Copa Airlines Flight 201

Copa Airlines Flight 201 was a passenger flight from Tocumen International Airport in Panama City, Panama to Alfonso Bonilla Arágon International Airport in Cali, Colombia. On 6 June 1992, the Boeing 737-204 Advanced operating the route entered a steep dive, desintegrated in mid-air and crashed into the gap of the Darién Gap 29 minutes after takeoff, killing all 47 people on board. The crash was caused by faulty instruments readings. Flight 201 is the deadliest crash in Panamanian aviation history, and the first and only fatal crash in the history of Copa Airlines.

Aircraft and crew
The plane was a 12-year-old Boeing 737-204 Advanced, registration HP-1205-CMP, piloted by capitain Rafael Carlos Chial (53) and First Officer Cesareo Tejada (25) with 5 Flight Attendants on this flight. Copa 201 was carrying 40 passengers and 7 crew. The jet was manufactured in 1980 and entered service with Britannia Airways bearing tail number G-BGYL. The aircraft was acquired by Copa Airlines as a result of the leasing agreement that both companies had in the 1990s, and the aircraft still bore a hybrid Britannia/Copa livery (still wore Britannia stripes, but with "Copa" titles on the forward fuselage and tail, and the Panamanian flag on the middle part of the fuselage) at the time of the accident.

The crash
Flight 201 took off from runway 21L at Tocumen International Airport in Panama City at 20:37 (8:37 p.m.) local time as a scheduled passenger flight to Cali, Colombia, with 40 passengers and seven crew members. Among the passengers were Colombian merchants conducting business in Panama. At 20:47 (8:47 p.m.), about 10 minutes after takeoff, Captain Chial contacted Panama City Air Traffic Control, requesting weather information. The controller reported that there was an area of very bad weather 30–50 miles (50-80 kilometres) from their position.

At 20:48 (8:48 p.m.), Captain Chial made another radio contact requesting permission from Panama City ATC to fly a different route due to the severe weather ahead. The new route would take the plane over Darién Province. 1 minute later, at 20:49 (8:49 p.m.), Panama City Control Center received a third message from Captain Chial, who reported reaching cruising flight level of 250 (25,000 feet; 7620 meters), and at 20:54, the captain reported problems with the airplane and made a request to turn back to Tocumen, which was granted.

However, at 20:56 (8:56 p.m.), 2 minutes later, while flying at an altitude of 25,000 feet (7,620 metres), Flight 201 entered a steep dive at an angle of 80 degrees to the right and began to roll uncontrollably while accelerating towards the ground. Despite the attempts by Captain Chial and First Officer Tejada to level off, the airplane continued its steep dive, until it exceeded the speed of sound and started to break apart at 10,000 feet (3,048 metres). Most of the bodies had their clothes torn off and were thrown away from the aircraft. Flight 201 crashed into a jungle area within the Darien Gap at 486 knots (560 miles per hour, 900 kilometres per hour), killing any remaining person still aboard.

At 20:57 (8:57 p.m.), Tocumen Air Traffic Control tried unsuccessfully to make contact with flight until it received a radio message from a KLM DC-10 aircraft that was approaching the airport, reporting that they intercepted a distress signal from Flight 201's transponder in an area between the Colombian border and Darien Province, several kilometres away from their position. After several unsuccessful attempts to contact the lost plane, Tocumen ATC finally declared a full emergency in the airport and informed the Colombian ATC centre at Bogota about the missing plane. At dawn the next day, search aircraft were sent to Flight 201's last known position.

After 8 hours, searchers spotted the first pieces of wreckage in the jungle of the Darien Gap. Because of the remoteness of the area and the difficulty of access, it took rescue personnel 12 hours to reach the site.

Because the bodies of the victims and various parts of the aircraft's fuselage were scattered in a radius of 10 km (6.2 miles), the recovery process was extremely difficult. After investigators reached the crash site, the investigation to find the cause of the crash began.

Investigation
The cockpit voice recorder was recovered and flown to Panama City, then to the United States, for analysis by the National Transportation Safety Board. However, NTSB analysts discovered that the tape was broken due to a maintenance error. Crash investigators had better luck with the flight data recorder, which showed the plane was in a high-speed dive before breaking up.

The trouble was later traced to a faulty wiring harness in the Attitude Director Indicator (ADI) instruments. The wires were frayed due to damage by long term over-stress, which caused an intermittent short circuit in the flow of data from the pilot side Vertical Gyro (VG), VG-1, to the pilot side ADI.

This issue was compounded on the accident flight. There are two ADI displays, fed independently by their own VG – one ADI/VG pair for the pilot, a separate pair for the co-pilot. In case one of the VG has a problem, the crew can manually switch either ADI to use the other VG. The switch of the Captain's ADI was found at the scene of the accident in the "Both on VG-1" position, feeding both of the ADI from the same, intermittently faulty, pilot side VG.

As a consequence, both the ADI would momentarily stay unchanged (no new data making it through), leading the crew to believe the plane was still flying in a particular attitude, thereby prompting a further control input by the crew, expecting the ADI to show that they had achieved the new attitude as requested. In essence, the ADI told the crew the plane was still banking left, thereby prompting more pilot input to bank right. This reaction rolled the aircraft to almost 80 degrees and caused it to go into a steep dive, with no chance for recovery.

The investigation team also found that the backup ADI (Stand-by) was probably available to the pilots during the intermittent failure of the main instruments systems (the post-impact damage of the Stand-by indicator showed that it was operating properly up to impact with the ground), but due to an ineffective cross-checking procedure done by the pilots, the backup ADI was not used correctly to identify the problem and select a reliable source of attitude information.

Another factor contributing to the crash was that the Copa Airlines' ground training simulator program was ineffective, as it did not present enough information relating to the differences between aircraft and crew resource management in order to give to the flight crew knowledge to overcome intermittent attitude indicator errors and to maintain control of an aircraft with the ADI/VG auxiliary instruments. Moreover, on the accident aircraft, the pilots were trying to apply what they had learned in the simulator relating to this issue, but due to the movement of the ADI's switch to the position of "Both on VG-1" and the insufficient information during their training; the reference from VG-2 was lost and the pilots were unable to identify the problem as a consequence.

Another factor contributing to the crash was the non-standard cockpit configurations between aircraft in the fleet of the company, including inconsistencies between aircraft and the simulators used for training. This caused confusion to the pilots about determining the setting of the ADI switches for the aircraft that was being operated at the time.

Despite bearing some similarities to other incidents related to the Boeing 737 during the 1990s (such as United Airlines Flight 585), the possibility of rudder deflection in flight was discarded as a possible cause of the crash. However, Flight 201 was registered on the category of "accidents related to suspicious rudder deflection".

Eyewitness accounts
In the morning of the next day, Colombian and Panamanian radio stations were reporting that some residents of Tucutí and other villages nearby to the crash site said that on the night of the accident they felt a very strong explosion, meanwhile others said that they saw a burning object that was falling from the sky towards the jungle.

However, these reports were eventually dismissed by the head of Panama's civil aviation authority, Zosimo Guardia.

Media coverage
A year after the crash, the story of the crash of Flight 201 and its investigation was featured in a WGBH, BBC, and NDR documentary. It was screened in the United States in the PBS NOVA series as Mysterious Crash of Flight 201 on 30 November 1993, and in the United Kingdom in the Horizon series as Air Crash - The Deadly Puzzle on 14 February 1994.

The crash was also the subject of a Season 14 episode of the Discovery Channel/National Geographic series Mayday. The episode featuring Flight 201, titled "Sideswiped", premiered in March 2015.