Sisters, OR, USA
N66HL
LEAGUE LANCAIR IV-TP
The purpose of the flight was for the flight instructor to conduct a flight review of the private pilot in his high-performance, experimental, amateur-built airplane. On-board data recovered from the airplane indicate that after departure, the airplane maneuvered for about 25 minutes before making a series of turns while gradually climbing. After reaching the highest altitude attained during the flight, the airplane began to descend and continued in an increasingly tightening right turn, creating a hook-type shape at the end of the radar track. This hook occurred over 15 seconds, with the airplane's pitch dropping from level to -68 degrees. This coincided with a vertical speed change from about -300 ft per minute (fpm) to a peak of -22,000 fpm, and a g-load increase to 7G, while the indicated airspeed peaked about 310 kts. The airplane broke apart in flight and the wreckage debris was scattered over an estimated 1,600-ft area of flat terrain. The instructor was experienced in the airplane and had flown with the private pilot before. The private pilot did not hold a current medical, although he always flew with an instructor onboard. The private pilot built the airplane about 4.5 years before the accident. The autopsy reports for both pilots revealed that the cause of death was blunt force trauma and no medical events likely occurred while in flight. A performance study of the airplane's flight revealed that the accident sequence only required about 79 percent of the available lift from the wing until well after the descent was established; consequently, the sequence was unlikely to have been precipitated by an aerodynamic stall. A postaccident examination of the airframe and engine revealed no evidence of a preimpact mechanical malfunction or failure that would have precluded normal operation. Flight control system continuity could not be confirmed due to the extensive damage incurred during the inflight break up. Accordingly, the reason for the steepening spiral dive, with increasing roll angle and speed, could not be established. Twenty-six percent of Lancair airplanes have been involved in accidents, and 19 percent have been involved in fatal accidents. In 2008 and 2012, the FAA convened two safety groups specifically to address the airplane's "unusually high accident and fatality rate compared to other amateur-built aircraft." The study noted that based on the statistics, the kit was involved in fatal accidents at "a rate that is disproportionate to their fleet size." As a result of studies developed by these safety groups, the FAA acknowledged that accidents would continue to occur if no action was taken. Thus, the FAA issued a notice that Lancair pilots should "review and thoroughly understand all information regarding stall characteristics and obtain specialized training regarding slow flight handling characteristics, stall recognition, and stall recovery techniques;" install an angle-of-attack indicator to better predict a stall; and have their airplane evaluated by an experienced type-specific mechanic to ensure proper rigging, wing alignment, and weight and balance. The notice was recalled shortly after its release and another notice was released later to include other high-performance experimental amateur-built aircraft.
HISTORY OF FLIGHT On April 23, 2012, at 1017 Pacific daylight time, an experimental League Lancair IV-TP, N66HL, departed controlled flight and broke up inflight 5 nautical miles (nm) southeast of Sisters, Oregon. The private pilot and his certified flight instructor (CFI) received fatal injuries, and the airplane, which was owned and operated by the pilot, sustained substantial damage. The local 14 Code of Federal Regulations Part 91 instructional flight, which departed Roberts Field, Redmond, Oregon, about 0950, was being operated in visual meteorological conditions. No flight plan had been filed. The purpose of the flight was for the CFI to conduct a flight review of the private pilot in his high-performance, experimental, amateur-built airplane. Flight track data recorded from the airplane's global positioning system (GPS) was extracted from the onboard Chelton multi-functional display (MFD) compact flash memory card that was recovered from the wreckage. The flight data file started at time 0948:34 and the data was captured at 1-second intervals. The data spanned from 0948:34 to 1017:20, or 28 minutes and 46 seconds. A review of the data revealed that the airplane started at Roberts Field and followed a flight path consistent with a departure from runway 10. The plot continued in that direction for about 2 nm and then reversed course temporarily heading northwest while gradually increasing in altitude from the airport's elevation of about 3,050 feet (ft) mean sea level (msl) to about 10,500 ft msl. Starting about 1008:30, the airplane made several shallow banks heading southwest, then northwest, and then south and