First throttle chop I ever had was sprung on me, unbriefed, by the factory test pilot at Torrance ten years ago; as a low-time UK-based pilot I'd never even HEARD of such a thing. And yes, I sat there like an idiot with my thumb in my mouth thinking, now what's it doing? while the horn blared and the nose went off on its own. Taught me a lot - firstly, that's what it looks like, and you know what you have to do. But also, it must have been three seconds after the chop before I did the right thing, and the factory pilot didn't have to intervene. Thank you Mr D Tompkins (just looked it up) for the most valuable four seconds flying I ever did.