shakedown vs test flight

shakedown

noun
  • A trial or test period, especially of a ship or aircraft 

  • Extortion, especially through blackmail 

  • A thorough search; a frisk 

  • An improvised bed. 

adj
  • that tests the performance of a ship or aircraft 

test flight

noun
  • a proving flight; usually of a prototype of a new aircraft design before it goes into production. 

How often have the words shakedown and test flight occurred in a corpus of books? (source: Google Ngram Viewer )