Airbus comes up for air, responds to Boeing’s Form 41 reliance

Airbus came up for air from the Paris Air Show and provided this response on the DOT Form 41 debate. Readers can now compare closely Boeing’s response to our queries with the Airbus response and draw their own conclusions. As with Boeing, we print their verbatim replies to our questions.

DOT form 41 Maintenance cost comparison

Boeing uses F41 data of the period 2004 to 2011 to demonstrate lower maintenance cost of the 737NG compared to the A320. Without debating about the relevancy of F41 data for aircraft maintenance performance and the “correctness” of the data, let’s have a look at the reported F41 data from the point in time when the A320 entered the US market (1991).

DOT 41_1

We see why Boeing is focusing on the 2004 to 2011 period, the reported data are at the first glance favourable for the 737NG.

However, the NG entered in the market in 1998, seven year later than the A320, hence at any point in time the graph compares aircraft with at least a seven year age difference. Is this a “like for like” comparison?

Let’s just shift the 737NG curve to the left, starting in the same year than the A320, in 1991:

DOT 41_2

The picture does now look quite different, but money over time does not have the same value and this is in the above graph penalising the NG.

To be fair the reported cost data need to be harmonised respecting the economic conditions. Let’s put all reported data in year 1991 economic condition:

DOT 41_3

At the time A320 entered the US market barely any MRO capacity was in place. This has changed over the years and from a certain point in time MROs started to make money with performing maintenance work on the A320. Competition started to take place between the MRO’s, which impacted the pricing of maintenance work in reducing the money spent for the operators. For the NG the maintenance market condition has not been the same. Due to the derivative nature of the NG to the 737 Classic a wide MRO base has been proposing maintenance work on the NG right form the entry into service in 1998.

The graph below illustrates this effect in showing the evolution of independent MROs in the US market.

Text Box: Increasing competition  - lower priceDOT 41_4

Another fact leads to lower maintenance cost for the A320 compared to the NG. It is the solid structure, which has been fully fatigue tested during the certification of the aircraft. An advantage the NG does not have, because again due to the derivative nature of the NG compared to the Classic, no full fatigue test has been performed and certification of the airframe has been obtain by “grandfather rights”.

Some quotes from leading MRO’s illustrate the well maturing structure of the A320:

A320 v 737 Maintenance

Conclusion:

·         Instead of focusing on the “sweat spot” for the NG, data of the entire reporting period must be compared

·         Comparing different fleet ages is not leading the sensible results

·         Market forces e.g. competition have an impact on maintenance cost

DOT 41_5

 The A320 airframe is better maturing than the NG and improvements on the A320 are showing tangible results.

71 Comments on “Airbus comes up for air, responds to Boeing’s Form 41 reliance

  1. This study is enlightening. It is a great lesson that demonstrates the art of comparing apples with apples, and oranges with oranges. The moral of the story is that one can use a graph to say just about anything. Graphing and rigor should always go hand in hand. Graphs are mathematical representations that must be used with mathematical accuracy and truthfulness.

  2. I was amazed in the past by Boeings seatcount and per seat cost comparisons (- using tiny “typical” seats at their own-) and Boeings superior ranges (-without taking into account payload-).

    I have started wondering where Boeing sees the balance between OverWhelming WallstreetAnalysts / Mainstream Press and looking unreliable in the eyes of the airline industry, because of knowingly comparing Apples & Oranges. Often telling half the story is lying.

    That can’t be good Brand marketing Randy?

    • Airbus relies on IATA data. This data is even worse. At least with Form 41 you have a airlines you use similar account measures, the same currencies, etc. IATA relies on data comes from carriers all over the world where accounting is more magical than factual. This comes from someone who had to supply IATA data to them during my airline days and we operated in a G8 economy.

      • Boeing, until this year, also used IATA data but discontinued because the data it had was 2006-2009 and now too old.

      • And I used to to receive this data during my time at IATA.. We always had a few doubts about quality of the data, but other than F41 no-one had ex-USA data

  3. How is it even possible that the A320 could have a maintenance advantage over the 737NG? The chart above indicates that the NG had a 46% advantage and now has a 20% disadvantage. A swing of over 60%? Not the slighest bit misleading or unrealistic (sarcasm).

