Flight Test Programs

ARW Ring-Wing
Flight Campaigns

Two full-scale distributed-electric propulsion flight campaigns — 81 sorties across two test articles and two continents. Most eVTOL concepts are renderings. These flew.

81
Total Sorties
Both Campaigns
49
ARW19 Sorties
Pendleton 2024
32
ARW38 Sorties
Singapore 2025
38
Max Rotors
ARW38 Config
12m
Max Altitude
AGL (all sorties)
Campaign 1 · 2024 · Pendleton, Oregon
ARW19 — Triple Nickel 001
Vehicle designationUS Triple Nickel (UAS)
Rotor count19 rotors
ConfigurationSingle annulus
Scale20% scale article
Aircraft mass19.2 kg
Test facilityPendleton UAS Range, OR
Airworthiness authorityACUASI / UAF
FAA registrationFA3FKKPXK3
Flight controllerCubePilot / ArduPilot
ESC architectureDroneCAN 19×
Battery energy1.78 kWh @ 50.4V
Campaign outcomeVehicle survived ✓
Campaign 2 · 2025 · Singapore, Aerial Arena
ARW38 — GOAERO Stage 2
Vehicle designationGOAERO Stage 2
Rotor count38 rotors
ConfigurationTwin annuli (2 × 19)
ScaleFull-scale article
Aircraft mass78.0 kg
Test facilityAerial Arena, Singapore
Airworthiness authorityAerial Industries Pte. (201919466C)
Flight controllerCubePilot Orange + Lua
ESC architecture32 DroneCAN + 6 PWM
Battery energy3.55 kWh (8 × 6S 20Ah)
Campaign outcomeStructural incident — F32

Campaign 1 · Pendleton, Oregon · 2024

ARW19 —
"Triple Nickel 001"

19
Rotors

Sortie Outcome Breakdown — 49 Sorties

22 Pass
13 Marginal
12 Abort
1
2
Pass (22)
Marginal finding (13)
Engineering abort (12)
Failed / repair required (1)
Requires allocator update (2)
Rotor Layout
1+6+12center + inner + outer ring
Total Disk Area
2.785 m²19 × 17-inch rotors
Disk Loading
67.6 N/m²at 19.2 kg MTOW
Hover RPM
4,550 RPMfigure of merit 0.62
Hover Power
1.84 kWestimated (1.01 kW ideal)
Max Altitude
12.0 m AGLLOS safety cap (all sorties)

Key Engineering Findings

Underdamped 3–4 Hz Pitch/Heave Oscillation Mode
Detected across multiple dynamic stability sorties (F30, F32). Estimated damping ratio ≈ 0.18 — well below the 0.35 threshold targeted for stable eVTOL flight. Mode excited by combined roll/yaw manoeuvres and persisted across retries, driving an allocator architecture review. Peak DDRM score 0.994 on repeated exposures.
12–13 Hz Rotor Ring Flutter-Like Vibration Band
Present in all vibration sorties (F33, F37, F47). Vibration Z RMS reached 67.5–93.4 mg — significantly above baseline idle levels (~21 mg). Attributed to propeller–ring structural interaction. A propeller strike on R08 during F31 terminated that sortie; post-replacement retries confirmed the flutter mode persisted at structural level.
Asymmetric Rotor Inflow — 25–30% Thrust Spread
Lateral-directional control sorties (F18, F20) showed issue-window thrust spread reaching 23–24% above median, with DDRM scores saturating at 1.000. Attributed to asymmetric inflow across the ring arc during side-translation. Inspection of inner-ring inflow baffles was recommended. Forward-flight sorties also showed low-Re lift drop-off at speed.
Control Allocator Saturation Under Rotor-Out Conditions
Min-control rotor-out tests (F25, F35) drove allocator saturation to 96.2% and 0% spare margin respectively — classified as requiring allocator update. CAN harness segment failures (F34, F39) compounded degraded-mode testing and required full harness replacement on segments A and B.
Thermal Margin at Ceiling (11.5–12 m AGL)
Extreme envelope ceiling climb (F38) achieved 12 m AGL with interaction losses rising to 20.5–25.5% and allocation saturation reaching 76%. One prior abort (F37) at 11.8 m due to ESC thermal derate. Tonal acoustic levels peaked at 74–76 dB(A) at 50 m during ceiling hold. Campaign closed with a clean noise sortie (NOISE_FTR_ANALOG, F42: pass).

