Why are the Boeing 737NG engines FLAT?

Hi everybody, welcome to Mentour, here’s another video podcast as always I hope you are doing absolutely fantastic so today.


Hi everybody, welcome to Mentour, here’s another video podcast as always I hope you are doing absolutely fantastic so today on the podcast, Why is the engine on the 737 flat at the bottom? Stay tuned. Right everybody, so why is it that the 737NG has engines that look like they’re a little bit flat at the bottom? Well, in order to understand this we really need to go back in time We need to go back into the history, when the 737 family was born. So back in the 1960s Boeing engineers were looking into creating an aircraft type that would be easy to use Easy for ground personnel to both board and to load with bags, and they were using something called Bulk loading, which means that they Were basically taking the baggage and throwing it into the hole; they weren’t using containers like to do on more modern aircraft, okay? Now in order to do that efficiently, they wanted to have an aircraft that was fairly low-down to the ground so they created The 737 to be just that to be low-down to the ground, easy to handle, and that was not a problem because at The time they were using turbojet engines. Now, they were using an engine type called JT8D and that engine essentially looks like a cigar and the reason that it’s so much smaller than the current engines that you see is Because a turbojet engine uses the core engine action, the hot gases that’s being expulsed at The back of the engine to create thrust. Okay, that’s how jet engines used to be run and you also see them in a lot of fighter jets today Now, the 737-100 and -200, the ones that We refer to as the Jurassic 737 models, they kept this engine but as the decades was moving forward into the late 70s and beginning 80s We were sort of seeing the advent of the turbofan engine now the turbofan engine works very differently Than the turbojet engine. The turbofan engine uses the Hot air gases that goes through the turbines to drive a big fan at the front of the engine. Now, that big fan Is what’s creating most of the thrust so it’s the bypass ratio as in the, air that’s passing By the core of the engine that is cause– that giving most of the thrust and that Also has the benefit of damping the sound so they’re much more efficient fuel-efficient and Quieter than the turbojet engines so The Boeing engineers wanted to fit the new CFM56 engines, the new Turbojet, -sorry the turbofan engines onto the 737 model, but here they encountered a problem. So since they originally Wanted the aircraft to be that low-down to the ground if you wanted to put a turbofan engine onto that same Airframe the turbofan engine is much bigger; it has a much bigger diameter Than than the the turbojet engine did. Okay so They faced that problem. They, also faced an additional problem of since they wanted to redesign the 737 they also wanted to be able to fit more passengers and the only way to do that is by stretching the airframe so the 737-300 and -400 and -500 actually they were continuously being stretched, okay now When you stretch an aircraft the center of gravity is going to change, okay? and I’m going to do a separate episode about center of gravity and why you’re not allowed to sit where you want later on, but When they did this, they also needed to solve the problem with this change of center of gravity, and the way that they Did that was that they redesigned the engine pylons, those are the things that’s actually holding the engines to the wings so they Moved the engines from being under the wings to being ahead of the wings By doing that they could actually lift the engines a little bit from the ground, and By redesigning the engine lip, the engine intake, okay, to being a little bit more flat at the bottom they could also gain a couple of precious Centimeters from the ground so by essentially moving it forward they were solving the problem with the center of gravity Because that actually balanced the aircraft out, and it could also lift it to get it away From the ground so the engines are not flat alright the engines obviously is completely circular they’re round Because the fan is round but the lip is a bit flattened and That helps when, we are for example doing crosswind landing so in a crosswind landing you might come in with A slight bank angle into the landing. Now, what you really really don’t Want is for the engine to be so close to the ground that it is a risk of hitting the ground So it is crucial That the engine inlet is as far away as possible from the ground, okay? Another redesign that you might have seen on the 737NG And the classic actually, is that they have kind of like a chipmunk Sight to the engine. That’s because another thing that We did or that Boeing engineers did in order to gain extra ground clearance is they moved the accessory gearbox and the fuel pumps from being Located under the engines to the side of the engines and that’s why you see that kind of little chipmunk shape to the Right so, by doing this they now Have achieved more ground clearance they could fit the more efficient, quieter Turbofan engines to the 737 family but they didn’t have to redesign the landing gear the only thing they Did was they strengthened it a little bit because the aircraft and the airframe was now heavier but They didn’t have to extend it they, on the 757 they actually Did extend it but that’s a different model so up until the newer 737NG’s the New generation 737, we have kept more or less the same ground clearance and we have enabled them to be easier to handle, to be easier to Load than for example the airbus 320 family, which is much higher than the 737 is Now, from from the 737NG, now we’re going into the 737 MAX family; the 737 MAX family will have Increased the the landing gear height slightly, okay, so that’s to enable the leap engines to be fitted Which is an even more efficient turbofan engine so from the 737 MAX family and up, we will not see this iconic Flattened shape of the engines from the 737 family anymore Guys, I hope you liked that explanation and continue to send in more questions about all things that you want explained And also make sure that you get the mentor aviation app There’s more and more people that are joining, by the day, you will find some links here in the description of this video inside of the app You’ll be able to watch videos you can get collections and see how to for example do a full set up or an emergency evacuation Of the 737 and also you can chat with other users other People that might be in training from different parts of the world and You can chat with me, so get in there register yourself, enable push notifications and Just tag @mentour if you, want to speak to me directly Have an absolutely fantastic day wherever you are and i’ll see you next time

