737NG-to-MAX production Plans and comparing the 737 with the A320/321

Boeing is gearing up for the transition from the 737 Next Generation to the 737 MAX at its Renton plant in Washington State.

During pre-Paris Air Show briefings at Boeing last month, embargoed until today, Boeing officials detailed how they will transition the production facility in a continuous flow. When Boeing introduced the 737NG, sales of the 737 Classic were terminated. Boeing expects a two year transition period this time, meaning the NG will continue production 2019, two years after the 737-8 MAX first enters service.

The exception will be the P-8A assembly line, which is based on the 737NG and which is in the so-called “saw tooth” building to the west of the primary 737 assembly plant. The saw tooth building is seen at the far right of this Boeing illustration.

Renton 737-MAX Factory Renderings

The primary plant above shows the current NG assembly lines to the left and right. The line on the left produces 21 737s a month and the one on the right will be at this rate next year. The line in the center will initially be the MAX transition line, where the test aircraft will be assembled and the workforce learns the differences between assembling the NG and the MAX, which will have substantial differences compared with the NG.

Eventually, the MAX will fully integrate on the two NG lines.

At previous air show briefings, Beverly Wyse VP and GM of 737 Program, said the center line will have the capacity to match the assembly rates of the other two lines, or 21 per month, giving Renton the capacity to produce 63 737s a month.

At last month’s briefing, Wyse displayed this chart that suggests production rates will maintain at 42/mo from implementation next year.

737 Production

However, we know from our own market intelligence that Boeing is considering sharply higher rates by the end of the decade.

Wyse, in the recent briefing, said the workforce is a key advantage for Boeing with flow-through benefits for Boeing’s customers.

“One of our key strengths at this site has been our employees…both in design and in production. It gives our customers a significant advantage and one of those advantages it brings our customers is flexibility. It has served our low-cost customers very well.”

Wyse said the 737’s lighter weight compared with the A320 is another advantage.

737 Weight Advantage 1

“The structural efficiency of the aircraft is not really visible, such as advance alloys, that contribute to lighter weight. We don’t have landing gear doors on the plane. That contributes to hundreds of pounds of weight advantage. The light weight, inner-opening cargo door contributes about 800 pounds of weight advantage. The lack of overwing escape slides. The fact that it’s lower to the ground. And yes, even that slightly narrower fuselage actually translates into an advantage for our customers.”

[We’re not sure we’d brag about not having evacuation slides, but maybe that’s just us.]

Wyse zeroed in on the lighter weights of the 737s vs the A320 family with this slide.

737 Weight Advantage 2

We noted that Boeing included one auxiliary fuel tank for the A321 but not for the 737-900ER and subsequently questioned the rationale for this because this would appear to be unfairly adding weight to the A321 for purposes of this illustration.

We have a 5900kg advantage on the -900ER (slide show 1 aux tank for the A321, not for the 900ER).

A spokesman provided this information:

Rather than comparing airplanes with the same number of fuel tanks, we compare those with the closest range to get that figure.  But in full disclosure, even with an extra fuel tank and 415 nautical miles greater range, the Boeing airplane is lighter.

Here are the numbers behind the chart:

  • A320/CFM (150 seats): 42,890
  • 737-800 (162 seats): 41,500
  • A321/CFM/1 aux tank (183 seats): 49,080 kg (design range = 2,635 nmi)
  • 737-900ER/0 aux tank (180 seats): 43,580 kg -5,500 kg (design range = 2,845 nmi  +210 nmi)
  • 737-900ER/1 aux tank (180 seats): 44,070 kg -5,010 kg (design range = 3,050 nmi +415 nmi)

The addition of 160 kg to both the A320 and A321 OEWs for “Production Winglet in lieu of Wing-Tip Fence” results in the two delta weights shown on the charts.  Adding that results in the following:

  • A320/CFM (150 seats, Production Winglets): 43,050 kg
  • 737-800 (162 seats, Winglets, Carbon Brakes): 41,500 kg -1550 kg
  • A321/CFM/1 aux tank (183 seats, Production Winglets): 49,240 kg
  • 737-900ER/0 aux tank (180 seats, Winglets, Carbon Brakes): 43,580 kg -5,660 kg

Although we probably could quibble with some of the methodology described, we at least now understand how Boeing came to include one aux tank for the A321 and none for the 737-900ER.

