whitney engines too than the ge cf6

@nimrodgicheru316 3 жыл бұрын

Yes I have flown onboard the b787 the engines aren't noisy during take off and landing

@AntonLoves737 3 жыл бұрын

Same with 737 max

@nickbien 3 жыл бұрын

Much quieter than a350

@Alaska_Aviation 3 жыл бұрын

I have also flown on a 787, it was a Boeing 787-9 and it is not that loud during takeoff and landing

@nickbien 3 жыл бұрын

alaska airlines 001 I was on an a350 and 787 back to back and 787 was much quieter during takeoff

@nimrodgicheru316 3 жыл бұрын

@@AntonLoves737 are you sure which airlines

@clrd4tkf 3 жыл бұрын

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.

@Johnny78674 3 жыл бұрын

The engine sound at full throttle reminded me of the sound of a vacuum cleaner.

@davidjames666 3 жыл бұрын

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!!!”

@mytech6779 3 жыл бұрын

I like the 757 at takeoff, you hear and feel that power, like a race car.

@vbscript2 3 жыл бұрын

@@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.

@vbscript2 3 жыл бұрын

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.

@pilotjelly1256 3 жыл бұрын

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.

@geoffbutler10 3 жыл бұрын

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.

@judeseton9232 3 жыл бұрын

No one: Literally no one: Coby: let me explane

@classicjoker2008 3 жыл бұрын

Bad pun...

@randomcontentgenerator2331 3 жыл бұрын

@@classicjoker2008 If you're saying bad pun for the "explane" that's literally what this channel is called

@BrianYYH 3 жыл бұрын

C- You tried.

@RadostinVelchev 3 жыл бұрын

I did not know that I need to know about chevrons until this video :D

@user-tt2fh8nf1o 3 жыл бұрын

Lame meme.

@ChrisJones-fm6wp 3 жыл бұрын

Its possible that the ge9x exhaust outlet, with its almost rounded octagonal shape, does the same thing as the chevrons for less drag penalty.

@Airplaneobseesed9937 2 жыл бұрын

No u are wrong

@cellokid5104 2 жыл бұрын

Nope

@jrwxtx 3 жыл бұрын

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.

@mytech6779 3 жыл бұрын

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.

@jrwxtx 3 жыл бұрын

@@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.

@KutWrite 3 жыл бұрын

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.

@cobyexplanes 3 жыл бұрын

Glad you enjoyed :)

@Migs3 3 жыл бұрын

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

@vieuxbal1253 3 жыл бұрын

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.

@a787fxr 3 жыл бұрын

Chevrons? I call them Shark teeth. !:- )

@brapa1190 3 жыл бұрын

Bio mimicry

@fethifethi884 3 жыл бұрын

I do agree

@michaelz6870 3 жыл бұрын

And rightly so!

@quillmaurer6563 3 жыл бұрын

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.

@brimopm Жыл бұрын

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 KZfaq content producers that can learn from your high-level graphics and proper nomenclature.

@cameronhoward99 3 жыл бұрын

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.

@dumbcow1 3 жыл бұрын

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.

@oliverllmills 3 жыл бұрын

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.

@RaynerGS 3 жыл бұрын

Thanks for your concern about sound quality and pronunciation, this makes it easy for a non-native English speaker to understand. Good job.

@javahedz 3 жыл бұрын

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!!

@blancolirio 3 жыл бұрын

The mixer sits where...?

@koenbaglien5276 3 жыл бұрын

Glad someone else heard that

@ozcarplayz1656 3 жыл бұрын

@@koenbaglien5276 I guess it's easy to mix up(no pun intended) compressor and turbine. But still they do very different tasks!

@matekochkoch 3 жыл бұрын

... somewhere in the cabinet under the kitchen sink.

@HermesBird11 3 жыл бұрын

01:32 is also pretty bad :’)

@1000CalorieSnackPack 3 жыл бұрын

@@HermesBird11 Why? Seemed pretty accurate to me.

@thespaceguy235 2 жыл бұрын

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.

@monibstar 3 жыл бұрын

Nice .. I like the Chevrons :) wish they werw continued in the 777x too

@itsReallyLou 2 жыл бұрын

I'm impressed! Very nice work. Thanks.

@alaybey9771 3 жыл бұрын

This question is always in my mind. Thank you for explaining this!

@user-rc9qi6yp6k 3 жыл бұрын

You mean his theories

@alaybey9771 3 жыл бұрын

@@user-rc9qi6yp6k no, i always thought why ge9x doesn't have cheverons

@user-rc9qi6yp6k 3 жыл бұрын

@@alaybey9771 you said thank you for explaining this like what he said was factual. He clearly said they were theories.

