How BIG can jet engines get?!

[@MentourPilot]

The first 1000 people who click the link will get a FREE trial of Skillshare Premium👉🏻 skl.sh/mentourpilot25 Start Learning today!

[@381delirius]

Hey Mentour when you can would you mind showing us the 737 max mcas activation simulation.

[@Mizai]

@Aston Ding he doesnt care he just wants money

[@sureman13]

mount engines on rear again , not on wings

[@adamp.3739]

Correction - you said Mach 0.8 is 8% of speed of sound, but in reality Mach 0.8 is 80% of the speed of sound. By that logic Mach 1.0 would be 10% the speed of sound, not 100%.

[@arieldahl]

If they want even bigger engines, why wouldn’t they just use the wing position and angles of a TU-225? (I’m not sure how it’s called but some planes have the wings above the frame like the Cessna or TU-225, and some have the wings angled down rather than up)

[@bigd2829]

I’m doing school presentation on you in French class, we had to pick a person we admire 😊

[@mavrikforsythe5037]

Hope he sees this!!

[@repeatedily4434]

Same here wtf

[@purpl3grape]

Oh, I used my pet rock.

[@drewhour]

My man is fighting for that scholarship lol

[@josephherron7671]

That's a hell of a compliment.

[@KirkParro]

I'm surprised you did not mention that, as the diameter of the fan disk increases, the tips approach the speed of sound, causing internal shock waves and greatly increased drag- the reason for the upcoming GTF- the Geared Turbo Fan, which uses a planetary gear system to reduce the rotational velocity of the disk- this would enable even larger diameter engines (probably for high wing designs). Looking forward to a video on those!

[@andyowens5494]

Absolutely, the primary limit on fan size is tip speed (IIRC some reach mach 1.2-ish at full tilt at sea level - hence the rake in fan tips on big engines, like a swept wing, but below 1 is best for that first disc - in the compressor stages increased temperature elevates the speed of sound, so its less of a problem deeper into the engine). The GTF doesn't allow bigger fans, but rather higher LP rotational speed, thus efficiency (its all about the money). The amount of bypass air pumped by the fan is always limited by the tip speed; a smaller faster fan at approx M1 can produce as much thrust as a bigger slower fan also at M1 (without the weight penalty mentioned in the clip), so the gear ratio is set accordingly rather than just making ever bigger fans.

[@jarikinnunen1718]

Why not use variable fan speed? Speed of sound depending of air density and it vary due altitude.

[@andyowens5494]

@@jarikinnunen1718 Easy; that would require complex gearing, which is just too unreliable (or if reliable, too heavy). GTF's are hard enough to get a single ratio thats runs for thousands of hours transmitting a few hundred kilo newtons of force. Basic gas turbines (99% of those in service) just had a shaft - no moving parts, so not much to go wrong (provided it doesn't fracture). Helicopters have gearboxes, but tend not to transmit bigger forces, require extensive maintenance, and are still the weak point in the whole system.

[@neilpickup237]

Which is why we are now seeing geared turbofan designs from all the major manufactures to keep the speed of the blade tips subsonic.

[@solarissv777]

@@andyowens5494 I wounder if anyone tried putting several fans side to side, driven from one turbine through a shaft?

[@PowerUPTechie]

Thank you very much for the shout out! It really means a lot coming from the best pilot/teacher/mentour in the world :)

[@bahman9]

Mentor pilot is the Aviation Legend of youtube

[@MentourPilot]

Thank you so much! 🙏

[@ahmadtheaviationlover1937]

@@MentourPilot your an awesome pilot!! Keep up the great content I love learning from you

[@mickstermouseter7059]

@@MentourPilot As a former USAF jet engine tech, I enjoy your videos a great deal. Plus your mini Golden doodle is a handsome fellow and he matches your hair. Does he have his pilot's license yet? They are great dogs! I raise standard size Bernedoodles.

[@JustSomeCanuck]

Somewhere, an engine designer is looking at that thumbnail and thinking "Maybe...?". He probably also has a landing gear designer who is trying to talk him out of it.

[@MentourPilot]

Haha!

[@Vatharian]

I hope (s)he doesn't work for Boeing...

[@nathan87]

Engineer here. Sorry to disappoint, my first thought wasn't... really engineering related 😂

[@5Andysalive]

Some sort of software can surely counter possible issues.

[@mc00094]

@@5Andysalive lol i see what you did there 😁

[@jayreiter268]

The principal of Mass Airflow you missed is that to double the thrust by increasing velocity requires four times the energy. Acceleration is a square rule function. To double the thrust by increasing mass only requires doubling the energy. So Mass Airflow is more efficient. I was in the business 26 years when I read a paper on Mass Airflow. I realized I knew "everything about aerodynamics" but I never understood what I knew.

[@scsilveradoss]

I logged on just to comment this lol

[@MeMe-gm9di]

I'm sure you're correct, but I'd love to ask why. I assume it's because of aerodynamic effects, because intuitively F = m * a -> a = F/m v = a * t -> v = F/m * t So, if we take an arbitrary t, I would only have to double the acceleration force to double the velocity. And double the velocity should equal double the force. But I'm sure I'm missing something obvious - I'm not calling you out, just trying to understand where I'm wrong!

