On November 12, 1996, the traffic flow in Indian airspace over Delhi was overloaded. Only one arrival route was used for approaching the airport, so the air traffic controllers had to separate arriving and departing aircrafts by their altitudes.

The Kazakhstan Airlines Ilyushin Il-76TD was flying from Shymkent to Delhi. There were 27 passengers on board, including tourists, and 10 crew members. The air traffic controller instructed the crew to descend to FL150 (about 4,570 meters) and informed about Boeing 747 flying towards, 300 meters below. It was an airplane of Saudi Arabian Airlines just departed from Delhi heading to Saudi Arabia. There were 312 people on board, including 23 crew members. Boeing crew received an instruction to maintain FL140 (about 4260 meters).

Ilyushin Il-76

The radars of air traffic control services at Delhi Airport did not display the current altitude of the planes. At the moment the controller saw the potential intersection of the routes of two airplanes, he expected that they would continue moving in different directions. But suddenly both dots on his monitor disappeared at the point of intersection.

Soon, the pilot of American military aircraft flying nearby contacted the controller and reported the following:

"We saw something to our right, looks like a big fireball something... looks like a big explosion."

The controller tried to reestablish communication with Il-76TD and Boeing 747, but there was no answer, only silence. The American crew transmitted:

"We see two fires trying to break to our right about 44 miles to your north west... passing through, we saw a big fireball in the cloud and I saw fire debris; Two distinct fires on the ground"

It was obvious that a collision had already occurred. The planes crashed at the distance of 74 kilometers from the airport. Rescuers found no survivors. In total 349 people died.

Reconstruction

The specialists investigated that the crew of Il-76 faced difficulties in communications with air traffic controllers. After receiving traffic information (it was about Boeing at FL140), the co-pilot being busy with other duties and listening to the frequency inattentively, got the wrong meaning of this message. He thought they were allowed to descend to FL140. The captain, apparently, perceived it in the same way and did not interfere with the control. The navigator also did not react to the continued descent. The radio operator knew the correct altitude, but from his seat in the cockpit he could not constantly monitor the actions of the pilots and indication of flight instruments.

Later the captain asked the crew at what altitude they must be. This confirmed that he wasn’t aware of the situation. The flight engineer added the misunderstanding by reporting that it was necessary to maintain FL140. The radio operator, however, immediately told: "maintain FL150, do not descend".

Just four seconds before the collision happened, the radio operator understood that the plane was at the wrong flight level and shouted that it was necessary to climb immediately to FL150. IL-76 had started to climb, but it was too late. Most likely, both planes were in the clouds and the crews did not have visual contact until the moment of the collision.

Reconstruction

As other circumstances also contributed to the disaster was the fact that a secondary surveillance radar, which provides air traffic controllers with information about the height of aircraft, wasn’t installed at Delhi Airport. In addition, there was no aircraft collision warning system on both planes.

As a result of the investigation, some recommendations were issued. Firstly, improving the ATC procedures in the airspace around Delhi. Secondly, improving the airport infrastructure. Thirdly, since that time the messages about other planes (traffic information) do not contain the altitude or flight level of this plane in order to prevent the possible misunderstanding.On November 12, 1996, the traffic flow in Indian airspace over Delhi was overloaded. Only one arrival route was used for approaching the airport, so the air traffic controllers had to separate arriving and departing aircrafts by their altitudes.

The Kazakhstan Airlines Ilyushin Il-76TD was flying from Shymkent to Delhi. There were 27 passengers on board, including tourists, and 10 crew members. The air traffic controller instructed the crew to descend to FL150 (about 4,570 meters) and informed about Boeing 747 flying towards, 300 meters below. It was an airplane of Saudi Arabian Airlines just departed from Delhi heading to Saudi Arabia. There were 312 people on board, including 23 crew members. Boeing crew received an instruction to maintain FL140 (about 4260 meters).

