History of the Flight
The pilot, operating the aircraft privately with three passengers, took off from Runway 08 at Bournemouth Airport at 1417 hours. The autopilot was engaged shortly after departure. Climbing to 3,000 ft on a heading of 075°, the aircraft received an ATC instruction at 1418:35 to climb to FL100 and then resume own navigation direct Goodwood. The pilot acknowledged the climb clearance but did not respond to subsequent transmissions.
At 1418:39, while at 3,000 ft and 258 KIAS approximately 6 nm east of the airport, the pilot felt a light vibration. A button on the instrument panel labeled 'atlas' illuminated, displaying 'atlas inop limit 140 kias' in red. The aircraft then rolled left at a rate described as "very quick." As the roll reached 45°, the autopilot disengaged automatically.
The pilot applied full right aileron and full right rudder but found these insufficient. He moved the throttles to idle and used both hands on the control column. Recorded data showed a bank angle alert at around 60° roll, with a sharp increase in normal acceleration reaching +2.65 g. The roll peaked at 75° left wing down with 9° nose down pitch, 19 seconds after onset. Descent rate peaked at 4,500 ft/min at 235 KIAS, reaching a minimum altitude of 2,300 ft.
The pilot pressed the illuminated ATLAS button and reset the ATLAS main circuit breaker, but neither action had effect. At 1419:18, he reported 'a problem' to ATC, sounding breathless and strained. ATC advised a left-hand downwind for Runway 08 and initiated a full emergency procedure.
The pilot managed to lift the nose, reduce airspeed, and recover the bank to around 30° left wing down. He climbed to 3,200 ft with airspeed reducing to 144 KIAS, but the aircraft then entered a descending left turn. During the downwind leg, altitude descended from 900 ft to 300 ft. Turning onto base leg above a sports field, the pilot used continuous full right aileron and some right rudder until landing. As airspeed reduced, less right rudder was needed, and lateral control was achieved by modulating right foot pressure. The aircraft turned onto a 1 nm final approach, right of the runway centreline at 200 ft. The tower controller described the turn as so tight the aircraft appeared "on its side." At a landing speed of 105 KIAS, the pilot applied full flap and landed at 1423 hours.
Meteorological Information
The aerodrome weather at 1420 hours reported wind from 140° at 12 kt, visibility greater than 10 km, broken clouds at 4,000 ft amsl, temperature 9°C, and QNH 1025 hPa.
Personnel
The 73-year-old pilot held an FAA Airline Transport Pilot's Licence and a valid Class 1 medical certificate, with 4,400 total flying hours (3,200 on type). He operated N680KH privately. He had completed initial Citation type conversion and recurrent training at a simulator facility owned by the aircraft manufacturer's parent company. His most recent three-day recurrent check in May 2018 achieved top grading in all items and a written exam score of 100%. Since 1998, the pilot had purchased four Cessna Citations, three new and one used.
Previous Event
On 16 March 2019, while flying from Buffalo to Goose Bay, the aircraft experienced an uncommanded left roll with the ATLAS INOP button illuminating for three to five seconds before extinguishing. The maximum bank angle was around 50°, and the event lasted about twenty seconds. The pilot did not investigate because the system functioned normally for the remainder of that flight and four subsequent flights.
Recorded Data
The aircraft was not fitted with a Flight Data Recorder but had a Cockpit Voice Recorder (CVR) covering the entire incident flight. The Maintenance Diagnostic System (MDS) recorded two faults on 13 April 2019 at the time of autopilot disengagement due to excessive pitch or roll. A similar fault from one Flight Guidance Computer was recorded on 16 March 2019. The Terrain Awareness and Warning System (TAWS) activated three times during the incident flight but not during the previous event.