On 2 August 2012, a Cessna 500 (EC-IBA) being operated by AIRNOR (Aeronaves del Noroeste) for the National Transplant Organisation (ONT) based in Santiago had completed transport of a medical team from Asturias to Porto and back and was positioning with just the flight crew on board from Asturias to Santiago. After being cleared for an ILS approach to runway 17 at Santiago in night Instrument Meteorological Conditions (IMC) and subsequently cleared to land, the aircraft did not land and there was no explanatory communication with ATC. The wreckage of the aircraft was subsequently found on the extended centreline of the runway approximately 1nm from the threshold (see the diagram below). The two pilots had died on impact.
An aerial view of the northern end of Santiago Runway 17 showing the position of the Santiago VOR and the site of the crash (reproduced from the Official Report)
An Investigation was carried out by the Spanish Comisión de Investigación de Accidentes e Incidentes de Aviación Civil (Comisión de Investigación de Accidentes e Incidentes de Aviación Civil (CIAIAC)). The accident aircraft was not fitted with a FDR or CVR or a GPWS and was not required to be. Information on the approach made was obtained mainly from a radar recording made available to the Investigation.
It was found that the 35 year old Captain, who had been PF for the accident flight, held a CPL/IR with valid ratings for the C500/551 and SA226/227 as pilot in command and for the A320 as second in command only. Information from the operator indicated that his total flying time was "over 3600 hours" which included "over 554" on type. He had worked for the operator previously but had then left, rejoining in 2010 and since then had flown 29 hours on type in just over 2 years, having been certified as a Captain 13 days prior to the accident. An examination of the operators paperwork found that there was no evidence that the required training flights had taken place under the supervision of "personnel duly authorised by the authority" and in the case of the Proficiency and Line Checks which were required to qualify as a Captain under EU-OPS, the flight logs did not list the Check Pilot who signed off the checks conducted as a member of the crew. The 37 year old First Officer also had a CPL/IR with a valid C501/551 type rating. Information from the Operator indicated that his total flying time was "over 650 hours" including 475 hours on type. He had joined the operator five months prior to the accident and since then had flown 61 hours in the accident aircraft. Prior to the flight sequence on the night of the accident, it was noted that the two pilots had flown together on one previous occasion for two sectors.
It was established that the accident flight had left Asturias after just 10 minutes on the ground after the flight from Porto, the crew having called Santiago APP en route to ask about the weather there. Departure from Asturias was found to have been made without enough fuel on board to reach the nominated diversion, Vitoria, despite the fact that the Santiago TAF issued at 0100L and valid for the period around the ETA included a 40% probability of periods of visibility reduced to 500 metres in Fog. In this matter, it was noted that as fuel uplift had not been pre-requested, a considerable delay would have been incurred at a time when the crew were likely to have recognised the chances of fog were quite likely to increase as time progressed.
Eighteen minutes after take off, the crew established contact with Santiago APP who passed the current (0530L) METAR - Wind Calm, 4000metres visibility in mist, FEW at 600 feet and Temperature and Dew Point both 13º C. APP then cleared the aircraft to the 10 mile fix for the runway 17 ILS. After descent clearances from APP, the crew were transferred to TWR and, after advising they were en route to a 10 mile final for Runway 17, the aircraft was cleared to land with the wind given as calm. Three minutes later, the COAPAS-SARSA system detected an ELT activation near the airport. On being notified of this 16 minutes later and being unable to contact the aircraft, the TWR controller asked airport operations to check to see if the aircraft was at its usual parking position and after being advised that it was not, activated the emergency procedure. The Airport RFFS subsequently located the wreckage at an elevation of 1200 feet along the extended centreline of the runway 1 nm before the 17 threshold and about 200 metres prior to the on-track Santiago (STG) DVOR/DME.
The Santiago airport weather office advised that around the time of the accident, there had been "intervals of reduced visibility caused by fog banks" and that this was a very common occurrence with "Fog banks created in the valleys around the airport coming into visual range at various times and from different directions" whilst usually being "confined to the bottoms of neighbouring valleys and not visible from the airport until they move in one direction or another", often rapidly. The RVR at the 17 threshold at the time of the accident was 1500 metres and about to drop below Cat 1 ILS limits and remain there to and through sunrise one hour later.
The available radar trace of the approach flown was examined and it was found that:
- Although cleared to a 10 mile fix, the aircraft flew to a 6 mile fix which is co-incident with the FAF.
- having joined the ILS LOC from below the GS, the aircraft never captured the GS but instead had remained below it and made a descent at a similar angle but remaining about 300 feet below it. This vertical profile led to the position of the VOR rather than to the runway TDZ.
- The ILS procedure required a go around to be made if the required visual reference had not been acquired by a Cat B aircraft by 1406 feet QNH which would have been 1.6nm before the VOR.
- This point would have been equivalent to 0.6nm on the ILS DME which was beyond the point where ground impact occurred.
- rates of descent until 2nm from the runway were about twice those which would be expected for a stabilised approach and should have led to a go around.
