A United Technologies Corp. Black Hawk helicopter carrying U.S. Navy SEALs to Osama Bin Laden’s hideout was downed by an air vortex caused by unexpectedly warm air and the effect of a high wall surrounding the compound, not mechanical failure or gunfire, according to U.S. officials and a lawmaker.
The Army pilot from the service’s most elite aviation unit executed a hard but controlled landing -- clipping a corner wall -- after the chopper lost lift. The 12 heavily armed SEALs exited the aircraft unharmed.
Senior government officials briefing reporters by telephone on May 1, the day bin Laden was killed, gave conflicting accounts, first saying the chopper experienced a mechanical “malfunction” and then backtracking without an explanation.
The initial administration explanation wasn’t accurate, according to U.S. government officials, a lawmaker and congressional staff briefed yesterday by Vice Admiral William McRaven, leader of the Joint Special Operations Command.
The command includes the Army’s 160th Special Operations Aviation Regiment, which piloted the SEALs of the Navy’s Special Warfare Development Group to the house in Abbottabad, Pakistan. McRaven yesterday briefed the Senate and House armed services and intelligence committees.
Rappelling Mission Ditched
The aviation unit is based at Fort Campbell, Kentucky. President Barack Obama is scheduled to visit the base on Friday and see members of the 160th, said an Army official who spoke on condition of anonymity because he wasn’t authorized to discuss the trip.
Twenty-five Navy SEALS were flown to the bin Laden home by two Black Hawks, CIA Director Leon Panetta told the PBS “News Hour” May 3.
The helicopter that crash-landed was supposed to hover over the compound’s courtyard so that the SEALS would rappel, or “fast rope,” to the ground, Panetta said.
According to two U.S. officials, who praised the skill of the pilot, the chopper lost the lift necessary to hover because it entered a “vortex” condition. At least two factors were at play -- hotter than expected air temperature and the compound’s 18-foot-high walls, they said.
The wall blocked rotor blade downwash from moving down and away as it normally would. This caused disturbed airflow to move in a circular, upward and then downward path back through the top of the rotor, causing insufficient lift for the aircraft.
The pilot, realizing he had lost lift, landed quickly in a maneuver practiced by pilots to deal with helicopter flight conditions known as “settling with power,” one official said.
Another explained that if a helicopter hovers next to a large enough building at just the right distance, moving air created by the rotors won’t be able to exit freely. Instead, it will hit the wall and have nowhere to go except back into the rotor, robbing lift.
The pilot executed a “hard landing” as a result, House Armed Services Committee ranking Democrat Representative Adam Smith told reporters after a McRaven briefing.
Asked if there was a mechanical failure in the United Technologies’ Sikorsky aircraft, Smith said, “I don’t believe that is what happened.
‘‘As was explained to me, with the temperature and the setting, it came down faster than they anticipated so I don’t believe there was some sort of mechanical failure. It’s just those were tough conditions to land in,” Smith said.
House Armed Services Committee Chairman Representative Howard McKeon of California reiterated in Washington yesterday that “it was not a mechanical failure.”
He also said he had “no sense from the military that they had any concerns about” leaving wreckage of the modified Black Hawk, said McKeon.
The commandos detonated an explosive to destroy the helicopter, which the Army Times reports was a specially configured stealth model Black Hawk.
Two 160th additional MH-47 special operations Chinook helicopters provided back-up and assisted in flying out the raiders.
Sikorsky Aircraft spokesman Paul Jackson said the company hasn’t been contacted about any aspect of the raid.
Once known as the secret Task Force 160, the aviation regiment was formed in 1981 and has participated in most major U.S. military operations since the 1983 invasion of Grenada. Its pilots are known as the “Night Stalkers.”
Five of its personnel were lost and eight aircraft, including two Black Hawks, were either destroyed or damaged during the October 1993 battle in Mogadishu, Somalia.
The unit’s Black Hawks and the mission to rescue the air crews were the basis of the book and movie “Black Hawk Down.”
The unit flies the Sikorsky MH-60 Black Hawk, Boeing Co. MH-47E heavy assault chopper, and the Boeing A/H-6M Little Bird, used to ferry Army Delta Force commandos during a raid in the invasion of Panama to free a jailed American businessman, Kurt Muse.