Come join Aussie Owen Zupp, airline pilot & award-winning aviation writer, as he flies solo in a light aircraft around Australia in 2010. Enjoy beautiful Australian scenery, especially the famous remote outback/backcountry, & learn a bit about Aussie aviation history. Part 4 (Final) sees Owen return to his starting point, Bundaberg, Queensland. Hope you enjoy. Cheers.

https://youtu.be/ZNNZs9-NPqg?si=O1fyd0jfChQbB8Hx

On August 31, 2018, a Boeing 737-800 of UTair airlines was operating a flight from Moscow (Vnukovo) to Adler (Sochi). The aircraft approached Sochi during the night amidst severe weather conditions: thunderstorms, heavy rain, and gusty winds. Some aircraft were unable to land and had to go around. Boeing initiated its landing approach and descended to 700 meters. However, upon receiving updated weather and visibility information at the airport, pilots decided to wait for more favorable conditions and entered a holding pattern.

Plane involved

While in the holding pattern, the crew received further updates on the weather, which remained unsuitable for landing. After this, the following conversation took place in the cockpit:

Captain: "Shall we play dump and make an approach?"
First Officer: "(so that) we don't have to go around"

After this, the first officer began preparing the aircraft systems for landing. During the approach, when the Boeing was at an altitude of about 260 meters, the "Go around. Wind shear ahead" alarm sounded.

Wind shear is a dangerous weather phenomenon that makes landing very risky. At an altitude of approximately 50 meters, the system signaled an encounter with wind shear. Both times, the crew did not respond to these signals. Only at around 15 meters altitude did the captain initiate a go-around, as the pilots were unable to see the runway due to the rain.

According to the investigation, the decision to go around became stressful for the crew, and they were in a "suboptimal working state." This was evidenced by the difficulties the pilots encountered in engaging the autopilot. Additionally, after its re-engagement, the crew repeatedly changed its modes. Furthermore, the first officer forgot to retract the flaps, although he informed the captain that he had done so.

Sochi Airport

During the climb, the crew expressed their opinion about the meteorological conditions at the airport:

First Officer: "So, damn, trying to land in such crap in Sochi, damn, forget it, damn it?"
Captain: "Fuck it."
First Officer: "Yeah."
Captain: "Absolutely nothing could be seen there."
First Officer: "Yeah."
Captain: "Absolutely, damn it, nothing."

However, despite this dialogue, the crew decided to attempt another landing. As they approached the runway again, the "Go around. Wind shear ahead" alarm sounded once more. Approximately a minute later, the wind shifted, turning from headwind to tailwind. At that moment, the captain switched to manual control and disengaged the autothrottle before it could reduce engine power due to the changed conditions. As a result, the aircraft's speed began to increase, and the rate of descent decreased. Consequently, the Boeing landed 1285 meters beyond the runway threshold, overshooting by 385 meters.

After touchdown, the first officer reported the activation of reverse thrust, although it was actually engaged only 16 seconds later. The crew applied maximum manual braking. Nevertheless, 26 seconds after landing, the aircraft, at a speed of 140 km/h, rolled off the runway, broke through the airport fence, and stopped in the bed of the Mzymta River. Subsequently, a fuel fire occurred, leaking from the damaged left wing fuel tank. The crew conducted passenger evacuation. The fire was soon extinguished by arriving services. Eighteen people were injured onboard as a result of the incident. Additionally, during passenger rescue, an airport employee died of a heart attack. The aircraft sustained serious damage.

Damaged aircraft

The investigation commission identified two main causes of the incident. The first was the repeated disregard by the crew of wind shear warnings, leading to landing at a great distance and at an increased speed.

From the captain's explanation: "The erroneous decision to land was made due to an emotional state: I simply didn't hear the wind shear alarm; my body disregarded it as background noise (during the first approach, it worked so loudly and for so long that it interfered with my work and, thus, turned from a danger warning system into unwanted noise)."

The second reason was the landing on a runway whose average coefficient of friction was calculated to be less than 0.3 due to water, which did not allow landing according to the current regulations.

Among the contributing factors were: the use of autopilot and autothrottle in wind shear conditions, late deployment of reverse thrust, inadequate preparation and psychoemotional state of the crew members, insufficient preventive work in the airline following previous cases of crews' untimely response to wind shear warnings, as well as non-compliance by the airport service with requirements for checking the condition of the runway after precipitation.

I've read lots of articles that mention how effective NVAF GCI was at guiding pilots to their targets but I've never come across anything that actually describes how it was done. I've also heard it described as more "authoritarian" than the "Teaball" system the USAF developed as a response but never any details as to how exactly the two GCI systems differed.