Sugarland, TX, USA
N584JS
EMBRAER S.A. EMB-500
The pilots of the very light jet were conducting a positioning flight in instrument meteorological conditions. The flight was cleared by air traffic control for the instrument landing system (ILS) approach; upon being cleared for landing, the tower controller reported to the crew that there was no standing water on the runway. Review of the airplane's flight data recorder (FDR) data revealed that the airplane reached 50 ft above touchdown zone elevation (TDZE) at an indicated airspeed of 118 knots (KIAS). The airplane crossed the runway displaced threshold about 112 KIAS, and it touched down on the runway at 104 KIAS with about a 7-knot tailwind. FDR data revealed that, about 1.6 seconds after touchdown of the main landing gear, the nose landing gear touched down and the pilot's brake pedal input increased, with intermediate oscillations, over a period of 7.5 seconds before reaching full pedal deflection. During this time, the airplane achieved its maximum wheel braking friction coefficient and deceleration. The cockpit voice recorder recorded both pilots express concern the that the airplane was not slowing. About 4 seconds after the airplane reached maximum deceleration, the pilot applied the emergency parking brake (EPB). Upon application of the EPB, the wheel speed dropped to zero and the airplane began to skid, which resulted in reverted-rubber hydroplaning, further decreasing the airplane's stopping performance. The airplane continued past the end of the runway, crossed a service road, and came to rest in a drainage ditch. Postaccident examination of the brake system and data downloaded from the brake control unit indicated that it functioned as commanded during the landing. The airplane was not equipped with thrust reversers or spoilers to aid in deceleration. The operator's standard operating procedures required pilots to conduct a go-around if the airspeed at 50 ft above TDZE exceeded 111 kts. Further, the landing distances published in the airplane flight manual (AFM) are based on the airplane slowing to its reference speed (Vref) of 101 KIAS at 50 ft over the runway threshold. The airplane's speed at that time exceeded Vref, which resulted in an increased runway distance required to stop; however, landing distance calculations performed in accordance with the AFM showed that the airplane should still have been able to stop on the available runway. An airplane performance study also showed that the airplane had adequate distance available on which to stop had the pilot continued to apply maximum braking rather than engage the EPB. The application of the EPB resulted in skidding, which increased the stopping distance. Although the runway was not contaminated with standing water at the time of the accident, the performance study revealed that the maximum wheel braking friction coefficient was significantly less than the values derived from the unfactored wet runway landing distances published in the AFM, and was more consistent with the AFM-provided landing distances for runways contaminated with standing water. Federal Aviation Administration Safety Alert for Operators (SAFO) 15009 warns operators that, "the advisory data for wet runway landings may not provide a safe stopping margin under all conditions" and advised them to assume "a braking action of medium or fair when computing time-of-arrival landing performance or [increase] the factor applied to the wet runway time-of-arrival landing performance data." It is likely that, based on the landing data in the AFM, the crew expected a faster rate of deceleration upon application of maximum braking; when that rate of deceleration was not achieved, the pilot chose to engage the EPB, which only further degraded the airplane's braking performance.
HISTORY OF FLIGHT On November 21, 2014, about 1010 central standard time, an Embraer EMB-500 (Phenom 100) airplane, N584JS, overran the runway after landing at Sugar Land Regional Airport (SGR), Sugar Land, Texas. The airline transport-rated pilots were not injured and the airplane was substantially damaged. The airplane was being operated by Superior Air Charter, LLC, Irvine, California (doing business as JetSuite Air), as a 14 Code of Federal Regulations (CFR) Part 91 positioning flight. Instrument meteorological conditions existed at the airport at the time of the accident, and the flight operated on an instrument flight rules flight plan. The flight originated from William P. Hobby Airport (HOU), Houston, Texas. According to the pilots, the purpose of the flight was to reposition the airplane from HOU to SGR. During the approach to SGR, the tower controller provided the pilots vectors to the airport and then told them to expect the instrument landing system (ILS) 35 approach at SGR. After the accident, the copilot reported that the tower controller cleared the flight to land and that there was no standing water on the runway. The copilot added that, during the approach, there was a tailwind of 15 kts that decreased to 9 kts on touchdown. After landing, the