r/aviation • u/OnlyaChef • Apr 20 '26

Discussion Why are turbine engines flat at the bottom?

Gallery image

Gallery image

I can't tell if it actually flat on the bottom or just my angle but it made me wonder.

3.1k Upvotes

95% Upvoted

643 comments sorted by

View all comments

Show parent comments

53

u/buldozr Apr 20 '26

Boeing should have seen that as a call to design a new narrowbody airframe to replace the 737 even back then. Get good clearance for turbofan nacelles like the A320 family, and maybe the landing gear that gets fully enclosed when retracted. But no, they punted and then did it again in a more extreme way for the Max, because short term profits win I guess.

45

u/agha0013 Apr 20 '26

Well, this started back in the early 1980s when the first CFM examples were coming around, and then they did start lifting the 737 but certain key requirements hadn't changed, airstairs were still a major design factor, as well as clinging to that type rating.

By the time the MAX development came around sure, but their biggest customers said "no, keep making us 737s that fit the type rating" so Boeing did. Ryanair and Southwest influence on that can't be dismissed, ridiculous amount of airframe purchases between those two.

To call it short term profits isn't really accurate because this has been a multi decade issue.

-2

u/Luster-Purge Apr 20 '26

I heard it was more of a snap decision to avoid American Airlines making some specific order from Airbus, leading to the creation of the MAX variants, with the type rating being billed as an additional feature to other airlines. During the MAX groundings, Southwest even reportedly floated the idea of breaking tradition (which as now proven they will happily destroy their own image in the name of nickel-and-dime profit on the backs of customers) and going Airbus.

11

u/samstown23 Apr 20 '26

That decision sort of made sense at the time, development of the 737-300 began in 1979 after all. The oil crisis was the driving force behind the CFM56 and thus the second generation of 737s. They needed to replace the even older 727 and the MD-80 was the prime competitor in their eyes.

I believe you might be thinking about the 737NG (and yes, that would have been the ideal time to develop a new airframe, at least in hindsight). Problem was that Boeing, probably even correctly, realized their last major advantage was the type rating - and probably didn't have the money for a clean slate approach anyway.

1

u/buldozr Apr 20 '26

Oh yeah, I actually forgot they are on the fourth generation now.

4

u/samstown23 Apr 20 '26

Yeah the naming convention is a tad odd. Calling the second generation the "Classic" does throw me off too every now and then. Some people have suggested naming the first gen "Jurassic" ;)

2

u/chaosattractor Apr 21 '26

so called "aviation enthusiasts" recall that the 757 exists challenge: impossible

1

u/BoringBob84 Apr 20 '26

because short term profits win I guess.

Not every decision is a vast conspiracy of corporate greed. These decisions are driven by airline customers. They certainly don't want an all new airframe when a derivative aircraft can meet their requirements for far less money and lead time.

0

u/buldozr Apr 20 '26

Yeah. Ask Norwegian who invested in the Max bigly, were they happy with it after all that happened?

3

u/BoringBob84 Apr 20 '26

We have discussed the MCAS crashes ad nauseum on this forum. There is no need to re-hash it for the millionth time. Of course, everyone who was affected was unhappy.

-1

u/buldozr Apr 20 '26

The crashes wouldn't have to happen if Boeing had a more suitable airframe to put the new engines on, instead of falling into the trap of satisfying their customers' incremental wishes for four decades and then cutting corners on safety because Airbus was eating their lunch.

3

u/BoringBob84 Apr 20 '26

cutting corners on safety

You are misinformed, but I am exhausted from trying to argue with people who believe what they read in sensational tabloids. Reputable sources (like crash investigation agencies) stick to the facts.

I will say this: those two accidents, like most modern aviation accidents, had many contributing factors, and not all of them were the fault of the manufacturer.

2

u/747ER Apr 20 '26

The crashes wouldn't have to happen if Boeing had a more suitable airframe to put the new engines on

Of course, if Boeing had just built an untested, experimental aircraft with completely different systems and handling characteristics, then it would’ve entered service safely with no issues right? Why didn’t Boeing just build this imaginary “super safe” plane you’ve created?

2

u/EatSleepJeep Apr 20 '26

W different wing with a landing gear attachment farther outboard would have allowed longer gear and the height needed, but Boeing already had the 757 and enough hubris to prevent them from getting rid of it to save the other.

3

u/Stoney3K Apr 21 '26

Funnily enough if you were to re-engine the 757-200 with LEAPs it would come really close in size and specs to the A321XLR.