Indisputable, however, is the seat advantage the 737-800 has over the A320.

“Huge to our customers is the increased revenue they can get from the 12 seats. It results in nearly half a million passengers being carried over the 20 years,” Wyse says.

48 Comments on “737NG-to-MAX production Plans and comparing the 737 with the A320/321

  1. If Boeing wants to ramp up in order to produce 63 MAX aircraft per month, perhaps they’d better start to walk the walk. Again, I’m not sure from where Boeing is going to get enough orders in order to match a neo production output of more than 60 units per month.

    http://www.pdxlight.com/neomax.htm

    • yes, how dare Boeing plan for the future. They should certainly listen to you and just fold up shop and kowtow to their rightful masters in Toulouse. The nerve of them to even dare to try to compete with Great, Glorious Airbus. All Hail Airbus – Emperor of the World.

      • Well, being grumpy won’t help getting your old customers to come back to you, that’s for sure! 😉

        Good planning for the future means making smart and intelligent decisions, not to mislead and make up stuff as you go along.

  2. The B-737NG has always had both a weight and range advantage over the A-32X (exception, the A-319/LR/CJ has more range than the B-737-700/ER, but the Airbus still weighs nearly 6,000 lbs. {nearly 2,700 kg.} more than the Boeing).

    • If you are going to compare the ACJ319 you need to compare it to a BBJ1, not a 737-700. They are different animals.

  3. First statement: The B737 has a weight advantage over the A320. Full stop.

    Mr. Wyse could in fact be more precise. Yes, the Boeing aircraft (like those that followed) are very efficient when it comes to structural weight, and Airbus was unable to match this until probably recently (hard to figure out). However, a quite substantial part of this advantage is caused by the B737 being certified to the rules of 1966. That for example allow to sit 189 instead of 180 in the A320 (besides having the exact same door layout), it allows Boeing to use less stringent crash and fatigue rules, and allow Boeing to go without emergency slides on the wings.
    I regularly talked about seats: the B737-800 is longer, hence allows more seating if pitch is a constant. Yet, it isn’t. Means A320 has less comfort? Depends, the A320 is wider. Some people prefer seat width, some prefer pitch. Most like to have both, and lots of it.

    So, like all marketing in connection with the B737MAX, again a big pile of junk.

    Note: I am not anti-Boeing. I am simply amazed by the amount of utter BS being emitted by the marketing department, especially in case of the B737. Aircraft like the B777 need no empty pointless marketing briefings, because they are simply good.

    P.S.: A320 MSN0001 had carbon brakes, like all 5600 that followed.

    • Riiight and Airbus only publishes pure gold facts. The sun shines out Airbus’ ass, and every break of wind from their marketing department is a fresh breeze. How dare those Boeing people have the audacity to market their own products, the gall. The nerve of some people. All HAIL AIRBUS – Emperor of the World.

      • Ordinarily we would edit down the tone a bit, but we actually laughed out loud on this one. But Howie, please tone it down a bit in the future. We’re still trying to control the language and tone of all comments.

      • Very well, I will watch the language. However, when people make blatantly dumb comments questioning why a company, ANY company, had the audacity to market their wares, well that just deserves a comment to point out how ridiculous it is.

        • Could you do us the favor and provide a quick run down on the “blatant falacies” your irate eye has locked on?
          What ever you seem to comment on seems to be not available to other readers.

          Shining sun and all the last time something even remotely in the direction of
          your allegations existed was when Louis XIV of France reigned:
          “The sun never sets in my realm.”
          But even then nobody would have thought the sun to be were you place it 😉

          • I don’t know about Louis XIV, but until not too long ago the British were saying that the sun never sets on the British Empire. And before that the Spanish were talking about their “empire on which the sun never sets” (el imperio en el que nunca se pone el sol).

          • Louis XIV was explicitly known as “le Roi-Soleil”.

