Silverton, CO, USA
N1539Q
CESSNA 150L
A witness saw the airplane flying low over mountainous terrain. He then saw the nose of airplane pull up, followed by the airplane flying inverted and departing controlled flight; the airplane's observed behavior is indicative of an aerodynamic stall. The airplane impacted rocky terrain at 12,570 feet mean sea level. The airplane was operating in excess of its maximum allowable gross weight. Further, the pilot was not using supplemental oxygen, despite a risk for hypoxia above 10,000 feet. The postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The pilot's autopsy indicated moderate to severe diffuse coronary artery disease. This elevated his risk for acute coronary syndrome or an acute arrhythmia followed by incapacitation but would have left no evidence at autopsy. Further, hypoxia would have increased the likelihood of an acute cardiac event. Additionally, the pilot had significant levels of multiple impairing medications at the time of the crash that would have affected his ability to operate the airplane. The pilot was very likely impaired by this combination of sedating medications, even at levels that were probably therapeutic. Further, the medications would have affected his decision-making ability, which may have played a role in his decision to fly at these altitudes without oxygen and above the airplane's maximum gross weight.
HISTORY OF FLIGHTOn July 14, 2011, about 0730 mountain daylight time, a Cessna 150L, N1539Q, was substantially damaged when it impacted mountainous terrain near Silverton, Colorado. The pilot and passenger were fatally injured. The airplane was registered to a private individual and was being operated by another private individual for the 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed and a flight plan had not been filed. The local flight had originated about 0645 from Animas Air Park (00C), Durango, Colorado. A witness about 4 miles to the southeast of the accident location reported the airplane just barely cleared the ridge when it flew directly over him at less than 100 feet above ground level (agl). The witness saw the airplane continue to the northwest and saw it circling when the airplane suddenly pulled nose up, appeared to go upside down, and disappeared from his view behind a ridge near the summit of the Stony Pass Trail. The witness proceeded to the accident location and discovered the wreckage where it had impacted near the summit. A family member of the pilot reported that the pilot was very familiar with the area around Stony Pass, since the family had been visiting the area since the 1970's and they thought he may have been scouting for a camping location in that area. They reported that although he was an experienced pilot, most of his flight time was logged at much lower elevations, and he was not very experienced at mountain flying. The family member also reported that the pilot had no fear at all about flying the small single engine airplane over the mountains even at night. He had no fear about flying very low in the mountains and he liked to fly below the tops of the ridges at about 500 feet from the ground. PERSONNEL INFORMATIONThe 62-year old pilot held a private pilot certificate for airplane single engine land which was initially issued by the Federal Aviation Administration (FAA) on September 27, 1998. He did not hold and instrument rating. The pilot's most recent third class medical certificate was issued by the FAA on February 5, 2010, with the limitation "must have available glasses for near vision." The pilot's logbook was not available for examination. A review of documents found in the wreckage included a flight review document dated February 16, 2010, where the pilot noted that he had logged 1,500 hours of flight experience, with 758 hours of flight experience in the accident airplane make and model. On his medical certificate application, dated February 5, 2010, he noted that he had logged a total of 4,125 hours of flight experience, with 60 of those hours in the previous six months. AIRCRAFT INFORMATIONThe two-seat, high-wing, fixed gear airplane, serial number (s/n) 15072839, was manufactured in 1971. It was powered by a 150-horsepower Lycoming O-320-E2D engine, s/n RL-19365-27A, which drove a 2-blade McCauley metal alloy, fixed-pitch propeller. The airplane had been modified with a short takeoff and landing (STOL) kit manufactured by Horton STOL-Craft, Inc., which was installed under FAA Supplemental Type Certificate Number SA909CE. Current aircraft maintenance logbooks were not available for examination. However, based on the tachometer reading at the accident scene, documents that were found in the wreckage, and other information, the most recent annual inspection was estimated to have been completed on July 2, 2011, at a tachometer time and engine total time of 827 hours. The airframe total time is unknown, but was estimated from the same documents to be about 4,000 hours. METEOROLOGICAL INFORMATIONThe closest official weather observation station was Telluride Regional Airport (TEX), Telluride, Colorado, located 17 nautical miles west of the accident site. The elevation of the weather observation station was 9,070 feet mean sea level (msl). At 0735 the automated weather observing system at TEX reported wind from 120 degrees at 3 knots, visibility of 10 miles, clear of clouds, temperature 13 degrees C, dew point 4 degrees C, with an altimeter setting of 30.31 inches of Mercury. Data from the U. S. Naval Observatory showed that the beginning of civil twilight occurred at 0529, and sunrise occurred