Eclipse · DIANA UCLM

The Eclipse is the aircraft with which DIANA went international. After two editions of the XtraChallenge in Valencia, the team entered the Air Cargo Challenge 2026 in Stuttgart —Europe’s reference university competition for cargo aircraft— as team number 26, and finished 25th of 37.

It is the team’s first aircraft built entirely in carbon fibre, and the largest of its edition: a 3.3 m wingspan to carry cans with a motor and battery the rules fix for everyone. It is also the first to fly with a flight controller.

Three years, three materials

The 2026 design builds directly on the two before it. In 2024 the team won the maximum payload award with an aircraft 95 % printed in LW-PLA. In 2025 it moved to a hybrid structure of aircraft-grade wood and heat-shrink film, keeping 3D printing for the complex shapes. In 2026 the cycle focused on mastering composites, carbon and glass, with 3D-printed moulds and resin infusion.

Story

PENDING — the account of the design, the build, the flight tests and what happened in Stuttgart is told by the team. The technical report dates from May 2026, before the competition, so the result and the lessons from the final are not in it.

What went wrong and how it was fixed

PENDING

Technical data

Geometry

Wingspan	3,308 mmThe technical report states 3.00 m without winglets and 3.146 m with them; that is an error in the report. The correct figure is 3,308 mm.
Root chord	0.25 m
Wing area	0.635 m²
Aspect ratio	14.17
Incidence angle	1°
Planform	Semi-elliptical, with a straight leading edge and an elliptical trailing edge, to approximate the elliptical lift distribution and reduce induced drag
Configuration	Mid-wing cantilever, no dihedral, no twist. Manoeuvrability was favoured over some stability
Wing airfoil	Clark Y at 9 % thicknessStarting from the standard Clark Y (11.7 %), 11, 10 and 9 % versions were generated; the 9 % proved most efficient. Initial candidates; Clark Y, E216, S23021 and SD7037.
Tail airfoil	NACA 0008, for its low thickness and drag while still housing a servo inside
Tail	V-tail with 45° dihedral, no vertical stabiliser

Masses

Empty mass	3 kg
Maximum payload	8 cansIn the Air Cargo Challenge the payload is discrete and measured in cans.
Centre of gravity	6.3 cm behind the leading edge empty; 7.4 cm at full load
Design load factor	n = 2 at maximum take-off mass

Performance

Payload prediction	In-house MATLAB script simulating take-off with propulsion data for several propellers, in the historical summer atmosphere of Stuttgart
Cruise speed	PENDINGThe report gives it as curves against payload, not as a single value.
Take-off distance	PENDING

Propulsion

Motor	T-Motor AT2814 900 KV (mandated by the rules)
Propeller	APC 13×8E Thin Electric, each unit statically balancedThe 13×8 and 13×6.5 performed similarly at the 30 A limit; the 13×8E was chosen once the aerodynamic prediction was factored in, for its high-rpm profile and pitch-to-diameter ratio, which keeps cruise speed within the current limit.
ESC	T-Motor AT 40 A, a 25 % margin over the 30 A peak. Its BEC is disabled to isolate power from control and avoid interference
Power battery	3S LiPo, around 3,200 mAhSized for a 320 s mission at 30 A with a 1.2 factor (take-off 20 s, climb 60 s, cruise 120 s, approach 120 s). 3S maximum by the rules. A twin parallel pack was rejected for weight, complexity and failure risk.
Current limit	30 A, imposed by the competition rules

Systems

Flight controller	Matek H743-Wing V3 (STM32H7, integrated IMU). Flown in FBWA mode; the pilot keeps control and the controller corrects attitude
Programmed functions	Electronic current limiting at 30 A via a Hall sensor feeding back to the controller, with low-voltage warning; and a 35° roll limiter, 5° inside the 40° regulatory ceiling
Ground station	Mission Planner
Transmitter	RadioMaster TX16S MKII MAX (ExpressLRS), with voltage and current telemetry on screen
Receiver	RadioMaster ExpressLRS XR1 Nano, 2.4 GHz
Servos	Hacker/Jeti DITEX EL0315M, ~15 g and ~3.8 kgf·cm at 6 V. Minimum torque required; ailerons 1.8, flaps 3.0, ruddervators 1.0
Avionics battery	3S 1,000 mAh LiPo, separate from the power battery, with a ×4 margin over estimated consumption
Buses	Power and avionics kept separate

Structure and manufacturing

Wing skin	Carbon-fibre lay-up with a double leading-edge reinforcement that takes most of the torsion
Main spar	Rohacell with carbon roving, the critical element in bending
Fuselage	Balsa and birch frames forming the cargo bay, with a two-ply carbon skin reinforced with 20 strands of longitudinal 12k roving. Five carbon rods run through the frames and keep the cans apart
Moulds	Two iterations, plaster and 3D printing. 3D printing won on reliability and precision; plaster proved fragile and laborious
Lay-up	Resin infusion for most parts for an even resin distribution; hand lay-up for the most complex geometries. Fibre at ±45° for torsion and shear
By part	Wing, infusion, 1 ply with reinforced leading edge · Fuselage, infusion, 2 plies · Empennage, infusion, 1 ply · Landing gear, hand lay-up, 2 plies
Printed parts	Joints in PA-CF (carbon-filled polyamide); spacers, fixings and control surfaces in LW-PLA; wheels in TPU
Breakdown	The aircraft is split into sections to fit the transport crate