Sepahan Airlines Flight 5915
| Industry | Aviation |
|---|---|
| Headquarters | Tehran , Iran |
Sepahan Airlines Flight 5915 Accident
Sepahan Airlines Flight 5915 was a domestic passenger service operating between Mehrabad International Airport in Tehran, the capital of Iran, and Tabas Airport located in South Khorasan province. On 10 August 2014, the twin turboprop HESA IrAn-140 aircraft assigned to this flight crashed shortly after departing from Mehrabad International Airport. The plane impacted a nearby boulevard close to the Azadi Stadium in Tehran. Among the 48 individuals on board—comprising 42 passengers and 6 crew members—40 fatalities were reported, while 8 survived.
The investigation conducted by Iran's Civil Aviation Organization identified a mechanical failure as the primary cause of the accident. Shortly after takeoff, one engine malfunctioned, and improper handling of this emergency by the flight crew resulted in a rapid loss of altitude, culminating in the crash. Additionally, investigators highlighted that ambiguities within the Aircraft Flight Manual (AFM) contributed to the crew's overestimation of the aircraft's maximum takeoff weight, which further exacerbated the situation.
Accident
Sepahan Airlines Flight 5915 was planned to operate a route from Tehran, the capital of Iran, to Tabas, a key city in South Khorasan province. Onboard were 42 passengers along with 6 crew members, including two off-duty Sepahan Airlines mechanics traveling as passengers. The flight departed from Mehrabad International Airport in Tehran, taking off from Runway 29L at 09:22 a.m. local time.
A malfunction occurred in the right engine just two seconds before the aircraft was due to lift off. The flight crew promptly declared an emergency and requested immediate clearance to return to the airport, initiating a left turn. While the co-pilot continuously communicated the engine failure to air traffic control, the plane stalled and began to descend sharply toward the right side. Subsequently, the right wing struck trees and then the ground.
The airplane crashed into a residential area near Mina Glass Boulevard in western Tehran, breaking apart upon impact with trees. The collision caused fuel lines to rupture, igniting a fire that engulfed the aircraft. Both engines and wings separated from the fuselage. The wreckage then collided with a concrete barrier alongside the boulevard and exploded. The tail section was thrown onto the boulevard itself.
Emergency response teams at the airport were alerted immediately; however, due to communication breakdowns and poor coordination, they were delayed in reaching the crash location. Rescuers managed to extract at least 11 survivors from the debris, all of whom were seriously injured and transported to nearby hospitals. Unfortunately, three of these survivors later died from their injuries, reducing the number of survivors to eight. In total, 40 passengers and crew members lost their lives in this accident. Additionally, at least three individuals on the ground sustained burn injuries and required hospital treatment.
Aircraft
The aircraft involved was an Antonov An-140 manufactured in 2008 with serial number 90–05 and assembled domestically in Isfahan. It bore the registration EP-GPA under Sepahan Airlines. At the time of the crash, it had logged 1,370 flight hours and completed 1,058 flight cycles. Powered by two engines, its left engine was produced in 2007 with 1,311 cycles recorded, while its right engine dated back to 2004 with 1,329 cycles.
The Antonov An-140 model—on which Iran’s HESA IrAn-140 is based—is a relatively modern design. Knock-down kits for domestic assembly within Iran were still being delivered as recently as 2007.
Passengers and crew
The flight carried 42 passengers alongside a team of six crew members. Among the passengers, 36 were adults and six were minors. Tragically, 34 passengers along with all six crew perished in the incident.
The pilot in command, aged 63, had amassed over 9,400 hours of flight experience, including approximately 2,000 hours operating the Antonov An-140. He had been certified to fly this aircraft type since May 2014. Medical evaluations confirmed he had no health restrictions and was not suffering from fatigue at the time of the accident.
The co-pilot, a 32-year-old captain, possessed a total flying experience of 572 hours, with 400 hours logged on the Antonov An-140. He commenced his captain transition training for this aircraft in September 2005. Documentation verified that he was adequately rested during the flight.
