I think altitude dependence is a red herring. I’m convinced that the corrugated ducting just creates enough drag to slow down the air so that there is not enough airflow to activate the sail switch.
Seems like drag must be a factor, but still seems like altitude could be a contributing factor as well.
At sea level, airflow would be reduced by drag from the duct. At higher altitudes, airflow would still be reduced by drag from the duct -- but it would also be reduced by the lower density of the flowing air. So there would be reduced airflow in both cases, but the combined effect would be more severe at higher elevations.
Edited by Yonder37, 26 November 2023 - 05:12 AM.