The delivery last month of the first 787-8 Dreamliner, claimed by Boeing to be 20 percent more fuel efficient than similar-sized current planes, highlights the importance of lightweight composite materials in the aviation industry.
Air New Zealand’s wholly-owned subsidiary Altitude Aerospace Interiors is in the thick of shedding weight in airline interiors, is launch customer for the longer 787-9 version with an order of eight aircraft.
Aviation has always been a big driver of composites use, and the airline industry has always used composites. That’s because aircraft are relatively high-performance vehicles that can’t afford to have weight where it’s not necessary.
Air New Zealand, the country’s flag carrier, has quite a large composites capability largely focused on the repair and maintenance of aircraft. For new interior fits and refits, its wholly-owned subsidiary Altitude Aerospace Interiors is in the forefront.
Altitude is a supplier of customized aircraft interiors for both commercial jet transport aircraft and VIP aircraft.
Baden Smith, head of commercial – airlines at Altitude said the company has the engineering design and certification teams necessary to produce the interiors, and it manages the entire supply chain.
“We design for a particular aircraft for retrofitting, or install new equipment in a new aircraft. What we do is try to increase an aircraft’s performance, using materials with a high specific strength and specific stiffness and reduce its weight. So virtually all the interiors that we build will be of composite,” Baden said.
Weight is one of the biggest constraints in an aircraft interior because ultimately it has to get it up in the air and operate in the most cost-efficient manner.
Costing will be different for each aircraft but Baden said US$400/year/kg of weight is a ballpark figure.
“So if you’re talking about a lifespan of 15 years, that’s a lot of money.
“A 747 is a couple of hundred tonnes. Any weight you can get out of that interior is a huge benefit to the airline for two reasons – the opportunity to save money via fuel which is good for the environment as well, or earn revenue by potentially loading another passenger or carry some more cargo.”
Altitude does all its interior design in New Zealand.
For a commercial transport aircraft, it manufactures the composite products mostly in Tulsa, Oklahoma in the US.
“There’s a bunch of reasons for that,” Baden said. “It’s just a lot easier because the aircraft has to be US FAA-certified. To have it done in the US is a lot easier.
“In New Zealand, the CAA refers to the same design standards as the US FAA Part 25 which defines the standards for the design of new and modified aircraft. There’s differences in the interpretation of those rules and the way you show compliance against those rules but it’s always the same rule.”
Interior installation is largely done at the Boeing, Airbus or the manufacturer’s facility.
It’s different for a VIP transport aircraft. It comes out of Boeing or Airbus or wherever it is empty with no interior at all. It will be flown down to either Auckland or Christchurch where a complete interior is fitted by Altitude.
“But we still manage the entire design. We might do some of the manufacturing in New Zealand and overseas but all the installation of that interior is done here,” Baden said.
When manufacturing is done in New Zealand, it is often at the engineering facilities of Air New Zealand. Occasionally, Altitude subcontracts some parts to other manufacturers.
Altitude has virtually never used anything but composites for primary structural components.
“We might use metallic materials from time to time like aluminium but largely they’re just for fittings, attachments and things that you need to machine or makes more sense to machine because of the way it’s going to be attached to the aircraft or something else is going to be attached to it,” Baden said.
Interior composite structures are sandwich-constructed to maximise local bending stiffness. The external skins are made of fibreglass reinforced composite and a phenolic honeycomb makes the core. In some specific circumstances the core may be replaced with aluminium honeycomb. In some very unusual situations carbon fibre skins with a honeycomb core is used.
The combination of phenolic honeycomb and fibreglass or carbon fibre meet flammability requirements.
“The fibre materials and the resin systems that we use tend to be very limited because of the flammability criteria,” Baden said.
“We’d use carbon fibre when we’re really at the limits of the strength that the material needs to carry. We try not to use it because fibreglass tends to suit us in most situations as it’s a relatively cost-effective material. Fibreglass is strong and stiff but also quite tough. With carbon fibre, you start to have to worry about things like galvanic cell corrosion if you’re using it close to any metallic material,” Baden said.
Carbon fibre will not corrode but it may create a situation which encourages corrosion in metallic materials, and of course, in an aircraft metallic materials are everywhere. With fibreglass that doesn’t happen.
While Kevlar may be used in different parts of the exterior of the aircraft, Altitude hardly ever uses it in interior components.
“Kevlar is a hygroscopic material. You don’t want to use it on the interior of the aircraft. You don’t want absorption of water into the material because it adds weight. It also creates health and safety issues.
As a provider of a very niche product for the international market, Baden said the future of composites is “very rosy”.
“The activity that we’re doing at the moment and the types of work that we’re doing with composites have a very strong application internationally and we expect that to continue.
“Right now, we’re working on programmes where one airline has a fleet of five aircraft, another has a fleet of seven, and another has 20 aircraft, and again another has 62.
“For us it’s not necessarily a volume game, it’s about how many different programmes we can be on because that’s where we really add value as a design and engineering company.”
Altitude has a mixture of 65 designers and engineers.
“Like any good designer or engineer you have to consider a good range of factors. Certainly you have to make sure that your design complies with the rules and meets certain regulatory standards like crash load considerations. They have to account for forward load under emergency landing considerations. There are certain flight loads that need to be considered both up, down and side loads that need to be considered if you’re experiencing turbulence for example.
“A flammability criterion needs to be considered, making sure that you’re not using a build up of material that is ultimately going to produce a product that doesn’t pass the flammability test.
“Abuse loads, passengers and flight crew/attendants walking through the aircraft, leaning or swinging on doors. In some situations it could be having to allow for a thousand pounds of load on a door because that’s the sort of abuse load criteria that you’re likely to see.
“Those are just quantitative criteria. Then there are the qualitative criteria as well like having to consider manufacturing methods and constraints and aesthetics.”
One of the biggest areas of value in the aircraft interiors market is the use of monocoque construction.
It does not have a whole lot of joints and no separate pieces of composite joined together with aluminium extrusions. It’s a single piece structure with load bearing capability.
“That’s where we’re a little bit different compared to some of our competitors internationally. They will build up a lot of their interiors from flat panel composites and then join them together with aluminium edge extrusions, just bolt them together.
“What we try to do, if the situation allows, is to try to have single piece construction.
“There’s a whole bunch of Boeing 777s flying around with all of the closets in the business class section designed by us. I know that sounds simple, just closets, but if you build a closet in a standard way, it will weigh a certain amount. The way that we design and have them built gives us anywhere between 20 and 30 percent reduction in weight.
“That’s the sort of thing that you could do with composites that you couldn’t do with metallic materials.”
For more information:
Altitude Aerospace Interiors
Tel: 09 2558909
Email: 021 713209