Evolutions of airworthiness standards for new aircraft structure designs using materials, processes, and advanced manufacturing methods


The European Commission published the amended Horizon Europe Work Programme 2023-24 on 31 March 2023. The overall driver of Cluster 5 – “Climate, Energy and Mobility” is to accelerate the green and digital transition, and the associated transformation of the economy, industry and society to achieve climate neutrality in Europe by 2050. 

This cluster contains seven research actions, which have been delegated to EASA as contracting authority. This project addresses the following action: Evolutions of airworthiness standards for new aircraft structure designs using materials, processes, and advanced manufacturing methods.

Outcome and output

The outcome below describes the expected and targeted benefit and impact the project will generate after successfully completion. The output below describes the intended project results needed to achieve the expected/targeted outcome. 

Expected outcome

The required output is industry supported content relating to the identified Tasks allowing development of further regulator and industry guidelines (as is increasingly necessary with regard developing regulator ‘Performance Based Regulation’ (PBR) philosophies) for the safe design, manufacture, and in-service use of bonded and sandwich structures in increasingly critical applications.  Regulatory and guidelines documents likely to benefit from this work include:

  1. EASA CM-S-005 issue 1 ‘Bonded Repair Size Limits in accordance with CS-23, CS-25, CS-27, CS-29 and AMC 20-29’;
  2. EASA CM-S-010 issue 1 ‘Composite Materials - The Safe Design and Use of Monocoque Sandwich Structures in Principal Structural Element Applications’;
  3. EASA AMC 20-29 ‘Composite Aircraft Structures’ (2010);
  4. SAE Composite Materials Handbook – 17 (CMH-17) – Disbond and Delamination Task Group;
  5. Other regulatory continued airworthiness documents (existing and/or new) which may benefit from this project.
Required output

Current technology summary:
A ‘benchmark’ summary of current and developing aviation industry (and regulator) practice to be provided regarding the use of sandwich structures, particularly in applications with safety implications. This is to include a summary of regulator and industry guidance development activities, and directly relevant supporting R&D, e.g., as has been developed in CMH-17, supported by R&D, e.g., EASA_REP_RESEA_2016. Furthermore, a summary of potential new applications is to be provided, including identification of potential applications in new product types, such as, Innovative Air Mobility (IAM). The summary is to also identify perceived limitations/roadblocks to such applications etc. 

Progress substantiated design solution:
Development of substantiated design solutions supporting the safe design of sandwich structures for applications and configurations of practical aviation industry relevance beyond those recently developed, e.g., CMH-17. Such work is likely to extend such methods (e.g., to include curvature, combined in-plane/shear loading) and include additional validation work for a broader range of materials/configurations (including metal face sheets), as may be of interest to rotorcraft and IAM designs. Once complete, this is to also be documented in a readily accessible form for industry reference.

Improve damage detection: 
Although safe design aims to avoid unsafe design space, experience suggests that damage detection will remain important to current Fatigue & Damage Tolerance philosophies and to addressing threats and events which may not have been identified in the original threat assessment, e.g., resulting from change in product use to meet evolving and originally unpredicted operational needs, discrete source events (such as Cat 5 blunt impact events, ref. AMC 20-29), unexpected degradation etc. Noting that sandwich structure relies upon bonding, the failure of which may be difficult to detect (e.g. ‘weak bonds’ etc), and also noting that sandwich structure many be subject to other damage modes which may also be difficult to detect (e.g. shear core failure, crushed core followed by skin spring back etc), provide improved substantiated and documented understanding of structure design, manufacture, and in-service damage detection methods (such as Structural Health Monitoring (SHM)) for bonded structure and sandwich structures). This is to also be documented in a readily accessible form for industry reference. 

Hybrid Structure and Continued Airworthiness Strategies: 
Advanced Materials and Processes (AMPs) are often used in products comprising of mixed materials (hybrid structures, e.g., combined metallic and composite structures) which may be difficult to substantiate at certification, e.g., in fuel tanks, for which realistic thermal and mechanical load cycle interaction is difficult to substantiate. Furthermore, competing damage modes (some of which are difficult to detect, see 3/ above) increase the challenge when introducing new technologies/new configurations with the intent to not reduce existing safety levels.  In order to support this intent, the potential exists to use other mitigating actions, e.g., identify candidate structure requiring such attention and to develop supporting Continued Airworthiness Strategies, e.g., Fleet Leader and Sampling etc. The outcome of Task 4 will be a proposed strategy to better address this matter. This is to also be documented in a readily accessible form for industry reference. 

Call for tender

Check the call for tender for this Research Project

Contract duration: 36 months

Important notice:
The call for tender will be issued ahead of the conclusion of the Contribution Agreement between the European Union, represented by the European Commission, and EASA. The conclusion of the aforementioned Contribution Agreement is a prerequisite for the award of any contract resulting from this tender procedure.