CL60, London Stansted UK, 2022

CL60, London Stansted UK, 2022


On 31 January 2022, a Bombardier Challenger 604 pilot lost control during the final stages of a London Stansted night crosswind landing. A bounced nose-gear-first touchdown was followed by a brief runway excursion onto grass before a return to the runway and a climb away. A diversion to London Gatwick followed without further event but subsequent inspection revealed structural and other damage sufficient to result in the aircraft being declared an economic hull loss. The Stansted touchdown was found to have occurred after a premature flare at idle thrust continued towards the stall and a momentary stick pusher activation occurred.

Event Details
Event Type
Flight Conditions
Flight Details
Type of Flight
Intended Destination
Actual Destination
Take-off Commenced
Flight Airborne
Flight Completed
Phase of Flight
Missed Approach
Location - Airport
Approach not stabilised, Copilot less than 500 hours on Type, Destination Diversion, Landing Flare Difficulty, CVR overwritten
Fatigue, Inappropriate crew response - skills deficiency, Manual Handling, Plan Continuation Bias, Procedural non compliance, Ineffective Monitoring - PIC as PF
Aircraft Flight Path Control Error, Environmental Factors, Hard landing
Off side of Runway, Continued Landing Roll
Damage or injury
Aircraft damage
Hull loss
Non-aircraft damage
Non-occupant Casualties
Off Airport Landing
Causal Factor Group(s)
Aircraft Operation
Safety Recommendation(s)
None Made
Investigation Type


On 31 January 2022, control of a privately owned and operated Bombardier Challenger 604 (N999PX) which was attempting to land at London Stansted in night VMC after a flight from Cairo with two passengers on board was lost after stick shaker and stick pusher activation occurred in the flare just prior to touchdown. After wing contact with the runway, several bounces and a veer off the left side of the runway, the runway was regained and a go around flown. The crew then decided to divert to London Gatwick and did so without further event. Damage to the aircraft during the attempted first landing was subsequently found to be so significant that it was beyond economic repair and it was declared a hull loss on that account. There were no injuries to any of the occupants during the initial landing attempt at London Stansted.


Ground contact damage to the left wing. [Reproduced from the Official Report]


A Field Investigation into the Accident was carried by the UK Air Accident Investigation Branch (AAIB). Relevant recorded data was recovered from the FDR but the 30 minute CVR had been overwritten as a result of the aircraft continuing in service and the failure to isolate it promptly on completion of the accident flight. Recorded airport CCTV data covering the approach and go-around was also available.

It was noted that the 48 year-old Captain, who been employed by the owner since 2019 and was PF, had a total of 4,235 hours flying experience which included 1,320 hours on type. The owner’s three pilots were provided with “six-monthly recurrent training sessions in a simulator” with the most recent being for the accident pilot being his LPC two weeks prior to the accident. However, he also stated that he routinely observed a “personal crosswind limit of 20 knots” because he was “cautious about operating the Challenger 604 in strong crosswinds”. In this context, it was noted that the maximum demonstrated crosswind in the AFM was 24 knots and this was “not considered limiting for take-off and landing” unless reverse thrust was used which had been used for the accident landing despite the 3,049 metre LDA.

Similar experience and age information for the Co-pilot was not recorded although it was noted that he had completed his type rating three months earlier after previous pilot employment at CAT operators and had since accumulated “about 150 hours on type”. He was “qualified to fly the Challenger in command or as co-pilot”. He stated that he was unaware of the Captain’s “personal crosswind limit” and “did not recognise the idea of a personal limit” and believed that “the aircraft limits should be observed”. He also commented on the fact that although he was familiar with CRM training as provided at his previous CAT operators, this had not been so in his current job.

What Happened 

The flight initially departed for London Stansted from El Gouna and made a stop at Cairo International before continuing to London Stansted. The pilots had been notified of the flight two days earlier but were not told the departure time until the day before when they were instructed to report an hour before an intended departure time of 1000 UTC. Twenty five minutes before this report time, the departure was delayed by 90 minutes and the flight then departed at 1130 UTC and arrived at Cairo an hour later. 

The planned departure time for the 5¼ flight from Cairo to London was 1400 UTC but was delayed for almost 5 hours. The flight was uneventful and during preparation for the Stansted Approach, the ATIS was noted to be giving a surface wind of 290° at 13 knots with runway 22 in use. VREF was calculated as 119 KIAS and VAPP as 125 KIAS (the latter in accordance with a somewhat non-standard procedure applicable to the aircraft type). The flight was provided with radar vectors to the runway 22 ILS by Approach Control and once fully established, the aircraft was configured for landing with flaps set to 45°. On being cleared to land by Tower with about 90 seconds to go, a spot wind of 300 at 13-25 knots was given.