[@jayreiter268]

@@MeMe-gm9di Acceleration is a square rule function It takes four times the energy to double the velocity of a mass. There is a self published paper "Mass Airflow" That paper explains this very well as it applies to ducted fans. I no longer have a copy of the paper. It used to be $35 with postage.

[@jayreiter268]

@@MeMe-gm9di There are to many listings for mass airflow and ducted fan to find the paper. I do not remember the college it came from. The basics are you can double the thrust by doubling the mass or doubling the velocity of the mass. Doubling the velocity uses four time the energy. That is why helicopters have long blades turning in the range of150 rpm.

[@ilovecops6255]

LOL! WRONGES! velocity is MAGNUMTUBE and directionnes UNUIT VECTORS. Plese try agen!

[@baksatibi]

Minutephysics has a video on this topic titled "Why Are Airplane Engines So Big?", he estimates the optimal engine diameter is about 4m, over that the drag of the engine itself negates the gain in efficiency.

[@edifyguy]

You are a wealth of knowledge, and one of the nicest people on the planet. Giving Ronnie a shoutout like that is beyond nice. Your kind heart shows in everything you do. Thank you for being who you are and doing what you do.

[@cgirl111]

Each of those new 777 engines costs (in todays dollars) about the same as an entire original 707.

[@Taranaki66]

In 1955, a 707 cost $4.3mm - about $41mm in current dollars. List price on a GE9X is around $42mm. You pretty much nailed it.

[@WELLINGTON20]

@@Taranaki66 Milimetres and dollars are not compatible

[@panda4247]

@@WELLINGTON20 yeah, it should be either €mm of $inch

[@Alex-lc1bv]

@@WELLINGTON20 It stands for 'million moneys.'

[@UnlikelyToRemember]

And the diameter of the 777 engine is bigger than the diameter of the 707 fuselage!

[@dansotelo228]

By the way, seeing this video in minute 17:05, I finally understood seeing that wake of air over the wing that I used to see over the wing. This wake was always easy to see on a 747-400 when flying overseas. You see I was in the bicycle industry and must have flown around the world more than 50 times starting in the late 70s till I semi-retired in 2016. I had the privilege to fly just about every modern airliner ever made and had several close calls too. I never get bored, flying, I love every minute of it.

[@tsi_mexx6580]

So nice to chill at home and learn about jet engines this evening! Thank's, mentour :)

[@MentourPilot]

You are more than welcome! Glad you liked it!

[@mikecasiglia7619]

I've been an "armchair pilot" for years and I really enjoy your explanation of the technical details of the jet engine as well as your other videos. Thank you - and I will try to patronize your sponsors in return. Mike

[@rogerclarke3291]

I finally passed my PPL last August here in the UK. Your videos have been a big inspiration along my journey. Thanks for posting your videos.

[@MentourPilot]

Congratulations! That’s so nice to hear

[@michailhack4170]

I can't tell you how good you are at explaining aerodynamics for dummies. I really appreciate it. Thanks.

[@Otto10761]

I am 11 years old and I watch your videos and want to become a fighter pilot you have such good videos

[@MentourPilot]

Glad you like them my friend! Keep working hard in school!

[@SwedishVFR]

I always wanted to be a pilot as a kid, and now I am! Not fighters or huge jets, but still aeroplanes! 😎 Don’t give up, and you can become that fighter pilot one day!

[@lukeorlando4814]

Someone want to give this kid some real advice? Everyone told me to work hard at school. But school just crammed curriculum down my throat and never gave any hint how to achieve me dreams and so now the closest I ever managed was a 30min experience flight as a 32nd birthday present.

[@fluffy-fluffy5996]

@@SwedishVFR du har ett jätteskönt land för att flyga över. Och kanske du flyger över Norge också? Oj, vad jag önskar jag kunde göra båda ☺️ (And now I hope you are Swedish because I just gambled because of your username hehe. And no it probably isn’t fully grammatically correct but I am Dutch, studied Swedish for 1,5years and studied there with all my courses in Swedish (passed them in one take, woohoo) . However that was 20-21y ago so I’m surprised this came out when without looking up, I just let it come from memory. Now I wonder how bad it was 😂 )

[@Jdtackett0226]

@@lukeorlando4814 I can relate! After several years of post graduate academia and massive student loan debt, I realized that “you can do anything that put your mind to “ is a crocload. No; actually not at all. I will never be a superstar athlete or win the Nobel for physics. It turns out that the only thing a bachelor degree in chemistry with no working experience is only good for getting additional education in chemistry. The problem with spending a decade obtaining education is, end the end, you still have no job experience.

[@paulmurphy42]

At about 14 minutes, you could have mentioned the VFW 614 with overwing engines, and explained why that was a failure. But still an excellent video, well done.

[@BruceLee-vn6iw]

Another point to consider regarding the difficulties of having large jet engines on top of the wing vs. under slung is the shifting of mass in relation to the aircraft’s cg. Basically, having that weight above the cg results in less stability; engines under the wing (mass under the cg) actually improves stability.

[@Mark-oj8wj]

This is the only channel I watch without browsing the comments.More than enough info to keep me occupied! (even though I've been flying jets for 20 years)👍

[@chrisg4305]

I work around the RR and GE engines for the 787. They are huuuuuge.

[@MentourPilot]

Indeed they are, excellent work of engineering!

[@cl63pbx]

Damn, such a cool job! Hope you can work around the 777X engines in the future as well!

