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69 Inch Fan For The MAX  
User currently offlinerotating14 From United States of America, joined Jan 2012, 648 posts, RR: 0
Posted (2 years 3 months 1 week 6 days 3 hours ago) and read 20457 times:

http://seattletimes.nwsource.com/htm...echnology/2018232657_boeing18.html

Boeing has decided to go with the 69 inch fan and not the 68. Does this make a huge difference?? Thoughts

54 replies: All unread, showing first 25:
 
User currently offlineRickNRoll From Afghanistan, joined Jan 2012, 812 posts, RR: 0
Reply 1, posted (2 years 3 months 1 week 6 days 3 hours ago) and read 20474 times:

Looks like they are wanting to increase weight and drag.

User currently offlinemffoda From United States of America, joined Apr 2010, 1071 posts, RR: 0
Reply 2, posted (2 years 3 months 1 week 6 days 2 hours ago) and read 20364 times:

It's actually 69.4" as reported by the WSJ... With no change to the NLG.


harder than woodpecker lips...
User currently onlineStitch From United States of America, joined Jul 2005, 30898 posts, RR: 87
Reply 3, posted (2 years 3 months 1 week 6 days 2 hours ago) and read 20270 times:
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Quoting rotating14 (Thread starter):
Does this make a huge difference?

According to some, every inch counts.


Quoting RickNRoll (Reply 1):
Looks like they are wanting to increase weight and drag.

Ssh! You'll honk off the "fan size is magic" crowd.  


User currently offlineWarpSpeed From United States of America, joined Feb 2010, 587 posts, RR: 3
Reply 4, posted (2 years 3 months 1 week 6 days 2 hours ago) and read 20075 times:

Shouldn't the focus be on By-Pass Ratio rather than fan diameter anyway? Larger Fan, Smaller core = more BPR.


DaHjaj jaj QaQ Daghajjaj !!!!
User currently offlinemffoda From United States of America, joined Apr 2010, 1071 posts, RR: 0
Reply 5, posted (2 years 3 months 1 week 6 days 2 hours ago) and read 19971 times:

Quoting WarpSpeed (Reply 4):
Shouldn't the focus be on By-Pass Ratio rather than fan diameter anyway? Larger Fan, Smaller core = more BPR.

Funny you should bring that up... On the Leeham website they're speculating (via Buckingham Research) that as well.

http://leehamnews.wordpress.com/2012...anges-to-the-cfm-leap-1b/#comments

Buckingham Research, citing Boeing at the investors’ day, wrote that Boeing talked about a 70 inch fan. Jon Ostrower–now at the Wall Street Journal–confirmed the larger fan, but at 69.4 inches (70 inches apparently was a rounded number) as well as pursuit of a smaller core.

The smaller core is important for two reasons: a larger fan and a smaller core provide for a higher by-pass ratio, increasing fuel burn reduction performance. The smaller core also enabled the engine to be mounted closer to the wing, which in turn means the previously announced 8 inch nose gear extension remains valid.



harder than woodpecker lips...
User currently offlineByrdluvs747 From United States of America, joined Jul 2004, 2358 posts, RR: 1
Reply 6, posted (2 years 3 months 1 week 5 days 21 hours ago) and read 19284 times:

Boeing has had years to address this problem. They should have confronted the 737's design flaws the moment they decided not to green light a clean sheet Y1. How much recertification would be needed to increase the length of the rear landing gear?


The 747: The hands who designed it were guided by god.
User currently offlinescouseflyer From United Kingdom, joined Apr 2006, 3389 posts, RR: 9
Reply 7, posted (2 years 3 months 1 week 5 days 20 hours ago) and read 19068 times:

Quoting Byrdluvs747 (Reply 6):
Boeing has had years to address this problem. They should have confronted the 737's design flaws the moment they decided not to green light a clean sheet Y1. How much recertification would be needed to increase the length of the rear landing gear?

Very large, they'd be looking at having to design one of the most complicated parts of the plane in the centre wing box and along with the wing changes to take the larger, heavier engines you're starting to look at a largley new plane along the lines of the 748 which increases costs ever further.


User currently onlineBreninTW From Taiwan, joined Jul 2006, 1633 posts, RR: 1
Reply 8, posted (2 years 3 months 1 week 5 days 20 hours ago) and read 19002 times:

Quoting Byrdluvs747 (Reply 6):
How much recertification would be needed to increase the length of the rear landing gear?

I believe there is also the complication that the 737 is right up against the limit that allows it to not have slides/rafts for the window exits. Any lengthening of the MLG would mean that Boeing has to add slides/rafts to the window exits of the 737.



