Conroe, TX, USA
N322QS
EMBRAER EMB 505
The pilot-in-command (PIC) and second-in-command (SIC) were conducting a positioning flight. According to the dispatch flight release, the pilots planned to land on runway 14, which was assumed to be wet. Before the flight, notices to airmen (NOTAMs) had been issued, which stated that the runway 14 threshold had been displaced 3,377 ft and that the instrument landing system and RNAV instrument approaches were not available. Although the NOTAMs were included in the flight release paperwork, dispatch personnel overlooked them, which resulted in flight planning numbers predicated on the full length of runway 14. During the approach, the pilots listened to the automatic terminal information service information and then became aware that runway 14 was shortened due to construction. Subsequently, the pilots calculated the landing distance required to land on a wet runway and chose to land on runway 1, which was the longer runway. The PIC reported that, during the approach, they encountered light rain but that the rain was moving away from the airport, which alleviated any concern regarding standing water on the runway. A review of flight data recorder data showed that the SIC flew a stabilized approach 9 knots above the reference speed (Vref) and that the airplane touched down 903 ft from the runway threshold at a groundspeed of 118 knots. The SIC stated that he began braking with half pressure and continued to increase the brake pressure to maximum, which was the normal braking procedure, but that the airplane did not appear to be decelerating. FDR data confirmed that the SIC began applying the brakes immediately upon touchdown and progressively commanded full braking performance from the brake system. The PIC informed the SIC that they needed to slow down, and the SIC replied that he had "no braking." The SIC then applied the emergency parking brake (EPB), but the airplane still did not slow down. FDR data indicated that the airplane achieved its maximum deceleration during the landing roll before the application of the EPB. FDR data showed that, once the SIC applied the EPB, the wheel speed dropped to 0. After determining that there was insufficient runway remaining for a go-around, the pilots realized that the airplane was going to exit the end of the runway. Subsequently, the airplane began to skid along the runway, which resulted in reverted-rubber hydroplaning, thus decreasing the stopping performance, and then exited the departure end of the runway and continued about 400 ft in soft terrain before it impacted a ditch and came to a stop. An examination of the brake system and data downloaded from the brake control unit indicated that the brake system functioned as commanded during the landing. Analysis of the runway surface and the amount of precipitation showed that there should have been no standing water on the runway. Landing distance calculations performed in accordance with the aircraft flight manual (AFM) showed that, even though the SIC exceeded Vref, the airplane should have been able to stop on the available runway. According to the National Transportation Safety Board's airplane performance study, the maximum wheel braking friction coefficient achieved during the portion of the ground roll before the application of the EPB was significantly less than the maximum wheel braking coefficient that would have been expected given the unfactored wet-runway landing distances published in the AFM. However, the study determined that, if the EPB had not been engaged and airplane had maintained the braking friction level attained during the landing roll before the engagement of the EPB, it would have been able to stop on the available runway. Therefore, the SIC's application of the EPB, which locked the wheels, reduced the friction level, and decreased the braking performance, prevented the airplane from stopping on the available runway. Nonetheless, the braking friction deficit observed in this accident showed that the stopping performance of the airplane was more consistent with AFM landing distances for runways contaminated with standing water than for runways that were merely "wet" even though it was determined that the runway could not have been flooded. Since the accident, the operator has issued a flight operations bulletin instructing pilots to conduct a landing distance assessment using the AFM contaminated runway performance data for the lowest contamination depth when the following three conditions exist: 1) the runway did not have a treated surface, 2) thrust reversers were deferred or not installed, and 3) the airport was reporting rain or heavy rain.
