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On August 8, 2010, about 0958 Pacific daylight time, a HOAC-Austria (now Diamond) HK-36R Super Dimona motorglider, N40440, serial number 36388, was substantially damaged when it impacted a building at Bend Municipal Airport (BDN), Bend, Oregon. The pilot/owner received fatal injuries. The flight was operated under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight.
According to several witnesses, the airplane departed from runway 16, gained a small amount of altitude, and then turned to the left, in an apparent effort to fly the traffic pattern and return for landing. One witness reported that the airplane never reached an altitude higher than approximately 50 feet, and another saw the left wing "dip down" shortly before the impact. The airplane struck an unoccupied factory building situated near the southeast corner of the airport. It came to rest on the ground upright, outside the building, and adjacent to a south-facing wall. The canopy was shattered, but the pilot remained in the cockpit. There was no fire.
According to Federal Aviation Administration (FAA) information, the pilot held a private pilot certificate with airplane singe engine land, single engine sea, multiengine land, and instrument ratings. His most recent FAA third-class medical certificate was issued in June 2009. He reported 5,000 hours of total flight experience on that medical application. Multiple attempts to obtain the pilot's flight records via family members and acquaintances were unsuccessful.
The Oregon State Police Medical Examiner Division autopsy report indicated that the cause of death was "blunt force injuries." The FAA Civil Aeromedical Institute conducted forensic toxicology examinations on specimens from the pilot, and reported that no carbon monoxide, cyanide, ethanol, or any screened drugs were detected.
FAA records indicated that in 2004, the pilot experienced a runway excursion in the accident airplane while landing at Camarillo Airport (CMA), Camarillo, California. He was not injured, and the airplane was not damaged during that event.
The airplane was a powered sailplane that was manufactured in 1993, and was registered to the pilot in 2001. The airplane was of Austrian design and origin, and was equipped with a Rotax 912 A2 80 hp engine, and a wood propeller that could be fully feathered in flight. It was not approved for night or instrument flight, and aerobatics were prohibited.
The airplane was primarily of glass fiber composite construction, with standard three-axis flight controls operated by cables and push-pull tubes. Each wing was equipped with a dive brake, and the horizontal stabilizer was mounted atop the vertical stabilizer. Landing gear was fixed, conventional arrangement. Seating was two-place side by side. A single-piece canopy hinged at the aft end permitted cockpit ingress and egress.
The MT brand two-blade, variable pitch propeller was electronically controlled and electrically driven. For soaring purposes, the propeller could be fully feathered in flight. The manufacturer's FAA approved flight manual (FM) stated that 60 seconds was required to drive the blades from full-feather to start position, or vice versa.
A 21.1 total (20.9 usable) gallon aluminum fuel tank was located behind the two seats. The "Limitations" section of the FM stated that the airplane was approved to use "aviation grade 100LL, MOGAS leaded min. octane rating: 96 ROZ, [and] Automotive Super, unleaded, min. octane rating: 95 ROZ" fuels. A placard next to the fuel filler port contained the same information.
According to BDN operations personnel, the pilot based the airplane at BDN. He kept it in a hangar along with a Rockwell Aero Commander 690 that was also registered to him. A search of the hangar did not locate any logbooks for the pilot or maintenance records for the accident airplane. Multiple attempts to obtain the airplane's maintenance records via family members and acquaintances were unsuccessful.
The 0955 automated weather observation at BDN included winds of 3 knots from 260 degrees; clear skies; temperature 19 degrees C; dew point 9 degrees C; and an altimeter setting of 30.00 inches of mercury.
FAA information indicated that the BDN elevation was 3,640 feet above mean sea level. The airport was equipped with a single paved runway, designated 16/34, that measured 5,200 by 75 feet. The traffic pattern was designated as left. A full-length parallel taxiway was located on the west side of the runway. The owner's hangar was situated on the east side of the airport, about 1,500 feet east of the runway. The taxiway from his hangar intersected the runway about 1,800 feet north of the threshold of runway 34, and 3,400 feet south of the threshold of runway 16.
