Some aircraft fulfill their missions so well that they seem to last almost forever. The Sikorsky S-61/H-3 Sea King helicopter, the prototype of which made its first flight way back in 1959, appears on its way to achieving this “never die” status.
The U.S. Department of State last month accepted the first two modernized S-61s to come out of a purchase agreement with Sikorsky Aerospace Services (SAS) that could see as many as 110 S-61Ts delivered over five years. U.S. rotorcraft modification specialist Carson Helicopters developed all the modifications, owns the supplemental type certificates (STCs) and rebuilds the modified aircraft.
The S-61T is the result of a number of S-61/H-3 improvements: composite main rotor; a five-screen, integrated glass cockpit developed with Sagem Avionics; engine air-particle separator; fixed landing gear; high-speed electric rescue hoist; fire-fighting tank provisions; Martin Baker energy-absorbing troop seating; improved fuel-quantity indicating system; cockpit air conditioning; electronic equipment designed to meet military requirements; and a shortened fuselage.
The following new elements are in the works: composite tail rotor blades (STC expected in six months); an upgrade of the General Electric T58-140 turboshaft engines to T58-16 engines (increasing power from 1,500 shp to 1,870 shp and expected to fly in August); an IFR-approved Rockwell Collins primary flight display (STC expected in two months); and a new autopilot to replace the helicopter’s original, 50-year-old stabilization system.
According to Carson Helicopters CEO Frank Carson, the composite main rotor blades alone provide the aircraft with 2,000 pounds more lift capability at the same horsepower than a comparable S-61 with the original blades, as well as a 15-knot improvement in cruise speed. He expects the T-58-16 engines will provide a 3,000-pound improvement in lift at 35-degrees C and 6,000 feet pressure altitude, a State Department goal for operations in Afghanistan.
“The re-engining project is very important,” said Anthony Serksnas, Sikorsky director of S-61 programs, “because it will give the modernized S-61 performance comparable to the latest Mi-17v5 [designed by Russian company Mil], especially in hot and high conditions in Afghanistan.” He said Sikorsky hopes to “qualify” the T58-16 in the S-61T within 18 months. As a military aircraft, the S-61T does not need civil certification, approval by Sikorsky’s qualification assurance board being sufficient. Frank Carson said he will seek an STC for the engine upgrade. Serksnas said the State Department has also requested crashworthy ballistics-tolerant fuel bladders for its S-61Ts.
The Sikorsky-State Department contract for S-61Ts is an indefinite-delivery/indefinite-quantity (IDIQ) purchase agreement. This type of agreement, Serksnas explained, “is a broad-based contracting vehicle that is used when the government is uncertain of the quantities of aircraft it would like delivery of. In this case, it could be from four to 110 aircraft.” The Department requested this wide range because several of its own agencies and the Department of Defense expressed interest in the S-61T, in part as a replacement for Mi-17 helicopters now in use in Afghanistan and Iraq.
The baseline S-61T uses the H-3 military helicopter, which has the shorter fuselage. The first four S-61Ts, which will support missions for the U.S. Embassy in Afghanistan, are actually former S-61Ns, two of which were shortened and two that were not. The State Department is looking at 15 to 20 follow-on aircraft for delivery this year and next year, and the majority of these will be modified H-3s. Carson Helicopters is doing all the modification work, with a rebuild taking about six months per aircraft.
Some 300 civil and military S-61s and H-3s remain around the world, he said, some built under license by Agusta and Westland. The State Department’s primary source right now is the U.S. Navy, which has 65 H-3s stored at the Davis-Monthan Air Force Base “aircraft boneyard” in Arizona.
Serksnas said the Department in late June initiated the transfer of 20 of these Navy H-3s for the S-61T program. Sikorsky has access to other airframes through customers looking to trade in aircraft. Carson Helicopters, which has been acquiring and modifying Sikorsky helicopters since 1963, obtains airframes on the open market.
Serksnas said Sikorsky officials had expected customer interest in the aging S-61 fleet to begin to decline about 10 years ago, but then the company noticed that spare parts sales continued to remain healthy. “A whole industry sprang up around supporting the S-61,” he said. “We knew Carson was doing some things and we took a closer look.”
Frank Carson said he thinks there are at least 20 to 30 years of life in his rebuilt S-61s. “In some respects our aircraft are better than the original–with new wiring and radios, the glass cockpit, the composite blades, the upgraded engines and new parts for various dynamic components being built by Sikorsky.”