Boom 16 has {HEAD ~ first and second arms} 20, 22 wherein second arm 22 is shorter than {TAIL ~ first arm} 20 
Boom 16 has { HEAD ~ first and second arms } 20 , 22 wherein second arm 22 is shorter than { TAIL ~ first arm } 20
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH