Fate, at times, reveals itself when, in a fatal event, the chain of small causes that provoke it, even though they could have been avoided, were not. The provisional report of the Civil Aviation Accident and Incident Investigation Commission (Ciaiac), which has been presented this Monday, just one year after the tragedy, describes the errors that caused the MD-82 aircraft bound for Las Palmas de Gran Canaria to take the lives of 154 people at Barajas airport.
According to the report, "three security barriers were exceeded": the verification manual was not applied correctly, the co-pilot reported a normal state of aircraft devices essential for takeoff (the flaps and slats, which were retracted and caused the accident), which did not correspond to the investigation tests, and finally, the system in charge of warning the crew of the aforementioned error failed.
However, the report makes it clear that the investigation continues, and further inspections of the ground sensing system and the aircraft's engines, among others, are pending. Likewise, aspects of human factors "will be investigated and analyzed in depth" to be reflected in a final report, which will also have a long period of preparation.
"The investigation data indicate that the takeoff maneuver was carried out with the slats and flaps retracted, which would constitute an inappropriate configuration that did not guarantee safety", the report indicates. The Ciaiac considers that for this, "three security barriers were exceeded for the takeoff to be carried out with an inappropriate configuration".
The checklist to configure the aircraft and the TOWS (the failure warning system), which did not warn of the erroneous takeoff configuration, were the fatal causes that, according to the provisional investigation, caused the tragedy.
Human errors
Firstly, the investigation reflects that the operator "had standard procedures and checklists in force designed for pilots to prepare a safe operation and which included the selection and confirmation of the appropriate configuration for takeoff". According to the report, the pilots used these procedures but due to factors such as "the return to the aircraft's parking due to a breakdown, the pressure due to the delay on the scheduled time or deficiencies in the working methods used in the cabin, the procedures were not strictly followed".
Specifically, the step of selecting and checking the flaps/slats lights was omitted after starting the engines. In addition, in the recordings, the co-pilot is heard "performing the last check of reading the values of the position of the center of gravity and the flaps on the adjustment panel for takeoff located on the pedestal and how he repeats the angle of the flaps again".
"However, the physical evidence and the recorded recording of the flaps in the DFDR (digital flight parameter recorder) are in contradiction with what the co-pilot is heard saying in the CVR (flight cabin voice recorder)". "It is considered, therefore, that the verification of the 'final items' did not mean a real verification of the indications in the cabin", the report adds, which concludes that "with everything, the most likely thing is that the flaps and slats were not extended by the crew for takeoff".
According to the company's Operations Manual in force at the time of the accident, the crew had to verify the operation of the TOWS when carrying out the checklist prior to starting the engines before the first flight of the day, and not in the subsequent ones, "so it is very likely that the crew did not verify the operation of the TOWS during their stopover in Madrid".
Manual revision
After the accident, in October 2008, the operator revised the manual and established the check before each flight. However, the report specifies that after the accident suffered by an aircraft of the same model in Detroit, the company McDonnell Douglas issued a telex in 1987 addressed to all operators of this type of aircraft in which it recommended that the TOWS check be carried out on each flight. However, it also indicates that this notice may not have had an effect on the company Spanair, which "started its activity with this type of aircraft later".
As a result of this new accident, the same recommendation has been extended to various air navigation organizations around the world. A piece of advice that the report makes to the Federal Aviation Administration (FAA) of the United States.
Technical error
"The investigation data also indicate that the system in charge of warning the crew of the inadequate configuration for takeoff (TOWS) did not work". The report includes an extensive investigation into one of the possibilities that this was the case, although it is not conclusive.
The report indicates that the aircraft's stopover was delayed due to an "abnormal indication" in the cabin of the temperature of the RAT probe, which reached 104 degrees Celsius. The pilots proceeded, according to technical indications, to disconnect it. This high temperature, according to the report, indicates that the probe heater was active on the ground, although "it is designed to heat the probe only when the aircraft is in flight".
According to the investigation, "the high temperature indication while the aircraft was on the ground and the failure of the TOWS to sound the warning horn to the crew during the takeoff run could be related to a possible malfunction of the R2-5 relay", a device that, inserted in a circuit, produces certain modifications in it or in another connected to it.
Analyzing data
The data collected in the first tests of the operation of this device after the accident are still being analyzed and a complete disassembly of the device is still missing, which could provide data "of great importance to determine its status", which leads to stating that "there is no conclusive information to establish whether a failure of the relay prevented the TOWS from working during the takeoff run that preceded the accident".
Despite this, it is significant that a high percentage of cases studied by the commission (80 percent), the same device (R2-5) was the cause of the same anomalous heating failure in other aircraft.
ACN Press
