Investigation Of The Causes Of The Emergency Landing Of The SE-EEU Aircraft

This report examines the cause of the emergency landing of the SE-EEU aircraft, which occurred on July 23, 2001, at a height of 2000 meters south of Sweden in the Linköping area due to the failure of the propeller blade.

Description of the incident

The plane was flying from Gothenburg to Norrköping, which suddenly heard the pilot a harsh sound on the right side of the engine, resulting in a diminution in motor power and severe vibration in the aircraft body. Following a reduction in thrust force on the right side of the plane and its yaw into one side, pilot forced to reduce the power of the left engine in order to balance forces. Next immediately communicate with air traffic control and report the situation, eventually, they decided to land at the nearest airport (SAAB Airport).

Fortunately, there were no fatalities in this event. The cause of the incidentWhich follows, the accident investigation team is formed instantly and collects information and investigates the cause of the incident. The propeller was made of a twin- blade aluminum type, which through the bronze cylinder bushing bearing is connected to the steel hub. One of the two blades nearby the 10 cm hub was divided from the propeller that caused to deformation and damage in the nose cone of the aircraft. In addition, the huge vibration caused the engine bracket to break and the engine moved forward, resulting in destruction to the cowling and the aileron. In order to carry out the final experiments, the rest of the broken blade, along with the other intact blade, was transferred by Materialteknik team to the Linköping lab for the final analysis and comparison.

• Defeat occurred due to fatigue cracks in the (A) section.
• The fatigue cracks emanated from an irregular torsion groove at a depth of 0. 2 mm.
• These irregular torsion valves may have been caused by inaccuracy during production. -Several porous points are visible near the fracture spot.
• All mechanical properties of the blade were tested according to the manufacturer's report.

To conclusion, all Materialteknik team metallurgical examinations have confirmed that the fracture was created through a fatigue crack that started in a groove in an edge with the 10cm distance of end root (area “A”). It is along with a manufacturing defect in the production stage that results in have been created this crack. A brief description of fatigue cracking and the proposed solution.

The phenomenon of failure and material fatigue occurs when the material is subjected to repeated or oscillating stress causing a sudden failure of the parts. In general, failures that occur under dynamic load conditions are called fatigue failures. The main reason for the risk of failure and material fatigue is that it occurs without prior knowledge and visibility. Fatigue is a breakdown with a crisp appearance, without any gross deformation in failure.

Usually, fatigue failure is detected from the appearance of the surface of the defect, which is formed from a region always caused by abrasion with crack propagation in the section and a rugged area formed in the piece when softly broken when the load is not tolerated. Another characteristic of the failure and material fatigue is that usually failure occurs at the point of stress concentration, such as a sharp corner or groove. Since this phenomenon is visible on the surface of the material, it can be detected by frequent and regular inspections of defective components. Also, the use of the material manual which provided by the manufacturer to determine the lifetime and number of permitted cycles can be used. And it was replaced before it broke. In addition, such as this case if the crack formed in depth of material it could use ultrasonic inspection method to detect cracking can be useful.