Scheduled Revenue Flight

On 25 December 2016, an ATR 72-600 aircraft registered PK-WGW was being operated by PT. Wings Abadi Airlines (Wings Air) as a scheduled passenger flight from Husein Sastranegara International Airport (WICC), Bandung to Ahmad Yani International Airport (WAHS), Semarang with flight number WON 1896. On board the aircraft were two pilots, two flight attendants and 68 passengers. There was no report or record of aircraft system malfunction prior to the departure. The aircraft departed from Bandung at 1734 LT (1034 UTC). The Pilot in Command (PIC) acted as Pilot Flying (PF) and the Second in Command (SIC) acted as Pilot Monitoring (PM). The flight from departure until commenced for landing approach was uneventful. At 1112 UTC, at night condition, the air traffic controller of Semarang Approach unit (approach controller) informed to all traffic that the rain was falling over the airport and the pilot confirmed whether the rain was heavy and was replied that it was slight rain. At 1115 UTC, the flight held over waypoint KENDA for separation with another aircraft and maintained altitude of 4,000 feet. Two minutes later, the flight was approved to descend to altitude of 3,000 feet. At 1118 UTC, the approach controller issued clearance for RNAV approach to runway 13 and advised the pilot to report when leaving waypoint KENDA. One minute later, the pilot reported leaving waypoint KENDA and the approach controller instructed to continue approach and to contact to the air traffic controller of Semarang Tower unit (tower controller). At 1120 UTC, the pilot advised to the tower controller that the aircraft was on final and the runway was in sight. The tower controller instructed to continue the landing approach and advised that the surface wind direction was 190° with velocity of 15 knots, altimeter setting 1,008 mbs and the runway was wet. At 1121 UTC, the tower controller had visual contact to the aircraft and issued landing clearance, the pilot read back the clearance and requested to reduce the approach light intensity. The tower controller reduced the light intensity and confirmed whether the intensity was appropriate then the pilot affirmed. At 1124 UTC, the aircraft touched down and bounced. After the third bounce, the pilot attempted to go around and the aircraft touched the runway. The tower controller noticed that the red light on the right wing was lower than the green light on the left wing. The aircraft moved to the right from the runway centerline and stopped near taxiway D. The tower controller realized that the aircraft was not in normal condition and pressed the crass bell then informed the Airport Rescue and Fire Fighting (ARFF) personnel by phone that there was aircraft accident near the taxiway D. At 1126 UTC, the pilot advised the tower controller that the aircraft stopped on the runway and requested assistance. The tower controller acknowledged the message and advised the pilot to wait for the assistance. While waiting the assistance, the pilot kept the engines run to provide lighting in the cabin. At 1129 UTC, the tower controller advised the pilot to shut down the engines since the ARFF personnel had arrived near the aircraft to assist the evacuation. Passenger evacuation completed at approximately 10 minutes after the aircraft stopped.

On 10 December 2016, JAV Boeing 737-400 Aircraft, registration JY-JAQ, operating a leased scheduled passenger flight SFW 502, on behalf of SAFI Airways under wet lease contract with the later call sign, departed a domestic flight from Herat Airport (OAHR), at 07:00 Z from RWY 36 to Kabul International Airport (OAKB) Afghanistan. At approximately 07:57:45 Z, the Aircraft touched down RWY 29 at Kabul. The aircraft departed Herat with 164 passengers ,07 Operating Crewmembers and 02 Engineers , Total on board were 173 person. As the flight approached OAKB, the crew received the automatic terminal information service (ATIS) from OAKB station at 07:45 Z indicating normal weather with visibility of 6 Km, temperature 07 degrees Celsius and wind of 150/07. The Aircraft was configured for landing with the flaps set to 30, and approach speed selected of 152 knots (VREF + 10) indicated airspeed (IAS). The Aircraft was cleared to approach ILS 29. The Aircraft was vectored by the radar for RWY 29. Air traffic control cleared the flight to land, with the wind reported to be 190 degrees at 15 knots. The crew stated that a few seconds after the touchdown, they felt the aircraft vibrating, during which they applied brakes and deployed the reverse thrust. The vibration was followed by the aircraft rolling slightly low to the right. It later came to a full stop left of the runway centre line, resting on its left main landing gear and the right engine, with the nose landing gear in the air. The occurrence occurred at approximately 3,806 ft / 1,160 m past the threshold. The PIC declared Emergency to the ATC and the cockpit crew initiated an evacuation command from the left side of the aircraft. Evacuation was successfully accomplished with No reported injuries. Kabul airport RFF reached the occurrence aircraft and observed the smoke coming from right side and immediately deployed their procedures by spraying foam on engine # 2. The aircraft sustained substantial damage due to the separation of the right main gear resulting on the aircraft skidding on the right engine cowlings. No injuries were sustained by any of the occupants during the occurrence or the evacuation sequence. Operating crew of the incident flight were called by the Afghani Civil Aviation Authority (ACAA) for interview and medical examination (alcohol and drugs, blood test). No injuries were reported by the occupants of the Aircraft or the ground crew.

