woxman and PIOs
Often referred to as JCs - why - well one of the first to be a victim of a severe PIO was a TP flying an F86 Sabre at high IAS. Sabre was one of first fighters with powered flying controls but it only had spring feel. You could only feel IAS by the amount of stick movement made to produce a result.
It just happened that above about 400 Kts if one flew through a gust disturbance causing the aircraft to pitch a little then the pilot's hand/arm on the stick acts like a bob weight and the pitch of the aircraft is enough to input a pitch demand opposite to what the aircraft is doing. This causes the aircraft to pitch the other way and one rapidly has a runaway condition with the aircraft pitching up and down whilst ever the pilot hangs on to the stick.
Experiencing this unexpectedly caused the hapless F86 TP to yell over an open microphone/radio "Jesus Christ" as a prayer in his moment of need!
Hence the derivation of JC/PIO.
My first was also in an F86 at 500 Kts at 500 ft and I had my left arm down beside the ejection seat. 5/6 large excursion in pitch almost broke my arm as I was projected violently up and down before letting the stick go to break the feedback loop. My next was also in an F86 in a dive on a target at low level attempting to fire 2 30mm cannons with negative g applied. Might have called more than JC but only way to break the sequence then was to haul back hard on the stick.
Next was just after lift off in the first Folland Gnat having a full slab tail plane. It was developmental and a known problem being sorted. My PIO was triggered by the gear retraction and the transient trim change nose up as the nose wheel/speed brake retracted. I instinctively corrected nose down and set the PIO going. Once again broke the feedback loop by a hard pull on the stick but had a few big views of the runway in very short time.
Most PIOs/JCs are divergent and can guarantee a wild ride unless you break the loop quickly.
I would expect that FBW computers have PIO damping. Anyone know?
Was surprised to see mention of PIOs in some helicopter control systems.
Any helicopter pilot care to describe situations where they occur and what you do about it before it beats you into bits and pieces of flying blades.?