Selected Sortie Log

Sortie Test ID Type Mean Inflow Loss Vib. Z RMS (mg) Max Altitude Result
F04TAKEOFFRetry6.5%22.012.1 mPass
F06CLIMBRetry6.5%21.912.1 mPass
F18LAT/DIR CONTROLPrimary16.7%67.72.0 mMarginal
F25MIN CONTROL (ROTOR-OUT)Primary14.3%41.32.0 mAllocator Update Req.
F30DYNAMIC STABILITYPrimary14.4%67.62.0 mMarginal
F33VIBRATIONPrimary17.9%67.52.0 mMarginal
F38CEILING CLIMBPrimary20.5%49.212.0 mMarginal
F40COMBINED AGILITYPrimary22.3%93.42.0 mMarginal
F42NOISE (50 m)Primary11.0%41.32.0 mPass — 76.6 dB(A)

Campaign 2 · Singapore, Aerial Arena · 2025

ARW38 —
GOAERO Stage 2

38
Rotors

Sortie Outcome Breakdown — 32 Sorties

21 Pass
3
7 Abort
I
Pass (21)
Marginal finding (3)
Engineering abort (7)
Structural incident — F32 (1)
Rotor Layout
2 × (1+6+12)twin annuli, 38 stations
Total Disk Area
5.570 m²38 × 17-inch rotors
Disk Loading
137.3 N/m²at 78.0 kg MTOW
Hover RPM
5,200 RPMfigure of merit 0.66 (+6.5%)
Hover Power
9.99 kWestimated (5.84 kW ideal)
Max Altitude
12.0 m AGLLOS safety cap (all sorties)

Key Engineering Findings

Improved Dynamic Stability — Damping Ratio +89%
Dynamic stability sortie (F21) recorded a damped 3 Hz pitch/heave mode with estimated damping ratio ≈ 0.34, compared to 0.18 in ARW19. Classified as an engineering pass. The twin-annulus electrical architecture and revised control allocation matrix directly contributed to this improvement, validating the ARW19 allocator-update requirement.
Reduced 12 Hz Vibration Band — ~48% Lower
Vibration Z RMS in the dominant 12 Hz band dropped from 67–93 mg (ARW19) to 34–35 mg (ARW38) in normal sorties. Interaction losses in steady hover reduced to ~6.5% vs 11–18% in ARW19. The vibration sortie (F23) passed engineering review; an earlier abort (F22) triggered by a PWM ESC desolder was corrected within the same campaign day.
Elevated Ring-Wing Load at High-Speed Translation (8 m/s)
Extreme envelope high-speed translation (F29) at 8 m/s and 4–6 m AGL recorded interaction losses rising to 11.7–15.5% and allocation saturation reaching 30.4%. Classified as marginal. Vibration Z RMS reached 54.8 mg — within acceptable range but elevated. Structural load on the ring attachment was flagged for redesign review.
F32 — Structural Limit Impact: Campaign Termination
The final sortie (F32, EXT_523277_STRUCTURE_LIMIT_CRASH) resulted in a structural limit impact that destroyed the fuselage, terminating the campaign. Vibration Z RMS reached 217.3 mg — approximately 10× nominal hover levels. Acoustic levels peaked at 93 dB(A) at 50 m. Allocation saturation at 67.6% in the pre-impact window. Engineering incident classification: airframe loss. No personnel injuries recorded.
Noise Profile — 84 dB(A) at 50 m (Pass)
Acoustic trace sortie (F27) recorded a peak of 84.0 dB(A) at 50 m — louder than ARW19's 76.6 dB(A), consistent with the higher disk loading of the 78 kg aircraft. Tonal noise spike above 75 dB(A) was noted, but the sortie passed the noise flight test requirement. Wind contamination aborted an earlier acoustic attempt (F26).

