The European Union Aviation Safety Agency has issued a notice of proposed amendment (NPA) that would update large airplane certification (CS-25) rules to provide a means for ensuring that no tire is below its minimum serviceable inflation pressure during operation. Compliance can be achieved either by requiring operators to perform tire pressure checks at suitable time intervals or by installing a tire pressure monitoring system.
“Incorrect tire pressure, and, in particular, under-inflation, is a contributing factor to tire- and wheel-failure-related accidents or incidents of large airplanes,” EASA said. “Onboard tire pressure monitoring systems and ground tire pressure indication systems have been developed, certified, and are available on various types of large airplanes.” However, despite recommendations from safety agencies, including the NTSB, such systems are not mandated by EASA or FAA regulations.
Among examples of accidents related to under-inflated tires cited in the NPA, was the fatal rejected takeoff crash of Learjet 60 on Sept. 19, 2008, in Columbia, South Carolina. The NTSB determined that tire pressures had not been checked for approximately three weeks and that they had experienced a 2 percent loss of pressure per day. At the time of the accident, the pressures of all four main gear tires were approximately 140 psi instead of the recommended 219 psi.
The under-inflation resulted in the failure of all four tires. In addition, tire fragments compromised some elements of the aircraft’s hydraulic system. The NTSB’s investigation also identified that there was a significant inconsistency in the operating community regarding the pilot’s role in ensuring correct tire pressures before takeoff.
“Visual inspections of high-pressure tires, such as those of the airplane involved in the accident, will not help to detect an incorrectly inflated tire,” the Safety Board concluded. Comments on the NPA are due June 6.