WPR15LA253 · Beech C90

During the initial preflight checks of the jet before departure, the first officer (FO) observed the BRAKE ACCU light illuminated, which indicated insufficient hydraulic pressure to the parking brake. The FO then referenced the quick reference handbook (QRH) Abnormal Checklist, which noted "Residual pressure normally allows six brake applications to the first detent. No further action required." When the pilot-in-command (PIC) entered the flight deck, the FO advised him of the anomaly and what the QRH Abnormal Checklist stated, which the PIC confirmed. After the ground crewman removed the wheel chocks, the airplane began to roll down a slight incline. Attempts by both flight crewmembers to stop the airplane by applying toes brakes and pulling the emergency brake handle were unsuccessful. The airplane continued to roll down the incline before colliding with a parked twin-engine turboprop airplane, causing substantial damage to the turboprop airplane and minor damage to the jet.

The investigation revealed that the jet's flight crew had used the inappropriate checklist for the BRAKE ACCU light anomaly. Rather than using the QRH Abnormal Checklist, the flight crew should have been familiar with, based on their training, and referenced the Normal Operations Pre-Flight Interior Inspection checklist. This checklist specifically states that, if the BRAKE ACCU light is on, the accumulator should be charged using the standby pump or by monitoring engine #2 and the chocks should not be removed until the light is extinguished. The flight crew maintained that they had no recollection during their simulator type-rating training that the QRH Abnormal Checklist was to be used for in-flight anomalies only. However, two simulator instructors employed by the firm that conducted the training for both flight crewmembers stated that all of their instructors are taught to stress that the QRH Abnormal Checklist is to be used only for in-flight anomalies. Had both of the jet's flight crewmembers thoroughly understood the correct checklist to use, the parking brake system, and how to appropriately resolve the BRAKE ACCU light anomaly, this accident would have not occurred.

The investigation also revealed that the jet's parking brake check valve was faulty, which was most likely the reason for the illumination of the BRAKE ACCU light. A design improvement to the valve had been developed about 7 years before the accident, which resulted in a new check valve to replace the previously defective check valve. However, the new check valve was never installed on the accident airplane.

Verbatim NTSB analysis and probable cause from the NTSB dataset