Minibee TRL4

TRL 4 – Mini-Bee | Technology Validated in Laboratory

At TRL 4, the Mini-Bee project entered a more advanced demonstrator-oriented phase. The objective of this stage is to validate key technologies in controlled environments, including the hybrid power chain, the physical and digital mock-ups, the Flight Control Unit, the structural assumptions and the first subsystem test benches. This page documents the active TRL 4 work carried out during the 2022/2023 academic year and the continuation of the Mini-Bee development after TRL 3.

Mini-Bee project development roadmap – TRL4 transition

Quick project summary

Project Mini-Bee

TRL stage TRL 4 – Technology Validated in Laboratory

Main period documented Academic year 2022/2023

Main focus Subsystem validation, FCU, hybrid power chain and mock-ups

TRL 4 visual overview

Rotor architecture Front view of the historical TRL4 distributed rotor configuration. Open image

Cockpit structure Cockpit and seat integration mock-up used for structure and ergonomic studies. Open image

Development roadmap Project development steps showing the progression from early mock-ups to demonstrator work. Open image

Previous TRL steps

TRL 1 – Basic principles observed Initial mission need, basic principles and first assumptions. Open TRL 1 – Mini-Bee

TRL 2 – Technology concept formulated First concept configuration, academic studies and early mock-ups. Open TRL 2 – Mini-Bee

TRL 3 – Experimental proof of concept Simulations, technical reviews, FCU prototypes and early test benches. Open TRL 3 – Mini-Bee

Visual introduction – 2023 work

File:15 02 2023 Soutenance finale compressed.pdf Ecole Centrale Lille Technical contribution and project presentation. Open document	File:202305 Projet MiniBee Soutenance finale corrigé.pdf Power chain Estaca Bordeaux work on the Mini-Bee power chain. Open document	File:202305 Soutenance MiniBee ESTACA 3A BDX Structure.pdf Physical mock-up Reduced-scale physical mock-up and structural work. Open document
File:2023 05 09 Soutenance.pdf Digital mock-up Estaca SQY digital mock-up and configuration studies. Open document	File:202305 Présentation Soutenance versionF.pdf Hybrid propulsion Work on hybrid propulsion architecture and assumptions. Open document	File:25042023 Présentation final MiniBee.pdf FCU prototype Cytech work on the Flight Control Unit prototype. Open document

Project overview

TRL 4 – Technology Validated in Laboratory corresponds to the stage where the Mini-Bee project started to consolidate and validate key technologies in controlled or representative environments.

At this level, the project is no longer only based on theoretical assumptions. The work begins to focus on subsystem validation, prototype logic, test benches, mock-ups, control architecture and the preparation of more representative demonstrator activities.

TRL 4 objective: validate the main technical building blocks of the Mini-Bee concept through laboratory work, mock-ups, subsystem studies and early controlled testing.

Tasks of academic year 2022 / 2023

The 2022/2023 period focused on several major technical work packages: power chain, physical mock-up, digital mock-up, hybrid propulsion and Flight Control Unit development.

Contributor	Work package	Documents
Ecole Centrale Lille	Technical contribution and project presentation	File:15 02 2023 Soutenance finale compressed.pdf
Estaca Bordeaux 3A	Power chain	File:202305 Projet Ingénieur ESTACA CR Final.pdf File:202305 Projet MiniBee Soutenance finale corrigé.pdf
Estaca Bordeaux	Reduced-scale physical mock-up	File:202305 Rapport de projet industriel - Projet Mini-Bee.pdf File:202305 Soutenance MiniBee ESTACA 3A BDX Structure.pdf
Estaca SQY	Digital mock-up	File:2023 05 09 Document support.pdf File:2023 05 09 Rapport final.pdf File:2023 05 09 Soutenance.pdf
Estaca SQY	Hybrid propulsion	File:202305 Présentation Soutenance versionF.pdf File:202305 Rapport de projet.pdf

FCU tasks

The Flight Control Unit is a critical subsystem for Mini-Bee because the aircraft relies on distributed electric propulsion and computerized flight control logic.

During TRL 4, several academic teams worked on FCU-related tasks, including prototype logic, STM / Arduino exercises, control studies and system architecture.

