Thursday, July 23, 2020

Controlled Flight Into Terrain: Bell 206B-3 JetRanger III, N417WT; fatal accident occurred November 03, 2018 in Uvalde, Texas

Mr. & Mrs. Byler

Gerald Green Lawrence

Craig Hatch, ICC
National Transportation Safety Board Investigator-In-Charge (IIC) Craig Hatch speaks during a briefing held November 5th, 2018 at the Uvalde County Office of Emergency Management.

The National Transportation Safety Board traveled to the scene of this accident.

Additional Participating Entities:

Federal Aviation Administration / Flight Standards District Office; San Antonio, Texas
Federal Aviation Administration Rotorcraft Standards; Fort Worth, Texas
Bell Helicopters; Fort Worth, Texas
Rolls-Royce Corporation; Indianapolis, Indiana

Aviation Accident Final Report - National Transportation Safety Board:

Investigation Docket - National Transportation Safety Board: 

Location: Uvalde, TX
Accident Number: CEN19FA024
Date & Time: 11/03/2018, 2347 CST
Registration: N417WT
Aircraft: Bell 206
Aircraft Damage: Destroyed
Defining Event: Controlled flight into terr/obj (CFIT)
Injuries: 3 Fatal
Flight Conducted Under: Part 91: General Aviation - Personal


The pilot and two passengers onboard the turboshaft-powered helicopter departed from a private ranch on a night cross-country flight in visual meteorological conditions. Video evidence from witnesses who observed the departure showed that bright flood lights were shown directly at the helicopter during the departure. The helicopter impacted terrain shortly after takeoff about 100 ft below the top of a 1,500-ft hill and about 5 miles east of the departure point.

An automated weather station, located 13 miles southeast of the departure site, at 0015 recorded, clear skies, and an altimeter setting of 29.97 inHg. A review of weather information about the time of the accident revealed a small area of cloud ceilings east of the departure point. Based upon the helicopter's recorded route of flight, it is unlikely that the helicopter encountered this area of reduced visibility/ceilings.

Examination of the helicopter revealed no evidence of any mechanical malfunctions or anomalies that would have precluded normal operation. Data from the helicopter's flight displays revealed that the helicopter's altimeter was set at 30.05 inches of mercury (inHg); The altimeter setting at the station nearest the accident site was 29.97 inHg. This difference would have resulted in the helicopter's altimeter indicating a higher altitude than the helicopter's actual altitude. The display's data also indicated the helicopter's flight path towards its destination airport. The flight display's last indicated altitude was 1,538 ft, which would have only provided marginal obstacle clearance.

Additionally, the helicopter terrain avoidance and warning system low altitude alerts were set to "inhibit", or turned off; therefore, the pilot would not have received a terrain warning message. Flight information from the displays did not record any evasive maneuvering, and it is likely that the pilot did not see the terrain before impact.

Autopsy and toxicology testing of the pilot did not reveal evidence of incapacitation. A review of the pilot's medical information indicated that he had been diagnosed with early cataracts; the pilot first reported cataracts to the FAA in 2005, and it is possible that they could have increased in severity enough to have compromised his night vision and contributed to his difficulty avoiding the hill. Additionally, the pilot's eyesight may not have adjusted to the night conditions after being exposed to bright lights during departure. However, the severity of his cataracts at the time of the accident is unknown, and whether visual limitations from cataracts or bright lights contributed to the accident, could not be determined.

The accident is consistent with control flight into terrain during dark night conditions

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The pilot's controlled flight into terrain during night visual meteorological conditions. Contributing to the accident was the pilot improper decision to inhibit the helicopter's terrain warning systems and flight at low altitude.


Altitude - Not attained/maintained (Cause)
Ground proximity system - Not used/operated (Factor)

Personnel issues
Lack of action - Pilot (Cause)
Decision making/judgment - Pilot (Factor)

Environmental issues
Dark - Effect on operation (Cause)
Mountainous/hilly terrain - Awareness of condition (Factor)
Mountainous/hilly terrain - Contributed to outcome (Factor)

Factual Information

History of Flight

Controlled flight into terr/obj (CFIT) (Defining event) 

On November 3, 2018, about 2347 central standard time, a Bell 206B helicopter, N417WT, was destroyed when it was involved in an accident near Uvalde, Texas. The pilot and two passengers were fatally injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. Night visual meteorological conditions prevailed at the time of the accident.

A review of data from the helicopter's primary and multifunction display units revealed that the helicopter departed a private ranch about 2341 and proceeded east toward San Antonio, Texas. The data showed that the helicopter reached an altitude of 1,900 ft before beginning a gradual descent, until the final barometric altitude of 1,538 ft (indicated altitude on the display) and 74 knots airspeed. The altimeter was set for a barometric pressure of 30.05 inHg. The data did not reveal any extreme changes in pitch, bank, or airspeed. The flight display also retained the last GPS altitude, which was 1,422 ft. Additionally, the terrain awareness warning system (TAWS) and helicopter TAWS low altitude alerts were set for 140 ft above ground level; however, terrain alerts were set to "inhibit."

Figure 1. Helicopter departure with flood lights shining on helicopter (Video screenshot from KSAT and Jason Martinez).

The Uvalde County Sheriff's Office was notified of a possible downed aircraft northwest of Uvalde, Texas. A search effort of authorities and local volunteers found the wreckage about daybreak the following morning.

The helicopter impacted the side of a hill about 5 miles east of the departure point and about 71 miles west of San Antonio International Airport. 

Pilot Information

Certificate: Airline Transport; Commercial
Age: 76, Male
Airplane Rating(s): Multi-engine Land; Single-engine Land
Seat Occupied:
Other Aircraft Rating(s): Helicopter
Restraint Used:
Instrument Rating(s): Airplane; Helicopter
Second Pilot Present: No
Instructor Rating(s): Helicopter; Instrument Helicopter
Toxicology Performed: Yes
Medical Certification: Class 2 With Waivers/Limitations
Last FAA Medical Exam: 03/26/2018
Occupational Pilot: Yes
Last Flight Review or Equivalent:
Flight Time:  (Estimated) 23400 hours (Total, all aircraft), 400 hours (Total, this make and model)

A review of previous aviation medical examinations noted a diagnosis of early cataracts; however, there was no additional information regarding the severity of the condition.

Aircraft and Owner/Operator Information

Aircraft Make: Bell
Registration: N417WT
Model/Series: 206 B
Aircraft Category: Helicopter
Year of Manufacture: 2005
Amateur Built: No
Airworthiness Certificate: Normal
Serial Number: 4591
Landing Gear Type: Skid
Date/Type of Last Inspection: 10/11/2018, AAIP
Certified Max Gross Wt.:
Time Since Last Inspection:  1953 Hours
Engines: 1 Turbo Shaft
Airframe Total Time:  as of last inspection
Engine Manufacturer: Rolls Royce
ELT:  C126 installed, activated, aided in locating accident
Engine Model/Series: 250-C20J
Registered Owner: W T Byler Co Inc
Rated Power:
Operator: W T Byler Co Inc
Operating Certificate(s) Held: None

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Night
Observation Facility, Elevation: KUVA
Distance from Accident Site: 13 Nautical Miles
Observation Time: 0515 UTC
Direction from Accident Site: 316°
Lowest Cloud Condition: Clear
Visibility:  10 Miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: 6 knots /
Turbulence Type Forecast/Actual:
Wind Direction: 30°
Turbulence Severity Forecast/Actual:
Altimeter Setting: 29.97 inches Hg
Temperature/Dew Point: 17°C / 16°C
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Private Ranch, TX
Type of Flight Plan Filed: None
Destination: San Antonio, TX (SAT)
Type of Clearance: None
Departure Time: 1145 CDT
Type of Airspace: 

A review of weather information about the time of the accident revealed a small area of cloud ceilings east of the departure point. This area of clouds dissipated and moved eastward over time. There was no indication of low-level wind shear or clear air turbulence.

There was no record of the pilot receiving a weather briefing before departure.

Moonrise occurred at 0343 and moonset at 1642 with about 19% disk illuminated. At the time of departure and the accident, the moon would have been below the horizon. 

Wreckage and Impact Information

Crew Injuries: 1 Fatal 
Aircraft Damage: Destroyed
Passenger Injuries: 2 Fatal
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 3 Fatal
Latitude, Longitude: 29.368056, -99.923889 (est) 

The helicopter impacted about 100 ft below the apex of a hill that measured about 1,500 ft mean sea level (see figure 2). A wreckage path about 75 to 100 yards long was distributed along the hillside leading to the main wreckage. There was no post-crash fire.

Figure 2. Wreckage at the accident site (Courtesy of FAA)

The hazardous terrain at the accident site precluded an on-scene examination of the helicopter; the wreckage was recovered to a secure facility for examination.

All major components of the helicopter were located at the accident site. The forward portion of the cabin/cockpit area was largely destroyed by impact. The tail boom remained attached to the fuselage but was twisted and damaged due to the impact. The fuel bladder remained in the fuselage and contained an undetermined quantity of fuel. The tail rotor gearbox was found several feet away from the tail boom. Both tail rotor blades were bent near the doubler but remained attached. The tail rotor was rotated by hand with no binding or anomalies noted with the tail rotor gearbox. Oil was present in the tail rotor gearbox. The tail rotor gearbox's magnetic chip detector was removed and no particles were observed.