100 thoughts on “Why are the Boeing 737NG engines FLAT?”

  1. …..and that boys and girls is the reason the max has issues. The new engines are even BIGGER, and boeing moved the engines up in the wing more causing the plane to stall easier. Hence, the secret software as a cover-up!!

  2. The news media made it sound like the engine placement issues were a new problem with the MAX generation that Boeing needed to work around to be competitive with Airbus. However, in fact they’ve know since the 1980s, Classic series, that a redesign was necessary but they kept kicking that can down the road. Likely so the program managers could save a bunch of money and get their big bonuses. Urgh, that’s so infuriating.

  3. Yes, the 737 is easier to handle and easier to load. And now with the 737 Max, it's also easier to crash. They just keep making life easier 😂

  4. My job is to R and R those outer barrel skins and lip skin segments on those units. If anyone cares. It’s a living.

  5. The 737 feels more and more shoehorned as time passes on. The design of the 60s is outdated and results in work-arounds like this. In terms of safety I’m not so sure if this is going to work out in the long run, as is tragically demonstrated with the MAX iteration.

  6. Eeeeeeeverytime I want to go back to doing something else, there some video that is like directly answering some question that I have always been curious about! Let me gooo xD

  7. Says more efficient engines in 737max, around 350 got killed already within a year! Garbage american engineering…

  8. When he was standing there someone should have pushed it up to full thrust. He would have to start to run😀😀

  9. Every body knows why , it was you my capt had a bad day and just landed bad really hard, just kidding

  10. LOL! It took 8 MINUTES to explain the reason why the housing of the engine is flat is so there is more ground clearance. Well nobody can accuse you of not being thorough lol! Seriously though I’ve watched a number of your videos and you have a talent for explaining information regarding Aircrafts that’s easy to understand for beginners. As always I hope you’re doing absolutely fantastic!

  11. Cheaper way to gain ground clearance is the number 1 answer (Engineer survey). Second place, we have cosmetic appearance or looks. This also assures that the original engine manufacturer gets the replacement and overhaul contracts for that aircraft. Finally, there might be a significant enough amount of a reduction in drag, that over time reduces annual fuel consumption expenses. Other than these, I have no idea.

  12. Thank you , Mentour Pilot, as the New ' Max ' appears a little front heavy needing MCAS , could Boeing not consider fitting an extra Rear FuelTank to re balance the Aircraft and give the MAX more range to compete with the Airbus A-321 Ex L.R. ? Could you please give me reply. ThankYou , Aircraftman 789

  13. I have always wondered why that part of the engine is flat. Thanks for the lesson. By the way, you look sharp in that uniform, Captain!

