The Brooklyn Navy Yard is turning out to be a hot ticket for small businesses. Seven new leases were signed at the Fort Greene spot, which is currently undergoing a $16.5 million restoration project for some of its structures, including Building 92 at 63 Flushing Avenue. Atair Aerospace, an engineering research and development company, and a green custom furniture designer are among the 38 businesses that have signed leases at the yard so far this year. Inexpensive rent, which Brownstoner estimates is around $10 cheaper per square foot than comparable space in nearby Dumbo, is named as a key reason for the high leasing activity.