Aviation Maintenance and Safety

Overview

• Importance of aircraft maintenance for safety and operational efficiency.
• Maintenance workers play a crucial role, often overlooked in favor of pilots.

Aircraft Checks

• A Check: Brief walk-around inspection performed every time the plane stops.
• B and C Checks: More intensive checks performed at set intervals.
• C Check: Detailed inspection requiring hundreds of man-hours, ensuring all components are functioning correctly.

Complexity of Modern Aircraft

• A Boeing 737 has over 360,000 parts compared to the Wright brothers' first plane with 1,500 parts.
• Importance of ensuring every component is functioning; even a missing screw can jeopardize safety.

Case Studies in Maintenance Failures

Alaska Airlines Flight 261 (Jan 31, 2000)

• Incident: Crash due to a failure in the horizontal stabilizer's control mechanism (Jack screw).
• Investigation Findings:
  • Jack screw separated from the nut due to lack of lubrication.
  • Mechanics under pressure to cut corners leading to falsified maintenance records.
  • Inspection cycles were stretched to save costs.

JAL Flight 123 (Aug 13, 1985)

• Incident: Deadliest single plane disaster in history due to a faulty repair on the tail.
• Investigation Findings:
  • A previous repair had not been performed correctly, leading to a faulty bulkhead.
  • Pressure from the cabin caused the faulty repair to fail after numerous flights.

Atlantic Southeast Airlines Flight 529 (Aug 21, 1995)

• Incident: Propeller blade failure due to maintenance oversight.
• Investigation Findings:
  • A cork used to maintain balance in the propeller caused corrosion.
  • Misguided maintenance practices led to undetected cracks in the propeller blade.

Swiss Air Flight 111 (Sep 2, 1998)

• Incident: Crash caused by fire originating from a faulty entertainment system installation.
• Investigation Findings:
  • Flammable insulation material allowed fire to spread quickly.
  • The entertainment system was not part of the original design, compromising safety.

United Flight 585 & U.S. Air Flight 427 (1991 & 1994)

• Incident: Rudder control failures in both flights caused them to crash.
• Investigation Findings:
  • Power control unit (PCU) showed no failures initially.
  • A thermal shock test revealed a small hydraulic valve could jam, leading to control loss.

Maintenance Practices

• Inspections are critical; however, some problems can go undetected.
• Maintenance teams at airlines like Southwest Airlines perform extensive checks nightly.
• Tools Used: Borescopes for internal inspections of engine components.

Conclusion

• Despite past disasters, the aviation industry has implemented stronger maintenance protocols.
• Continuous learning and improvements in maintenance practices are vital for ensuring passenger safety.