FDR data showed that the Captain disconnected the AP at approximately 150 feet agl at 136 KIAS and with both engines at approximately 50% N1. Prior to this, the AP had maintained the flightpath without any large control surface deflections, the AoA vanes were the same and remained below +5°. Once the AP had been disconnected, an increasing amount of left rudder was accompanied by increasing oscillation as the ailerons were used to lower the right (into wind) wing. Thrust was increased to around 60% N1 and divergence in the left and right AOA vane deflection confirmed that a sideslip was being flown.

From 50 feet agl and at VREF +11, thrust was gradually reduced to idle over eight seconds and the aircraft - still in a sideslip - was then progressively flared for landing but floated for a further six seconds as the AOA recorded by both vanes increased with the left vane peaking at 18° at which point the aircraft “suddenly rolled left and pitched sharply down". The recorded pitch attitude changed from +8° to -2° and the recorded roll attitude changed from 10° right wing-down to 13° left wing-down in less than two seconds. Almost immediately, a momentary bounced ground contact occurred led by the nose and left main landing gear and followed by the right main landing gear. 

The aircraft was then briefly airborne again and reached its minimum airspeed of 101 KIAS as thrust was increased but because a nose up pitch attitude was still being held at 14°, the aircraft rolled to the left again, this time to 30° of bank whilst pitching down. Seven seconds later, the left main and nose landing gear made a further momentary ground contact despite additional nose-up elevator input and recorded normal acceleration reached almost 2.5g, the maximum allowable value. During this time, the aircraft briefly veered off the 46 metre-wide runway and its paved shoulder onto the adjacent grass and the Co-pilot stated that after the first bounce he had called “go around” two or three times. 

The go around then commenced and after 9 seconds, a warning of disparity in the position of the landing gear was annunciated. The flightpath was stabilised during the climb out and shortly after passing 500 feet agl, pitch reached a maximum of 21.6° nose up. On establishing contact with ATC radar, the co-pilot asked if the controller could find an airport nearby with “normal wind conditions”, stating when asked that their crosswind limit was 15 knots and was advised that London Gatwick had an almost into wind runway with a maximum reported wind speed of 18 knots and it was decided to divert there. The transit was without further event and followed by radar vectors to the runway 26 ILS followed by a normal landing. A “grinding noise” from the nose landing gear became apparent as the aircraft decelerated and it was decided to stop on the RET. Airport marshallers were asked to attend and make an external inspection and after doing so reported that obvious damage to the nose landing gear was visible. The aircraft was shut down and on disembarking the aircraft to inspect the damage, the crew then discovered damage to the aircraft left wing.    

The Captain subsequently reported that he believed that the stick pusher had activated at some stage during the near ground phase but unlike later similar aircraft, the installed FDR did not record activation of either the stick shaker or stick pusher. However, calculations by Bombardier for the Investigation found that the left AOA value had exceeded the stick shaker threshold for approximately two seconds just prior to the first touchdown and then just prior to the second touchdown, both AOA values had exceeded the stick shaker and stick pusher thresholds with “at most, one second between the second stick shaker activation and the stick pusher activation”.

An AAIB examination of the accident site later that day found that between the runway 22 intersections with taxiways ‘PR’ and ‘U’ (approximately 1,070 metres and 1,470 metres and beyond the runway TDZ, there were three separate wing strike marks on the paved surface. Each of these measured approximately 20 metres and had been marked by paint transfer from the aircraft left wing. All three landing gear wheel tracks then transitioned to furrows in the adjacent grass and debris from the wing was found where it had struck a concrete pad in the grass area.  

A preliminary external damage assessment confirmed considerable ground contact damage to the left wing and winglet and its substructure, to the left aileron and to the left outboard flap fairing. Light scuffing, possibly indicative of relative movement between the wing and fuselage, was evident on the skin at the left wing root. The left wheel axle of the nose landing gear had failed so that the top of the left wheel was angled towards the landing gear leg (see the illustration below) and its tyre inboard sidewall had been severely scored and abraded by rotation of the tyre against a grease nipple at the bottom of the oleo. Some localised buckling of the lower fuselage skin immediately aft of the nosegear bay was also visible.

