These two aircraft pushed the limits in airframe and engine technology, the gains in efficiency and performance have been really impressive


But has the switch to substantially more composites in both types really been worth it ?



I read that most of the gains in efficiency on both types are mostly due to their new, far more efficient engines, the empty weight of both aircraft doesn’t appear to be far lighter than a conventional, all metal construction equivalent airframe



There are advantages to composite construction to be sure, corrosion is no longer an issue and it allows for a higher pressure differential, lower cabin altitude and more humidity improving passenger comfort


But Boeing is doing that anyway with the new 777-9 and it’s conventional, aluminum fuselage


The composite fuselage is apparently very strong with impressive hour and cycle limits but is that worth it too ?


If these airframes can endure a lot longer is that a real benefit ? In 20 years there will be new technologies enabling even greater efficiencies



I always thought the 787 was going to be the base model of a whole new mostly composite family of Boeing aircraft


I don’t see that at all now, I think the 737 / 757 and 767 replacements will all be of conventional aluminum construction


An eventual clean sheet replacement for the 777 thats modeled on the 787 seems doubtful, if that approach was promising why didn’t Boeing go ‘all the way’ with the 777-8–9 and incorporate a 787 like composite fuselage ?



I’m starting to think the whole composite experiment was and is just that, the massive investment by B and A doesn’t seem to have paid off as far as composites are concerned although AB seems to have executed it better I don’t think this is leading to a whole new family of similar types from either manufacturer

Max Q wrote:

if that approach was promising why didn’t Boeing go ‘all the way’ with the 777-8–9 and incorporate a 787 like composite fuselage ?

Because they then wouldn't be 777s, and thus would have to go through the far more extensive+expensive approval process for all-new aircraft.

Max Q wrote:

I’m starting to think the whole composite experiment was and is just that, the massive investment by B and A doesn’t seem to have paid off as far as composites are concerned

High on supposition, low on tangible data.

Without the real financial numbers, plus an accurate simulation to calculate the opportunity cost + likely performance of a conventional build of the same type/class..... none of which we here have or would be privy to, there's no way to *accurately* come to the conclusion you seek, one way or another.

Max Q wrote:

These two aircraft pushed the limits in airframe and engine technology, the gains in efficiency and performance have been really impressive


But has the switch to substantially more composites in both types really been worth it ?



I read that most of the gains in efficiency on both types are mostly due to their new, far more efficient engines, the empty weight of both aircraft doesn’t appear to be far lighter than a conventional, all metal construction equivalent airframe



There are advantages to composite construction to be sure, corrosion is no longer an issue and it allows for a higher pressure differential, lower cabin altitude and more humidity improving passenger comfort


But Boeing is doing that anyway with the new 777-9 and it’s conventional, aluminum fuselage


The composite fuselage is apparently very strong with impressive hour and cycle limits but is that worth it too ?


If these airframes can endure a lot longer is that a real benefit ? In 20 years there will be new technologies enabling even greater efficiencies



I always thought the 787 was going to be the base model of a whole new mostly composite family of Boeing aircraft


I don’t see that at all now, I think the 737 / 757 and 767 replacements will all be of conventional aluminum construction


An eventual clean sheet replacement for the 777 thats modeled on the 787 seems doubtful, if that approach was promising why didn’t Boeing go ‘all the way’ with the 777-8–9 and incorporate a 787 like composite fuselage ?



I’m starting to think the whole composite experiment was and is just that, the massive investment by B and A doesn’t seem to have paid off as far as composites are concerned although AB seems to have executed it better I don’t think this is leading to a whole new family of similar types from either manufacturer

The experiment is still ongoing.
We don't know how large CFRP structures will behave over time and NDT of large CFRP surfaces is very difficult such that accidents will eventually occur due to undetected fatigue.

Short answer. Composite construction enables the high aspect ratio wings (L/D) and aerodynamic shape which gives both 787 and 777-9 the range requested of the airline customers. A new composite fuselage has very high non-recurring costs from test, certification and tooling.

LAX772LR wrote:

Max Q wrote:

if that approach was promising why didn’t Boeing go ‘all the way’ with the 777-8–9 and incorporate a 787 like composite fuselage ?

Because they then wouldn't be 777s, and thus would have to go through the far more extensive+expensive approval process for all-new aircraft.

Max Q wrote:

I’m starting to think the whole composite experiment was and is just that, the massive investment by B and A doesn’t seem to have paid off as far as composites are concerned

High on supposition, low on tangible data.

