Boeing and Leonardo Helicopters, along with their rotorcraft competitors, are baffled by the US Air Force’s requirements for the UH-1N Huey replacement programme but are pressing ahead with a bid based on the MH-139, a militarised version of the commercial AW139 medium-twin.

From Boeing’s perspective, the protracted Huey replacement programme is playing out like a repeat of the cancelled Common Vertical Lift Support Platform programme, with one mission set driving high speed, endurance and payload requirements.

The air force has hung onto stringent requirements set out in the CVLSP programme, including the ability for the helicopter to hover at 6,000ft in temperatures up to 35°C (95°F), but the helicopter industry has struggled to meet those standards, JD Clem, Leonardo helicopter division USAF director, told reporters this week at Leonardo’s AW139 facility in Philadelphia, Pennsylvania. Still, the service has not given up on requirements they set out years ago in CVLSP, he adds.

“I know that some of the requirements are the same that they were then and some of them I scratch my head on,” he says. “But they seem very reluctant to re-engage the process to try and redefine what those requirements are and justify them at this point...All I can say is, I’m not gonna throw a rock at them, they have a set of requirements they passionately believe in and they think they require all that stuff.”

Today, a fleet of UH-1Ns defend the USAF’s Minuteman III missile silos and fulfills a continuity of government mission. Most of the air force’s nuclear silos are scattered over North Dakota and Montana.

An industry day set for 8 May may help clarify the air force's timing and requirements for the UH-1N replacement.

“The acquisition transition has moved from this continuum of best value approaches...back toward something that has more of a developmental feel,” Rick Lemaster, director tiltrotor business development at Boeing, says this week. “I don’t know why they did what they did. That’s what we’re looking to do at industry day is understand the rationale in what they’re looking to accomplish.”

As Boeing and Leonardo attempt to navigate the tricky waters of US defence acquisition, they’re also waging an aggressive media blitz in the Huey replacement competition. After a technical glitch grounded a March media flight, the MH-139 took off with reporters this week over Philadelphia. With ominous grey skies dissipating just long enough for the 20min flight, the MH-139 powered up its two Pratt & Whitney Canada PT6C-67C engines, switched to autopilot and accelerated to 120kt at 1,000ft before crossing over the Delaware River. The helicopter induced minimal vibration and crossed 10 miles from its takeoff point in about 10min.

Back on the ground, a large American flag hangs over a production line humming with the construction of AW139s, AW119 light-singles and the AW609 tiltrotor. The facility produces about a third of Leonardo's AW139s, but Boeing would build all 84 replacement aircraft for the USAF in Philadelphia if it captures the UH-1N replacement bid, Clem says.