General Electric has started preliminary testing of the improved T700-701D turboshaft for the Sikorsky UH-60M Black Hawk helicopter. The US Army will be watching as it considers upgrading the Boeing AH-64A/D Apache's powerplant to the same standard.

"After one year of development, we have the first engine in test and several tests are already completed. We're also on track to deliver the first three engine shipsets in December to support flight testing and we're well on our way to qualifying the first T700-701D by mid-next year," says Scott Reed, GE director of military programmes.

From 2004, the US Army is planning to upgrade to UH-60M standards 1,217 Black Hawks, the vast bulk of which are UH-60As powered by the older 1,160kW (1,560shp) T700-700, while some will be UH-60Ls with the 1,400kW T700-701C. The T700-701D will be rated at 1,500kW and offer extended durability. "Preliminary tests have shown good results with less deterioration than allowed for under the specifications," says Reed.

Apache operators are less interested in the additional power and more in savings from reduced maintenance requirements and more spares commonality with the UH-60M. The army does not have enough T700-701Cs to power its growing fleet of radar-equipped AH-64Ds and has been forced to swap engines on the lighter AH-64A and non-radar equipped AH-64Ds for less powerful -701s.

Rather than upgrade T700-701s to the -701C standard, the army is looking at uprating the entire fleet to the -701D as part of a proposed Block 3 upgrade to the AH-64 starting in 2004. While the UH-60L has already been fitted with an uprated 2,530kW gearbox, the transmission on the Apache would need to be upgraded to take advantage of the additional power and a planned fifth main rotor blade.

The improved engine incorporates a new combustor liner, material changes to the first and second stage blades, similar to the CT7-8 powering the Sikorsky S-92, along with cooling modifications to the power turbine third stage, stator nozzles and shroud.

Source: Flight International