Contributor	Scope	Documents
Estaca SQY 4A	FCU development and presentation	File:20230425 Soutenance finale P2I 4A.pdf
Cytech	FCU prototype and project work	File:25042023 Présentation final MiniBee.pdf
Esigelec	FCU / electrical system work	File:20230203 ESIGELEC PING2 réunion 10.pdf

Arduino and STM exercises – FCU 2022 / 2023

The FCU training and prototyping work also included Arduino and STM Nucleo exercises carried out by Estaca and Cytech.

Arduino FCU Exercice Arduino FCU

STM Nucleo FCU Exercice STM Nucleo FCU

Arduino FCU – English Exercise Arduino FCU English

STM Nucleo FCU – English Exercise STM Nucleo FCU English

Main TRL 4 technical areas

Hybrid power chain Work on the generation, conversion and distribution of electrical power for distributed propulsion.	Physical mock-up Reduced-scale and structural mock-up activities to support integration and configuration studies.	Digital mock-up Digital model development to improve the understanding of aircraft layout, structure and integration.
Hybrid propulsion Studies on the interaction between thermal generation and electric propulsion systems.	Flight Control Unit FCU development, control logic, STM exercises and distributed rotor control preparation.	Subsystem validation Preparation of laboratory validation logic before full demonstrator integration.

TRL 4 configuration visuals

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  Distributed rotor architecture

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  Cockpit structure and seat integration

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  Project development steps

TRL 4 development logic

The TRL 4 phase supports the transition from proof of concept to controlled validation of key technologies.

1. Consolidate	2. Prototype	3. Validate	4. Integrate	5. Prepare TRL 5
TRL 3 results	FCU, mock-ups and power chain	Laboratory and controlled tests	Subsystem consistency	Relevant environment validation

What TRL 4 covered

Covered during TRL 4 power-chain studies; reduced-scale physical mock-up; digital mock-up work; hybrid propulsion studies; FCU prototype activities; Arduino and STM Nucleo exercises; subsystem-level validation preparation; stronger link between concept and demonstrator work.

Still open after early TRL 4 work complete full-scale validation; flight-ready FCU architecture; complete hybrid chain ground-test validation; full structural test evidence; complete certification compliance matrix; representative operational environment tests.

Visual archive – 2023 documents

The following documents support the TRL 4 visual and technical archive for the 2022/2023 academic year.

File:202305 Rapport de projet industriel - Projet Mini-Bee.pdf Physical mock-up report Open document

File:2023 05 09 Rapport final.pdf Digital mock-up report Open document

File:20230425 Soutenance finale P2I 4A.pdf FCU presentation Open document

Image and document files used on this page

Wiki file name	Use in page	Link
MiniBee_TRL4_60_rotors_front_view.png	TRL4 rotor architecture visual	Open image
MiniBee_TRL4_cockpit_structure_mockup.png	Cockpit structure and seat integration visual	Open image
MiniBee_TRL4_project_development_steps.png	Hero visual and project development roadmap	Open image
15 02 2023 Soutenance finale compressed.pdf	Visual introduction and Ecole Centrale Lille task	Open document
202305 Projet MiniBee Soutenance finale corrigé.pdf	Visual introduction and power-chain task	Open document
202305 Soutenance MiniBee ESTACA 3A BDX Structure.pdf	Visual introduction and physical mock-up task	Open document
2023 05 09 Soutenance.pdf	Visual introduction and digital mock-up task	Open document
202305 Présentation Soutenance versionF.pdf	Visual introduction and hybrid propulsion task	Open document
25042023 Présentation final MiniBee.pdf	Visual introduction and FCU task	Open document
202305 Rapport de projet industriel - Projet Mini-Bee.pdf	Visual archive and physical mock-up documentation	Open document
2023 05 09 Rapport final.pdf	Visual archive and digital mock-up documentation	Open document
20230425 Soutenance finale P2I 4A.pdf	Visual archive and FCU documentation	Open document

Why TRL 4 matters

TRL 4 is a key maturity step because it connects the Mini-Bee concept to laboratory-level validation.

It helps transform the work from studies and proof-of-concept activities into controlled subsystem validation. It also prepares the project for later stages where technologies must be tested in more representative environments.

Transition to the next stage

Next maturity step: Mini-Bee TRL 5 – Technology Validated in Relevant Environment.

At TRL 5, the project should move from laboratory validation toward tests in conditions closer to real operational use.

See also

• Mini-Bee TRL 1
• Mini-Bee TRL 2
• Mini-Bee TRL 3
• Mini-Bee project