This technical teardown chronicles the development and flight testing of the "Ultralight MK5," a manned experimental aircraft constructed primarily from corrugated cardboard. The project explores the structural viability of cellulose-based materials in aviation, focusing on flute orientation for spar integrity, skinning techniques using brown packing paper, and the integration of a redundant "fly-by-wire" wireless control system.
Engineering challenges highlighted include high rolling resistance on unimproved surfaces, susceptibility to hygroscopic degradation (water damage), and the aerodynamic limitations of a low-powered, high-drag airframe. Despite these constraints, the aircraft successfully achieved sustained flight under FAA Part 103 regulations before concluding in a controlled flight into terrain (CFIT) due to maneuverability limits in a confined operating area.
Experimental Flight Log: Cardboard Ultralight MK5
0:01 Project Objective: The mission aims to validate the feasibility of a manned aircraft constructed of approximately 95% cardboard.
1:20 Material Stress Testing: Preliminary testing determined that a combination of vertical and horizontal flute orientations in cardboard ribs provides the highest resilience to structural failure.
2:27 Wing Architecture: Ribs were laser-cut and "hollowed out" to minimize weight. The internal structure uses a boxed-spar design for rigidity.
3:13 Load Calibration: Destructive testing confirmed the wing could support at least 140 lbs, meeting the minimum safety threshold for the pilot's weight.
4:32 Skinning & Aerodynamics: The airframe was skinned with brown packing paper. While significantly less durable than traditional aviation fabric (OEX), it was deemed sufficient for low-speed testing.
5:25 Fuselage Integration: The fuselage is a 17 lb monocoque cardboard structure. A limited amount of plywood was utilized for high-stress hardpoints and wing-joiner boxes (6:53).
8:42 Empennage Design: The tail section (rudder and elevator) utilizes double-layered cardboard and pizza box components for horizontal stabilization.
10:54 Structural Rigging: A temporary aluminum king post was used for ground stability, while fiberglass tape "slings" provided tension-based reinforcement for flight loads.
13:52 Propulsion System: The power plant consists of a quad-motor "push-pull" configuration capable of generating approximately 120 lbs of thrust.
16:18 Flight Control Logic: The aircraft utilizes a "fly-by-wire wireless" system. To mitigate electronic points of failure, the pilot implemented a dual-receiver redundancy scheme, isolating motor controls and split-elevator functions across separate power sources (17:47).
18:34 Avionics: A custom Arduino-based attitude indicator was housed in a pizza box to provide basic flight telemetry.
20:33 Surface Friction Issues: Initial taxi tests failed due to high rolling resistance of the jettisonable landing gear in long grass.
22:32 Material Vulnerability: A shop flood caused significant hygroscopic damage to the trailing edges, requiring a surgical removal and replacement of soggy cardboard (24:03).
24:16 Landing Gear Revision: To achieve takeoff velocity, the builder fabricated a lightweight chromoly steel carriage to reduce weight and rolling resistance.
26:57 Regulatory Framework: The aircraft was designed to comply with FAA Part 103, which governs ultralight vehicles weighing under 254 lbs with a maximum level speed of 55 knots.
32:24 Sustained Flight: Using a vehicle-assisted tow launch, the aircraft achieved sustained, powered flight. The pilot reported sensitive elevator response and successful banking maneuvers.
34:42 Flight Termination: Due to a lack of ailerons (relying solely on rudder/dihedral for roll) and pilot saturation, the aircraft failed to clear a tree line during a circuit, resulting in a low-speed impact.
37:00 Post-Flight Analysis: The impact resulted in a "front fell off" structural failure of the cockpit. The pilot remained uninjured, concluding that while cardboard can achieve manned flight, its lack of maneuverability and environmental sensitivity makes it a suboptimal aviation material.
Recommended Review Panel:
Experimental Aircraft Association (EAA) Safety Officers: To evaluate the risks of non-standard material usage in Part 103 aviation.
Structural Engineers (Materials Science): To analyze the strength-to-weight ratio of corrugated paper in load-bearing aeronautical applications.
FAA Regulatory Analysts: To review the implications of "fly-by-wire" hobby-grade electronics in manned ultralight craft.