began a 7 nm southwest stretch all while maintaining an altitude of about 10,500 ft msl. A review of the remaining data disclosed that at 1015:20, the airplane was at 10,455 ft msl and began a right turn. The turn continued and the airplane's track completed a 360-degree circular pattern with a diameter of about 2.8 nm over the span of about 1 minute and 30 seconds. While in the turn, the airplane initially descended to about 10,250 ft msl at 1015:42 and then began to climb 1,350 ft over the course of 1 minute to about 11,600 ft msl. Thereafter, the airplane climbed to its highest altitude of about 11,720 ft msl at 1016:47 and then began to descend as the right turn tightened, creating a "hook" type shape as its end (about 0.4 nm in diameter). This hook encompassed the last hits of the flight track and occurred over 15 seconds, during which the airplane's altitude decreased over 3,900 ft to a recorded altitude of 6,715 ft msl. The last altitude recorded was 6,445 ft., at time 1717:13. Starting at about 1716:40 (33 seconds before the end of the data), the pitch angle dropped steadily, from 9 degrees nose-up to 68 degrees nose-down at the end of the data. Simultaneously, the vertical speed dropped from a 2,000 feet per minute (fpm) climb to a 22,000 ft per minute (fpm) descent, the g-load increased to 7gs, and the indicated airspeed (KIAS) increased to about 310 kts. PERSONNEL INFORMATION Certified Flight Instructor A review of the airmen records maintained by the Federal Aviation Administration (FAA) disclosed that the CFI, age 52, held a CFI and airline transport pilot certificate with airplane ratings for single-engine and multi-engine land, as well as instrument flight. His most recent second-class medical certificate was issued on February 22, 2012. The pilot had a history of severe obstructive sleep apnea treated with a Continuous Positive Airway Pressure (CPAP) device while sleeping, which he had reported to the FAA. A National Transportation Safety Board (NTSB) investigator reviewed the CFI's personal flight logbooks. According to the logbooks, his total flight experience was 11,098.4 hours, with 5,320.2 in turbine-engine airplanes. There were entries in the logbook that indicated he had flown the accident airplane about 18 hours, all of which he logged as a CFI. The last flight recorded in the log was noted as taking place on April 14, 2012 in the accident airplane, totaling 2.5 hours flying from Redmond to Madras, Oregon to Bend, Oregon and back to Redmond. The first-pilot's weight was estimated to be about 220 pounds (lbs). According to the CFI's spouse, he was having no problems sleeping and would regularly get between 7 to 9 hours of sleep. He never received any surgical treatment for the sleep apnea. She additionally reported that the CFI was in good health and took no medication. He had characterized the pilot-owner as being a "very meticulous guy especially with his airplane." He stated that he had not flown a Lancair that was better maintained than the accident airplane. Pilot-Owner According to the FAA airmen records, the pilot-owner age 68, held a private pilot certificate with an airplane rating for single-engine land (acquired in 1997), as well as a complex and instrument rating (acquired in 1998). His most recent second-class medical certificate was issued as a limited medical certificate on May 05, 1997. The pilot additionally held a repairman experimental aircraft builder certificate and built the airplane. According to his friends , the pilot did not hold a current medical because of health issues, and therefore always flew with flight instructors familiar with Lancairs. All of these CFIs were approved on the pilot's insurance policy. The pilot owner's logbooks indicated he had amassed about 785 hours total time, of which 217 was accrued in high-performance turbine airplanes. The last flight was recorded as occurring on February 27, 2012 where he flew 1.7 hours as pilot in command logging 0.2 of that as occurring in actual instrument conditions. The pilot-owner's weight was estimated to be 210 lbs. AIRCRAFT INFORMATION The Lancair IV-TP is an amateur-built experimental airplane constructed mainly of composite materials. The high-performance, pressurized airplane is equipped with four seats, retractable tricycle landing gear, and traditional flight control surfaces. The accident airplane received a special airworthiness certificate in the experimental category for the purpose of being operated as an amateur-built aircraft in October 2008. The equipment on the airplane was a standard Lancair installation for an IV-TP and part of a quick-build where the pilot completed the construction in a facility that specializes in helping builders with their kit projects. The airplane was equipped with a Walter/General Electric M601E-11A engine, serial number (s/n) 071007, and, according to the manufacturer, is rated at 751 shaft horse power (SHP). It had a constant-speed three-bladed