pilot, who was flying the airplane, applied the brakes and noted no appreciable deceleration. She then pulled the emergency brakes twice, but the airplane continued past the end of the runway and onto a grassy area. The airplane then crossed a service road and came to rest in a drainage ditch facing opposite the direction of travel with the empennage section partially submerged in water. A review of flight data recorder (FDR) data revealed that, while on the ILS approach to runway 35, the airplane slowed to 120 knots (kts) and that it maintained that airspeed until about 155 ft mean sea level (msl), at which point it slowed to about 118 kts. The airplane remained on the glideslope until about 380 ft msl, when the cockpit voice recorder (CVR) recorded an electronic voice stating "autopilot," consistent with autopilot disconnection. Shortly after, the airplane descended below the glideslope. The airplane crossed the displaced threshold about 100 ft msl and at 112 kts indicated airspeed (KIAS), and touched down at 1010:37, about 1,040 ft from the threshold, at an airspeed of 104 KIAS. During the landing roll, the CVR recorded the pilots concern about the airplane's lack of deceleration. About 1.6 seconds after touchdown, the nose landing gear touched down, and the pilot's brake pedal increased, with intermediate oscillations, over a period of 7.5 seconds and reached full pedal deflection. About 4 seconds later, the emergency/parking brake (EPB) was applied, at which point the wheel speed dropped from 70 to 0 kts, consistent with a locked-wheel skid. Concurrently, the FDR recorded an engine indication and crew alerting system ANTI-SKID FAIL message, consistent with the application of the EPB and locking of the wheels. The airplane departed the runway at 1011:15 at a groundspeed of about 30 KIAS. Shortly after, the FDR recorded accelerations consistent with the impact and airplane coming to a stop. PERSONNEL INFORMATION Pilot The pilot held an airline transport pilot certificate with airplane single-engine land, multi-engine land, and instrument ratings. Additionally, she held an instructor's certificate with airplane single-engine and instrument ratings. She reported that she had 6,311 total flight hours and 1,110 hours in the accident airplane make and model. The captain was issued a Federal Aviation Administration (FAA) first-class medical certificate on July 29, 2014. Copilot The copilot held an airline transport pilot certificate with airplane single-engine land, multi-engine land, and instrument ratings. He reported that he had 4,232 total flight hours and 814 hours in the accident airplane make and model. The copilot was issued an FAA first-class medical certificate on July 26, 2014, with the restriction, "must wear corrective lenses." AIRCRAFT INFORMATION The Embraer EMB-500 Phenom 100 is included in the very light jet (VLJ) class of airplane. The Phenom 100 can seat four passengers in its normal configuration, but it can be configured to carry up to seven passengers. The airplane is equipped with two Pratt & Whitney Canada PW617-F turbofan engines each rated at a takeoff thrust of 1,695 lbs. The accident airplane's serial number was (S/N) 50000140 and was certified as a 14 CFR 23 normal category airplane. The EMB-500 is not equipped with thrust reversers, and prior to serial # 50000325 not equipped with spoilers. All EMB-500s from serial # 50000325 onwards are equipped with spoilers when delivered from the factory. The accident airplane was not equipped with spoilers. Brake System The Phenom 100's hydraulic brake system delivers hydraulic pressure to the brakes via input on the brake pedals. The hydraulic pressure to the brake system is supplied at a maximum of 3,000 pounds per square inch (psi). The copilot's (right seat) brake pedals are mechanically linked to the pilot's (left seat) brake pedals. Each pilot brake pedal is connected to a pedal position transducer (PPT), each of which produces two independent electrical outputs to the brake control unit (BCU) that were proportional to the respective pedal displacement. The BCU controls the main brake system. The brake system is a brake-by-wire system with an antiskid function. There are no hydraulic components on the brake control; therefore, the only pedal force feedback to the pilots is from a force spring installed on the pedals. This provides a consistent pedal resistance regardless of the runway condition and the pressure applied. Wheel speed information is sent to the BCU via two axle-mounted speed transducers. The BCU uses the output from the wheel speed transducers, the PPTs, and two brake line pressure transducers to generate an electrical command to the associated brake control valve (BCV). Anti-skid protection is provided when the BCU detect a skid by monitoring the two-wheel speed transducer signals. If a skid is detected, the BCU sends a signal to the BCV to reduce pressure to the brakes. The antiskid protection cannot be turned off in the cockpit. The Phenom 100 is equipped with an EPB to stop the airplane if the main brake system fails and