ISO-Plane TRL3

ISO-Plane TRL3

ISO-Plane TRL3 defines the transition of the ISO-Plane program from a validated conceptual architecture toward a technically substantiated engineering definition.

At this stage, the project is no longer limited to architectural feasibility. It enters a phase where the main assumptions must be supported by calculations, simulations, preliminary tests, subsystem sizing and structured technical risk reduction.

TRL3 is therefore the first maturity level where the ISO-Plane becomes an engineering-driven aircraft concept, with the objective of preparing the program for demonstrator design, industrial dialogue and future TRL4 maturation.

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Executive Summary

TRL3 corresponds to the analytical and experimental proof-of-concept phase of the ISO-Plane program.

The purpose of this phase is to verify that the selected aircraft architecture can credibly support the transport, autonomous loading, unloading and flight operation of one standard 20-foot ISO container.

The TRL3 work focuses on:

• structural feasibility of the fuselage and ventral cargo opening;
• validation of the cargo lifting and locking load paths;
• aerodynamic refinement of the high-wing twin-engine configuration;
• integration of Q400-derived landing gear into the nacelle architecture;
• consolidation of mass, balance and mission performance;
• preliminary systems architecture definition;
• identification and reduction of major technical risks;
• preparation of the project for industrial and pre-certification discussions.

TRL3 does not aim to produce a flying prototype. Its objective is to produce engineering credibility.

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Program Context

The ISO-Plane is a specialized cargo aircraft concept designed to transport a single 20-foot ISO container while remaining significantly smaller than conventional military transport aircraft capable of carrying containerized freight.

The aircraft is intended to provide autonomous loading and unloading capability, either from the ground or directly from a truck trailer, without requiring heavy external airport handling equipment.

The reference configuration includes:

Parameter	TRL3 reference assumption
Mission	Air transport of one 20-foot ISO container
Payload objective	Up to approximately 8 tonnes of containerized payload
Loading concept	Autonomous loading and unloading through a ventral cargo access system
Propulsion	Twin turboprop configuration using Pratt & Whitney PW150A-class engines
Wing configuration	High-wing architecture
Landing gear concept	Main landing gear derived from Bombardier Q400 architecture, integrated into the nacelles
Cargo bay	Pressurized cargo compartment compatible with a 20-foot ISO container
Cockpit	Pressurized cockpit, crew of two, with operational access independent from the cargo bay
Design ambition	Long-range container air logistics with autonomous ground handling

The TRL3 baseline remains a design target, not a certified aircraft definition.

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TRL Context

Technology Readiness Level 3 corresponds to an early proof-of-concept stage.

For ISO-Plane, TRL3 means that the main technical principles selected during TRL2 must be tested against engineering reality.

TRL3 includes:

• analytical proof-of-concept;
• preliminary experimental proof-of-concept when possible;
• subsystem feasibility validation;
• first-order structural verification;
• aerodynamic model refinement;
• mechanical integration studies;
• preliminary failure and risk analysis;
• preparation of subsystem demonstrators;
• identification of technical gaps toward TRL4.

TRL3 is the first phase where the program must demonstrate that the architecture is not only innovative, but also technically defendable.

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TRL2 to TRL3 Transition

Status Achieved at TRL2

The end of TRL2 established a coherent conceptual architecture for the ISO-Plane.

The following elements are considered part of the TRL2 baseline:

• global aircraft architecture selected;
• high-wing twin-turboprop layout retained;
• 3D digital mock-up created;
• loading system concept defined;
• ventral cargo door concept selected;
• rear access and cargo bay layout investigated;
• PW150A engine family selected as propulsion reference;
• Q400-derived landing gear integration concept retained;
• preliminary fuselage sizing completed;
• preliminary mass and performance estimates produced;
• initial market and operational studies performed;
• first collaborative project structure established between academic contributors.

TRL3 Entry Logic

The TRL3 phase starts when the aircraft is sufficiently defined to allow engineering verification.

The main TRL3 question is:

Can the ISO-Plane architecture withstand preliminary structural, mechanical, aerodynamic and operational scrutiny?

To answer this, TRL3 must convert the digital mock-up into a structured engineering definition.

