An intake air duct serving as {HEAD ~ a passage} for supplying air to {TAIL ~ an engine}, the intake air duct comprising: 
An intake air duct serving as { HEAD ~ a passage } for supplying air to { TAIL ~ an engine } , the intake air duct comprising :
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH