After 17 years of continuous operations in Afghanistan and Iraq, the US Air Force’s combat rescue workhorse, the Sikorsky HH-60G Pave Hawk, is looking tired.
The 96-helicopter fleet has far outlived its average per-aircraft life expectancy of 6,000 flight hours, with each rotorcraft now averaging 7,100h, according to an August report by the US Government Accountability Office. Only about 68% of the fleet was mission-capable in fiscal year 2017: below the USAF’s desired 75%.
US Air Force
The Pave Hawk is becoming harder to maintain. Airframe, turboshaft engine, and flight control failures are common, says the GAO. On average, the fleet spent 332 days in depot-level maintenance in FY2017, compared with 233 days in FY2007 – a more than 40% increase.
“The biggest impact has been the burden on our maintainers, the sustainment when we are not flying,” says Lt Col Charles McMullen, a USAF Pave Hawk pilot. “The aircraft go through maintenance cycles much faster. The cost to sustain those airframes as components get older is also going up.”
Fortunately, by as early as this December Sikorsky hopes it will be able to test fly the aircraft’s replacement, the HH-60W. The new Pave Hawk II – or Whiskey – variant boasts longer range, with a 2,500 litre (660USgal) internal fuel tank, and a specially-developed tactical mission kit that will give pilots and pararescue crew information from a phalanx of sensors.
Sikorsky
In August, the first two engineering, manufacturing and development (EMD) helicopters moved off the final assembly line in Sikorsky’s Stratford, Connecticut plant, where they were built alongside US Army UH-60 Black Hawks and US Navy MH-60R Seahawks. The rotorcraft will be transferred to the company’s West Palm Beach, Florida facility to undergo several months of instrumentation checks before test flights in December.
The USAF has awarded the Lockheed Martin-owned company a $1.5 billion contract to deliver four EMD-phase helicopters and five system demonstration test articles. The rotorcraft manufacturer is also contracted to provide six aircrew and maintenance training simulators, and instructional courseware.
The USAF’s programme of record calls for 112 helicopters, potentially worth about $7.9 billion to Sikorsky. The service expects to have its first aircraft by March 2020, three months ahead of schedule, and the GAO says deliveries should run through 2029.
Lockheed Martin
Central to a combat rescue team’s ability to perform extraction missions is being able to gather and organise information quickly, says Tim Healy, Sikorsky’s director of air force programmes and a former Pave Hawk pilot.
“Oftentimes you’d take off in a general direction and you are flying en route to where the person needs to be rescued, at the same time you are planning the rescue,” he says.
With that in mind, the Whiskey variant sports two mission computers to control, integrate and display information. Data from electro-optical/infrared sensors, radar, missile and radar warners, and laser warning systems is continuously gathered and distributed across seven flat-screens.
“It’s not just the two pilots that are doing the mission thinking. It’s the two pilots, two pararescue crew members and the special mission aviators [gunners],” says Healy, emphasising the need for the crew to share information. “A really good crew, when you hear them talking, it’s like an audio ballet.”
The avionics allow the helicopter to automatically hold a hover over a spot chosen by the pilot, enabling the crew to give more of their attention to the rescue and potential hostile forces.
Combat rescue crews have to work inside a cabin that is about 18in smaller than the standard HH-60M. The back part of the helicopter’s cabin, where the space starts to narrow towards the tail boom, has been redesigned to accommodate the aircraft’s larger internal fuel tank, which has almost twice the capacity of the Black Hawk’s 1,360 litre structure.
“We had to figure out a way to make the inside bigger without making the outside bigger,” says Healy, adding that “some new and improved aluminium alloys” are being used to keep weight down. The aircraft’s gross weight is 10,200kg (22,500lb); just 227kg more than the Black Hawk.
The extra fuel and marginal weight increase gives the helicopter a 195nm (361km) combat radius. It also can hover at 4,000ft and temperatures of 35°C (95°F) at the mid-mission point.
Despite its large internal fuel tank, the Pave Hawk II also comes with a refuelling probe on its right side, which it can use to take on fuel from a Lockheed HC-130 tanker.
“It also has a fuel dump system. Sometimes when you are hovering at a high altitude you want to dump fuel,” says Healy. Beyond those modifications, 75% of the rest of the Whiskey aircraft remains the same as the UH-60M upon which it is based, enabling maintainers to borrow parts from the US military’s most abundant medium-lift helicopter.
“We did not have to change any of the dynamic components, like rotor blades, drive train, transmission… all of that is common with the UH-60M,” says Healy. “We wanted to take advantage of all the benefits of the Black Hawk but also update and bring it up to a modern state of technology.”
Source: Flight International