@alaybey9771 3 жыл бұрын

@@user-rc9qi6yp6k well, this is some sort of explanation

@user-rc9qi6yp6k 3 жыл бұрын

@@alaybey9771 i see

@MegaWingman7 3 жыл бұрын

If you look at the GEnX on the 747-8, the primary exhaust is also scalloped

@climber950 2 жыл бұрын

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.

@Rickiye 3 жыл бұрын

I've always wondered about that serrated engine design, glad to have stumbled on this 👍

@hair2050 3 жыл бұрын

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.

@Tomcatters 3 жыл бұрын

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.

@robinsattahip2376 2 жыл бұрын

Learn something every day. I always thought they were just decorative. Thanks.

@danschlesinger8772 3 жыл бұрын

Great video coby, very professional and so NOT ANNOYING like many KZfaq folks! I’m in!

@richardhoating23 3 жыл бұрын

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!

@Chicken_3475 3 жыл бұрын

I have been on the Qantas Dreamliner, and you can barely hear the engines when inside the plane

@SamuelHiti 3 жыл бұрын

Just found this channel and instantly subbed! Can't wait for what's more in store ✈

@cobyexplanes 3 жыл бұрын

Welcome aboard :)

@SamuelHiti 3 жыл бұрын

Coby Explanes Thank you Captain! 👨🏻‍✈️

@garyb.1047 3 жыл бұрын

Excellent. I like the way you assessed the variables here. Thanks.

@cobyexplanes 3 жыл бұрын

Glad it was helpful!

@Trex1094 3 жыл бұрын

Yes 789 I was on was really quiet was disappointing because I love jet noise!!

@mgsaviation9292 3 жыл бұрын

Good question - Shrek

@turboconqueringmegaeagle9006 3 жыл бұрын

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.

@jeffk412 3 жыл бұрын

Geeking out on Aeronautic details! Hellz yeah!

@ahmadhtaher9731 3 жыл бұрын

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

@agusgro 3 жыл бұрын

i was going to say the same!, it was not the turbine, it was the low and high compressor

@cobyexplanes 3 жыл бұрын

Yep you're right, this is why you always ned to proofread your work! lol

@remustgh31 3 жыл бұрын

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..

@soeren72 3 жыл бұрын

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.

@CausticLemons7 3 жыл бұрын

I learned many things from this video. Thanks!

@cobyexplanes 3 жыл бұрын

Glad it was helpful!

@JacobFNBR Жыл бұрын

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

@superskullmaster 3 жыл бұрын

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.

@vbscript2 3 жыл бұрын

Right. The Boeing ones are the only ones with the more distinctive chevrons on the nacelles, though.

@Airplaneobseesed9937 2 жыл бұрын

That is wrong but very close

@adamk203 3 жыл бұрын

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.

@jemand8462 Жыл бұрын

You should try flying on an A380 or A350 bro

@TheKatava 3 жыл бұрын

Very informative as usual

@cccc9911 Жыл бұрын

This is a great channel!!

@vladsnape6408 3 жыл бұрын

5:38 "..not only are these materials heavy and expensive.." - isn't titanium actually quite light, considering its strength?

@CodeKujo 3 жыл бұрын

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.

@scottycatman 3 жыл бұрын

@@CodeKujo Exactly. And it's gonna be thick, too.

@prof.m.ottozeeejcdecs9998 3 жыл бұрын

r..emember the old 707's they had something at the engine exhaust, that looked suspiciously like these "new" 'mixers'!

@Airplaneobseesed9937 2 жыл бұрын

No those are the reverse thrusters

@milestrumper5992 2 жыл бұрын

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.

@zippersocks 3 жыл бұрын

Wow. Great video! Totally subscribing. Keep up the good work, guapo.

@cobyexplanes 3 жыл бұрын

Welcome aboard :)

@timothycook2917 3 жыл бұрын

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 👍

@cobyexplanes 3 жыл бұрын

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

@theskyline1425 3 жыл бұрын

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.

@aarondynamics1311 3 жыл бұрын

I've seen chevrons on the Antonov 124

@theskyline1425 3 жыл бұрын

@@aarondynamics1311 yeah that too

@goldviationflights 3 жыл бұрын

Actually some A320s with CFM engines have chevrons (it's hard to see but they do).

@girikchokhani2449 3 жыл бұрын

1:49. Coby, the source says Safran, but the video is from Pratt and Whitney.

@jaredshane5500 3 жыл бұрын

Great topic n vid very well done. A topic I now know alot more about.

@cobyexplanes 3 жыл бұрын

Glad to hear it :)

@aviationchannel6204 3 жыл бұрын

I've been on the 787-8 before, and it's much quieter than the A330.

@Ksubsbefore-qu3iv 3 жыл бұрын

nah then

@youngtimer964 3 жыл бұрын

Generational difference in engines, my friend

@nntflow7058 3 жыл бұрын

Well d'oh! That's like saying B737-800 is more efficient than B727. Obviously.

