It was a quiet winter night within the English village of Cley subsequent the Sea, inhabitants 400. 2014 was only one week outdated and everybody was simply getting again into the swing of post-Christmas residing. Peaceable. Quiet. Till a flock of geese took down a US Air Power helicopter of their yard.
The helicopter was a part of a two-aircraft formation on a coaching mission, two Sikorsky HH-60G helicopters higher referred to as Pave Hawks. It was a workhorse of the US Air Power, in use since 1982 and utilised in nearly each navy operation within the intervening years. Whereas the Pave Hawk is now being phased out in favour of the Jolly Inexperienced II, the US Air Power alone nonetheless operates 99 Pave Hawks.
A key cause for that is that the Pave Hawk is designed to go locations different plane received’t. It flies low, beneath radar protection, hugging the terrain in what’s recognized within the navy as nap-of-the-earth flight. The forward-looking infrared system makes them significantly effectively suited to night-time low-level personnel restoration operations.
This explicit Pave Hawk, tail quantity 88-26109, was assigned to the 56th Rescue Squadron, working out of RAF Lakenheath as a part of the US Air Forces in Europe (USAFE)’s forty eighth Fighter Wing. The mission that night time, the seventh of January 2014, was for the 2 Pave Hawks to fly in formation for a coaching state of affairs rescuing a downed F-16 pilot at midnight.
The pilot of the mishap helicopter and the co-pilot of the lead helicopter developed the mission plan the day earlier than. All crew members would put on night-vision goggles. They’d depart from RAF Lakenheath an hour after sundown and fly about 36 nautical miles to a degree south of Blakeney. There, they might orbit, confirm the standing of the hypothetical downed pilot and conduct a risk evaluation. The 2 helicopters would stay in formation and fly low-level for about three and a half nautical miles to a touchdown zone close to the village of Salthouse, a website continuously used for coaching missions. At such low altitudes and at midnight, their choices have been restricted. The deliberate routing needed to keep away from obstacles, air site visitors and native noise-restricted areas.
The mission plan complied with all operational necessities and was authorised.
That very same day, the day earlier than the accident, the Wildlife Belief counted a flock of some 400 geese together with different birds roosting within the space.
The Blakeney Level Nature Reserve is a widely known habitat for giant flocks of migratory birds and is designated as avoidance zone: “keep away from by 500 toes or 2 nautical miles for flying choices”. The UK Army Low Flying Handbook recommends that aircrew ought to cross coastlines at proper angles and above 500 toes above floor stage to keep away from chook strikes. Nonetheless, this mission was a nighttime tactical low-level formation, supposed to be flown below the quilt of darkness and required flying beneath 500 toes.
A month earlier, in December 2013, a storm surge had flooded the coastal marshes, together with Blakeney Reserve. A number of flocks of birds had moved southeast to roost on drier floor.
The crew had entry to chook exercise maps throughout planning. The December map confirmed reasonable chook exercise west of the touchdown zone at nightfall. The January map, launched the day of the coaching mission, indicated a low-level space of chook exercise over the Cley Marshes. The crew had entry to the maps for reference throughout mission planning. The maps indicated an space of reasonable chook exercise at nightfall (outlined as one hour earlier than and after sundown) to the west of the proposed touchdown zone. Because the mission departed after sundown and would arrive on the touchdown zone an hour after nightfall had ended, this threat was thought of mitigated.
The important thing level: All required procedures for evaluating dangers and advantages have been adopted.
On the day of the crash, the Wildlife Belief counted zero geese.
The 2-aircraft formation departed at 17:33: 90 minutes after sundown and half an hour after the top of nightfall, half an hour after the reasonable nightfall chook hazard warning had expired. The helicopters flew north to start out their simulated mission to rescue the hypothetical downed F-16 pilot below the quilt of darkness.
