Pilot 101: Pilot Induced Oscillation aka PIO

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DaSH PA at Half Moon Bay Airport

Happy National Aviation Day! In recognition of the day, the HPA Notebook is introducing a new series of posts, Pilot 101.  This recurring series will examine flying challenges that pilots of HPAs often encounter.  

This week's topic is pilot induced oscillations, most often referred to as PIOs.   These oscillations occur when a pilot inputs a series of overcorrections in opposite directions, each input intended to correct the previous one.  The diverging sinus-wave flight pattern that results is very common with first-time HPA pilots as most HPAs are very pitch sensitive.  Pilots riding the roller coaster of PIOs should let up on the controls and allow the HPA to level out and essentially fly itself.  

 Other factors that can feed into and exacerbate PIOs are lags in the control system and pitch variations due to changing pedaling cadence, which most HPAs experience to some degree.

In the top video, the maiden flight of DaSH PA (Dead Simple Human Powered Airplane), pilot Alec Proudfoot has a series of PIOs early on, but as a seasoned pilot, he recognizes the PIOs, and lets up on the controls.  As a result, the HPA levels out in flight.  In the video below, Airglow takes a hard landing as a result of PIOs that did not come under the pilot's control.  
Airglow at 2018 BHPFC Icarus Cup

Pilot 101 tip: Remember that HPAs are pitch sensitive and keep pitch inputs light -- if pitch trim is available, fly pitch mostly with trim. Keep your view on the horizon and aim to keep pedaling input as steady as possible.



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