On 07 December 2016 morning, after a routine daily inspection at Benazir Bhutto International Airport (BBIAP) Islamabad, Pakistan International Airlines (PIA) aircraft ATR42-500 Reg No AP-BHO operated 05 flights (ie Islamabad to Gilgit and back, Islamabad to Chitral, Chitral to Peshawar and back). As 6th and last flight of that day, it took off from Chitral at time 10:38:50 UTC (15:38:50 PST) with 42 passengers (including 01 engineer) and 05 crew members (03 pilots and 02 cabin crew) aboard for Islamabad. It crashed after 42 minutes of flight at 11:20:38 UTC (16:20:38 PST) about 3.5 Nautical Miles (NM) SSE of Havelian, and 24 NM North of BBIAP Islamabad. All 47 souls aboard were fatally injured. The aircraft remained in air for about 42 minutes before crash (all timings in UTC). These 42 minutes have been split into three stages of flight, described hereunder:

(a) Initial Stage: From 10:38 to 11:04 (~26 minutes) degraded speed governing accuracy of the port propeller was evident in the DFDR data, but was apparently not observed by the cockpit crew. The flight stabilized at an altitude 13,500 feet AMSL and a cruising speed of 186 knots IAS (instead of expected 230 knots IAS). There were two latent pre-existing technical anomalies in the aircraft (a Fractured / dislodged PT-1 blade due to a known quality issue and a fractured pin inside the OSG), and one probable latent pre-existing condition (external contamination) inside the PVM of No 1 Engine. Digital Flight Data Recorder (DFDR) analysis indicates that No 1 Engine was degraded.

(b) Middle Stage (Series of Technical Malfunctions): From 11:04 to 11:13 (~09 minutes), a series of warnings and technical malfunctions occurred to No 1 Engine (left side) and its related propeller control system. These included Propeller Electronic Control (PEC) fault indications, followed by No 1 Engine power loss, and uncontrolled variation of its propeller speed / blade pitch angle abnormal system operation). The propeller speed which was initially at 82% (cruise setting) decreased gradually to 62% and later at the time of engine power loss it increased to 102% (and stayed at that value for about 15 to 18 seconds). It then reduced down to Non Computed Data (NCD) as per DFDR. At this point, (based on simulation results) the blade pitch angle increased (possibly close to feather position). Later, the propeller speed increased to 120% to 125% (probably caused due to unusual technical malfunctions) and stayed around that value for about 40 to 45 seconds. It finally showed an abrupt drop down to NCD again. At this point, (based on simulation results) the blade pitch angle may have settled at a value, different from the expected feathered propeller. During this unusual variation of propeller speed, there were drastic variations in the aircraft aerodynamic behaviour and sounds. The directional control was maintained initially by the Auto-Pilot. A relatively delayed advancement of power (of No 2 Engine) post No 1 Engine power loss, reduction of power (of No 2 Engine) for about 15 seconds during the timeframe when left propeller rpm was in the range of 120% to 125%, and once again a reduction of power towards the end of this part of flight, were incorrect pilot actions, and contributed in the IAS depletion. Auto-Pilot got disengaged. Towards the end of this part of flight, the aircraft was flying close to stall condition. No 1 Engine was already shutdown and No 2 Engine (right side) was operating normal. At this time, IAS was around 120 knots; aircraft started to roll / turn left and descend. Stick shaker and stick pusher activated. Calculated drag on the left side of the aircraft peaked when the recorded propeller speed was in the range of 120% to 125%. During transition of propeller speed to NCD, the additional component of the drag (possibly caused due to abnormal behaviour of left propeller) suddenly reduced. The advancement of power of No 2 Engine was coupled with excessive right rudder input (to counter the asymmetric condition). This coincided with last abrupt drop in the propeller speed. As a combined effect of resultant aerodynamic forces aircraft entered into a stalled / uncontrolled flight condition, went inverted and lost 5,100 feet AMSL altitude (ie from ~13,450 feet to 8,350 feet AMSL).

