Scheduled Revenue Flight

Findings:
- The licenses and qualifications held by the flight crew, flight and duty times, the documented technical status of the aircraft and the aircraft mass and balance had no influence on the sequence of events
- The flight crew planned the flight from BGKK to BGGH with the destination alternate BGSF
- The latest BGGH TAF before departure from BGKK indicated marginal weather conditions (strong winds, low visibility and low cloud base) for a successful approach and landing at BGGH
- The forecasted weather conditions at the expected approach time at BGGH were below preplanning minima (use of two destination alternate aerodromes)
- The actual weather conditions at BGGH and enroute weather briefings were equivalent to the forecasted weather conditions
- With reference to the operator’s aerodrome and procedure briefing and the latest reported wind conditions from Nuuk AFIS before landing, a landing was prohibited
- Strong winds and moderate to severe orographic turbulence from the surrounding mountainous terrain increased the flight crew load
- On approach, the flight crew had difficulties of maintaining stabilized approach parameters
- The flight crew most likely suffered from task saturation and information overload
- No flight crew call outs on divergence from the operator’s stabilized approach policy were made
- An optimum crew resource management was not present
- Important low altitude stabilized approach parameters like airspeed, bank angle and runway alignment were not sufficiently corrected
- The flight crew was solely focused on landing and task saturation mentally blocked a decision of going around
- A divergence from the operator’s stabilized approach policy caused an unstabilized approach and a hard landing leading to an excess load of the right MLG at touchdown
- The right MLG fuse pin sheared as a result of overload
Factors:
- A divergence from the operator’s stabilized approach policy caused an unstabilized approach and a hard landing leading to an excess load of the right MLG at touchdown
- The right MLG fuse pin sheared as a result of stress
Summary:
Adverse wind and turbulence conditions at BGGH led to flight crew task saturation on final approach and a breakdown of optimum cockpit resource management (CRM) resulting in a divergence from the operator’s stabilized approach policy.
The divergence from the operator’s stabilized approach policy caused an unstabilized approach and a hard landing leading to an excess load of the right MLG at touchdown. According to its design, the right MLG fuse pin sheared as a result of stress.

Comprehensive technical examination of the nose wheel steering on OY-NPB uncovered no single causal factor, but some indications of unsatisfactory maintenance. Irregularities that alone or in combination could have caused a temporary fault with the steering were present. The Accident Investigation Board believes that a temporary fault caused the nose wheel to unintentionally lock itself in a position towards the right. No other defects or irregularities that could explain why the aircraft veered off the runway were found. The AIBN reported that the same fault had occurred 6 days earlier as well, during that encounter the captain managed to disconnect nose wheel steering quickly enough to regain control. Maintenance could not replace the fault and the aircraft was released to service.

The following findings were identified:
- The LEFT MAIN LANDING GEAR ASSEMBLY (PN D23189000-19 and SN MN1700) collapsed, failing with 5,130 cycles after the last overhaul.
- A specific component (pin) of the assembly connecting the landing gear to the airframe, the AFT PIVOT PIN (P / N D61000, S / N 25), broke on account of fatigue, whose onset was facilitated by a machining process carried out in the pin section transition region.
- The ANAC-approved ATR72 Series Aircraft Maintenance Program of the TRIP Linhas Aéreas company read that the LEFT MAIN LANDING GEAR ASSEMBLY had to undergo overhaul every eight years or 18,000 cycles.
- On 27 February 2009, the PR-TTI landing gear was removed and, on 09 March 2009, was sent to be overhauled by the AV Indústria Aeronáutica Ltda. It had 31,684 cycles since new and 18,095 cycles since the last overhaul.
- AV Indústria Aeronáutica Ltda. was homologated for conducting such inspection, as specified in the List attached to the Addendum, Revision no. 11, dated 05 January 2009, and accepted by means of the Official Document no. 0173/2009-GGAC/SAR, issued by the Civil Aviation Authority.
- The AV Indústria Aeronáutica Ltda. company disassembled the legs of the landing gear, and outsourced some of the tasks for not possessing technical knowledge and/or appropriate machinery (necessary for the process of reconditioning the AFT PIVOT PIN (D61000 SN 25).
- Two of the three companies outsourced by AV Indústria Aeronáutica Ltda. were not homologated by the Civil Aviation Authority.
- The AV Indústria Aeronáutica Ltda. company conducted external audits of the three companies involved in the overhaul.
- The audits carried out by AV Indústria Aeronáutica Ltda. were not sufficient to identify that the contractors lacked qualified personnel, manuals and the machinery necessary to work with aeronautical products.
- The AV Indústria Aeronáutica Ltda. Technical Manager did not supervise the overhaul inspections and services performed by the contracted companies.
- The AFT PIVOT PIN (D61000 SN 25) is part of the assembly that connects the landing gear to the airframe.
- All revision tasks were described in the manuals of the manufacturer.
- The AFT PIVOT PIN (D61000 SN 25) failure-analysis report stated that the PRTTI aircraft left main landing gear collapsed on account of fatigue, whose onset was facilitated by a machining process carried out in the section transition region of the pin.
- The manufacturer's maintenance manual did not refer to any machining work in that region of the pin.
- In only one stage of the pin reconditioning process was it possible to observe that a machining task was required, namely, the Grinding of chromium.
- The lack of capacitation and training of the subcontractors’ professionals for handling aircraft material hindered the execution of an efficient maintenance work as prescribed by the manufacturer's manual, culminating in inadequate machining during the maintenance process.
- The lack of an effective process of supervision, both on the part of TRIP Linhas Aéreas and on the part of the other contractors and subcontractors allowed the existing maintenance services’ latent failures not to be checked and corrected, in a way capable of subsidizing, in an adequate and safe manner, the execution of the landing gear maintenance service.
- The process of supervision of the TRIP Linhas Aéreas and the AV Indústria Aeronáutica Ltda. companies by the Civil Aviation Authority, prescribed by specific legislation in force, was not enough to mitigate the latent conditions present in the accident in question.
- According to the technical opinion issued by the DCTA, the AFT PIVOT PIN (D61000 and SN 25) presented fracture surfaces with ± 45º inclination, as well as a flat area with multiple initiations, indicative of a fracture mechanism related to fatigue. In examinations of the external surface of the pin, in a region close to the fatigue fracture, cracks were observed that had initiated from scratches created by an inadequate maintenance machining process. In the region where the overload-related fracture occurred, it was also possible to identify that the machining process had modified the profile of the part in the section transition region, by producing a depression. Thus, it can be said that the AFT PIVOT PIN (D61000 and SN 25) of the PR-TTI left main gear broke on account of fatigue, whose onset was facilitated by an inadequate machining process that had been performed in the section transition region of the pin.

