On June 4, 2023, N611VG became a ghost plane flying over the DC restricted airspace and Virginia before crashing into mountainous terrain in southwest Virginia after six F-16s intercepted the plane but failed to establish contact the pilot.
The fact that the pilot was unresponsive leads to the public speculation that the Citation lost cabin pressure at 34,000 feet. This accident can be seen very similar to the 2022 Baltic Sea crash where a Cessna Citation II spiral dived into the Baltic Sea after fuel exhaustion caused by likely loss of cabin pressure at cruising altitude, and on Helios Airways Flight 522 where everyone onboard was incapacitated due to the crew's failure to set the cabin pressurization before takeoff.
Another speculation is that the single pilot had become unconscious due to medical reasons, and other passengers were unable to assist.
What is Loss of Cabin Pressurization?
A loss of cabin pressurization could be caused by structural failure or pressurization system failure, leading to hypoxia if oxygen is not immediately used. Based on 14 CFR Part 91.211 regarding supplemental oxygen use for general aviation operations, flight crew must use oxygen above 12,500 ft MSL after 30 minutes, and at all times above 14,000 ft MSL. Above 15,000 ft MSL, oxygen must be provided to each occupant of the aircraft. For Part 135 (commuter and on-demand operations) and Part 121 (scheduled air carrier operations), the crew does not need to use oxygen below FL 410 if each has a quick-donning mask, which must be put on under 5 seconds with one hand.
Time is the problem here. If cabin pressurization is lost around 35,000 feet, the time of useful consciousness (TUC) for a person is less than 30 seconds. The scary part is that pilots will never know the actual TUC that has elapsed. Judgment is impaired for someone who is experiencing hypoxia, and they may not recognize the gravity of the situation anymore after the first few seconds. It is not anymore about how fast the pilot can put on the quick-donning mask. The reaction-decision time must also be accounted for, potentially along with the time spent looking at indications of the problem on the cockpit displays and dealing with other distractions such as calming the passengers. If time is incorrectly spent within the first few seconds after cabin pressurization is lost, the crew may fail to make rational and life-savings decisions before it becomes a ghost plane.
In a controlled environment, anyone could easily put on the mask in under 5 seconds with one hand while sitting on the ground. With stress, however, two of the hazardous attitudes in aviation are likely to take over – invulnerability and resignation. It takes time for the pilot to accept an actual emergency, and in the case of hypoxia, it is easy for the pilot to give up trying after judgment is impaired.
A Solution to Loss of Cabin Pressurization
One solution to this problem is to install automatic-donned oxygen masks that are designed to cover the pilot's faces automatically when the loss of cabin pressurization is detected, which would isolate human factor. If solutions similar to this is implemented in Part 91, 121, and 135 operations, pilots do not need to worry about their time of useful consciousness anymore. This device could also be implemented above passenger seats on airliners, which can be especially useful for people who don't pay attention to the safety video before flight.
Another Probable Cause: Single Pilot Incapacitation
According to the reports, no one was on the right seat of the flight deck along with the captain. It is probable that the captain of N611VG had passed out and the other three passengers were unable to assist with operations. However, it is unclear as to why they did not notice the unusual 180 turn and the distance it has flown past their destination, as well as the flares that the F16s used. The Cessna 560 Citation V is certified for single-pilot operations, and it is a lot riskier than jets that require two pilots for operations for this reason. Pilot incapacitation due to medical reasons have been seen before, such as on American Airlines Flight 1353 where the first officer assumed the captain’s duties after unfortunately passing away in flight, and in numerous flight instruction flights where the student pilot took over the controls after their flight instructors had passed out.
A Solution to Single Pilot Incapacitation
Although single-pilot operations are great, risks are involved knowing that there is only one competent pilot aboard the plane. A solution to this problem is to always have another person who may or may not have a license on the flight deck along with the pilot, and is briefed pre-flight on how to communicate with ATC and some basic aircraft controls in the event that the competent pilot becomes unconscious.
The crash of N611VG is under investigation, and no theories can be proven to be correct at the moment. However, two of the theories are presented in this article in an attempt to suggest new solutions to the risks in aviation.