The present invention is in the technical field of auxiliary power units and {HEAD ~ emergency power units} for {TAIL ~ aircraft} 
for
The present invention is in the technical field of auxiliary power units and { HEAD ~ emergency power units } for { TAIL ~ aircraft }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL