For those out there who like to emulate real world airline operations vs. "playing the video game", here's a topic that's been bugging me for a while so I did some research before writing this piece.

I have concluded that the FeelThere 'Call' checklist item (ERJ145) to start the APU while still on final approach is wrong.  Unless there is an inflight problem requiring aux power/bleed air, there is no reason to run the risk of an APU start fire when the airplane is in flight's most vulnerable situation (low and slow for landing) and the pilots are plenty busy enough with the approach/landing.  

Airlines that fly the ERJ145 tell pilots they would prefer the right engine continue to run at the gate until ground power is connected instead of starting the APU.  Fuel prices and maintenance costs are reasons behind this logic.  Furthermore, EUR airports are really strict about APU's running at the gate due to noise/air pollution.  

The ERJ has only one baggage/cargo door on the left side, so the ground crew can easily stay clear of the idling right engine as they hook up the ground power.  

In situations where the terminal has poor or no ground power available, start the APU on taxi in, NOT while in the air on final approach.  

While we are on the APU subject, what about start up/departure procedures?

In most commercial jet airliners, the normal start up procedures call for the APU to be shut down right after the main engines are running and stable.  

Some operators are asking pilots to taxi out on one engine with the APU supplying bleed air for cabin comfort.  This is more typical in busy major airport environments where long wait times/lines at the departure runway really eat up the fuel with both main engines running.  The second main engine start usually occurs about 5 minutes prior to takeoff so it is nice and warm before takeoff power is applied.  I think most of us sim pilots can disregard this policy as who wants to wait in line 20 minutes to fly a simulator?  I've been #5 in line with Ultimate Traffic II running pretty high and the line moves pretty quickly so I've got both engines up and running and the APU off as normal procedure dictates.    

Abnormal takeoff procedures (bleeds off) require the APU to continue to run supplying bleed air until about 1000 AGL.  APU shut down is part of the abnormal takeoff "after takeoff" checklist.  Also remember on APU start up to allow at least 2 minutes between start up and use of APU bleed air - or you run the risk of melting/damaging the turbine fan blades with fluctuating/high EGT.  

Happy Flying!