February 14, 2012

What Brought Down 160th SOAR's Stealth Black Hawk?

Bin Laden gets face-shot

When the Osama Bin Laden raid went down, there was a flurry of news reporting, many initial reports stumbling over themselves as both the media and the White House struggled to get their stories straight.  Who executed the raid?  How was Bin Laden killed?  Who is Seal Team Six?  Our readers already knew the answer to that last one, but you get the idea.  From what I gather, and we don’t have the whole story even today, is that the actions on the objective were fairly straight forward.  Maybe there were one or two terrorists who had armed themselves, but it doesn’t sound like that slowed ST6 down much, if at all.  Everything was kosher until they began to exfil off the objective.

What happened next would reveal a previously classified aviation program to the world and potentially create an international crisis.

160th Special Operations Aviation Regiment’s Secret Helicopter

From a training event with 160th back in 2006

As a member of 3rd Ranger Battalion and 5th Special Forces Group, I flew with 160th numerous times in both Afghanistan and Iraq.  I’ve seen 160th pilots do some amazing things with their aircraft.  They put us down on roof tops, they’ve had the co-pilot lean out of the helicopter and deliver fire support with an M4, and I’ve even been on a MH-60 as the pilot navigated his helicopter between power lines with surgical precision to insert my ODA on an objective.  I have nothing but respect for these guys, and it surprises no one that it was 160th that successfully conducted the OBL raid with the SEALs.

While I was in Army Special Operations, I heard nothing, and I mean not even a whisper of any secret helicopter projects.  Not even a rumor about stealth helicopters.  This goes to show how tight the Army’s OPSEC was around this project, and with good reason.  As we now know from the wreckage left behind in Pakistan, at least one stealth helicopter was on the mission, but probably two or three as that is how many helicopters would be needed at a minimum for the raid, and having one stealth helicopter and two non-stealth MH-60’s flying in formation together would kind of negate the purpose.

In this case, the stealth capabilities of these helicopters would be needed to insert a Ground Assault Force into the target area while evading Pakistani radar stations during this cross border operation.  Bin Laden was living near a Pakistani military base in Abbottabad, a town filled with active duty and retired military officers.  Who would’ve thought…

While 160th is based at Ft. Campbell, Kentucky, it turns out that there is also a element of the Special Operations aviation unit located off-site called Echo Squadron.  The exact location of Echo Squadron will remain undisclosed due to OPSEC considerations.

Stealth Hawk Down

Stealth Hawk tail section

While it appears that one helicopter landed inside the compound and extracted successfully, another crash landed.  This forced the ST6 operators, pilots, and any flight crew to initiate the destruction plan.  More than likely they popped some thermite grenades inside the downed Stealth Hawk and cross loaded onto one of the other aircraft.  This is another reason why you never have just one bird on station for a mission like this, if one aircraft goes down, you have men stranded on the ground.  But why did the crash happen to begin with?

After consulting with experts in the field of rotary wing aircraft, it seems that the most likely cause of the crash was due to a phenomena known to pilots as “settling with power” with atmospheric conditions potentially playing a role as well.  Helicopter pilots will almost always attempt to land while facing into the wind, however, the pre-determined approach into the objective in this case may have actually given them a down wind landing.  If the rotor wash pushed from the rotors down to the ground, then comes back up and pushes into the decent path of the helicopter, it can then make the aircraft unstable.  This is how settling with power can destabilize a helicopter.  The rotors essentially created a vortex of dead air space that could no longer generate lift.

The rotor blade system needs clean, that is, uniform air to produce lift.  If instead it gets un-uniform air, such as air previously disturbed by the helicopter’s own rotor wash, than the pilot could be in for some trouble.

At this point, the pilot would have begun to lose control of the aircraft from self-induced turbulence.  Without lift and maneuverability, he would have to conduct a controlled crash as a last resort.  As we see in the pictures, the tail rotor section split over an outer wall of the compound.  Did this obstacle also disrupt the air flow from the main rotor system and destabilize the aircraft?  Maybe.

What is it?

Artists rendering of the Stealth Black Hawk

As pictures of the wreckage began to filter out to the media from Pakistan, the main question became: What the hell is it?  There was speculation that it was an entirely new type of helicopter cooked up deep inside some black budget Special Access Program at Area 51.  Others made the observation that it was more likely a highly modified MH-60 helicopter.  I pulled the following picture off the comments section of an Aviation Weekly article not long after the OBL raid:

Stealth Hawk/UH-60 comparison

As you can see above, the main rotor system of a conventional Black Hawk does look an awful lot like that of the wreckage left behind in Pakistan.

