Amazing the stuff we find to talk about on a wet Sunday afternoon
Keith
Well you have tidied up a fair bit of theory there!
In point of fact the practice of checking the spiral stability of an aircraft in the sky can present quite a good gotcha to young lads (and lasses).
At one stage I used to take Kinston Aero Eng Uni students up three at a time in a PA44 to show them some of the practical reality of flight test issues. The spiral stab bit used to go like this
Q: “OK – how do we see if this thing is spirally stable or not?”
A: “Trim it out S&L, roll on 30 deg of bank, let go the controls and observe”
So that’s what we did. 30 secs after abandoning the controls and approaching Vne at 70 deg of bank, the view of the crew was that it was unstable in the spiral mode.
Recover, explain flight test results not worth a damn unless they are repeatable.
Repeat test. Same result. Remark “Hey, tell you what, lets try that one more time”
Repeat test. This time it rolls wings level.
So what is going on?
Any comments Keith?
Regards