Tail-End Ferry Fatigue: Get-Home-Itis Is Not The Only Factor

In September, the NTSB published a Final Report on an accident with a very simple determination of probable cause: “The pilot’s loss of helicopter control as a result of fatigue during cruise flight at night.”

The flight was a “tail-end ferry flight.” Unlike FAR Part 121 operations, Part 135 charter operators have no rest requirements for a Part 91 repositioning flight at the end of the day. Part 91 flights at the beginning of the day or between Part 135 flights are counted, but the tail-end ferry flight home can extend a pilot’s flight and duty time. It can’t be counted as “rest,” so the pilot would need the required rest before starting the next Part 135 day.

Tail-end ferry flights have been a part of the charter world since the original charter rest and duty rules were written. It has been confirmed by numerous FAA Legal Interpretations. In 2003, I served on an Aviation Rulemaking Committee (ARC) that sought to eliminate tail-end ferry flights as part of a comprehensive overhaul of outdated rest and duty regulations. The ARC’s recommendations never made it to the Notice of Proposed Rulemaking (NPRM) stage. Now I serve on another ARC with the same goal of drafting enforceable, science-based rest and duty regs that fit the on-demand nature of the charter world.

So, what does this recent tail-end ferry accident tell us? Would new regulations have prevented it? Here are the facts: It was an air ambulance helicopter, a Eurocopter AS350B2, with one pilot and two emergency medical service crewmembers aboard. They took off about 2107 on the final flight. It was night, but visual conditions prevailed. Prior to this flight, they had flown three others for a total of 94 min. of flight time over a period of 2.5 hr.

Shortly after takeoff, the pilot asked the crewmembers whether they were “alright.” One crewmember responded, “Yup” and then asked, “Question is are you alright up there?” The pilot responded, “Uhhh, think so. Good enough to get us home at least.” There was no further discussion related to fatigue.

During the flight, the pilot adjusted his seat position and flexed his legs, which were actions consistent with signs of fatigue. Also, although he participated in the medical crewmembers’ conversations in the middle of the flight, he did not near the end. During the last portion of the flight, the helicopter entered a progressively steepening right bank, and the pilot did not respond as the medical crewmembers shouted his name. The helicopter descended and became inverted, and the pilot continued not to respond as the medical crewmembers shouted his name.

After the helicopter began to roll to the right, the pilot slumped to the left, appearing incapacitated. The crash occurred at approximately 2250. 

The pilot and the two crewmembers were killed.

On the day of the accident, April 26, 2018, cellular telephone activity revealed two possible opportunities for the pilot to sleep before going on duty, but it is not known if he rested during those times. Thus, the pilot could have been awake for about 15.5 hr. at the time of the crash (based on telephone records showing activity at 0725 that morning) if he did not take advantage of the sleep opportunities.

The NTSB stated: “Although this time since awakening would not be considered excessive, this accident shift was the pilot’s first after returning from a week-long vacation during which his circadian rhythm would have had him sleeping. Further, the environment created by the helicopter vibration, darkness of night, and few operational demands during the cruise phase of flight would have increased the pilot’s fatigue and the body’s biological desire to sleep.”

There is little doubt that this experienced pilot simply fell asleep. But why? This accident did not happen simply because the current regulations allow tail-end ferry flights. The cruel irony of this accident is the pilot was coming off a week of vacation. The NTSB mentioned time-zone change, but the pilot, who was based in Wisconsin, simply took a week in Florida. A 1-hr. time-zone change was not a major factor. A bigger factor: circadian rhythms.

Pilots were talking about the dangers of flying “on the back side of the clock” long before scientists coined the phrase “Window of Circadian Low” (WOCL). This pilot switched to sleeping nights for a week. Then he gave himself a day to switch to becoming a night pilot. But the crash occurred before 11:00 p.m. He didn’t make it to the backside of the clock. The WOCL for people adapted to a usual day-wake/night-sleep schedule begins around 2:00 a.m.

Part 135 needs enforceable, science-based rest and duty regulations. They do need to address the dangers of tail-end ferry flights, but more importantly, they need to introduce fatigue management principles so that pilots and operators better understand the risks of quickly changing their days to nights.