Aftermath

While the OBL raid was an overwhelming success, it also exposed a Top-Secret helicopter program.  Certainly this was something taken into account by both military planners at JSOC as well as political leadership in Washington, DC.  They would have worked a risk mitigation strategy and determined that the intelligence justified the raid even if it came at the expense of compromising a classified program and certain Special Operations Tactics, Techniques, and Procedures.  I think I join the vast majority of Americans in agreeing with this decision, but let’s also examine the negative effects.

Within weeks the press was reporting that Pakistan was letting officials from the Chinese government look at the wreckage of the Stealth Black Hawk.  Some experts, optimistically in my opinion, have weighed in saying that the Chinese will be able to reverse engineer the stealth helicopter technology in a matter of months.  I’m not so sure. The Clinton administration initiated a series of technology transfers to China and we’ve all heard about Chinese hackers engaging in industrial espionage.  It seems that it was only relatively recently that the Chinese built a functioning stealth fighter.

Chinese J-20 Stealth Fighter

At any rate, it seems beyond a shadow of a doubt that at some point countries antagonistic towards the United States will reverse engineer stealth technology, it’s just a question of when.  As for the Stealth Black Hawk (the official designation of this aircraft remains unknown) you can be sure that 160th combed over every piece of intel and technical detail when working up their After Action Review to avoid a similar incident in future operations.

About the Author

is an eight year Army Special Operations veteran who served as a Sniper and Team Leader in 3rd Ranger Battalion and as a Senior Weapons Sergeant on a Military Free Fall team in 5th Special Forces Group. Having left the military in 2010, he is now working towards a degree in Political Science at Columbia University. Murphy is the author of Reflexive Fire, Target Deck, the PROMIS series, and numerous non-fiction articles about Weapons, Tactics, Special Operations, Terrorism, and Counter-Terrorism. He has appeared in documentaries, national television, and syndicated radio.

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  • RW11

    Afghan1 I think the phenomenon of "Vortex Ring State" and recirculation manifest in very similar ways.  Although I understood your writeup, I am not sure the lay-person will. I'm going to try to break that down a little further without sounding like an asshole. Always a challenge.  There are always a tip vortices at the edge of any airfoil, rotor blades included. This is where the high pressure air below the surface cycles up to the relative low pressure above the surface. This disturbance causes no lift to be produced on that section of the blade/airfoil where the vortex exists. This phenomenon is reduced when close to the ground, or in "ground effect" because downwash deflects off the ground/surface below you to carry part of the vortex away from the rotor system...reducing its impact on lift.  An additional vortex can develop in a rotor system if air cycles up through the rotors due to outside factors such as: high rates of decent or high pressure below the rotor due to the confinement of air in....say an enclosed compound. This will happen closer to the hub, perhaps about ¼ to ⅓ the length of the blade out from the center-hub. This is because the velocity of the air moving downward on this section of the blade is lower than it is the further out you go on the blade (except the tip, which is subject to the tip-vortex described above). So..it is the creation of this additional, and sometimes unpredicted, vortex about ¼-⅓ the length of the blade out from the hub that causes a reduction of lift.  Given the situation, the phenomenon was unrecoverable after it developed.  As is usual. A picture is worth 1000 words. Here is a vortex ring state, out of ground effect hover, and in ground effect hover.

  • myfinaloption

    good read

  • Andreas M

    Great article Jack, very insightful.

  • caseymac1944

    Awesome as always! Thanks Jack!

  • Afghan1

    It should be noted that there is difference between "settling with power" and "vortex ring state", although they are sometime used erroneously as the same thing. "Recirculation" is also another seperate phenomenon. Settling with power means not having enough power available to arrest your rate of descent. High density altitude and heavy gross weight both contribute very much to this. Vortex ring is basically falling into your own downwash. Low forward airspeed (made worse by landing downwind) combined with a decent rate of descent can cause this condition. To recover you have a couple options; get airspeed or remove yourself from the vortices. An underused technique is to quickly put in lateral cyclic to move the aircraft sideways into clean air. Recirculation is when there are obstacles (wall, heavy treeline, etc) that force the downwash back vertically where the air is then reintroduced back into the rotor system. It isn't the vortices that are the problem, but the movement of the air. The induced airspeed changes the angle of attack of the blades and leaded to less available lift. Anyways, just giving a bit more info on the phenomenons that could have contributed to this incident. Without more info it's hard to know what exactly caused it. All of these events are pilot induced, but the operational need of the mission obviously force the pilots to take greater risks when selecting their approaches then in a non-combat situation.