Right engine failure
Eyewitness accounts from survivors indicated that the aircraft’s right engine experienced a failure during takeoff. Review of the aircraft’s logbook showed multiple recorded faults and malfunctions related to the right engine. In April 2014 alone, at least two engine failures were documented. Specifically, on April 23 and April 24, while flying to Bandar Abbas, the right engine ceased functioning during cruise. On April 28, the engine failure warning light briefly illuminated. Additionally, on April 29 during routine inspections, ground personnel identified corrosion on a compressor blade of the left engine.
A mere three days prior to the crash, on August 7 during a flight from Tabriz to Isfahan, significant vibrations were detected in the right engine. The flight data recorder captured this shaking and triggered an alarm. A sensor replacement was performed to address this issue; however, post-replacement data showed inconsistent vibration levels between the right and left engines, which investigators considered unreliable. It was concluded that the sensor replacement had been improperly installed by maintenance crews.
Further analysis determined that the root cause of the right engine failure was linked to a disruption in the aircraft’s fuel delivery system. Specifically, fuel supply lines feeding the combustion chamber were interrupted due to a malfunction in the electronic engine control unit known as SAY-2000. This system failed to operate correctly, causing a delay of approximately 17 seconds before feathering of the propeller commenced. Once activated after this delay, the feather pump engaged and the system recognized the failing right engine to initiate propeller feathering.
Investigators highlighted that flight crew identified the right engine failure within about five seconds after its onset, whereas official warning signals were only activated after a delay of roughly fourteen seconds.
Previous studies concerning the SAY-2000 system on the Antonov An-140 revealed software modifications had been implemented following earlier incidents where this system contributed to excessive engine failures beyond acceptable limits. Despite these updates, failure rates remained above satisfactory thresholds, indicating that software adjustments did not sufficiently mitigate the problem.
Additional discoveries
The inquiry uncovered that the aircraft had been operated beyond its weight limits. This issue stemmed from ambiguities within the Aircraft Flight Manual (AFM), which investigators found to be unclear and misleading. It is believed that the pilot was misled by the AFM during the calculation of the maximum takeoff weight, resulting in an overestimation by approximately 190 kg. Furthermore, the fuel load exceeded requirements by 500 kg. The investigation also noted that the aircraft did not achieve the designated takeoff speed; rather than lifting off at the prescribed 224 km/h, the crew chose to initiate takeoff at 219 km/h.[1]
Following the failure of the right engine, standard procedure required the pilots to activate the right engine feather button to feather that propeller. The pilots acknowledged the malfunction within 5 seconds of its occurrence, and 9 seconds later, the pilot flying reiterated the engine failure. Despite this, neither pilot engaged the right propeller feather control. At 14 seconds post-failure, the co-pilot communicated the engine issue to Air Traffic Control. By this point, airspeed had peaked at 224 km/h before declining. The aircraft then entered a stall condition. Due to insufficient altitude, recovery was impossible, leading to a crash.[1]
Conclusive report
Subsequent analysis identified several contributing factors to the crash. The aircraft was overloaded by 2,666 kilograms (5,878 lb), and improper trim settings were applied for takeoff. Specifically, the stabilizer should have been trimmed upward between zero and six degrees, but during this flight it was set two degrees downward. Additionally, the rudder trim was off-center. Flaps intended to be deployed at 15 degrees were only set at ten degrees. During the takeoff roll, a fault in the electronic fuel delivery system caused power loss in the right engine. Despite not reaching rotation speed yet, two seconds after this failure, the captain initiated liftoff. Shortly after detecting engine failure, the crew delayed feathering the propeller. The aircraft’s airspeed declined as it climbed to a maximum altitude of 40 metres (130 ft), then descended into an aerodynamic stall. When propeller feathering finally occurred 17 seconds after failure onset, recovery was no longer feasible, resulting in impact with a highway located 1.6 kilometres (0.99 mi; 0.86 nmi) beyond the runway’s end. The final investigation report states:[1]
References
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