Nivar

Nivar

Analysis of Weather-Related Aviation Accidents in Iran Using ASN Information and ERA5 Reanalysis Data

Document Type : Original Article

Authors
1 Associate Professor, Research Institute of Meteorology and Atmospheric Science, Tehran, Iran
2 Assistant professor
Abstract
Adverse weather conditions are recognized as one of the most critical contributing factors in aviation accidents, particularly during the takeoff and landing phases. This study investigates the role of various meteorological phenomena in aviation accidents within Iran. To this end, six weather-related aviation accidents and one serious incident were systematically analyzed, each directly associated with specific atmospheric hazards including airframe icing, lightning strikes, thunderstorms, low visibility, and crosswind conditions. Accident and incident records were obtained from the Aviation Safety Network (ASN) and complemented by multiple meteorological data sources, including ERA5 reanalysis datasets, METAR aviation weather reports, satellite imagery, and lightning detection records. This multi-source approach enabled a comprehensive meteorological reconstruction of each event and facilitated a deeper understanding of the contributing weather factors. The analysis of the icing-related accident revealed that ambient temperatures near 0°C, combined with high humidity and the decision to skip de-icing operations, led to surface contamination of the wings. This likely caused aerodynamic performance degradation and a stall during the takeoff phase. The findings align with global simulation-based studies indicating that inadequate de-icing in near-freezing conditions significantly increases the risk of control loss due to ice accumulation on aerodynamic surfaces. One lightning-related accident and one serious incident were also examined. The first resulted in a total aircraft loss with fatalities, while the second, although not fatal, led to temporary failure of essential flight systems including the weather radar, Ground Proximity Warning System (GPWS), and transponder. In both cases, the CAPE×P index, which reflects the combined effects of convective energy and moisture availability, indicated elevated values, confirming the presence of highly unstable atmospheric conditions conducive to lightning activity. These cases underscore the broad operational risks posed by lightning, including electronic failures, structural damage, and degraded situational awareness—particularly in mid-flight or during descent. A thunderstorm-related accident involving a Tupolev Tu-154 demonstrated the hazards of encountering cumulonimbus (CB) clouds and hail along an active flight route. The aircraft sustained a vertical acceleration of 1.8g and significant physical damage due to hail, forcing the crew to return to the departure airport. CAPE×P values, METAR observations, and satellite imagery validated the existence of deep convective storms and widespread instability across the region at the time. These results are consistent with climatological studies indicating an increase in thunderstorm frequency and severity, particularly in mountainous and semi-arid regions under global warming scenarios. Low visibility was found to be a critical factor in two separate incidents: one during final approach and another during landing. In both cases, visibility dropped below 1,000 meters due to fog or snowfall, and cloud ceilings were low. These meteorological conditions severely impacted the pilots' ability to maintain visual contact with the runway, complicating decision-making in the final stages of flight. ERA5 data confirmed saturated atmospheric moisture and overcast conditions, while METAR reports documented persistent fog and low temperatures. Such scenarios highlight the importance of accurate visibility forecasting and the need for advanced Instrument Landing Systems (ILS) to reduce operational risk under low-visibility conditions. Lastly, the accident attributed to crosswind and tailwind conditions revealed the critical role of wind components, particularly the exceedance of tailwind limitations at the runway level, and the presence of vertical wind shear between 10 and 100 meters altitude. These factors led to unstable final approach dynamics and insufficient deceleration, causing a runway excursion. The presence of wind shear and sudden airspeed changes in the final landing phase underscores the importance of real-time wind monitoring and decision-support systems, especially in airports with short or geographically constrained runways. Overall, this research highlights the complex interactions between meteorological hazards and flight safety in Iran. The findings reinforce the urgent need to improve aviation meteorology infrastructure, including real-time hazard detection systems, pilot training for weather-related contingencies, and the revision of standard operating procedures. Enhanced use of satellite data, reanalysis products like ERA5, and ground-based observations such as METAR can support more informed and timely operational decisions, ultimately contributing to safer skies across the region.
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Volume 49, 130-131 - Serial Number 130
October 2025
Pages 100-121

  • Receive Date 11 April 2025
  • Revise Date 13 July 2025
  • Accept Date 19 July 2025
  • Publish Date 23 September 2025