[@chrisg4305]

@@cl63pbx its pretty neat but very intimidating. I help bring the engines into the final assembly building using a massive forklift. Carrying 22 million dollars worth of engine in between 500 million dollar airplanes is sure to cause some stress lol

[@amargoun]

@@MentourPilot the RR engines have the advantage of less weight for equal thrust.

[@godfearingperson5495]

@@amargoun But RR are less powerful than the GE90

[@jamesberlo4298]

I spoke to a triple 7 Pilot, he was former military (real old School) he said it was his favorite and handled like a Sports Car and was so responsive for such a big Aircraft.

[@TheJoshRed]

I walk by the 777X engines every morning on my way to my work station (767 pylons). These engines are freaking HUGE! I still look in amazement as I pass by them.

[@lukeprice7782]

I can listen to you all day. The way you explain things is first class

[@LuisRamirez-rh6nh]

Some airplanes with top mounted engines: HondaJet, Beriev Be-200, Antonov An72/74, Antonov An32

[@womble321]

Exactly it would have solved the 737 max problem as they could have fitted them where they liked.

[@adamp.3739]

@@womble321 Well yes but actually no.

[@teecar9868]

Did you watch the video????

[@wemustconfrontrealitynow3205]

There was an aircraft called the VFW 614 which first flew in July, 1971 and had over-wing, pylon-mounted jet engines, But this was a 40-44 seat airliner with a gross weight of 19,958 Kg. and with twin engines each rated at 7,500 lbs. of thrust. These were small turbo-fan engines. A photo in the Wikipedia article shows the engine and pylon above the wing and it's not hard to imagine a seven ton engine and how substantial and sturdy, not to mention the weight of it, a pylon would need to be to withstand flight loadings. There would be no engineering compromise which would work; shorten the pylon to save weight and you cause greater aerodynamic disturbance and drag. Lengthen it to avoid these effects and you increase the weight. So much easier to suspend the engines on pylons below the wing and they just hang there on the fuse pins.

[@wemustconfrontrealitynow3205]

@@womble321 see my reply, about the VFW 614, in answer to the same comment, from Luis Ramirez.

[@k-vn-7]

11:59 Little doggo makes a safe and comfy landing. 🙂

[@JC-gw3yo]

Petter, something you forgot to mention was the jet engines have become much quiet as they kept increasing the fan bypass ratios

[@miscbits6399]

Extremely quiet. If you're near heathrow you notice the A380s because they're a "hole" in the background noise in the sky

[@kenoliver8913]

This is an important advantage of high bypass engines - moving more gas at lower speed is innately less noisy. The higher the bypass ratio the quieter (assuming the fan blade tips are kept subsonic). Noise at takeoff is a major problem in designing a supersonic airliner, because you can't use high bypass engines supersonically (again, fan blade tip speed ...).

[@davidwilliams4484]

I'm a private pilot of small 4 seat aircraft, and so a lot of what you discuss about the large jets is not relevant to what I do. Despite that I probably have watched most of your KZbin videos and find them very informative. You obviously study your subject extensively. Thanks. I also enjoy seeing your dogs

[@zariyah295]

KZbin: wanna know why airplane engines are so big at 4AM? me: Well...I should probably be asleep right now My brain: I DONT NEED SLEEP I NEED ANSWERS

[@htcmlcrip]

Same lol

[@daigriff89]

I work at an MRO Facility, and i am involved with the GE90 Engine every day. its a great engine, and its huge. I have also been involved with getting our Facility ready for the 9X. Theres some great technological leaps in it with the CMC and additive manufactured hardware. The 9X may be rated with less thrust than the GE90 115b, but don't forget is has tested to more than it on the beds, so there could be potential for a higher rated powerplant in the future.

[@JoeHTX]

Maybe I'm "old fashioned" or something, but, my favorite planes are the old trijets. I just like them.

[@Richard_McDonald_Woods]

Many thanks for these latest two videos. Very interesting!

[@TheKolian1996]

Thank you! It was so interesting I didn't even notice that 20 minutes passed!

[@MentourPilot]

Awesome!!

[@christophergrove4876]

HOLY MOTHER OF PEARL! I just looked at a size comparison of the 777 with a GE9X next to a 737 and the diameter of the GE9X is as big or bigger in diameter as the fuselage of the 737!!! Astounding!!!

[@weazleman36]

I’ve been an aircraft maintenance tech for major airline for 28 years and still love aviation so I enjoy watching your videos a lot. We have to learn how to work on all the aircraft in our fleet and the last 16 years I’ve been working pretty much composite repairs exclusively, so I’ve had to learn a lot about the newest aircraft we’ve purchased the A-350 and A-220 (C100) lol. The A-220 having GTF Geared Turbo Fan’s. Fascinating. I knew Rolls was working on a large GTF which is neat but I had no idea the A-220 had GTF Pratt’s until we started receiving them. The compressor and turbine is tiny with a normal looking Fan. With a gearbox driving the Fan you can run the fan at the perfect RPM to get the most thrust out of the blades. And the wonderful computer designs of the blade contours allows ever point on the blade to keep the air flowing over that section at an ideal speed. Rolls has a Three spool engine with the very aft Turbine shafted to the Fan and then the turbine section just fwd of that shafted to the N2 fan directly behind the Fan which guides air into the compressor then the fwd turbine section driving the compressor section. 3 spool can assure that each section can spin at an RPM that helps prevent turbulence as air flows through the engine. GE and Pratt’s are two spool and on the older engines the N1 and N2 Fan and blades just aft of the fan were driven by the same shaft from the Aft turbine section. Which caused an issue. Either the N1 or the N2 was spinning to fast or to slow never in the Goldilocks zone. Now with the Geared Fans we can always make sure through design and gear size that at core engine’s can run at the perfect speed for fuel efficiency and the fan will produce the best thrust possible. So this seems to be the next evolution in engines. The GTF is a really neat engine to look at.

