Deployed units showed servo whirring, stalling, and burnout. The 3.6g micro servo (rated 0.7 kg/cm) was running at the edge of its torque budget under cable tension during pan motion, the highest dynamic load moment. Before swapping the servo, I needed to confirm torque was the actual failure mode.
02 / AutoPlane
AutoPlane — Fuselage Architecture & Internal Layout
Owned the fuselage from architecture selection through internal component layout for a fixed-wing autonomous survey UAV. Manufactured and assembled Spring 2026.
Role
Mechanical Systems Engineer, Airframe
Aircraft
1.2m span · 50 mph cruise · 10 lb payload · S1223 airfoil
Tools
SolidWorks, XFLR5
Team
8 members / 3 subteams — 25 selected from 164 applicants
Option A
Central Pod + Twin Boom
Better downward camera FOV. Cleaner motor placement. But: more structural joints, flutter risk at boom-empennage connection, higher assembly complexity on a first build.
Selected ✓
Slender Pod Monocoque
Lowest drag at Re ~2×10⁵. Skin carries structural loads, so less internal reinforcement mass. Compatible with foam milling and vacuum-bagged composites. Moment arm improves stability without an oversized tail.
The tradeoff: a belly aperture for the camera instead of an unobstructed boom-mounted view. Hit our AUW targets.
Full CAD assembly — 15% gyroid wing infill visible
Every component pushed back on the fuselage geometry. The internal envelope had to fit the full avionics stack while holding CG placement, vibration isolation, and serviceability.
Fuselage internal cavity — designed around component stack
| Component | Constraint imposed on fuselage |
|---|---|
| PM02D Power Module | Near CG — short high-current runs to PDB, placement fixed internal bay geometry |
| Dual GPS | Requires separation + clear sky exposure — constrained upper fuselage geometry |
| Pixhawk 6X | Positioned for IMU isolation from motor vibration — affects mount stiffness design |
| D3548 Motor | Tractor config — CG and nose geometry set by motor mass forward of wing |
| Raspberry Pi | Thermal management — requires airflow clearance, can't be adjacent to battery |
Full LW-PLA airframe in strong foaming configuration. The choice was driven by minimizing wing loading on a structurally aerodynamic (not load-bearing) airframe: carbon spars carry the primary loads, infill contributes stiffness only. 15% gyroid infill selected based on research showing isotropic stiffness and damage tolerance under flight loads.
Fuselage redesigned with a modular removable nose section, giving direct access to internal avionics without full disassembly. A DFM call driven by field serviceability. Nozzle temperature tuned to 240°C through controlled test prints.
Modular removable nose — direct access to internal avionics
Print deformation vs nozzle temperature
Fabrication — Frith Lab
Picked the S1223 for the wing because it gave the high CL we needed at our cruise Reynolds, gentle stall behavior at 13° AoA, and enough thickness to fit the internal spar. The numbers: CL max ~2.2, cruise CL ~1.4 at 2.5° AoA, lift calculation confirming 16.98 lbf at 22.35 m/s. Static margin of 16% kept handling stable and responsive.