Pilot Incapacitation is the term used to describe the inability of a pilot, who is part of the operating crew, to carry out their normal duties because of the onset, during flight, of the effects of physiological factors.
Death is the most extreme example of incapacitation, usually as a result of a heart attack, but is not necessarily the most hazardous. Although most recorded deaths of operating pilots in flight have been found to be due to cardiovascular disease, by far the most common cause of flight crew incapacitation is gastroenteritis.
Incapacitation may occur as a result of:
- The effects of Hypoxia (insufficient oxygen) associated with an absence of normal pressurisation system function at altitudes above 10,000 ft.
- Smoke or Fumes associated with an Fire in the Air or with contamination of the air conditioning system.
- Gastro-intestinal problems such as severe Gastroenteritis potentially attributable to Food Poisoning, or to Food Allergy.
- Being asleep.
- A medical condition such as a heart attack, stroke or seizure, or transient mental abnormality.
- A Bird Strike or other event causing incapacitating physical injury.
- A malicious or hostile act such as assault by an unruly passenger, terrorist action or small arms fire, or possibly malicious targeting of aircraft with high powered lasers by persons on the ground.
Unless the incapacitation occurs on a single pilot operation, incapacitation of one pilot may not be immediately obvious, become only progressively evident, or escape notice altogether until an unexpected absence of response or action occurs.
Clearly, if the single pilot of a small aircraft becomes incapacitated then the safety of the flight is liable to be severely compromised and Loss of Control may result. However, for the two pilot case typical of larger transport aircraft, incapacitation of only one of the pilots is unlikely to present a significant risk given the attention which pilot training, especially for low minima precision approaches, is usually required to give to the implications of single pilot incapacitation.
Loss of Separation may be a secondary effect of total crew incapacitation or side effect of the additional workload imposed upon the remaining crew member(s).
The key to avoiding serious problems from the incapacitation of one pilot in a multi crew aircraft is the availability of appropriate SOPs and recurrent training which includes practice in their use.
Correct control of both the aircraft pressurisation system and, if necessary, use of the emergency oxygen supply will both prevent Hypoxia and protect the crew from the effects of Smoke and Fumes. Therapeutic Oxygen supplies can also alleviate the condition of a crew member or passenger suffering a medical condition. Staggering crew meal times and ensuring that each pilot eats different meals both prior to and during flight, will usually prevent both pilots becoming incapacitated due to Food Poisoning and is currently common practice. Intentional sleep whilst on the flight deck may be relevant on long haul flights but should only take place if an appropriate SOPs exists and is followed.
The first indication that a controller might get of total flight crew incapacitation is Loss of Communication. Having tried all means, without success, to contact the aircraft, it is extremely difficult for a controller to ascertain what is happening on an aircraft. If the aircraft autopilot is engaged then it will be likely to follow the flight plan route towards the destination. Conforming with standard loss of communication procedures, military aircraft can be tasked to intercept the aircraft and inspect it visually but there is little that a controller can do other then ensure the safety of surrounding traffic by maintaining separation.
Accidents & Incidents
Events on the SKYbrary Database which list Incapacitation as a causal factor:
On 29 October 2019, an Airbus A321 was descending towards its destination, Kaohsiung, when the First Officer suddenly lost consciousness without warning. The Captain declared a MAYDAY and with cabin crew assistance, he was secured clear of the flight controls and given oxygen which appeared beneficial. He was then removed to the passenger cabin where a doctor recommended continuing oxygen treatment. On arrival, he had fully regained consciousness. Medical examination and tests both on arrival and subsequently were unable to identify a cause although a context of cumulative fatigue was considered likely after three consecutive nights of inadequate sleep.
On 27 September 2017, a Boeing 777-200LRF Captain left the flight deck to retrieve their crew meal about 40 minutes after departing Abu Dhabi but whilst doing so he collapsed unconscious in the galley and despite assistance subsequently died. A MAYDAY was declared and a diversion to Kuwait successfully completed by the remaining pilot. The Investigation determined that the cause of death was cardiopulmonary system collapse due to a stenosis in the coronary artery. It was noted that the Captain’s medical condition had been partially concealed from detection because of his unapproved use of potentially significant self-medication.
On 21 January 2019, a Piper PA46-310P en-route north northwest of Guernsey was reported missing and subsequently confirmed to have broken up in flight during an uncontrolled descent. The Investigation found that neither the pilot nor the aircraft involved were able to be used for commercial passenger flight operations but also found that although the direct cause of loss of control was unproven, it was most likely the consequence of carbon monoxide poisoning originating from an exhaust system leak. The safety implications arising from operation of private flights for commercial passenger transport purposes contrary to regulatory requirements were also highlighted.
On 15 August 2016, the cognitive condition of an Airbus A320 Captain deteriorated en-route to Riga and he assigned all flight tasks to the First Officer. When his condition deteriorated further, an off duty company First Officer travelling as a passenger was invited to occupy the flight deck supernumerary crew seat to assist. Once descent had commenced, the Captain and assisting First Officer swapped seats and the flight was thereafter completed without any further significant event. The Investigation concluded that the Captain’s serious physical and mental exhaustion had been the result of the combined effect of chronic fatigue and stress.
