What 's the procedure to restart the engines in mid-flight of an aircraft like ATR-72 which does n't have an APU and is started with GPU -LRB- external ground power unit -RRB- ?
`` Pre-flight Airplane Procedures : Why is the '' `` start engines '' '' sequence on a 737 -LRB- First start APU , wait for correct EGT , then electrical bus switch , etc -RRB- manual ? Could n't it be automated ? Is it similar on other planes -LRB- B767 , A320 -RRB- ? ''