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SAT in the comfort zone with Clean Sky's SPAIN

Europe's Small Air Transport (SAT) category could be getting an upgrade in terms of thermo-acoustic comfort as Clean Sky's SPAIN project nears completion this June. By integrating thermal and acoustic insulation into the cabin sidewall panels, passengers will enjoy a quieter inflight experience; General Aviation's planemakers will benefit from simplified design, construction and assembly of cabin linings; and aircraft operators will gain from affordable and easier maintenance using eco-friendly insulation materials which reduce environmental impact.

The finely tuned economics of aviation in the SAT category leaves limited opportunities for improving inflight comforts, but Clean Sky's SPAIN (Smart Panels for SAT Aircraft Cabin Insulation) project is intent on redressing the balance in favour of the European traveller.

The project is taking a fresh look at insulation, both in terms of keeping passengers shielded from the cold outside temperatures and especially in respect of blocking out the juddering roar inherent in non-pressurized propeller-driven aircraft. After all, if the aspiration is to get anywhere door to door within Europe within four hours, why can't the journey also be free of noise and vibration?

"The SPAIN Project aims to be innovative in terms of insulation blanket construction methods for coupling the best thermal and acoustics characteristics and in cabin insulation system design methodologies suited for the SAT community" says Jaime Perez de Diego, Clean Sky Project Officer. "The challenge is to research, design, develop and implement a cabin insulation system that is cost-conscious to acquire, reduces cabin noise, improves accessibility and lowers maintenance costs linked to the insulation system removal. Weight saving is also a target, to drive down operating costs. But the key innovative breakthrough is the coupling of the thermal and the acoustic insulation materials in an integrated way with the cabin interior sidewall panels to simultaneously achieve all these targets".

Clean Sky Project Officer Michel Goulain points out that "on small aircraft, the proximity of the propeller to the passengers is very close, and these propellers create a whistling noise which is tiring for travellers. Part of the plan is to assess the possibility of incorporating some Helmholtz resonators into the thermo-acoustic insulation because these are efficient for noise suppression".

Why has the industry taken so long to address this important challenge for SAT aviation? The answer is partly an issue of scale and economics, according to one of the project partners: 

"The problem today is that the supply chain for aircraft OEM companies that produce thermo-acoustic materials is more oriented towards the big airframers, but there is a need for smaller aircraft constructors to have better thermo-acoustic insulation to provide cabin comfort. However, there isn't a supply chain in place to provide SAT planemakers with suitable systems at a cost effective level. This is the big challenge of Clean Sky's SPAIN project" says Giuliano Di Paola, Chief Technical Officer at Napoli-based Protom Group S.p.A which is coordinating the project.

"This cabin acoustic insulation system we are working on will have better performance than the state-of-the-art for this kind of category of aircraft, and should be more affordable" adds Di Paola.

The SPAIN consortium, which also comprises Tecnologie Industriali & Aeronautiche SpA (TI&A), has been working on the innovative approach to cabin thermal and acoustic insulation improvement for small commuter type aircraft by integrating new insulation materials with the cabin interior linings – an initiative that will culminate with the design, development and production of a complete cabin insulation system for the EV-55 new-generation twin turboprop aircraft manufactured by Czech Republic-based Evektor, the topic manager for the project.

Quantifiable goals for SPAIN include reducing cabin noise to lower than 80 dBA (in contrast to 90 dBA, the norm for general aviation). Additionally, the aim is that by combining insulation and lining elements it will be possible to improve accessibility for maintenance purposes, thereby reducing by 20% the costs associated with the insulation system removal during overhauls or inspections. 

Environmental and sustainability considerations are integral to the project, and for the development of this insulation system, the consortium is committed to using materials based on natural organic fibres (or fibres derived from recycling processes) as an alternative to the conventional synthetic thermal insulation substances. 

The consortium reports that following an initial screening of the optimal materials available on the market, with characteristics of thermal and acoustic insulation, they have performed a sizing of the preliminary configuration most suitable of material compounds with the goal of matching the requested thermal and acoustic performance, with ongoing thermal characterization testing and acoustic testing on various configurations of the materials. The SPAIN consortium is also working on the Verification & Validation approach, aiming at developing a robust design methodology for a thermo-acoustic insulation system suited for small aircraft community. Currently, design of the complete EV-55 aircraft cabin insulation system is in progress with the selected insulation material compounds.

"We have a demonstration planned this March on one section of the cabin" says Di Paola. "We will be testing – in an acoustic chamber – a cabin interior sidewall panel equipped with this blanket that is made of different materials that dampen the acoustic noise and which also provides the right thermal insulation. Then we will run some analysis to show that we have a reduction of the acoustic noise compared to similar aircraft because this is the main point of the project. These types of aircraft are not so comfortable in terms of thermal and acoustic performance, and our objective is to improve comfort in the general aviation aircraft. And at the end of the project, we plan to equip the entire cabin of the EV-55 aircraft with this kind of insulation system".