The following findings were identified:
1) Weather conditions existing at the time of the event, during the approach to the runway the aircraft was operated slightly above the stall speed and a major change in wind speed could cause a stall. The altitude at which the windshear occurred, and the reaction time of the pilot and the responsiveness of the aircraft determined whether the descent could be arrested in time to avoid an accident.
2) No published descent procedures were performed, possibly misinterpretation of Flight Instruments (altimeter, airspeed indicator).
3) During the descent to the VOR/DME for runway 20 and 02, the pilot in command (PIC) did not check his approach chart, and did not continually consult the first officer on the altitude and course.
4) There was no adequate communication between crew; deficient CRM (No approach briefing was made for any of the two approaches).
5) The aircraft was configured for landing with flaps fully down (flap 42) at a very long distance from the track without having it in sight. It is noteworthy that the aircraft will not respond to an adverse condition windshear as it appeared at that time with such a configuration. It should be noted that in both approaches it is mandatory to perform a 'circling' procedure.

Loss of control during an attempted go-around initiated below Decision Height (200 feet) in Instrument Meteorological Conditions.
The following factors were considered as significant:
- The approach was continued in conditions of poor visibility below those required.
- The descent was continued below the Decision Height without adequate visual reference being acquired.
- Uncoordinated operation of the flight and engine controls when go-around was attempted
- The engine power-levers were retarded below the normal in-flight operational range, an action prohibited in flight.
- A power difference between the engines became significant when the engine power levers were retarded below the normal in-flight range.
- Tiredness and fatigue on the part of the Flight Crew members.
- Inadequate command training and checking.
- Inappropriate pairing of Flight Crew members, and
- Inadequate oversight of the remote Operation by the Operator and the State of the Operator.

Bad weather conditions for the aircraft and inappropriate actions by cockpit crew to confront the situation is the main cause of the accident. The following contributing factors were identified:
- The old technology of aircraft systems,
- Absence of a suitable simulator for adverse weather conditions,
- Failure to correctly follow the operating manual by the flight crew,
- Inadequate cockpit resources management (CRM).

A short circuit emerged while the aircraft generators were connected to the aircraft's electrical system after start-up of the engines, via an APU. The short circuit caused a strong fire in the generators compartment in the tail which spread rapidly through the fuselage. The cause of the fire was an electrical arc produced by electrical currents exceeding ten to 20 times the nominal loads when two generators not synchronized with each other were brought online but got connected together instead of being connected to parallel busses. The following contributing factors were identified:
- Poor technical conditions of contacts TKS233DOD responsible for connecting the generators with the electrical busses, that were damaged by prolonged operation without maintenance. A contact normally open was welded and fractured insulation material moved between contacts that are normally closed. These abnormal contact positions led to the connection between #2 and #3 generators.
- Differences in the schematic diagrams of generator 2 and generators 1 and 3. When the switch is moved from "check" to "enable" with no delay in the "neutral" position generator 2 is brought online without time delay which leads to increased wear of normally closed contacts in the TKS233DOD unit.
- The specific design of the electrical systems to ensure power supply to each bus from either the APU or either engine integrated drive generator.

The cause of the accident was the unwise decision taken by the crew to descend without taking the harsh mountain terrain into consideration. Controlled flight into terrain.