History of the Flight
On 23 January 2020, the crew of Bombardier CL600 2C10 (CRJ700) registered F-GRZL, operated by HOP!, was conducting a commercial passenger flight from Lille to Lyon-Saint-Exupéry. Aware of low visibility procedures (LVP) at the airport due to freezing fog and visibility below 300 m, the crew had planned a CAT IIIa precision approach. The captain, as pilot flying (PF), was required to use the Head-Up Display (HUD) for such approaches.
During the approach, the aircraft was stabilized on ILS 35R. At a height of 1,400 ft, the PF disconnected the autopilot and manually followed the HUD guidance cue. The aircraft remained stabilized. At around 500 ft, the aircraft entered cloud, and the PF reported that the lateral guidance cue began to diverge to the left. Concurrently, the pilot monitoring (PM) stopped monitoring the PFD to adjust his headset jack socket due to radio reception issues.
At 19:12:10, at 320 ft, the PF made four successive left roll inputs of increasing amplitude, reaching a left roll angle of 11°. The PF also applied a nose-up input at 19:12:14, lasting 33 seconds. The aircraft reached a minimum height of 265 ft at 19:12:17, left of the centreline and above the glide path. Two seconds later, the PF rolled wings level, but the aircraft was now on a flight path diverging 20° from the runway centreline.
The PM later stated that upon returning his eyes to the PFD, he saw the vertical bar offset right and called it out; the PF replied he was correcting. The lateral deviation increased, and the PM suggested a go-around. Between 19:12:22 and 19:12:30, the aircraft continued deviating left and above the glide path. The nose-up input increased, pitch reached 11°, then decreased. Power levers were advanced incrementally. Airspeed dropped to 120 kt (15 kt below reference) before recovering. At 19:12:37, 23 seconds after the nose-up input began, power levers were moved to 50° (TOGA detent) and the PF pressed the TOGA button, activating go-around modes. Pitch stabilized at 8°.
At 19:12:41, the controller asked if they were going around; the crew confirmed. The aircraft flew over the threshold of parallel runway 35L at 420 ft with a magnetic heading of 341°. The controller instructed the crew to continue on heading and climb to 5,000 ft. F-GRZL then flew over a taxiway, an aircraft parking area, and near the control tower at 820 ft. The controller asked if the crew had lost the centreline; they replied there was a small instrument problem but everything was regained. A second CAT IIIa approach was completed without incident.
Meteorological Information
At the time, Lyon-Saint-Exupéry was under LVP conditions with night operations. Visibility ranged from 140 m to 300 m with freezing fog. Temperature was -1°C, dew point -1°C, QNH 1026 hPa. Wind was east to south-east at 2-5 kt. Runway visual ranges (RVR) at 19:09:24 were 325 m for threshold 35R, 300 m mid-runway, and 400 m opposite.
Aerodrome Information
The missed approach path for runway 35R published in the AIP instructs straight-ahead climb to 5,000 ft with radar vectoring. The ILS 35R has a self-monitoring function that activates every ten minutes; no alerts were recorded before or after the incident. Examination of continuous localizer signal recordings at the threshold found no ground-based interference. The recorded localizer deviation parameter in the QAR matched the aircraft’s actual flight path, confirming the localizer signal validity.
Head-up Guidance System (HGS) Information
F-GRZL is equipped with a Collins Aerospace HGS 4200, installed under STC on the left side only. It is certified for CAT III manual approaches; the captain must be PF. The HGS uses the same sensor data as the FCS to compute guidance commands. It offers various modes, including AIII for CAT III approaches. The AIII mode arms when conditions such as runway altitude entry, glideslope entry, IRS in NAV, selectors in NORM, no HGS fault, same VHF NAV frequencies, AGL above 800 ft, and FCS armed LOC and GS are met. When active, AIII is displayed in green on the PFD and on the HUD. The PF places the flight path symbol on the guidance cue to follow the path. Below 300 ft, runway edge lines appear on the HUD. If lateral deviation is excessive, a triangle indicator appears. An approach warning (APCH WARN) may trigger below 500 ft for out-of-tolerance conditions.