Mark, would you mind explaining thoroughly how can technician get access to those areas of upper surface of wing skin which are not accessible from the access panels? Are they allowed to walk over the wing surface?
You can walk on the wing. Areas are clearly marked "No Step" that are not designed to hold significant weight.
Most wing access panels are below wing. Mechanics don't spend much time on top of the wing.
How much time are you around aircraft? In the cockpit, in the E&E compartment, wheel well, APU...... these places are visited often by working mechanics. It might be a good idea to get out with the guys working the aircraft. Grab some tools and join in. You'll have the basics down quickly.
A lot of these questions don't even enter the minds of working mechanics. We've all been around numerous types of aircraft.... this all comes naturally.