Without the real financial numbers, plus an accurate simulation to calculate the opportunity cost + likely performance of a conventional build of the same type/class..... none of which we here have or would be privy to, there's no way to *accurately* come to the conclusion you seek, one way or another.

Might I also add. That very expensive development may very well not have paid off because the market for that size of aircraft exists but not big enough to justify a clean sheet

Opus99 wrote:

LAX772LR wrote:

Max Q wrote:

if that approach was promising why didn’t Boeing go ‘all the way’ with the 777-8–9 and incorporate a 787 like composite fuselage ?

Because they then wouldn't be 777s, and thus would have to go through the far more extensive+expensive approval process for all-new aircraft.

Max Q wrote:

I’m starting to think the whole composite experiment was and is just that, the massive investment by B and A doesn’t seem to have paid off as far as composites are concerned

High on supposition, low on tangible data.

Without the real financial numbers, plus an accurate simulation to calculate the opportunity cost + likely performance of a conventional build of the same type/class..... none of which we here have or would be privy to, there's no way to *accurately* come to the conclusion you seek, one way or another.

Might I also add. That very expensive development may very well not have paid off because the market for that size of aircraft exists but not big enough to justify a clean sheet

Well, exactly !


Goes to my point

I can see this both ways

From one aspect, aircraft will have to evolve due to increased demand in reducing the emissions/carbon footprint and increased efficiency, and this will require a lot of necessary research/development/change since currently no current design can really handle the requirements.

The other aspect is have we reached a peak in aircraft design/functionality? I use for example the basic Diesel-electric locomotive used primarily in the US. They have evolved a bit but the basic running gear/design is overall the same basic design/concept from the 1950's from Electro-Motive

Max Q wrote:

These two aircraft pushed the limits in airframe and engine technology, the gains in efficiency and performance have been really impressive


But has the switch to substantially more composites in both types really been worth it ?



I read that most of the gains in efficiency on both types are mostly due to their new, far more efficient engines, the empty weight of both aircraft doesn’t appear to be far lighter than a conventional, all metal construction equivalent airframe



There are advantages to composite construction to be sure, corrosion is no longer an issue and it allows for a higher pressure differential, lower cabin altitude and more humidity improving passenger comfort


But Boeing is doing that anyway with the new 777-9 and it’s conventional, aluminum fuselage


The composite fuselage is apparently very strong with impressive hour and cycle limits but is that worth it too ?


If these airframes can endure a lot longer is that a real benefit ? In 20 years there will be new technologies enabling even greater efficiencies



I always thought the 787 was going to be the base model of a whole new mostly composite family of Boeing aircraft


I don’t see that at all now, I think the 737 / 757 and 767 replacements will all be of conventional aluminum construction


An eventual clean sheet replacement for the 777 thats modeled on the 787 seems doubtful, if that approach was promising why didn’t Boeing go ‘all the way’ with the 777-8–9 and incorporate a 787 like composite fuselage ?



I’m starting to think the whole composite experiment was and is just that, the massive investment by B and A doesn’t seem to have paid off as far as composites are concerned although AB seems to have executed it better I don’t think this is leading to a whole new family of similar types from either manufacturer

I personally don’t work in composites as a profession (so someone who does feel free to correct me) but I have been involved with several projects including it and have several friends who do it for a living/masters thesis. Composites can save an extraordinary amount of weight and still be exceptionally stiff and strong. But there are a couple of key disadvantages when comparing it to metals. The most significant of which is that composite materials are generally not isotropic, meaning they are not the same strength when loaded in different directions. They are also, from my understanding, much more sensitive to cracks and damage than metals. Extremely sensitive to manufacturing processes. With that in mind, I’m really not surprised that the safety margins for the first generation of something as structurally complex as a fuselage are probably higher than they need to be. Unless there is some breakthrough in aluminum or steel alloys, or even some other metal, composites are definitely the present and future.

AndoAv8R wrote:

I can see this both ways

From one aspect, aircraft will have to evolve due to increased demand in reducing the emissions/carbon footprint and increased efficiency, and this will require a lot of necessary research/development/change since currently no current design can really handle the requirements.

The other aspect is have we reached a peak in aircraft design/functionality? I use for example the basic Diesel-electric locomotive used primarily in the US. They have evolved a bit but the basic running gear/design is overall the same basic design/concept from the 1950's from Electro-Motive

There is a limit to aircraft design, and we are inching ever closer to it. Every 1% increase in fuel efficiency in a modern airliner costs far more than a 1% increase did even just two decades ago. Airline manufacturers (and their cast of supply chain partners including engine manufacturers) are pushing the limits of material design to eke out additional performance.