I'm tired of the A vs. B sniping. Neither make planes that shed wings randomly!
User currently offlinesweair From Sweden, joined Nov 2011, 1820 posts, RR: 0
Reply 9, posted (2 years 3 months 1 week 5 days 19 hours ago) and read 18765 times:

Imo the NSA was the better way, they should have done a minimum reengine on the 737 and gone full ahead on the NSA. The 737s age is showing, as any upgrade is about compromises all the time.

Maybe its the huge blunder the 787 became that has scared Boeing into going the minimal route into the future. The 777NG is also the minimal way forward. Age will catch up to a frame eventually like it has on the 737 now.

Will we even see a new model done before 2030 at Boeing?


User currently offlinesweair From Sweden, joined Nov 2011, 1820 posts, RR: 0
Reply 10, posted (2 years 3 months 1 week 5 days 17 hours ago) and read 18344 times:

Quoting clydenairways (Reply 10):
According to some, every inch counts.

69 is a nice number...


User currently offlinemurchmo From United States of America, joined Sep 2005, 166 posts, RR: 0
Reply 11, posted (2 years 3 months 1 week 5 days 15 hours ago) and read 17720 times:

Quoting sweair (Reply 9):

I would say its worth noting that Boeing clearly wanted a NSA. It's the airlines forcing them into these decisions.



to strive to seek to find and not to yield
User currently offlinerheinwaldner From Switzerland, joined Jan 2008, 2223 posts, RR: 5
Reply 12, posted (2 years 3 months 1 week 5 days 11 hours ago) and read 13249 times:

Quoting Stitch (Reply 3):
According to some, every inch counts.

According to Boeing I would say. Nobody proves that point better than Boeing. Increasing the fan size multiple times despite the earlier claims, that the optimum for the 737 has truly been found.

Seems the earlier optimums for the MAX were not good enough... And...how can we be sure that this will be final?


User currently offlineodwyerpw From Mexico, joined Dec 2004, 852 posts, RR: 2
Reply 13, posted (2 years 3 months 1 week 5 days 11 hours ago) and read 13226 times:

Quoting RickNRoll (Reply 1):
Looks like they are wanting to increase weight and drag.

Thanks for putting the smile on our collective faces!

This is good news that they went for the 70inch fan (69.4). So different than the talk a year ago about 'settling' on a 66inch fan. They have spent the additional money (nosegear) to permit the engineers a bit more latitude to pursue higher efficiency.

Will be interesting to see if we get to keep the almost round nacelle inlets with this 1 1/2" increase of the previous 68". Or perhaps the renderings already accounted for the 70"?



Quiero una vida simple en Mexico. Nada mas.
User currently offlineDocLightning From United States of America, joined Nov 2005, 19559 posts, RR: 58
Reply 14, posted (2 years 3 months 1 week 5 days 11 hours ago) and read 13038 times:

Quoting murchmo (Reply 12):
I would say its worth noting that Boeing clearly wanted a NSA. It's the airlines forcing them into these decisions.

It was really Airbus forcing them into the decision. Boeing had wanted to wait for some newer technology to get a bit further down the pipeline, which would have allowed them to design a new airframe around the next generation of engines (whether GTF's, open rotors, or whatever else). Instead, Airbus launched the NEO. When this happened, Boeing's original intent had been to continue incremental improvements to the NG, but the airlines made it clear that this was not sufficiently competitive with the NEO. Having loyal customer AA place an order for NEO's must have stung like crazy.

A clean-sheet design would have meant that the result might have been incompatible with the next generation of engines. So what was left?

It's obvious that this is the last 737.


User currently onlineStitch From United States of America, joined Jul 2005, 30898 posts, RR: 87
Reply 15, posted (2 years 3 months 1 week 5 days 10 hours ago) and read 11848 times:
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Quoting rheinwaldner (Reply 13):
According to Boeing I would say. Nobody proves that point better than Boeing. Increasing the fan size multiple times despite the earlier claims, that the optimum for the 737 has truly been found.

Seems the earlier optimums for the MAX were not good enough... And...how can we be sure that this will be final?



If Boeing continuing to tweak the design as they move towards Firm Configuration makes the MAX that much more competitive with the neo, the only ones who will care are Airbus and the Airbus Aficionados.


User currently offlineRoseflyer From United States of America, joined Feb 2004, 9607 posts, RR: 52
Reply 16, posted (2 years 3 months 1 week 5 days 10 hours ago) and read 11760 times:

Quoting rheinwaldner (Reply 13):

According to Boeing I would say. Nobody proves that point better than Boeing. Increasing the fan size multiple times despite the earlier claims, that the optimum for the 737 has truly been found.