    The 737 maintenance advantage:
    Newer airframe
    Lighter weight
    Simple-value added design
    Fewer required components for dispatch
    Longer intervals with less tasks to perform

    • cms did you read the article or did you avoid that, so you can stick to the Boeing line?

      • If you believe that an airplanes maintenance costs can change by 60%, by doing nothing physical to the airplane you have to drinking some Airbus kool-aid.

    • I think the lesson here is:
      data can be (ab)used to support any conclusion.

      reality is the only check that matters and it shows both airframes are selling like hotcakes.

  4. Form41 has never been intended to be an airplane-to-airplane comparison tool, but an airline-to-airline tool. Data is raw, most of the times not verified by either the airline or DoT, and several key factors such as age of aircraft and stage length are not applied.

  5. So, am I reading the Airbus argument correctly as saying that comparing maintenance costs of a new A320 against those of a 7 year old 737 is more accurate than comparing the costs of a new A320 vs new 737? That is what it seems they are arguing to me?

    • I think you have it reversed. What is demonstrated here is that Boeing was comparing a brand new 737 versus a seven year old A320. The correct and honest way of doing this is to compare aircraft of the same age. But it does not stop there. One has also to take into account the evolution of maintenance costs over time and include exterior factors like the lower costs that are associated with higher competition; or conversely, the higher costs that are associated with less competition among maintenance providers.

  6. cms :
    How is it even possible that the A320 could have a maintenance advantage over the 737NG?

    It is “obviously” impossible according to the Boeing mythology. The latter was built on the fact that Boeing produced exceptionally strong aircraft in the 1950s and 1960s. And therefore quickly became the industry standard. It had, and still has, a REPUTATION. And when the various Airbus models came on the market they were inevitably gauged against that Boeing standard. But it did not take into account the fact that aircraft engineering had considerably evolved over the years.

    Today we know with a much higher degree of certainty how to design any given part so that it will not fail within a certain margin. In the old days there was a much higher degree of uncertainty and aircraft were designed with correspondingly higher margins. On the other hand, modern aircraft are better tested for longevity, and theoretical models are more rigorously validated in the labs (or invalidated, like in the case of the 787 wing root). Hence the advantage the A320 has over the 737: At the time it was designed, it was tested more intensely and with a higher degree of accuracy, simply because it had the meet the contemporary design standards.

    • The A320 is heavier because the design incorporates the increased fatigue requirements. Maybe someone remembers the occurrences of fatigue damage on Southwest Airlines. Aloha (a B737-200 lost parts of the fuselage roof, one flight attendant perished) is not a useful example due to special circumstances.

      • Why do you have in mind with “special circumstances”? Salty environment? Poor maintenance? High cycles (Milk Run from one island to the other)?

    • Normand, if you dig a little further you would see that the 737NG started to fly 10 years after the A320. Boeing made a lot of changes to the systems and structure to reduce maintenance costs for the NG as customers demanded. Learning from many past models including the high tech 777, it was also tested at the same stringent standards of other airplanes. There are Classics still flying around the world. NGs will have long lives too. Check back with Toulouse for your next talking point.

      • bfd, I am in complete agreement. The 737NG is nothing like its predecessor, the 737 Classic. The only commonality is the fuselage diameter. Alloys, corrosion protection, manufacturing process, design and validation are all the latest standard. Something the A320 cannot boast. (Hence heavy checks at 6-yrs on the A320).

  7. It basically says that when sufficient competition exists the maintenance cost converge. The A320 is apparently superior in airframe maintenance when it ages. The B737 will hold an advantage in component maintenance (as it has less). I would assume that when you count in the seat difference (which does exist, even if it is less than Boeing says), I would say both are roughly the same. Thanks to Scott to this very informative series of posts and the guts to ask tough questions and bring them to public domain. Great job!

  8. The third graph, overlaying # of A320 MRO’s over the costs of each, normalized for 1991 costs (removing inflation) just shreds Boeing’s PR and reveals it for the chicanery it is. To be honest, it would have been even more informative to show the # of B737 MRO’s, but it’s safe to say that they had a signifigant early lead. And A320’s point of equality happened at 4 MRO’s (and I think even at the point of 3 MRO’s, or even 2 MRO’s, they were already on the same trajectory). Perhaps Scott or somebody could slap together a graph overlaying Boeing MRO #’s?

