Image: Wikipedia
A GOL Boeing 737-800 similar to the aircraft involved in the Brazilian mid-air collision
What are the possibilities of 2 airplanes colliding and landing safely?
Topher Barott from Quora asks the above question.
Mid-air collisions on commercial airliners are extremely rare. I believe Topher Barott is referring to commercial planes instead of collision between military aircraft.
In 1986, the collision between a DC-9 and a private aircraft over Cerritos, California highlighted the importance of mandating the use of TCAS (Traffic Collision Avoidance System) in aircraft.
TCAS basically shows a pilot of all the aircraft around and will let him know if the traffic is too close by annunciating a ‘TRAFFIC, TRAFFIC’ call out. When it comes on, pilots would look out for the traffic visually and react accordingly.
If there is a danger of colliding, the system will call out what he needs to do to avoid it with call outs like ‘CLIMB. CLIMB’ or ‘DESCEND, DESCEND’ with the amount of deviation.
If further action is required the TCAS will even call out ‘INCREASE RATE OF CLIMB/DESCEND’ The maneuver should be initiated manually by the pilot within seconds.
On 29 September 2006, a Brazilian Airlines Boeing 737 on route to Rio de Janeiro collided mid-air with an Embraer Legacy 600 business jet. The wingtip of the Embraer sliced off about half of the B737’s left wing. The 737 broke up in mid-air and crashed into an area of dense jungle, killing all 154 passengers and crew on board.
Despite sustaining serious damage to its left wing and tail, the Embraer Legacy jet landed with its seven occupants uninjured.
How could this happen when the planes were equipped with TCAS?
Investigation revealed that the collision avoidance system in the Legacy plane was not functioning thereby disabling the system’s ability to detect and be detected by conflicting traffic.
On 1 July 2002, a Russian TU-154 and Boeing 757 collided in mid-air over Germany. Prior to the collision, the TCAS was giving the right evasive commands but it was the interference of the air traffic official, who twice commanded wrongly for the airplane to dive which resulted in the accident.
On 12 November 1996, a Saudi Arabia Airlines Boeing 747 and a Kazakhstan National Airways Ilyushin IL-76 cargo plane collided around 100 km west of New Delhi. 349 lives were lost making it the worst deadliest mid-air collision.
Today with modern planes like the Airbus A350, the auto pilot is capable of handling an evasive action automatically when two planes are on a collision course.
As such, when the plane sense and imminent collision, it will automatically engage within 3-5 seconds.
With a fully operating TCAS, actual mid-air collisions are becoming a rarity. However, near misses have been occasionally reported but they were the cautionary part of the avoidance system.
Other than the Embraer Legacy business jet that landed safely after the collision with the B737, there were no commercial planes that have landed safely after a mid-air collision.
1. See a video on Gol Transportes Aereos Flight 1907 – Crash Animation 2 here
2. See another video on Mid-air Collision Over The Amazon Rainforest DISASTER BREAKDOWN