Pakistan International Airlines Flight 661 was a Pakistani domestic passenger flight from Chitral to Islamabad, operated by Pakistan's flag carrier Pakistan International Airlines. On 7 December 2016, the aircraft serving the route, an ATR 42-500 twin-turboprop, crashed near Havelian following an engine failure. All 47 people on board died, including singer-turned-preacher and entrepreneur Junaid Jamshed, and the Deputy Commissioner of the District of Chitral.
Four years after the crash, Pakistan Aircraft Accident Investigation Board (AAIB) published the result of their investigation. In the final report, the crash was described as a unique case and the first ever of its kind in the entire operational life of ATR aircraft. The aircraft's left engine had failed mid-flight and the aircraft's safety system prevented the pilots from resolving the issues, which led to the sudden appearance of a huge amount of drag on the left side. The bizarre nature of the emergency that the crew faced eventually caused them to lose control. The investigation further revealed that faulty maintenance practices within PIA were to blame for such failures and the issue had been allowed to happen by weak oversight by the airline and the nation's aviation regulatory body.
The complex nature of the crash led to the issuance of several recommendations, two of which were urgent enough that mentioned parties were asked to comply immediately. Following the discovery of loopholes within CAA oversight, AAIB ordered authorities to impose stricter monitoring regarding airworthiness and airliner operation in the country. Pakistan's CRM training system was asked to be revamped. While extremely remote, there were also fears from the investigators about the possibility of another similar crash in the future. The manufacturer of the aircraft, ATR, was asked to include a specific procedure to safely recover from the situation.
Background
Aircraft
The aircraft involved in the accident was an ATR 42-500, serial number 663, registration AP-BHO, delivered to Pakistan International Airlines (PIA) in 2007. The aircraft was part of the replacement aircraft for PIA's aging Fokker fleet.
In 2009, the aircraft was damaged during a landing attempt at Lahore, but was subsequently repaired and returned to service. It sustained an engine failure in 2014, but the engine was replaced and no further problems were reported. By the time of the crash, it had recorded more than 18,700 flight hours since joining PIA's fleet and had last undergone certification in October 2016.
Passengers and crew
Forty-two passengers, including two infants, were on board the aircraft. The passengers included 39 Pakistani citizens, and one Austrian, one Chinese and one South Korean national. The passengers included Pakistani singer-turned-preacher Junaid Jamshed who was traveling with his wife Nahya Junaid. Shahzada Farhad Azis, a member of Chitral's traditional royal family who was flying with his wife and daughter, Deputy Commissioner of Chitral District Osama Ahmed Warraich, two sky marshals and an Aircraft Maintenance Engineer were also among the passengers. There were 20 Chitral residents on board.
The flight manifest showed that there were five flight crew: 43-year-old Captain Saleh Janjua, 40-year-old First Officer Ali Akram, 26-year-old trainee pilot Ahmed Janjua (no relation to the captain), and two flight attendants Sadaf Farooq and Asma Adil. Captain Janjua was reported to be an experienced pilot with over 12,000 flight hours during his career. He was also a type-rated instructor for ATR aircraft. First Officer Akram was also an experienced pilot with over 3,600 flight hours on the ATR-42 while trainee First Officer Ahmed Janjua joined PIA in 2014 and had accrued a total flying experience of more than 1,400 hours on the ATR-42.
Flight
Flight 661 was a flight from Chitral, the capital of Chitral District located in the mountainous region of Khyber Pakhtunkhwa, to Pakistan's capital of Islamabad. The flight was scheduled for twice a week and was expected to take off at 15:30 PST. The expected time of arrival in Islamabad's Benazir Bhutto International Airport was at around 16:40 local time.
The aircraft left Chitral Airport's Runway 20 at 15:38, with trainee first officer Ahmed Janjua as the pilot flying and Captain Saleh Janjua as the co-pilot and pilot monitoring. The trainee first officer was flying for route familiarization, while another cockpit crew, First Officer Akram, was sitting at the back of the cockpit on the jumpseat to observe him as well. The weather in the region was fine and there was no recorded significant activity on the radar.
Cruising at FL135, the airspeed was stabilized at 186 knots. After everything was set, Captain Janjua decided to make an announcement to the passengers.
Start of anomaly
While he was making the announcement, he was interrupted by the trainee first officer, who informed him that an alert of a mechanical fault on the Propeller Electrical Control-1 (PEC-1) had suddenly appeared. Captain Janjua asked the crew to read the procedure checklist for such issue and ordered the trainee first officer to call the flight engineer in the cabin to the cockpit. He turned his attention back to the PA system to complete his announcement. After completing it, he asked the crew to read the checklist again. The crew decided to reset the PEC-1. By this time, the airspeed had dropped to 146 knots (270 km/h; 168 mph).
The alert appeared for the second time. First Officer Akram, who was sitting on the cockpit jumpseat, asked the throttle lever to be moved to 100% and to override the PEC, while Captain Janjua asked the trainee first officer to read the checklist once more. The lever was moved to 100% while the PEC was put into a reset again for three times, but the fault stayed on. Failing to resolve the issue, they decided to switch off the PEC. Meanwhile, the airspeed started to increase due to the lever setting.
In accordance with PIA's policy, Captain Janjua took over the controls from the trainee first officer while First Officer Akram switched his seat with the latter pilot, becoming the co-pilot for the rest of the flight. Shortly after, Captain Janjua informed the controller in Cherat about his intention to switch to Islamabad Control. The controller approved his request and asked the crew to report back once they had reached Islamabad.
