What happened
On August 6, 2020, an IndiGo Airbus A321 (registration VT-IUD) was performing a scheduled flight from Chennai to Delhi. During the landing phase at Delhi Airport, the aircraft encountered challenging meteorological conditions, including gusty winds up to 30 knots and a trend of thunderstorms.
As the aircraft descended below 90 feet, it experienced a rapid reduction in the longitudinal headwind component. This loss of wind caused a decrease in airspeed and lift, leading to an increased rate of descent. Although the crew attempted to manage the descent, the aircraft performed a flare at only 30 feet with a high descent rate of 880 feet per minute and a negative pitch angle. This resulted in a severe hard landing with a vertical acceleration of 3.137 G. The impact caused the aircraft to bounce approximately 4 feet into the air before a second touchdown occurred with a lower vertical acceleration of 2.41 G. There were no injuries to the 129 passengers or the six crew members on board.
The investigation
AAIB India investigators examined the flight data recorder (DFDR) and cockpit voice recorder (CVR) to reconstruct the flight path. The investigation focused on the aircraft's aerodynamic response to the changing wind conditions and the crew's manual inputs. The analysis revealed that the aircraft's pitch dynamics were influenced by ground effect at low altitudes, which hindered the effectiveness of the pilot's pitch-up commands.
Technical inspections following the incident involved coordination with Airbus and engine manufacturers. Due to the high-G impact, inspections were conducted on the landing gear and engines. A borescope inspection of the right-hand engine revealed rubbing marks, leading to its removal for further examination. The investigation also noted that while the aircraft's automated systems did not trigger a hard landing warning, the automated load reports confirmed the high vertical acceleration.
Findings
- The primary cause of the incident was an inadequate flare maneuver, performed at a height of 30 feet while the aircraft was experiencing a high rate of descent and a negative pitch angle.
- A lack of situational awareness by both the pilot in command and the co-pilot contributed to the event.
- Adverse weather conditions, specifically the sudden loss of headwind, acted as a contributing factor.
- The co-pilot, who was performing a supervisory landing, had limited experience on the A321 type (approximately 10 hours) and struggled to assess the situation in the gusty conditions.
- The crew utilized plain language for communication during the critical phase of flight, which deviated from the operator's established procedures.