However, there is a huge incentive difference between airlines and locomotives (which have also gotten more efficient over time). Today, it takes 5 gallons of fuel to move 1 ton of freight across the country on a train. On a plane, it's 60 gallons (and it gets worse if you're doing long-haul). Fuel costs are practically trivial to a railroad - the cost of maintaining the railroads themselves, the cargo loading/off loading, and so on - is the major cost driver for a railroad. A 20% increase in fuel efficiency doesn't really change their business model or drive a competitive differentiation.

For an airline, fuel costs are massive. So airlines will indirectly pay for the billions of R&D required to get better fuel efficiency.

All that said - on the topics of carbon fiber - it's not going away. It costs a lot to design a new CFRP plane which is why the 777 isn't doing it - it would be a redesign. Composites have been a major component of all new airplane designs in the past 30 years with ever increasing scope/utilization - with more use in long-range widebodies because that is where the biggest return is in terms of fuel consumption. CFRP is getting cheaper over time as well - economies of scale and use in other sectors like automotive are pushing down the cost of CFRP pretty significantly (although the manufacturing techniques in airlines are more expensive - but they still benefit).

At a minimum, it will be used in the wings of pretty much all new designs. It may or may not be used in fuselages depending on mission purpose. The shorter the haul, the less benefit of weight reduction (although on the flip side if it has effectively unlimited cycles in practice then that has its own benefits for short haul use).

Max Q wrote:

I read that most of the gains in efficiency on both types are mostly due to their new, far more efficient engines, the empty weight of both aircraft doesn’t appear to be far lighter than a conventional, all metal construction equivalent airframe

You're right on this. This is why Airbus and Boeing are always going on about the engines - the vast majority of the efficiency comes from the powerplant. This is why the step change is always engines... neos and so on, with just tweaks to the airframe. The real people who should be credited are the engineers and designers at Rolls-Royce, Pratt & Whitney and General Electric. They're the ones responsible for most of the efficiency, though the airframe manufacturers are the ones who are always crowing about how good their product is as though they built the engines too.

I visited Boeing and have held a piece of standard aircraft structure and a piece of composite, the same size, and the composite is lighter, yes, but it's not THAT much lighter. It wasn't a WOW how light is THIS moment, it was more, "oh yes, it's lighter, I see".

Max Q wrote:

Opus99 wrote:

LAX772LR wrote:

Because they then wouldn't be 777s, and thus would have to go through the far more extensive+expensive approval process for all-new aircraft.



High on supposition, low on tangible data.

Without the real financial numbers, plus an accurate simulation to calculate the opportunity cost + likely performance of a conventional build of the same type/class..... none of which we here have or would be privy to, there's no way to *accurately* come to the conclusion you seek, one way or another.

Might I also add. That very expensive development may very well not have paid off because the market for that size of aircraft exists but not big enough to justify a clean sheet

Well, exactly !


Goes to my point

No, it doesn't go to your point. You haven't made a financial analysis grounded by data. You've offered nothing but supposition.

It's pretty clear CFRP is the material of choice for wings. CFRP offers strength and smoothness and precise moulding you can't get from metal. The shape is ever changing, so the mass production advantages of metal are less important.

It's still not clear what the winner is for fuselages. CFRP is costly. It's actually "too strong" for fuselages in that it needs to be thicker than necessary to deal with ramp rash and other collision risks. Since fuse cross sections are (mostly) uniform, their shaping advantages are minimized. They may save labor in that stringers can be co-cured, but then again the robots that lay out carbon fiber aren't cheap either.

One data point is the last commercial airliner clean sheet, A220, has CFRP wings and metal fuse. Actually it also uses CFRP for the empennage and rear section where the cross section tapers, again a positive aspect of CFRP is its relative ease of shaping while retaining strength and low weight. Other than that A220 has a traditional cross section.

CFRP also may find favor for some of the "ovoid" cross sections we see discussed. They may not be the optimal thing to do from the point of physics, but may find favor because they enable an overall smoother airline operation.

Overall, it seems hard to expect a fuselage of a traditional cross section narrow body airliner to be CFRP, unless the cost of making CFRP has dropped significantly in the last decade. It seems metal is easier to mass produce for constant cross sections. It is somewhat labor intensive but in at least some cases robots can be used to reduce the labor cost.