(c) Final Stage: The final stage of flight from 11:13 to 11:20 (~07 minutes) started with the aircraft recovering from the uncontrolled flight. Although blade pitch position was not recorded (in the DFDR – by design), and it was not possible to directly calculate that from the available data, a complex series of simulations and assumptions estimated that the blade pitch of left propeller may have settled at an angle around low pitch in flight while rotating at an estimated speed of 5%. Aircraft simulations indicated that stable additional drag forces were present on the left side of the aircraft at this time and during the remaining part of flight. Aircraft had an unexpected (high) drag from the left side (almost constant in this last phase); the aircraft behavior was different from that of a typical single engine In Flight Shutdown (IFSD) situation. In this degraded condition it was not possible for the aircraft to maintain a level flight. However, that level of drag did not preclude the lateral control of the aircraft, if a controlled descent was initiated. The aircraft performance was outside the identified performance envelope. It was exceptionally difficult for the pilots to understand the situation and hence possibly control the aircraft. Figure hereunder shows different stages of flight.

On October 28, 2016, about 1432 central daylight time, American Airlines flight 383, a Boeing 767-323, N345AN, had started its takeoff ground roll at Chicago O’Hare International Airport, Chicago, Illinois, when an uncontained engine failure in the right engine and subsequent fire occurred. The flight crew aborted the takeoff and stopped the airplane on the runway, and the flight attendants initiated an emergency evacuation. Of the 2 flight crewmembers, 7 flight attendants, and 161 passengers on board, 1 passenger received a serious injury and 1 flight attendant and 19 passengers received minor injuries during the evacuation. The airplane was substantially damaged from the fire. The airplane was operating under the provisions of 14 Code of Federal Regulations Part 121. Visual meteorological conditions prevailed at the time of the accident. The uncontained engine failure resulted from a high-pressure turbine (HPT) stage 2 disk rupture. The HPT stage 2 disk initially separated into two fragments. One fragment penetrated through the inboard section of the right wing, severed the main engine fuel feed line, breached the fuel tank, traveled up and over the fuselage, and landed about 2,935 ft away. The other fragment exited outboard of the right engine, impacting the runway and fracturing into three pieces. Examination of the fracture surfaces in the forward bore region of the HPT stage 2 disk revealed the presence of dark gray subsurface material discontinuities with multiple cracks initiating along the edges of the discontinuities. The multiple cracks exhibited characteristics that were consistent with low-cycle fatigue. (In airplane engines, low-cycle fatigue cracks grow in single distinct increments during each flight.) Examination of the material also revealed a discrete region underneath the largest discontinuity that appeared white compared with the surrounding material. Interspersed within this region were stringers (microscopic-sized oxide particles) referred to collectively as a “discrete dirty white spot.” The National Transportation Safety Board’s (NTSB) investigation found that the discrete dirty white spot was most likely not detectable during production inspections and subsequent in-service inspections using the procedures in place. The NTSB’s investigation also found that the evacuation of the airplane occurred initially with one engine still operating. In accordance with company procedures and training, the flight crew performed memory items on the engine fire checklist, one of which instructed the crew to shut down the engine on the affected side (in this case, the right side). The captain did not perform the remaining steps of the engine fire checklist (which applied only to airplanes that were in flight) and instead called for the evacuation checklist. The left engine was shut down as part of that checklist. However, the flight attendants had already initiated the evacuation, in accordance with their authority to do so in a life-threatening situation, due to the severity of the fire on the right side of the airplane.

During the takeoff roll from runway 15/33 at Dire Dawa-Aba Tenna Dejazmach Yilma Airport, the aircraft collided with wild animals. The captaint abandoned the takeoff procedure and initiated an emergency braking manoeuvre when the aircraft veered off runway and came to rest. All 80 occupants evacuated safely and the aircraft was damaged beyond repair.

On final approach to Belaya Gora Airport, the aircraft was too low and hit the ground. On impact, the right main gear and the nose gear collapsed. The aircraft slid for several yards before coming to rest in a snow covered field about 400 meters short of runway threshold and 300 meters to the left of the approach path. The propeller on the right engine was torn off and it appears that the fuselage was bent as well. All 33 occupants were evacuated safely. At the time of the accident, weather conditions were marginal with limited visibility caused by snow falls. It was reported the visibility was about 2,5 km at the time of the accident while the crew needed at least 4 km on an NDB approach.

