Tristar engines
What GlueBall says is correct. Lockheed likely should have offered alternatives to the RB211-22, however once the bugs were ironed out the triple spool RB211 family have proved to be extremely reliable and fuel efficient. I know of more than one which remained "onwing" for more than 20000 hrs. Also, unlike the Douglas three holer, I don't ever recall a Tristar "shedding" an engine.