On May 02, 2011, Seal Team Six, comprising elite U.S. Special Operations personnel, successfully executed a mission that terminated the life of the most wanted man on the planet -- Osama bin Laden (OBL). The hunt lasted almost a decade making this one of the most high profile raids in recent times, and a military operation that has secured a well-deserved place on the modern history syllabus in schools around the world. As an experienced and recently retired assault helicopter pilot and mission commander in the Royal Air Force, I spent 20 years working with UK and U.S. special forces, as well as the regular Army, in pursuit of terrorists from Northern Ireland to Kosovo and Macedonia to Baghdad. During my military career, risk was an equation of probability versus consequence, and in this article, I will offer a unique perspective that the ground operators in the OBL raid were not only blind to, but had no control over.
Personal accounts by Seal Team Six operatives have already hit the bookshelves; 'No Easy Day'; 'Memoirs of an Elite Navy Seal Sniper', as well as National Geographic's docudrama, 'Seal Team Six: The Raid on Osama bin Laden' -- all offer a ground operator's perspective. There is no doubt that the threats facing the Seals during the assault on the Abbattobad compound were significant, and all with lethal consequences. Radio frequency activated Improvised Explosive Devices (IEDs), suicide bombers, concealed snipers and booby traps are but a few of the asymmetric threats that pervade contemporary counter insurgency warfare and are supremely difficult to defend against. However, the vulnerabilities of the team during the strike phase were only a part of the story; the risks taken by the elite ground force were elevated well before their boots touched down in Pakistan.
Critical to mission success, the infil (infiltration) and exfil (exfiltration) relied on Blackhawk and Chinook helicopters to fly the teams, including the Quick Reaction Force, from Afghanistan, to OBL's abode in Pakistan, and back again. Mitigation of the threats during the first and last phase of the raid lay entirely in the hands of the capable aircrews. Once the wheels of the helicopters had lifted from Jalalabad, a whole new system of threats came into play; threats that the Seals had no control over in any shape or form, and with consequences that could have killed any one of the teams in the blink of an eye.
Risks in the airborne environment are generated from a complex catalogue of environmental, tactical, technical and enemy factors that are processed thousands of times a minute by the minds of the crews that conduct the missions. Flying under the cover of night at low-level is essential for covert and high profile raids, pursuing the element of surprise whilst ameliorating the risk of being detected by the enemy. Tactical flying of this nature also brings with it inherent dangers that require a high degree of flight training, experience, concentration, anticipation and rapid processing of data. References a pilot takes for granted during the day, such as the natural horizon and objects on the ground used for hovering, become less obvious at night. The scan a pilot uses by day consists of assimilating millions of references outside of the cockpit with limited glances inside at the instruments. By night, the routine changes to regular monitoring of instruments within the cockpit, including artificial horizons and radar altimeters, both essential for safe flight but at the same time, reducing the proportion of time spent looking out of the window. Consequently, masts, wires, chimneys, tall buildings, birds and trees become harder to detect, and if struck in mid-flight, have the ability to bring a helicopter down.
Night Vision Goggles (NVGs), also known as Night Vision Devices (NVDs), exponentially reduce the risks of flying in pitch black conditions whilst very low to the ground, and are used by most tactical crews flying in operational theaters. These ingenious inventions turn the world green with varying levels of image noise depending on the light levels -- the darker it gets, the noisier the picture becomes. Conversely, if a source of bright light is encountered, the image created by the NVG can become over exposed, a little like taking a photograph with a slow shutter speed. This blooming effect can blind the pilot momentarily until the NVGs readjust to the intensity of the light source. The route from Jalalabad to Abbottabad will have covered some of the most austere, dark and hazardous terrain a pilot could ever be pitted against. On the upside, valleys in mountainous regions are excellent routes for cover, especially if trying to avoid detection from enemy radar. On the down side, they also provide natural funnel features and bottlenecks where enemy insurgents are likely to set up firing points making the crews vulnerable to small arms or RPG attack -- obstacles such as wires and masts are also more prevalent in the valleys. Route selection by the aircrews will have balanced a requirement to conceal the helicopter formation from radar, against funneling and detection by the enemy.