HISTORY OF FLIGHT On September 19, 2014, about 0847 central daylight time, an Embraer EMB-505 Phenom 300 airplane, N322QS, impacted a ditch after the airplane departed the end of the runway while landing at Lone Star Executive Airport (CXO), Conroe, Texas. Neither of the two airline transport-rated pilots were injured. The airplane was substantially damaged. The airplane was being operated by NetJets Aviation, Inc. (NetJets), 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 an instrument flight rules flight plan had been filed. The flight originated from Nashville International Airport, Nashville, Tennessee, at 0706. According to the dispatch flight release paperwork, the pilot-in-command (PIC) and second-in-command (SIC) planned to land on runway 14, which was assumed to be wet. Before the flight, notices to airmen (NOTAMs) had been issued, which stated that the runway 14 threshold had been displaced 3,377 ft and that the instrument landing system (ILS) and RNAV instrument approaches were not available. Although the NOTAMs were included in the flight release paperwork, dispatch personnel overlooked them, which resulted in flight planning numbers predicated on the full length of runway 14. According to cockpit voice recorder (CVR) information, at 0827:04, the pilots received the automatic terminal information service (ATIS) information, which indicated that the runway 14 takeoff and landing distance was 4,111 ft and that the ILS for runway 14 was out of service. The pilots calculated the runway length required for a wet runway landing and then chose to land on runway 1, which was the longer runway. The PIC stated that, during the approach, the flight encountered light rain but that the rain was moving from the northwest to the southeast, away from the airport and that this alleviated any concern about standing water on the runway. He added that both he and the SIC had previously landed the EMB-505 in moderate-to-heavy rain with no decrease in braking ability. The CVR recorded the pilots briefing the approach and missed approach procedures. Subsequently, the tower controller cleared the runway 1 RNAV approach, and the pilots then discussed alternate airports in the area. At 0841:30, the tower controller cleared the airplane to land and stated that moderate-to-heavy rain was at the airport. The pilots conducted the Before Landing checklist and continued the approach. While continuing the approach with the SIC flying the airplane, they saw the runway at 600 ft above ground level, and the copilot disengaged the autopilot at 400 ft. At 200 ft, the SIC reduced the power and adjusted the altitude and airspeed for a stabilized approach with a maximum airspeed during the approach of 130 knots. In his postaccident written statement, the PIC stated that the landing appeared normal and "smooth." The SIC stated that he began braking with half pressure and continued to increase the brake pressure to maximum, which was the normal braking procedure. Sounds recorded on the CVR consistent with the airplane touching down were heard at 0837:13, followed by the pilots stating that the airplane was not slowing down. The SIC stated, "brakes. Emergency brakes," followed by "nothin' man" and "I got nothin'." The PIC stated "where's the brakes," followed by "where are they?" The PIC then said "go…don't go sideways, don't go sideways." The airplane exited the departure end of the runway and continued about 400 ft through soft/muddy terrain before coming to rest half-way down a ditch. According to the air traffic controller who witnessed the accident, the pilots flew the RNAV runway 1 approach and broke out of the clouds at the minimums for the approach. The controller stated that the airplane touched down just past the 1,000-ft marker on the runway and did not appear to decelerate as it continued down the runway. PERSONNEL INFORMATION PIC The PIC held an airline transport pilot certificate with an airplane multiengine land rating and a commercial pilot certificate with airplane single-engine land and balloon ratings. He held type ratings in Cessna 500, 650, and 750; Embraer 505; and Hawker Siddeley HS-125 airplanes. A limitation on the EMB-505 type rating was the requirement of an SIC. The PIC's last flight check was in the EMB-505 on May 12, 2014. The PIC was issued a first-class Federal Aviation Administration (FAA) medical certificate on April 3, 2014, which contained the limitations that it was not valid for any class after October 31, 2014, and that he must wear corrective lenses. He had 13,466 hours of flight time, of which 322 hours were in EMB-505 airplanes. SIC The SIC held an airline transport pilot certificate with an airplane multiengine land rating and a commercial pilot certificate with an airplane single-engine land rating. He held type ratings in ATR-42, ATR-72, Cessna 750, Bombardier CL-65, and Embraer 505 airplanes. Limitations on the CL-65 type rating were SIC privileges only and circling approaches in visual meteorological conditions. A limitation on the EMB-505 type rating was the requirement of an SIC. The SIC's last flight check was in the EMB-505 on