Originally Posted by
LOMCEVAK
One problem related to cockpit control checks is that some control surfaces are not visible from the cockpit, especially elevator and rudder trim tabs. The only way that you can then check these is during the pre-flight walkround having set full trim deflection first. However, this requires careful thought because the tab will deflect in the opposite direction to a control surface and will require you to go back to the cockpit to then set the opposite direction. Also, if an aircraft has a mechanically linked nosewheel steering system then full rudder checks can only be performed whilst taxiing and that is not the time to look over your shoulder at the rudder, which possibly you cannot see anyhow. So, there are a few practicalities which do require robust engineering procedures and pilot observations cannot always be used as a mitigation.
I believe that the above is much of the solution.
For light aircraft, I don't like checklists that say 'Controls.....Free'. The response should be free and correct. Admittedly, it is difficult to check the rudder on some aircraft like Pipers where you have to be moving but it is unlikely to be a fatal fault.
As for the 'correct' part of Free and Correct, that may have to be checked on the walkaround as mentioned in the quoted post. It is usually fairly simple to just reach into the cockpit and move the control column fore and aft while standing outside and looking at the tail.
As for the trim tab, it can be the same thing. For example on the C182 I flew the other day, I move the elevator tab to full nose down and see tab up. Then full nose up and see tab down. Now you have confirmed full trim movement and proper direction. Then I move the rudder trim tab a bit and check that the rudder pedals move in the proper direction. Doesn't take much time.
After a serious maintenance check, a more thorough flight control check must be done, especially in larger aircraft where visual checks are typically not done. It can be quite complicated in an aircraft like a 727 with number of slat panels versus flap selections combined with number of ailerons deflecting at different flap selections all needing to be taken into account.... and spoiler deflection differences as well. Of course a good post maintenance checklist using flight crew plugged into remote jacks and communicating with the cockpit while observing control movements should be used.
Checking maximum tab deflection angles with a protracter and comparing it to the type certificate is an interest thought. I suppose one could do that. If it were a typical flight school aircraft with others parked nearby, I might just make a comparison.
Best to be paranoid about this stuff.
I actually enjoy the walkaround(in good weather). The ones requiring the most detail in order to be considered reasonably thorough are........older biplanes. Got current on one recently that I hadn't flown in a few years. The instructor suggested an hour long walkaround for the first check of the day on that type. While I think I do it faster, he is not far off, in my opinion.