On 4 February 2020, an Airbus A350-900 initiated a go around from its destination approach at 1,400 feet aal following a predictive windshear alert unsupported by the prevailing environmental conditions but the First Officer mishandled it and the stop altitude was first exceeded and then flown though again in a descent before control as instructed was finally regained four minutes later. Conflict with another aircraft occurred during this period. The Investigation concluded the underlying cause of the upset was a lack of awareness of autopilot status by the First Officer followed by a significant delay before the Captain took over control.
On 15 August 2018, a Boeing 737-300SF crew concerned about a small residual pressure in a bleed air system isolated after a fault occurred en-route then sought and were given non-standard further troubleshooting guidance by company maintenance which, when followed, led directly and indirectly to additional problems including successive incapacitation of both pilots and a MAYDAY diversion. The Investigation found that the aircraft concerned was carrying a number of relevant individually minor undetected defects which meant the initial crew response was not completely effective and prompted a request for in-flight assistance which was unnecessary and led to the further outcomes.
On 17 November 2017, an Airbus A320 flight crew were both partially incapacitated by the effect of fumes described as acrid and stinging which they detected when following another smaller aircraft to the holding point at Geneva and then waiting in line behind it before taking off, the effect of which rapidly worsened en-route and necessitated a precautionary diversion to Marseilles. The very thorough subsequent Investigation was unable to determine the origin or nature of the fumes encountered but circumstantial evidence pointed tentatively towards ingestion of engine exhaust from the aircraft ahead in one or both A320 engines.
On 31 December 2017, a de Havilland DHC2 floatplane being manoeuvred at low level over Jerusalem Bay shortly after takeoff was observed to enter a steeply banked turn from which it appeared to depart controlled flight and impact the water surface below almost vertically. The Investigation concluded that the aircraft had stalled despite the exemplary proficiency record of the pilot and that in the absence of any other plausible explanation found that the loss of control was likely to have been the effect of an elevated exposure to carbon monoxide found during post mortem toxicology testing.
On 23 September 2019, the flight crew of an Airbus A320 on approach to London Heathrow detected strong acrid fumes on the flight deck and after donning oxygen masks completed the approach and landing, exited the runway and shut down on a taxiway. After removing their masks, one pilot became incapacitated and the other unwell and both were taken to hospital. The other occupants, all unaffected, were disembarked to buses. The very comprehensive investigation was unable to establish the origin of the fumes but did identify a number of circumstantial factors which corresponded to those identified in previous similar events.
On 20 August 2011, a RAF Aerobatic Team Hawk failed to complete a formation break to land near Bournemouth and the aircraft flew into the ground, destroying the aircraft and killing the pilot. The subsequent Inquiry concluded that the pilot had become semi conscious as the result of the sudden onset of G-induced impairment characterised as A-LOC. It was found that the manoeuvre as flown was not radically different to usual and that the context for the accident was to be found in a range of organisational failures in risk management.
On 6 July 2011 the First Officer of a Ryanair Boeing 737-800 was suddenly incapacitated during a passenger flight from Pisa to Las Palmas. The Captain declared a medical emergency and identified the First Officer as the affected person before diverting uneventfully to Girona. The subsequent investigation focused particularly on the way the event was perceived as a specifically medical emergency rather than also being an operational emergency as well as on the operator procedures for the situation encountered.
On 30 September 2018, an Airbus A319 Captain had to complete a flight into Glasgow on his own when the First Officer left the flight deck after suffering a flying-related anxiety attack. After declaring a ‘PAN’ to ATC advising that the aircraft was being operated by only one pilot, the flight was completed without further event. The Investigation found that the First Officer had been “frightened” after the same Captain had been obliged to take control during his attempted landing the previous day and had “felt increasingly nervous” during his first ‘Pilot Flying’ task since the event the previous day.
On 13 April 2015, a Swearingen SA226 Metro II which had recently departed on a cargo flight was climbing normally when it suddenly entered an unexplained and steep descent a few minutes after takeoff. There were no communications from the pilots. It was later found to have impacted terrain after a rate of descent exceeding 30,000 fpm had created aerodynamic forces which caused structural disintegration to begin before impact. The Investigation could not determine why but concluded that “alcohol intoxication almost certainly played a role” and noted that indications that the Captain was a chronic alcoholic had not prompted any intervention.
On 3 October 2015, the pilot of a Beech Super King Air on a business flight lost control in IMC shortly after take-off and the aircraft subsequently impacted terrain at high speed. The Investigation concluded on the balance of probabilities that pilot medical incapacitation was likely to have occurred. It was noted that the aircraft had not been fitted with TAWS nor was it required to be but it was found that alerting from such a system would have increased the chances of the only passenger, another professional pilot, successfully taking over and three corresponding Safety Recommendations were made.
On 5 September 2015, a Boeing 737-800 was about to commence descent on a non-precision final approach at Porto in VMC when a green laser was directed at the aircraft. The Pilot Flying responded rapidly by shielding his eyes and was unaffected but the other pilot looked up, sustained flash blindness and crew coordination was compromised. Subsequently, the approach became unstable and a go around to an uneventful approach to the reciprocal runway direction was completed. The subsequent Investigation noted the use of increasingly powerful green lasers in this way and that such use was not contrary to Portuguese law.