My pet peeve is the seemingly widespread belief that small aircraft are built of armour plate
Too often I see pilots smashing the controls back and forth on the walk around, slamming the door with a 100 lbs of force and mashing all the engine controls like they were operating a steam locomotive. The idea of being gentle and smooth to the device that can kill you seems to have been deleted from the QFI curiculum.
One of the earlier posters mentioned the mixture control. This is a personal sore point. Unfortunately an all too common scenario is repeated with many PPL's I fly with.
On the runup the engine mixture is abruptly pulled full out, the engine emits a strangled cough like the last weeze of a murder victim, where upon the pilot rams the mixture full in and the poor engine roars to life after clearing its throat with a nice back fire
. For the rest of the flight the mixture stays fully in because there instructor told them "bad" things could happen to the engine if it is leaned below 5000 feet
How come the correct way to do a runup mixture check and sensible leaning practices are so uncommon
