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Aviation Accident

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NTSB Identification: CEN14FA505
14 CFR Part 91: General Aviation
Accident occurred Friday, September 19, 2014 in Conroe, TX
Probable Cause Approval Date: 04/19/2017
Aircraft: EMBRAER EMB 505, registration: N322QS
Injuries: 2 Uninjured.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

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.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
  • 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.