Boeing: CSAR-X Contender Has Lower Downwash

By James T. McKenna | July 10, 2007

Boeing’s HH-47 contender for the contested U.S. Air Force Combat Search and Rescue-X (CSAR) contract has a downwash velocity 3-10 percent lower than that of its two competitors, the manufacturer claims. Downwash is the latest battlefield in Lockheed Martin’s behind-the-scenes fight to build political pressure against the Air Force’s choice of the Chinook as its next-generation CSAR helo. That company, which is pitching an EH101 variant with teammates AgustaWestland and Bell Helicopter, is again protesting USAF acquisition steps, having succeeded in having the U.S. General Accountability Office overturn the service’s November 2006 contract to Boeing. Sikorsky, which offers an S-92 variant, also is protesting to GAO again. Downwash isn’t known to be part of their protests. But press accounts have rehashed U.S. Army reports on Chinook downwash incidents and said Congress is looking at the issue. U.S. Sen. Mary Landrieu (D-La.) implied in a July 3 letter to Air Force Secretary Michael Wynne that Chinooks were pulled from rescue duty after 2005’s Hurricane Katrina for fear they would blow people off roofs. Boeing HH-47 Program Manager Rick Lemaster said in a press briefing today that the company is committed to limiting the HH-47’s downwash velocity to 59 kt, as measured up to 6 ft off the ground with the aircraft hovering at 80 ft. The Air Force limit is 65 kt. Lemaster said that max velocity would be below the overlap of the Chinook’s fore and aft rotors. Below the hoist point at the forward starboard cabin door, he said, downwash velocity would be 35-45 kt. He added Boeing’s calculations, based on published disc loading data for the EH101 and S-92, put the Chinook’s downwash velocity 3-10 percent below theirs. There undoubtedly will be more to come. For related news


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