[@cr-yi7ep]

I wondered when Mentour was going to get to geared fans but he never did. I guess fans getting bigger and slower, and turboprops steadily acquiring more and curvier blades, are an example of convergent evolution ;)

[@larrydugan1441]

The GE90-115B Is a beast. Never a hickup and we seldom needed full thrust. A marvel of engineering.

[@skagerstrom]

8:20 Damn those ailerons are working hard!

[@ChrisZoomER]

Hey Mr. Mentour, thank you for uploading a video explaining how jet engines work just as I requested in a previous comment (though you may have seen it) and explaining how and why a greater bypass generally means greater fuel efficiency. I would like to add something though. The fan may act like a propeller in the sense that it sucks air in and blows it backwards like an un-ducted turboprop but the reaction force on the fan is little to none, so the fan produces virtually no net thrust of its own by blowing air like a propeller. I’ve talked with numerous people who work for Pratt & Whitney along with RR Trent and they’ve all told me the same thing. They told me that the fan in a high bypass jet engine is more of a compressor than anything else, the fan blows air through the ever narrowing bypass duct as this air squeezes through a tighter and tighter space. The energy that the fan puts into partially compressing the bypass flow cancels out nearly all the thrust produced by the fan acting like a prop so the fan’s net thrust is

[@ChrisZoomER]

Another thing I noticed is that he said in this video that planes can and are even designed to exceed their critical Mach number where in his video about how fast a place can fly, he said planes aren’t designed to do that and thus never ever do. He contradicted himself in those two videos though his second explanation was more accurate which makes me hope that he learned a thing or two about airplane speed since that other podcast.

[@paulcheek5711]

I hope the dog is taking all this in...

[@Lashb1ade]

Plot Twist: Mentour Dog is the true brains of the operation.

[@vazquez0102]

I am private pilot myself and besides the highly interesting videos contentents, I enjoy watching those two dogs too.... The brown one looks very much like the 7 year old poddle that we have at home. !!!

[@kevinfletcher1999]

The dog is thinking “he’s talking to himself again! “

[@booqueefious2230]

The dog taught mentour everything he knows

[@jerryj.7905]

Although I am not a pilot (i like to fly though), I very often watch your videos; they are great!! Very well explained, very good English, very interesting stuff. Thanks!

[@mousseman8239]

One limiting factor of engine size will also be when one of these failed engines creates so much drag in flight that ETOPS will not be guaranteed anymore, and as we've seen with the two UAL fan blade failures, this can happen, and the amount of drag induced in such cases. Another limiting factor will be the vibrations caused by an unbalanced fan blade as shown in UAL 1175. Maybe the solution to this will be that the pilot can eject the complete engine from the wing, but I suspect airlines will not like it too much if the plane suddenly loses a 8 million USD engine in the ocean because it failed.

[@louis1952]

Thanks for your excellent videos - always informative. Just one quibble on this one : it is the velocity of the working fluid that increases during combustion, not the pressure.

[@jimmelnyk7506]

This was an interesting installation, and it is, of course, a very complicated subject. However, there were two potential solutions that you did not cover: 1) high mounted wings; 2) tail mounted engines. Both configurations have fewer constrictions on the engine diameter. (I am a B-24 enthusiast, so high wings are always in the back of my mind.)

[@bitcoinmoc]

good point.

[@NXTangl]

Or engines mounted inside the wings/as part of the body.

[@juniorladd3419]

I love your laid back dog.

[@lucifermorningstar4548]

Realistically only slightly bigger than the GE9X. The drag increase will eventually make it a losing battle.

[@Th3Shrike]

na mate just add afterburners and hope the thing doesn't melt anything important

[@lucifermorningstar4548]

Kun Feng HBPR turbofans act on the opposite end of thrust production than an afterburner. One increase the amount of slow moving air and the other increase the small amount of fast moving air. You don’t want both.

[@ping_me1vp]

that dog has a funny character lol just like our bunny,cracks me up every time

[@charlesisitua678]

What about mounting the engines at rear like the MD 80 ?

[@garrnk]

It's an option weight is still a major issue as big heavy engines on a tail moves the center of gravity aft. Too big and you could never push the nose down and will stall once you get airborne.

[@TonyRule]

@@garrnk Which is why the wings are set so far back. Like he said, it's all about compromises or, more accurately, tradeoffs.

[@garrnk]

@@TonyRule exactly

[@listerdave1240]

@@garrnk The C of G is not at all an issue. It is just a matter of putting the wings further back. What probably is an issue is that the wings will need to be stronger since their weight is now bearing down on the middle of the aircraft rather than directly from the wings, which means heavier wings. Once would of course need to see if maybe that increase in weight of the wings is still offset by the increased efficiency that might be achieved, which could well be the case.