May 12, 2014. The SIC was issued a first-class FAA medical certificate on July 22, 2014, with no limitations. He had 9,861 hours of flight time, of which 361 hours were in EMB-505 airplanes. AIRCRAFT INFORMATION The accident airplane was a twin-engine turbofan, low-wing airplane, serial number 50500165, manufactured in 2013. The airplane was type certificated as a 14 CFR Part 23 commuter category airplane and was configured for two flight crewmembers and seven passengers. The airplane was equipped with two Pratt & Whitney PW535E turbofan engines, each of which delivered 3,360 lbs of thrust. The airplane was maintained in accordance with the manufacturer's inspection program. The last inspection was completed on July 2, 2014, at a total airframe time of 597.7 hours. Brake System The airplane's hydraulic brake system delivered hydraulic pressure to the brakes via input from the brake pedals. The hydraulic pressure to the brake system was supplied at a maximum of 3,000 pounds per square inch (psi). The SIC (right seat) brake pedals were mechanically linked to the PIC (left seat) brake pedals. Each PIC brake pedal was connected to a pedal position transducer (PPT), each of which produced two independent electrical outputs that were proportional to the respective pedal displacement to the brake control unit (BCU). The BCU controlled the main brake system, which was a brake-by-wire system with an antiskid function. The only pedal force feedback to the pilots was from a force spring installed on the pedals that provided a consistent pedal resistance regardless of the runway condition and the pressure applied. Wheel speed information was sent to the BCU via two axle-mounted speed transducers. The BCU factored the output from the wheel speed transducers, the PPTs, and two brake line pressure transducers then sent an electrical command to the associated brake control valve. The brake system had an antiskid function (which controls slip ratio) and a locked-wheel protection (which detects deep skids). The antiskid function worked independently on each wheel by comparing the current wheel angular speed to a reference angular speed, which was calculated based on the speed of that same wheel. The locked-wheel protection compared both main landing gear (MLG) wheel speeds and alleviated brake pressure when the slower wheel fell below 30% of the opposite wheel speed. The airplane was equipped with an EPB to stop the airplane if the main brake system failed. The EPB was operated by a T-handle on the control pedestal, which was mechanically linked via a steel cable to the EPB valve. The antiskid function was not available when using the EPB. An examination of the brake system and the data downloaded from the brake control unit (BCU) indicate that the brake system functioned as commanded during the landing. Ground Spoiler Function The airplane had a ground spoiler function that deployed the spoiler panels on the ground during landing to decrease lift, increase drag, improve braking, and reduce stopping distance. The airplane must be on the ground, the thrust levers must be in the "idle" position, and the ground spoilers must be armed for them to deploy during landing. The ground spoiler function automatically armed when the weight-on-wheels (WOW) sensors indicated "in-air" for more than 10 seconds and the airspeed was valid and greater than 60 knots indicated airspeed (KIAS). 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-505 was first certificated by the Brazilian regulator (the Agência Nacional de Aviacão 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. Therefore, to certify the airplane in Europe, Embraer proposed to EASA that the unfactored wet-runway landing distances presented in the EMB-505 AFM would be computed as 125% of the demonstrated, unfactored dry-landing distance, and EASA accepted this proposal. 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. The factored wet-runway distances in the EMB-505 AFM were 115% of the factored dry distances, or 192% of the unfactored dry distances. The EMB-505 AFM also provided 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 0841, the CXO automated surface observation system reported calm wind, visibility 2 miles in heavy rain and mist, a few clouds at 500 ft above ground level (agl), ceiling 8,000 ft agl broken, 10,000 ft agl overcast, temperature 23° C, dew point 22° C, and altimeter setting of 29.93 inches of Mercury. Remarks included the following: hourly precipitation 0.21 inch, temperature 22.8° C, and dew point 22.2° C. A review of weather observations reported before and after the accident showed that the rain began at 0444. The rain varied from moderate-to-heavy intensity from 0725 until after the accident. The rain ended at 1129. The total precipitation reported between 0444 and 0847 (the time of the accident) was 0.45 inch. The total precipitation reported between 0444 and 1129 was 0.50 inch. AIRPORT INFORMATION CXO is located about 37 miles north of Houston, Texas. The airport is equipped with an air traffic control tower, which is operational between 0700 and 2200. The airport chart supplement