The US Navy/Bell Boeing MV-22 Osprey test team plans to conduct a final phase of shipboard suitability tests in November that, it hopes, will lift the final operational restrictions still imposed on the tiltrotor before the start of Opeval by VMX-22 early in 2005.
The tests will be the last element of a four-year effort to clear the MV-22 from severe shipborne operational restrictions that were imposed following an incident in January 1999 when an Osprey on the edge of the deck made an uncommanded 6° roll to the left after becoming enveloped in the wake of a Boeing CH-46 further up the flightdeck of the LHD-class ship. Following extensive wind tunnel tests at NASA Ames from October 2001 to April 2002, the four-phase flight-test effort has covered several downwash surveys and shipboard deployments.
Major control law changes introduced in Phase III tests conducted on the USS Iwo Jima were further refined for later Phase IV tests on the USS Bataan in November 2003 and, more recently, in June 2004 under Phase IVB, again on the USS Iwo Jima. The changes altered the lateral axis control laws to overcome the roll perturbation due to wake interaction, and involved reducing the collective pitch of both rotors by 2° at full aft collective position to reduce thrust and "to firmly plant the aircraft on deck".
The team says the MV-22 equipped with the new control laws "exceeded all the design goals and significantly expanded the V-22 launch/recovery wind envelope for LHD spot 7 [aft landing area on the deck]". The revised control laws continue to be refined under the follow-on evaluations which are planned to include "V-22 on V-22" wake tests in three high-speed wind conditions. "Hopefully, we can put a stake in this, and if we can get those three wind conditions, we can get rid of the last of the operational restrictions," says the test team.
Source: Flight International
