Raytheon Aircraft Company HAWKER N694ES incident near Denver, Colorado

Probable cause

The failure of the main landing gear tire, which resulted in separation of the servo block and subsequent total loss of all hydraulic system pressure and prevented the landing gear from extending before landing.

NTSB analysis

The commercial pilot and the airline transport pilot were operating a business flight. According to the operator, the pilots reported that, during the takeoff roll, they felt and heard a vibration emanating from the airframe. They continued the takeoff and retracted the landing gear. Air traffic control tower personnel radioed the pilots and informed them that they had momentarily observed white smoke coming from the airplane. Shortly after, the hydraulic low pressure lights illuminated. The pilots returned to the airport but were unable to extend the landing gear normally. They subsequently attempted to extend the landing gear using the alternate gear extension procedures without success. Due to the hydraulic system malfunction, the pilots diverted to an airport with a longer runway and landed the airplane with the flaps and gear retracted.

An examination of the airplane revealed that the No. 2 (inboard) tire on the left main landing gear assembly had ruptured, which resulted in the servo block separating from its actuator. The separation of the servo block resulted in the loss of both the normal and emergency hydraulic system pressures.

There were no obvious signatures of cuts or foreign object damage to the tire's external layer, and no manufacturing anomalies of the tire were noted. An examination of the tire fragments revealed wrinkles on the inner liner of the tire shoulder area consistent with overdeflection. The tire could have become overdeflected if it was operated below the recommended pressure and/or if it was overloaded. According to the operator, tire pressures were checked before flight, but the pressures were not recorded; therefore, it could not be determined whether the incident tire was consistently operated at the recommended pressure. The operator was not aware of any overloaded condition of the airplane.

Due to similar incidents, the airplane manufacturer had previously issued a service bulletin (SB), which recommended the installation of a landing gear jack that had improved servo block mounting hardware that would prevent separation of the servo block in the event of a tire failure. The SB recommended installing the landing gear jack with the improved hardware at the next landing gear jack replacement or overhaul; however, the airplane had not required a landing gear jack overhaul or replacement and, therefore, it did not have the improved servo block mounting hardware installed. No similar failures involving the improved mounting hardware have been reported.

Text from the NTSB. Open the NTSB docket for CEN15IA014 for the full record.