The US Army has begun its search for a new “Block III” engine to power its enhanced Textron Systems RQ-7B Shadow UAV that is paired with the Boeing AH-64 Apache gunship in the scout role.

The second iteration of the RQ-7B, which began fielding in 2015 as the RQ-7Bv2, is weighed down by new mission equipment and air vehicle improvements and the existing piston engine built by UK firm UAV Engines cannot keep up. It was designed for a Shadow UAV with a gross takeoff weight of approximately 127kg (280lbs) but the aircraft has since grown closer to 209kg (460lbs), according to the army.

In a request for information (RFI) published this month, the army says it has a new requirement for a more powerful and reliable engine with an average failure rate above once every 1,000h.

Textron Systems RQ-7 Shadow. US Army image

US Army

“This propulsion system shall provide RQ-7Bv2 with a more reliable and lower life cycle cost system,” the notice states. “The system shall allow growth in aircraft weight while maintaining performance.”

According to a recent Q&A document, the army will consider all alternative propulsion systems including piston engines and small turbines. “This RFI is not restricted and does include turbine engines,” the notice states.

The army has previously said it intends to trial two competing engines before beginning procurement in “late 2017”. According to army budget documents for fiscal year 2017, the service plans to furnish 120 Block III engines.