Seems the earlier optimums for the MAX were not good enough... And...how can we be sure that this will be final?

The article does a very good job of answering that question. Of course every inch counts! Too large is too much weight and drag, and additional airframe modifications. Too small is opportunity left for improvements in propulsion efficiency. Where the final number ends up is based on very thorough analysis and it is engineers with a PhDs making those determinations.

http://seattletimes.nwsource.com/htm...echnology/2018232657_boeing18.html

A bigger fan produces more efficient propulsion. On the negative side, it also adds weight and drag. Engineers must come up with the optimal engine size to produce the greatest overall benefit to the airplane.

Penning said 69 inches is "looking like the best balance of weight, drag and performance."

However, on fan size, Airbus insists that bigger is better. Its executives argue that Boeing simply can't make the 737 MAX fan as big as it would like because the jet sits lower to the ground than the Airbus A320 and there isn't enough clearance to fit a bigger fan.

...

Some in the industry have speculated that, because of the ground-clearance limitation on fan size, Boeing is struggling to come up with a design that will match the fuel efficiency of the Airbus neo.

But in a note to clients Wednesday, Richard Safran, aerospace analyst with Buckingham Research Group, wrote that "the revised engine fan size has more to do with optimizing the engine than a means to overcome performance deficiencies."

And Scott Hamilton, industry analyst with Leeham.net, said that with the MAX still five years away from entry into service, "Boeing is doing what it ought to be doing in trying to get every little advantage out of its redesign."



If you have never designed an airplane part before, let the real designers do the work!
User currently offlinesweair From Sweden, joined Nov 2011, 1820 posts, RR: 0
Reply 17, posted (2 years 3 months 1 week 5 days 10 hours ago) and read 11709 times:

How long will they keep the NSA on the back burner?

User currently offlineodwyerpw From Mexico, joined Dec 2004, 852 posts, RR: 2
Reply 18, posted (2 years 3 months 1 week 5 days 10 hours ago) and read 11630 times:

Quoting rheinwaldner (Reply 13):
According to Boeing I would say. Nobody proves that point better than Boeing. Increasing the fan size multiple times despite the earlier claims, that the optimum for the 737 has truly been found.

I don't think the word 'Truly' was ever used. There has been no design freeze. Of course, we cannot be sure that 69.4" is final, until they freeze the design. We may see further tweaks. The key is implementing improvements that don't substantially raise the overall costs, negatively impacting Boeing's total Value proposition for the MAX.

Who cares? I enjoy seeing the NEO and MAX both getting better!



Quiero una vida simple en Mexico. Nada mas.
User currently offlineRevelation From United States of America, joined Feb 2005, 12445 posts, RR: 25
Reply 19, posted (2 years 3 months 1 week 5 days 10 hours ago) and read 11588 times:

Quoting rheinwaldner (Reply 13):
Increasing the fan size multiple times despite the earlier claims, that the optimum for the 737 has truly been found.

  

Just last month Boeing's Jim Albaugh explicitly said that the number was still being investigated and won't be firm till the end of the year:

Quote:

CFM has initially sized the engine with a 1.74m-wide fan, but the precise dimensions could change before the design is frozen in the fourth quarter.


Ref: http://www.flightglobal.com/news/art...-other-details-for-737-max-370602/

Don't be surprised if it changes yet again.



Inspiration, move me brightly!
User currently offlinelightsaber From United States of America, joined Jan 2005, 13008 posts, RR: 100
Reply 20, posted (2 years 3 months 1 week 5 days 10 hours ago) and read 11058 times:
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Quoting mffoda (Reply 2):
It's actually 69.4" as reported by the WSJ... With no change to the NLG.

It sounds like a slight move of the engine enabled by the *small* core shrink.

Quoting Stitch (Reply 15):
If Boeing continuing to tweak the design as they move towards Firm Configuration makes the MAX that much more competitive with the neo, the only ones who will care are Airbus and the Airbus Aficionados.

Boeing's engineers are doing a good job. This will help.

Any rumors/PR on if the LEAP will receive a variable nozzle for the fan? That should help 1.5% or so. The cruise efficiency does not have to be compromised for takeoff and climb stall margins. Note: I normally quote 2%, but I'm SWAGging that engine/wing interactions might limit the benefit.

