Parker, CO, USA
N152RB
EBERLE JOHN S FOKKER DR-1 TRIPLANE
The pilot departed the airport, made a left turn to the east, and climbed to an altitude of 6,700 feet mean sea level (msl) at a groundspeed of about 93 knots. About 5 minutes after departing the airport, the airplane initiated a left descending turn and disappeared off radar. Two witnesses who lived near the accident site heard the airplane approach. One witness said the engine sounded normal. As they went outside to see the airplane, the witnesses saw the airplane go over their house at a low altitude, and one witness went to the back of the house to continue to watch the airplane. After he got to the back of his house, the witness saw the airplane in a tight left descending spiral in about a 45-degree nose-down pitch angle. A postaccident examination of the airplane did not reveal any preimpact anomalies that would have precluded normal operations. A review of weather conditions at the time of the accident revealed that the density altitude was about 8,250 feet. The elevation at the accident site was 6,170 feet msl. The high density altitude would have reduced the airplane’s climb performance by about 67 percent, which could explain the airplane’s reduced climb performance. When the pilot was interviewed 7 months after the accident occurred, he said he could not recall anything that occurred on the day of the accident. However, it is likely that the airplane stalled as a result of reduced airspeed and climb performance while operating at a high density altitude.
HISTORY OF FLIGHT On August 26, 2012, about 0946 Mountain Daylight Time, a Eberle Fokker DR.1, tri-plane, Experimental Amateur-Built airplane, N152RB, owned by a private individual and operated by an Airline Transport Pilot, was substantially damaged when it departed controlled flight and impacted terrain two miles northeast of Parker, Colorado. The pilot, the sole person on board the airplane was seriously injured. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight being operated under the provisions of 14 Code of Federal Regulation Part 91. The cross-country flight originated at Centennial Airport (APA), Englewood, Colorado, about 0941 MDT, and was en route to the Platt Valley Airpark, Fort Lupton, Colorado. Centennial Airport Air Traffic Control Tower recordings indicated that at 0937:49, the pilot requested and received taxi clearance to runway 17L. At 0940:14, the pilot received clearance for takeoff on runway 17L and an eastbound departure. At 0942:41, Federal Aviation Administration, Denver Terminal Air Traffic Control Center radar showed the airplane’s 1200 transponder code track parallel to and slightly east of APA runway 17L at 6,200 feet msl. The field elevation at APA was 5,885 feet msl. The airplane made a left turn to an approximate heading of 095 degrees and proceeded on an easterly heading at a groundspeed of about 93 knots. The radar data showed the airplane make a gradual climb to 6,700 feet. At 0946:10, the radar track and altitude showed the airplane initiate a descending left turn. At 0946:18, the radar track stopped over the location where the airplane impacted the ground. The airplane was at 6,400 feet when the radar track stopped. At 0946:31, the target disappeared from radar. The terrain elevation at the accident site was 6,170 feet msl. A witness who lived in a house at the end of a cul-de-sac near the accident site, heard the airplane heading toward their house. He said that he and his wife went outside to see the airplane just as it was going over. The airplane was traveling west to east and was “probably a couple of hundred feet up”. He said the airplane was yawing to the left as it went over. The witness lost sight of the airplane and went around the house to see the airplane. As he got around the garage, he saw the airplane in a left spiral; about 45 degrees nose down, descending toward the ground. The witness said he lost sight of the airplane when he turned to tell his wife to call 9-1-1. The witness then grabbed a fire extinguisher and went to the accident scene. He said that when the fire and rescue persons arrived, he observed a fire fighter move the airplane’s throttle back to idle and turn off all of the switches in what was left of the airplane’s cockpit. The wife said that she was in the house when her and husband heard the airplane approach from the west. She said it sounded like it was low to the ground. They went outside to see it. She could hear the airplane’s engine. It sounded normal. She said that when she saw the airplane go over her house, it appeared as if it were being pushed to the south. When she went back inside the house to call 9-1-1, she said she could see the airplane on the ground in the distance. The pilot was interviewed on March 4, 2013, following seven months of healing and physical therapy. The pilot could not recall any of the events of that day and said that the first thing he did remember after the accident was waking up in the hospital. AIRCRAFT INFORMATION The airplane was a full-scale replica of a World War I, German Fokker DR.1 tri-plane. It was painted red and affixed with insignia so as to resemble the airplane flown and made famous by the German ace fighter pilot, Baron Manfred Von Richtofen, also known in history as the Red Baron. The owner normally had the