The main rotor hub and blade assembly had separated from the main rotor mast below the main rotor hub. The main rotor mast exhibited a fracture consistent with mechanical overload. The two main rotor blades were fractured outboard of the doublers and located near the wreckage path.

Main rotor drivetrain continuity was established by rotating the input drive by hand and observing the rotation of the mast. No abnormalities were noted when the transmission was rotated by hand. The transmission chip detectors were removed and no particles were observed.

The components of the hydraulic system, including the hydraulic pump, sustained various degrees of impact damage. A small amount of hydraulic fluid was present in the hydraulic oil reservoir. The three servo actuators remained attached to the roof structure, and movement was noted when manipulated by hand. No preimpact abnormalities were noted with hydraulic system. Flight control continuity could not be established due to impact damage; however, no anomalies were noted with the collective, cyclic and anti-torque pedals.

No evidence of pre-impact abnormalities were noted during the airframe examination.

The engine was removed from the airframe and transported to an overhaul facility for a detailed examination. The engine was placed on a stand and disassembled. Continuity through the accessory section was established. Foreign object damage was noted to the leading edges of the intake compressor blades; also "metal spray" was noted on the turbine compressor wheel. The engine bleed valve and fuel nozzle were bench tested. The power turbine governor and fuel control units were sent to another facility and tested. No engine abnormalities were noted that would have restricted normal operation of the engine. 

Medical And Pathological Information

The Bexar County Medical Examiner's Office, San Antonio, Texas, conducted an autopsy on the pilot. The cause of death was determined to be "multiple blunt force injuries."

The FAA Forensic Sciences Laboratory conducted toxicological testing of the pilot. The specimens were not tested for cyanide and carbon monoxide. The test was negative for ethanol; desmethylsildenafil was detected in the muscle and liver. Desmethylsildenafil is an active metabolite of sildenafil, which is not considered to be impairing.

Bailee and Will shared an engagement photo from inside a helicopter after he proposed.


  1. Summary (direct quote): The accident is consistent with control flight into terrain during dark night conditions.

    Additional quote: The pilot's eyesight may not have adjusted to the night conditions after being exposed to bright lights during departure.

    The altimeter was not set properly, the offset would have been less than 75 feet, not enough that it should have made a difference especially at night when the pilot should have used extra margin.

  2. The low AGL flying altitude with terrain warning silenced raises the question of whether he intended to follow Hwy 55 into Uvalde and then proceed along the US-90 corridor for the rest of the flight.

    Was overflying that corner of hills beyond Hwy 55 with no development/lighting in dark night conditions planned, or a navigation error? If planned, why fly so low?

    Mapped point using NTSB crash coordinates:

  3. I flew around this area yesterday afternoon looking at some property. I must have flown right over the crash site. I got down to 2,200 MSL and was getting terrain warnings from my Garmin and from my passenger. This is no place to fly low in the dark. The hills abruptly end just a few hundred yards south of the crash site and it becomes a flat plain. Sad.

  4. I believe the grave error was allowing altitude to diminish by 400 feet. Very likely was inadvertent.

    Pilot established an initial altitude of 1,900. Given the altimeter error then the pilot intended to be at 2,000 MSL but really was at 1,900. So far they're still safe. But then altitude was allowed to diminish by 400 feet over the next few minutes and leading to impact.

    One lesson I take away from this is to build in additional altitude. Not expecting to allow 400 ft altitude excursions. But if one were to occur at least it would not be fatal.

    This crash is a real shame. Should have never occurred.

  5. Per statistics 101 and basic mathematical permutations, a high time pilot isn't safer than a student fresh out of a solo unless there is a continuous loop of incremental improvements from one flight to the next. How often do you practice stalls on a routine flight? or go for a few touch'n goes departing for a trip and spending 10-15 min extra doing it? or rehearse filling a VFR navlog by hand every so often? and always look to better the next landing?
    If not all you would have achieved after tens of thousands of hours of flying is bring some small probability of disaster that was always there all along to be the lucky draw after all those tries and it would be the lucky day for disaster, not you and your passengers...

    1. Per statistics, low time pilots have more accidents. A lot more accidents.

  6. Pilot was employee of the groom's family, it was the groom's family ranch and their helicopter. Byler's have a Houston business operation. This was not his first flight from the ranch back into nearby cities. Pilot flew for them 15 or 20 years, and Vietnam chopper experienced, too.

    Pilot certainly knew the terrain, made the trip back and forth for years. Nobody can say whether he intended to overfly the dark hills or take the road track. Distraction with the newlyweds in back or whatever, he did not crash due to unfamiliarity with the area or inexperience.