A quick glance up before startup in a PA28 will tell you precisely nothing.
A local A/D with an A/G service and parachuting which I frequent has the 'call for startup' rule when the paradropping a/c is in the air.
The Drop a/c has radio and the dropzone geezer on the ground are all on a/d frequency:
Start up will be approved while the drop a/c is climbing and the a/c self announces progress in the climb, time to drop etc.
Once the meatbombers have left the aeroplane no startup is allowed till all the canopies are down, which is announced by the dropzone chap.
It is simplicity itself to listen out on the back up Icom while all this is going on.........
Cusco