When three nuclear protestors broke into the E-9 Minuteman launch site in rural North Dakota on 20 June 2006, alarm bells rang all over the US Air Force.

Terrorists may have tried harder to gain access to the missile silo. But these trespassers were dressed as clowns, and merely spray-painted slogans around the site. Finished with their work, they waited patiently inside the launch site with hands raised until a helicopter-borne USAF security force arrived to arrest them.

Within the air force, however, the incident underscored the need to replace an ageing, under-powered fleet of 62 Bell UH-1Ns charged with responding to such alarms across vast distances.

The USAF's unguarded, remote missile sites dotting the Great Plains have always been vulnerable to potentially catastrophic security breaches, and the trio of harmless clowns only seemed to mock that risk.

Minuteman Nuclear silo - North Dakota
 © US Air Force
 Minuteman nuclear launch silo, North Dakota

A more high-profile security lapse in 2007, when a Boeing B-52 inadvertently transported six nuclear-tipped missiles across the country, drove sweeping reforms of the USAF nuclear enterprise. But it has taken five more years and a controversy over acquisition strategy to address the UH-1N replacement issue.

On 27 May, the USAF finally launched a competitive bidding process for 93 helicopters, releasing a draft request for proposals under the common vertical lift support platform (CVLSP) programme.

Recognising the scale of the need if not the urgency, the USAF's draft requirements call for a very different kind of helicopter than the 4,700kg (10,400lb)-class UH-1N.

For the most challenging profile - responding to a security breach at a missile launch site - the aircraft with four crew members must transport a nine-member security force with all of their weapons and other equipment a minimum of 210km (115nm) and back, with multiple stops en route.

The five most likely helicopters competing for the CVLSP contract are at least 50% larger than the UH-1N, ranging from the 6,800kg AgustaWestland AW139 to the 22,700kg Boeing HH-47. Falling in between are the Bell UH-1Y, Sikorsky UH-60M and the Eurocopter EC725 offered by EADS North America.

The USAF's demands for increased performance may yet force some competitors to switch to an even larger aircraft.

"We don't see any requirement that we don't meet with a government off-the-shelf UH-60M aircraft," said Tim Healy, Sikorsky's director of air force business development. But he added: "It isn't a cakewalk, but we do meet all the requirements we see so far."

US Air Force UH-1N
 © US Air Force

Until now, the USAF has released only the aircraft requirements, but not the acquisition strategy. Until it divulges how the requirements will be scored in an evaluation, most competitors are keeping their options open.

AgustaWestland, Boeing and EADS confirmed interest in competing for the contract, but declined to specify which aircraft could be proposed. AgustaWestland has the option of choosing between the AW139 and larger AW101, while EADS is balancing potential bids based on Eurocopter's EC725 Cougar or AS532 Puma.

Boeing's only option appears to be the HH-47 Chinook, unless it teams with Bell to offer the V-22 tiltrotor. However, the USAF has not expressed any interest in a high-speed aircraft, with its draft requirement documents calling for a minimum speed of 135kt (250km/h). While 30% faster than the UH-1N, this is less than half the top speed of the V-22.

In addition, Bell seems concentrated on offering the UH-1Y for the CVLSP contract, describing the far more powerful and updated version of the Huey airframe as the "best value" in the competition.

The competitors' strategies are likely to take shape after 10 June, when the USAF is expected to reveal the acquisition strategy for CVLSP during a closed-door "industry day" meeting.

The competitive strategy has already survived an attempt within the USAF to at least consider awarding a sole-source deal to the UH-60M. In late March, USAF acquisition officials rejected the sole-source option in favour of a competitive bidding process.

Source: Flight International