  4. I really have to smirk a bit at seeing Boeing highlighting “conventional flight control”, “no RAM air turbine” as a plus for the 737. If they really only added weight, fuss and annoyance, why did they introduce them in the 777 and 787?
    Same with “smaller service doors” and “lower ground clearance”, which they suddenly try to paint as being advantageous.
    Utterly bizarre.

    • Conventional flight controls are heavier than FBW. And by the way the MAX will have FBW spoilers. But the RAT will add weight, and I think it is required by the new regulations. The 737 being low to the ground does not need escape slides, which saves weight. The smaller service doors also save weight. With a contemporary fuselage design Boeing would lose those legacy advantages.

    • The 737 being lower to the ground would translate into less weight irregardless of the lack of escape slides or smaller service doors. Shorter landing gear posts means they can be more structurally efficient. It also means the attachment points can be lighter along with the part of the wing box between the main gear. This, in turn, translates into lighter fuselage hardpoints for the wing attachment.

      There is a huge structural benefit to having the the aircraft sit low on it’s gear. However, this must be traded off against the benefit of using high BPR engines with large fan diameters. One does not want to vacuum the runway on take-off.

      • Actuall,y when you look at the figures the A320 has lower landing gear weight than the B737NG (that without carbon brakes). At least the figures I know, which are always difficult as weight accounting of landing gears differs between companies. The actual landing gear length affects only about 20% of the components. The major influential figure is the weight at landing. Sizing load cases include some other sometimes scary requirements that no car would survive. Boeing introduced carbon brakes quite recently. They apparently didn’t feel the need to do that earlier, quite luxurious to disregard technology.
        FBW is not necessarily lighter in weight. You need quite some electronics (triple redundant inertial reference unit for example), which then need electricity (and cooling). In essence, the larger the aircraft the better FBW gets. For small aircraft, there is hardly any weight advantage.

      • I was referring to how the weight of the gear strut changes with strut length for a given technology generation when everything else is equal. Of course there are many other things that contribute to the total weight of the gear.

        Since the gear, at least as far as I can remember, is a very long lead time item in the development of an aircraft, I can see why Boeing might have been reluctant to change it on the 737.

    • Agree!
      I am pretty amazed by this slide. one could think that it was written by Airbus to ridicule the 737 as an old era, obsolete technology design!

      At least we won’t be able to say that Boeing did not know of the 737 limitations.

  5. “Indisputable, however, is the seat advantage the 737-800 has over the A320.”
    That seems reasonable, the 737-800 has additional cabin length that can be used for extra seats.

    Now for the 737-900 and A321, the latter has a nearly 2 meters longer cabin. How come the seatcount difference used for the comparison is only 3 seats? Seems cheesy.. did anyone ask the Boeing spokesman?

    KCT, about the often claimed range advantage of the 737NG, try apples to apples. Put 200 passengers (20t) in a 737-900ER and a A321. The A321 flies further. Below 5 hours the A321 can carry 5t more payload and we are not even talking about runway restrictions. Lately the A321 has found many customer among 737NG operators. With the big GTF’s and sharklets, the performance difference will grow further.

    http://i15.photobucket.com/albums/a357/thezeke/range%20payload/f3a7d034.png

    • “Now for the 737-900 and A321, the latter has a nearly 2 meters longer cabin. How come the seatcount difference used for the comparison is only 3 seats? Seems cheesy.. did anyone ask the Boeing spokesman?”

      Airbus uses a higher seat count for the A321 than Boeing does. This is typical of the seat “games” we’ve written about. We haven’t gotten around to this yet, but we will. US Airways configures its A321s with 187 seats, for example.

  6. The lack of ram air turbine is caused by the manual reversion, the Boeing can fly in absence of all hydraulics. These small advantages of the 1960ies certification environment give the B737 so much advantages (both in performance, but also in cost), that Boeing cannot find a better alternative. A new B737 would grow even beyond the A320 in terms of weight, complexity and cost, and Boeing knows that.

    • The ability to fly without hydraulics is why the 737 does not need a RAT, but I think if anyone would build a cable driven system today (not that anyone would) they wouldn’t need a RAT. It is not a certification issue. The weight advantage of FBW is less than commonly thought – replacing cables with copper wires isn’t a big advantage and the requirements for redundancy (like RAT’s) also chips away at the weight advantage. The real benefit in FBW is the ability to tune the performance of the aircraft and for crew workload.

