USAF MH-139A defensive system holding up supplemental type certificate progress

A technical issue with a defensive system on the Boeing MH-139A Grey Wolf helicopter is preventing the US Air Force (USAF) from earning a supplemental type certificate (STC) for the aircraft.

The Boeing MH-139A Grey Wolf helicopter of the USAF. A technical issue with a defensive system on the aircraft is preventing the service from earning a supplemental type certificate (STC) for the platform. (US Air Force)

Lieutenant General Duke Richardson, military deputy, office of the assistant secretary for acquisition, technology, and logistics (AT&L), told a Senate panel on 22 June that this defensive system, which he said has a nacelle around it, is causing unusual air disturbances that the USAF is working to understand so it can be granted the STC. He did not provide further details about this defensive system. Boeing and the USAF did not return requests for comment prior to publication.

Lt Gen Richardson said the MH-139A needs three STCs. One has been approved, he said, while the other two are behind schedule.

An STC is a type certificate issued when an applicant has received US Federal Aviation Administration (FAA) approval to modify an aeronautical product from its original design. The FAA needs to certify the AgustaWestland AW139, the European version of the MH-139A, for flight with use of military equipment. This is important because the USAF and FAA want to ensure that modifications or changes to the AW139 will not interfere with equipment that could cause safety of flight issues.

“It is not necessarily that the FAA is being slow or anything,” Lt Gen Richardson said. “It is really just trying to work through those technical issues.”