The terrain south of the airport consisted of several relatively flat fields with tall grass and interspersed with some trees, and bounded by more trees, buildings, and powerlines.
The airport was not equipped with an air traffic control tower. There was no record of any communications to or from the airplane on the morning of the accident.
WRECKAGE AND IMPACT INFORMATION
The airplane struck and came to rest against an unused factory building on airport property. The wreckage was located about 1,200 feet east, and 200 feet north, of the threshold of runway 34. The building was about 25 feet high, with a slightly sloped roof. The lower 8 feet of the exterior walls was unpainted concrete, while the upper 17 feet consisted of sheet metal panels painted dark red. Most of the area adjacent to the building near the impact site was paved with asphalt.
The first impact mark was on a south-facing wall at an outside southwest-facing corner of the building, and consisted of crush damage to a rain gutter downspout and the underlying sheet metal. The crush line was about 8 feet above ground level (agl), and was aligned about 30 degrees above the horizontal (from east-to-west). Corresponding fracture lines and impact signatures, including red paint transfer, were located about the midspan point of the right wing leading edge. Linear, white transfer marks about 15 feet long, and consistent with glass-fiber composite material abraded against the asphalt, extended from the vicinity of the outside corner towards the main wreckage. The airplane was situated against a second south-facing wall located about 50 feet north of the first wall that was impacted. The second wall was damaged over its full height in the vicinity of the wreckage. About 5 linear, evenly-spaced striations of white and red material were present on the asphalt just aft of where the nose of the airplane came to rest.
The fuselage was intact. The single piece T-configuration horizontal stabilizer was separated from, and lying just aft of, the vertical stabilizer. Both wings were significantly damaged. The left wing was split and twisted back inboard over the fuselage.
The engine remained attached to its mount, the mount remained attached to the fuselage, and the propeller blades and hub remained attached to the engine. Both propeller blades were missing their outboard halves; the ends were severely splintered, and multiple blade fragments were located in the immediate area. The fuel tank was intact, and the cap remained in place. The attachment status and condition of the fuel line(s) was not determined, but fuel was observed on the ground after the accident.
The fuel selector valve was found in its on position; the propeller pitch control was set to about 2,500 rpm; and the propeller mode switch was set to AUTO. The cockpit pitch trim control was set to the full airplane nose-up position. The light and fuel pump switches were found in their down (off) positions. The Mode master switch was found in the "Power Flight" position. The propeller control circuit breaker was found in the out/activated position; the circuit was disabled in that breaker position.
The Deschutes County Sheriff Office (DCSO) report stated that the first person on the scene, a private citizen, turned off the ignition and the "gas/fuel line." However, in a subsequent NTSB interview, that individual stated that he turned off the ignition and retarded the throttle, but did not alter any other control positions. Evaluation of photographs taken by DCSO personnel indicated that the fuel pump and light switches were in their up (on) positions shortly after the accident.
The wreckage was recovered and transported to a secure facility, where it was examined in detail about 2 months after the accident.
The canopy was securely latched, but the transparency was heavily fragmented, and separated from the canopy frame.
Examination of the flight control system did not reveal evidence of any pre-existing mechanical conditions or failures that would have precluded normal operation. The two cockpit control sticks were attached to a common linkage and moved in unison. With the exception of impact-related fractures, the roll control system was continuous from the two cockpit control sticks to both ailerons, and no components were missing. Continuity was also determined for the pitch and yaw control systems. The pitch trim system was determined to be operable through its full range.
Red paint transfer marks were present on the leading edge of the right wing, the lower skin of the left wing, the upper left side of the vertical stabilizer and rudder, and the underside of the elevator.
The single strap that retained the welded aluminum fuel tank was fracture-separated. The bottom surface of tank exhibited deformation in the "down" direction, consistent with hydraulic deformation. The fuel quantity sensing unit was installed and intact. The sensing unit was removed and the tank was observed to contain only a trace amount (wetness/odor) of fuel. No tank breaches were observed.