airplane on static display with other World War I replica airplanes at the Vintage Aero Flying Museum on the Platt Valley Airpark. The single-seat, three wing airplane, serial number 20936, was manufactured in 1978 and had an airworthiness certificate classifying it in the experimental amateur-built category. The airplane was powered by one Lycoming IO-360-B4D fuel-injected engine rated at 180 horsepower at 2,800 rpm. The airplane's tachometer read 638.38 hours at the accident site. A maintenance status board in a hanger at the Platt Valley Airport showed the airplane was due its next condition inspection on October 1, 2012. The status board also showed its next oil change was due at 650 hours. PERSONNEL INFORMATION The pilot, age 60, held an Airline Transport Pilot certificate with single-engine land, multi-engine land, single-engine sea, and instrument ratings. According to the pilot's FAA medical records, on January 25, 2012, he reported having 19,650 total flying hours, and reported having flown 75 hours in the six months prior to the examination. According to the airplane’s owner, the pilot had about 150 total hours in the accident airplane. The pilot held a second class medical certificate dated January 25, 2012. The certificate showed a restriction, [the] Holder shall possess glasses with correcting lenses for near vision while exercising the privileges of his airman certificate. The pilot was given an NTSB Form 6120.1 Pilot/Operator Aircraft Accident/Incident Report to complete. However, it was not returned, and not pursued because of the distress the pilot showed when interviewed about the accident. METEOROLOGICAL INFORMATION At 0954, the Routine Aviation Weather Report for APA, about 5 miles west of the accident site, was wind 250 degrees at 7 knots, clear skies, 10 miles visibility, temperature 77 degrees Fahrenheit (F), dew point 44 degrees F, and altimeter 30.21 inches of Mercury. WRECKAGE AND IMPACT INFORMATION The National Transportation Safety Board on scene investigation began at 1200 MDT. The accident site was located at the top of a knoll in a rolling cow pasture approximately 1,500 feet east of a cul-de-sac in a rural residential area about two miles northeast of the downtown area of Parker. The accident scene consisted of the airplane main wreckage to include the engine, propeller, cockpit, fuselage, top, middle, and bottom wings, main landing gear, empennage, and tail wheel. The airplane rested upright and was oriented on a 135-degree heading. A three foot long, eight inch wide and 10 inch deep impact crater was located beneath the airplane's engine and propeller. Broken pieces of the airplane's forward fuselage, and the three faux redial engine cylinders were located in and around the crater. About 30 inches aft of the impact crater was an I-shaped impression in the ground which was consistent with the leading edge of the main landing gear foil and axle, and the two main gear tires. The airplane's ring cowling was broken circumferentially at the attachment screws. It was located about three feet in front of the airplane and impact crater. The front of the cowling was split around the opening for the engine crankshaft. The top front of the cowling was crushed and chipped. The airplane's two blade propeller showed one blade undamaged and the other blade bent aft about 45 degrees at the hub and bent forward about 30 degrees 18 inches from the blade tip. The bent blade showed leading edge polishing along the blade span. The airplane's engine was bent downward and pushed aft. The firewall was bent aft and upward. The fuel tank was crushed upward and broken. It was punctured at the bottom. The smell of fuel was prevalent in and around the fuel tank and beneath the airplane. The cowling and forward fuselage around the engine was broken down and fragmented. The cockpit floor was crushed upward. The seat, lapbelt and shoulder harnesses were intact. The cockpit walls were bent and broken outward and down. The instrument panel was broken forward and fragmented. The windshield with the faux machine guns was broken aft. The top wing was broken at mid-span. The left top wing was broken down and aft. The left aileron was intact. The push-pull tube running from the mixer was broken at the fuselage just forward of the cockpit. The right aileron was also intact and its push-pull tube was also broken at the fuselage forward of the cockpit. Flight control continuity to both ailerons was confirmed. The left middle wing was broken downward at the wing root. The outboard strut was broken outward and aft. The left bottom wing was broken upward at the wing root. The outboard three feet of the left bottom wing was broken upward. The outboard wing strut between the bottom and middle wing was broken aft. The right middle wing was broken downward. The outboard strut was broken downward and aft. The right bottom wing was intact. The outboard strut between it and the middle wing was broken down and aft. The main landing gear struts we're bent aft and crushed upward. The airfoil covering the wheels' axle was crushed upward and aft. Both main wheel rims, spokes, and caps we're bent aft. The tires remained intact. The fuselage aft of the cockpit was broken down and twisted 10 degrees counter clockwise. The empennage and tail wheel showed no damage. Control continuity from