If you put a lock in, thereís really no chance of damage to the TQ tube sitting on the ground. That said, everything wears out. And judging by the pilots Iíve seen flying around at 200 KIAS or more with the ball mostly displaced, or leaving the plane without a lock, who knows what else is going on, bent, or damaged. But I donít see where a plexi window will be worth it other that to marvel at some machinery. You canít really see sheared rivets in a torque tube.
Then there are the crappy repairs, etc. Take care of it and itís extremely reliable. Let a Gulfstream blow it hard over while youíre in the FBO drinking coffee and poof, $25k out the window.
For the first time in a long time, yesterday I started up with the lock in place. I was distracted after the fueler at Dolphin aviation walked around the plane 3 times trying to figure out where to fuel the plane. After we talked and found a screwdriver, I checked the caps, etc I was refreshing myself on auto start override as I hadnít used that in 15 years either. Got out of routine and forgot the external lock. Fortunately a customer was watching and came out to advise and helped me out by throwing it in the baggage. Embarrassing for sure, but I wouldnít have made it 10 feet without figuring it out as I move the pedals a lot when taxiing. Last time I did that I was in the Shrike and could duck out the back door to remove without shutting down. Anyway, reminded me that the only real way of a pilot can check for integrity of the TQ tube is to leave the external lock in place and push on the pedals.