The engine tech really is the driver of efficiency, although the composite airframe confers a material OEW advantage at a similar configuration, anywhere from high-single-digits to as much as 20% with the longest barrels. The problem is, it is costlier to develop and produce.

787 and A350 may be last of a breed since they may be the last generation of commercial airliners with no provision for single pilot operation, but we've had that discussion already.

And I think the discussion of "what is the actual requirement for aircraft lifecycle going forward" is an interesting one. This crisis is showing it's not as hard to write off aircraft after their first lease (10-12 years) than maybe was being presumed earlier. The price to update aircraft seems to be very expensive, as is heavy maintenance. The life cycle of the aircraft's avionics seems to be more in control of the fate of the aircraft than the old days. Does it really make sense to build an aircraft for more than 20-24 years of use?

ClassicLover wrote:

You're right on this. This is why Airbus and Boeing are always going on about the engines - the vast majority of the efficiency comes from the powerplant. This is why the step change is always engines... neos and so on, with just tweaks to the airframe. The real people who should be credited are the engineers and designers at Rolls-Royce, Pratt & Whitney and General Electric. They're the ones responsible for most of the efficiency, though the airframe manufacturers are the ones who are always crowing about how good their product is as though they built the engines too.

Yet they too are hitting the law of diminishing returns. RR's problems with thermal coatings and PW's problem with high speed seals and bearings show this to be true. Pratt spent decades perfecting the gearing, but in the end their engine is just slightly better than LEAP which is a more traditional architecture.

I personally don’t work in composites as a profession (so someone who does feel free to correct me) but I have been involved with several projects including it and have several friends who do it for a living/masters thesis. Composites can save an extraordinary amount of weight and still be exceptionally stiff and strong. But there are a couple of key disadvantages when comparing it to metals. The most significant of which is that composite materials are generally not isotropic, meaning they are not the same strength when loaded in different directions. They are also, from my understanding, much more sensitive to cracks and damage than metals. Extremely sensitive to manufacturing processes. With that in mind, I’m really not surprised that the safety margins for the first generation of something as structurally complex as a fuselage are probably higher than they need to be. Unless there is some breakthrough in aluminum or steel alloys, or even some other metal, composites are definitely the present and future.

One of my mentor's 35 years ago when I started my career said that we shouldn't be overly concerned about fatigue in composite structure because there are 10,000 fibers acting as crack stoppers. It is difficult to actually create a fatigue crack in composite structure when there are in-plane loads exclusively. In a balanced design, the metal details in the fittings and the fasteners in the joints are more critical than the composite structure.

It is true that one needs to be careful when there are design features which create out-of-plane loads, which might create disbonds and delamination. Typically this would be radius details in shear clips and spar chords.

Overall, it seems hard to expect a fuselage of a traditional cross section narrow body airliner to be CFRP, unless the cost of making CFRP has dropped significantly in the last decade. It seems metal is easier to mass produce for constant cross sections. It is somewhat labor intensive but in at least some cases robots can be used to reduce the labor cost.

What you are neglecting to consider is that highly integrated structure, e.g. co-cured stringers on a fuselage barrel section and integrated fuselage frames, saves a lot of cost in part count reduction, assembly touch time, and inventory cost. Those who don't work in the industry really have no concept of how much it costs to engineer, contract, qualify, and inspect/receive each individual part.
The economies of scale have also dropped CFRP raw-material costs down dramatically over the past thirty years for toughened matrix intermediate modulus pre-pregs used on the 777, 787 and 777X airplanes.

CaptainHaresh wrote:

Max Q wrote:

These two aircraft pushed the limits in airframe and engine technology, the gains in efficiency and performance have been really impressive


But has the switch to substantially more composites in both types really been worth it ?



I read that most of the gains in efficiency on both types are mostly due to their new, far more efficient engines, the empty weight of both aircraft doesn’t appear to be far lighter than a conventional, all metal construction equivalent airframe



There are advantages to composite construction to be sure, corrosion is no longer an issue and it allows for a higher pressure differential, lower cabin altitude and more humidity improving passenger comfort


But Boeing is doing that anyway with the new 777-9 and it’s conventional, aluminum fuselage


The composite fuselage is apparently very strong with impressive hour and cycle limits but is that worth it too ?


If these airframes can endure a lot longer is that a real benefit ? In 20 years there will be new technologies enabling even greater efficiencies



I always thought the 787 was going to be the base model of a whole new mostly composite family of Boeing aircraft


I don’t see that at all now, I think the 737 / 757 and 767 replacements will all be of conventional aluminum construction


An eventual clean sheet replacement for the 777 thats modeled on the 787 seems doubtful, if that approach was promising why didn’t Boeing go ‘all the way’ with the 777-8–9 and incorporate a 787 like composite fuselage ?