Avia Propeller V508/E/84/B2 (s/n 910663007), that was manufactured in 2004; the blades were 84 inches (in) in length. The airplane's test flight hours were completed in September 2009. Thereafter, the logbooks indicated that the pilot estimated that the airplane's stalling speed in the landing configuration (Vso), at a weight of 3,750 lbs and a CG of 137 inches aft of datum, was 61 knots. Maintenance Records The airplane's maintenance records were reviewed by a NTSB investigator. According to the records, the airplane, serial number LIV-578, had accumulated a total time in service of about 463 hours at the time of the last recorded maintenance on April 4, 2012. During that inspection, it was noted that the engine oil was changed, the fuel filter was replaced and the fuel control unit (FCU) was bled. A review of the airplane's documents further revealed that the engine was manufactured in 2007 and as of March 14, 2012, had amassed 457.2 hours and 339 cycles. Fuel Quantity Based on Chelton data, the airplane had a recorded total fuel quantity of 138 gallons (gals) at the time of startup, including 57 gals in the left and right wings (114 gals total). The last recorded data point indicated 52 gals in the right tank and 45 gals in the left tank, with a total quantity of 119 gals. Weight and Balance NTSB investigators estimated the airplane's gross take-off weight (GTOW) and center of gravity. The GTOW was estimated to be 3,934.4 lbs, with a center of gravity (CG) at 138.5 in aft of datum. The weight at the time of the accident was estimated to be 3,628 lbs, based on the GTOW and the recorded fuel burn. The weight and balance record in the airplane indicated that the maximum allowable takeoff gross weight was 3,800 lbs, and the allowable CG range was from 132 to 144 in aft of datum. A sheet detailing the weight and balance computations is appended to this report. The Lancair-recommended maximum GTOW for a Lancair IV-TP with the turboprop engine and winglets was 3,550 lbs. FAA regulations governing amateur-built aircraft identify the builder as the manufacturer of that individual aircraft and, as such, the builder is allowed to set the weight limits, including maximum GTOW, at any desired value. Because each aircraft is unique in its construction, the builder must determine the stall speeds for that particular aircraft. Documents relating to the stall speeds specific for the occurrence aircraft were found during the investigation and are presented later in this report. Performance Study An NTSB engineer used the Chelton MFD data and a simulation of the Lancair IV-TP to compute additional performance information about the flight. In the simulation, the airplane's flight controls were manipulated so as to approximately match the recorded GPS track and MFD altitude data. These calculations are described in a memorandum contained in the public docket for this accident. The simulations used a simple model of the Lancair IV-TP (flaps in the retracted position), a weight of 3,628 lbs (the estimated GTOW less the recorded fuel flow during the flight), and the weather conditions recorded at the time of the accident. The engine power in the simulation was based on recorded propeller speed (Np) and engine torque (Q) data. Lancair was not able to provide any usable aerodynamic or performance data with which to construct a simulator model; consequently, the simulator model used in the performance study was based on theoretical aerodynamic relationships grounded in classical aerodynamics and the airplane's geometry; a report of flight tests from 2009 in the accident airplane; estimated stall speeds provided by the Transportation Safety Board of Canada (TSB); estimates of angle of attack, lift, and drag based on the recorded MFD data from the accident flight; and comparisons with other aircraft. The objectives of the simulation were to: -obtain a "match" of the recorded MFD GPS positions using the recorded pitch and roll information and engine power. -verify the self-consistency of the recorded data by comparing the MFD data to self-consistent simulation data. -provide estimates of performance parameters that were not recorded on the MFD. -quantify the lift coefficient (CL) required to fly the final maneuver recorded by the MFD and determine its proximity to CLmax (the value of CL at stall). The simulation was able to generate a reasonably good match of the recorded motion of the airplane. Furthermore, the highest CL achieved in the simulation was about 1.03. The CLmax (at flaps up) implied by the stall speeds obtained during flight tests of the airplane was about 1.30, suggesting that the accident maneuver only required about 79 percent of the available lift from the wing, and consequently did not involve a stall. Instead, the maneuver described by the MFD and simulation is a steepening spiral dive, with increasing roll angle, speeds, and normal load factor (nlf), with nlf reaching about 7 G's and the