On January 13, 2011, Air Canada Flight 878 departed Toronto for Zurich on a scheduled passenger service with 95 passengers, 6 flight attendants and 2 flight crew. After approximately three hours of flight time, the First Officer expressed a desire for a ‘controlled rest’ – a standard practice used in many (usually non-US) airlines that permits one pilot to effectively get a small amount of ‘sleep’. The procedures in place for controlled rest were not strictly adhered to with the FO sleeping for 75 minutes – well in excess of the 40 minutes as suggested by the company Flight Operations Manual. The FO woke up after the captain made a radio position report and was quickly appraised of opposite direction military traffic (that the captain was monitoring visually and on the Navigation Display). The first officer – somewhat confused, disorientated and situationally unaware, and suffering from REM-induced sleep inertia – mistook the planet Venus as an imminent collision and took evasive action. The captain immediately disconnected the autopilot and pulled back on the control column to regain altitude. It was at this time the oncoming aircraft passed beneath the Air Canada 767.
From the Transport Safety Board of Canada findings:
[T]he aircraft pitch changed from the cruise attitude of 2 degrees nose up, to 6 degrees nose down followed by a return to 2 degrees nose up. The vertical acceleration forces (g) went to −0.5 g to +2.0 g in 5 seconds. Computed airspeed increased 7 knots then decreased 14 knots before recovering to cruise speed with the aircraft’s altitude decreasing to 34 600 feet increasing to 35 400 feet and finally recovering to 35 000 feet.
Despite the illuminated seat belt sign, some passengers were not restrained and suffered minor injuries.
A relief pilot in the passenger cabin (that was to serve as a relief pilot for the return sector) was sensibly (and admirably) called to the flight deck to monitor the progress of the crew for the remainder of the flight.
Is it normal for Pilots to Sleep on the Flight Deck?
Despite what many people believe, it is normal for most airlines to have a strategic ‘controlled rest’ program in place as a genuine tool to mitigate the effects of fatigue. Strict procedures are usually put in place to ensure that the pilot only receives rest – not a deep sleep – and other actions are taken to ensure safe continuance of flight with what essentially becomes a single-pilot operation. It’s the FO’s lengthy “sleep” that was the single most obvious factor causing the incident.
What is Sleep Inertia?
Have you ever woken up after a sleep and responded to a situation that flowed from a dream? Have you ever woken up and not realised where you were (extremely common amongst airline pilots)? Have you ever woken up struggled to determine if it was a work day or day off? Sleep intertia is the post–sleep performance decrement and grogginess that occurs immediately after awakening. It’s essentially the continuance of a sleeplike state after you regain ‘consciousness’… and it poses a serious threat to the ‘controlled’ rest process.
Strangely, the exact purpose of the various cycles of sleep are largely unknown. What is known, however, is that REM (Rapid Eye Movement) sleep is the deepest sleep and is most likely to cause short-term performance deteriorations if woken.
REM Sleep: Stages (vertically) and hours (horizontally)
Non-REM dreams (during the first 40-60 minutes of sleep and then staggered thereafter) are more likely to consist of brief, fragmentary impressions that are less emotional, less vivid, and less likely to involve visual images than REM sleep dreams. If woken up during periods of REM sleep, it’s possible that the vivid imagery might translate to the woken state and cause the pilot to carry his sleeping thoughts into the real world. It’s believed that stage four sleep is also quite vivid and is the phase of sleep most responsible for nightmares. These deep stages or sleep should be avoided on the flight deck. Controlled rest is normally limited to 20-30 minutes for most carriers to ensure that the pilot avoids any REM cycle. In fact, most physiologists suggest pilots avoid anything beyond stage 2 sleep.
Video: This video shows a dog reacting to sleep inertia [Credit: YouTube user MarinaHD2001].
From the TC report:
With a view to providing a substantial rest, the captain allowed the FO to rest beyond the 40–minute maximum set as a defence against entering slow–wave sleep; the 75–minute rest that ensued increased the probability of entering slow–wave [REM] sleep. The severity and duration of sleep inertia are more likely to be worse if a person is awakened from slow–wave sleep, especially if the rest occurs at a circadian low and when the person is fatigued. Given the consistency between the conditions that worsen sleep inertia and the FO’s sleep and controlled rest, and the observation that the FO felt unwell when awakened, it is likely that the FO was suffering from high levels of sleep inertia.
In a post-incident interview with the captain and other crew working for the airline, it was identified that staff generally had a poor understanding of the dangers involved with lengthy controlled rest (suggesting a sub-par human factors and CRM program). The airline subsequently issued bulletins to crew alerting them to published procedures.
This incident barely scratches the scratch relating to broader and more relevant fatigure related issue & discussions.
The situation could have been worse. Consider a situation where a pilot woke in a state where he believed he was responding to an emergency. He might pull engine switches, fire handles or – not dissimilar to the situation described above – aggressively handle the aircraft in such a way that it causes serious controllability issues.
Controlled rest seems to be largely misunderstood by the travelling public. Remember the photo of a sleeping Cathay Pacific captain in 2011?
Cathay quickly responded to the clueless news reports with a statement that read, in part, “This photograph should not be taken out of context as it would appear to illustrate ‘controlled rest’, which occurs in cockpits of many of the best airlines in the world. This includes Cathay Pacific, which allows controlled rest under strictly controlled conditions, which permit one pilot of a two-crew aircraft, to take a short rest during low workload periods during the cruise only… the controlled rest period would have lasted 40 minutes at most, during which time the co-pilot would have full control.”
If you’re a passenger, how do you respond to the idea of “controlled rest”? If you’re a pilot, what measure to you or your airline take to combat fatigue?
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About Marty
I thought it was common knowledge that pilots slept during the flight…I knew this when I was like 5.
No big deal for me
The post is well written and a good read. Thumbs up for your work!