[@DavidLemmo]

@@garrnk moving the horizontal stabilizer to the front can help with that

[@steveschaeffer614]

That's Ceramic Matrix Composites, been working on devoping the parts for the 9x for 7 years. Retired last week, YAY!!! Great channel, keep up the good work!

[@Ihaveanamenowtaken]

Fun fact: the theoretical limit of an engine diameter is about 4 meters, industry is reaching the limits.

[@currentriver4951]

What limits the diameter?

[@PaliVCiernom]

@@currentriver4951 Drag

[@almerindaromeira8352]

@@PaliVCiernom How so?

[@almerindaromeira8352]

Is it only diminishing returns on the efficiency?

[@PaliVCiernom]

@@almerindaromeira8352 frankly, I don't know enough to explain in detail.

[@stephensparkman3072]

I like how how much QUIETER the turbo fans are vs turbo jet. We lived north of DFW airport years ago directly below a landing /takeoff corridor. Planes would generally take off toward the north in the winter and I noticed the reduced sound of turbo fan jets was clearly much less. American Airlines flew the old MD 80 models with turbo jet engines and the noise was incredibly noticeable.

[@lukeorlando4814]

I finally remembered to not turn the volume up loud enough to hear you until AFTER the “theme song “

[@MentourPilot]

And I’ve reduced the volume, just for you! I always think of you when I edit that part.

[@alanguile8945]

Aww I liked it loud!

[@gg5115]

@@alanguile8945 Agreed that I don't need my subwoofer tested every time I watch a video. I think these are edited often on laptop or wimpy computer speakers, so the editor is unaware of the decibel level in the 100 Hz range, and/or assuming everyone else has wimpy speakers. Those of watching on the big screen in 5.1 surround get a bit more 'experience' than the author intended.

[@alanguile8945]

@@gg5115 Yes I'm watching on an old MacBook pro so 100Hz doesn't exist for me!

[@lukeorlando4814]

Thank you.

[@YesterchipsMIG]

Just came home from my holiday on rhodes... tuifly 737-800... and during boarding, it was exactly my thought: "the engines cannot become any bigger"... and now this brilliant video. Thanks so much! ^^

[@SwedishVFR]

Great video as always 👍

[@MentourPilot]

Thanks

[@dirkschwartz1689]

Hi Petter, I really love your channel with its huge variety of themes and aspects of aviation explained in a great manner!

[@heartinpiece]

This was cool! My understanding was that turbo-prop engines have even larger bypass ratios, but at the cruising speed of commercial airliners turbo-fans become more efficient. Could you also do a video that compares turbo-prop vs turbo-fan Please?

[@wiredforstereo]

This is true, which is why you see short hop routes often use turbo-props, for instance Horizon's fleet of Dash 8s. They cruise at a lower altitude, and a lower speed, but with far greater efficiency. For short hops they can be a similar gate to gate time, but cost a lot less.

[@Enzi_Meteori_902]

9:08 I love that you put the GE-9X compared to a house Now i have an idea how massive them engines are

[@paulr4279]

Interesting video. But poor doggy...heard it all in rehearsals, clearly! Hehe

[@DawnUSNvet]

I love your dog who keeps next to you as you talk :)

[@VelvetCondoms]

If we see more top-mounted wings, in the form of the AN124, for example, that would add a lot of engine space without landing gear weight or compromised aerodynamics.

[@garycard1456]

What about rear-mounted engines? Like on the Boeing 727, Vickers VC 10, Cessna Citation, Lockheed Tristar, IL-62?

[@VelvetCondoms]

@@garycard1456 balance is an issue with rear mounted engines. There is a reason that the md-80 family has the wing box relatively far back in the fuselage. It is because the engines are heavy. This limits the weight of rear mounted engines.

[@acatisfinetoo3018]

This video was very enlightening, I love learning about aviation stuff and the engineering that goes into these amazing machines.

[@PeterEdin]

The VFW-Fokker 614 and the HondaJet do have the engines on top of the wing.

[@martinmarheinecke7677]

The VFW 614 had higher maintenance costs than a conventionally build small jet-airliner. This eats up the economical benefits of its good fuel efficiency and the excellent take of and landing performance even on unprepared dirt runways. VFW underestimated the maintenance problem of "standing" engines, so the 614 was no commercial success.

[@hotshotsbydonphotography9376]

I just found your channel and find it very interesting. You do a great job explaining things.👍🏻

[@kramphillips]

So why can’t they configure the wings at the top like the Boeing C-17 Globemaster III?

[@drewpknutz1410]

the c17 is a cargo plane with no windows on the side of the fuselage if thats a hint.

[@murphysaburningdeathtrap4983]

Aircraft have better handling when the wings are below the fuselage, because of this most commercial aircraft have the wings mounted at the bottom of the fuselage. A major acceptation to this is are antonov aircrafts which are designed for pure cargo capacity, this is why there flown by some of the best cargo pilots in the world.

[@tomriley5790]

It's not impossible but the extra efficiency of the engines would have to overcome the extra drag from bulges to accomodate landing gear etc. the engines getting larger would make it more difficult to work on to for maintenance - again could be overcome if the maintenance requirements and reliability were low enough. currently though engine efficiency is right at the edge of what can currently be done (IMHO this is why we've seen a few failures over the past few years) perhaps witha bit more technology you might be able to get past this.

[@bruceparr1678]

@Jason Bowman They could use B52 style undercarriage.

