Since learning of the raid on Osama bin Laden’s Pakistani hideout in May I’ve wondered why the first of the two Black Hawk helicopters crashed inside the walls of the compound before the mission had begun to unfold.
Did someone forget to replace a vital cotter pin such as led to the Queen of Oak Bay ferry smashing into a Vancouver dock in 2005? Or did a refueling miscalculation send the machine on its way with a half empty tank, like an airliner a few years ago.
You would think after months of meticulous planning and exercises qualified mechanics would have done a last minute engine tune-up and re-checked the chopper’s fuel and oil levels.
Each Black Hawk, modified to mask heat, noise, and movement, and covered with radar-dampening ‘skin’, was manned by two experienced pilots. Yet the helicopter crashed the moment it arrived over the walled compound. It ended straddling the compound wall.
An article “Getting Bin Laden” written by Nicholas Schmidle published in The New Yorker’s August 8 edition explains what went wrong that moonless night.
For many months before initiating the raid an elite team of SEALS had practised every step of the entire plan using a mock-up of bin Laden’s compound built according to information gleaned from drone surveillance over Abbottabad. Then in mid-April the team “flew to Nevada for another week of rehearsals,” writes Schmidle. “The practice site was a large government-owned stretch of desert with an elevation equivalent to the area surrounding Abbottabad. An extant building served as bin Laden’s house. Aircrews plotted out a path that paralleled the flight from Jalalabad to Abbottabad.
“Each night after sundown, drills commenced. The pilots flew in the dark, arrived at the simulated compound, and settled into a hover while the SEALs fast-roped down.”
Rehearsals went off without a hitch; why did the May 1 assault end with the first helicopter plummeting into bin Laden’s compound?
“The moment the helicopter cleared the compound wall, the machine began ‘getting away’ from the pilot,” Schmidel writes. “When the helicopter began getting away from the pilot, he pulled back on the cyclic, which controls the pitch of the rotor blades, only to find the aircraft unresponsive.
“The high walls of the compound and the warm temperatures had caused the Black Hawk to descend inside its own rotor wash -- a hazardous aerodynamic situation known as ‘settling with power’. During training in North Carolina, this potential problem had not become apparent, because the chain-link fencing used in rehearsals had allowed air to flow freely.
“A former helicopter pilot with extensive special-operations experience said of the pilot’s situation, “It’s pretty spooky—I’ve been in it myself. The only way to get out of it is to push the cyclic forward and fly out of this vertical silo you’re dropping through. That solution requires altitude. If you’re settling with power at two thousand feet, you’ve got plenty of time to recover. If you’re settling with power at fifty feet, you’re going to hit the ground.”
As the helicopter fell, “the tail rotor swung around, scraping the compound’s security wall. The pilot jammed the nose forward to drive it into the dirt and prevent his aircraft from rolling onto its side. The Black Hawk pitched at a forty-five-degree angle astride the wall.”
It’s astounding no one considered or realized the flying dynamics might be different with a solid mud wall as compared to a chain link fence. This was no spur-of-the-moment raid. Engineers, combat generals, experts of all kinds had weighed every inch of the plan, yet overlooked a simple difference -- bin Laden built a solid wall. The U.S. fast tracked using open mesh wire.