Both propeller blades were set to a similar pitch value, which was consistent with a takeoff setting. Both blades exhibited damage consistent with powered rotation at the time of impact. Aside from some intake and exhaust system crush and displacement damage, the engine was essentially intact. Only minor anomalies were noted during the examination; no evidence of any pre-existing mechanical conditions or failures that would have precluded normal operation was detected. According to the Diamond Aircraft Airworthiness limitations, the maximum (depending on Service Bulletins accomplished) recommended engine overhaul interval was 1,200 hours or 10 years, whichever came first. Based on the carburetor flanges found on the engine, which were a mandatory replacement item at overhaul, the engine did not appear to have been overhauled.
Using an external battery and fuel supply, the engine was started and test run to about 1,200 rpm (propeller rpm), including several throttle sweeps. The engine was not run at a higher rpm due to safety/integrity concerns. No anomalies were noted, and no pre-existing mechanical problems were found that would have prevented the engine from producing full power during the accident flight.
Refer to the accident docket for additional information.
A 2-ring binder containing the airplane FM was found in the airplane; it was undamaged. Examination of photographs taken on-scene by the DCSO indicated that the FM was not stowed in the pilot's flight bag at the time of the accident, but its location for the flight could not be determined. Two pages (4-11 and 4-12) were missing from the FM, and two pages numbered 4-11 and 4-12 were found in the wreckage; those pages were damaged and stained from the accident, but their binder holes were intact, consistent with them being out of the binder during the accident. The two pages were from the "Normal Procedures" section of the FM. Page 4-11 contained steps 15 to 22 of the "Launch/engine starting, run up, taxying procedures" subsection. Page 4-12 contained steps 23 to 27 of that same subsection. It also contained steps 1 to 6 of the "Takeoff and climb" subsection.
Weight and Balance Information
The weight and balance of the accident flight was estimated using the last known airplane empty weight, the pilot's weight, the weight of the items on board, and a presumed full fuel load. The resulting values were a weight of 721 kilograms (kg) with a center of gravity (CG) of 409.75 millimeters (mm). Maximum certificated takeoff weight was 770 kg, and the allowable CG range was 318 mm to 430 mm.
Airplane Performance Information
The FM provided takeoff performance tables, which used headwind, pressure altitude, and ambient temperature as the input variables. The tables were predicated on the maximum certificated weighted of 770kg. Table output included two takeoff distances; "S1" was the takeoff ground roll, and "S2" was the takeoff distance to clear a 15 meter (49 feet) obstacle. Based on the ambient conditions, the resultant S1 value was approximately 1,000 feet, and the resultant S2 value was approximately 1,350 feet.
The FM stated that the best rate of climb speed was 57 knots, and the best angle of climb speed was 51 knots. The FM stated that at sea level, maximum gross weight, propeller speed 2,420 rpm, and 57 knots airspeed, a climb rate of 807 feet per minute (fpm) would result. That equates to a climb gradient of about 8 degrees, which is similar to other small general aviation airplane climb rates. No other climb performance data was provided in the FM, and therefore, the predicted climb performance for the existing conditions could not be determined.
The investigation could not determine where the pilot began the takeoff roll, particularly whether he used the full runway length or conducted an "intersection takeoff" due to his hangar location. There was no information to determine the actual maximum altitude that the airplane achieved.
The FM stated that maximum gross weight, the minimum rate of descent (propeller feathered) was 224 fpm at 51 knots, which equates to a gradient of about -2.4 degrees.
Airplane Flight Procedures
In addition to procedures typical for engine run-up on other piston-powered airplanes, the "Normal Procedures" section of the FM contained a "propeller check" which consisted of exercising the propeller pitch control knob and the propeller switch, and obtaining defined results and indications.