    • “Shredding Boeing’s PR and reveals the chicanery it is.” You must be John Leahy. Comparing DOT data is one of many sources, but normalization for age, labor rates, flight time and utilization to show a comparison that is based on airplane characteristics. I wonder if Airbus is doing this with the data for fair comparison. If not, that would be chicanery. For an airplane to have a 60% cost improvement versus its competitor with the same design and parts seems to be a pretty big stretch…

      • “For an airplane to have a 60% cost improvement versus…”
        You are misquoting there. I don’t know if it is deliberate or not.

        cms was stating that there was a swing of 60% which resulted in the A320 having a 20% cost advantage over the 737.

        Furthermore Airbus is merely answering some of Scott’s questions, not trying to score PR points with anyone, unless they happen to be reading it here.

      • So are you saying that a) you don’t believe an older aircraft costs more to maintain that a newer one, b) that the value of money changes over time, and c) that competition in a market helps to reduce prices?

  9. Could it be that the NG cost advantage diminishes over the years because they are flown on shorter stages and therefore have higher cycles at the same age?

    • Another factor could be an increasing trend to outsource mro. More demand would allow room for more mro providers, which increases competition.

    • You raise a valid question. To look at these trends at face value can be misleading as it assumes all operators for both models fly at the same conditions – yearly utilization, flight length, operating environment, OEWs, etc. Maintenance costs for the same aircraft type will be different for a high cycle operator versus a long haul operator.

  10. So the number of MROs offering maintenance work seems to have a heavy impact on maintenance prices. When thinking about new market entrants like comac, mitsubushi etc this should be a heavy entry barrier.

    But airlines with inhouse mro are not impacted

    • The one airline I know with a big inhouse mro ordered lately 100 A320. Also there is a learning curve of how to do things quicker than at first time. The one airline also operates with cargo and hubs. So 45”LD3 may have been beneficial. Boeing moved from LD2 to LD3 on B787. Ryanair operates with no containers, no hubs, no cargo…

      • Ryanair also flies shorter stages in general, while LH flies their A320 series as far as Cairo, Amman, Istanbul, Tblisi, Moscow.

      • Ryan Air is a people mover that heavily squeezes customers on baggage.
        i.e. Ryan Air transports selfloading PAX and that unavoidable handfull of paid bags.

    • Airlines with in house mro are impacted by the investment required to get accustomed to a (more) new airframe

      • Indeed, and they probably need a minimum fleet size to make it work. If in-house MRO wasn’t affected by these things, why would Air France have thrown a wobbly over RR only on the A350?

  11. Interesting analysis. However using present values for comparable aircraft of the same age would probably give quite different results. [Note: while using the dollar value of 1991 accounts for inflation, it does not reflect the time value of monet]

  12. cms :
    bfd, I am in complete agreement. The 737NG is nothing like its predecessor, the 737 Classic. The only commonality is the fuselage diameter. Alloys, corrosion protection, manufacturing process, design and validation are all the latest standard. Something the A320 cannot boast. (Hence heavy checks at 6-yrs on the A320).

    CMS, lots of things on the NG are new. Lots are not new, the same as earlier 737s or only different dash numbers. The promoted 737 commonality.

    Something the A320 cannot boast. (Hence heavy checks at 6-yrs on the A320)

    Maintenance checks are customized for A320s these days. Airlines choose the maintenance plans that best fit their operations. Some do heavy checks every 12 years now. Airbus is working to extend service live to 180.000 hrs. Far longer then any 737.

    http://www.asianaviation.com/articles/4/Airbus-plans-A320-life-extension

    • the 737 has the same flexibility in its maintenance plan too to give flexibility to its operators. the good news is that they will not have to it as often because the time between checks is longer. you cannot do a heavy check every 12 years on an a A320, only airplanes like a 787 with composites can reach this. I have seen an A320 do a heavy check every 79 months, but a bunch of other maintenance tasks that had to be done a 72 months fell out and had to be put in a c-check.

