The FAA has approved special operating conditions for the Boeing-Leonardo MH-139A Grey Wolf helicopter for the U.S. Air Force. The helicopter is based on the civil version of the Leonardo AW139 medium twin. This design feature incorporates a 2.5-minute all engines operating (AEO) power restricted for use at helicopter operating speeds below 60 knots indicated airspeed and hovering out of ground effect (HOGE).
This power is referred to as 2.5-minute HOGE utility power (HUP), which is greater than the transmission power limitations associated with takeoff and AEO. Use of the 2.5-minute HUP is not part of, or combined with, a takeoff operation.
In September 2020, Boeing applied for a supplemental type certificate (STC) for performance envelope expansion of the AW139. The AW139 helicopter as changed is a medium twin-engine 14 CFR part 29 transport category B helicopter with a 15,521 pounds mtow with seating for nine passengers and two crewmembers.
Last year, a senior USAF procurement officer said at a Senate hearing that the addition of defensive systems to the aircraft necessitated the granting of three STCs from the FAA. The granting of this latest STC paved the way for Boeing to deliver the first of four MH-139A Grey Wolf test helicopters to the USAF earlier this month.