Generally speaking, pilots are restricted to relatively simple maintenance tasks such as changing a spark plug, changing a wheel or replacing a blown navigation light bulb etc.
really.......... and when is changing a "spark plug" simple? A lot of pilots wouldnt know how to open a cowl on a more complex aircraft. Thats if they had to tools to do such a job just floating in the hold
Changing a wheel is simple as well? Where are they getting the spare wheel from? The jack, the torque wrench the splut pins..... or do they just float around in holds of aircraft as and when the pilot decides to fix it....