For a decade after his terrible 9/11 attacks, which left over 3,000 Americans dead, Osama bin Laden avoided American authorities, often narrowly escaping bombings and raids by a window of hours.  But on Sunday May 1, 2011 in a raid authorized by U.S. President Barack Obama, U.S. Navy Seals shot and killed bin Laden inside a private residential compound in Abbottabad, Pakistan.

I. Stealth Choppers -- Key to the Strike?

According to numerous sources, including a report in the online magazine Army Times, one of the keys to the raid were modified MH-60 Black Hawk helicopters designed for stealth.

The helicopters were still relatively noisy, but they were virtually invisible to radar.  That was thanks to low observable modifications that added "several hundred pounds" of weight to the helicopters.  A UH-60 -- one of the most commonly used Black Hawk helicopters -- weighs about 10,624 lb. when empty.  A MH-60 can weigh between 11,124 and 11,624 lb.  And with the modifications, the empty chopper would be tipping the scales at 11,524 to 12,024 lb.

The modified helicopter bears little resemblance to a traditional Black Hawk, according to those who've seen them -- they have distinct lines.  And most notably their windshield has been painted with a special coating that reduces the radar cross-section.  That coating also presents a danger as it can interfere with the night-vision goggles pilots typically use to navigate at night.

II. History of the Stealth MH-60

The "low-observable" program, which reportedly birthed the unique chopper, had its roots in the stealthy AH-6 Little Bird choppers employed by U.S. Special Forces in the 1980s.  

In the 1990s, the U.S. Special Operations Command (USSOCOM), working with Lockheed-Martin Corp.'s (LMT) Skunk Works division, looked to revamp the design.  Skunk Works, which had been responsible for the F-117 stealth ground attack aircraft, applied its stealth experience to the 160th Special Operations Aviation Regiment’s MH-60s.  

The work was continued in the "1999 to 2000 timeframe" by the Boeing Company (BA), which was financed by USSOCOM to modify several MH-60s to the Lockheed's stealth design.  The plan was to station the new choppers at a base in Nevada under the command of a lieutenant colonel.  The plan was to assign 35 to 50 USSOCOM warriors to the unit.

Describes a source in the Army Times report, "The intent was always to move it out west where it could be kept in a covered capability. There were going to be four [low-observable] aircraft, they were going to have a couple of 'slick' unmodified Black Hawks, and that was going to be their job was to fly the low-observables."

"[W]ithin the last two years", those plans were cancelled, but not before a few of the stealth copters had been delivered.  Reportedly, the U.S. Military would rotate traditional MH-60 Black Hawk crews -- members of the 160th’s 1st Battalion, headquartered at Fort Campbell, Ky. -- to the Nevada base to train on stealth Black Hawks.  In short, the project was scaled back, but remained partially executed.

III. Launching the Mission

When President Obama gave the order to execute the strike, he may have launched the first major battlefield test of the new chopper design (though it is possible they were used in the recent Afghanistan and Iraq conflicts).

One mystery is how the helicopters were able to reach the target and return.  The stealth choppers reportedly lacked air-to-air refueling probes, which would disrupt the radar cross-section.  The maximum ferry range of the choppers was 1,318 miles.  So if they were launched at sea, they would have been unable to return, as the target was ~700 miles inland.  

More likely, the helicopters may have landed somewhere in Afghanistan, though the launch location is still ambiguous.  Also possible is that the helicopters could have been fitted with extended range tanks to complete the trip from sea and back.

According to cables aired by Wikileaks in recent months, it was clear that the U.S. believed senior military and government leadership in Pakistan were consorting with Al Qaeda, bin Laden's terrorist organization.  The operation thus was, according to some sources, carried out without informing Pakistan for fear that bin Laden would be tipped off and escape.

Speaking of Wikileaks, the whistleblowing-cum-espionage organization almost tipped off bin Laden that the U.S. authorities were onto his whereabouts, if only he had read their most recent publication.