Quoting Roseflyer (Reply 16):
Too large is too much weight and drag

Due to technological improvements, the MAX is not there. The larger the fan diameter, the longer the mission the MAX will be optimized for as a larger fan does add weight and nacelle drag (plus engine/wing interaction drag for the 737), but it also improves cruise propulsion efficiency. The LEAP is not yet at a diameter that is severely impacting cruise fuel burn (from a fan diameter engine aerodynamics standpoint that ignores weight and external drag).

Quoting Roseflyer (Reply 16):
http://seattletimes.nwsource.com/htm...echnology/2018232657_boeing18.html
"Some in the industry have speculated that, because of the ground-clearance limitation on fan size, Boeing is struggling to come up with a design that will match the fuel efficiency of the Airbus neo."

This will help with engine performance. I keep hearing of little improvements here and there (no links, this is from my rumor mill) that will also help the 737. It isn't that Airbus isn't doing the same thing, it is juts that the A350 and other projects are distracting them more. Boeing is about one year away from releasing engineers from the 748 to help with the 737 too... (Note: My estimate, my rumor mill refuses to give me any such proprietary schedule information right now.)

Lightsaber



Societies that achieve a critical mass of ideas achieve self sustaining growth; others stagnate.
User currently offlineRevelation From United States of America, joined Feb 2005, 12445 posts, RR: 25
Reply 21, posted (2 years 3 months 1 week 5 days 8 hours ago) and read 9455 times:

Quoting lightsaber (Reply 20):
It sounds like a slight move of the engine enabled by the *small* core shrink.

Right. The Leeham article just says "pursuit of a smaller core" without saying anything about how much smaller. What would the tradeoffs be? Meaning, at what point does improved performance via less weight and more bypass ratio overtake the cost hit to CFM of having two different sized cores?

From what I've read in the usual public sources, Boeing seems to be more public than CFM is about how different the Leap 1B is from the other variants.

In looking for more info, I ran into this cat-fight between PW and GE over use of CMC vs use of advanced cooling systems:

Quote:

P&W's approach on the geared turbofan introduces no new materials, but adds an all-new "super cooling" system to keep the geared turbofan's metallic turbine blades below melting temperatures.

"Cooling air is still the best way to increase turbine inlet temperature," P&W's Adams says.

Adams concedes that rising core temperatures will eventually force cooling systems to become more sophisticated in the absence of advanced materials. Instead of simply piping the air straight into the turbine, the coolant itself will have to be cooled. This means the extracted air first must be routed outside of the engine core and through heat exchangers, then returned to the core and down into the hottest section of the turbine.

For GE, such an approach seems too risky.

"For a commercial application such as the Leap we don't need to use the additional complexity of active cooling when we have a superior material solution at hand," Carlson says.

But the readiness for CMCs for all but the most benign environments in the engine core is still debated. CMCs have been studied since the mid-1980s in the US by NASA, and finally introduced in stator vanes of the third-stage low pressure turbine of GE's now-cancelled F136 fighter engine.

But CMCs have been slow to enter commercial production because of the high cost of manufacturing and questions about the reliability of the material in operational service. P&W's Adams estimates that CMCs still cost between 10 to 100 times more to manufacture than conventional materials. Moreover, Adams says, GE may be forced to use CMCs because the company lacks the advanced cooling technology developed within P&W.

Carlson responds that GE has resolved the problems that prevent P&W from immediately applying the new material.

"What Pratt & Whitney doesn't have is access to our trade secrets and proprietary information in how we design and build CMC parts," Carlson says. "It's quite a unique process and we've figured out how to do this."

Ref: http://www.flightglobal.com/news/art...-technology-for-cfm-engine-371586/

Interesting times ahead!



Inspiration, move me brightly!
User currently offlineflylku From United States of America, joined Apr 2006, 806 posts, RR: 0
Reply 22, posted (2 years 3 months 1 week 5 days 8 hours ago) and read 9356 times:

In what part of the flight envelope does a larger fan generate more drag?


...are we there yet?
User currently offlineairboe From San Marino, joined Jan 2011, 45 posts, RR: 0
Reply 23, posted (2 years 3 months 1 week 5 days 6 hours ago) and read 7979 times:

Boeing has previously stated they could not go beyond 68.4 inches without major and costly structural changes.

But - voila - now they can, - now the new sweet spot appears to be 69.4 inches.

I think is is pure magic how they succeed in finding another new sweet spot one time after another.
I guess they have received some magical help from poor Harry Potter, I do not hope Mr Voldemort is hiding in the wardrobe.

Expect to see first flight in 2016 - late.   



keep it free of the propellers
User currently offlineCM From , joined Dec 1969, posts, RR:
Reply 24, posted (2 years 3 months 1 week 5 days 6 hours ago) and read 7807 times:

Quoting airboe (Reply 23):
Boeing has previously stated they could not go beyond 68.4 inches without major and costly structural changes.