      Stepping up to the new regulations does require more weight in some areas, but even the A320 is enjoying that advantage over a NSA. The NG had to step up to many of the new requirements since is was a new derivative – one of which is the over-wing hatches (instead of plug doors). I haven’t been able to find where your escape slide are comming from, but rafts in the overhead is a customer option on that is rarely selected.

      The great selling point of the larger fuselage for passenger comfort also means more structural weight (all else being equal) and it means punching a bigger hole in the air. So it comes at a cost.
      In addition to the previous mentioned landing gear related advantages: The 737 does not use MLG doors (the wheels sit flush to the fairing), and bigger engines are more efficient but weigh more and need more wing structure. There are good technical reasons for the weight differences and much of airliner design is a series of comprimizes.

      • The over-wing escape slides are required when the aircraft wing upper surface is above a nominal height. The 737 does not need them, nor the E-Jet and the CRJ. But they are required for aircraft that sit higher, like the A320 and the CSeries.

    • I was under the impression that certain types of FBW systems can allow the use of a smaller empennage and control surfaces, thus providing significant weight reduction because they can compensate for the slightly relaxed stability margins. I could be wrong, however.

      I find it hard to believe that the 737 NG is not certified to the same fatigue life standards as the A320, given that they were developed around the same time.

      • The new wings on the NG might have to be certified to the latest fatigue standards, but not the fuselage.

      • I would also be surprised if Boeing did not modify the fuselage structure of the 737NG in response to the Aloha Airlines 737 “convertible” incident.

        • My understanding is that Boeing has altered the manufacturing process for the affected areas. But the problem was more a maintenance issue than an engineering flaw.

      • Boeing is changing the shape of the fuselage afterbody. If this includes part of the pressurized section, then it seems the fuselage would have to be certified to the latest standard. However, I’m not sure the pressurized section will be affected by the shape changes.

        • The pressure bulkhead actually separates the cabin from the afterbody. So any modifications of the latter should not affect pressurization.

  7. CBL :
    Agree!
    I am pretty amazed by this slide. one could think that it was written by Airbus to ridicule the 737 as an old era, obsolete technology design!
    At least we won’t be able to say that Boeing did not know of the 737 limitations.

    Maybe not every airline in world is looking for the most advanced materials, avionics and maintenance infrastructure.. many shiver at the thought of dented CRFP NB ribs or faulty FMS boxes on faraway outstations.

    • You don’t get it. This was simply funny.

      Any “mine is better than yours” discussion is pointless to my eyes, kid games.

  8. The Achilles heel for the MAX in my opinion will be the issue of noise levels.
    Remember that noise is on a logarithm scale( 5dBA reduction if I recall is a 50% reduction in noise) and I simply cannot see how the LEAP X can be remotely close to the GTF in terms of noise levels.
    Would not be surprised to see an Airbus technician somewhere close to the runway when the Bombardier C100 takes to the sky with his “Tandy” dBA meter.
    Seriously, I expect the GTF to re-write the rules on airport noise. It is likely to be close to an ATR or Dash-8 in footprint, maybe even better on take off due to its greater rate of climb.
    Will negate any fuel burn issues, and unfortunately as we speak is not available for MAX.
    I believe the 2/1 ratio between the NEO and MAX will continue, but expect the GTF to become the dominant engine.

  9. Andrew :
    Would not be surprised to see an Airbus technician somewhere close to the runway when the Bombardier C100 takes to the sky with his “Tandy” dBA meter.

    Airbus already has a lot of experience with the GTF engine. They have borrowed one from P&W to test it on an A340. So they already have a pretty good idea how quiet it is. And it is following this extensive flight testing campaign that they have decided to offer it on the A320.

  10. “We don’t have landing gear doors on the plane. That contributes to hundreds of pounds of weight advantage.”
    isn’t this massive BS from BOEING PR?
    No doors obviously means lots of additional aerodynamic drag
    It also means hundreds of thousands of pounds of unnecessary burnt fuel over the aircraft’s life!
    No civil plane manufacturer would dare design to day a plane without landing gear cover!
    Even a slowish turboprop has them!

