I can't speak too much to the detail of an autopilot flight test. I've done quite a few, but just the basic checks of all of the functions. There are certainly characteristics to be checked, with which I am l not familiar. Your avionics tech will know, and advise you.
I did several autopilot test fligths on a Bellanca Viking last summer, and due to a defect in the autopilot, the plane would happily roll inverted, which I cautiously let it do, just to get the attention of the disbelieving avionics tech I was carrying. For this reason, I always make sure that I know how to rapidly disconnect the autopilot, and confirm that this function works early in the flight. I also make sure I have good visual reference to the ground.
On the subject of Cessna 303, I shall offer the following record I made of a very unusual experience I had while flying one Transatlantic. Check the function of your deicing system!
Pilot DAR
Bill and I were ferrying a Cessna 303 from Canada to England, for delivery to it’s new owner. With lots of Cessna 310 and 340 experience, I felt extremely comfortable flying the 303, and off we went. This particular aircraft was very well equipped, with full IFR equipment as one would expect, and full known icing equipment. So there we were, flying in IMC, though often with a view of the ground, but picking up ice. No problem, I just selected on all of the deicing equipment, and had a look around the aircraft to assure that is was functioning. The boots on the wings, and just the very tips of the horizontal stabilizer could be seen, and I was able to confirm that they were operating as expected. Obviously, the boot on the vertical fin could not bee seen, and this was an act of faith.
After a while, and while obviously picking up some ice, a slight twitch in the yaw axis developed. It was about what you’d feel if you were alternatively pushing the pedals a little. I looked over at Bill’s knees, and asked, “Are you playing on the pedals down there?” But as I asked, I observed that his knees were still, so this was not his doing. Next I scanned the engine instruments – they indicated that the engines were both purring. The twitching in yaw got a little worse, and was now noticeable in pitch as well. Whatever it was that causing the twitching was making be nervous. When I’m nervous, I like to be closer to maneuvering speed (Va), in case something unexpected happens. So, I pulled the power back, and began to slow down…
As the plane slowed, we were suddenly rodeo riders, the plane was yawing and pitching violently, though roll control was prefect the whole time. Yaw was ten degrees either side uncontrollably, and pitch, though harder to estimate, was enough to give us quite a variation in “G”. Whatever the problem, slowing down made it a lot worse, so I sped up, and it settled down. The only thing it could be was airframe ice, nothing else would seem to have changed since we took off. But this was a known icing certified aircraft! So I flew as fast as I could, knowing that whatever it was, was getting worse, and we were still in the ice. At the higher speed, anything bad which happened, would happen worse, and faster! I had to get out of the ice.
We were able to descend, flying up the valleys in the mountains, not far from Wabush, Labrador. We were lucky enough to find warmer air, and the ice slowly shed on it’s own. An hour or so later, I landed in Shefferville, Quebec for fuel. Of course, slowing down, was an exercise in extreme caution. But the plane handled perfectly. The after landing visual inspection revealed no ice, or other defects at all. Mystery… Our trip continued….
Bill was flying the leg from Iceland to Scotland. I was bored. Searching for some new stimulus, I found the previously unread flight manual for the aircraft, and browsed. Among the commonly found white pages, was an uncommon fluorescent red one. To it’s corner, stapled a tiny zip lock bag, which contained a placard. My interest was peaked now (better late than never). The information on the page instructed that flight into known icing conditions was prohibited, and at the first encounter, an immediate 180 degree turn was to be executed. The placard in the zip bag simply said “Flight in icing conditions prohibited”. Well that was clear! But, with the placard in the bag, and the bag in the book, and the book in the glovebox, the pilot (who had not bothered to read the book prior to flying) had no way of knowing! To read on, it turns out that because the Cessna 303 has a “crucifix” tail, meaning the horizontal stabilizer is mid way up the vertical stabilizer, their respective leading edges form a cross. The middle of this cross was not deiced, and thus a block of ice would form there, and disrupt the smooth airflow over the tail. The result was (in several cases) fatal inflight breakup of the aircraft, due to loss of pitch and yaw control. This, I could imagine! This flight manual page, and placard were required by airworthiness directive 86-01-01.
The final instruction on the page was to install the placard. I did.
I understand that soon an electric pad was developed for installation on the offending leading edges, to correct this design deficiency.
I learned from that to read the flight manual before flying. I don’t know how close we came to breaking that plane up in flight, but it was a lot closer than we should have come!