Tuesday, September 18, 2012

Boeing B75N1, N4473N: Accident occurred July 03, 2011 in Wetmore, Colorado

Sidney Emmert

DENVER (AP) -- Federal aviation investigators say pilot error was the likely cause of a vintage-biplane crash that killed the pilot and injured a passenger in south-central Colorado last year. The National Transportation Safety Board's final report on the crash says the probable cause was the pilot's failure to maintain clearance from the ground while maneuvering at low altitude. The report was issued last week. The 1947 Boeing two-seater crashed on July 3, 2011, near Wetmore in the San Isabel National Forest about 110 miles south of Denver. The crash killed 50-year-old Sidney Emmert of Oklahoma City. His passenger, Robert Hamilton of Wetmore, was treated at a Colorado Springs hospital and released. 

NTSB Identification: CEN11FA444 
14 CFR Part 91: General Aviation
Accident occurred Sunday, July 03, 2011 in Wetmore, CO
Probable Cause Approval Date: 09/13/2012
Aircraft: BOEING B75N1, registration: N4473N
Injuries: 1 Fatal,1 Serious.

According to the passenger, the pilot was maneuvering the airplane at low altitude in mountainous terrain. The passenger reported that the pilot was flying the airplane “low and slow,” the airplane’s bank angle began to increase, and the airplane descended and collided with trees. A postimpact fire consumed a majority of the wreckage. An examination did not find any anomalies with the airframe or engine that would have precluded normal operation.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The pilot's failure to maintain clearance from terrain while maneuvering at low altitude.


 On July 3, 2011, approximately 1550 mountain daylight time, a Boeing B75N1, impacted terrain near Wetmore, Colorado. The commercial pilot was fatally injured and the pilot-rated passenger sustained minor injuries. The airplane was substantially damaged and a postimpact fire ensued. The airplane was registered to and operated by Quetzal Limited Partnership, Oklahoma City, Oklahoma, under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which operated without a flight plan. The local flight originated from the Fremont County Airport (1V6), Canon City, Colorado about 1515.

The pilot-rated passenger reported that after departing 1V6, the airplane was flown at low altitude around several locations before circling the passenger’s home. While flying west from the passenger’s home there was no communication between him and the pilot. The passenger said that the airplane got low and slow, and the airplane’s bank increased. He further reported that the airplane descended and collided with trees. The passenger found the pilot unresponsive and attempted to get the pilot out of the airplane. A fire began and the passenger retreated from the spreading fire. The passenger remarked that there were no changes in engine noise.


The pilot, age 50, held a commercial pilot certificate for airplane single engine land, single engine sea, and instrument airplane. He held a private pilot certificate for airplane multi-engine land. A third class medical certificate, without restrictions, was issued on October 14, 2009, at which time the pilot reported having accumulated 1,500 hours of total time, with 90 hours in the previous six months. The pilot’s logbook was not obtained during the investigation and it is unknown how many hours in make and model the pilot had logged. The pilot had acquired the accident airplane on October 13, 2009.


The tandem two-seat, tube and fabric, bi-wing airplane, serial number 75-1183, was manufactured in 1947. A 450 horsepower Pratt & Whitney R-985 engine drove a Hamilton Standard 2B20 constant speed propeller. The airplane was issued a standard aerobatic airworthiness certificate on August 19, 1992. The airplane was configured with dual pilot controls.


At 1331, an automated weather reporting facility at Pueblo, Colorado, located 28 nautical miles to the east of the accident, reported wind from 080 degrees at 23 knots gusting to 28 knots, visibility 10 miles, a clear sky, temperature 97 degrees Fahrenheit (F), dew point 26 F, and a barometric pressure of 30.01 inches of Mercury.


The first impact signatures were damaged trees located 40 to 60 feet east southeast of the accident site. Several downed branches displayed clean angular cuts. The wreckage was located on the northern face of a ravine. The airplane came to rest in an upright position on a 240 degrees magnetic heading. The main wreckage consisted of the propeller, engine, and fuselage frame. Both bi-wings were almost completely consumed. Flight control continuity was confirmed to the rudder and elevators surfaces, and cable continuity was established to the aileron attachments. The cockpit instruments were unreadable due to thermal damage. The pilot’s restraint belt buckle was found in the secured position. One blade of the two-bladed metal propeller was partially buried in the ground. The other blade displayed gouges, chord wise scratches, and was bent forward near mid-span. The throttle quadrant was thermally damaged with the throttle, mixture, and propeller pitch lever set about 1/3 open. The engine was impact and thermally damaged. There were no anomalies detected with the airframe or engine which would have precluded normal operation.


An autopsy was performed on the pilot on July 6, 2011, by the El Paso County Coroner as authorized by the Custer County Coroner. The manner of death was ruled an accident. The medical examiner noted the presence of smoke inhalation and a postmortem carboxyhemoglobin of 7 percent. The autopsy found no anatomic reason for the pilot’s incapacitation.

The FAA Civil Aerospace Medical Institute (CAMI), Oklahoma City, Oklahoma, performed forensic toxicology on specimens from the pilot. The toxicology report marked putrefaction “yes.” The specimens received were deemed unsuitable for carbon monoxide analysis. Tests for cyanide, ethanol, and drugs were negative.

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