Cross-Talk between Altitude Changes and Speed Control during Simulated Low-Altitude Flight

Simulations of flight over a planar environment create an ambiguous optical stimulus in which changes in altitude can potentially induce inappropriate control of speed. Previous research has shown that changes in altitude produce changes in global optical flow rate that lead to erroneous judgments of speed and increased RMS error in speed control. However, from these studies it is unclear whether erroneous speed control was directly due to misperceiving changes in altitude as changes in speed or simply a response to more complex optical flow masking the optical effects of speed changes. Our experiment used a speed maintenance task during simulated flight over a planar surface to examine the effect of changes in altitude on control of speed. We found that power in participants' speed control input increased at the specific frequencies of the simulated altitude changes relative to power at those same frequencies when no altitude disturbance was present. These results clearly show that controllers respond to...