Metal fatigue caused 1,885 serious accidents between 1927-1981, claiming 2,240 lives – with 100+ incidents still occurring annually.
From the Archives of Aviation Safety
It’s one of the great miracles of modern life: stepping onto a jet, soaring above the clouds, and landing safely hundreds or thousands of miles away. We trust the steel and aluminum that hold us aloft. But there’s a sneaky, relentless enemy lurking inside every aircraft part: metal fatigue.
A comprehensive worldwide survey recently dug into the cold, hard facts of this invisible foe, revealing just how serious metal fatigue is to flight safety.
The Secret Life of a Crack
What is fatigue? It’s simply the effect of repeated use. Every flight—every takeoff, bump of turbulence, and firm landing—puts stress on the metal components. Over years and thousands of hours, tiny, almost invisible cracks can start to grow, even if the part never sees a single overwhelming load.
If this crack develops in a part critical for flying safely, the result is a serious accident. In fact, between 1927 and 1981, fatigue fracture was a factor in an astonishing 1,885 serious aircraft accidents globally, claiming the lives of 2,240 people.
Critical Safety Issue:
Metal fatigue caused 1,885 serious aircraft accidents between 1927-1981, resulting in 2,240 fatalities - a hidden threat that continues today.
Where Airplanes Are Most Vulnerable
Which parts are most likely to get “tired”? The survey offers a clear picture:
- Fasteners: Bolts, studs, and screws are the number one initiation site for fatigue cracks
- Holes and Notches: Any fastener hole or sharp design feature like fillets or radii
- High-Stress Areas: Components experiencing repeated loading cycles
The data shows that fasteners are responsible for 24% of fatigue failures in fixed-wing aircraft and 26% in rotary-wing aircraft (helicopters).
Most Vulnerable Areas:
Fasteners (24-26% of cases), holes, and high-stress design features are the primary sites where fatigue cracks begin.
The Recurring Nightmare
Perhaps the most unsettling finding is the sheer number of repeated accidents due to the exact same problem on the same model of aircraft.
- Cessna 182: 21 accidents due to nose gear fork failure
- Bell 47 Helicopter: 42 accidents over 19 years due to failed tail rotor blade
These repeated incidents highlight why designers and maintenance crews must constantly chase and solve these ongoing fatigue issues.
Recurring Failures:
Same aircraft models experiencing identical fatigue failures repeatedly - Cessna 182 (21 incidents) and Bell 47 (42 incidents).
The Tiny Culprits
Where does the fatal crack usually begin? It’s almost always at a spot that experiences high stress:
Fasteners: The bolt, stud, or screw is the number one initiation site for both fixed-wing (24% of cases) and rotary-wing aircraft (26% of cases).
Holes and Notches: Any fastener hole or a sharp design feature like a fillet or radius is a high-risk area where a crack can start growing.
Crack Initiation Points:
Fatigue cracks almost always begin at fasteners (24-26%) and stress concentration points like holes and sharp design features.
The Continuous Battle for Safety
The researchers ultimately concluded that even with modern engineering, serious fatigue-related accidents are still occurring at a rate of about 100 per year.
But don’t panic! This research isn’t meant to ground us; it’s the foundation of modern aviation safety. These findings are what drive aircraft inspectors, maintenance engineers, and airworthiness directives to hunt down and fix these known problems—often requiring airlines to replace parts or inspect them more frequently—long before that invisible crack can grow into a disaster.
When you fly, rest assured that the battle against metal fatigue is constant, detailed, and ongoing. The engineers and safety experts are always watching.
Ongoing Safety Battle:
Despite modern engineering, ~100 fatigue-related accidents occur annually, driving continuous inspection and maintenance protocols.