Weather and Flight Experience
One day in March 1944 I was flying my Spitfire from Italy toward our base on Corsica. I was alone and it was late in the day. The sky was overcast and gray, as was the sea surface below, so my horizon was marginal. But I had no worries about my situation, and was not paying attention to the instruments. Suddenly, a change of air and engine noise told me something was wrong. I looked at my instruments and they showed my plane was in a diving turn. My reaction was, "those instruments can't be right!" but knew immediately that they were right and that I had to rely on them to get out of the dive. I was at about 6,000 feet and had sufficient altitude to recover using the needle-ball-airspeed instrument technique. I had been an instructor in AT 6s for about a year and a half after graduation and I got much instrument and link-trainer time. I became fully competent in the needle-ball-airspeed technique, so I never used the artificial horizon, because it's gyro would tumble if you made a steep turn. Incidentally, the Spitfire, instead of a ball to show skidding or slipping, had a second needle, pointing downward below the turn needle.
I probably lost my horizon after flying into haze, or a region of uniform color and brightness. If I had flown into cloud I would have known that I had lost my horizon and had to go on instruments in order to stay oriented and in control. If I had been unable to fly on instruments I would have become disoriented, a condition called pilot vertigo, and I would have had to bail out or crash with the plane. But I didn't suffer vertigo because I was not aware that I had lost my horizon, orientation, and control of the plane. It then wandered and went into a spiral dive producing the noises that alerted me.
I recalled this experience in July 1999 when John F. Kennedy, Jr's plane crashed. It was very clear to me, from the radar records of his plane's behavior, that the same thing happened to him.