  14. what's the meaning of 737-200, 737-300 and B747-400 or A380-300? why its called 737? please explain…thank you

  15. Mandela effect just like the engine being so far out on the wings they used to be under the wing completely under which makes more sense than being so far out on a wing looks unsafe to be honest but you probably don't know nothing about Mandela effect so you don't and won't believe me but would you believe thousands of people who also say the engine used to be under the wing and not where they are now. Well would you. Because thousands do remember but I guess we all miss remember.

  16. Thanks for inviting questions about the how and why of airplane functioning. My question is: why do airline pilots decide to kill themselves while at work?

  17. Can you explain why 777 engines roar during the start up process? It’s a distinct sound that no other plane makes

  18. you want to know why? I will tell you why. Boeing is extremely lazy and even greedier and their attempt to maintain a dinosaur who has long since passed retirement age is going to be the reason they fail as a company the 737 has flat engines because baggage handlers used to physically throw the luggage into the compartment because it was so low to the ground but now instead of redesigning the engines and basically redesigned the entire plane they maintain this stupid lowrider useless design in today's modern encased prop turbine engine world and now you have problems like the 737 Max. people are dying in the hundreds and I just don't understand why you would want to keep this absolutely beyond outdated dinosaur alive when it is so far past retirement age it is disgusting to even think that they are keeping the engines flat and keeping this thing as low to the ground as they do for absolutely no reason other than to cut corners on training pilots on a new aircraft and several other reasons which all funnel down to increasing profits and minimizing expenditures which is extremely ironic to me because all they're going to do is lose money in the end when the 737 Max turns out to be a complete disaster which it already has proven to be it just needs to retire. stop making the stupid engines flat work on a high Wing design and just focus on on the next big thing in aviation but please for the love of God retired this stupid dated dinosaur already!!!

  19. Funny!, Boeing as a company reminds me of British Petroleum and the oil rig disaster off the coast of Louisiana because they wanted to save a few pennies they ended up losing billions after they made a huge mistake and honestly if you look at major corporations as a whole these kind of things happen all the time where they try to pinch pennies by cutting corners and disaster inevitably occurs and then they end up losing way way way way more than they would have lost if they just would have taken the time to get it right the first time and not cut corners I honestly do not understand the minds of corporate big dogs because it seems like such simple logic and common sense to me to spend a few dollars now to save a few billion dollars later…🙄

  20. The MAX engines are so efficient that they have not burned a single gallon of fuel for months. Boeing went from a company for which I had great respect to a company that seems to be corrupt and rotten from the top. After two deadly crashes they petitioned President Trump to allow their defective design to continue to fly – and kill even more innocent people.

  21. It took my attention for this video regarding boeing 737 coz I used to fly this plane everytime I go back to Papua New Guinea from Philippines and vice versa with Air Niugini as the carrier.

  22. I just watched your video explaining why the front of engines aren't painted. Now I see this video with the front of the engine painted. Apparently it is not a rule.

  23. I missed most of it, catching the end of the DC-7 and the Connie ! Wish they were still used as a choice for those of us wanting to spend a few more hours in the air. The sound and feel of those four 18 cylinder radial engines is like music. The sound of the props, also. By the early 1970's props and piston aircraft travel was ending. In 1975, I started aircraft mechanic's school , became an A&E mechanic in 1980. Helicopter mechanics and crew was the future. As time passes, there will be no one alive to remember flying in those great airplanes. People alive today in their 80's ans 90's were there for most it. People ages 60's and 70's were there as it ended.

  24. B737のエンジンが下の部分フラットなの知っているよ、大昔の737ー200はターボファンじゃ無かったから丸かった。
    爺さん英語も入力出来るけど、スペルが間違いそうだし、いかんせん時間がかかりそう。✈️

  25. Hey, @mentourpilot, what is the point of APUs on larger aircraft if shore power is available at just about any destination capable of handling large aircraft?
    Just asking because I recently flew to a regional town on a dash-8 and it lacks an APU and requires a genset on the ground… Yet wouldn't small airports with limited infrastructure be a textbook case for needing an APU on board?

  26. The engine is flat at the bottom because the designer has a sloppy hand for drawing ✍🏽 and he was shaking.

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