Possible Boeing 737 replacement

[starviking]

That is not to say that Boeing has messed up badly. How can a flight critical system be designed such that it is susceptible to a single-string failure?

The Seattle Times report (Reply 62, Boening 737 MAX thread) gives the answer:

"The bottom line of Boeing’s System Safety Analysis with regard to MCAS was that, in normal flight, an activation of MCAS to the maximum assumed authority of 0.6 degrees was classified as only a “major failure,” meaning that it could cause physical distress to people on the plane, but not death.

In the case of an extreme maneuver, specifically when the plane is in a banked descending spiral, an activation of MCAS was classified as a “hazardous failure,” meaning that it could cause serious or fatal injuries to a small number of passengers. That’s still one level below a “catastrophic failure,” which represents the loss of the plane with multiple fatalities.

The former Boeing flight controls engineer who worked on the MAX’s certification on behalf of the FAA said that whether a system on a jet can rely on one sensor input, or must have two, is driven by the failure classification in the system safety analysis.

He said virtually all equipment on any commercial airplane, including the various sensors, is reliable enough to meet the “major failure” requirement, which is that the probability of a failure must be less than one in 100,000. Such systems are therefore typically allowed to rely on a single input sensor.

But when the consequences are assessed to be more severe, with a “hazardous failure” requirement demanding a more stringent probability of one in 10 million, then a system typically must have at least two separate input channels in case one goes wrong.

Boeing’s System Safety Analysis assessment that the MCAS failure would be “hazardous” troubles former flight controls engineer Lemme because the system is triggered by the reading from a single angle-of-attack sensor.

“A hazardous failure mode depending on a single sensor, I don’t think passes muster,” said Lemme."

Ref: https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/

 

[Jason Dykstra (Wyvern)]

Is this concept, in any way, related to the NMA or NSA?

 

[TomcatViP]

No but it's interesting. It shows that beyond Boeing, many engineers wouldn't have thought that someone would crash a plane simply because of an erroneous alpha trim input: the legislator, the safety controllers at Boeing and the FAA staffs.*
Nobody punched that yoke but the PiC. Nobody slammed the throttle full trust but the PiC. None Boeing engineer could have acknowledged that sensor maintenance could be botched that way...

At the end it's apple Vs bananas... And a huge criminal(?)** PR campaign.

*And previous flight did demonstrate that a crash was not a direct consequence of the failure (the plane was flown straight to its destination while encountering the same failure)
** Multiple individuals actively pursuing a defamation campaign

 

[Maro.Kyo]

https://leehamnews.com/2025/10/27/boeing-sees-no-new-single-aisle-plane-until-2040/
2040 for entry into service, that is.

 

[alberchico]

Finally we're seeing some activity from Boeing. Disappointed that the truss braced wing as well as the RISE powerplant are being ditched for something more conventional, but I think we all knew that was inevitable. It's interesting that Boeing is starting out with a larger airframe size than many envisioned, but considering the runaway success of the A321NEO that makes sense. One thing I know both manufacturers won't do is repeat the mistake of shrinking their aircraft to create an A319 or 737-700 variant or God forbid something along the lines of the A318.

Article has a paywall but I'll quote a summary of the main points from a post on another site:


"- single aisle airliner (more revolutionary than evolutionary)
- closer in size to the 757 than any 737 model
- model will have a familiar tube and turbofan design
- far more efficient wings than anything in service today, they’ll be longer, thinner and yes they will be folding wings like the 777x
- teams in Boeing are stepping up exploratory work from suppliers, work includes redesigning the cockpit to make it more user friendly, there’s also looking at a small engine in the tail (probably won’t make it to the final design Imo, but it’s being explored)
- Boeing is looking at the upper end of the max-10 size of aircraft and then from there they’ll create a family of aircraft. So essentially the smallest version of the new family will be the size of the max 10.
- engines will be ducted, Boeing is not interested in the CFM rise. CFM is working on a ducted version of RISE
- groundwork will begin in earnest once the 777-9 is certified essentially. But engineers are ramping up the R&D, testing what suppliers have available or what they’ll have.
- Boeing is also courting engine suppliers to see what they have available"

https://www.bloomberg.com/news/feat...en-aircraft-trump-and-china-to-power-comeback

 

[TomcatViP]

@alberchico : Thanks for providing the summary.

 

[flateric]

I dunno, I can open article without paywall and one point is (expectedly) totally different to summary provided

"For senior executives in charge now, the appetite for risk is decidedly limited. Initial design preferences point to a single-aisle airliner that’s more evolutionary than groundbreaking, according to people familiar with the plans. Closer in size to the out-of-production 757 than any current 737 model, the initial plane would adhere to conventional design elements and engines, rather than taking a more revolutionary path, said the people.

Teams of Boeing engineers are stepping up exploratory work with supplieraround other technological advances that might go into a new airplane,from the electronics in its cockpit to the small engine in its tail. The work includes redesigning a flight deck that’s more user-friendly for pilots in thewake of the Max tragedies.

The US manufacturer isn’t expected to formally launch its next all-newplane until around the turn of the decade, said people familiar with thematter. That’s around the same timeframe when Airbus is expected tounveil its own leading-edge narrowbody plane, setting up a clash.
Boeing is looking intently at the upper end of the single-aisle market whereit doesn’t have a product beyond the 737 Max 10, the people said. Fromthere, the US manufacturer would create a broader portfolio of efficientworkhorse jets to eventually replace its 737 family.
The model will have the familiar tube-and-turbofan design that’s marked jetravel since the 1950s, although its wings will be far-more efficient andadvanced from any commercial jet in service today. They’ll be longer,thinner and hinged at the end, similar to the
777X wing.

“At the same time, as we have done over the decades, our team evaluatesthe market, advances key technologies, and improves our financialperformance, so that we will be ready when the time is right to moveforward with a new product,” Egan said. The company declined toelaborate on its strategy or make Ortberg available for an interview."

 

[Not James Stockdale]

I dunno, I can open article without paywall and one point is (expectedly) totally different to summary provided

I think that summary came from airliners.net and they ragged on the guy for miswriting that over there.

It's been so long since Boeing should have built a 757 replacement that I can't even congratulate them for this.

The Code C gates they want this plane to fit into allow for a wingspan up to 36 m, but is there a length limit associated with that or is it dependent on airports?