Did a pilot’s search for adventure lead to tragedy instead?
Aviation is exhilarating. The career paths that make up the industry’s pilot pipeline couldn’t be sustained if it weren’t. The steep expense of initial training, the long hours and low pay of flight instruction, the tedium and hazards of pipeline patrol, air tours, and offshore shuttles are all made tolerable by the innate joy of flight. If pilots occasionally indulge in the taste for the thrills that originally attracted them to flight training, well, that’s only human nature.
Of course, most of what’s considered safety culture consists of thwarting human nature, or at least restricting its scope for circumventing the rational mind’s efforts at risk assessment and mitigation. That’s the reasoning behind standard operating procedures that remove as many decisions as possible from the individuals who actually operate the aircraft.
N74137 was an Airbus AS350 B3 air ambulance operating from Air Methods’ local base in Globe, Arizona. Early in the afternoon of December 15, 2015, it was dispatched to transport a cardiac patient from Globe to Mesa. The flight was crewed by a pilot, flight nurse, and flight paramedic. Conditions were characteristic of the Phoenix area in December: clear skies, light northwest winds, and essentially unlimited visibility.
The flight was short, about 25 minutes, and the patient remained stable throughout. After unloading him, the helicopter refueled at Phoenix-Mesa Gateway Airport (KIWA) before departing for home.
Data recovered from the aircraft’s onboard Appareo GAU2000 data logger, which obtained position and altitude data from its own internal GPS and airspeed and altitude readings from the helicopter’s pitot-static system, showed the helicopter initially traversing the area around Gold Canyon at about 500 feet above ground level (agl). As it approached the Superstition Mountains heading east-northeasterly, it climbed enough to begin skimming over the hills at altitudes ranging from more than 1,000 feet above the valley floors to as little as 240 feet above the peaks.
During the last three minutes of the flight it flew even lower, remaining below 800 feet agl and crossing ridgelines with less than 50 feet to spare. After traversing the rim of Rogers Canyon just 30 feet above a saddle, the ship descended and accelerated, following the canyon floor. Ground speed reached 148 knots at an altitude of no more than 300 feet agl as the helicopter tracked toward the next ridge.
The flight paramedic later recalled hearing the pilot say, “Oh, shit” and seeing him making “jerky fast hand movements” on the controls. After a hard right bank the paramedic likened to “try[ing] to do a U-turn at 60 miles an hour,” the aircraft hit the next ridgeline just below another saddle point at an altitude of 5,035 feet. It was 5:23 p.m.
The 51-year-old commercial pilot had logged 5,670 hours in a 25-year flying career. He was the Globe base’s safety officer, a role that the paramedic said he “took very seriously.” The pilot was well liked by his teammates, in part because of his willingness to help clean the aircraft and equipment after transports. The paramedic also described him as liking to fly lower than their other pilots, but “not like dangerously low or anything.”
The paramedic also mentioned the pilot’s service in the US Army, as did other flight crew at the Globe base. It would appear, however, that he didn’t fly for the army. His résumé cited no military flight experience, and the file assembled during the National Transportation Safety Board (NTSB) investigation includes his honorable discharge with the explanation “Failure to qualify for flight training – no disability.” His civilian medical certificate required the use of corrective lenses.
The Flight Controls
The NTSB’s report makes particular note of the phenomenon of servo transparency, a condition in which the aerodynamic loads generated by the main rotor system exceed the forces produced by the aircraft’s hydraulic system. The difference “is transmitted back through the pilot’s collective and cyclic controls” and increases rapidly, potentially creating the impression that the controls have jammed. On helicopters like the AS350 with clockwise-turning main rotors, “it results in a right and aft cyclic motion accompanied by down collective movement.”
The amount of feedback is proportional to the severity of the maneuver that instigates it, but it “normally lasts less than 2 seconds when the pilot is aware of the conditions and relaxes the pressure on the controls”—not the most natural reaction to a mountain ridge rushing toward you at 250 feet per second. The paramedic’s impression of the flight’s final seconds was “Hard right. Lost altitude fast. See it coming. Then we just hit …”
Search and Rescue
The helicopter’s emergency locator transmitter was undamaged but did not activate … until the wreckage was moved onto a flatbed trailer during recovery.
The flight was tracked by satellite, but the staff at the national communications center failed to notice its disappearance for more than two hours. Some time after 7:30, they alerted Air Methods’ Operations Control Center, which launched a search. Company aircraft located the accident site at about 8:30 p.m., but because of the steep terrain and limited access had to summon another helicopter with hoist equipment to lower medics to the scene. The first rescuers reached the victims at 9:54, four and a half hours after the crash.
The pilot had stopped breathing shortly after impact. The paramedic found himself hanging in his straps outside the high side of the wreckage. His glasses and helmet “were gone.” He cut himself free with his trauma shears and dropped to the snow, falling into a stream of fuel leaking from the ruptured tanks. The flight nurse was conscious but badly hurt, pinned under the wreckage with the right skid across his throat and jaw. The paramedic’s own injuries left him unable to walk. They tried to use their mobile phones but couldn’t get a signal.
Temperatures dropped rapidly after the sun set, and both men began suffering from hypothermia. The flight nurse diagnosed himself with a collapsed lung, but his aspiration needles were in a pocket of his flight suit that was out of reach beneath the wreckage. His breathing became increasingly labored until he succumbed.
His autopsy showed multiple rib fractures with a left-sided flail chest (a serious condition where a segment of the rib cage becomes detached from the chest wall) and significant internal bleeding from intraabdominal injuries. His Injury Severity Score was graded as 22 (severe), and the NTSB concluded that “it is unlikely that he would have survived until help arrived even if the initial notification of the crash had occurred more rapidly.”
The paramedic was eventually able to signal the search aircraft with the light on his mobile phone. He survived and provided investigators with his account of the flight.
It should go without saying: the purpose of satellite tracking is to guarantee immediate response when an aircraft can’t be accounted for. A prompt initiation of search-and-rescue efforts might have located the wreckage before sunset, making it easier for rescuers to reach the scene and minimizing hypothermia. Interviews with staff at the communications center suggested that unusually heavy volume in her sector might have overloaded the relatively inexperienced specialist tracking the flight, the kind of single-point failure institutional systems are presumably designed to prevent.
But of course there’d have been no need for search or rescue had the pilot chosen to cross the mountains at a conservative 1,000 feet above the peaks. Skies were clear, and the altitude records set by the AS350 B3 include landing on the summit of Mt. Everest, so neither the meteorological nor service ceiling was a factor.
From outside, one can see no practical reason to risk the ship and its crew by zipping 30 feet over ridgelines and racing down canyons at 150 knots. But as the paramedic recalled, “Each pilot has their own little route … I say they’re like surfers. They have their own little way they do things.” The accident pilot’s preferred route to Globe from the west passed “some rock formations … he just liked to fly by.”
Three days after the accident, Air Methods’ chief pilot issued a critical bulletin announcing a zero-tolerance policy for violations of the minimum VFR altitude standards set by the company’s General Operations Manual. Increasing consumer sales of unmanned aerial vehicles (drones) were cited as a reason.