A SF-340 Captain reported that the standard operating practice of getting the flight crew attention by banging on the aircraft cabin to pass paperwork in during engine starts is very distracting. The practice caused the loss of attention to the details of the engine start process.

Narrative

I believe this to be a huge safety operational issue concerning ground operations on the Saab. This is a system wide issue occurring mostly at outstations. This incident just happens to take place at ZZZ. We had about a twenty minute turn this afternoon. We ran all appropriate checklists up to and finishing with the starting engine checklist. After getting the sign for two; I began to start the right engine. As the engine was being started I heard a loud bang noise coming from near the whisky hatch. Now; from being on the Saab for years; I know it has become a practice for station agents to bang on the aircraft to pass paperwork through the hatch. This practice is completely unacceptable. First; both my hands and my attention should be on starting the engine; not on wondering what the banging noise is. Nor shall I be receiving any paperwork during an engine start. After the first bang a second louder bang came from near the whisky hatch. I ignored the bang again; but became slightly distracted and irritated. After about ten more seconds I heard an even louder bang followed by someone yelling. I had not even finished the start and already had three loud slaps on the aircraft followed by a yell. How am I supposed to know whether the station wants me to discontinue the start for some reason; or worse they are trying to get my attention because of a fire? This practice is dangerous and I think it should be addressed. After completing the starts of both engines; and taxiing away; I called the operations frequency to discuss this matter with them. After sensing the lack of care in what I had to tell them about this issue; I was further irritated. This issue continued on my mind for the duration of the flight and the rest of my day. I feel that the station personnel here; and many outstations need to be trained that we need to know where everyone is at all times when the engines are running and we don't need an unnecessary banging and or distractions especially during engine starts. As an answer to slapping the side of the aircraft to get our attention; why couldn't we train ramp personnel to go to the front of the aircraft; where the ramp guy is starting us; and wait till the start is finished. Then once they have our attention; then approach the aircraft and pass any paperwork through the hatch. This station did not seem to care what I had to say; and this practice will go on and on and someone will either get hurt or aircraft will be damaged.