UK S-92 Near-CFIT Highlights Hazards of MVFR Flight

 - July 12, 2021, 7:36 AM
An investigation into a 2019 near-accident involving a Sikorsky S-92 by the UK's Air Accidents Investigations Branch shows many similarities to the crash that claimed the lives of former basketball superstar Kobe Bryant and eight others just three months later.

A UK Air Accidents Investigations Branch (AAIB) final report found that VFR flight into instrument meteorological conditions (IMC) lead to a Sikorsky S-92A operated by Starspeed nearly crashing next to a house, with a subsequent recovery that inflicted 131 percent torque on the engines. The event occurred early on the evening of Oct. 14, 2019, on a flight from Birmingham Airport to a private landing site in northern Cotswolds. There were two pilots and nine passengers on board. 

While the helicopter ultimately arrived at its destination, the circumstances are eerily similar to the one that killed former NBA star Kobe Bryant and eight others near Calabasas, California, in January 2020. Namely, a crewmember feeling pressure to satisfy the need of a client to reach his destination and continue a VFR flight into marginal VFR (MVFR) and ultimately IFR conditions. The latter was also encountered in an area of rising terrain with a subsequent loss of pilot orientation to the ground, loss of location orientation, and spatial disorientation, while continuing to hand fly the aircraft as opposed to engaging the onboard automatic flight control system. Encroaching local sunset also played a role in this incident, but was not a factor in the Calabasas accident.

Throughout the report, evidence emerged of a captain—the pilot flying—unsure and anxious about deteriorating weather conditions both before and during the flight, a reluctance to engage automation, and heavy completion bias to press on into deteriorating conditions. Meanwhile, the copilot, while expressing multiple doubts about continuing the flight, continued to repeatedly, albeit tacitly, affirm the captain’s rapidly failing decision chain. All the while the approach parameters of the flight became increasingly unstable in terms of pitch, heading, and airspeed. 

Before the flight took off, the captain confided in the copilot that “we are really up against it” in terms of encroaching cloud cover and fading daylight, while the actual weather conditions at nearby airports were even worse than forecast. Birmingham reported a broken base at 800 agl, which would lower to 400 during the day, Gloucestershire reported a broken base at 800 to 900 feet, with patches down to 400 agl, and Oxford reported a base of 600 feet, declining to 400 to 500 feet during the day. While there was no formal weather reporting at the landing site, the estate manager reported to the copilot just before the flight’s departure that the weather was “closing in” and that the tops of nearby radio towers could not be seen. 

During the first four minutes of the flight, the helicopter progressively descended to avoid cloud bases, but initially maintained 500 feet agl. But as the flight progressed, the crew was treated to a crescendo of altitude warnings from the radar altimeter and terrain warnings from the HTAWS. The crew also became confused about selection of waypoints in the FMS.

Altitude deteriorated to 200 feet, then 100 feet agl, and ultimately 28 feet agl, while airspeed dropped to 35 knots. The crew could not visually locate the landing site on the first approach. According to the AAIB report, “The pitch attitude, and consequently airspeed, of the helicopter were unstable. It then yawed 30 degrees to the left and climbed, with nose-down pitch attitude, in response to collective input by the [captain].” 

The captain called go-around. And then, according to the AAIB, he “rapidly raised the collective resulting in the ‘low rotor’ aural warning, and engine torque increasing to 131 percent. The helicopter initially achieved a positive rate of climb but then continued a more level acceleration, as the pitch attitude of the helicopter remained below the horizon. As a result, it flew along a level flight path at less than 300 feet agl. In response to deviation calls by the copilot, the [captain] raised the attitude of the helicopter significantly above the horizon achieving a high rate of climb, as the airspeed reduced back to under 10 knots.” 

Instead of returning to Birmingham or diverting to an alternate—which had not been pre-flight planned—the crew opted to retry the approach, this time using a Dragon GL3 portable landing aid that had been placed at the landing site. But the captain rejected the copilot’s suggestion to use automation—in the form of the onboard automatic flight control system—for the second try, a direct violation of the company’s operations manual given the conditions, and a potentially fatal mistake that became apparent shortly after the helicopter headed back to the initial point (IP) of the approach.

Altitude deviated by up to 300 feet, airspeed and pitch again fluctuated, and heading varied up to 45 degrees on either side of the approach track. The copilot suggested a return to Birmingham, to which the captain responded, “I’m just going to...err...try one more mile.”

Two and half miles from the landing site and at 800 feet agl the captain said, “It’s not going to happen” and called go around but then pressed on to the landing site anyway. The pitch was minus 10 degrees and the helicopter was descending at 1,000 fpm. Finally, the copilot spoke up, saying, “I’m not happy with this.” 

The captain replied with a series of “gotchas” but still pressed on. Ten seconds later, at 500 feet agl, the captain called the landing light in sight. The approach stabilized and the helicopter landed without further incident. But the over-limiting of the engines was immediately reported and the helicopter was later flown to Stansted on a ferry permit for a series of inspections. The flight was reported to the AAIB, which deemed the incident serious and opened an investigation. 

According to the AAIB, there were a series of problems with the flight, including lack of standard operating procedures for altitude alert settings and stabilized approach criteria, as well as a lack of effective crew communications, customer bias inconsistent with flight safety, and crew uncertainty with landing rules. The agency stressed the need for the creation of more point-in-space approaches at helicopter landing sites and the overall need for greater awareness with regard to helicopter operations in areas of degraded visual conditions. It also suggested greater use of flight data monitoring for onshore operations.