TRL3 Exit Logic

TRL3 may be considered complete when the critical concepts are validated by analysis and supported by credible simulation or preliminary test evidence.

The expected TRL3 exit condition is not a prototype, but a mature technical dossier enabling the launch of TRL4 demonstrators.

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TRL3 Objectives

The main objectives of TRL3 are:

• perform detailed structural calculations on critical zones;
• validate the feasibility of a large ventral opening in a pressurized fuselage;
• refine the aerodynamic configuration using CFD and analytical methods;
• verify the mechanical logic of the autonomous cargo handling system;
• assess the load paths generated by lifting an 8-tonne ISO container;
• consolidate the central wing box configuration;
• verify landing gear integration into nacelle structures;
• update the aircraft mass breakdown;
• refine the center-of-gravity envelope;
• assess cargo loading and unloading stability;
• identify the highest technical risks;
• prepare subsystem demonstrator requirements for TRL4;
• initiate structured technical exchanges with industrial partners.

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TRL3 Engineering Philosophy

TRL3 is based on a conservative engineering approach.

The objective is not to optimize every parameter immediately, but to identify whether the core architecture is structurally and mechanically viable.

The guiding principles are:

• prioritize feasibility before optimization;
• validate load paths before refining geometry;
• use conservative margins where uncertainty remains high;
• separate architectural assumptions from verified engineering results;
• document every major hypothesis;
• identify the assumptions that must be tested physically at TRL4;
• maintain compatibility with open-source collaboration while protecting potential industrial interfaces.

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Configuration Baseline at TRL3 Entry

Aircraft Architecture

The ISO-Plane TRL3 reference architecture is a high-wing twin-turboprop aircraft with a pressurized fuselage and a ventral container loading system.

The aircraft is designed around the geometric constraints of a 20-foot ISO container.

The general layout includes:

• forward cockpit;
• pressurized cargo bay;
• high wing and central wing box;
• twin turboprop propulsion;
• rear empennage structure;
• nacelle-mounted main landing gear;
• ventral cargo door;
• mechanized cargo handling system;
• twist-lock-based container attachment interfaces.

Cargo Bay Architecture

The cargo bay must accommodate one standard 20-foot ISO container while preserving sufficient structural continuity around the fuselage.

Key design constraints include:

• container external length compatibility;
• lateral clearance for loading operations;
• vertical clearance for container motion;
• structural clearance around the ventral opening;
• compatibility with pressurization loads;
• integration of lifting arms or mechanized load transfer elements;
• integration of locking points;
• access to emergency securing systems;
• maintainability of the cargo handling equipment.

Ventral Door Architecture

The ventral cargo door is one of the defining systems of the ISO-Plane.

At TRL3, the retained concept is a three-panel opening system allowing ground-level access for loading and unloading a 20-foot ISO container.

The ventral door must:

• preserve aerodynamic continuity in flight;
• support pressurization sealing requirements;
• avoid structural weakening of the fuselage beyond acceptable limits;
• provide sufficient opening clearance for the container;
• remain compatible with internal floor or guide structures;
• withstand local loads from cargo handling interfaces;
• support emergency closing and locking logic;
• remain inspectable and maintainable.

Landing Gear Architecture

The main landing gear is derived from the Bombardier Q400 concept and is integrated into the nacelles below the high-mounted wings.

This architecture is retained because it avoids occupying the lower fuselage volume required by the cargo bay and ventral opening.

The TRL3 landing gear integration studies must verify:

• nacelle structural reinforcement;
• landing load transfer into wing and engine support structures;
• retraction kinematics;
• wheel well packaging;
• gear door integration;
• compatibility with propeller clearance;
• ground stability during loading;
• compatibility with truck and ground loading scenarios.

Propulsion Architecture

The TRL3 propulsion reference remains the Pratt & Whitney PW150A engine class.

This engine family is used as a sizing and integration reference for:

• power-to-weight estimation;
• nacelle sizing;
• propeller clearance studies;
• fuel consumption modelling;
• operational range estimation;
• integration with Q400-derived systems and landing gear concepts.

At TRL3, the engine selection is not yet a procurement decision. It is a technical baseline for configuration development.

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