NVGs also lack fidelity in depth perception requiring the pilot to continually evaluate the helicopter's speed and height in order to accurately gauge the rate of closure with obstacles and buildings. Advanced NVG technology can now superimpose certain critical data into a goggle drastically reducing the requirement for pilots to go 'heads in' or to conduct scans involving large head movements. The weight of the NVGs and helmet, along with the confined space of a cockpit make simple tasks much more difficult, increasing the onset of fatigue, and exacerbating the margins for error. Despite advances in NVG technology, certain conditions such as increased precipitation, reduced visibility and flight in mountainous or ocean regions can cause disorientation and loss of spacial awareness resulting in CFIT, or Controlled Flight Into Terrain -- a very real risk during the raid.
To deploy as many soldiers and firepower as possible onto the compound required the Blackhawks and Chinooks to fly in tactical formation during the infil. Apart from the obvious vulnerabilities of a mid-air collision, route selection would have been critical. Flying down a valley will funnel all aircraft in the formation; if an enemy firing point is overflown by the lead aircraft, the tail end charlie can become easy pickings. The northern Afghan/Pakistan frontier is plagued with insurgents, requiring the aircrews to be alert to enemy activity at every stage of the infil and exfil.
Most pilots will tell you that the transit is the easy part. It is the last two minutes of the infil that provide the moments of sensory and data overload, where spikes of activity cross well and truly over the red capacity line, and where the demand for intense concentration is at its peak as a transition is made from forward flight to the hover. This is the part of the mission where staying in front of the "drag curve" (a term in the aircrew world for keeping on top of your game) is key to survival and where dropping behind it can be fatal. The aircrews and Seal Teams are at their most vulnerable as forward speed tails off and the requirement for more power increases due to a loss of translational lift (a phenomena that increases the lift component and reduces the need for power as airflow across the main rotor surpasses 30 to 40 knots -- the reciprocal is also true).
At this point a myriad of simultaneous risks comes into play all with competing priorities -- a heavy load will reduce power margins as the helicopter comes into the hover -- accentuated by hot temperatures and high altitudes. In normal circumstances the crew will have calculated the weight and power required (and available) at the target, to ensure a hover outside of ground effect is achievable. The downdraft created by the main rotor blades creates a ground cushion as the helicopter descends into the low hover -- reducing power requirements -- commonly known as "ground effect." However, there are certain instances that may reduce the amount of lift that the engines and main rotor can generate. Flying too close to the lead helicopter can lead to dirty air being sucked through the blades of the second or third aircraft, potentially leading to a loss of lift and a topping out of power which could result in a heavy landing. The compound in Abbatobad was surrounded by high walls making recirculation a serious hazard, a phenomenon experienced when the downwash is forced down and out from the main rotor, up the wall, and back into the blades. This can leave the pilot with insufficient power to halt a rapid downward trajectory, resulting once again in a heavy landing and a rolling of the helicopter. Once over the target at low altitude and zero forward groundspeed, the threat from small arms fire or RPG attack is extreme -- probability and consequence at this point are nudging full scale deflection on the risk-ometer.
To intensify matters further, identifying the building as it rapidly approaches can be a difficult procedure in itself, even with advanced GPS and NVG systems. Negotiating the final approach so the formation has an effective in-to-wind component is desirable to reduce power requirements and increase power margins, but can be complicated if the crew are late in identifying the target. Wind from the forward sector also assists with delaying an ensuing dust cloud that forms around the cockpit as the aircraft slows; a result of fine sand grains being kicked up by a powerful downwash. A suitable and prominent reference by the pilot has to be selected quickly as the helicopter reaches the hover and as the dust cloud envelops the cockpit. Without a reference the pilot will become disorientated, leading to angles of bank that can, in some instances, put a helicopter on its back. Drifting in the hover is common when references are lost due to the dust cloud. In the confines of the Abbottobad compound, the likelihood of a tail-rotor strike due to unintentional drifting was a serious threat that if realized, would have culminated in catastrophe. To give you an example of how quick a situation can develop, the helicopter below suffers a tail rotor drive failure in the late stages of approach and within eight seconds of the problem occurring catastrophe has struck -- aircrews and passengers are often at the hands of the gods during such violent technical failures.
The threats and risks associated with airborne infils and exfils, if played out, come with depleting outcomes that Seal Team Six would have known little about or had any influence over. Personal accounts of the raid provide an extraordinary insight into the dangers surrounding the team, with the difference between gallantry and success, bad luck and failure, being split by a cigarette paper. The mettle that all members of the OBL raid displayed during the strike phase is truly remarkable but when you consider the threats, risks and success in the context of the entire mission -- "remarkable" rapidly becomes "miraculous."