      So what if Airbus is extending the life of an A320 to 180000 hours? The 737 can have a similar life. At 180000 the airplane will be over 50 years old. I doubt many airlines will have airplanes that old in their fleet. They replace them earlier mostly before 20 years due to fuel prices, regulatory issues and airline brand. There are 737-200s flying regular service in Yellowknife Canada.

  13. If you take the last graph and extrapolate the airbus advantage out to the 20 year estimated life expectancy of the airframe, It looks like the areas under the Boeing advantage and Airbus advantage curves would be similar, assuming that the airbus advantage continues on at the same rate. This would be another way to assess who is better. Unfortunately we do not yet have that data on Airbus vs Boeing.

    • From a life cycle cost perspective – using present values, the aircraft giving superior cost advantage in the initial segment of the 20 year estimated life could well be more preferable. I would imagine that, for airlines, what matters most are life cycle costs

      • for a buying decission you would have to compare planes from the same manufacturing interval ( and keeping in mind future developement ) . i.e. Apples to Apples 😉

  14. Anyone know what happens to a 737NG around the 9/10 year mark that starts to push its prices up so much?

    • Unscheduled maintainance to fix officially not expected structural deterioration?
      ( forex decompressions from fuselage/skin structural failures. even if the actual
      damage is negligible resultant inspections on the cohort are invariably expensive)

      FAA being a bit too close to Boeing should not be limited to the 787.
      IMHO it probably permeats Boeings portfolio. There seems to be a lot less
      hard backing behind Boeing’s reputation than one would expect from PR
      ( direct and also the floods of astroturfing injected into any discussion ).

      • The material provided leaves a lot of room for speculation, as you are doing when suggesting “unscheduled maintenance to fix officially not expected structural deterioration”. As the airplane enters later years, there are structural block checks that occur that consume large amounts of labor and material. I would be speculating if I said that this is what is happening around the 9/10 year mark, but it would make sense that costs increase on an airplane after the honeymoon period.

  15. So you think random wear and tear then, rather than 1, 2 or half a dozen specific design ‘weaknesses’?

    Also, any info on whether the EASA/Airbus relationship operates similarly to the FAA/Boeing relationship (re level of independence etc.)?

    • He, having “ring pull opener” faults is not “random wear and tear” . IMHO and all that jazz.

      Then:
      If you could be so kind as to bring some EASA subjugated to Airbus examples up?

  16. This response by Airbus is unbelievable! It’s obviously so full of crap. The assumptions are wrong, the methodology is wrong, and not surprisingly, the conclusions are wrong. What is more unbelievable, in my humble opinion, is that no one else here has pointed this out yet. I guess Airbus PR has successfully achieved its goal.

    First of all, let’s look at Airbus’ wrong assumptions:

    “However, the NG entered in the market in 1998, seven year later than the A320, hence at any point in time the graph compares aircraft with at least a seven year age difference.”

    This statement is a lie. It assumes that we are too dumb to understand how averages work or how airliners enter the fleet. The Form 41 data presented is a year by year comparison of the entire US operational 737NG fleet with the entire US operational A320 fleet. As such, the average age of the A320 fleet was not 7 years when the first 737NG entered service in 1998, it was considerably younger than that. Were there 7 year old A320’s in 1998? Sure there were, but there were also A320’s in the fleet that were only a couple years old or even brand new. The key concept that Airbus PR is distorting here is the AVERAGE age of the fleet.

    Consider this example which neglects aircraft retirements from the fleets. If A320’s entered the fleet at a constant rate/year (flat EIS profile) for 21 years starting in 1991, the average age of the A320 fleet would be 10.5 years. Also, if 737NG’s entered the fleet at a constant rate/year (does not need to be the same rate as the A320’s) for 14 years starting in 1998, the average age of the 737 NG fleet would be 7 years. Thus, under flat EIS profiles, the A320 fleet is only 3.5 years older than the 737NG fleet on average, not 7 years!

    The only realistic way the A320 fleet could be 7 years older than the 737NG fleet is if both fleets have similar (no need to be flat) EIS profiles, just offset by 7 years, AND those EIS profiles taper to zero in less than 14 years after initial EIS. Are the EIS profiles flat, you ask? No, not for a particular airline, but I would say they are approximately flat if the fleet encompasses all US airlines. I guess there is the possibility that the A320 EIS profile could be skewed early and the 737NG EIS profile could be skewed late. This could possibly result in a greater than 7 year age difference between the two fleets, but I find this to be very unlikely considering US airlines are still receiving new units of both types.

