Nostrum CRJX at Pamplona and Madrid on Feb 1st 2015, burst one tyre, one tyre with flat spot
Last Update: March 27, 2017 / 19:13:36 GMT/Zulu time
Spain's CIAIAC reported in their preliminary notice of Feb 23rd 2016, that the suspicion of a burst tyre by the crew was confirmed, when the outboard left hand main tyre was found burst, a flat spot was found on the right outboard main tyre. White ice was found accumulated along the gear struts and attached to the gear doors. The CIAIAC opened an investigation into the occurrence looking particularly into the weather conditions at Pamplona at that day, thawing operation at Pamplona and the operating parameters during taxi and takeoff. Data have been collected, the analysis is still ongoing.
On Mar 27th 2017 the CIAIAC released their final report concluding the probable causes of the incident were:
The incident was caused primarily because part of the slush encountered while taxiing and during the subsequent takeoff run is thought to have made its way into the landing gear bays, adhering to the components there. When the gear was retracted, wheels number 1 and 4 were in a lower position and thus more exposed to low temperatures during the flight. As a result, the slush deposited on the gear could have fallen due to gravity to the brake assemblies before freezing in place.
The following contributed to the incident:
- Improper snow clearing operations at the Pamplona Airport, which resulted in the presence of slush on the apron and cordons of slush both on the taxiway and on the runway.
- The improper operation taken by the crew when taking off from a contaminated runway, namely: heat the brakes; delay gear retraction to facilitate the detachment of the contaminant; make a positive landing at the destination to detach any remaining frozen contaminant.
The CIAIAC analysed that after landing wheels #1 and #4 did not rotate although no brakes had yet been applied. It was likely that the brakes assemblies and the wheels were effectively locked.
The CIAIAC wrote: "The aircraft was equipped with carbon, instead of steel, brakes. The main drawback of carbon brakes over steel brakes is that due to their porosity, they can absorb large amounts of moisture. If this happens, the moisture can soak the brakes, which can then freeze if the temperature conditions are right. This situation can lock the brakes, which could potentially result in a tire blowout during the landing. In light of the above information, it is likely that some of the slush encountered by the aircraft while taxiing and during the subsequent takeoff run made its way into the gear bay and attached to the gear structure due to its viscosity. When the gear was retracted, wheels number 1 and 4 remained in a lower position that is less protected against low temperatures while in flight. As a result, the slush could have fallen under the force of gravity to the brake assemblies, soaking them in parts and forming deposits that later froze."
With respect to crew actions the CIAIAC analysed:
In contrast to the instructions in the procedures described above, the crew did not comply with the procedural requirement of getting 3 BTMS units prior to takeoff. They stated that this would have forced them to do seven braking cycles (actually six by procedure for their weight) from 20 to 5 kt, unfeasible over the short taxi distance (about 300 m) used when taking off from the Pamplona Airport. They also argued that they could not delay retracting the gear as specified in the procedure because they did not want to “go into the clouds” with the gear out and because, as they stated, it would be “hazardous” at an airport with a geography like Pamplona’s. In this regard, the CIAIAC believes that if it is impossible to comply with a procedure, crews should report this and the operator should write a procedure specific to the airport in question.
When landing, the crew did not make a positive landing, as specified in the applicable procedures. When asked why they did not carry out this maneuver, both replied that they did not think the weather conditions at LEPP warranted such a landing, although when they felt vibrations during the landing roll, the first officer immediately associated them with that problem.
With respect to the aerodrome in Pamplona the CIAIAC analysed:
The information relayed about the coefficient of friction did not correspond to the values for each third of the runway51, but rather to the average of the first run, the second run and the average of both runs. The airport concluded that the procedure did not consider criteria involving how the coefficient of friction measurement should be applied depending on the contaminant type. The point where the contaminant depth was measured was chosen by the RFFS Crew Chief using the least favorable selection criteria. The contaminant depth was determined at the same time that the second evaluation of the friction coefficient, and the contaminant depth on the taxiway and apron, believed to have been greater than on the runway, was not measured. There were also snow trails along the taxi path taken by the aircraft, meaning that contaminant build-up could also have occurred during the taxi phase.
On the day of the incident another operator asked that the apron be cleared up to the airplane, and passengers complained that it was difficult to access the terminal. The information provided by the airport indicated that there were not enough personnel to remove snow. The day after the incident, at about the same time (05:10), the other operator also asked that a path be cleared so that passengers could board the airplane, and later informed that they would not take off until both the apron and runway were completely clear of snow. Further snow removal activities were recorded on that day.
According to the airport’s procedure, when the snow is 0 to 1.5 cm deep, the method used on the runway is to apply urea. The aircraft manufacturer’s limits in terms of the maximum contaminant depth allowed to cover a significant part of the runway is 1.5 cm for slush. According to the EASA’s Technical Instructions, if more than 1.27 cm of slush is present, operations have to be suspended. The RFFS reported a slush contaminant depth of 12 mm. In light of these figures, the aircraft’s operation would have been within limits, the snow did not have to be removed and the limit specified by the EASA for suspending operations was not exceeded.
Deficiencies were detected, however, in how the procedures in the Winter Operations Plan were applied, as well as in the training given to the personnel (RFFS) involved in both taking readings and clearing the movement area (maneuvering area plus apron).
After conducting its analysis, the airport proposed taking certain actions, but as of this writing, the CIAIAC is unaware of what measures, if any, have been adopted. Two safety recommendations are thus issued in this regard.
LEPP 010700Z 34012G22KT 290V010 7000 SN SCT011 BKN030 BKN040 01/01 Q1007=
LEPP 010630Z 31011KT 280V340 9000 -SN SCT015 BKN025 BKN035 01/01 Q1007=
LEPP 010600Z 33012KT 7000 SN BKN007 BKN025 01/01 Q1006=
LEPP 010549Z 32013KT 280V340 3000 SN BKN006 BKN020 01/01 Q1006=
LEPP 010537Z 32016KT 9000 SN SCT011 SCT015 BKN025 02/00 Q1006=
LEPP 010530Z 31013G23KT 280V340 9999 SN SCT020 BKN040 02/00 Q1006=
LEPP 010500Z 32012G23KT 290V350 9999 SCT025 BKN040 02/M00 Q1005=
LEPP 010430Z 30015G27KT 280V340 9999 SCT030 BKN045 02/00 Q1005=
LEPP 010400Z NIL=
LEPP 010330Z NIL=
LEPP 010300Z NIL=
LEPP 010230Z NIL=
This article is published under license from Avherald.com. © of text by Avherald.com.
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