Flight Crew Continues VFR Flight Into IFR Conditions

Alaska accident uncovered many real world problems facing Alaskan flight operations.

cessna caravan
A Cessna Caravan similar to the accident aircraft.Textron Aviation

A Cessna Caravan 208B on a Part 135 daylight VFR trip between Quinhagak, Alaska (PAQH) and Togiak, Alaska (PATG), slammed into the side of a hill about 10 nm northwest of its destination after encountering IFR conditions along the route. The aircraft was operated by Hageland Aviation Services Inc, dba Ravn Connect, as flight 1133. The October 2016 accident claimed the lives of both pilots and the lone passenger aboard. Both pilots held commercial pilot certificates with an instrument rating. At the time of departure from PATG, local weather reported calm wind, visibility 9 miles, light rain, with scattered clouds at 1,400 feet agl and an overcast at 4,400 feet agl. The temperature was 8°C.

Flight 1133 was equipped with Spidertracks, that provided near real-time flight tracking data transmitted at 6-minute intervals via Iridium satellites to an internet-based storage location. Hageland used the data as one means of tracking its flights. The ADS-B aboard flight 1133 was inoperative on the day of the accident. Hageland flights were not equipped with any other onboard flight tracking systems.

The accident flight departed AQH at approximately 11:33 local time and proceeded southeast toward PATG at about 1,000 feet msl (AQH field elevation is 42 feet). The airplane’s last recorded location, at 11:53, was about 19 nm northwest of PATG at an altitude of 1,043 feet msl. Flight 1133 struck the hill at an altitude of 2,300 feet, just a few hundred feet below the 2,500-foot peak in the area. While Hageland aircraft included terrain avoidance and warning system software, that system was inhibited on flight 1133 at the time of the accident, robbing the crew of valuable situational awareness information.

Much of what was not originally known about flight 1133 was developed from eye-opening interviews with the crew of a second Hageland flight crew, consisting of a PIC and a safety pilot in another Caravan that departed PAQH about 2 minutes after the accident flight. According to Spidertracks and automatic dependent surveillance-broadcast (ADS-B) data for the second airplane, that crew flew a route initially similar to the route and altitude of the accident flight.

Data showed that as the second flight approached the mountainous terrain, at 11:56, it diverted south to remain over lower terrain than the route the accident flight followed. The PIC of the second flight later told investigators that after seeing poor weather conditions ahead, he turned away from the higher hills as they approached Togiak in order to head towards generally better weather. Why the crew of the first Caravan continued on into an area of higher terrain in poor weather rather than either turning around or at least turning south toward lower terrain is unknown.

The NTSB's 20-month investigation into the accident initially pointed to the flight crew for failing to avoid the unexpected IFR weather as they approached Togiak, as well as for failing to exit IFR conditions once they encountered them.

terrain inhibit switch
NTSB discovered it is easy for pilot to forget to re-engage TAWS.NTSB

The NTSB did not let Hageland Aviation Services Inc. off the hook, citing the company’s tacit pilot approval of a terrain inhibit switch that many crews used to avoid nuisance alerts enroute when the aircraft operated below 1,000 feet msl. The Board also cited Hageland’s poor crew resource management and CFIT training. Despite regular operations in mountainous terrain, the FAA surprisingly did not require Hageland to conduct CFIT training at all. Hageland’s training programs had been the focus of both FAA and NTSB concern during the 4 years before this accident, resulting from five previous accidents and a runway excursion incident involving Hageland flights during a 16-month period between December 3, 2012, and April 8, 2014. The NTSB also pointed to the FAA’s failure to ensure Hageland’s CRM training included all the elements required under Part 135.

Specifically, the NTSB questioned the lack of a requirement for effective TAWS protections and nuisance-alert mitigations for flights that operate under VFR at altitudes below the TAWS normal altitude limits. As designed, once the terrain inhibit switch was pushed to inhibit the TAWS alerts, a pilot would have to push the switch again to un-inhibit the alerts. Remembering to un-inhibit the system requires the pilot to adequately monitor the situation and perform the action at the intended time. However, research has shown that pilots can forget to perform an action due to multitasking, distraction, task interruption, absence of cues, or poorly formed intentions in memory. (add terrain switch photo here)

Hageland training did not include specific guidance to crews about how to effectively work with the TAWS inhibit switch. While other air carriers also operate with similar terrain inhibit switches in the cockpit, the Board issued Safety Recommendation A-17-35, which asked the FAA to implement ways to provide effective TAWS protections while mitigating nuisance alerts for single-engine airplanes operated under Part 135 that frequently operate at altitudes below their respective TAWS class design alerting threshold.

At the time of the accident, Hageland did not have a process to collect and review flight data to identify deviations from standard operating procedures and regulations and other potential safety issues. The company has since begun installing monitoring equipment on its fleet that will enable the carrier to identify risk trends and to take corrective action before an accident occurs.

Flight 1133, as well as other Hageland aircraft, were not equipped, nor were they required to be equipped, with a crash-resistant flight recorder systems capable of capturing cockpit audio and images of the instrument panel and pilot’s forward view. Thus, investigators lacked information about the dynamic aspects of the weather the flight crew faced, visual cues of deteriorating weather and how the flight crew reacted to the developing situation and worked together. Such information would have benefited the investigation and provided the details needed to determine the most effective countermeasures to prevent future accidents.

Finally, the Board cited the need for improved ATC infrastructure to support low-altitude instrument flight rules (IFR) operations in Alaska. The crew of the second Caravan told investigators that many flights operate in the region under VFR because it is much easier than flying in the IFR system. Hageland and FAA personnel described that communications and weather-reporting limitations could not support IFR operations in many areas in Alaska.