I’m starting to think the whole composite experiment was and is just that, the massive investment by B and A doesn’t seem to have paid off as far as composites are concerned although AB seems to have executed it better I don’t think this is leading to a whole new family of similar types from either manufacturer

The experiment is still ongoing.
We don't know how large CFRP structures will behave over time and NDT of large CFRP surfaces is very difficult such that accidents will eventually occur due to undetected fatigue.

Isn't CFRP inspection improving due to technology? Your statement only seems accurate in the case where time and techniques are at standstill.

Interesting replies, I guess my question remains though, does anyone think Boeing or Airbus will build a new aircraft model using the 787 or A350 as a template, or indeed a new airframe using mostly composite?

Max Q wrote:

Interesting replies, I guess my question remains though, does anyone think Boeing or Airbus will build a new aircraft model using the 787 or A350 as a template, or indeed a new airframe using mostly composite?

Airbus:
MY guess is that the next ( from new ) design will be a (narrow body?) with laminar flow wings.

fully composite plastic structure sporting 3d surfaces/forms are a prerequisite for that step.

cfrp panels for fuselage construction seem to work well too ( for Airbus )

other steps: additive manufacturing ( as in laser sintering of complex parts )
but also parametric manufacture of CFRP parts.
look into Airbus cfrp frames: They seem to be wound as hollow profile hoops that are separated
into two frames after curing. How much fiber is wound onto the mold is position dependent.
The way frames and fuselage skin are connected via clips allows for material thickness variation.

I can see composite structure being used for wings on future types but not all composite fuselage construction, I don’t think the payoff is there

Neither Boeing nor Airbus have developed a brand new aircraft since the 787 and A350, and as other posters have said it would be far more complicated to change the fuselage design on existing aircraft variants

CaptainHaresh wrote:

We don't know how large CFRP structures will behave over time and NDT of large CFRP surfaces is very difficult such that accidents will eventually occur due to undetected fatigue.

The all-composite B-2 has been in service since 1997, the Premier I since 2001, the A300 has had an all-composite fin since 1985. What exactly do you think we still need to learn?

ELBOB wrote:

CaptainHaresh wrote:

We don't know how large CFRP structures will behave over time and NDT of large CFRP surfaces is very difficult such that accidents will eventually occur due to undetected fatigue.

The all-composite B-2 has been in service since 1997, the Premier I since 2001, the A300 has had an all-composite fin since 1985. What exactly do you think we still need to learn?

Dornier also used CFRP in structural parts on their Alpha Jet in the mid-1970s, and introduced a CFRP wing for the type in the mid-1980s.

LAX772LR wrote:

Max Q wrote:

if that approach was promising why didn’t Boeing go ‘all the way’ with the 777-8–9 and incorporate a 787 like composite fuselage ?

Because they then wouldn't be 777s, and thus would have to go through the far more extensive+expensive approval process for all-new aircraft.

Max Q wrote:

I’m starting to think the whole composite experiment was and is just that, the massive investment by B and A doesn’t seem to have paid off as far as composites are concerned

High on supposition, low on tangible data.

Without the real financial numbers, plus an accurate simulation to calculate the opportunity cost + likely performance of a conventional build of the same type/class..... none of which we here have or would be privy to, there's no way to *accurately* come to the conclusion you seek, one way or another.

It is with noting though that the A220 and the MC21 are post 787/A350, they are both considered state of the art and both went for aluminium/alloy fuselage.

rigo wrote:

LAX772LR wrote:

Max Q wrote:

if that approach was promising why didn’t Boeing go ‘all the way’ with the 777-8–9 and incorporate a 787 like composite fuselage ?

Because they then wouldn't be 777s, and thus would have to go through the far more extensive+expensive approval process for all-new aircraft.

Max Q wrote:

I’m starting to think the whole composite experiment was and is just that, the massive investment by B and A doesn’t seem to have paid off as far as composites are concerned

High on supposition, low on tangible data.

Without the real financial numbers, plus an accurate simulation to calculate the opportunity cost + likely performance of a conventional build of the same type/class..... none of which we here have or would be privy to, there's no way to *accurately* come to the conclusion you seek, one way or another.

It is with noting though that the A220 and the MC21 are post 787/A350, they are both considered state of the art and both went for aluminium/alloy fuselage.

I think that’s telling and probably where the industry as a whole is going