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After years at Cessna , he spent one year working on the certification of the Umbaugh U-17 and years at McCulloch Aircraft Corporation performing design studies on inexpensive rotorcraft .
 Cessna, McCulloch Aircraft Corporation
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Cessna, McCulloch Aircraft Corporation