On October 2, 2016, about 1157 Alaska daylight time, Ravn Connect flight 3153, a turbine powered Cessna 208B Grand Caravan airplane, N208SD, collided with steep, mountainous terrain about 10 nautical miles northwest of Togiak Airport (PATG), Togiak, Alaska. The two commercial pilots and the passenger were killed, and the airplane was destroyed. The scheduled commuter flight was operated under visual flight rules by Hageland Aviation Services, Inc., Anchorage, Alaska, under the provisions of Title 14 Code of Federal Regulations Part 135. Visual meteorological conditions prevailed at PATG (which had the closest weather observing station to the accident site), but a second company flight crew (whose flight departed about 2 minutes after the accident airplane and initially followed a similar route) reported that they observed unexpected fog, changing clouds, and the potential for rain along the accident route. Company flight-following procedures were in effect. The flight departed Quinhagak Airport, Quinhagak, Alaska, about 1133 and was en route to PATG.

The twin engine aircraft departed Goma on a regular schedule flight (service UNO830) to Beni, carrying eight passengers and two pilots on behalf of the Monusco, the United Nations Organization Stabilization Mission in the Democratic Republic of Congo. On approach to Beni-Mavivi Airport, the crew completed the approach checklist and elected to configure the aircraft but realized that the undercarriage would not extend. After the circuit breaker was reset, the crew was able to lower the landing gear manually and continued the approach with no reporting to ATC. After touchdown on runway 11, the aircraft rolled for about 450 metres when the right main gear collapsed. Out of control the aircraft veered off runway to the right, slid in a grassy area, crossed a ditch and came to rest near the apron. All 10 occupants evacuated safely and the aircraft was damaged beyond repair.

The approach to Siddharthanagar-Gautam Buddha Airport was completed in good weather conditions with a wind from the southeast at 4 knots and a 8 km visibility. After touchdown on runway 28, the twin engine aircraft was unable to stop within the remaining distance. It overran, lost its undercarriage and came to rest in bushes, some 110 metres past the runway end. All 32 occupants evacuated safely and the aircraft was damaged beyond repair.

The Cessna had departed about 3 minutes prior on a scheduled passenger flight and the Piper was en route to a remote hunting camp when the two airplanes collided at an altitude about 1,760 ft mean sea level over a remote area in day, visual meteorological conditions. The airline transport pilot and two passengers onboard the Cessna and the commercial pilot and the passenger onboard the Piper were fatally injured; both airplanes were destroyed. Post accident examination revealed signatures consistent with the Cessna's outboard left wing initially impacting the Piper's right wing forward strut while in level cruise flight. Examination revealed no mechanical malfunctions or anomalies that would have precluded normal operation of either airplane. Neither pilot was in communication with an air traffic control facility and they were not required to be. A performance and visibility study indicated that each airplane would have remained a relatively small, slow-moving object in the other pilot's window (their fuselages spanning less than 0.5° of the field of view, equivalent to the diameter of a penny viewed from about 7 ft away) until about 10 seconds before the collision, at which time it would have appeared to grow in size suddenly (the "blossom" effect). From about 2 minutes before the collision, neither airplane would have been obscured from the other airplane pilot's (nominal) field of view by cockpit structure, although the Cessna would have appeared close to the bottom of the Piper's right wing and near the forward edge of its forward wing strut. The Cessna was Automatic Dependent Surveillance-Broadcast (ADS-B) Out equipped; the Piper was not ADS-B equipped, and neither airplane was equipped with any cockpit display of traffic information (CDTI). CDTI data would have presented visual information regarding the potential conflict to both pilots beginning about 2 minutes 39 seconds and auditory information beginning about 39 seconds before the collision, providing adequate time for the pilots to react. The see-and-avoid concept requires a pilot to look through the cockpit windows, identify other aircraft, decide if any aircraft are collision threats, and, if necessary, take the appropriate action to avert a collision. There are inherent limitations of this concept, including limitations of the human visual and information processing systems, pilot tasks that compete with the requirement to scan for traffic, the limited field of view from the cockpit, and environmental factors that could diminish the visibility of other aircraft. Given the remote area in which the airplanes were operating, it is likely that the pilots had relaxed their vigilance in looking for traffic. The circumstances of this accident underscore the difficultly in seeing airborne traffic by pilots; the foundation of the "see and avoid" concept in VMC, even when the cockpit visibility offers opportunities to do so, and particularly when the pilots have no warning of traffic in the vicinity. Due to the level of trauma sustained to the Cessna pilot, the autopsy was inconclusive for the presence of natural disease. It was undetermined if natural disease could have presented a significant hazard to flight safety.