E135, Norwich UK, 2003
E135, Norwich UK, 2003
On 30 January 2003, an Embraer 135 being operated by Swedish company City Airline on a scheduled night passenger flight from Aberdeen to Norwich overran the slush-covered landing runway following a late touchdown in normal visibility. There were no injuries to any of the 25 occupants and with no signs of fire, the passengers subsequently disembarked via the aircraft integral airstairs. There was only minor damage to the aircraft landing gear which required wheel replacement.
Description
On 30 January 2003, an Embraer 135 being operated by Swedish company City Airline on a scheduled night passenger flight from Aberdeen to Norwich overran the slush-covered landing runway following a late touchdown in normal visibility. There were no injuries to any of the 25 occupants and with no signs of fire, the passengers subsequently disembarked via the aircraft integral airstairs. There was only minor damage to the aircraft landing gear which required wheel replacement.
Investigation
An Investigation was carried out by the UK AAIB. It was established that the First Officer as PF and that at the time the flight crew briefed for their approach they based it on the Automatic Terminal Information Service (ATIS) current at the time, which had given a wind velocity of 360° /11 knots, a temperature of PS01 and the runway state as wet. They were only made aware of the possible surface contamination when on base leg for the ILS when ATC APP advised that the runway was now covered in “slush mixed with hail to a depth of 2-3mm.... you can still see the white lines through the slush.” Although the flight crew had acknowledged this, they had no recollection after the event of receiving this information.
During the descent the flight crew had also received an Engine Indicating and Crew Alerting System (EICAS) Stall Protection System (SPS) warning due to the sensing of airframe ice accretion and in accordance with SOPs had added 6 knots to the calculated approach speed making it 130 knots with 120 knots as the Reference Speed (Vref). Then, during the final stages of the ILS approach to Runway 27, the TWR controller gave spot winds as the wind veered and increased. At touchdown the wind velocity was 020° / 23 knots which was equivalent to a tailwind component of 10 knots and a crosswind component of 21 knots.
The aircraft floated down the runway, touching down at a speed of 120 knots between 500 and 600 metres from the threshold. Brake applications were ineffective and the First Officer transmitted that they were 'going off the end of the runway' just before the aircraft left the paved surface at a ground speed of 74 knots. The overrun area was a field covered in snow over a soft surface which produced significant retardation and the aircraft stopped with the wheels up to the axles in mud 130 metres from the end of the runway.
The Investigation noted that the flight crew had briefed for the Flap 22 approach on the basis that the ATIS conditions they heard meant that a landing distance of 1,730 metres. was required compared to the LDA of 1841 metres. However, by the time the aircraft landed, with a 10 knot tailwind component and with a 6 knot increase in approach speed because of the SPS warning, it was calculated during the Investigation that the required landing distance was actually 2,150 metres. However, under prevailing definitions, the runway surface was not considered to have been ‘contaminated’ for aircraft landing performance purposes. It was also noted that the applicable State Regulations for airport operators extant at the time included the remark stated that “where contaminant remains, runway condition reports shall not contain readings taken directly from friction measuring machines”. In relation to reduced crosswind limits on runways assessed as having less than dry runway braking action, it was noted that although “many airlines' performance tables provide a direct correlation between type of contaminant and braking action in order to calculate a crosswind limit, this was not the case with this company” and that, had the crew wished to check their landing crosswind limitation, they would have needed a braking action report from ATC, which would not have been forthcoming.
The Investigation concluded that the flight crew
“appeared unaware of how critical the LDA at Norwich Airport was for their approach in the prevailing conditions. Their arrival brief was based on ATIS information that was benign compared to the conditions actually encountered. Had the crew consulted any of the tables in the (Route Planning Manual) at this point however, they would have realised that minor changes in the landing conditions or a less than accurate approach and touchdown would have resulted in a critical situation. A more thorough brief may have enabled them to identify exactly what weather changes would require a diversion, eliminating the need to consult RPM tables during the high workload period of the approach.”
Two Safety Recommendations were made:
- That the CAA encourage research that could lead to the production of equipment that can accurately measure the braking action of runways under all conditions of surface contamination. (2003-96)
- That City Airline review its Embraer 135 landing configuration policy and, in consultation with Embraer Brasileira de Aeronautica SA, produce a comprehensive written procedure that includes advice and highlights the ramifications associated with the execution of a 'Flap 22' landing. (2003-97)
The Final Report of the Investigation was published on 6 November 2003 and may be seen in full at SKYbrary bookshelf: AAIB Bulletin No: 11/2003 Ref: EW/C2003/01/05