Investigation Summary
The investigation revealed that the windscreen had been replaced 27 hours prior to the flight. The Shift Maintenance Manager (SMM) used 84 bolts that were 0.026 inches too small in diameter and 6 bolts that were the correct diameter but 0.1 inches too short. Instead of consulting the Illustrated Parts Catalogue (IPC), the SMM visually matched the old bolts with replacements from a bin, failing to notice the slight size difference. Because the BAC One-Eleven windscreen is fitted from the outside, cabin pressure pushed the window against the bolts rather than the airframe; the undersized bolts eventually stripped and failed under pressure.
Final Conclusions
The AAIB concluded the accident was caused by the installation of a windscreen using incorrect bolts. Contributing factors included the SMM's failure to follow established procedures, the lack of a 'Vital Point' designation for windscreen replacement which would have required a second inspection, and inadequate quality monitoring by British Airways management regarding maintenance practices.
Video Analysis
The Pilot Who Was Sucked Out Of His Plane | British Airways Flight 5390 — A detailed look at the incredible survival of Captain Tim Lancaster and the maintenance errors that led to the blowout of BA5390.
Watch on YouTube ↗If playback is blocked, the owner has disabled embedding — use the link above.
Systems & Failure Modes
Windscreen Retention Bolts
90 bolts (7D series) designed to hold the windscreen against internal cabin pressure.
Pressurization System
Maintains a higher pressure inside the cabin than the outside atmosphere; the pressure differential caused the blowout.
Interesting Facts
- 0184 of the 90 windscreen bolts were of a smaller diameter than specified.
- 02The captain survived being exposed to 300+ mph winds and sub-zero temperatures for over 20 minutes.
- 03The maintenance manager used a visual 'best fit' method instead of checking the parts manual.
- 04The BAC One-Eleven windscreen is an 'outward-facing' design, meaning it relies entirely on the bolts to stay attached under pressure.
Safety Actions & Advisories
Maintenance Procedure Review
British Airways reviewed its quality monitoring to ensure Shift Maintenance Managers' work is subject to the same audit standards as other technicians.
Vital Point Designation
The AAIB recommended that safety-critical tasks like windscreen replacement be designated as 'Vital Points' requiring a second signatory.