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Going with the flow

New materials and careful system management promise a reduction in air conditioning noise throughout the cabin, as well as lighter weight and reduced maintenance, as Paul E. Eden explains

Air conditioning, like much in the cabin, adds weight and complexity, as well as requiring a certain level of maintenance – none of which is ideal for an airline when time and money are tight. Apart from the complex maintenance issues, air conditioning is also responsible for a major part of the ambient cabin noise, often being blamed for poor passenger experiences and uncomfortably low humidity. In response, manufacturers are employing new technologies, clever operating techniques and the latest materials to solve these problems.


Among the market leaders in air distribution systems, the Diehl Aerosystems Aircabin range offers components and full air conditioning systems, not only for passenger cabins, but also crew rest areas, flight decks, cargo compartments and avionics bays. Using carbon fibre reinforced plastics (CFRPs) and fibreglass, the company delivers maintenance-free components, claiming that it is only the filter elements in its systems that will ever require attention.


A Diehl spokesperson explained more about its products and production processes: “Both CFRPs and fibreglass are used in Diehl components, sometimes in combination with honeycomb and with insulating materials applied.” In terms of component or system design, he says, “Depending on the history of the aircraft type that we’re providing components for, we either build-to-print (based on the original equipment manufacturer’s design), build-to-specification, or work with other equipment manufacturers as partners.”


Matzen & Timm, located in Norderstedt, near Hamburg airport, produces a variety of air conditioning system parts and customised items. Dirk Baumann, the firm’s managing director, explains; “We specialise in complex connection and hose systems using high-tech caoutchouc [natural rubber] materials – such as silicone. We also use high-temperature hoses, suction hoses and coolant hoses for air conditioning, vacuum toilets and bleed air systems.”


The manufacturer includes lightweight bellows for cabin air distribution in its product line up, with Baumann noting that reducing the weight of its products is an important consideration for the future.



Benny Younesi is president of Aerocon Engineering, based in Van Nuys, California. The company offers bespoke solutions to a wide range of operator requirements, among them VIP and VVIP interior completions and air conditioning optimisation. Although Aerocon does not list airlines among its regular clients, it regularly modifies commercial airframes to customer specifications – including the Fokker 100 and both Boeing narrow and wide bodies – and Younesi has much to say on cabin air conditioning.


His VIP clients demand quiet cabins and air conditioning output matched to living space, where interiors are divided into work areas, lounges and bedrooms, for example. Aerocon satisfies these requirements through careful optimisation of existing technologies and by installing its own systems. “We recently had a customer with an equipment fit producing a huge heat load,” he says. “It forced us to really push the envelope; we went to our component suppliers expecting them to meet the requirements – that’s when the technical challenge becomes very difficult.”


In terms of noise reduction, Younesi explains that Aerocon has a system suitable for a range of platforms up to the Boeing 747-8 and that it will soon begin work on one for the Boeing 787. “We find the air conditioning or environmental control system [ECS] particularly challenging. Almost 50% of cabin noise is derived from the cabin air distribution system and poorly designed equipment can counter our noise reduction system. We work with the completion centres or our customers, helping them understand the ECS and air distribution system so that airflow, velocity and pressure at the outlets and air returns are managed carefully.


“We’re careful not to degrade the thermal aspect of the cabin, but we make sure that there’s no excess airflow at high velocity. With a well-balanced airflow, noise and cooling can be balanced simultaneously. We optimise existing systems by modification, ensuring that air distribution is balanced throughout the cabin.”


Diehl’s work includes the design and production of air-mixing chambers, air ducting and air outlets, right up to complete air distribution packages. It prides itself on the low weight of its systems, but also on their minimal noise output. The company’s spokesperson agrees with Aerocon’s philosophy of reducing noise primarily through airflow optimisation, but also notes that special manufacturing methods and muffling technology are applied to components. >>

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