Aeroflot Flight 37577

The aircraft approached Sovetsky at dusk. After receiving the actual weather for 16:50 (14:50 MSK), and clearance from the air traffic controller, the pilots began descending at 17:16. The commander decided that the copilot would fly the aircraft during this phase, contrary to the training program for An-24 flight crews. The crew also did not immediately activate the anti-icing system. It was later turned on before the outer marker, but only after the "Icing" warning had activated three times. At 17:24, the crew reached the transition level (1,200 meters) and set the altimeters to the airport level pressure, reporting this to the controller. They then cross-checked the altimeters and continued descending until reaching 500 meters, 17 kilometers from the runway. The controller indicated that the approach would be conducted using the ILS on a heading of 304°, but in violation of procedures, did not provide updated weather data, or the location and markings of the runway.

The landing gear was deployed at 17:25:10 at an indicated airspeed of 310–315 km/h, and the flaps were first set to 15° at 285 km/h, and then to 30° (landing configuration) at 240 km/h. The radio altimeter's decision height was set to 62 meters. At 17:26:40, the commander reported entering the glide slope at 500 meters, 10 kilometers from the runway threshold, and began descending according to the approach pattern.

However, 6 km (3.7 mi) from Sovetsky at 250 m (820 ft), the vertical speed increased to 5 m/s, but the crew did not notice this as they were correcting a lateral deviation. As a result, the aircraft descended below the glide slope, passing the outer marker at 60–90 meters below the required altitude (120–150 meters instead of 210). Realizing this, the pilots gradually reduced the vertical speed to zero and maintained level flight for about a kilometer until they rejoined the glide slope, then continued descending. At 130 meters, the flight engineer should have called "Assessment," but he did not, nor did he announce "Decision height" at the appropriate altitude (100 meters). The commander also did not share his assessment with the crew at the decision height. The flight engineer-instructor in the cockpit did not intervene to correct the errors made by the crew under evaluation.

When the runway threshold was 300 meters away, the controller transmitted updated weather data, which was below the minimum required for an An-24, necessitating a go-around. However, the crew did not execute it. Instead, at 75 meters, the vertical speed increased to 6 m/s, creating an emergency situation. After passing the decision height of 62 meters, the radio altimeter's warning signal activated, but the descent continued. Only at 35 meters did the pilots see that the aircraft was heading toward a forest, prompting them to abruptly pull back on the control yokes, raising the nose and causing the aircraft to start climbing, which resulted in nearly 1.5 times the normal load factor. Additionally, someone advanced the engines to takeoff power without command. However, the crew did not fully arrest the descent in time.^[2]

At a distance of 180 meters from the outer marker, the An-24 struck trees with its right wing. The impact destroyed the wing and shut down the right engine, causing the right propeller to feather automatically. However, the left engine had already begun spooling up to takeoff power (the collision occurred a few seconds after advancing the engines), creating asymmetric thrust. Combined with the asymmetric lift from the damaged right wing, this caused the aircraft to roll to the right, reaching a bank angle of 27°. The crew attempted to counter the roll with maximum rudder and aileron deflection, initially reducing the bank to 12°. However, a few seconds later, due to stall on the damaged right wing, the right bank rapidly increased again (16° per second). At 17:28:47, the An-24, with an almost 90° right bank, crashed into a highway embankment, crossed it, and struck an earthen berm, where it disintegrated and caught fire. Rescue services found 8 severely injured passengers at the crash site. The remaining 27 passengers and all 5 crew members perished.^[2]

The crash of the An-24 aircraft occurred due to a combination of the following factors:

• insufficient preparation of the crew for landing under the given conditions and unsatisfactory crew coordination, including the distribution of functions between the commander and the copilot, which led to a violation of the approach pattern and premature descent below the decision height in difficult weather conditions without visual reference to ground landmarks.
• violation by the crew of the minimum landing altitude established for this type of aircraft during an ILS approach, accompanied by rapid descent to establish visual contact with ground landmarks at extremely low altitudes.
• repeated disregard by the commander and copilot of the need to initiate a go-around upon reaching the decision height, receiving information from the controller about deteriorating vertical visibility, and activation of the radio altimeter's decision height warning at 62 meters, which prevented the crew from correcting the errors made during the approach.
• failure of the inspecting flight engineer-instructor to fulfill his duties in monitoring the actions of the evaluated crew.