Shortly after, the pilots began to notice an abnormal sound coming from the engines. The torque of the left engine rapidly dropped from 75% to 0%, while the speed of the left propeller quickly accelerated to 102%. The airspeed immediately dropped to 154 knots (285 km/h; 177 mph) and the aircraft started to drift towards the left. Captain Janjua announced that they had lost the left engine and attempted engine feathering. The fuel flow to the engine was shut off and the engine was shut down. The crew successfully slowed the loss of airspeed. The speed of the left propeller then decreased, hovering at around 25%.
Struggle for control
At 16:11 local time, Captain Janjua ordered First Officer Akram to request permission for the flight to descend and to make a mayday call. During this time, the speed of the left propeller was still relatively low, with an amount of below 25%. The speed then gradually increased to 50% in 26 seconds before it suddenly jumped to 120 – 125% in just 8 seconds. The cockpit crew initially didn't notice the change in the sound of the propeller, but when the propeller suddenly accelerated it took the crew by surprise as the noise quickly intensified, prompting Captain Janjua to ask the crew about the sound. While he was asking, the sound continued to become louder and a massive drag force had just been generated on the left side of the aircraft.
The heavy drag led the autopilot to be disconnected and caused the aircraft to start banking gradually to the left. The aircraft was then manually flown by the pilots. Due to the massive left drag, Captain Janjua had to apply excessive force to the rudder and aileron to keep the aircraft from being pulled towards the left. Despite the huge input that he had applied, his efforts were in vain as the aircraft kept moving to the left. In addition, the airspeed was constantly decreasing, creeping towards the aircraft's stall speed.
The crew didn't understand the reason for the aircraft's unusual behaviour. They noticed that their attempted feathering of the left engine earlier had failed and decided to try another attempt of engine feathering, but it failed again. In his effort to stabilize the flight, Captain Janjua added more thrust to the right engine several times, but his actions somehow aggravated the situation as it worsened the condition.
First plunge and initial recovery
The faulty engine suddenly fixed itself as the speed of the left propeller dropped from over 120% to just around 25% in seconds. In an instant, the massive drag force on the left side of the aircraft vanished. As Captain Janjua made excessive right turn inputs on the control column, the aircraft immediately banked to the right at a large angle, taking the crew by surprise. The aircraft flipped over, barrel-rolled, and then plunged for 5,100 feet (1,554 m) with the right wing perpendicular to the ground. This lasted a total of 24 seconds. Panicking, the crew repeatedly tried to save the aircraft from rolling by deflecting the aileron to the left. They eventually managed to regain control and level the wings.
The crew was clearly traumatized by the incident as they could be heard hyperventilating and their voices were trembling. First Officer Akram asked whether there was something wrong with the power. The other crew members were still confused about the exact cause of the aircraft's bizarre state. They were so terrified by the plunge that they couldn't have a structured discussion. Meanwhile, the speed of the left propeller had stabilized to under 5%. Despite this, a massive drag generated on the left side again as the blade pitch was in an angle that was close to a low pitch angle. The power lever was moved forward, but the airspeed kept decaying.
The state of the aircraft's performance had largely degraded. It was impossible for the crew to reach Islamabad unless they put the aircraft into a gradual descent, even though they were flying over a mountainous area. The crew reluctantly descended the aircraft to preserve the remaining airspeed, which was continuously decreasing. As they became closer to the ground, the crew tried to decrease the rate of descent, but as a result, this increased the depletion rate of the airspeed.
The trainee first officer at the back, fearing another plunge, repeatedly advised the crew not to put the aircraft into a bank. He requested that the captain maintains an altitude of 5,200 feet (1,585 m). Captain Janjua attempted to comply, but had to reduce the rate of descent, causing the airspeed to decrease and trigger the stick shaker. The crew then alerted the controller in Islamabad and declared multiple Mayday calls requesting priority landing.
Seeing the oncoming mountain, Captain Janjua desperately tried to turn the aircraft to the right. He was successful as the aircraft gradually turned, but the airspeed continued to deplete, causing stall warnings to blare inside the cockpit. Immediately afterwards, the aircraft started to turn to the left again. Their airspeed was at 156 knots (289 km/h; 180 mph) and their altitude was at 5,280 feet (1,609 m), with merely hundreds of feet being left from the ground.
Final plunge
Captain Janjua tried to stop the aircraft from turning to the left with great effort as the large drag on the left side had forced the crew to make large right input on the controls. The turn, however, became more uncontrollable and the airspeed continued to drop. The aircraft continued to lose its altitude and became nearer to the mountainous terrain. Captain Janjua tried hard to level the wings and to avoid the mountains by making excessive right turn input and modulating the thrust on the right engine, but he didn't realize that by that time it was not possible anymore for the aircraft to fly over the mountains. The TAWS warned the crew on the impending collision with terrain, while the crew desperately tried to save the aircraft from the mountains by holding the altitude. In doing so, the airspeed continued to decay further.
The aircraft finally reached a dangerously low speed and the stall warning sounded again inside the cockpit. At 850 feet (259 m) above ground, the left wing completely stalled and the aircraft banked 90 degrees to the left, nosediving into the mountain. It slammed onto terrain at a speed of 138 knots (256 km/h; 159 mph) and disintegrated. The aircraft crashed at about 16:15, leaving wreckage ablaze on the side of a hill between the villages of Saddha Batolni and Gug, near the Pakistan Ordnance Factory in Havelian in Khyber Pakhtunkhwa province about 90 kilometres (56 mi; 49 nmi) from the airport. The wreckage was reported to be strewn over an area about 2 kilometres (1.2 mi) across.
All 47 passengers and crew members were killed in the crash. This was the seventh aircraft accident resulting in hull loss sustained by PIA since 2000. Of the previous six, one resulted in fatalities; that of Pakistan International Airlines Flight 688 in 2006, in which 45 people died.
Coincidentally, the crash happened on International Civil Aviation Day.