A more detailed damage assessment was performed after removal to a hangar by the contracted MRO in accordance with directions provided by Bombardier and it was found that as well as the externally visible damage, there was some bulging and buckling of the skin on the right sidewall of the nose landing gear wheel bay and operational test of the aileron control system found “several anomalies with the hydraulic actuation aspects of the system” and it was noted that the ailerons only returned to neutral if moderate force was applied. Finally, a wing symmetry and alignment check found that the extent of twist to the left wing meant that it was outside of allowable limits which Bombardier considered “indicated permanent plastic deformation of the wing attachment point” so that the ultimate strength of the materials involved had been exceeded and that a return to service would have required a complete wing set replacement.  


The nose landing gear showing the broken left wheel axle. [Reproduced from the Official Report]

Why It Happened

As the aircraft neared Stansted, the surface wind was, as reported and forecast, slowly veering and increasing but a detailed examination of the wind velocity recorded every second during the final stages of the approach and landing at Stansted found that it had still been within the applicable aircraft type crosswind limit of 24 knots throughout. Since the Co-pilot had been unaware of the Captain’s “personal crosswind limit” he had not prompted the commander to observe it.

The AFM was found to indicate that the correct VREF would have been 123 KIAS rather than the 119 KIAS used and the VAPP calculated according to the procedure in the OM should have been 142 KIAS rather than the 125 KIAS used with the OM procedure being “to maintain it until the aircraft crosses the threshold”. FDR data showed that the deceleration below even the crew’s (too low) calculated approach speed had been premature and by the time the AP was disconnected at approximately 150 feet agl, the recorded IAS was continuing to reduce below even the incorrectly calculated (too low) VAPP. This deceleration continued with no compensating thrust increase as the speed decayed below even the (too low) crew-calculated VREF for about five seconds before flight idle was selected. This absence of any recorded increase in engine thrust to maintain speed resulted in “reduced energy as the aircraft entered the flare and subsequent float” which was considered to indicate that neither pilot was closely monitoring the airspeed. The outcome was that as the aircraft floated 10 feet above the runway for six seconds, its forward speed reduced to just two knots above the stall speed “probably because the Captain had wanted to make a smooth landing for the comfort of the passengers”. It was noted that “had the aircraft touched down soon after the flare was initiated it is less likely the stick pusher would have activated and more likely that a runway excursion would have been avoided”

The only OM guidance on the conduct of crosswind landings was found in the Supplementary Procedures section on “Operation on Contaminated Runways where it was stated that “in crosswind conditions, the crosswind crab should be maintained for as long as possible, until prior to touchdown…”. No cross wind landing guidance was included in the OM ‘Normal Procedures’ section on Approach and Landing or in the type Recommended Operational Procedures and Techniques (ROPT). 

Overall, available evidence indicated that mishandling of the landing was ultimately attributable to inappropriate aircraft control in the landing flare. The operational context for this was a PF who seemed to be generally uncomfortable with crosswind landings. The owner’s operation of the aircraft was facilitated by employing three pilots all qualified to command on type but none of whom were qualified as Training Captains and all of whom flew relatively infrequently. 

The absence of any flight time limitations system meant that report times could, as in this case, be delayed at short notice and that delays developing within the course of a flight duty period could lead to an extended period in flight. In respect of the latter, the pilots involved had been obliged to complete a flight duty period (FDP) in excess of 14 hours although the Captain stated that in his view although impairment due to fatigue was not a cause of the accident, the length of the working day and the time of arrival, in combination with commercial pressure, was likely to have induced plan continuation bias

In summary, the Conclusion of the Investigation was that failure to discontinue the unstable approach before reaching the runway had been the collective result of fatigue, commercial pressure and the nature of the interactions between the two pilots which may have made them more susceptible to the plan continuation bias which appeared to have been present during the accident approach.

Intended Safety Action advised by Bombardier was an update of CL-604 manuals to include a similar level of information on crosswind landing technique to that which is already provided in the equivalent manuals for other aircraft which it manufactures.

The Investigation noted that two other very similar events involving loss of control and stick pusher activation of the same aircraft type just prior touchdown had occurred within five weeks of this one - on 27 January 2022 at Heraklion to a Guernsey-registered aircraft and on 28 December 2021 at Bern to a UK-registered aircraft. Both these events remained under investigation at the time this Investigation was completed.

The Final Report of the Investigation was published on 9 November 2023. No Safety Recommendations were made.

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