The potential for Aircraft failure, fatigue, and structural failure is something that anyone in the aircraft industry is familiar with. Aircraft undergo rigorous testing before they can be considered safe and certified for flight to ensure that they can operate how they need to.
According to Boeing, equipment failure, which includes structural failures, only accounts for about 20% of accidents in today’s aircraft. We’ve come a long way from early flying machines, where nearly 80% of accidents were related to some kind of mechanical or structural failure.
Still, since safety is at stake, metal fatigue and failure is something that must be considered with every maintenance inspection. Let’s take a look at fatigue and metal failure.
According to the International Air Transport Association (IATA) data, there were only 53 accidents and 240 fatalities in the last year 2019. There were 4.54 billion people have traveled through planes and there were 46.8 million trips.
Old days, Aircrafts were made out of metals and there were more crashes were occurred. Among of various reasons, FATIGUE FAILURES were very important and dangerous factor. Because it won’t show any foreshadows.
Aircraft failures due to Fatigue
|1919||Italy||Caproni Ca.48||Vibrations of the wing and suddenly broke|
|1930||England||Junker F.13||Due to turbulences, plan tail was broken|
|1953||Mexico||Douglas DC-6||Due to turbulence, main structure was failed|
|1954||Mediterranean Sea||BOAC Flight 781||Roof fail due to fatigue|
|1954||Mediterranean Sea||South African Airways Flight 201||Due to fatigue decompression happened|
|1963||USA||B52 Stratofortress||Broken vertical stabilizer|
|1964||USA||NRB 57 Canberra||both wings were failed|
|1964||USA||B52 Stratofortress||Broken vertical stabilizer and landed|
|1965||USA||Handley page hasting||Elevator became uncontrollable due to failure of two bolts|
|1966||USA||BAC One Eleven 203AE||Due to turbulences, Horizontal and vertical stabilizers were broken|
|1976||Argentina||Hawker Siddeley 748||Starboard wing was failed|
|1977||Zambia||Boeing 707||Broken right horizontal stabilizer|
|1978||Norway||Sikorsky S-16||Rotor blade was loosened from the knuckle joint due to fatigue|
|1985||Japan||Boeing 747 SR||Tail fin was blown out|
|1988||USA||Boeing 737||Roof top was blown off|
|1992||Netherlands||Boeing 747||One engine was ripped and one was broken. Crashed on landing|
|1997||Norway||Euro copter AS 332L1 Super Puma||Due to fatigue failure in the Spline, power transmission shaft was broken and crashed in to the sea|
|2002||Taiwan||Boeing 747-200||Tail section was broken off and air craft was disintegrated in to several parts|
|2005||USA||Grumman Turbo-Mallard G73T||Wings were broken in flight due to fatigue|
The maximum load that can bear the metal is called tensile strength. But fatigue failure happens less than it. If there is Fluctuating force or cyclic loads fatigue failure can be initiated. With the increment of the force, the number of cycles needed to fail will reduce as follows. If the force is lower than the critical level, there won’t be initiate fatigue failures.
Factors that trigger fatigue.
- Temperature (Inversely proportional)
- Magnitude (amplitude) of the applied force
- Number of cycles or frequency of the force fluctuating
Then how these failures identify be observing the broken parts. That’s called Failure analysis. There will be a smooth start, curved lines (Beach marks) with having gaps, and finally a rough surface. Using those beach marks, the force and the frequency that the sample faced can be calculated.
Actual images of the crack surface of the fatigue failures.
Fatigue Failure Aircraft Failure Analysis