at 0600. AIRPORT INFORMATIONThe two-seat, high-wing, fixed gear airplane, serial number (s/n) 15072839, was manufactured in 1971. It was powered by a 150-horsepower Lycoming O-320-E2D engine, s/n RL-19365-27A, which drove a 2-blade McCauley metal alloy, fixed-pitch propeller. The airplane had been modified with a short takeoff and landing (STOL) kit manufactured by Horton STOL-Craft, Inc., which was installed under FAA Supplemental Type Certificate Number SA909CE. Current aircraft maintenance logbooks were not available for examination. However, based on the tachometer reading at the accident scene, documents that were found in the wreckage, and other information, the most recent annual inspection was estimated to have been completed on July 2, 2011, at a tachometer time and engine total time of 827 hours. The airframe total time is unknown, but was estimated from the same documents to be about 4,000 hours. WRECKAGE AND IMPACT INFORMATIONThe wreckage was examined by the investigator-in-charge (IIC) at the accident location. The airplane had impacted rocky, mountainous terrain at an elevation of 12,570 feet msl, about 90' below the summit near a four-wheel drive trail. The wreckage path began at the initial impact ground scar and continued on a direction of 220 degrees. The aircraft came to rest inverted 38 feet from the initial impact point with the fuselage oriented on a heading of about 55 degrees. The tail cone was partially separated at the aft cabin bulkhead. There was evidence of fuel in the fuel tanks, fuel pumps, fuel lines and the fuel strainer. The propeller blades displayed obvious impact damage on the leading edges, and the separated crankshaft and crankshaft flange displayed evidence of torsional overstress fracture with no evidence of fatigue stress. There was evidence that the pilot had been wearing his lap belt. There was evidence that the passenger had not been wearing her lap belt, and there was evidence that both occupant had not been using their shoulder harnesses at the time of impact. No provisions for use of supplemental oxygen were observed in the wreckage. The postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. ADDITIONAL INFORMATIONThe FAA's Aeronautical Information Manual, Chapter 8, contains the following instructions regarding fitness for flight: "CAUTION- The CFRs prohibit a pilot who possesses a current medical certificate from performing crewmember duties while the pilot has a known medical condition or increase of a known medical condition that would make the pilot unable to meet the standards for the medical certificate." In addition: pilots are prohibited from "performing crewmember duties while using any medication that affects the faculties in any way contrary to safety." The FAA's Aeronautical Information Manual, Chapter 8, contains the following instructions on hypoxia and the relevant altitudes: "From 12,000 to 15,000 feet of altitude, judgment, memory, alertness, coordination and ability to make calculations are impaired, and headache, drowsiness, dizziness and either a sense of well-being (euphoria) or belligerence occur." In addition, "Small amounts of alcohol and low doses of certain drugs, such as antihistamines, tranquilizers, sedatives and analgesics can, through their depressant action, render the brain much more susceptible to hypoxia." … "Hypoxia is prevented by heeding factors that reduce tolerance to altitude, by enriching the inspired air with oxygen from an appropriate oxygen system … for optimum protection, pilots are encouraged to use supplemental oxygen above 10,000 feet during the day, and above 5,000 feet at night." The requirements of 49 Code of Federal Regulations 61.53 state that "a person … shall not act as pilot in command … while that person: knows or has reason to know of any medical condition that would make the person unable to meet the requirements for the medical certificate necessary for the pilot operation; or is taking medication or receiving other treatment for a medical condition that results in the person being unable to meet the requirements for the medical certificate necessary for the pilot operation". The requirements of 49 Code of Federal Regulations 91.211 (a) (1) state that: "No person may operate a civil aircraft of U.S. registry … at cabin pressure altitudes above 12,500 feet (MSL) … unless the required minimum flight crew uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration". The FAA's Mountain Flying Pamphlet, FAA-P-8740-60, recommends that pilots should "cross a ridge or pass at the ridge elevation plus at least 1,000 feet." Based on witness statements, the records of refueling, the tachometer time when the airplane departed, and the tachometer time at the accident scene, the IIC estimated the airplane departed from 00C about 0645, estimated the accident occurred about 0730, and estimated the fuel remaining on-board at the time of the accident was about 19 gallons. Driver license records show the pilot weighed 165 pounds and the passenger weighed 118 pounds. Weight and balance records showed the accident airplane had an empty weight of 1,254.2 pounds. The weight of the airplane at the time of take-off from 00C, with an estimated 25 gallons of fuel, was estimated by the IIC to be 1,687 pounds. Based on the pilot's fuel consumption records of previous flights the IIC estimated the fuel remaining in the airplane at the time of the accident was about 19 gallons of fuel. The IIC estimated the weight of the airplane at the time of the accident to be about 1,651 pounds. The maximum gross weight limitation for the Cessna 150L