US Army continues search for better scout helicopter

20/04/11 By Stephen Trimble Flight International

The US Army's search for a more capable armed scout helicopter continues, but most of the signs are pointing back to an improved version of the Bell OH-58D Kiowa Warrior.

Since the cancellation of the Bell ARH-70 Arapaho in 2008, the army aviation branch has committed to spend more than $1.3 billion to modernise the OH-58D at the same as it considers a wide range of alternatives for replacing the venerable type.

An analysis of alternatives has considered options ranging from launching the high-speed Sikorsky S-97 Raider, pursuing the conventional EADS North America AAS-72X and Boeing AH-6S Phoenix, settling for a modernised OH-58D or gambling on an AVX concept for an OH-58 cabin with a coaxial rotor and dual-ducted fan.

The analysis has been delivered to the army's leadership, but no decision has been reached. Nor has a date been set for briefing Ashton Carter, under secretary of defence for acquisition, technology and logistics, on the army's recommended course of action, says Lt Col Bob Grigsby, programme manger for the army's armed scout.

As the army leadership continues to ponder the options, the OH-58 programme is gaining momentum inside the army's budget documents, with three separate tracks to preserve and extend the Kiowa Warrior fleet until 2025 already in place.

First, the army is taking 39 OH-58As out of storage and converting their cabins to the D-model standard, with another 40 retired OH-58As still available, Grigsby says. The converted OH-58Ds will help reduce a shortfall of aircraft, while the army is also considering relaunching production.

The army is also modernising other OH-58Ds to an F-model standard under the cockpit and sensor upgrade programme, which adds a nose-mounted sensor, glass cockpit displays and improved avionics.

Finally, Bell has flown a "Block II" version of the Kiowa Warrior with a 1,020shp (760kW) Honeywell HTS900-2 engine, which provides a path to overcoming the OH-58's inability to hover at 6,000ft (1,830m) when temperatures are above 35°C (95°F) - also known as the "6K/95" standard.

Alternatives to the Kiowa Warrior could face a difficult challenge. Army aviation leaders have set an "aimpoint" for delivering a next-generation aircraft with high-speed capability for 2030, which seems to remove the S-97 from consideration from an immediate OH-58 programme.

By comparison, EADS and Boeing's proposals based on off-the-shelf, conventional helicopters may be more attractive. EADS, for example, says the twin-engined AAS-72X, a modified version of the Eurocopter EC145, can be delivered at the same price and within the same timeframe as the roughly $4.5 million price tag for the OH-58F upgrades, but with 6K/95 performance as standard with no need for a re-engining.