The Role of Fuel in the Failure of Polyurethane Tubes

Guy Zehavi, Depot 22, Materials Division, Israeli Air Force, Tel Aviv, Israel (guyzehavi4@gmail.com)
Liel Arazani, Depot 22, Materials Division, Israeli Air Force, Tel Aviv, Israel
Faran Levi, Depot 22, Materials Division, Israeli Air Force, Tel Aviv, Israel
Yalfal Siyum, Depot 22, Materials Division, Israeli Air Force, Tel Aviv, Israel
Inna Kaprovsky, Depot 22, Materials Division, Israeli Air Force, Tel Aviv, Israel
Dr. Moshe Rabaev, Depot 22, Materials Division, Israeli Air Force, Tel Aviv, Israel
Dr. Adva Cohen, Depot 22, Materials Division, Israeli Air Force, Tel Aviv, Israel

Breakage in the aircraft’s fuel tubes caused an emergency landing. In order to determine the source of the failure, the aircraft’s used fuel tubes were compared against identical unused fuel tubes. The used tubes were examined under an electronic microscope, whereupon microscopic cracks were found in the tubes through where the aviation gasoline passed. Furthermore, various chemical analyses revealed the glass transition temperature of the used fuel tubes was noticeably different from the unused tubes. In order to better understand the failure source, a GCMS analysis was performed using a chromatoprobe® sampler. The GCMS analysis showed that the unused fuel tubes contained significantly more additives than the used tubes. Therefore, it was determined that the additives were extracted from the tube by the fuel itself, causing a decrease in the tubes’ flexibility resulting in cracks across the fuel tubes.