History of Flight
On April 5, 2013, at approximately 1509 central daylight time, an Embraer EMB-500 (registration N196EC) experienced an antiskid brake system failure immediately prior to touchdown on runway 1/19 at Key Field Airport (MEI), Meridian, Mississippi. The airline transport pilot was not injured and the airplane sustained no damage. Visual meteorological conditions prevailed and an instrument flight rules flight plan had been filed for the positioning flight, which originated from Destin-Fort Walton Beach Airport (DTS), Destin, Florida, about 1430. The airplane was registered to and operated by Progressive Aviation, LLC under Title 14 Code of Federal Regulations Part 91.
According to the pilot, after touchdown he applied the brakes and the airplane immediately began "sliding similar to hydroplaning." The airplane slid approximately 2,800 feet down the runway before coming to a stop. Examination of the main landing gear revealed that both tires had deflated. The tires were replaced and the airplane taxied to a hangar without further abnormalities. Initial examination by a Federal Aviation Administration inspector revealed that both main landing gear tires had wear marks similar to being locked up while the airplane was in motion.
Personnel Information
The pilot, age 45, held an airline transport pilot certificate with airplane multiengine land ratings, and a commercial pilot certificate with an airplane single-engine land rating. A second-class airman medical certificate was issued on October 12, 2012, with no limitations. The pilot reported 2,500 total hours of flight experience, with 250 hours in the accident airplane make and model.
Aircraft Information
The six-seat, low-wing, retractable landing gear, pressurized T-tail airplane was manufactured in 2010. It was powered by two Pratt & Whitney Canada PW617F-E turbofan engines mounted on the aft fuselage.
A review of the pilot operating handbook (POH) indicated that the main landing gear brakes are a brake-by-wire system controlled by either pilot or copilot seat rudder pedals. The rudder pedals actuate pedal transducers that send brake inputs to the Brake Control Unit (BCU). The BCU, connected to DC BUS 2, receives all brake interface signals and controls the Shutoff Valve (SOV) and both Brake Control Valves (BCVs) for braking capability. The POH states: "In case of main brake failure, the Emergency/Parking brake is available and must be used carefully to stop the airplane."
The POH further states, in part, "…the antiskid protection prevents tire skidding and maximizes brake efficiency according to the runway surface." The system controls hydraulic pressure applied to the brakes and meters wheel brake pressure to recover wheel speed and prevent skidding. The antiskid system is deactivated for wheel speeds below 10 knots. Antiskid protection is not available for the emergency/parking brake system.
The brake system includes touchdown protection, which inhibits brake pressure if the brake pedals are applied prior to touchdown. Touchdown protection receives input from the weight on wheel (WOW) proximity switch and is deactivated when wheel speed exceeds 30 knots or 5 seconds after WOW senses ground contact. Locked wheel protection compares main landing gear wheel speeds; if one wheel speed becomes about 30 percent lower than the reference velocity, full brake pressure relief is commanded, allowing wheel speed recovery. This system becomes active at about 30 knots.
The airplane was not equipped with thrust reversers, spoilers, or leading edge slats.
Meteorological Information
The 1458 recorded weather observation at MEI included wind from 340 degrees at 10 knots, visibility 10 miles, clear skies, temperature 18°C, dew point 8°C, and barometric altimeter 30.09 inches of mercury.
Airport Information
Key Field Airport is a publicly owned airport with an operating control tower at the time. It has two runways: runway 1/19 (10,003 feet long, 150 feet wide) and runway 4/22 (4,599 feet long, 150 feet wide). The airport elevation is 298 feet above mean sea level. The runway was dry during the incident.
Flight Recorders and Testing
The airplane was equipped with a cockpit voice and data recorder (CVDR) and a Central Maintenance Computer (CMC). Both were downloaded and data transmitted to Embraer for analysis. Examination of the impact switch associated with the CVDR revealed it had been activated, requiring exposure to a 5g deceleration; however, recorded data showed no such exposure, with the greatest recorded level about 1.273g. The CMC logged a "BRAKE CONTROL UNIT FAIL" and the crew alerting system message "ANTI-SKID FAIL" 2 and 1 seconds prior to touchdown. Wheel speed transducers were tested with no abnormalities found.
The BCU, manufactured by Meggitt Aircraft Braking Systems, was sent to the NTSB Recorders Laboratory for download. Fault codes indicated "Lt ws ga dsgree," "Rt ws ga dsgree," and no weight on wheels. Right and left wheel speeds were 85.95 and 85.11 knots respectively. Right brake pedal application was 36%, left 2%. Right brake pressure showed 182.23 psi, left 50.26 psi.
The BCU was examined at the manufacturing facility in Dayton, Ohio, under NTSB supervision. Functional testing on a test bench showed normal operation with no anomalies.