    I did a quick check of the average ages of the US A320 and 373NG fleets. I used average age data on individual US airlines as of 2012 from Airfleets.net and computed a weighted average age of the entire US fleets of both types. The answer was initially surprising. As of 2012, the average age of the US A320 family fleet was 10.7 years and the average age of the US 737NG family fleet was 8.1 years. This is a difference of only 2.6 years, not far from the flat EIS profile example that I gave above. This small difference is less surprising considering aircraft retirements also affect the average age of the fleet. Assuming that the oldest aircraft are retired first, retirements will serve to make both fleets younger, and the age delta will most likely get smaller.

    Preceding the Airbus lie that the graph compares aircraft with AT LEAST a 7 year age difference, Airbus PR tries to assert that Boeing is focusing on the 2004 to 2011 time period. I see nothing in Boeing’s slides or in Boeing’s answers to Scott’s questions that suggest that Boeing is only focusing on that period. Perhaps Airbus is trying to set us up for their funky slide-the-data-back-in-time trick that they try to slip by us.

    This brings up Airbus’ absolutely ridiculous methodology:

    “Let’s just shift the 737NG curve to the left, starting in the same year than the A320, in 1991: The picture does now look quite different,….”

    You think! The picture does indeed look quite different because it no longer reflects reality. Even if there was a 7 year difference in the average ages of the two fleets during every year under question, which there wasn’t, shifting one set of data in time is a disingenuous and lazy way of trying to compensate for it. Airbus makes a big deal about how market forces, such as competition, impact the maintenance cost, but shifting one set of data in time relative to the other means that those market forces and conditions (other than inflation) will not be properly accounted for. Market forces such as competition can change a lot in 7 years. So much for an apples to apples comparison!

    Another problem with shifting data sets in time to compensate for fleet age is that the difference in fleet age is not always the same year to year. As I showed above, the difference in average age between the two fleets was only 2.6 years in 2012. This age difference could very well have been greater during other years covered by the data set, but it all depends on the EIS profile and retirement profile of each type.

    Boeing’s description of their methodology, on the other hand, at least sounds spot on.

    “There are many differences in the fleets of different airlines, like airplane age and the average stage length (Fhrs/Trip). Both affect maintenance costs. To enable true comparison, maintenance cost is normalized for a common airplane age….
    Similarly, costs are normalized for stage length and some other factors. All these normalizing processes are approved by the IATA Maintenance Cost Task Force of which both Boeing and Airbus are also members and uniformly used by most of the industry. We compare costs and do modeling in our tools on basis of the normalized costs…
    Maintenance cost data is normalized to the same age level for instances where the airplane ages are different. This is done for each airline and then grouped together. The analysis ensured we were comparing like-aged aircraft not the entire fleet.”

    Normalization processes are typical for these types of cost analyses, however, they require a lot of detailed book-keeping that does not fit nicely on a PR slide. While Boeing does not show their methodology, it is better than trying to pass off a ridiculous one.

    Finally Airbus’ conclusions:

    “Instead of focusing on the “sweat spot” for the NG, data of the entire reporting period must be compared”

    How about the A320 maintenance data for 2005 through 2011? Where did that data run off to in their comparison?

    “Comparing different fleet ages is not leading the sensible results”

    Very true, but assuming that the average fleet age difference is equal to the difference in initial EIS, and preferentially treating one data set by sliding in time does not lead to sensible results either. It just makes things worse, and their maintenance cost assertions now have zero credibility.

    “Market forces e.g. competition have an impact on maintenance cost”

    True as well, but we will never know from Airbus what those impacts are because this so called “analysis” was so crappily done. Again, their credibility is lost.

    “Another fact leads to lower maintenance cost for the A320 compared to the NG. It is the solid structure, which has been fully fatigue tested during the certification of the aircraft. An advantage the NG does not have, because again due to the derivative nature of the NG compared to the Classic, no full fatigue test has been performed and certification of the airframe has been obtain by “grandfather rights”.