Recently leaked profiles of Guantánamo Bay detainees identify the U.S. as recently suspecting that senior-level Al Qaeda were residing in Abbottabad, Pakistan.

According to a Pakistani news report one document reads:

In October 2002, Nashwan Abd al-Razzaq Abd al-Baqi, aka (Abd al-Hadi al-Iraqi), contacted and asked detainee (Libi) to work with him in Peshawar. Detainee accepted the offer and spent the next five to six months working under Al-Baqi organizing the purchase of supplies for fighters including medicine, lights, batteries, food, and clothing. In July 2003, detainee received a letter from Osama bin Laden’s designated courier, Maulawi Abd al-Khaliq Jan, requesting detainee to take on the responsibility of collecting donations, organizing travel, and distributing funds to families in Pakistan. Bin Laden stated detainee would be the official messenger between him and others in Pakistan.

In mid-2003, detainee moved his family to Abbottabad and worked between Abbottabad and Peshawar.  Between August 2003 and February 2004, detainee travelled to Shkai, Pakistan on three occasions. While at Shkai, detainee met with al-Qaeda’s Sharia Council, delivered funds to fighters and met with Hamza Rabia.

In mid 2004, detainee moved his family from Abbottabad to Bajaur. During October 2004, detainee received a letter from Bin Laden asking about the financial situations in Pakistan and Waziristan. In addition to the letter, there was a video tape of Bin Laden speeches.

If bin Laden had known that U.S. authorities were on to his secret hiding spot, he could have vacated the area.

Fortunately for the lives of Arab nationals and Americans, the hint Wikileaks dropped fell on deaf ears and bin Laden appeared oblivious to the impending strike.

IV. The Strike -- A Crash, but Mission Success

Early Monday morning, under the black of night, chaos erupted.  The helicopters successfully dumped a large team of Navy Seal special operatives, undetected by radar.  But even as the firefight in the compound ensued, one of the helicopters crashed to the ground.

It is thought that the crash may have been due to an unusual phenomenon called "settling with power", which occurs when a helicopter descends more rapidly than intended due to the rotors failing to produce sufficient lift to counter their turbulent downwash.

That might have been the "price" for the great stealth-avoidance characteristics of the chopper.  It is thought that the extra weight of the stealth modifications, combined with the full load of the combat team, likely combined to force the chopper down.

Fortunately no personnel were seriously injured, and the Special Forces operatives were able to destroy the body of the helicopter with thermite grenades.  But the explosion did not destroy all of the craft -- the helicopter’s tail boom, tail rotor assembly and horizontal stabilizers were left intact and unrecovered in a courtyard at the compound.

Pictures of those parts revealed the blocky radar-avoiding design and what might be the true story of the raid, if you believe retired U.S. Military staff.

V. More Questions Raised

The assassination raised many fascinating questions for the U.S. media, academic community, intelligence agencies, military, and government.  

For example, bin Laden was widely thought to be hiding in caves in the Hindu Kush Mountains between Afghanistan and northern Pakistan.  Instead, bin Laden appears to have been hiding in the swank residential compound since 2005.

Another mistaken belief was that bin Laden was suffering from kidney failure and required dialysis.  A search of the house revealed no dialysis equipment or medications, other than some eye drops and Vaseline.  

Bin Laden was also thought to be heavily armed, but was initially spotted unarmed, according to sources, though some claim he picked up a weapon after using one of his wives as a human shield.

And he made a mistake that may dearly cost Al Qaeda -- reportedly he left hard drives with a wealth of documents lying around the house, in direct violation with his own Al Qaeda code of operations he authored.  Those hard drives may provide U.S. operatives the clues they need to ferret out the remaining vestiges of Al Qaeda in the Middle East and Africa.

While there are many new questions, some fascinating dialogues from a tech perspective, and an abundance of theories, perhaps the most interesting is the tale of the stealth choppers and their role in the attack. If true, the operation stands as a great vindication of the U.S. stealth air initiative -- often chastised for its "over-spending".