ANC25LA011

The pilot-in-command (PIC), seated in the left seat, and the second-in-command (SIC), seated in the right seat, reported that, just after starting the airplane’s engines, it began to roll forward uncommanded and unnoticed. The airplane subsequently struck an unoccupied, parked airplane across the ramp, substantially damaging the accident airplane’s right engine firewall and engine mounts. Both pilots reported that the area of the ramp where the airplane was parked was very dark. The PIC stated that, during the engine starts, he had the parking brake set and the toe brakes applied. The SIC reported that the parking brake was set during his preflight checks and just before removing the wheel chocks. Both pilots reported that the airplane remained stationary after the right engine was started. During the start of the left engine, the PIC reported that he did not notice that the airplane was moving until just before the collision. The SIC reported that, after confirming that the airplane was stationary following the right-engine start, he looked down to adjust his shoulder harness and did not notice the airplane was moving before the collision. Postaccident examination and operational testing of the brake system revealed no anomalies that would have precluded normal braking. Maintenance records showed that the accident airplane had undergone an exterior wash and an external and compressor rinse of both engines before the accident flight. After the accident, another pilot flying the same model airplane from the same base reported reduced braking effectiveness during the initial taxi after an exterior and compressor wash. Given the PIC’s report that the parking brake was set and that he was applying the toe brakes when the airplane began moving, the absence of a brake-system fault during postaccident testing, and the subsequent report of reduced braking effectiveness in another company airplane of the same model following a similar wash, the accident airplane likely exhibited temporarily reduced braking effectiveness during the engine start following the exterior wash.

On December 20, 2024, about 2315 Hawaii-Aleutian standard time, a Raytheon Aircraft Company (formerly Beech) C90A airplane, N438CA, was substantially damaged when it was involved in an accident near Honolulu, Hawaii. The pilot-in-command, seated in the left seat, the second-in-command, seated in the right seat, and two medical personnel were uninjured. The airplane was operated as a Title 14 Code of Federal Regulations Part 135 air medical flight. According to the operator, the medical transport flight was en route to a neighboring island to pick up a patient and had two medical personnel from the Kapiolani Medical Center on board. The pilots reported that, just after starting the engines, the airplane began to roll forward uncommanded and subsequently struck an unoccupied, parked company airplane, about 50 to 75 ft across the ramp. As a result, the accident airplane sustained substantial damage to the right engine firewall and engine mounts. Both pilots reported that the ramp area where the airplane was parked was very dark. The PIC reported that he had set the parking brake and was applying the toe brakes during the engine starts. The SIC reported that the parking brake was set during his preflight checks and before the wheel chocks were removed. Both pilots reported that the airplane remained stationary after the right engine was started. The PIC reported that he did not notice that the airplane was moving until just before the collision. The SIC reported that, after confirming that the airplane was stationary following the right-engine start, he looked down to adjust his shoulder harness and did not notice the airplane’s movement before the collision. An examination of the airplane’s brake system by FAA inspectors found an adequate amount of hydraulic fluid in the brake reservoir. During an operational check from both pilot stations, the brakes held under load and released normally, and the parking brake could be set and released normally, with no faults noted. The inspectors observed the operator bleed the brake system using the gravity method; no air was noted in the brake system. The inspectors observed a minor amount of hydraulic fluid on the fuselage beneath the parking brake valve. They found the hydraulic lines tight, and examination of the parking brake valve and lines revealed no faults. According to maintenance records, the accident airplane had undergone an exterior wash and an external and compressor rinse of both engines before the accident flight. After the accident, a different pilot flying another company airplane of the same make and model from the same base reported through the operator’s internal safety reporting program that he experienced moderately reduced braking effectiveness during the initial taxi after an exterior and compressor wash. He reported that he had to apply the brakes aggressively for about one-half mile before normal braking effectiveness returned. During the investigation, the operator revised itsaircraft wet wash procedures to require that wheel and brake assemblies be rinsed with fresh water, dried, and visually inspected for contamination before return to service.