In a False Claims Act lawsuit filed in federal court in Milwaukee, Wisconsin, a whistleblower has charged Derco Aerospace Inc., a United Technologies Sikorsky unit, with overcharging the government nearly $50 million on aircraft parts.

The whistleblower — Mary Patzer — filed the lawsuit in June 2011.

Patzer is a former Derco assistant controller.

This week, the government intervened against Sikorsky and Derco.

The Justice Department said it will file its own complaint in the case within 60 days.

Patzer alleged that the companies were submitting bills to the federal government with an illegal 20 percent markup.

Patzer alleges that she raised her concerns with the illegal markup with her supervisors who were “unresponsive” to her concerns.

Patzer then went up to Sikorsky’s federal government accounting manager, Dawn Kawtucki.

“Almost immediately after exposing the non-compliance issues to Kawtucki, Patzer was terminated,” the lawsuit alleged. “Derco informed Patzer that her position had been eliminated due to a ‘reduction in force’ on or around September 30, 2010.”

Patzer alleges that her position was assigned to an employee who had “little or no experience with government military contracts.”

And she alleges that in fact she was fired for blowing the whistle on the illegal 20 percent markup.