lists an elevation of 245 ft and a magnetic variation of 5° east. Runway 1/19 is 5,000 ft long and 100 ft wide, concrete, and in good condition with a threshold elevation of 230 ft and 0.2% grade. The runway has a medium-intensity approach lighting system and nonprecision runway marking. The runway also has a two-light precision approach path indicator lighting system, which was out of service. Runway 14/32 was under construction at the time of the accident. As noted earlier, a NOTAM had been issued, which stated that the runway 14 threshold had been displaced 3,377 ft and that the ILS and RNAV instrument approaches were not available. The dispatch Flight Release for N322QS, showed that the landing was planned for runway 14 which was assumed to be wet. The NOTAMs were included in the Flight Release paperwork, but were overlooked by dispatch resulting in flight planning numbers predicated on the full length of runway 14. The pilots became aware of the runway information during the flight and they opted to land on runway 01. The automated terminal information service (ATIS) ZULU which was received by the crew reported the runway 14 takeoff and landing distance was 4,111 ft and the ILS for runway 14 was out of service. WRECKAGE AND IMPACT INFORMATION According to the FAA inspector who arrived on scene shortly after the accident, there were light tire scuffmarks on runway1, which began 1,877 ft before the departure end of the runway. There were no visible signs of rubber transfer on the runway. The airplane exited the departure end of the runway and continued about 400 ft through soft/muddy terrain before coming to rest on down-sloping terrain. The distance between the ground tracks made by the nose tire and the right MLG gear track was 18 inches, indicating that the airplane skidded after it departed the runway surface. A flat worn spot was visible on both the left and right main tires. Both tires showed evidence of reverted rubber hydroplaning. The airplane contacted a silt/erosion control fence during the overrun. The nose landing gear collapsed and separated from the airplane just before it came to rest. The airplane sustained substantial damage, including, but not limited to, damage to the forward bulkheads, composite ribs, forward fuselage frame, and the center fuselage area. Power was applied to the airplane after the accident, and a ground hydraulic power stand was used to generate a hydraulic system pressure of 2,850 psi. The brakes and spoiler system were tested, and both functioned normally. The antiskid auto-startup test was completed with no faults noted. TESTS AND RESEARCH BCU and Central Maintenance Computer (CMC) The BCU, serial number 276920254, was removed from the airplane and sent to Meggitt in the United Kingdom. The recorded faults were downloaded, and the BCU was functionally tested under the supervision of an investigator from the Air Accidents Investigation Branch, and it functioned normally. Embraer downloaded the CMC messages on scene with the concurrence of the National Transportation Safety Board (NTSB) investigator-in-charge. The BCU faults and CMC faults and messages were correlated with one another and reviewed by Embraer. Although the BCU and CMC recorded four sequences of faults and messages, the data and the examination of the brake system indicated that the brake system functioned as commanded during the landing. FLIGHT RECORDERS The airplane was equipped with an L-3/Fairchild FA2100-3083 combination cockpit voice and flight data recorder (CVDR), serial number 000885510, which provided both flight data recorder (FDR) and cockpit voice recorder (CVR) functions. The CVDR was removed from the wreckage and examined at the NTSB Vehicle Recorder Laboratory, Washington, DC. The CVR contained 2 hours 4 minutes 14 seconds of good quality voice recordings. A CVR group was convened, and a transcript was prepared for the period from 0824:47 to 0848:01. FDR Data The FDR contained 222 hours of data. Timing of the FDR data is measured in subframe reference numbers (SRN), where each SRN equals 1 lapsed second. The accident flight was the last flight on the recording, and the flight duration was about 1 hour 37 minutes. The FDR data showed the airplane initially on approach above 150 knots. From 0844:18 to 0844:38, the flap position increased from flap position "one" through to flap position "three," at which position it remained for the rest of the approach. At 0844:43, the brake pressure for the left and right MLG briefly spik
The second-in-command's (SIC) engagement of the emergency parking brake (EPB), which decreased the airplane's braking performance and prevented it from stopping on the available runway. Contributing to the SIC's decision to engage the EPB was the lower-than-anticipated deceleration due to a wet-runway friction level that was far lower than the levels used to determine the wet-runway stopping distances in the Airplane Flight Manual (AFM) and necessitated a landing distance considerably greater than that published in the AFM.
Source: NTSB Aviation Accident Database
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