In Afghanistan, Boeing AH-64 Apache and Sikorsky UH-60 Black Hawk helicopters encountered a problem their designers never anticipated. Hovering at 4,000ft in 35°C (95°F) conditions had always seemed sufficient performance for a helicopter. But Afghanistan’s mountains and hot summer raised the bar for hot-weather hovering by 2,000ft.

Even so, GE Aviation could have supplied more powerful versions of the trusty 2,000shp- (1,490kW-) class T700 engine, the trusty turboshaft that has powered both helicopters since the 1970s.

But the army was not interested. If the service was going to launch a re-enginging programme for about 2,135 UH-60s and 690 AH-64s, it was going to demand something else for its investment: a 25% reduction in specific fuel consumption, while increasing thrust by roughly 25-30% within the same footprint of a T700.

Thus, the improved turbine engine programme (ITEP) was born – the largest engine development now under way by the Department of Defense (DOD). The competition for the next phase of the 3,000shp-class propulsion system began in September. The army plans to select up to two bidders early next year to deliver a preliminary design with technical data in 2018. A single bidder will then be selected to start developing the engine, with the ITEP powerplant entering the fleet beginning with the UH-60 in the early 2020s.

Opportunities of this size in the rotorcraft market come around very rarely, so the army is expecting robust competition. In addition to the rival GE Aviation GE3000 and Honeywell-Pratt & Whitney HPW3000, army officials also say they expect additional bidders. Among the likely candidates, Rolls-Royce has already declined to participate. Assuming the Russian Klimov TV7-117V is ineligible, that leaves only Turbomeca.

The French engine manufacturer began tests of its Tech 3000 demonstrator programme earlier this year, promising to lower specific fuel consumption in a new 3,000shp-class engine by 25%. Aside from a clear demand from the civil sector, it appears aimed at replacing the RTM322 engine that today powers the NH Industries NH90, the AgustaWestland EH101 and the Westland Apache AH1 attack helicopter – the UK army’s version of the AH-64.

Little else is known about the Tech 3000, save for plans to certificate the engine by the end of the decade, and Turbomeca declines to say whether it will respond to the army’s RFP for the ITEP preliminary design phase.

Among the known bidders, the competition reveals a clear split in design philosophy. The Honeywell-Pratt & Whitney joint venture, called ATEC, features a two-spool engine design. The GE3000, as with the T700, is based on a single-spool architecture.

According to Honeywell, the twin-spool offers an inherent 3-4% reduction in specific fuel consumption, but dividing the pressure and thermal loads carried by each spool. It is also better suited to handling future thrust growth, as the army wants the ITEP design capable of reaching 3,750shp without major changes.

However, GE answers that the single-spool architecture can easily accommodate higher thrust requirements, as the company’s single-shaft GE38 engine in the 7,500shp power class attests. The single-shaft also offers the advantage of simplicity with fewer parts than a dual-spool system.

The axial-centrifugal compressor for the GE3000 has already demonstrated the highest overall pressure ratio (OPR) among any of the company’s gas turbine engines, including the 27:1 OPR planned for the massive GE9X for the Boeing 777X. The engine also features heat-resistant ceramic matrix composites in non-rotating parts, reducing cooling requirements to obtain better fuel efficiency.