48
posted ago by Revodude ago by Revodude +48 / -0

From a reliable friend.

Bottom line: Minimum Equipment List item that had a problem, but the maintenance was repeatedly deferred. I would not have flown it with a MEL problem. And the FADEC should freeze at the current setting instead of idle.

From a retire aviation mechanic neighbor FYI

Flight: AI-171 | Aircraft: Boeing 787-8 | Date: June 15, 2025 | Route: Ahmedabad (VAAH) → London Heathrow (EGLL) Crash Site: ~1.2 km from VAAH Runway 23, post-V1 and rotation

  1. Primary Cause – Electrical Power Transfer Interruption (PTI) During Rotation • During transition from ground to airborne electrical configuration, the aircraft experienced a cascading dual-engine FADEC (Full Authority Digital Engine Control) failure. • Root cause: Uncommanded bus transfer failure due to arcing in the main power relay box (PRB-A), traced to water ingress during pre-flight GPU disconnection in heavy rain. • This led to loss of electronic engine control at rotation, resulting in both GEnx engines rolling back to ground idle within 4–5 seconds.

  2. Flight Data Record Timeline • +0:11 sec: Nose gear lifts off. • +0:13 sec: Sudden engine rollback begins. Thrust reduces from 92% N1 to <27% within 3 seconds.

• +0:16 sec: Master caution + ENG FAIL L/R warnings. FO calls, “Both engines dropping!”

• +0:20 sec: Autopilot and flight control reverts to Direct Mode. Pitch up attitude peaks at 18°.

• +0:25 sec: Aircraft stalls at 186 ft AGL. • +0:30 sec: Full aerodynamic stall; nose drops rapidly. • +0:38 sec: Ground impact at 54° nose-down attitude, 174 knots.

Contributing Factors • Environmental Conditions: • Torrential rain during pushback. • Moisture intrusion into PRB-A connector (P/N: HLN8471) — a known corrosion-risk component. • Latent Maintenance Issue: • Power transfer relay unit showed signs of thermal damage in a previous MEL deferral 2 weeks prior. • No replacement had been conducted; aircraft was cleared under repetitive deferral.

• Boeing 787 has no physical engine control backup (i.e., no direct mechanical linkage in FADEC loss scenario). • Loss of power supply to both EEC channels resulted in engine “freeze” at ground idle instead of flameout. • Flight Crew Response: • Attempted engine relight sequence not completed before stall onset. • Emerg