[@bruceparr1678]

@@drewpknutz1410 I don't get the hint. Check out the BA146. It has lots of windows.

[@maartencautereels1206]

one like for the dog.. he is just to cool

[@barefeg]

What about attaching the wing higher?

[@barefeg]

@Guillaume Huet what about the anthonov

[@Britguy21]

A very successful aircraft with this is the BAe 146. I don't see any reason why this couldn't be scaled up but i'm no expert.

[@annatamparow4917]

So sorry to have pilots with such skills as yours furloughed! Keep well, all of you!

[@roberthunter5059]

"The way to [prevent the engines from scraping the runway] is with bigger landing gear." The C-5 Galaxy disagrees.

[@liampedersen]

I had the same thought. Why do cargo planes like the C-5, C-130 etc have top mounted wings vs passenger planes generally mount the wings on the bottom of the fuselage? I suspect that the military aircraft need more engine ground clearance to operate on dirt runways, and shorter landing gear can be made stronger. But is there an efficiency argument for bottom mounted wings?

[@deep.space.12]

@@liampedersen You fuselage needs extra struts to support a high wing, thus there are weight concerns. The military also has different requirement than fuel efficiency. Dirt clearance, as you mentioned, is an important factor because military aircrafts has to be able to land on unpaved runways.

[@liampedersen]

@@deep.space.12 Thank you for your reply. But I fail to see why a top mounted wing needs struts when a bottom mounted one does not. The C-130 (which I have ridden in a lot) does not have them. My guess is that airlines avoid the top mounted wings because of cabin noise (engines right next to windows) and difficulties entailed by stowing all the landing gear in the fuselage rather than the wings.

[@deep.space.12]

@@liampedersen Think about the body of the fuselage. On the ground, the body has to carry the extra weight of a top-mounted wing, hence heavier components. In comparison, the fuselage doesn't have to handle the weight of a bottom-mounted wing. The force is a compression force on the structure on both types. In the air, the fuselage would hang down from a top-mounted wing, and the force is now tensile. So you structural element has to handle both compression and tensile forces, which probably translates to even more increased weight. While for a bottom-mounted wing, the force is compression in both cases. Less requirement, less weight.

[@liampedersen]

@@deep.space.12 Interesting point. Thanks again.

[@JohnnyMichigan313]

Dog is hilarious. I like how the owner has matching hair.

[@publicmail2]

Todays engines are more then ever like a propeller aircraft.

[@Vatharian]

I was actually quite shocked to learn, that modern jet engines (or turbofans, really) are jet-powered ducted prop planes. With bypass ratio 12:1 or more power comes from a jet, thrust comes from a fan. On a side note I really wonder how a B52 would look with 8 turbofans.

[@JustSomeCanuck]

@@Vatharian The B-52H (the version still in service) actually does have turbofans, just ones with very low bypass ratios. Those engines are from the same family as those used on the Boeing 707 (Pratt & Whitney JT3D).

[@victortitov1740]

"Todays engines are more then ever like a propeller aircraft." - indeed. So much so that I'd like to stop calling them "jet engines" and start calling them "thrusters" instead. The name "engine" should refer to the core of the thruster - the thing that converts fuel into mechanical power (and a little bit of thrust)

[@darkwinter6028]

It is worth noting that the dynamics of fans and propellers are a little bit different due to the proximity of one blade to another...

[@jaysmith1408]

@@Vatharian eight turbofans? Would only need four, and still come out ahead.

[@morteparla6926]

I stood next to a 747-400's GE CF6 engine today, and couldn't believe how massive it is. And then it occured to me that the new GE9X engine dwarfs it in size, and my mind was blown.

[@EliAviator]

I think the GE90 is the largest.

[@GVTSounds]

@@EliAviator GE9X

[@EliAviator]

@@GVTSounds ok

[@rsvt]

Mentour: You can't put jet engines on top of the wing of an aircraft!!! Russian Beriev Be-200: Am i a joke to you?

[@MentourPilot]

You can! It just won’t be as effective

[@rsvt]

@@MentourPilot yeah they actually did it just because it's amphibious aircraft and they had no other choice

[@autobreza7131]

I submit for your review the HondaJet.

[@A.Lifecraft]

@@MentourPilot I guess it might be a thing of the future. They could build engine mounts that protrude from the wing backwards and just slightly up as opposed to forwards-downwards as it is now common. This should have some benefits like better ground clearance, better visibility from inside the cabin in case of engine failure, reduced thrust vectoring caused by better geometry and better lift and low-velocity capabilities (by sucking in air from above the wing). Meanwhile it would keep advantages of the contemporary design like dampening wing vibration and good accessibility to the engine. Maybe i am totally mistaken by missing some important detail but one sometimes wonders how long it took mankind to implement technologies that are kinda obvious. The basic structure of jet airliners was introduced with the first operational jet-fighter the Me262, it had a long and heavy nose, front gear, engines mounted under the wings and a broadened wing root and is really more a predecessor to airliners instead of fighters structurally. And since then, its all tweaking the same basic form... With these engines sitting above high-mounted wings as on the Dornier X or the Martin P6M, these are of course limited in thrust due to bad thrust-vectoring, but they did it to get away from spray water. But I am thinking about high-mounted engines on low-mounted wings.

