PORTLAND, Ore. (AP) — Defense contractor Precision Castparts Corp. said on Monday that it has agreed to buy Synchronous Aerospace Group, which makes mechanical assemblies for commercial and military planes.

Precision Castparts said it was paying an undisclosed amount in the cash deal. It said the deal should close by the end of December and would add immediately to earnings.

Synchronous makes flight controls, wing ribs, bulkheads, and other airplane parts. It employs about 700 people in Santa Ana, Calif., where it has its headquarters, and in Kent, Wash., Wichita, Kan., and Tulsa, Okla. It is a portfolio company of the private investment firm Littlejohn & Co. of Greenwich, Conn.,

Precision Castparts Chairman and CEO Mark Donegan said it was “another tuck-in acquisition that will make a strong contribution as we continue to expand our aerostructures capabilities.” He also said that Precision Castparts will be able to handle some functions that Synchronous had previously had to buy from other companies, such as fasteners (which include bolts and rivets) and metal forging and casting work.

Sterne Agee analysts Peter Arment and Josh W. Sullivan noted that this is fifth recent deal, and the fourth time this year, where Precision Castparts has bought an aerospace supplier. Previous deals included McSwain, Centra, Klune, and Primus.

Shares of Precision Castparts fell $1.25 to $178.09 in afternoon trading. Its shares peaked for the past year at $182.40 two weeks ago. They fell as low as $150.53 in early August.