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Flightworthy Flush Lightweight doors for unpressurized Fast Rotorcraft

Periodic Reporting for period 4 - FRCDoorDemonstrator (Flightworthy Flush Lightweight doors for unpressurized Fast Rotorcraft)

Reporting period: 2020-06-01 to 2021-09-30

The Joint Technology Initiative Clean Sky 2 has the goals to showcase novel material, process, etc. technologies on different Integrated Technology Demonstrators (ITDs). Green Rotorcraft is one of the six strategic areas. In there, Airbus Helicopters developed RACER - the Rapid and Cost-Effective Rotorcraft.

RACER represents an important European technology development by the Joint Undertaking. It enables a higher cruising speed, longer flight ranges, hence longer rescue missions, lower fuel consumption as well as low gas emission, low community noise impact, and high productivity for operators. RACER is one of the latest and most advanced developments which will secure the technological as well as economical frontrunner position of Airbus Helicopters in the field of helicopters. This is important for society in various ways: on the one hand RACER will be a very sustainable mobility system due to implementation of most efficient and clean drive train technologies contributing to the European Green Deal Goals for 2050. On the other hand, the technologies used in RACER will need highly skilled experts for manufacturing, assembly, repair, maintenance and further future advancement.
Overall objectiv of Green aircraft ITD is to develop, manufacture and test a large scale flightworthy demonstrator RACER embodying the new European compound rotorcraft architecture to be designed, integrated and flight tested.

The project FRCDoorsDemonstrator is one of many parallel development activities which contribute to the final goal of a first flightworthy RACER demonstrator.
In FRCDoorsDemonstrator, it is goal to develop the following four (five) mandatory doors: 1a) Pilot door (left-hand-side), 1b) Co-Pilot door (right-hand-side), 2) Sliding Cabin door including the door-frame (left-hand-side), 3) Luggage door (left-hand-side), and 4) the rear Avionic door. For all doors it is task to design, size, manufacture, test, assembly and deliver the different doors in final flightworthy configuration to topic manager Airbus Helicopters. It is issue to take aerodynamic configuration, highly ambitious weight and power targets as well as emission reduction targets into account so to achieve increased flight speeds and reduced emissions and noise for the RACER.

Although the design and development of the underlying design-concepts for the different doors took a very long time, the joint collaboration between the FRCDoorsDemonstrator consortium, in special the experts of CI Composite Impulse, and the topic manager was fruitful. In the end, the manufacturing, final finishing and preparation for final assembly could be demonstrated. All doors (see pictures attached) were realized and provided to Airbus Helicopters for final mounting to the RACER.
Since start of the project in 2015, the different door systems have been designed along very detailed technical requirement specifications and pre-concept investigations of Airbus Helicopters.
In the initial design phase, only inner helicopter space, outer aerodynamic flight surface as well as interfaces (structures, electrics, pipings, sensors, etc.) between the neighbouring development systems were available. Designs of the single systems and sub-systems were developed based on existing requirements and needs of Airbus Helicopters. Where needed these were adapted according to clashes or non-compliances detected in multiple design loops.

After passing PDR and CDR, all designs were transferred into 3-dimensional CAD models which contained full details. These were a) used to run structural simulations by means of finite element methods and b) to derive 2D drawings for mould manufacturing as well as final doors manufacturing. In the final phase of the project, the five demonstrator doors were put into real. All single composite parts were manufactured using composite technologies at highest level. In some cases the use of single-run poly-urethan tools were sufficient. In some cases black composite tools were mandatory so to achieve dimensional stability for the large parts and to maintain within the given tolerance boundaries. After final assembly the doors received the basic coating. Final painting will be done by Airbus Helicopters.

Besides the outcomes "demonstrator doors" the project lead to additional results for the consortium partners. For CI Composite Impulse it was the first time to closely work together with partner Airbus Helicopters and to experience the development field of helicopter systems. CI Composite Impulse was able to improve their composite processing technologies. As well, CI installed materials testing systems which allow them to run inhouse tests and to set up material data basis for their internal use. Coordinator LKR for the first time accompanied such a big and complex development project - consisting of many sub-systems and consortia.

The project status has been regularly communicated to AH and to the project officer. Support has been given for higher level CleanSky2 presentations CI published a press release at Fachhochschule Dortmund in 2018. LKR has distributed information by using AIT webpage and CORDIS. Social media channels (LinkedIn, Facebook, AIT-web-page, …) have been used to distribute results at the end of the project when demonstrator doors were available.
DEC of results will be continued post-project at the following conferences: LKR Light Metals Technologies Conference 2022 (Salzburg), Aircraft Interior Trade Fair 2022 (Hamburg). Sales department of CI Composite Impulse will integrate information and results of the project into its company presentations. As such, gained expertise and process technologies will be offered to their customer networks for future commercial exploitation.
The weight and efficiency targets of RACER are very ambitious. With state-of-the-art design and manufacturing concepts it would not be possible to meet envisaged overall performance targets of RACER. The combined approach of new flight concept together with high performance low weight composite manufacturing technology for the major primary structure of RACER including the doors will contribute to reaching the final flightworthy high performance fast rotorcraft.

The FRCDoorDemonstrator consortium achieved the following progress beyond the state of the art:

- Aerodynamic quality: all doors have a design which is free of diturbing attachements. They are perfectly integrated into the outer skin of the fuselage. Gaps and sealing systems do perfectly match. This all contributes to a minimum air resistance for the RACER.

- Lightweight design: Composite technology has been used for >90% of the doors´structures. Only a view elements such as fasteners, threads, locking / latching elements and mechanisms are made of metal. In this way the doors weight 25% less than conventional helicopter doors.

- Maintenance performance: All latching and locking systems are integrated in a way that these are easy accesible and able to be installed, repaired or distmantled.

- Tolerances: By using composite technology for all doors it was possible to maintain smallest structural tolerances even for the doors with large dimensions such as pilot doors or cabin door.

- Safety: Cockpit doors and cabin door are equipped with provisions so to arrest the doors in open positions, for i.e. rescue operation conditions. Furthermore, they contain provisions for the installation of emergency exit windows which can be jettisoned.
Rear Avionic door
Luggage door
Collection of RACER doors ready for shipment
Cabin door
Released concept of Fast RotorCraft RACER – Paris Air Show, Le Bourge, June 2017, Courtesy by Airbus
Right-hand Cockpit door