    I love it! This must have been JL’s contribution to this most excellent piece of work. Yeah, Boeing has never done a full fatigue test on the 737, right.

    There has been a lot of criticism of Boeing’s PR practices lately in this forum. Most of it is probably well deserved. Where is the criticism for this piece of PR beauty from Airbus?

    • So let’s put this another way, Airbus should have merely said, look, here are the maintenance cost curves, per DOT Form 41 for the first 14 years after EIS for the A320 and here are the maintenance cost curves, per DOT Form 41 for the first 14 years after EIS for the 737NG. Obviously there are other factors but please, lets not get our shorts all twisted over this one as both OEMs are going to use this data to make their products look the best.

      Let’s look at something else that many seemed to have overlooked, the quote from Lufthansa Technik, “LHT – Lufthansa Technik (…) has found less significant corrosion or fatigue related fuselage structure work arising on A320s than on Boeing 737s of similar age.”
      Is that more Airbus spin?

      • “Obviously there are other factors”

        You got that right! Like the fact that the data shows the maintenance costs for both manufacturers curves markedly up after 2004. Part of the data Airbus obviously does not want to highlight.

      • “…lets not get our shorts all twisted over this one…”

        I realize my response was strong, but the strength of my response was only proportional to the stupidity of what Airbus put out.

        Besides, if my old thesis adviser would have seen this so called “analysis” and known that I follow this blog but didn’t critically respond, I’m certain he would try to get my degree revoked.

    • Now do the same carefull analysis for Boeing’s itty bit 😉

      ( I would take Airbus’ reply to be a satirisation of Boieng’s piece )

    • Mike Bohnet :
      While Boeing does not show their methodology, it is better than trying to pass off a ridiculous one.

      What your piece makes quite clear is that we need an analysis which would be carried out by an independent party that would have been pre-selected by both manufacturers. And also one that would detail its methodology so that neither Boeing or Airbus would be able to contest its findings.

      Mike Bohnet :
      (…) because again due to the derivative nature of the NG compared to the Classic, no full fatigue test has been performed and certification of the airframe has been obtain by “grandfather rights”.
      I love it! This must have been JL’s contribution to this most excellent piece of work. Yeah, Boeing has never done a full fatigue test on the 737, right.

      The “grandfather rights” don’t necessarily imply that Boeing never conducted any fatigue test at all on the 737. What might be different is what was exactly required at the time (1968). But that would not have prevented Boeing from conducting more stringent tests of its own initiative on the NG, or the MAX for that matter, than it had to.

      The main difference between the 737 and the A320 is that the latter is necessarily heavier because the regulations have changed in the meantime. Airbus had to make the airplane sturdier to better sustain potential crashes, as the new norms of the eighties required them to do. Thus making the airplane heavier by design. The 737 did not have, and still does not have, to submit itself to those requirements. This is the key point of the “grandfather rights”.

      But I believe that because the A320 had to be made stronger and heavier, it might actually benefit from that in terms of long-term durability of its airframe structure.

      • The whole reason I brought this up is because Airbus is claiming in their response that NO full fatigue test has been performed on the 737, an obvious distortion of the truth that people in this forum seem to be OK with.

        • You have a reference for full fatigue testing on the 737 “classic” and/or 737NG ?
          ( And how stringent were the requirements in the initial certification for the jurassic?)

          If you go through the AD history of any version of the 737 you will find that fatique cracking
          is a relatively constant feature for this type. ( “Boeing builds them to last” is a carefully pampered myth imho )
          In recent years this even passed the “brain blood barrier” into the press.

        • Woody, I read basically the same thing around that time in Aviation Week. The situation with the 737 is very well described here.

      • The article quotes a Boeing spokesman as saying that the 737 NG fuselage has some significant design changes from the 737 classic.

        “Newer models of 737s are still being built. These models, according to Boeing spokesman Doug Alder, have a different design that won’t result in the same joint failure seen in classic 737s.”

        Doesn’t this mean that the 737 NG fuselage would have had to be recertified?

