Report: Swiss E145 at Nuremberg on Jul 18th 2005, overran runway

23.07.2010 - 13:24

Map (Graphics: BFU)A Swiss International Airlines Embraer ERJ-145, registration HB-JAU (now XA-ULI) performing flight LX-1190 from Zurich (Switzerland) to Nuremberg (Germany) with 16 passengers and 3 crew, had encountered turbulence and icing conditions enroute. The airplane subsequently landed on Nuremberg s wet runway 28, however experienced too low a deceleration to stop before the runway end. The captain attempted to steer the airplane into the last taxiway exit F at high speed, which caused the airplane to turn by about 200 degrees and roll backwards. The airplane came to a stop with both main gear on soft and the nose gear still on paved surface. No injuries occured, the airplane received damage to the tyres. The passengers were able to disembark via the airplane s integral stairs. Germany s Büro für Flugunfalluntersuchung BFU released their final report in German concluding the probable cause was: hydroplaning of the aircraft due to wet runway. Contributing were: - insufficient information provided to the crew about the actual runway condition - instable approach due to gusty winds - an added 20 knots to the approach speed - late touch down due to being too high above the threshold The captain, total flying experience 5545 hours thereof about 2500 hours on the Embraer, was pilot flying. Enroute the airplane encountered turbulence and icing conditions which was detected by the automatic icing detection system and caused the stall protection system to automatically increase all target speed by 5 to 7 knots. This increase can not be terminated until back on the ground. The crew prepared for an approach to runway 28 (runway length 2700 meters/8850 feet) with flaps at 22 degrees and 16000kg (35250lbs) landing weight and computed an approach speed of 127 knots, which resulted in an effective approach speed (Vapp) at 148 knots including wind, gust and icing compensations. The airplane was not equipped with thrust reversers, required landing distance available therefore was computed at 2312 meters suitable for the runway. During the approach the crew received weather information via the last ATIS stating winds from 290 degrees at 28 knots gusting 40 knots. The tower controller told the investigators, that a thunderstorm with heavy rain had moved across the airfield about 10 minutes prior to landing, the runway was wet but no standing water was observed on the runway surface. Another aircraft landed just prior to Swiss Embraer and exited normally via taxiway D, the crew made no comment about the runway condition. The tower told the crew that winds came from 360 degrees at 14 knots, no further data about runway or weather conditions were transmitted. According to flight data recorder data the airplane flew an ILS approach to runway 28 with autopilot engaged until 350 feet AGL, the approach was stabilised at 500 feet AGL. Following the deactivation of the autopilot at 350 feet AGL the airplane was flown manually but deviated above and below the glidepath several times. Thrust reduction began at 110 feet AGL, idle thrust was reached at 15 feet AGL. The airplane crossed the runway threshold at 54 feet AGL at a speed of 150 KIAS and touched down 981 meters (3200 feet) past the runway threshold at a speed of 128 KIAS. The ground spoilers automatically deployed (indicating wheel spin up), brakes pressure increased to about 400-500 PSI over the next 22 seconds resulting in a deceleration of 0.14G, then the deceleration reduced to 0.07G with the brakes pressure fluctuating between 250 and 0 PSI. 35 seconds past touch down the left hand brakes pressure briefly rose to 3000 PSI, the right hand brakes pressure remained at 3000 PSI for 7 seconds, deceleration remained at 0.07G. 32 seconds after touchdown the airplane began to turn left at a ground speed of 52 knots turning from 280 degrees to 080 degrees, the ground spoilers retracted automatically. The BFU analysed, that the airplane began hydroplaning 22 seconds after touchdown, when the deceleration reduced from 0.14G (medium braking action) to 0.07G (poor braking action, comparable with an icy runway). A normal deceleration would be around 0.3G, therefore a wet runway contributed to reduce the deceleration to 0.14G during the first 22 seconds. Friction however was still sufficiently high to spin up the wheels which triggered the ground spoilers to deploy. The runway friction was measured about 30 minutes after the incident the results however had little bearing into the conditions at the actual landing. The measurement however revealed several locations in the last third of the runway, where the friction value was below other areas thus indicating possible slippery surface. Analysis of the traces on the runway following the overrun revealed, that the airplane encountered a rare form of hydroplaning, the so called "rubber reversion hydroplaning". All 4 main wheel tyres and the runway tracks showed molten rubber. This form of hydroplaning can occur even on damp runways. When the wheels lock, the resulting friction heat and the moisture on the runway produce a steam cushion carrying the airplane even below usual hydroplaning speeds. The BFU analysed, that the landing distance computations showed a required landing distance available of 2312 meters leaving just 388 meters reserve. The airplane however landed 981 meters past the runway threshold, so that the available landing distance reduced to 1719 meters about 600 meters short of the requirement and therefore insufficient to stop the airplane on the runway. The BFU annotated, that they perceive the automatic increase of the target speeds by 5-7 knots, which can only be reset on the ground, as disadvantageous with regards to the landing distance necessary. HB-JAU in its final position (Photo: BFU): Tyre marks (Photo: BFU): Molten rubber (Photo: BFU): Read the article at http://avherald.com/h?articleBeae64d Modify your subscription at http://avherald.com/h?login