The takeoff procedure included the following steps:
- Electric Fuel Pump - ON
- Propeller Pitch Control Switch - AUTOMATIC
- Propeller RPM knob - maximum propeller speed
- Throttle - full, rpm not below 2,420
Although the run-up section specified that the carburetor heat functionality was to be checked, the FM as found did not contain any information regarding the use or prohibition of carburetor heat on takeoff and climbout.
The FM stated that the electric fuel pump was to be switched off once at an altitude greater than 330 feet above the ground.
The "engine failure during takeoff" subsection of the "Emergencies" section of the FM included the following steps:
- Fuel valve - check if OPEN
- Electric fuel pump - check if ON
- Choke - check if OFF
- Propeller speed control - maximum speed
- Ignition switch - BOTH
That subsection also stated that "If the troubles cannot be eliminated immediately, and the engine refuses to deliver enough power, a straight-in-landing must be performed under 80 m (260 ft) of altitude."
Temperature and dew point values for the approximate time and location of the accident indicated that the relative humidity was approximately 55 percent. When the intersection of the two temperature values was located on a chart that depicted carburetor ice envelopes, the point was in the region of the chart denoted as "Serious Icing (Glide Power)," approximately midway between the region denoted as "Icing (Glide and Cruise Power)," and the one denoted as "Serious Icing (Cruise Power)."
Airspeed Indicator and Tachometer Tests
The tachometer and airspeed indicator were removed from the wreckage and tested with NTSB oversight at the facilities of Mid-Continent Instruments, Los Angeles, California. The tests consisted of providing known inputs to the instruments, and recording both the input and indicated output values. Both instruments were found to be functional, but anomalies were observed.
The airspeed indicator needle occasionally got stuck at 30 knots when the input airspeed was reduced. That anomaly could be expected to be detected by a pilot operating the airplane.
The tachometer registered about 15 percent lower than the input values across the range of test speeds. That value differed significantly from the instrument panel placard which stated "Tachometer indicates 36 rpm too few." The manufacturer's Airplane Maintenance Manual (AMM) required that the tachometer be checked against a "calibrated tachometer" each time maintenance was performed on the airplane, and that a specific AMM checklist be completed and filed with the airplane maintenance records following that activity. No evidence of such a check or the required documentation was located during the investigation.
Propeller Control Circuit Breaker
The activated propeller control circuit breaker (ETA part number 2-5700-ID1-K10-DD, 3.5A) was sent to the NTSB Materials Laboratory in Washington, D.C., for evaluation and testing. Radiographic and electrical continuity analysis indicated that the breaker was mechanically intact, and completed or interrupted the electrical circuit when operated manually. Applications of electrical loads revealed that the breaker operated in accordance with the manufacturer's specifications. A representative of the breaker manufacturer stated that there were no known problems with that model breaker. Refer to the docket for additional information.
Propeller Speed Control Unit
The propeller speed control unit was removed from the airplane and sent to the MT Propeller facility in Deland, Florida, for evaluation. The unit was tested with an FAA inspector present, who provided the following synopsis:
"It was removed from the packaging and inspected for external damage, none noted. Its operation and condition was compared to a similar known operational unit in MT's shop, using a test hub, a 12-volt power supply, and a test harness. The actuation time, continuous operating load amperage, and indicator lights all operated within normal parameters, as compared to the known unit. This only verifies the controller operation, with a test hub. The actual operation on the aircraft involved could be affected by internal wear in the hub, gearbox, or actuating motor." Those items were not tested.
The airplane manufacturer had issued about 50 Service Bulletins on a variety of subjects for the accident airplane make and model. Since the maintenance records were not obtained for the investigation, the compliance record could only be approximated, based on examination of the wreckage. Relevant results were as follows:
Service Bulletin 36-36/1, "Use of Unleaded Fuel" - Compliance partially established based on placard and FM page revisions; compatibility of installed fuel hoses not established.
Service Bulletin 36-54, "Elevator Stop Bolts" - Not applicable by airplane serial number
Service Bulletin 36-72, "Aileron Control System" - Apparent compliance established based on adapters observed in aileron control rods.
