In May 2021, a tragic accident resulted in the loss of seven lives when a Citation 501, N66BK, crashed into Percy Priest Lake near Nashville, Tennessee, shortly after takeoff.
The incident occurred just before 11 a.m. with an overcast sky at 1,300 feet above ground level (AGL), although visibility below the clouds was good and there was no precipitation. The pilot had fully fueled the aircraft for the two-hour journey from Smyrna Airport (KMQY) to Palm Beach International Airport (KPBI) in Florida. After taxiing to Runway 32, he received instructions to turn to a heading of 090 upon takeoff and maintain an altitude of 3,000 feet. His previously received IFR clearance indicated a climb to flight level 330 (FL 330) was expected approximately 10 minutes post-departure.
“Understood,” the pilot confirmed, “we’re heading to 090 at or above 3,000.” The tower provided corrections, which the pilot acknowledged. Following this, the tower controller instructed him to switch to Nashville departure frequency, and he replied, “Going to Nashville.”
ADS-B data showed the Citation was climbing at 2,000 feet per minute and initiating a right turn as it entered the overcast layer. Roughly two minutes after takeoff, the aircraft had reached an altitude of 2,900 feet with a heading of 090 and a ground speed of 200 knots, but the pilot had not yet communicated with Nashville departure.
Departure control prompted: “N66BK, are you on frequency?”
The pilot confirmed his presence.
“N66BK, indicate your altitude; you are radar contact three miles north of Smyrna, fly a heading of 130,” the controller instructed.
The phrase “say altitude” usually indicates the aircraft is not at the designated altitude, and by this point, the Citation had descended to 2,500 feet.
Silence ensued as the Citation continued its right turn, now at a heading of 160 degrees. After 15 seconds, the departure controller repeated, “N66BK, did you copy your heading 130?” The controller did not comment on altitude, while the Citation was actually below 2,000 feet at this moment.
“130, 66BK,” the pilot responded, but he was never heard from again.
After reaching 2,900 feet, the Citation started to descend, with its airspeed increasing to 290 knots. At 1,875 feet, it rolled into a 60-degree bank to the right, then climbed at a rate of 6,000 feet per minute, reaching 2,975 feet in 14 seconds before it entered a swift left turn and subsequently dove. Witnesses described the impact with the water as resembling a lawn dart.
The National Transportation Safety Board (NTSB) determined that the erratic flight path of the Citation indicated a clear case of spatial disorientation and attributed the loss of control to the somatogravic illusion, as it occurred during initial ascent.
This illusion stems from the body’s inability to differentiate between the sensations of acceleration and pitching up, or deceleration and pitching down, when deprived of visual cues. Immediately after takeoff, when the airplane is both climbing and accelerating, the typical sensation of ascent can feel exaggerated, especially in powerful aircraft that gain speed quickly. As a result, the pilot may mistakenly perceive that the aircraft’s nose is rising, leading to an inappropriate pitch-down response, often subconsciously. Consequently, the airplane may stop climbing, descend, and inadvertently fly into terrain.
Each instrument pilot, or those who take off VFR at night over challenging terrains, can potentially encounter this illusion. However, the critical question is why some pilots crash while most do not. Since reliance on instruments is crucial, we can reformulate the question: Can a pilot trained to fly using instruments still lack the self-discipline to disregard physical sensations, no matter how compelling they may feel?
The Citation pilot, aged 59, held a commercial pilot certificate with ratings for single and multiengine land, instrument, and helicopter, as well as a CE-500 type rating that had expired prior to the accident. His wife was known for founding a church promoting weight loss through faith, and this inspired the couple to acquire both an MU-2B and the Citation. Initially flying a Cessna 172 and a Baron, he advanced quickly through various aircraft types. At the time of the incident, he had logged 1,680 flight hours, with 83 of those in the Citation, and possessed a total of 40 hours of actual instrument flight experience, only 6 of which were in the Citation.
Sixteen months prior to the accident, he completed a FlightSafety type rating course but did not achieve the required performance level to attempt the check ride. Following the course, he hired an instructor for 11.4 hours of flying, who reported to the NTSB that he “saw no issues” with the pilot’s capability to operate the Citation in instrument meteorological conditions (IMC). The examiner who administered his type rating check ride described him as “very competent” and possessing “full confidence” in his flying skills.
After receiving the type rating, the pilot accumulated around 25 hours of flying time with another instructor, who emphasized that their training was more about enjoying flying together than formal instruction, aiming to help the pilot become more familiar with the Citation.
This instructor, with extensive experience in jets and Citations, offered a detailed evaluation. He found the pilot to be safe and effective with checklists; however, he noted that the pilot seemed “always behind the airplane” and struggled to visualize his situation in terms of time and space without consulting his iPad. He had difficulties with the Citation’s autopilot, which he found less user-friendly than that of his MU-2, and preferred to fly manually. Although the pilot had ambitions to fly to prominent cities such as New York, Los Angeles, and Atlanta, the instructor expressed concerns about his readiness to navigate complex air traffic control environments.
The Citation was operating over its maximum gross weight, and its center of gravity (CG) might have been positioned unusually far forward, yet these factors alone would not suffice to explain the loss of control. Rather, the pilot’s challenges with situational awareness and autopilot operation seemed more relevant: he appeared to be slightly out of his depth.
Nonetheless, the instructor was puzzled by the pilot’s sudden disorientation during departure, a maneuver familiar to him. He speculated that the pilot may have inadvertently flipped the avionics master switch instead of turning off the igniters, a mistake he had made before.
Should the pilot’s disorientation have originated from the somatogravic illusion, it likely escalated into a broader sensation of vertigo. The erratic flight path exhibited by the Citation suggested a complete breakdown of situational awareness, where the pilot struggled to interpret the attitude indicator and relied solely on physical sensations for guidance. The flight path resembled that of a VFR pilot who inadvertently strays into a thunderstorm, rather than that of an experienced jet pilot navigating mild IMC.
The primary takeaway from this incident is the sobering realization that such tragedies are possible. The weather conditions were manageable. The flight was straightforward. Although the pilot was not exceptionally skilled, he was deemed capable and safe, with considerable experience in large, fast aircraft. He held a type rating for the jet. Yet, the tragedy still unfolded.
This column first appeared in the April Issue 957 of the FLYING print edition.
Based on an article from flyingmag.com: https://www.flyingmag.com/somatogravic-all-was-well-for-a-pilot-and-then-it-suddenly-wasnt/