the control stick to the elevator and the rudder pedals to the rudder was confirmed. The airplane wreckage was retained for further examination. TESTS AND RESEARCH The airplane was examined at Fort Lupton, Colorado on September 4, 2012. The fuel selector was positioned on. The fuel boost pump was removed and powered up and worked normally. The engine driven fuel pump was removed, examined and worked normally. Fuel was found in the fuel line to the pump. The fuel screen was removed and examined. It was wet with fuel and clean. The throttle body was removed and examined. Continuity from the throttle and mixture controls was confirmed. Fuel was present in the throttle body and the lines into the unit. The magnetos were removed and examined. Both magnetos showed spark at all of the leads. The fuel distribution manifold was opened and showed fuel. Fuel was found in the manifold and the fuel lines to the cylinders. The oil screen was removed and examined. The oil in the screen and drained from the engine crankcase was clean and flowed freely. Some small pieces of metal consistent with aluminum were found in the screen. The engine's top spark plugs and rocker box covers were removed and the crankshaft was turned to determine continuity and compression. The crankshaft turned freely. All pistons moved properly. The camshaft, push rods, rockers and valves moved properly. Good compression was confirmed. No anomalies were found that would have precluded the engine from producing normal rated power. Fuel Testing At APA, an on-airport service company using an avgas truck put seven gallons in the accident airplane and 75 gallons in a Mullicoupe that the pilot was going to fly to Fort Lupton later that day. A Beech Staggerwing was also refueled from the vehicle that provided fuel to the Fokker DR.1, receiving 18 gallons. Fuel samples were taken from the vehicle, the Staggerwing, and the Mullicoupe, and were sent to a fuel testing laboratory in Denver, Colorado, for testing and examination. The tests were conducted on October 9, 2012. The results of the tests indicated that all fuel samples were 100 low lead aviation gasoline, were free of particulates and contaminants, and would combust normally as designed. Airplane Performance Another pilot who flies World War I replica airplanes to include the Fokker DR.1 tri-plane, and had flown the accident airplane said that the DR.1 was designed to be unstable to be highly maneuverable as a military fighter airplane. He said the airplane was very pitch sensitive, that the ailerons were okay, and that the rudder was pretty powerful. He did not know what the maximum lift to drag ratio for the airplane was. He said he tried to figure it once and said it was probably somewhere around five-to-one (five feet forward for every one foot down). He said performance-wise, the 180 horsepower Lycoming engine could get 1,000 foot-per-minute rate-of-climb at sea level with it, in the airplane. The airplane has a very steep descent angle during approach for landing. He said they don’t use airspeed as much as flying attitude on approach because you have to be looking outside of the airplane most of the time, but he figured that on approach, the airplane was flying at 70 to 75 miles per hour. He said at the higher elevation, that speed was probably a couple of miles per hour higher. Because of the drag the airplane produces, it slows fast when transitioning from the descent to the flare for landing. The airplane “probably” touches down around 50 to 55 miles per hour. The airplane climbs at about 65 miles per hour and cruises about 105 miles per hour. The replica airplane pilot said if you lost an engine, you’d have to push the nose over quite a bit to get your airspeed back. He said you would be surprised how much of a push forward it is to get the nose down. The replica airplanes do stalls and acrobatics. The airplane gives a good stall warning before it stalls. He said that he wouldn’t let it wrap up into a spin. With the small rudder the airplane has, you’d have to get the nose pointed down quick. The replica airplane pilot said he had flown the accident airplane at least three or four times, both at or near sea level and at the Platte Valley Airport in Ft. Lupton, Colorado. He said that the airplane performed noticeably different at 5,000 feet msl versus sea level. Density Altitude Based on the weather conditions and pressure altitude at APA at the time of the accident, the density altitude in the area would have been about 8,250 feet. FAA Pamphlet FAA-P-8740-2 (2008) Density Altitude defines density altitude as pressure altitude corrected for non-standard temperature variations. Density altitude is an indicator of aircraft performance. As density altitude increases, air density decreases resulting in decreased aircraft performance. According to the Koch chart, based on the conditions at the time of the accident, the takeoff distance required to get airborne would have been 150 percent of the normal takeoff distance added to the normal takeoff distance, and the airplane’s rate of climb would have been decreased by 67 percent.
The pilot's loss of control of the airplane due to the airplane’s reduced climb performance during high density altitude operations.
Source: NTSB Aviation Accident Database
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