Service Bulletin 36-73/1, "Carburetor Flange" - Not in compliance; superseded flanges observed on carburetors. This Diamond SB referenced Rotax Mandatory SB-914-019-R1, which was intended to prevent failure of the flange. No damage was observed on the installed flanges.
Service Bulletin 36-77, "Start Check Placard" - Not in Compliance; superseded placard still installed in airplane, superseding placard not installed. The superseding placard included one modified step and two additional steps. The modified step was changed from "Trim checked" to "Trim neutral." The new steps were "Carburetor heat OFF" and "Fuel pump ON."
Observed Maintenance Activity
Two different witnesses separately observed the pilot working on the airplane in the period before the accident. A hangar neighbor reported that about a week before the accident, the pilot had the engine cowl removed, and another individual appeared to be helping him. The neighbor did not have any additional information about that observation. About 2 days before the accident, a non-aviation individual observed the pilot working under "the tail" of the airplane, but he did not know what the pilot was doing. A small access panel is located on the underside of the fuselage, about 12 inches forward of the rudder. According to the airplane manufacturer's representative, and also the airplane maintenance manual (MM), removal of that panel is used to obtain access to portions of the rudder and tailwheel control systems. Access to the pitch control system at the aft end of the airplane is obtained by removal of the rudder.
The airplane was equipped with two external air vents to provide fresh air to the cockpit. One was situated on each side of the fuselage, and both were NACA-style low drag flush ducts. Each corresponding cockpit outlet was just forward of the right and left seat occupant's outboard knee, just below the instrument panel, and no screens or filters were present in either duct or outlet unit. An abandoned insect nest with honeycombed cells was found in the left inlet duct. No insects were present, and the nest was extracted and sent to a curator in the Division of Invertebrate Zoology at the American Museum of Natural History in New York for identification and evaluation. The curator provided the following information:
"First, it is certainly a nest of the paper wasp genus Polistes. The species cannot be determined: it is either aurifer de Saussure, or dominula (Christ). The former is a native species; the latter is introduced, first being reported from the West Coast in the 1990's but now quite common. The nest is young, in the sense of early in the colony cycle, because it contains no brood whatsoever. However, the nest is considerably weathered. August is also getting to be late in the season to initiate a new nest anyway, so I have to conclude that the nest was built before the accident. Because the nest was young, if there were any wasps present at the time of the accident, there were no more than 1-2, the foundress or co-foundresses. Neither of the species mentioned has a reputation for being particularly aggressive, indeed, if anything dominula is considered the opposite. Moreover, young nests are less likely to elicit an aggressive defense than nests with brood. But a startled foundress could well take off in alarmed flight, which does tend to alarm humans who observe it. That possibility cannot be ruled out based on this nest specimen."
Airplane Flying Handbook Guidance
Chapter 16, "Emergency Procedures" of the Airplane Flying handbook (AFH, FAA-H-8083) addressed multiple aspects of emergencies, and included several paragraphs regarding psychological hazards, precautionary landings, and turns back to the runway shortly after takeoff.
Abnormal situations and emergencies often present "psychological hazards," which the AFH stated "may interfere with a pilot’s ability to act promptly and properly when faced with an emergency." The AFH listed several factors that constituted these psychological hazards, including reluctance to accept the emergency situation, a desire to save the airplane, and undue concern about getting hurt. Regarding the second factor, the AFH included the following:
"The pilot who has been conditioned during training to expect to find a relatively safe landing area...may ignore all basic rules of airmanship to avoid a touchdown in terrain where airplane damage is unavoidable....The desire to save the airplane, regardless of the risks involved, may be influenced by two other factors: the pilot’s financial stake in the airplane and the certainty that an undamaged airplane implies no bodily harm. There are times, however, when a pilot should be more interested in sacrificing the airplane so that the occupants can safely walk away from it."
The AFH defined a precautionary landing as a premeditated landing, on or off an airport, when further flight is possible but inadvisable, and that the altitude available is one controlling factor in the successful accomplishment of an emergency landing.