@aviationchannel6204 3 жыл бұрын

@@youngtimer964 GE CF6 to GEnx

@youngtimer964 3 жыл бұрын

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.

@florimond. 3 жыл бұрын

I wish I had an airplane joke! 😅

@BrunoLevionnois 3 жыл бұрын

thanks for the credit ! nice video!!

@boeingboy223 3 жыл бұрын

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

@boeingboy223 3 жыл бұрын

@@InForTheLonghaul because that is how far technology has come ;)

@alexibm2477 3 жыл бұрын

Pretty surprised you say that chevrons are on their way out. They wer introduced just 13 years ago,that is surprisingly young.

@johniii8147 3 жыл бұрын

Simple it doesn’t need one for noise reduction

@youngtimer964 3 жыл бұрын

Right

@icollectstories5702 3 жыл бұрын

My guess is the ducting of the bypass air and exhaust are sufficient to ensure the gases don't mix underneath the wing. There is mixing turbulence behind the wing, but it doesn't get conducted into the airframe. Perhaps a smaller wing chord at the engine attachment point helps?

@richardbriansmith8562 Жыл бұрын

Awesome Video

@treschlet 3 жыл бұрын

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

@remi_gio 3 жыл бұрын

Coby is always getting hotter. Love the cub beard😍

@GeeBoggs 3 жыл бұрын

He's flippin’ adorable. Glad to see a perception that aligns with mine.

@omisokaomisokas5095 3 жыл бұрын

Great video man. Congrats. I am a now a new subscriber.

@cobyexplanes 3 жыл бұрын

Welcome aboard!

@air-headedaviator1805 Жыл бұрын

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

@user-rc9qi6yp6k 3 жыл бұрын

I appreciate the theories, you could have just included the T word in the title.

@siddhantsavanth6068 3 жыл бұрын

787 was definitely a lot quitter compared to 777!! N much more peaceful

@RM-xi4zs 3 жыл бұрын

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.

@JoeNasr123 3 жыл бұрын

You do great research!

@cobyexplanes 3 жыл бұрын

Thank you!

@CristianGarcia-wk9hh 3 жыл бұрын

I found the A350 even quieter than the 787 to be honest.

@kompressor01 3 жыл бұрын

This is the question I was asking myself. Thank you.

@roberthamilton1301 3 жыл бұрын

Thanks !

@RUSLexplorer2020 3 жыл бұрын

Interesting ! Thanks !

@Mr.Who3 Жыл бұрын

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.

@thatbooklover 3 жыл бұрын

the 787 was probably the most quiet plane ive been on (while sitting close to the engine) and just like you said it has chevrons so... though the most quiet flight ive had was at the front of the second deck on an a380 truly amazing

@martinputz8010 3 жыл бұрын

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)

@actemple3282 3 жыл бұрын

Super cool plane I just seen on with the cuts

@Devang589 6 ай бұрын

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.

@BackyardBeeKeepingNuevo 3 жыл бұрын

I had flown on “The Max” several times before the FAA grounded it. The Max is much quieter. However, that could also be a function of the acoustics inside the longer cabin and that it is a newer plane with a different resonance owing to the composite materials used in manufacturing the plane.

@Rickie-37 2 жыл бұрын

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

@eyetrapper 3 жыл бұрын

Interesting video man!

@cobyexplanes 3 жыл бұрын

Thanks :)

@bjoe385 3 жыл бұрын

I’ve flown the 787-8 twice and it wasn’t noticeably quieter than the 777 200ER or the 747 400.

@Bob-yp9wt 3 жыл бұрын

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.

@daemonyeoh 3 жыл бұрын

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.

@mytech6779 3 жыл бұрын

They design for noise at takeoff thrust, that is where you will get the real difference.

@HughesEnterprises 3 жыл бұрын

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.

@akvinodin 3 жыл бұрын

Thanks, this video was really helpful to understand better about GE9X jet engines. Is it due to Patent issues competitor RR & PW didn't try Chevrons.

@stevelaminack1516 3 жыл бұрын

I found the 787 quieter but more impressive to me was the smooth ride due to the flexibility of the composite wings.

@andrewsamuelson3275 Жыл бұрын

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.

@davidcoker7989 2 жыл бұрын

To answer your question at the end, yes, I have flown on planes with chevrons and I do honestly think that they might just be a little too quiet IMO. I like just enough roar to cover up any chatting and passenger noise in the middle of the night, and on the Dreamliner all of that is way more noticeable when trying to sleep as opposed to other aircraft where the sound of the engine helps to cover that better. You can hear everything from several rows away on planes that are quieter. The engine lull does help also to induce sleep, especially for light sleepers as myself. Could this perhaps be a reason they are doing away with them?

@BrandonKent136 2 жыл бұрын

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.