WPR19FA230

The pilot’s failure to release the parking brake before attempting to initiate the takeoff, which produced an unexpected retarding force and airplane nose down pitching moment. Also causal was the flight crew’s delayed decision to abort the takeoff, which resulted in a runway excursion. Contributing to the accident was the lack of a NO TAKEOFF annunciation warning that the parking brake was engaged, and lack of a checklist item to ensure the parking brake was fully released immediately before takeoff.

The crew was conducting an on-demand charter flight with eight passengers onboard. As the flight crew taxied the airplane to the departure runway, the copilot called air traffic control using his mobile phone to obtain the departure clearance and release. According to the pilot, while continuing to taxi, he stopped the airplane short of the runway where he performed a rudder bias check (the last item in the taxi checklist) and applied the parking brake without verbalizing the parking brake or rudder bias actions because the copilot was on the phone. After the pilot lined up on the runway and shortly before takeoff, the flight crew discussed and corrected a NO TAKEOFF annunciation for an unsafe trim setting. After the copilot confirmed takeoff power was set, he stated that the airplane was barely moving then said that something was not right, to which the pilot replied the airplane was rolling and to call the airspeeds. About 16 seconds later, the pilot indicated that the airplane was using more runway than he expected then made callouts for takeoff-decision speed and rotation speed. The pilot stated that he pulled the yoke back twice, but the airplane did not lift off. Shortly after, the pilot applied full thrust reversers and maximum braking, then the airplane exited the departure end of the runway, impacted a ditch, and came to rest 1,990 ft beyond the departure end of the runway. The airplane was destroyed by a postcrash fire, and the crew and passengers were not injured. Postaccident examination of the airplane and computed tomography scanning of the parking brake valve revealed it was in the ON position at the time of the accident. Calculations based on airplane performance data and airport surveillance video indicated that the accident airplane was able to accelerate to the speed required for the airplane to rotate and lift off as configured for a normal takeoff. However, the airplane’s performance was substantially degraded during the accident takeoff roll by an unexpected retarding force acting at the wheel/runway interface. Based on the parking brake valve examination and the performance of the airplane during the accident sequence, it is likely that the engaged parking brake produced the unexpected retarding force at the wheel/runway interface, and at a magnitude and direction that adversely affected the airplane’s acceleration and rotation capability during the attempted takeoff. Review of the airplane’s before takeoff and takeoff checklists revealed no explicit item that directed the flight crew to release or check the parking brake. The operator and manufacturer’s taxi checklists direct the flight crew to check brakes but do not specifically refer to the parking brake, and the operator’s flow diagram for that checklist did not point to the parking brake pull knob. Additionally, the position of the parking brake lever was not evaluated as part of the conditions that trigger a NO TAKEOFF annunciation. Review of the CE-560XL parking brake’s certification revealed that the parking brake was designed to prevent the airplane from rolling if one engine is at takeoff power and did not require a cockpit indication if the parking brake was not fully released. These conditions met the parking brake standard at the time of certification. However, the standard was updated in 2002 to require an annunciation if the parking brake was not fully released when takeoff power was applied, and the CE-560XL parking brake was not required to be updated to that standard. The manufacturer did not test the parking brake with both engines at takeoff power and was not required to as part of certification. The head of training where the pilot and copilot received their CE-560XL training stated that no airplane flight manual, checklist, or training curriculum provided a caution or warning that takeoff speeds may be achievable with full or partial pressure applied by the parking brake, and the pilot reported that he expected the airplane not to move with takeoff power applied. Available evidence, including continuous, heavy rubber deposits on the runway consistent with the main landing gear wheel spacing throughout the acceleration segment of the takeoff roll, indicates that it is likely that the pilot did not release the parking brake after setting it to perform the rudder bias check. Because the parking brake pull knob was located on the pilot’s left side and was obstructed from the copilot’s view, it is unlikely the copilot could have seen the pull knob before or during the takeoff. Although the crew was aware of the airplane’s slow acceleration, it was not clear at the time that it was related to an unexpected retarding force or the unsafe condition of the engaged parking brake. Had the parking brake lever position been incorporated into the conditions that trigger a NO TAKEOFF annunciation, as required for airplanes certificated after 2002, the pilot and copilot likely would have identified that the parking brake remained engaged and corrected the unsafe setting before attempting takeoff, just as they did for the unsafe trim setting. Despite the flight crew’s non-adherence to standard operating procedures, a checklist item that directed the pilot to fully release the parking brake before takeoff could have also served as an important redundancy to an annunciation, but none appears in the before takeoff checklist.

