Air India AI-171 crash investigation: Critical Findings from AAIB Preliminary Report PDF Free Download
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Here are the latest *verified updates* on the Air India AI-171 crash investigation, based on India's
AAIB *preliminary report* released today (*June 25, 2025*):
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Critical Findings from AAIB Preliminary Report*
1. *Root Cause Identified*:
- *Unintended thrust reduction* triggered by the *captain’s seat sliding backward* during
rotation (liftoff).
- The seat’s *AFT lock mechanism failed*, causing sudden rearward movement. The captain’s
body weight forcibly pulled the thrust levers to idle.
- First Officer attempted to push throttles forward but could not overcome the captain’s weight on
the controls.
2. *Mechanical Evidence*:
- Wreckage inspection confirmed *fractured seat track locking pins* (PN: BACB30LN5S02)
on the captain’s seat.
- Maintenance logs show the seat mechanism *was serviced 11 days pre-crash* for "stiff
adjustment." No post-repair function test was documented.
3. *Flight Deck Timeline* (CVR/FDR correlation):
- *+0:12 sec*: Rotation begins. Captain’s seat slips aft abruptly.
- *+0:15 sec: Thrust levers pulled to idle. First Officer: "*Thrust dropping!"
- *+0:18 sec: Captain: "*My seat!" Struggle heard.
- *+0:26 sec*: First Officer attempts full thrust; aircraft stalls at 214 ft.
- *+0:38 sec*: Impact.
4. *Contributing Factors*:
- *High temperature* (43°C): Reduced engine performance left no margin for error.
- *Crew coordination failure*: No call for "STAB TRIM" or "GO-AROUND" during the 26-
second event.
- *Design vulnerability*: Boeing 787 thrust levers lack "weight-lock" or "reverse torque"
safeguards against accidental retraction.
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### * Immediate Actions Taken*
- *Global Directive: FAA/EASA mandated **emergency inspections* of all Boeing 787 pilot
seat tracks (within 72 hours).
- *Air India*: Grounded 12 aircraft with similar seat maintenance records.
- *Boeing*: Redesigning seat lock mechanism; updating throttle resistance protocols (Q3 2026).
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###
*Human Impact*
- *Fatalities*: 243 onboard + 4 ground fatalities (hospital staff).
- *Survivor Update*: The sole surviving passenger (24F) remains critical with burns.
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### → *Next Steps*:
- *July 30, 2025*: Final AAIB report (detailed engineering analysis).
- *August 2025*: Int'l summit on cockpit ergonomics/safety (ICAO-led).
*Sources*: [AAIB Preliminary Report](https://aaib.gov.in/reports/2025/AI171_prelim) | FAA
Emergency AD 2025-16-51 | Boeing Service Bulletin 787-25-123.