I'm pretty sure you made this up... Source?


25 Post contains links tdscanuck : The 737 ecoDemonstrator (CFM56-7 engines) will test variable area fan nozzles...I won't be at all surprised if they show up on the MAX: http://atwonl
26 ikramerica : For every 0.5 shrink in Core Radius, that's 1" increase in Fan Diameter assuming the full shift can be accommodated in front of the wing. While nothi
27 Post contains links airboe : http://www.flightglobal.com/news/art...ne-fan-size-options-to-two-361438/ Actually the sweet spot in the late summer of 2011 apears to be 66 inches. "
28 PITingres : Which nowhere that I can find says what you claimed: Unless you are claiming that lengthening the nose gear is a "major and costly structural change"
29 Post contains links airboe : I would gladly clarify: Very costly, very-very costly: http://www.flightglobal.com/news/art...ined-737-fan-size-decision-361001/ A design shelved ear
30 lightsaber : It is a decision to have one core with 99% of the parts common (fuel injectors and a few other parts never are common due to variations in case diame
31 aerokiwi : The forward landing gear extension has now gone from 6 inches to 8 inches. Does this mean the MAX will lose its nose-down attitude on the ground? The
32 Revelation : Clearly CFM would be able to make even more money if they could make one core work, but... ... it seems Boeing has been all over CFM to pull out all
33 ikramerica : You quoted something but didn't seem to understand it. They found 68" (68.4") would be the optimal in that it allows for a larger fan without overdoi
34 lightsaber : Agreed. But by having a more competitive airframe, it will have a longer sales life. I'm not sure which case would have the higher ROI. I can see jus
35 Post contains images CM : You are under the incorrect assumption that each increase in fan diameter requires a new increase in landing gear length. This is simply not the case
36 kanban : Tom, is there any chance they found a way to reduce the nacelle thickness by rearranging some of the engine support hardware tubing and ducting allow
37 Post contains images lightsaber : Possible, but the nacelle thickness is more for aerodynamic shape. Most people only see the metal of the nacelle. For example, the nozzle for the air
38 tdscanuck : It's possible but, like lightsaber said, there's more going on than just nacelle thickness. The 787 has a significantly *thicker* nacelle (larger rad
39 PlanesNTrains : "Having trouble" or "creating trouble"? Seriously, in this and a few other MAX threads, it appears to be the latter. -Dave
40 astuteman : I'm not sure I'm following this to be honest. There seems to be a bit of "Boeing's MAX will get the "fancy new Leap-X core", whilst Airbus (and COMAC
41 XT6Wagon : I didn't really see much of the A320NEO leap-x will suck compared to the 737MAX leap-x here, but I think some people are reading too much into the "n
42 airboe : I understand that very well. What you fail to understand is, that I am quoting Boeing statements - about 9 month old. 9 month ago, it was Boeings ass
43 RickNRoll : I think everyone knew that, but more a case of what they wanted than expected. They have been since been working hard at making sure they meet what t
44 oykie : In what stages of flight will this improve fuelburn? During climb or cruise? Or both? Will this help performance on shorter routes than longer? I am
45 par13del : If a non engineer can weigh in, you are correct Boeing settled on the inch longer gear to accomodate the fan. Also correct, but you seem to think the
46 PlanesNTrains : No. The A350 was up against a new build frame. The MAX is up against another re-engine, albeit a very compelling one. -Dave
47 Revelation : IMHO your logic is flawed. First of all you have no idea what Boeing promised the customers so you have no idea if the engine is hitting the fuel con
48 Stitch : As I read it, enough units of the LEAP-X1B will be sold to justify giving it a core optimized for a 69" fan as opposed to using the core of the LEAP-
49 kanban : Thanks.. both of you.. yes that is a cramped place..supported both spares and engine build up at different times... so could they be looking a flatte
50 tdscanuck : I don't think we know enough to make that conclusion; it could because they're not where they want to be or it could be because they see an opportuni
51 sweair : Will the NSA sit as low to the ground as the current 737? I think it will be a bit different, more like A320 and a decent 757 replacement member done
52 AirbusA370 : The NSA will look more or less like an A320, that is the current state of technology. That is the whole problem, you won't develop something to compe
53 kanban : let them take out a few.. I have about 120 lenses from an estate I need to get rid of... Thanks Tom
54 Post contains images lightsaber : Sad but true. Hence why I want to leave nacelle structure alone! Or, be GE and take ownership of the 'propulsion pod.' What I mean is the two cores w
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