Archive for March, 2010

Aircranes

Monday, March 29th, 2010

While some helicopters are designed for speed, others are built simply to lift a lot of weight. Perhaps the best example is the Erickson S64 Aircrane. The S-64 was the first helicopter built as a flying crane with an aft-facing pilot station that allows the pilot to directly view the load being carried and fully control the aircraft during precision operations. This unique helicopter was certified in 1969 and originally manufactured by Sikorsky Aircraft as the S-64A Skycrane. In 1992, Erickson purchased the type certificate to the Sikorsky S-64E and S-64F models, and the aircraft designation was changed to the S-64 Aircrane. Today, Erickson owns and operates a fleet of 18 Aircranes throughout the world.

The Aircrane’s rotor system consists of a six-blade fully articulated main rotor and a four-blade tail rotor. The S-64E is powered by two Pratt and Whitney turbine engines generating a combined maximum takeoff rating of 9,000 shp, giving the S-64E model an external load lift capacity of 20,000 pounds (9,072 kg) at sea level. The S-64F features a strengthened airframe, a rotor system with longer chord length, and two Pratt and Whitney engines rated at 9,600 shp which gives the S-64F model an external load capacity of 25,000 pounds (11,340 kg) at sea level.

Initially, the Aircrane’s civilian mission centered on timber harvesting and power line construction; however it has been used in many areas of heavy lift construction. For example, installing ski lifts, air-conditioning systems, and delicate steel artwork.

One of the most publicized jobs involved removing and replacing the Statue of Freedom, which sits atop the United States Capitol dome in Washington D.C. Using its precision maneuvering capability the Aircrane lifted the statue off of its pedestal on May 9, 1993, and placed it back after much needed renovation on October 23, 1993. Another high-profile project was the construction of the CN Tower in Ontario, Canada. In 1975, the Aircrane transported and placed the seven-ton steel sections that made up the antenna and weather metering systems, on at that time what was the world’s tallest freestanding structure, at an altitude of more than 1,850 feet.

In 1992 Erickson created the Helitanker firefighting system with a 2,650-gallon tank that can spray water, foam mix, or fire retardant. Two snorkel attachments take 45 seconds or less to fill up from any freshwater or saltwater source at least 18 inches deep. In 1997 the FAA certified a horizontal monitor water cannon attachment to fight high rise structure fires in congested urban areas. The cannon uses aircraft hydraulic power to propel a focused stream of water or foam mix up to 150 feet at a rate of up to 300 gallons per minute. The helicopter has now become a valuable firefighting tool in California and other parts of the world.

See the AOPA Pilot story on the Sikorsky Skycrane, “Dancing with Lucille.”

 

Need for speed

Wednesday, March 17th, 2010

Flying a rotor system edgewise through the air creates a problem known as dissymmetry of lift. One side of the disc advances into the wind (headwind) while the other side is retreating (tailwind). For a fixed angle of attack, the lift on the advancing side is greater creating a lift imbalance that increases with airspeed. Early engineers came up with a way to equalize the lift by changing the angle of attack (flapping) as the blade moves around the rotor disc. This required increasing the angle of attack on the retreating side as the helicopter gained airspeed. As with any airfoil, the angle of attack can only increase so much before it stalls. Referred to as retreating blade stall, this problem limits a helicopter’s forward speed.

Ever since the development of the helicopter engineers have tried to figure out ways to get around the rotor system’s speed limitation. Although there are several ideas for this, one is a co-axial rotor design. This arrangement uses two stacked rotor systems with the same axis of rotation, but turn in opposite directions. This way when the retreating blade is losing lift the blade above (or below) it is advancing and gaining lift. This helps equalize lift across the rotor system. (There are other advantages as well like increased lift ability and no need for a tail rotor.)

In the 1970s Sikorsky demonstrated high speed flight with the S-69 Advancing Blade Concept (ABC) system. The S-69 used two rigid counter-rotating rotor systems with an auxiliary propulsion arrangement. Today, Sikorsky Aircraft is incorporating decades of research and development from the S-69 into its X2 technology concept demonstrator. The X2 aircraft uses two rigid counter-rotating rotor systems and a pusher propeller for auxiliary propulsion. Additionally, Sikorsky has included new technologies including an integrated fly-by-wire system, high lift-to-drag rigid blades, low drag hub fairings, and active vibration control.

The X2 is currently being test flown at Sikorsky’s West Palm Beach, Florida, development flight center. In October 2009 the X2 achieved a speed of 106 knots. This milestone moves the company a step closer to its stated goal of demonstrating that a helicopter can cruise comfortably at 250 knots while retaining such desirable attributes as excellent low-speed handling, efficient hovering, and a seamless and simple transition to high speed.

If Sikorsky is successful, the next 10 years could bring a new era of high speed helicopter flight.

Thoughts on EMS training

Thursday, March 4th, 2010

The helicopter EMS industry is struggling with a high accident rate. Several months ago the NTSB published recommendations ranging from equipment requirements to increased training. There seems to be no doubt in the helicopter industry that the FAA will mandate one or more of the NTSB recommendations this year. In the past the FAA has been reluctant to act; however, the feeling now is if the FAA does not come out with something strong to stop the accidents, Congress will.

In my opinion, increasing the amount and type of training will do the most good. Using technologies such as HTAWS and NVGs are helpful as well, but I think the most benefit will come from better training.

EMS is a tough business with lots of cost pressures, and spending more money on training can be hard to justify sometimes. I was told by one EMS vendor that watching costs was paramount to survival, if he couldn’t bid a competitive price and lost contracts they’d be out of business.

An interesting dichotomy was when I flew a corporate helicopter. I was trained at FlightSafety every six months and could take the helicopter (a Bell 430) out once a month to practice. The corporate mission was nowhere near as demanding as EMS flying, yet there was considerably more emphasis placed on training. Sometimes I wonder if the difference was because the person who ultimately approved the training budget also rode in the back of the helicopter. Those passengers certainly had a vested interest in the proficiency of the pilots.

It will be interesting to see what the FAA does. If operators can afford the technology and the increased training then that’s the best scenario. However, if it’s one or the other I believe the best improvement in the accident rate will come from enhanced training.