The Investigation considered the above in conjunction with other information, including the finding that the First Officer's ILS frequency had been wrongly set and that the LOC flag on his HSI was defective and permanently in view. It was concluded that the most likely explanation for the premature descent was that the VOR DME instead of the ILS DME had been put on the Captain's HSI by the inadvertent activation of the 'HOLD' option by the First Officer trying to resolve the lack of an ILS display due to his mis-tuned NAV2 box. This would have led the Captain to believe that "he was one mile closer to the runway (than he was), which could have made him increase their descent rate sharply to capture the glide slope". It was, though, "not known why the Captain decided to make the approach without the aid of the glide slope and to go by distances and altitudes only". However, it was considered that the circumstantially evident lack of sighting of terrain prior to impact could have been attributed to descent into a fog bank in the final stages.
Noting that the operator had a valid AOC and an AESA-approved Operations Manual, the Investigation noted that:
- The approved Operations Manual was neither wholly compliant with EU-OPS nor appropriate to the operations being conducted. In particular, the aircraft operated were able to be flown by a single pilot but the AIRNOR Operations Manual (Type) Volume (Part B) was found to be a simple copy of the generic AFM. The company did not have any Standard Operating Procedures (Standard Operating Procedures (SOPs)) and although there were two pilots on board the accident flight as required by the applicable passenger transport regulations, no evidence was found of any trained or documented distinction between the duties of the PF and those of the PM nor of any procedures to ensure coordination of their actions.
- Although there was no documented evidence that the aircraft had not been airworthy, it was concluded that at the time of the accident, "the aircraft had several (potentially relevant) deficiencies, though their existence and resolution by maintenance could not be confirmed through the entries made by crews in the log book". It was noted that authorisations held by the 54 year-old Technician who maintained the accident aircraft included all those which would be expected except that for avionics maintenance privileges (the B2 category). The effect of this was that any avionics defect recorded in the aircraft Technical Log at base would ground the aircraft pending qualified assistance.
- The accident flight crew had been "on call" between 1300 and 2300 local time and had been notified of the flying duty required 20 minutes prior to the end of the on-call period. Despite being in accordance with the prevailing flight time limitations, it was noted that the sequence of flights to follow would "take place at a time of day more associated with sleep" and could have "contributed to an increased sensation of fatigue and drowsiness". In particular, it was considered that the final sector leading to the accident "may have been characterised by excessive fatigue....in combination with the complacency caused by arriving at their destination" and noted that "crew fatigue studies have shown a propensity toward more errors under these circumstances".
Although in the circumstances it would not have made any difference, the delay on the part of ATC in formally activating the 'Alert Phase' for an overdue aircraft was noted - this being required "within 5 minutes after the expected landing time".
The formally documented Causes and Contributory Factors identified by the Investigation were as follows:
Causes: The ultimate cause of the accident could not be determined. In light of the hypothesis considered in the analysis, the most likely scenario is that the crew made a non-standard precision approach in manual based primarily on distances. The ILS frequency set incorrectly in the first officer’s equipment and the faulty position indicated on the DME switch would have resulted in the distance being shown on the captain’s HSI as corresponding to the VOR and not to the runway threshold. The crew shortened the approach manoeuvre and proceeded to a point by which the aircraft should already have been established on the localiser, thus increasing the crew’s workload. The crew then probably lost visual contact with the ground when the aircraft entered a fog bank in the valleys near the airport and did not realise they were making an approach to the VOR and not to the runway.
- The lack of operational procedures for an aircraft authorised to be operated by a single pilot (to be) operated by a crew with two members.
- The overall condition of the aircraft and the instruments and the crew’s mistrust of the onboard instruments.
- The fatigue built up over the course of working at a time when they should have been sleeping after an unplanned duty period.
- The concern with having to divert to the alternate without sufficient fuel combined with the complacency arising from finally reaching their destination.
Six Safety Recommendations were made as a result of the Investigation as follows:
- that AIRNOR develop a specific plan that would ensure that the crews annotate all the discrepancies of the aircraft in the Aircraft Technical Log as soon as they are detected. (REC 09/15)
- that AESA revise its supervisory policies for both operations (Safety of National Aircraft Program - SANA) and aircraft (Aircraft Continuing Airworthiness Monitoring - ACAM) to establish criteria and define procedures for inspections in line with the objectives that are actually being pursued in terms of safety standards. (REC 10/15)
- that AIRNOR establish the operational procedures required to operate in each of its aircraft based on the equipment specific to each and using clear and common criteria for weather conditions, fuel planning and stabilized approaches (REC 11/15)
- that AESA take the initiative so as to establish as mandatory, following international guidance in ICAO Annex 10, for all operators to register the data from ELTs. (REC 12/15)
- that DGAC, at the initiative of AESA, establish as mandatory, following international guidance in ICAO Annex 10, for all operators the registration of the data from ELT. (REC 33/15)
- that ENAIRE (the ANSP, formerly AENA) establish the procedures needed to remind control personnel during refresher training of the emergency phase and of the obligation to monitor the operation of aircraft operating in and around the airport. (REC 13/15)
The Final Report was approved on 24 June 2015 and made available in English translation.