Flight-Testing a Fruit-Fly Connectome as an Aircraft Yaw Damper

Flight-control laws are assessed by their frequency response, stability margins, gust rejection and behaviour under failure; connectome-derived controllers have so far been shown mainly in time-domain demonstrations. We applied these tests to a spiking model of the fruit fly's visual yaw pathway, a 20,556-neuron FlyWire subcircuit from the T4/T5 motion detectors to the descending neuron DNa02, with the aircraft's yaw rate imposed directly as the firing rate of artificial T4/T5 sources, and compared it with rewired copies and a classical yaw damper. Under sinusoidal yaw, the right-minus-left DNa02 firing rate followed the yaw rate with coherence 0.98 at 1 Hz and with the stabilizing sign. It ranked first against 19 degree-preserving rewirings (median 0.31; p = 0.05) and narrowly first against 19 cell-type-preserving rewirings, which leave every input to the HS, VS, H2 and DNa02 cells unchanged. Closed around the rudder of a simulated six-degree-of-freedom Cessna 172 in moderate turbulence and tuned under the same margin rule as the yaw damper, it reduced RMS yaw rate by 19%, against 57% for the damper. Of 11 wirings it had the lowest RMS yaw rate and the lowest RMS sideslip on both aircraft models. The three rewired controllers that came closest on yaw rate in the Cessna model were saturated relays flying skidding turns. No lesion-study flight departed, so the pre-specified departure test could not separate the wirings; under random neuron loss the real wiring's mean RMS yaw rate rose toward the bare airframe's but not above it, partly because the loss often silenced its one active readout neuron, and silencing its six HS cells returned it to the bare airframe's yaw rate. Flight-control tests can therefore measure what a connectome's wiring contributes to a controller, and they expose failure modes, such as relay-like skidding, that a single performance score hides.