    • “No doors obviously means lots of additional aerodynamic drag
      It also means hundreds of thousands of pounds of unnecessary burnt fuel over the aircraft’s life!”

      Not necessarily true. If properly tailored, an open gearwell design can be very low drag. Resonances within the well, however, can also be very difficult to manage, hence closed gearwell solutions.

  11. No RAT, no slides, no landing gear doors, low height, mechanical controls…

    I’m looking forward to seeing if Boeing sticks to these “advantages” with the NSA.

  12. Mike Bohnet :
    Since the gear, at least as far as I can remember, is a very long lead time item in the development of an aircraft, I can see why Boeing might have been reluctant to change it on the 737.

    If Boeing had to change the gear on the 737 it would be to have a taller one in order to accommodate the new generation of engines under the wing. But to do so they would have to redesign the centre wing box, around which the aircraft is built. A major undertaking, to say the least. And with a taller gear the 737 would need over-wing evacuation slides. So they would end up with a heavier aircraft because of the re-disigned CWB, taller gear and slides. And a new CWB would probably require a re-disign of the fuselage interface, which would likely compromise the legacy privileges. It’s a simple proposition, but one which engenders complex ramifications.

    • I agree with what you are saying. Another indication of why sitting lower to the ground means less weight. Some people are making fun of it because they think it is just old, but there are very good reasons (not just from a grandfathering point of view) why it can be advantageous.

      • I wouldn’t call it an advantage. Maybe a trade-off. The question is if they’re going keep low for their replacement. Right now, there’s nothing much they can do to change it, and so have to make the most of it.

      • It would not be a trade-off if it did not have advantages to go along with disadvantages.

        Whether Boeing keeps going low on the replacement is an interesting question. In my opinion, Boeing seems to be trending towards lower sitting aircraft these days. The 787, in particular, strikes me as sitting low, although that is relative to it’s size because a person can walk upright under the fuselage. If the 787-8 looks low, the stretched versions will seem even lower. Also, the pylons already look like they are extremely short in the vertical direction, so the aircraft is probably sitting as low as it could possibly get.

      • Oh yes, I forgot about the replacement. I heard somewhere that the NSA was a high wing configuration. Is that correct?

        • Technically speaking a high wing aircraft is one that looks like the Avro RJ for example, or the C-5 Galaxy. But the NSA would only need to sit high enough to fit any suitable engine with a large diameter fan under the wing. So the NSA would most likely look like the current 737, but would sit much higher from the ground to provide adequate clearance

          The utopists among us think that the NSA will be fitted with the “next generation” of engines, which many, excluding myself, believe will be of the propfan or unducted fan variety. In that case the NSA could have any kind of wing because this type of engine would most likely be installed somewhere else on the aircraft.

          The realists among us, including myself, think that the future belongs to intrinsically quiet engines. For the time being there is only one variety around and it is the GTF. For the same reason that no one would want to design an engine that burns a lot of fuel, no one in his right mind would want to design an engine that makes a lot of noise.

      • Thank you Normand. I did mean high wing such as most military transports. SO , sounds like the NSA was going to be a low wing config, sitting higher, like the A320. Makes sense since high wings usually need a t-tail or a raised afterbody to minimize wing/stab interference.

  13. Late comment, I’m not expecting this to be posted, just sharing a thought, anyways:

    The 737 naturally sits lower to the ground meaning that one could easily slide off the wing (trailing edge) to the ground with very little fuss and very little-to-no injury to show for the leap — with out the escape slide. Further, the over wing escape slide cannot be used as a life raft because of its curvature/shape – mostly.

    The escape slides on the forward and rear doors can double as slide rafts — on larger aircraft.

    If we look at US Airways flight 1549, we see that passengers used the over wing exit & forward slides as temporary rafts while rescue converged on their location in the Hudson river. Some passengers also stood on the aircraft’s wings. Because the slides are fixed to the aircraft, they sunk with the aircraft when it went under.

    We’ll probably see some changes with this safety equipment, especially with the exit slides becoming slide rafts (excluding the over wing exit equipment) in order to satisfy regulatory authorities where these narrowbody aircraft are operated on ETOPs missions (over water).

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