Pilot Debrief

EMBRAER EMB-505 near Banner Elk, NC — 2021-08-26

Final reportERA21LA353
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Date
2021-08-26
Location
Banner Elk, NC, USA
Airport
NC06
Aircraft
EMBRAER EMB-505
Registration
N413N
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Landing

Probable cause

The pilot’s failure to achieve the approach criteria for the available runway landing distances published in the POH, likely as a result of the steeper-than-normal approach and the required left turn on short final to avoid the terrain surrounding the airport. Contributing to the accident were a lower runway friction than that assumed by the airframe manufacturer and tire cornering forces imparted during the landing roll, which reduced the airplane’s reduced braking effectiveness, which when combined with a high approach speed, increased the required stopping distance beyond the runway distance available. Also contributing to the accident was the operator’s lack of consideration of airport topography in its Destination Airport Analysis Program.

Contributing factors

Contributing to the accident were a lower runway friction than that assumed by the airframe manufacturer and tire cornering forces imparted during the landing roll, which reduced the airplane’s reduced braking effectiveness, which when combined with a high approach speed, increased the required stopping distance beyond the runway distance available. Also contributing to the accident was the operator’s lack of consideration of airport topography in its Destination Airport Analysis Program.

NTSB narrative

The pilots were conducting a repositioning flight in a light business jet to a private airport located in mountainous terrain. Both pilots reviewed a manual and a video to become familiar with the unique approach and landing features at this airport along with the landing performance data for both a dry and a wet runway. Visual meteorological conditions existed at the time; however, a rainstorm had just passed over the airport, the runway was wet, and a security video showed rain as the airplane rolled down the runway. The PIC stated that he flew the approach at the landing reference speed (Vref) and applied full brakes once the airplane touched down on the 4,600 ft-long runway. The airplane did not slow down and started to veer to the right. The PIC applied full left rudder to steer the airplane back to the left to avoid a cliff located off the end of the runway. The PIC also stated that the airplane crossed over a small taxiway and into a grassy area, where the airplane’s left wing impacted a sign. The airplane continued to travel forward before the left wingtip impacted a parked vehicle, which stopped the airplane but also resulted in substantial damage to the left wing. Flight recorder data revealed that the airplane was configured to land (full flaps and landing gear extended) as it flew toward the airport. As the airplane was crossing over the runway threshold, it was still rolling back to a wings level attitude. The airplane’s indicated airspeed was 118 knots (the landing reference speed [Vref] for the assumed landing weight was 110 knots). The airplane touched down about 1,410 ft past the runway threshold with a 3-knot tailwind. The airplane landed about 9 ft to the right of the runway centerline and continued to drift right about 29 ft before returning toward the runway centerline. The pilot applied the brakes and used the rudder pedals to steer the airplane back to the left to maintain control, but this effort did not prevent the airplane from departing the runway. An airplane performance study of the FDR and other data for this accident determined that the airplane exceeded some of the landing criteria outlined in the manufacturer’s Pilot’s Operating Handbook (POH), which was most likely due to the unique characteristics of the landing approach, including a steeper-than-normal approach and the requirement for a left turn to align with the runway on short final, which would have made it more difficult to achieve the published landing distances outlined in the POH. In addition, the performance study found that the maximum wheel braking friction coefficient developed by the airplane during the landing ground roll was significantly less than that implied in the unfactored wet-runway landing distances published in the POH. The study further determined that, if the maximum wheel braking friction coefficient implied in the POH wet-runway landing distances had been achieved during the accident landing (and if maximum braking could have been maintained from the point at which both brakes were applied), the airplane would have stopped on the runway with about 290 ft remaining, even with the higher-than-nominal airspeed over the threshold. In addition, if the airplane had crossed the runway threshold at the Vref (instead of at Vref plus 8 knots) and had achieved the same maximum wheel braking friction coefficient as during the accident landing roll (lower than that implied in the POH but still with continuous braking), then the airplane would have stopped on the runway with about 265 ft remaining. However, the friction available from the runway has to be shared between the braking and cornering demands of the airplane. In this case, the airplane was unable to stop on the paved runway because the combination of the airspeed above Vref, the lower-than-assumed maximum wheel braking friction coefficient during the landing roll, and the cornering forces required for directional control increased the required stopping distance beyond the stopping distance available. The flight’s operator held a Part 135 operating certificate, but the accident flight was conducted under the provisions of Part 91. The operator’s General Operations Manual (GOM) did not state whether any of the Part 135 procedures or requirements for determining an airplane’s limiting weight at landing could be changed for a Part 91 repositioning flight. According to the pilot, he did not differentiate between a Part 91 and a Part 135 flight. The operator’s runway length requirements for dispatching flights under Part 135 were incorporated in the GOM. A review of those procedures revealed that the airplane could only have been dispatched (based on landing weight and runway conditions) using the Destination Airport Analysis Program (DAAP). The DAAP allows 80% of the available runway length to be used for landing instead of the 60% allowed by section 135.385(b), but 25% of the unfactored dry landing distance must still be added to the required runway length to account for wet conditions. The airplane’s calculated landing weight was 15,210 lbs. The unfactored dry runway landing distance using the 60% factor was 4,595 ft (2,757 ft. / 0.6). Dispatching to a wet runway with the 60% factor would require an additional 15% safety margin (as recommended by FAA SAFO 19001), or 689 ft, for a total required runway length of 5,284 ft. Therefore, the flight could not be dispatched to NC06 using the 60% factor. However, using the 80% factor the required dry runway length was 3,446 ft (2,757 /.08), and 4,135 ft with the 15% safety margin. Consequently, the airplane could only have been dispatched using the 80% factor. The GOM content for the DAAP is regulated by section 135.23(r), which in-part states that the GOM must account for “airport facilities and topography” when “establishing runway safety margins at destination airports.” However, the operator’s GOM did not specifically require consideration of airport facilities and topography in its DAAP. The absence of this requirement is concerning because the terrain surrounding the accident airport requires a relatively steep glidepath angle and a significant heading change on short final approach to the runway, which makes it difficult to achieve the airplane state at 50 ft above the runway threshold needed for the landing distances published in the manufacturer’s POH. Thus, if the operator’s GOM had considered airport topography (that is, the unique terrain and approach procedures for landing on the runway) as a DAAP requirement for calculating runway safety margins, the accident flight would most likely not have been dispatched. Per the GOM, the 80% factor can be used but only with prior permission from the director of operations. The available evidence did not show whether the pilot and the director of operations spoke before the accident about landing at the airport. However, the director of operations was aware that another company pilot had attempted to land at the airport 11 days before accident but diverted to another airport due to the terrain. The investigation revealed that the airplane could have landed using 80% of the available runway length, as outlined in the DAAP. However, the combination of factors described above increased the required landing distance beyond the runway distance available, and the pilot lost control of the airplane while maneuvering on the runway.

Analysis

Primary failure mode
Controlled flight into terrain
First missed decision gate
The decision to land at NC06 despite adverse weather conditions.

NTSB coding

Evidence available

  • CVR
  • Video
  • FDR / data
  • ADS-B / radar
  • Photos
  • 26 docket documents
View NTSB final reportView NTSB docket

Docket documents26

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