Why do you have to open the pneumatic crossfeed valves to de-ice the wings? Exactly what does the AC bus cross-tie switch do? And why do the engines only draw fuel from the center tank when all the fuel booster pumps are on? The key to understanding these and many other aspects of your aircraft is studying the schematic drawings for the various aircraft systems. That may sound a little bit dry, but to help you out I have included a Schematics section in the DC-9 Classic Flight Center that gives you live interactive schematic drawings.
Stepping into the cockpit of an advanced aircraft for the first time trying to learn how to fly it with nothing to help you out but a manual, or maybe a good tutorial if you’re lucky, can be quite a daunting task.
If you are an experienced simmer the general knowledge of how aircraft work will go a long way, but you’re still going to have your work cut out for you trying to learn a new aircraft. If you are a newer simmer, you may be in for an extremely steep learning curve.
The DC-9 is equipped with the Sperry SP-50 Automatic Flight Control System (AFCS), which is a gyroscopically controlled electromechanical system. The DC-9 is an old school aircraft and the autopilot installed in this aircraft is very much old school too. If you are used to flying with modern autopilots, you will find that this autopilot works a bit differently than the other autopilots you may be familiar with.