SUAV Operational Vibration Testing & Airframe Analysis
Project: SUAV Operational Vibration Testing & Airframe Analysis
July 2023 · China Aerospace Science and Technology Corporation
A comprehensive operational vibration survey was conducted on a MALE-class UAV at an aviation test center, utilizing ruggedized data acquisition systems to characterize airframe dynamics across 20 flight regimes.
Test Configuration
1. Instrumentation
4 × RE-846U Rugged DAQ Systems (deployed in avionics bay)
Operating temperature: -40°C to +70°C
Shock resistance: 50g, 11ms half-sine
35 triaxial IEPE accelerometers (100mV/g sensitivity)
Locations:
Wing roots (6 nodes, spanwise distribution)
Empennage (vertical & horizontal stabilizers)
Payload bay (structural interface points)
Control surface actuators (servo mounting bases)
2. Test Matrix
| Flight Phase | Key Parameters | Duration |
|---|---|---|
| Taxi | 0.5-5Hz ground-induced vibration | 120s |
| Takeoff (100% throttle) | 10-500Hz engine harmonics analysis | 45s |
| Climb (15° pitch) | Buffet boundary identification | 180s |
| Cruise (FL200) | Aeroelastic mode excitation | 300s |
Data Acquisition & Processing
Sampling:
Baseband: 2kHz/channel (0-1kHz analysis BW)
Zoom FFT: 25.6kHz for gearmesh frequency monitoring
Synchronization:
PTPv2 time synchronization (±50μs inter-system alignment)
Flight parameter triggers (via ARINC 429 bus)
Analysis Methods:
PSD (Hanning window, 50% overlap)
Order tracking (shaft speed referenced)
Transmissibility analysis (control surface to airframe)
Key Findings
1. Structural Dynamics
Discovered 37Hz wing bending mode coinciding with:
2nd engine harmonic (potential flutter risk)
Mitigated via stiffener reinforcement (8% mass penalty)
2. Propulsion-Induced Vibration
Identified 540Hz gearmesh resonance exceeding:
MIL-STD-810G Category 14 limits
Resolved with isolator redesign (attenuation >12dB)
3. Control System Interaction
Measured servo-induced vibrations at:
22Hz (aileron actuation frequency)
88Hz (PWM-related harmonics)
Engineering Outcomes
Design Changes Implemented
Added constrained layer damping to payload bay (vibration reduction: 35% @ 50-200Hz)
Optimized servo update rate from 400Hz to 450Hz to avoid structural modes
New Maintenance Protocols
Established vibration-based wear indicators for:
Engine mounts (alert threshold: 4.2g RMS @ 1/rev)
Control hinges (3σ exceedance monitoring)
Certification Support
Provided compliance evidence for:
DO-160G Section 8 (vibration)
ASTM F3200 UAV airworthiness standards
Technical Terms
MALE: Medium Altitude Long Endurance
IEPE: Integrated Electronics Piezo-Electric
PSD: Power Spectral Density
This test established baseline vibration signatures for the UAV fleet, enabling condition-based maintenance with 92% fault detection accuracy.