        • No need for recertification. It is still the same lap joint technology. I think the changes have more to do with the manufacturing process than anything else. With lap joint the strength comes from the bonding material (PRC). When not properly applied the rivets have to take up the load, and after some time the skin starts to tear apart around the rivets. With proper bonding the load is distributed more evenly across the overlap. I believe that was why the failures occurred earlier than expected. It is not that the calculations were wrong. In other words it’s not a design flaw. Maybe a bad design choice, but not a bad design per say. My understanding is that the manufacturing process of the lap joint had to be revised.

    • Thanks for compiling all the data and pointing out potential flaws Mike. Very worthwhile.

      The Airbus methodology remains valid, if crude, though, because airliner maintenance is not done by average years (ie it isn’t smooth, but lumpy, via A, B, C & D checks). So, assuming the fleetwide utilisation profiles are comparable, a comparable percentage of each type will have processed through A, B, C & D checks respectively at more or less the same number of months post introduction.

      As for issues of changes in environment over 7 years (the apples vs apples you mention), certainly a valid point in absolute cost terms. Perhaps someone with MRO exprience during 91-98 has some insight?

      • Does someone have enhanced access to airfleets.net or similar for
        extracting the US based A320 and 737NG aquisitions?
        I’d be willing to massage that data into showing something sensible.

      • Thanks for your response Woody, and for noticing the fleet age compilation. It did take some time.

        I will have to respectfully disagree with your assertion that is quoted below:

        “So, assuming the fleetwide utilisation profiles are comparable, a comparable percentage of each type will have processed through A, B, C & D checks respectively at more or less the same number of months post introduction.”

        I think I get what you are trying to say, that if both utilization profiles are similar, but only one is delayed by 7 years from the other, then the percentage of of each type that have passed through a given maintenance check will be roughly the same, only offset by 7 years. However, this can only be true if there are no longer any new aircraft entering either fleet.

        You would be right, for example, if all the A320’s were delivered to the US fleet in, let’s say, 10 years (1991-2000) and if all the 737NG’s were also delivered in 10 years (1998-2007), just offset by 7 years. The problem is that there are still new frames of both types entering the fleet. These new frames will continually lower the percentage of each type that has passed through a given maintenance check relative to the types initial EIS.

        While it is true that maintenance costs are lumpy, the data cited is average maintenance cost over the entire fleet of each type for a given year. So, for a given year, one has to look at the average point in the maintenance schedule for each types fleet in order to make a comparison. Even if I thought that shifting one data set relative to the other in order to account for this was valid, I would argue that shifting the data set by the full 7 years is not. The shift should be more like 3.5 years.

        This is another reason why I think Boeing’s answers to Scott’s questions are way better than Airbus’, and that Boeing really understands the essentially elements required to perform a good analysis. Boeing actually mentions the average stage length, which can be used relate the aircraft’s chronological age to the part of its “maintenance age” that is dependent on hours or cycles.

        “There are many differences in the fleets of different airlines, like airplane age and the average stage length (Fhrs/Trip). Both affect maintenance costs.”

  17. Mike,
    wouldn’t your old adviser additionally have pulled your ears for taking Boeings line unreflected hook and sinker ;-?

    Someone at Boeing will have spent long nights to find just the right set of brackets
    to present a sexy argument. ( In contrast Airbus probably was lax, but hilarious enough to provide good balance )

    • No, he would not pull my ears because I did not take Boeing’s line unreflected hook and sinker, like you claim. While I was highly critical of Airbus’s so called “analysis” and therefore disagreed with their conclusions, I never, ever said I agreed with Boeing’s conclusions either. I do, however, think Boeing’s statements of how to do the analysis are correct. I hope you can appreciate the difference here.

      I think Boeing did a much better job of answering Scott’s questions than Airbus did. If I based my opinions on these answers to Scott’s questions alone, I think Boeing has more credibility on this issue than Airbus does.

  18. Maybe I should repeat this part as you seemed to have igonored it to advance your own point of view:

    “LHT – Lufthansa Technik (…) has found less significant corrosion or fatigue related fuselage structure work arising on A320s than on Boeing 737s of similar age.”

    I repeat, is that more Airbus spin?

    This is one of the most objective points you can take out of either OEM’s responses.

    • I honestly don’t know how spun up that particular quote is, although I will not take it a face value when stated within this particular work of propaganda. Context and all, you know. I briefly looked for the issue of MRO Magazine listed in the fine print but I did not find it yet. I’ll spend a little bit more time looking.