was listed in the FAA Type Certificate Data Sheet as 1,600 pounds. COMMUNICATIONSNo record of any communications with the accident airplane was found for the day of the accident. MEDICAL AND PATHOLOGICAL INFORMATIONAn autopsy was performed on the pilot by a forensic pathologist in Durango, Colorado, as authorized by the Coroner of San Juan County, Colorado. The cause of death was listed as multiple fractures and internal injuries due to blunt trauma. Forensic toxicology was performed on specimens from the pilot by the FAA, Aeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma. The toxicology report stated: NO CARBON MONOXIDE detected in Blood (Cavity); NO CYANIDE detected in Blood (Cavity); NO ETHANOL detected in Vitreous. The following additional findings were noted: 171 (ug/ml, ug/g) Acetaminophen detected in Urine Amlodipine detected in Blood (Cavity) Amlodipine detected in Urine Atenolol detected in Blood (Cavity) Atenolol detected in Urine 6.793 (ug/mL, ug/g) Carisoprodol detected in Blood (Cavity) Carisoprodol detected in Urine 0.727 (ug/mL, ug/g) Dihydrocodeine detected in Urine 0.047 (ug/mL, ug/g) Dihydrocodeine detected in Blood (Cavity) 0.372 (ug/ml, ug/g) Hydrocodone detected in Blood (Cavity) 8.412 (ug/ml, ug/g) Hydrocodone detected in Urine Hydromorphone NOT detected in Blood (Cavity) 3.605 (ug/mL, ug/g) Hydromorphone detected in Urine Meprobamate detected in Urine 7.271 (ug/ml, ug/g) Meprobamate detected in Blood (Cavity) The National Transportation Safety Board (NTSB) Chief Medical Officer reviewed the IIC's narrative, the autopsy report, the toxicology results, the pilot's FAA airman medical certification file, and the pilot's personal medical records. The pilot was granted his first medical certificate without limitation in 1995. In 2001, his third class medical certificate was limited by the need to wear corrective lenses. In 2004, he reported having had a LASIK procedure. On his most recent FAA medical exam, on February 5, 2010, he reported taking medications for the first time: Tylenol (acetaminophen), aspirin (salicylic acid), and Advil (ibuprofen); all over-the-counter pain relievers. He did not report any other significant medical conditions or any prescription medications to the FAA. The pathologist identified natural disease in the heart on the autopsy. The heart weight was at the upper limit of normal for a man of this pilot's height at 370 grams (normal heart weight is 330 ± 40 grams). In addition, there were areas of stenoses in the in the left anterior descending, circumflex, and marginal coronary arteries varying from 70 to 90 percent, and stenosis in the right main no greater than 70 percent. Toxicology testing revealed acetaminophen, amlodipine, atenolol, carisoprodol, hydrocodone and its metabolites hydromorphone and dihydrocodeine, and meprobamate in urine. Amlodipine and atenolol were found in cavity blood (these are two blood pressure medications marketed under the trade names Norvasc and Tenormin respectively). Also found in cavity blood was 6.793 ug/ml of carisoprodol (a controlled substance used to treat musculoskeletal pain and marketed under the trade name Soma), 0.372 ug/ml of hydrocodone (a narcotic pain medication prescribed as a controlled substance and marketed under the trade names Vicodin, Lorcet, and Norco), 0.047 ug/ml of dihydrocodeine (hydrocodone's primary metabolite), and 7.271 ug/ml of meprobamate (an anxiolytic prescribed as a controlled substance and only approved for short term use by the Food and Drug Administration (FDA), marketed under the trade name Miltown). Prescription bottles containing some of these medications were recovered by investigators from the personal effects in the pilot's hotel room. Personal medical records from 1996 to April 6, 2011, reveal a diagnosis of chronic low back pain. Since at least 1996 this condition was being routinely treated with Lortab (hydrocodone and acetaminophen) and Soma (carisoprodol). In addition, by the last year of his life the pilot had been diagnosed with hypertension, primary hyperaldosteronism, high cholesterol, intermittent depression, and borderline diabetes. According to the notes from the last visit with the physician, the pilot was being treated with amlodipine, atenolol, spironolactone for his hypertension and hyperaldosteronism, aspirin as a preventative for heart disease, and the Lortab and Soma for his chronic back pain. No mention was made in the medical records of meprobamate. TESTS AND RESEARCHThe airplane was equipped with an Insight Avionics GEM 602 engine monitor which was examined at the NTSB vehicle recorder division in Washington, D.C. The engine monitor is capable of providing the crew with exhaust gas and cylinder head temperatures from each of the engine cylinders. The instrument can display, depending on the installation and engine type, up to 13 engine temperatures in a bar graph or digital display, however it does not retain any engine data during operations. No data was recovered from the GEM 602 unit.
The pilot's failure to maintain control of the airplane while operating it at low levels above mountainous terrain and in excess of its maximum allowable gross weight, which resulted in an aerodynamic stall. The pilot's failure to maintain control resulted from an acute cardiac event and incapacitation, hypoxia, or the effects of sedating medications or a combination of these factors. Contributing to the accident was the pilot's improper decision to takeoff above gross weight and without oxygen for the flight in mountainous terrain.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
