On 2 March 2018, a Cessna 525 (EC-KES) being operated by Taespejo on a non-scheduled international passenger flight from Lille to Bern as TES202 touched down aligned with the left hand side of the landing runway in reportedly normal visibility at night and the Captain took over and returned the aircraft to the runway it had briefly left altogether. Completion of the landing roll and taxi in then followed without further event but damage to the aircraft was found after passenger disembarkation and a runway inspection found broken edge lights and landing gear wheel tracks in the snow adjacent to the left hand edge of the runway.
An Investigation was carried out by the Swiss Transportation Safety Investigation Board (STSB). No flight data or voice recorders were installed in the aircraft and there was no regulatory requirement for them to be fitted, so the Investigation was based on the crew statements, ATC radar recordings and site inspection. It was noted that the Captain was a Portuguese national who had a total of 6,878 flying hours of which 3,540 hours were on type and that the First Officer, who had been PF for the landing, was a Spanish national with a total of 1,001 flying hours of which 274 hours were on type.
Earlier in the day, the aircraft operated by the same flight crew had taken three passengers from Geneva to Lille with the expectation being that in the evening, a return flight to Geneva with the same three passengers on board would be made. However, when it became apparent that there had been sufficient snowfall at Geneva to cause a consequent temporary closure of the runway there, the return flight was instead re-planned to Bern, where the forecast was more favourable. Both pilots stated that they had been familiar with that airport.
The fight was uneventful with the Bern TAF for the ETA indicating light winds, a ceiling of 4,500 feet, surface visibility 5000 metres and no precipitation. The ATIS current 25 minutes prior to landing gave similar conditions with no cloud below 11,000 feet aal but with shallow fog present. Snow was present either side of the landing runway 14 but the runway surface was reported as being completely clear of snow with braking action “good” over the full length of the runway. The TWR controller subsequently clarified that the reported shallow fog was only present over the first 230 metres of the 1530 metre LDA for landing runway 14, which was 30 metres wide and had runway edge lights but no centreline lighting. TWR also advised that the runway lighting had been switched to maximum brightness.
An ILS approach was flown and after reporting established on the ILS LLZ, they were cleared to land and when acknowledging this whilst at 5000 feet QNH (approximately 3,300 feet aal), the crew added that “they already had full view of runway 14”. Recorded radar data showed that between 7 nm and 3½ nm from touchdown, the aircraft groundspeed had been approximately 205 knots which, with the maximum wind speed below 2300 feet aal having been at the most 3 knots, would have been close to the corresponding airspeed. Thereafter, speed was reduced to reach 160 knots passing 1000 feet aal and further reduced over the next 0.4 nm to just under 140 knots, the final recorded ground speed data point.
The crew stated that the AP had been disconnected “shortly before reaching the DA” and that “the entire approach was stabilized, had proceeded without any problems and the view of the runway was not restricted”. Their statements also said that “the aircraft touched down at a normal rate of descent, perhaps slightly to the left of the middle of the runway (and) that subsequently, the aircraft suddenly yawed slightly to the left around its vertical axis as if the runway was slippery and ended up on the left-hand side of the runway, perhaps in the snow to the left of the runway” after which the Captain had taken over control and steered the aircraft to the right to the middle of the runway.
Inspection of the aircraft on stand after disembarkation of the passengers found that the doors of both main landing gears and the left flap were damaged and that all wheels and the underside of the fuselage and wings were “covered in mud” which was also present on both the inlet and exhaust of the left engine. A subsequent inspection of the runway found that six runway edge and taxiway lights had been damaged, some having been “completely torn off” their mountings.
Immediately after the landing, a further measurement of the friction coefficient along the full length of the runway was carried out and confirmed that the corresponding braking action was still “good”. The runway inspection which had found the damaged lights also found wheel tracks in the snow adjacent to the left hand edge of the runway. When measured, these were found to match the separation of the landing gear on a Cessna 525. The first evidence of wheel contact with the snow, described as no more than “a slight imprint in the snow”, was assessed as attributable to the left main landing gear in the final stages of the flare prior to touchdown. It began with approximately ½ metre beyond the edge of the runway approximately 530 metres beyond the landing threshold [position 1 in the illustration below]. This track increased its deviation from the runway edge to 2 metres before temporarily ceasing after approximately 40 metres and then restarting in the vicinity of taxiway ‘B’, this time with the wheel firmly on the ground and making an imprint on the frozen ground underneath the snow. This track was then joined by those of the nose gear [position 2] and finally the right main gear [position 3] before all tracks made a sharp turn to the right and onto the runway approximately 850 metres beyond the landing threshold [position 4].
An annotated section of the runway showing the extent of the off runway landing roll (the area within the yellow dotted rectangle is enlarged in the next illustration). [Reproduced from the Official Report]
Wheel track detail - left main wheel (red), nosewheel (green) and right main wheel (red). [Reproduced from the Official Report]
It was noted that the crew account of the landing position did not match the available evidence. It was also noted that whilst the operator’s OM specified that an approach made under “visual flight rules conditions” should, once fully established on the glideslope, be made at “less than 170 KIAS”, the available data indicated that on becoming fully established, the airspeed was still in excess of 200 knots. The OM also specified that the speed should be VREF +10 (which was 115 KIAS for the approach concerned) once within 4 nm of the runway threshold whereas at this point it was still over 200 knots. Even passing 1,000 feet agl, the speed was still only reducing through 158 knots. The actual touchdown position was also estimated to have been in excess of 600 metres past the runway landing threshold and almost 400 metres beyond the paint-marked aiming point.
Since the crew stated that they had not realised that the aircraft had landed aligned with the edge of the runway or had then rolled for 300 metres partly or wholly off it before corrective action had been initiated, it was considered that two circumstances may have prevailed:
- The crew mistook the left-hand runway edge lights as runway centreline lights whereas no such lights are installed.
- The shallow fog at the beginning of the runway degraded visual reference to the extent that the PF failed to notice the lateral deviation to the left.
The Investigation was unable to determine why the touchdown had been made aligned with the runway edge but formally confirmed that:
- The crew executed the instrument approach at a considerably excessive speed and only reduced the speed very late. At a distance of 2 nm before the runway threshold and at a flying altitude of 1,000 ft above ground, the ISA was still 43 knots above the recommended final approach speed. In doing so, the crew clearly deviated from the stabilised final approach principle.
- Following a normal flare, the aircraft touched down in the snow to the left of the runway and rolled for approx. 300 metres along the left-hand edge of the runway, before making an abrupt turn to the right, back onto the runway.
- There was shallow fog in the landing zone.
- The surface of the runway was damp. The friction coefficient (FC) along the entire runway was such that good braking action could be achieved.
The Final Report of the Investigation was completed on 24 May 2018 and subsequently published on 18 September 2018. No Safety Recommendations were made.