[@jaysmith1408]

@@A.Lifecraft Honda does that

[@hermanshelton3660]

I love your dog 🐕. He is so cool 😎

[@roflchopter11]

2:48 the pressure doesn't actually increase across the combustion chamber; the volume (and thus velocity) increases. AgentJayZ has a great video about this.

[@johnmurrrhame7530]

Thanks for pointing this out. You are correct. The highest pressure in a jet engine is at the exit of the compressor. If the burner pressure was higher than the compressor pressure, the combustion gasses would flow backwards, towards the lower pressure in the compressor. The heat of the burners add volume and velocity but not greater pressure. The exhaust gasses flow out the rear, to the relatively low pressure of the atmosphere. Along the way, the fast flowing hot gasses drive turbines which power the compressor and the fan.

[@steveschaeffer614]

Yes, containing pressure after after the compressor does nothing, releasing it creates thrust.

[@evilchaosboy]

Hi, Mentour. Thank you for sharing your _MASSIVE_ accumulation of wisdom with all of us. I am in awe of it. Also, had I _even_ one teacher in high school with your skill at making difficult concepts relatable to the untrained mind, I woulda really kicked ass in physics! You are the BEST, sir!! Gotta go, the fasten seatbelt sign just lit up! \m/

[@Mortimer_Duke]

That may be the funniest thumbnail yet. What a dangling pair

[@thefenlanddefencesystem5080]

Wouldn't want to snag them on treetops.

[@carlosishac8954]

Hey I love your videos. Your explanation is awesome. Great work.

[@piotrekz9337]

@Mentour Pilot - one question, what about "top wing aircraft"? Theoretically, can they lift a bigger turbofan engines? Or maybe there are other factors precluding the creation of this type of structure? Nice to watch you, great job, regards from Poland!

[@kapteinsuperskoot6986]

Antonov An-124 and An-225. My idea also. Big engines, high wing, short landing gear. Et voila.

[@markpell8979]

As I now see, Piotrek and Kaptein Superskoot have already asked my question, Petter. These points are worthy of further discussion on your channel.

[@dansotelo228]

Your dog(s), constantly steal the show... I love flying and cherish every word you speak. But often I'm all into what you're saying when my eyes drift to your dogs and I just start busting up. And this time it was at 16:10 in this video as you were all into the airflow ever the wing, when my eyes drifted to your cute dog just laying there not giving a flying $h!t what you are saying. I laughed so hard I nearly got a headache. Keep Up The Great Work. Your Fan, Dan Sotelo

[@mrblueberry4864]

The future they just ganna go ham on the engine and then build around it

[@kabel74]

From the days of the breakthrough RB211 to the upcoming GE9X, I notice that the fan is getting bigger while the core is getting smaller. Add exotic materials, new manufacturing process and advanced electronics control to that, you got an engine that is fascinating to study as a system. What an insight into the development of jet engine and its relation to other part of an aircraft that dictate its design. Thanks.

[@RickySTT]

I can’t stop laughing at that thumbnail!

[@hokutoulrik7345]

It is the Kerbal version. MOAR THRUST!!

[@williamreymond2669]

17:15] Compressibility, the formation of a shock wave! I love it.

[@Yonada]

So I am a few months late, I know, but when you talk about engine above or below the wing, I get that there is an aerodynamic issue to be dealt with. So lets not put the engine on top of the wing. But, how about raising the wing like on the Antonovs? Or placing the engines at the back, like the MD90? The An 225 has six engines, but couldn't it in theory have two enormous ones hanging from the wings that are already high up on the plane body?

[@mycrowatt]

There are also passenger comfort, noise, and safety reasons to not mount the engines higher. Specifically: 1) Passengers like to be able to see out the windows. 2) Imagine the sheer panic that would occur if the flames from an engine surge/compressor stall were right outside the rear windows. 3) Having engines alongside the cabin would significantly reduce the potential number of emergency exits, and possibly require passengers to go to an exit further away. 4) It also potentially allows a fuel leak or fire to spread to the cabin faster. 5) More engine noise coming into the cabin. (Remember pi*r^2.) 6) Underslung engines are significantly less likely to throw shrapnel into the passenger cabin in the case of an uncontained engine failure. 7) Higher mounted engines are more difficult for firefighters to access. (Remember e.g. there have been incidents where throttle controls were disconnected and engines were put out with firefighting foam.) When you add all of this to the aerodynamic and maintenance concerns, it becomes fairly obvious that it's just not an attractive option. You might think about a return of rear-mounted engines, e.g. like the MD-83. But remember in those days the engines were much smaller (and consequently lighter). Side mounting of a modern engine would itself be quite an engineering challenge. Not to mention fuel and control routing; the dangers we've already seen with respect to engine failures in the tail of an aircraft; the moment arm created by this positioning; and of course similar maintenance concerns to high mounted engines.

[@AndrewFremantle]

Congrats on the thumbnail! It's hilarious.

[@MentourPilot]

Yes, my graphic designer is a genius! ❤️ Thank you!

[@mecomingtomo6933]

Thanks for this Vid Peter! I listen to your vids every night as I brush my teeth😄

[@marianoquiroga1976]

What about high wing configuration mounted on the upper fuselage, like on the Antonov An-225? That would make a lot of room to fit larger engines. Was that solution demoted due to handling reasons?