      Even if this one quote is not Airbus spin, however, it still does not invalidate my point that the rest of Airbus’ response to Scott’s questions is pure spin, and badly done spin at that.

  19. Mike Bohnet :
    The whole reason I brought this up is because Airbus is claiming in their response that NO full fatigue test has been performed on the 737, an obvious distortion of the truth that people in this forum seem to be OK with.

    That’s not how I read it. I read it to say that the 737NG has never had a full fatigue test. But I admit that one can interpret it to read that the 737 as a whole never had a full fatigue test. Which may or may not be true, I have no idea if this was required for certification in the 60s, and/or whether Boeing has done it if it wasn’t, in any case.

    • Your point about multiple interpretations of a given statement is well taken, Andreas. Both manufacturers seem to take advantage of ambiguities in wording and in definitions so they can lie, and when called on it, point out that they were misinterpreted by the other.

      I did a bit of checking on whether or not the 737 ever underwent a “full” fatigue test, and it turns out that it depends on how one defines a “full” fatigue test. Does full mean the entire full-scale airfame including forward fuselage, center fuselage, wings, gear, rear fuselage, and empennage, like is currently occurring with the 787? Or, could it mean certain full-scale airframe parts tested separately such as center fuselage plus wing, or entire fuselage only?

      If one adheres to the first definition, then Boeing has indeed never performed a “full” fatigue test on the 737. From what I’ve found, Boeing used the 727 full-scale fatigue tests for the original 737 because they had essentially identical fuselages except for the length. In the 1990’s, Boeing took a standard 737NG fuselage off the line and fatigue tested it to 225,000 cycles, three times the design life of 75,000 cycles. This test involved the fuselage only.

      Boeing is currently conducting a full-scale fatigue test of the entire P-8 structure. I suppose these results will be valid for the 737 NG, since the P-8 is based on the 737 NG.

      http://www.thedailybeast.com/newsweek/2012/03/19/is-boeing-s-737-an-airplane-prone-to-problems.html
      http://seattletimes.com/html/businesstechnology/2014691096_boeing06.html

      It is interesting to note that according to the first definition, Airbus has not performed a “full” fatigue test on the A320 either. They did the center fuselage plus wing test (EF2) separate from the rear fuselage test (EF3).

      “The concepts of the new fatigue tests have been developed based on the experience and cognitions of all former aircraft tests for Airbus and in particular the A320 EF tests about 20 years ago, when EF2 was accomplished by IABG and EF3 by Airbus Hamburg.”
      http://icaf2009.fyper.com/program/show_slot/33

      I could not find any reference to a forward fuselage (EF1) fatigue test ever being performed on an A320 back when it was first introduced. I will admit, however, that not finding a reference to it, does not necessarily mean it did not happen.

      So, while Airbus’ statement about the 737 is strictly true, it is disingenuous because the A320 failed to live up to that same strict definition.

      • Hi Mike,
        you are brushing over a detail here imho:
        design proofs for the 737 were in part grandfathered from precursor aircraft.
        all the parts for the A320 even if also separately got their own design proofs.
        ( obviously, nothing in the Airbus portfolio to borrow from anyway )

        Afaics there is a wide range of presenting information going from
        very evenly objective
        to selecting highlights
        to presenting unremarkable as highlight
        to very contrived presentations
        finally invented from whole cloth

        There is more to it than just B/W : true or lie.
        In my very personal oppinion Boeing has always been far ahead in
        scrambling up the ladder into fantasy land.

        Then there are other forces at work.
        In the German press Boeing sales found a lot more mention than the A350 First Flight
        ( and I’ve yet to see mention of the PAS fly by in mainstream media like Zeit, der Spiegel, ..)

  20. I’ve been trying to replicate the above data and make similar comparisons between other a/c but am yet to get anywhere close.

    Getting the cost data is clear from P-5.2 but the flight hours data (to take it to USD/per flight hour) is less clear. There seem to be several sources for flight hour data by a/c (from P-5.2 itself, T-100 etc. etc.) but none have let yielded any results that are comparable to the above.

    Does anyone have any suggestions?

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