calibrated airspeed reaching 310 knots at the end of the recorded data. Pilot's Operating Handbook (POH) A Pilot Operating Handbook (POH) for an exemplar Lancair IV-TP, provided by Lancair contained stall speeds, from which an estimate of CLmax was made. In a table titled "Aircraft Operating Speeds," the POH listed the following: -Stall Speed Clean (Vs)=69 KCAS -Stall Speed landing configuration (Vso)=61 KCAS The table did not indicate the airplane weight associated with these stall speeds, but the stall speeds published in the POHs of small general aviation aircraft generally correspond to the maximum gross weight of the airplane. The exemplar POH stated that the maximum takeoff weight was 3,200 lb.; assuming that the published stall speeds corresponded to this weight, the resulting CLmax is 2.03 at flaps up, and 2.59 at flaps down. These values are high compared to the flight test results from the accident airplane, the calculation of the former engineer with Lancair, and the CLmax values of other small general aviation airplanes. The POH for the exemplar Lancair IV-TP contains the following information in the "Emergency Procedures" section (p. III-7): -The best glide speed tested to date is 120 IAS (indicated airspeed), 1,570 FPM (feet per minute) resulting in a 7.7:1 glide ratio. -Glide distance is approximately 0.75 nm per 1,000 feet of altitude loss, however this may vary significantly. It is suggested that it be established for your individual aircraft. 1,570 ft./min. at 120 kts. IAS is indeed a 7.7:1 glide ratio. However, a 7.7:1 glide ratio results in a forward distance of 7,700 ft. (1.27 nm) for every 1,000 ft. of altitude loss, so the statement in the POH that the "glide distance is approximately 0.75 NM per 1000 feet of altitude loss" is inconsistent with the 7.7:1 glide ratio information provided in the preceding sentence. 0.75 NM forward travel for 1,000 ft. altitude loss is a glide ratio of about 4.6:1, considerably below the 7.7:1 figure. It is noteworthy that the "Emergency Procedures" section of this exemplar airplane POH contains conflicting glide performance information, with no way to determine which data, if any, are correct. METEOROLOGICAL INFORMATION The conditions over Oregon at 10,000 feet indicated the following conditions: south-southwest winds near 30 kts, a temperature of 3 degrees Celsius, with a 2 degrees temperature-dew point spread in Salem, Oregon, located approximately 80 miles northwest of the accident site. Roberts Field had an Automated Surface Observation System (ASOS) and reported the following conditions near the time of the accident: wind 090 degrees at 7 knots; visibility 10 statute miles (sm); cloud condition clear; temperature 21 degrees Celsius; dew point 07 degrees Celsius; altimeter setting 29.93 in of Mercury. A NTSB Weather Study was performed. The meteorologist reported that satellite data indicated that there was no thunderstorms or cumulonimbus activity over the accident site, and that visual meteorological conditions (VMC) prevailed. Water vapor imagery did not depict any significant moisture channel darkening typically associated with turbulence or mountain wave activity. No advisories were current for any organized areas of turbulence or icing conditions over the region. COMMUNICATIONS The Redmond Air Traffic Control (ATC) Facility provided the recorded radio communications between the pilot and controllers. The airplane was cleared to make a left downwind departure for runway 10 and made no further radio communications until the time of the accident. The Redmond local control frequency recorded a series of transmissions that came from an unknown source at that time. The first transmission did not contain any eligible words, and the verbal transmission sounded like a grunt. A transmission followed seconds later that sounded distant, as if a person in the background was speaking. Only one word was slightly discernible, and was an expletive. Another transmission was heard after a second, but no words were transmitted. WRECKAGE AND IMPACT INFORMATION NTSB investigators did not travel to the accident site, the information contained in the section was gathered from parties to the investigation, the FAA, and local law enforcement. The accident site was located in flat unpopulated terrain, about 5 nautical miles (nm) southeast of Sisters. The main wreckage was located at an estimated 44 degrees 13.107 minutes north latitude and 121 degrees 30.547 minutes west longitude, at an elevation of about 3,400 feet mean sea level (msl). The distance from Redmond (departure city)
The pilots’ inability to maintain control of the airplane and arrest a steep spiral dive while maneuvering for reasons that could not be determined because postaccident examination could not identify any anomalies that would have precluded normal operation prior to the inflight breakup.
Source: NTSB Aviation Accident Database
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