On the way in which to the primary level, they performed simulated risk countermeasures. The helicopters arrived on the first level 25 minutes into the flight and began a left orbit, simulating a test on the downed pilot’s standing.
Excessive winds close to the preliminary holding level, south of Blakeney, induced the formation to float north in direction of the Blakeney Level Nature Reserve. Blakeney Reserve is a delegated no-fly space and so they have been approaching the zones marked for reasonable and extreme chook hazards. The coaching profile meant that they have been flying low, simply 110 toes above floor stage, which meant they have been liable to inflicting a noise disturbance in the event that they received too near populated areas.
The lead helicopter pilot moved the orbit 1.3 miles to the north, establishing a brand new “preliminary level” nearer to the shoreline. This stored them away from Blakeney Reserve and the recognized bird-hazard space. The brand new route stored them in an space marked with a “low” chook hazard ranking, but in addition handed over Cley Marsh, a part of a protected wildlife space.
They reached the brand new preliminary level and accomplished two full left orbits. Then they exited the orbits to fly east at 100 toes above floor stage at 110 knots indicated airspeed. The 2 helicopters maintained a 0.3 nautical mile separation, with the mishap helicopter positioned behind and to the left of the lead.
As they approached Cley Marsh, a flock of geese took to the air, possible startled by the noise of the engines. Inside a minute, the birds had climbed to a peak of 110 toes.
The Pave Hawk within the flight lead place, nonetheless about 0.3 miles forward, didn’t see the geese in any respect. However behind them, the rising geese collided with the opposite helicopter. That kind of goose weighs 6 to 12 kilos. At the very least three crashed by the windscreen and into the cockpit, knocking the pilot and co-pilot unconscious.
At the very least one goose struck the gunner within the open doorway, rendering the gunner unconscious. One other goose crashed into the nostril of the helicopter, disabling the Trim and Flight Path Stabilization programs. The Flight Path Stabilization system dampens modifications in pitch, roll, and yaw to maintain the plane secure in flight. Each of those parts are a part of the autopilot. With the autopilot disabled, the stick fell to the left.
At this level, the Pave Hawk was in a furiously harmful state: simply 110 toes above the bottom with the autopilot disabled and each pilots unconscious. It began to financial institution left till it hit a essential level and misplaced all vertical raise.
The one member of the crew who was nonetheless acutely aware was the flight engineer, who more than likely by no means even realised what was occurring. The report grimly notes that it takes 3.4 seconds for a human to understand and course of a sensory enter.
Three seconds elapsed from chook strike to the crash.
The Pave Hawk was destroyed on affect, killing all 4 crew members.
The entire crew have been carrying full helmets which have been designed to face up to a drive of 150Gs. The entire helmets have been cracked from the drive of the affect. Feathers have been discovered inside and outdoors of the helmets.
The report notes {that a} barely beneath common goose, weighing about 7.5 kilos, would affect with, as an oddly particular comparability level, 53 occasions the kinetic power of a baseball shifting at 100 miles per hour. The geese exceeded the design tolerance of each the windscreen and the helmets, delivering over 300 Gs of drive on affect.
America Air Power Plane Accident Investigation Board in the end concluded that the accident was brought on by a number of chook strikes – however supplied no contributing elements that might have mitigated the danger. They discovered no proof that the mission planning or supervision of the planning contributed to the mishap.
The crew have been briefed on the chook exercise within the areas, with up-to-date stories of chook exercise within the space. These referenced heightened chook exercise at nightfall, however as they have been working after nightfall, there was no cause to contemplate this a priority. The night time imaginative and prescient goggles restricted the crews’ visual view, which might have stopped them from seeing the geese retreating. However then, it’s unattainable to say that the geese would have been seen by the bare eye at midnight, not to mention whether or not there was time to do something about them.
It’s a brutal demonstration of simply how deadly a chook strike will be, destroying 4 lives and a $40 million plane in seconds. Finally, the Air Power can solely hope it doesn’t occur once more.