to provide means to keep the aircraft parked even when the hydraulic power system is turned off. The EPB is operated by a T-handle on the control pedestal. The handle is mechanically linked to the emergency brake valve. Upon using the EPB, the pressure applied is proportional to the handle displacement. No anti-skid protection is available. Certification In general, 14 CFR Part 23 certification regulations require that dry-runway landing distances be published in airplane flight manuals (AFM) and that they be based on performance demonstrated during flight tests on smooth, dry, hard-surfaced runways. Certification regulations do not require the publication of landing distances on other-than-dry runways, although certification applicants may choose to present this information to the regulator. If the applicant provided this information, it would not necessarily be based on flight tests (largely because of the difficulty of achieving a consistent "wet" or "contaminated" runway surface) but rather derived by calculations based on assumptions agreed to by the regulator. The EMB-500 was first certified by the Brazilian regulator (the Agência Nacional de Aviação Civil), which, like the FAA, does not require the publication of landing distances on other-than-dry runways. However, the European Aviation Safety Agency (EASA) does require the publication of landing distances on other-than-dry runways if the airplane is to be operated on such runways. The unfactored landing distance is the actual distance from the runway threshold required to land the airplane and stop it without any safety factors applied. The factored landing distance is the actual distance from the runway threshold required to land the airplane and stop increased by a safety factor. Therefore, to certify the airplane in Europe, Embraer proposed to EASA that the unfactored wet runway landing distances presented in the EMB-500 AFM would be computed as 125% of the demonstrated, unfactored dry-landing distance, and EASA accepted this proposal. The factored wet-runway landing distances in the EMB-500 AFM are 115% of the factored dry distances or 192% of the unfactored dry distances. The EMB-500 is certified in the "normal" category, not the "commuter" category; therefore, 135.385(c) did not apply to the accident airplane. However, in practice, JetSuite operates the EMB-500 in compliance with 135.385(c). The EMB-500 AFM also provides a table of landing distances for landings on runways covered with standing water, slush, or wet snow at depths of 0.125, 0.250, and 0.375 inches. METEOROLOGICAL INFORMATION At 1012, the SGR automated weather observation system (AWOS) reported wind from 130° at 8 kts, 6 miles visibility, light rain and mist, broken clouds at 3,300 ft and an overcast ceiling at 4,200 ft, temperature 66°F, dew point 64°F, and a barometric pressure of 30.15 inches of mercury. At 1025, the SGR AWOS reported wind from 130° at 8 kts, 10 miles visibility, few clouds at 600 ft, and broken clouds at 1,800 ft and an overcast ceiling at 4,400 ft. AIRPORT INFORMATION SGR is a public-use, towered airport, located 17 miles southwest of Houston, Texas. SGR has a single concrete runway, 35/17, which is 8,000 ft long and 100 ft wide. Runway 17 has a 380 ft displaced threshold; runway 35 has a 1,984 ft displaced threshold. Runway 35 touchdown zone elevation is 78 ft. FLIGHT RECORDERS The CVR were removed from the airplane and examined at the National Transportation Safety Board's Vehicle Recorder Lab in Washington, DC. The FDR data file was downloaded by the operator and sent to the NTSB's Vehicle Recorder Lab. WRECKAGE AND IMPACT INFORMATION The airplane came to rest about 100 ft beyond the end of runway 35 down a small embankment in a drainage creek filled with water. The airplane had spun around about 148° opposite the direction of travel with the front of the airplane on the embankment The aft section of the airplane was submerged in water, and the tail cone was partly broken and separated from the empennage. The right main landing gear had collapsed, and the right-wing tip and aileron were damaged. TESTS AND RESEARCH BCU The BCU was removed from the airplane and sent to the unit's manufacturer's facility in Ohio. No visual defects were noted, and the BCU was functionally tested, and it functioned normally. Data were downloaded from the BCU, and no abnormities were noted with the braking system. Airplane Performance Study The NTSB conducted an Airplane Performance Study for the accident flight to determine the airplane's position and orientation during the relevant portion of the flight and its responses to control inputs, external disturbances, ground forces, and other factors that could affect its trajectory. The study used various data sources, including FDR and airplane thrust and aerodynamic performance information. According to the performance study, the airplane's approach to runway 35 complied with the operator's stabilized approach criteria, with the airplane tracking the RNAV final approach course and glideslope at an airspeed of about 130 knots. The