An undeclared, unacknowledged alliance is emerging between Bell and Sikorsky as industry waits to find out how the US Army plans to address its Armed Aerial Scout (AAS) requirement to replace the OH-58D Kiowa Warrior. They want the same thing -- almost.
Bell wants the Army to take the upgraded OH-58F model, add new-build cabins and the uprated powerplant and dynamics from its Block II demonstrator and keep the Kiowa Warrior in service. Sikorsky wants to keep the Kiowa Warrior in service too, so it has time to develop its high-speed, coaxial-rotor S-97 X2 Raider to enter service in 2025. Bell wants to stay in the armed scout business: Sikorsky wants to launch its next-generation rotorcraft family.
S-97 Raider. (Concept: Sikorsky)
Bell's OH-58 Block II comes in two flavours. The first of two company-funded demonstrators, which flew on April 14, is powered by a 1,020shp Honeywell HTS900 and has a Bell 407 transmission and main rotor and Bell 429 tail rotor. It essentially recreates, dynamically, the cancelled ARH-70A armed reconnaissance helicopter that was to replace the OH-58D.
The second demonstrator will have a 12%-uprated version of the Rolls-Royce Model 250 engine now in the OH-58D, so the Army has a choice of engine. Both Block IIs will be used to demonstrated that an uprated OH-58 can meet the Army's "6k/95" hot-and-high performance requirement for the AAS -- the ability to hover out of ground effect at 6,000ft altitude on a 95F day.
OH-58 Block II. (Concept: Bell Helicopter)
When combined with the F-model cockpit and sensor upgrade and new-build cabins, the Block II is the lowest-cost, lowest risk way to meet the AAS requirement, Bell argues, keeping the Kiowa Warrior in service by following the well-worn model of remanufacturing the helicopters to increase capability and extend life.
Sikorsky, meanwhile, is building two S-97 Raider prototypes that will fly in 2014. If the Army awards a development contract in 2015, the company says, the aircraft could reach initial operational capability in 2025, the out-of-service date for the upgraded OH-58F. Raider would offer 220kt speed and "at least 10k/95" performance, Sikorsky says.
The fly in the ointment of this cunning, if uncoordinated, plan is the Army's avowed intent to field a next-generation replacement for the Black Hawk by 2030 under the Joint Multi-Role Medium program. This would have a speed of at least 200kt. But the Army will not have the budget to develop both that and a new-start AAS.
Sikorsky, not surprisingly, says replacing its UH-60M Black Hawk could wait until 2035, giving the Army the opportunity to cut its teeth on JMR technology by fielding it first on a smaller scale, and a smaller fleet, with AAS. We should find out the Army's take on how AAS and JMR will fit together over the next few months.
As for JMR Medium, Bell has teamed with V-22 partner Boeing to propose an advanced tiltrotor for the JMR technology demonstration. Speed will be at least 270kt, which means "Sikorsky will be in a race for second place," says CEO John Garrison.