The pilot, who was the pilot flying during the accident flight, held a pilot-in-command type rating for the CE-560XL, CE-525S airplanes. The pilot’s most recent proficiency check about 3 months before the accident flight was his initial type rating for the accident make and model. The copilot was the pilot monitoring for the accident flight and qualified as captain by the operator. He held a pilot-in-command type ratings in the CE-560XL, CE-750, and second-in-command privileges for the ERJ-170/190. About a month before the accident flight, the copilot completed his most recent simulator training, which included recurrent training for the CE-560XL. Parking Brake According to the manufacturer’s operating manual, the accident airplane’s parking brake was part of the CE-560XL’s “normal brake system” and employed “controllable check valves that could prevent the return of hydraulic fluid after the brakes have been set.” The left-seat pilot normally sets the parking brake by “depressing the toe brakes and pulling out the black parking brake handle [pull knob] located on the lower left side of the instrument panel” (see exemplar CE-560XL in figure 1). The parking brake’s power (or resistance) could vary and is dependent upon the amount of force the pilot applied to the toe brakes before pulling the parking brake pull knob. The manufacturer’s operating manual does not specify how much force or length of time to apply to the toe brakes while setting the parking brake. If the CE-560XL toe brakes are not fully depressed when the parking brake valve is engaged, then only partial pressure would be trapped by the parking brake valve. In a submission for this investigation, the manufacturer stated that the parking brake valve is designed to also trap pressure in the brake lines if the parking brake pull knob is pulled first, followed by application of the toe brakes, but the manufacturer’s operating manual does not include that information. The parking brake pull knob on the CE-560XL is located on the lower left side of the instrument panel near the left-seat pilot’s left knee, which obscures it from the view of the right-seat pilot (see figure 2). Figure 1: View of the parking brake pull knob in the ON position in reference to the instrument panel in an exemplar CE-560XL. Figure 2: Location of the obscured parking brake pull knob within an exemplar CE-560XL When asked how to normally engage the parking brake during a postaccident interview, the pilot stated that he normally pressed on the toe brakes enough to stop the airplane’s taxi movement then pushed the toe brakes “a little bit more” and pulled the “lever.” He added that “you’re not standing on [the toe brakes].” The pilot further reported that it was his understanding that if the parking brake was set on the CE-560XL, the airplane “shouldn’t move” with takeoff power applied. When the copilot was asked if he believed the airplane could move with the parking brake engaged, he reported, “I have no expectations for anything.” According to the head of training at the training center where the pilot and copilot received their CE-560XL training, no CE-560XL airplane flight manual, checklist, or training curriculum provided a caution or warning that takeoff speeds may be achievable with full or partial pressure applied to the parking brake. Takeoff Warning Annunciator The airplane was equipped with a NO TAKEOFF warning light as part of the annunciator panel, but the parking brake lever was not a part of the alerting conditions. The airplane operating manual stated, in part: On the ground, the amber no takeoff annunciator will illuminate steadily if one or more of the following conditions exist: Flaps not within takeoff range (less than 7° or more than 15°), elevator out of trim for takeoff, horizontal stabilizer is out of takeoff position, or speed brakes are out of takeoff position. … Pressing the master caution will cause the flashing annunciator to change to steady on and the master caution to extinguish. Checklists Delta Private Jets (the operator) produced its normal CE-560XL checklists, which were adapted from the manufacturer’s airplane flight manual checklists, and the operator required its pilots to use the operator’s checklists. The Federal Aviation Administration certificate managing office accepted these adapted operator checklists in May 2017. The manufacturer’s “before starting engines” checklist called for the “park brake” to be set and the operator’s “before start” checklist called for the parking brake to be set by the left-seat pilot; therefore, both the manufacturers and operator’s checklists call for the parking brake to be set before the engines are started. There were no further checklist items referring to the parking brake in the manufacturers and operator’s checklists until the shutdown checklist. The third item of manufacturer’s taxi checklists stated, in part, “brakes…check”; the manufacturer stated that this step calls for the brakes to be tested. The operator’s taxi checklist also includes this item, but its flow diagram in the standard operating procedures points to the toe brakes rather than the parking brake pull knob for this checklist item. The rudder bias system is a check item in the operator’s taxi checklist and the manufacturers before taxi checklist. The operator’s rudder bias check procedures direct the pilot flying to verbalize “left throttle, left rudder… right throttle, right rudder” while checking the rudder bias. The pilot stated that he typically would have verbalized “parking brake on, parking brake off” when performing the rudder bias check; however, because the copilot was on the phone obtaining clearance and release for the flight, he did not verbalize those callouts during taxi. Certification The parking brake standard outlined in 14 CFR 25.735, Brakes and Braking Systems, was first established in 1965 and remained the standard until May 2002. To meet the original requirements of 14 CFR 25.735 in force between 1965 and 2002, the parking brake must prevent the airplane from rolling on a paved, level runway when set by the pilot with takeoff power on the critical engine. To certify the CE-560XL parking brake to that standard, the manufacturer demonstrated that the parking brake prevented the airplane from rolling when set with full parking brake pressure applied and one engine at takeoff power. The parking brake was not required to be tested with both engines at takeoff power, and the manufacturer did not test this condition. Effective May 2002, the Federal Aviation Administration amended 14 CFR 25.735 (Amendment 25-107) to state, in part, “There must be indication in the cockpit when the parking brake is not fully released.” However, the CE-560XL was initially certificated in 1998 (4 years before the parking brake indication amendment) and built to the initial 1965 standard, which does not require a cockpit indication if the parking brake is not fully released. Examination of the accident site revealed that the airplane came to rest about 1,990 ft beyond the departure end of runway 2 on a heading of about 078°. Examination of the runway revealed tire transfer marks which originated from near the runway 2 hold short line and progressed onto the runway then continued throughout the entire length of the runway, runway overrun, and a perpendicular oriented runway (see figure 3). The tire marks extended into a grassy area, across a taxiway, and within the grassy area near the main wreckage (see figure 4). Figure 3: View of the approach end of runway 2, with right main landing gear (MLG) transfer marks annotated. Figure 4: View of the accident site and runway environment. All major structural components of the airplane were located within the vicinity of the main wreckage. Examina