[@fetzie23]

Could also be a passenger safety issue? You'd have the engines with a direct line of sight to the cabin, maybe that would be a bit too loud? On the AN-225 they don't need to worry about deafening the cargo :) I can also imagine that in the case of an engine fire, you'd want to keep shrapnel away from the fuselage (placing the engines below the fuselage puts a conveniently placed reinforced barrier between the passengers and the engines, and also makes it harder for passengers to see an engine fire).

[@polcho]

from the construction point of view it's easier to lift the load than to have the load hanging below the wings so this is probably one of the main reasons why we see that it's so common with the low mounted wing designs on bigger aircraft.

[@jorge8596]

@@polcho most purpose built cargo planes have a high wing design though

[@gazfish]

Another great video, thought you might have mentioned the geared bypass fan

[@makulo93]

when did ed sheeran become a pilot. he has so many talents

[@timpine9610]

Love your dog!

[@dimitrimalikov4673]

Hello, thank you for your super interesting Channel! I was wondering: engine layout such as the one of A400M or an Antonov AN-124 could ease the accomodation of big engines below the wings, since the wings are implemented on the top of the aircarft fuselage. Why such architecture is not applied to commercial aircarfts?

[@altoclef6688]

A guy who loves engines must be the ultimate fanboy.

[@MrRexquando]

Just keeping accuracy: Turbines went from Radial to Axial not Radial to serial.

[@burningSHADOW42]

Also, there is a limit to the size of the fan, I think that is somewhere around 4m diameter. Above that, the drag from the surface area of the fan negates any benefits.

[@axelBr1]

From an oil and gas industry perspective "radial" jet engines would be called centrifugal, which is what I've always heard Frank Whittle's design called. But I think the German design started with an axial compressor.

[@axelBr1]

@@burningSHADOW42 Not to mention the tip of the fan blades going supersonic.

[@burningSHADOW42]

@@axelBr1 yes, that is a problem, but you can actually compensate for that using a geared fan.

[@axelBr1]

@@burningSHADOW42 The fan is already geared. And the slower the tip is then the even slower at the hub. This will need quite a high angle of attack to compensate so the twist on the fan will be quite savage. The fan blade aerodynamics will be really complicated and you will probably end up with very limited air flow range of operation.

[@bimblinghill]

Great vid. Explanations of the reason behind bypass fans, and of transonic airflow particularly good.

[@Ronarays]

Pro tip: Make a giant jet engine and attach wings to it with room for the passengers inside them.

[@Teuronium]

Not two but four Wings, then you get an X-Wing engine ^^

[@NatureAndTech]

Google "KLM Flying-V", and yes... it's an aircraft, not a guitar.

[@bobbyea9109]

But if, bigger engines are fited in the tail?

[@titter3648]

And the passengers will get a more "exciting" ride the further they are form the center of the axis of rotation.

[@Ronarays]

@@titter3648 It's not a bug, it's a feature!

[@brunofischer808]

VERY interesting and informative video! Thank you Peter.

[@RMGiroux]

Why not go back to high wings? Unless you explained that and I missed it, I got interrupted at the end of the video.

[@MentourPilot]

There are other issues with high wings, mainly to do with the overall structure of the aircraft.

[@vizsolyipal1]

And what about the tail mounted engines?

[@markiangooley]

@@MentourPilot ah. High wings were my first thought, but I figured there must be a reason they’re not more popular...

[@murphsmodels8853]

The main issue with shoulder mounted wings (the engineering term for high wings) is that the wing spars still have to pass through the fuselage. On low wing planes, the spars go through the area where the center fuel tank is. High wings would have to go through the passenger cabin, and you'd either lose overhead storage space, or seat space.

[@jaysmith1408]

@@murphsmodels8853 what about the Dash-8? Just lumps the wing box on the roof, but I would imagine that takes a bit of drag, not critical at regional speeds so they just got over it i’d presume

[@matualonso]

And that's why we love MD80.

[@littleolme9492]

Perhaps it's already been mentioned - Fokker made an jet with engines over the wing, the VFW-614. Obviously somewhat less successful over the years than the 737.

[@markdoldon8852]

The point isnt that top mounted engines can't be done. It's that eventually the loss of efficiency outweighs (literally) potential benefits. If a top.mounted engine creates more drag/less lift, then the added bypass capability eventually isn't enough to make it worthwhile. All engineering works that way. There are lots of ways to do a thing but the cost/benefit will determine which is the BEST choice.

[@littleolme9492]

@@markdoldon8852 Mark Doldon, that's probably exactly why the Fokker company only made 19 of those planes!

[@krislaarsgard8445]

Oops was already mentioned, with my failing to read your post, but still what about scaling Honda jet?

[@krislaarsgard8445]

But it was in operation until 2012...

[@aiwanano6507]

Amazing info, great work! Thanks!

[@edwardtomczyk1139]

So having a giant passenger size “A-10” Warthog design aircraft would be a bad idea ??? It works pretty well for that aircraft?

[@MentourPilot]

In the warthog the engines are sitting behind and above the wings. You can’t do that with huge engines since it would severely alter the weight and balance.

[@Blafirelli]

@@MentourPilot Nah, that could be balanced by huge gatling autocannon in front :) Which could then e.g. launch fireworks to celebrate succesfull landing... what a briliant idea, i should patent this!

[@NenYim]

@@MentourPilot wouldn't placing the landing gear towards the rear also counter act that issue?

[@bocahdongo7769]

@@NenYim Your aircraft basically become unlandable