Sicily

The accident was caused by the failure of the nose landing gear (nose gear up) due to over-extension of the shock absorber which caused interference between the tires and the NLG compartment and locked the NLG in a retracted position. The over-extension was caused by the incorrect installation of some internal components of the shock absorber during the replacement of the internal seals the day before the accident.
The following factors contributed significantly to the improper activity conducted at maintenance:
- the insufficient experience of technical personnel in carrying out the maintenance tasks conducted on the NLG;
- the lack of controls on the operations carried out, deemed unnecessary by the CAMO engineering department;
- the lack of definition of roles and tasks during the planning phase of the maintenance work;
- the operational pressure on maintenance personnel, arising from the need to conclude maintenance operations quickly in order not to penalize the management of the aircraft;
- the insufficient clarity and lack of sensitive information in the maintenance tasks and related figures contained in the AMM, regarding the replacement of internal shock absorber seals, subsequently made clearer by the manufacturer;
- the reported black and white printing of the applied AMM procedures, which could have made the warnings in the manual barely legible.

The event is classified as short landing accident and the cause is mainly due to human factors. The fact that the aircraft contacted the ground took place about 367 meters short of the runway threshold was due to the crew's decision to continue the instrument approach without a declared shared acquisition of the necessary visual references for the completion of the non-precision procedure and of the landing maneuver. The investigation revealed no elements to consider that the incident occurred due to technical factors inherent in the aircraft.
The following contributing factors were identified:
- The poor attitude of those present in the cockpit to use of basics of CRM, particularly with regard to interpersonal and cognitive abilities of each and, overwhelmingly, the commander.
- Deliberate failure to comply with SOP in place which provided, reaching the MDA, to apply the missed approach procedure where adequate visual reference of the runway in use had not been in sight of both pilots.
- Failure to apply, by those present in the cockpit, the operators rules, concerning in particular: the concept of "sterile cockpit"; to do the descent briefing; to make callouts on final approach.
- The routine with the crew, carrying out approaches to Palermo-Punta Raisi Airport, from which the complacency to favor the personalization of the standards set by operator, and by law. The complacency is one of the most insidious aspects in the context of the human factor, as it creeps in individual self-satisfaction of a condition, which generates a lowering of situational awareness, however bringing them to believe they had found the best formula to operate.
- The existence of adverse weather conditions, characterized by the presence of an extreme rainfall, which significantly reduced the overall visibility.
- The "black hole approach" phenomenon, due to adverse weather conditions together with an approach carried out at night, the sea, to a coast characterized by few dimly lit urban settlements.
This created the illusion in the PF of "feeling high" compared to what he saw and believed to be the threshold, with the result to get him to abandon the ideal descent profile, hitherto maintained, to make a correction and the subsequent short landing.
- The decrease of performance of the light beam produced by SLTH in extreme rain conditions; The only bright horizontal reference for the crew consisted of the crossbar of the SALS, probably mistaken for the threshold lights.

The accident under examination, as most aviation accidents, has been determined by a series of events linked one another, which caused the final ditching. The ditching was primarily due to the both engines flame out because of fuel exhaustion. The incorrect replacement of the fuel quantity indicator (FQI) was one of the contributing factors which led irremediably to the accident. The accident’s cause is therefore traceable firstly to the incorrect procedure used for replacing the FQI, by means of the operator’s maintenance personnel. This shall be considered the disruptive element, which caused the final ditching of the aircraft due to the lack of fuel that caused the shutdown of both engines. As said before the accident was determined by a series of events (contributing factors) linked one another. Hereafter are listed some considered of major importance.
- Errors committed by ground mechanics when searching for and correctly identifying the fuel indicator.
- Errors committed by the flight crew: non-respect of various operational procedures.
- Inadequate checks by the competent office of the operator that flight crew were respecting operational procedures.
- Inaccuracy of the information entered in the aircraft management and spares information system and the absence of an effective control of the system itself.
- Inadequate training for aircraft management and spares information system use and absence of a responsible person appointed for managing the system itself.
- Maintenance and organization standards of the operator unsatisfactory for an adequate aircraft management.
- Lack of an adequate quality assurance system;
- Inadequate surveillance of the operator by the competent Tunisian authority.
- Installation characteristics of fuel quantity indicators (FQI) for ATR 42 and ATR 72 which made it possible to install an ATR 42 type FQI in an ATR 72, and vice versa.
The analysis of various factors that contributed to the event has been carried out according to the so called Reason’s "Organizational accident" model. Active failures, which had triggered the accident, are those committed both by ground mechanics/technicians the day before the event while searching for and replacing the fuel quantity indicator, and by the crew who did not verify and fully and accurately complete the aircraft’s documentation, through which it would have been possible to perceive an anomalous situation regarding the quantity of fuel onboard. Latent failures, however, remained concealed, latent in the operator’s organizational system until, some active errors (by mechanics and pilots) were made, overcoming the system’s defence barriers, causing the accident. Analysing latent and active failures (errors) traceable to various parties, involved in the event in several respects, it clearly emerges that they were operating in a potentially deceptive organizational system. When latent failures remain within a system without being identified and eliminated, the possibility of mutual interaction increases, making the system susceptible for active failures, or not allowing the system to prevent them, in case of errors. Active failures were inserted in a context characterised by organizational and maintenance deficiencies. The error that led to the accident was committed by mechanics who searched for and replaced the FQI, but this error occurred in an organizational setting in which, if everybody were operating correctly, probably the accident would not have occurred. Inaccuracy of information entered in the aircraft management and spares information system, particularly regarding the interchangeability of items and the absence of an effective control of the system itself, has been considered in fact one of the latent failures that contributed to the event. The maintenance and organization standards of the operator, at the time of event, were not considered satisfactory for an adequate management of the aircraft. The flight crew and maintenance mechanics/technicians involved in the event, when they made incorrect choices and took actions not complying with standard procedures, did not receive sufficiently effective aid from the system in order to avoid the error.

It is believed that the crew encountered windshear during the last portion of the flight.

It was determined that a fire erupted in the cargo compartment and that toxic fumes emanated from the paints, most of them consisting of cyanure. The crew was quickly asphyxiated by these toxic fumes.