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Is it fair to say that narrowbody aircraft have a longer life than widebody aircraft? This is the conclusion drawn from a report written by Dick Forsburg from Avolon (.pdf), where he says that the average life of a narrowbody is 26.6 years, while the average life of a widebody is 24.6.

Is it generally accepted that narrowbodies have a longer life than widebodies? If so, what are the reasons for narrowbodies having a longer life that widebodies?

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    $\begingroup$ A few dozen DC3s are probably skewing the statistics. $\endgroup$ – Brian Drummond May 9 '18 at 20:19
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    $\begingroup$ What happens when you design a structure with a very new technology, using slide rules, with a relatively crude understanding of fatigue, so you add oodles of margin, and end up with an airplane with a near infinite fatigue life. As a product that, still to this day, businesses still purchase to put to work and make money over 85 YEARS after it was designed, the 3 is the greatest engineered conveyance of the 20th century in my book. $\endgroup$ – John K May 9 '18 at 21:55
  • $\begingroup$ This question is ambiguous. The reference discusses economic life and has the data you quote, rendering any other answer moot. You do not specify economic life, which makes me wonder whether you actually mean design life (how long the aircraft is intended to last) or maybe cycle life (which type is built more durably) $\endgroup$ – Pilothead May 13 '18 at 4:38
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The author does a very good job explaining the jet market. The key take-away is that it's all about economics. In many ways, narrowbodies may "wear out" faster as they typically fly shorter routes and accumulate more cycles in a shorter period of time. Pressurization cycles are a big factor in structural fatigue.

But that's not the primary reason for retirements. Airplanes get retired when operating them is no longer profitable. Profit is generically income minus costs. Income for aircraft is maximized by flying as much as possible (high utilization) with the highest load factors possible. Costs are primarily driven by capital depreciation, fuel, crew, and maintenance.

The shorter lifespan he identified for widebodies is driven by a few key factors:

  1. Widebodies are a smaller percentage of the total fleet, so that even a few "early" retirements will cause a larger shift in the average.
  2. Widebodies are suited primarily for long-haul, high density routes. So a shift in travel patterns can quickly leave a route unprofitable. Covering that reduced demand will often mean shifting to a smaller aircraft to keep the load factors up. Narrowbodies have more inherent flexibility.
  3. And what I would say is one of the most significant factors is the shift of widebodies from 4 engines to 2 engines over the last 20-25 years. It's not a fast process as widebody construction is not very high rate, but the cost benefit of 2 engine widebodies (B777, A330, A350) means a lot of 4 engine aircraft (B747, A340) have been retired in the last 10-15 years.
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    $\begingroup$ I would guess that there's also probably less third-world secondary market willing to buy really old aircraft in the case of wide-bodies compared to narrow-bodies. $\endgroup$ – reirab May 9 '18 at 15:37
  • $\begingroup$ The article says that narrowbody aircraft have a longer lifespan than widebody (26.6 years vs 24.6 years). So pressurization cycles may not be a determining factor. $\endgroup$ – zundi May 10 '18 at 0:11
  • $\begingroup$ @zundi Edit answer to clarify that structural issues aren't a primary reason why airplanes get retired. $\endgroup$ – Gerry May 10 '18 at 12:00
  • $\begingroup$ Zundi is right - short-haul aircraft accumulate their cycles in much less time, so a longer lifetime means that many more cycles are accumulated. However, short-haul aircraft are also designed for more cycles (guess why!), so the overall conclusion is not valid. What is more significant is that very old aircraft will dominate the statistics - wide bodies are simply not long enough around! $\endgroup$ – Peter Kämpf May 10 '18 at 12:05
  • $\begingroup$ So how many cycles is a heavy designed for? 40 or 50k? $\endgroup$ – John K May 10 '18 at 15:51
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The author has a masters degree in marketing, so please do not expect an expert in statistics. Adding up some numbers without correcting for effects will lead to wrong conclusions. When almost all 707s and DC-8s are retired already but one quarter of all DC-10s and half of all A300s are still in service, it is simply too early to give an "average" retirement age for wide bodies.

It would be better to only compare aircraft from a specific time period, like the 1980s, but to simply add all up will produce misleading results since wide bodies are not around long enough and have been introduced with high-bypass fan engines already, so they can still be operated profitably, if only as freighters.

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The cycle length is the biggest factor I think. Airframes are generally designed to be economical to operate to 80000 cycles, but often the airframes start to require patching and reinforcement of the structure at around 40-50000 cycles to avoid increasingly onerous inspection requirements. Airframes get retired when the cost of incorporating the structural reinforcements exceeds the benefit. Regional Jet aircraft that do a cycle every 1.2 hours suffer the most from this and many get retired after only 20 years of service because it's not worth patching them up. In general, the longer the average cycle time, the more years that can be squeezed out of an airframe.

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    $\begingroup$ If I'm not mistaken, you are actually explaining the opposite: why smaller aircraft should be retired earlier, when the OP is asking why larger ones are. $\endgroup$ – jcaron May 9 '18 at 16:50
  • $\begingroup$ Good point lol. My expertise is in the regional world. People would complain about how RJs were being retired so early from an hours standpoint and I would point out that a 767 with 40000 hours has less than half the cycles of a regional jet. $\endgroup$ – John K May 9 '18 at 21:50
  • $\begingroup$ The article says that narrowbody aircraft have a longer lifespan than widebody (26.6 years vs 24.6 years). $\endgroup$ – zundi May 10 '18 at 0:14
  • $\begingroup$ Your cycle count is only correct for short-haul aircraft. Long range design cycles are maybe half as many. $\endgroup$ – Peter Kämpf May 10 '18 at 12:07
  • $\begingroup$ Well yes of course an airplane averaging 4 hour legs will have not much more than a quarter of the cycles of an RJ for the same flight hours. $\endgroup$ – John K May 10 '18 at 15:47
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As stated in the comment above, if you mean economic life the reference you quote already proves the answer in the current environment.

The reason narrowbodies are currently kept in service longer than widebodies is due to the extraordinary demand for narrowbodies due to extreme growth of LCCs and competitors following a period of world wide deregulation. If you can't get a new aircraft you keep using the old one, even if it is not as efficient as some newer unavailable model. This environment may change at some point, and the answer will change with it.

If you mean design life, commercial aircraft are typically designed to last 30 years though this has been lower in the past. A narrowbody's life is much tougher than a widebody's so they are built tougher; they have a higher cycle capacity built into them.

A typical widebody would wear out rapidly if exposed to typical narrowbody usage. If you look at the 747D made for JAL/ANA to use on domestic routes, it not only was packed with a larger than normal number of seats, increased gross wt and reduced fuel capacity, it was also reinforced to endure the additional wear. Its design cycle life was 52,000 compared to a standard 747 at 24,000. It also had derated engines to lengthen their useful life.

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