Selected Sortie Log

Sortie Test ID Type Mean Inflow Loss Vib. Z RMS (mg) Max Altitude Result
F04TAKEOFFRetry6.5%21.912.0 mPass
F11LONGITUDINAL CONTROLPrimary7.3%22.02.0 mPass
F13LAT/DIR CONTROLPrimary8.4%35.02.0 mPass
F18MIN CONTROL (ROTOR-OUT)Primary8.2%21.92.0 mPass ↑ vs ARW19
F21DYNAMIC STABILITYPrimary7.5%34.92.0 mPass — ζ=0.34 ↑
F23VIBRATIONPrimary9.3%34.92.0 mPass ↑ vs ARW19
F27NOISE (50 m)Primary6.5%22.12.0 mPass — 84.0 dB(A)
F29HIGH-SPEED TRANSLATIONPrimary11.7%54.85.3 mMarginal
F31HARD LANDINGPrimary7.5%95.912.0 mMarginal — repair reqd.
F32STRUCTURE LIMIT CRASHPrimary13.4%217.312.0 m⚠ Incident — Airframe Loss

Campaign-over-Campaign Analysis

ARW19 → ARW38
What Improved

Key engineering metrics comparing the 2024 19-rotor campaign to the 2025 38-rotor twin-annulus campaign.

Flight Dynamics
Dynamic Stability
Pitch/heave mode damping ratio improved from ζ ≈ 0.18 (ARW19, marginal) to ζ ≈ 0.34 (ARW38, pass). The dominant mode frequency shifted from 3.35 Hz to 3.05 Hz. Revised Lua motor-matrix allocation directly addressed the ARW19 finding.
ARW19: ζ = 0.18 ARW38: ζ = 0.34 ↑89%
Structural Vibration
Vibration Z RMS
12 Hz ring-flutter vibration Z RMS dropped from 67–93 mg in ARW19 dynamic/vibration sorties to 34–35 mg in equivalent ARW38 sorties — approximately 48% reduction. Confirmed by multi-sortie vibration sweep comparison across both campaigns.
ARW19: 67–93 mg ARW38: 34–35 mg ↓48%
Propulsion
Figure of Merit
Rotor figure of merit (FM) improved from 0.62 (ARW19) to 0.66 (ARW38) due to optimised rotor station spacing in the twin-annulus configuration. Mean hover interaction losses reduced from 11–18% (ARW19 problem flights) to 6.5–9% in comparable ARW38 sorties.
ARW19: FM = 0.62 ARW38: FM = 0.66 ↑6.5%
Control Authority
Rotor-Out Margin
ARW19 drove allocator saturation to 96.2% during rotor-out tests — requiring an architecture update. ARW38 achieved the same test with 1.2% saturation (engineering pass), demonstrating the improved 4×38 wrench-matrix allocation resolved the ARW19 saturation issue.
ARW19: 96.2% saturation ARW38: 1.2% saturation ↓
Acoustics
50 m Noise Level
ARW38 noise signature (84.0 dB(A) at 50 m) was higher than ARW19 (76.6 dB(A)), consistent with 4× greater disk loading. Both campaigns passed the noise flight test requirement. Tonal content above 75 dB(A) was noted in both vehicles as an open research item for ring-wing acoustic optimisation.
ARW19: 76.6 dB(A) ARW38: 84.0 dB(A) ↑ (higher mass)
Open Research Items
Forward Programme
Both campaigns identify high-priority research areas: propulsion–airframe interaction (PAI) CFD modelling, high-actuator-count control allocation ceiling (beyond 32 outputs), ring-wing tonal noise reduction, and forward-flight low-Re lift drop-off characterisation. Seeking university research collaboration partners.
Collaborate

Research Data

Dataset & Technical
Documentation

Telemetry
Per-Rotor ESC Telemetry
50 Hz vehicle state and 10 Hz per-rotor command, thrust, RPM, current, temperature, and CAN-bus status logs for all 81 sorties. ARW19 in PX4 ULog (.ulg), ARW38 in ArduPilot dataflash (.BIN) + MAVLink (.tlog) format.
Instrumentation
Ring-Mounted IMU Arrays
400 Hz IMU data, 50 Hz magnetometer, and 10 Hz GPS integrated from NED velocity. Engineer-annotated anomaly windows across all marginal and abort sorties — data rarely available publicly for high-rotor-count DEP aircraft.
Compliance
Part 21-Style Test Matrix
Full Part 21 / CS-23 compliance mapping for both campaigns, including target and exemption documentation for all altitude-capped sorties. TCCA Aircraft Certification basis (ACRA UEN 201919466C). Airworthiness Statement issued by ACUASI / University of Alaska Fairbanks.
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Research & Flight Test Collaboration

Active SBIR/STTR proposals with UC Berkeley HiPeRLab, LBNL, and Elodin Systems. Seeking CFD partners for PAI modelling, control-system researchers for high-actuator-count allocation, and institutions for Mitacs / NSERC co-funding.

Contact for Collaboration View Publications