CVR recorded the copilot, who was the pilot monitoring (PM), call "1000 … stable" at 1009:10.3 when the airplane was at an indicated altitude of 1,103 ft (1,021 ft above the field elevation (AFE) of 82 ft) and about 147 KIAS, or 27 kts above the approach speed (Vap of 120 kts. Per JetSuite's Standard Operating Procedures (SOPs, the PM would have been required to call "1000 continue, speed" because the speed exceeded Vap + 5 kts. As the airplane descended below an indicated altitude of 800 ft msl (about 722 ft above the touchdown zone elevation [TDZE] of 78.4 ft) while on the ILS approach to runway 35, it slowed to 120 kts, which is the flaps 3 Vap (approach speed) specified in JetSuite's SOPs. During the final approach, the airplane remained on the glideslope until about 380 ftmsl (302 ft above TDZE), when the CVR recorded an electronic voice stating "autopilot," indicating that the autopilot had been disconnected. Shortly after, the airplane descended below the glideslope. The airplane maintained 120 kts until about 155 ft msl (about 77 ft above TDZE), then slowed to about 118 kts at 50 ft above TDZE, and then slowed to 104 KIAS at touchdown. The airplane crossed the runway 35 displaced threshold at an indicated altitude of about 100 ft msl (22 f above TDZE) and about 112 KIAS, and it touched down at 1010:37.4, 1,040 ft from the threshold at a groundspeed of 111 kts with about a 7 tailwind. The CVR did not record the pilots making any speed callouts between 500 ft above field elevation (AFE and 50 ft above TDZE, even though at least one speed callout in this band is required by the SOPs. In addition, the EMB-500 AFM specified that at the landing weight of about 8950 lbs, the flaps 3 Vref is 101 kts. The SOPs required pilots to go-around if the airspeed at 50 ft above TDZE exceeded about 111 kts. As noted above, at an indicated altitude of 50 ft above TDZE (128 ftmsl), the indicated airspeed was about 118 kts, 7 kts, above the approximate 111-kts limit. The landing distances published in the EMB-500 AFM are predicated on the airplane slowing to reference speed (Vref at 50 ft over the threshold. During the accident landing, the speed at 50 ft exceeded Vref by about 17 kts and resulted in an increased runway distance required to stop. Runway 35, even with the higher threshold crossing speed and assuming that the airplane braking performance implied in the AFM landing distances could be achieved, had an available landing distance of 6,016 ft, which met JetSuite's General Operations Manual (GOM) wet-runway dispatch ("planning") requirement of 1.92 times the unfactored dry landing distance, which for this landing would have been 2,695 ft times 1.92 or 5,174 ft. About 1.6 seconds after touchdown, the nose landing gear touched down, and the pilot's brake pedal increased, with intermediate oscillations, over a period of 7.5 seconds and reached full pedal deflection at about 1010:46.6. During this time, the airplane maintained a deceleration (longitudinal load factor, nx) that oscillated between -0.05 and -0.10 G's; and averaged about -0.07 G's. At 1010:49.7, 3.1 seconds after the brake pedals reached maximum deflection, the nx suddenly decreased to a minimum (i.e., a maximum deceleration) of -0.162 G's. Between 10:10:50 and 10:10:58, the nx oscillated between about -0.11 and -0.14 G's. At 10:10:50.7, the Emergency / Parking Brake (EPB) was applied, and the right and left wheel speeds decreased to 0 at 1010:55.2 and 10:10:58.2, respectively. After both wheel speeds reached zero, the nx increased (indicating decreased deceleration) to between about -0.08 and -0.11 G's until about 1011:11, when the airplane started to yaw to the left and drift to the right. The airplane departed the runway at 1011:15, at a groundspeed of about 30 knots, and came to rest in a drainage ditch about 500 feet past the end of the runway. For about the first 12 seconds after touchdown, the computed braking coefficient oscillated about a value of 0.03 (the assumed unbraked, rolling braking coefficient) with peaks between 0 and about 0.1. The braking coefficient remained at this low value even as the brake pedals were depressed and then jumped to an average of between 0.13 and 0.14 at 1010:50, coincident with the decrease in nx (that is, increased deceleration). As part of the performance study, in May 2015, the NTSB and the partie
The pilot's engagement of the emergency parking brake during the landing roll, which decreased the airplane's braking performance and prevented it from stopping on the available runway. Contributing to the pilot's decision to engage the emergency parking brake was the expectation of a faster rate of deceleration and considerably shorter wet runway landing distance provided by the airplane flight manual than that experienced by the crew upon touchdown and an actual wet runway friction level lower than the assumed runway fiction level used in the calculation of the stopping distances published in the airplane flight manual.
Source: NTSB Aviation Accident Database
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