Payson, AZ, USA
N62959
PIPER PA-31-350
The pilot began flying the twin piston-engine airplane model for the cargo airline about 11 months before the accident. Although he had since upgraded to one of the airline's twin-turboprop airplane models, due to the airline's logistical needs, the pilot was transferred back to the piston-engine model about 1 week before the accident. The flight originated at one of the airline's outlying destination airports and was planned to stop at an interim destination to the southwest before continuing to the airline's base as the final destination. The late afternoon departure meant that the flight would arrive at the interim destination about 10 minutes after sunset. That interim destination was situated in a sparsely populated geographic bowl just south of terrain that was significantly higher, and the ceilings there included multiple broken and overcast cloud layers near, or lower than, the surrounding terrain. Although not required by Federal Aviation Administration (FAA) regulations, the airline employed dedicated personnel who performed partial dispatch-like activities, such as providing relevant flight information, including weather, to the pilots. Before takeoff on the accident flight, the pilot conferred briefly with the dispatch personnel by telephone, and, with little discussion, they agreed that the flight would proceed under visual flight rules to the interim destination. Information available at the time indicated that the cloud cover almost certainly precluded access to the airport without an instrument approach; however, the airplane was not equipped to conduct the only available instrument approach procedure for that airport. Additionally, the pilot did not have in-flight access to any GPS or terrain mapping/database information to readily assist him in either locating the airport or remaining safely clear of the local terrain. Although the airplane was not being actively tracked or assisted by air traffic control (ATC) early in the flight, review of ground tracking radar data showed that the flight initially headed directly toward the interim destination but then began a series of turns, descents, and climbs. The airplane then disappeared from radar as the result of radar coverage floor limitations due to high terrain and radar antenna siting. The airplane reappeared on radar about 24 minutes after it disappeared and about 9 minutes after the FAA-defined beginning of night. Based on the flight track, it is likely that the pilot made a dedicated effort to access the airport, while concurrently remaining clear of the clouds and terrain, strictly by visual means. This task was made considerably more difficult and hazardous by attempting it in dusk conditions, and then darkness, instead of during daylight hours. About 15 minutes after the airplane reappeared on radar, when it was at an altitude of about 13,500 ft, the pilot contacted ATC and requested and was granted an instrument flight rules clearance to his final destination. About 3 minutes later, the controller cleared the flight to descend to 10,000 ft, and the airplane leveled off at that altitude about 6 minutes later. However, upon reaching 10,000 ft, the pilot requested a lower altitude to escape "heavy" up- and down-drafts, but the controller was unable to comply because the ATC minimum vectoring altitude was 9,700 ft in that region. About 1 minute later, radar contact was lost. Shortly thereafter, the airplane impacted terrain in a steep nose-down attitude in a near-vertical trajectory. Although examination of the wreckage did not reveal any preimpact mechanical deficiencies that would have prevented normal operation and continued flight, the extent of the damage precluded, except on a macro scale, any determination of the preimpact integrity or functionality of any systems, subsystems, or components, including the ice protection systems, autopilot, and nose baggage door. Analysis of the radar data indicated that the airplane was above 10,000 ft for at least 41 minutes (possibly in two discontinuous periods) and above 12,000 ft (in two discontinuous periods) for at least 18 minutes. Although the airplane was reportedly equipped with supplemental oxygen, the investigation was unable to verify either its presence or its use by the pilot. Lack of supplemental oxygen at those altitudes for those periods could have contributed to a decrease in the pilot's mental acuity and his ability to safely conduct the flight. Analysis of air mass data revealed that mountain-wave activity and up- and downdrafts with vertical velocities of about 1,000 ft per minute (fpm) were present near the accident site and that the largest and most rapid transitions from up- to down-drafts occurred near the accident site, which was also supported by the airplane's altitude data trace. The analysis also indicated that the last radar target from the airplane was located in a downdraft with a velocity of between 600 and 1,000 fpm. Other meteorological analysis indicated that the airplane encountered icing conditions, likely in the form of supercooled large droplets (SLD), several minutes before the accident. Aside from pilot reports from aircraft actually encountering SLD, no tools currently exist to detect airborne SLD. Further, the tools and processes to reliably forecast SLD do not exist. SLD is often associated with rapid ice accumulation, especially on portions of the airplane that are not served by ice protection systems. Airframe icing, whether due to accumulation rates or locations that exceed the airplane's deicing system capabilities, mechanical failure, or the pilot's failure to properly use the system, can impose significant adverse effects on airplane controllability and its ability to remain airborne. Because of the pilot's recent transition from the Beechcraft BE-99, in which the pitot heat was always operating during flight, he may have forgotten that the accident airplane's pitot heat procedures were different and that the pitot heat had to be manually activated when the airplane encountered the icing conditions. If the pitot heat is not operating in icing conditions, the airspeed information becomes unreliable and likely erroneous. Erroneous airspeed indications, particularly in night instrument meteorological conditions when the pilot has no outside references, could result in a loss of control. The investigation was unable to determine whether the pitot heat was operating during the final portion of the flight. The investigation was unable to determine whether the pilot used the autopilot during the last portion of the flight. If he was using the autopilot, it is possible that, at some point, he was forced to revert to flying the airplane manually due to the unit's inability and to a corresponding Pilot's Operating Handbook prohibition against using it to maintain altitude in the strong up- and downdrafts, which would increase the pilot's workload. Another possibility is that the autopilot was unable to maintain altitude, and, instead of disconnecting it, the pilot overpowered it via the control wheel. If that occurred and the pilot overrode the autopilot for more than 3 seconds, the pitch autotrim system would have activated in the direction opposite the pilot's input, and, when the pilot released the control wheel, the airplane could have been significantly out of trim, which could result in uncommanded pitch, altitude, and speed excursions and possible loss of control. Whether the pilot was hand-flying the airplane or was using the autopilot, the encounter with the strong up- and downdrafts and consequent altitude loss likely prompted the pilot to input corrective actions to regain the lost altitude, specifically increasing pitch and possibly power. Such corrections typically result in airspeed losses; those losses can sometimes be significant as a function of downdraft strength and the airplane's climb capability. If that capability is compromised by the added weight, drag, and other adverse aerodynamic effects of ice, aerodynamic stall and a loss of control could result. Radar tracking data and ATC communications revealed that another, similar-model airplane flew a very similar track about 6 minutes behind the accident airplane, except that that other airplane was at 12,000 ft not 10,000 ft. The 10,000-ft ATC-mandated altitude placed the accident airplane closer to the underlying high terrain and into the clouds with the icing conditions and the strong vertical air movements. In contrast, the pilot of the second airplane reported that he was in and out of the cloud tops and did not report any weather-induced difficulties. The accident pilot did not have any efficient in-flight means for accurately determining the airborne meteorological conditions ahead, and the ATC controller did not advise him of any adverse conditions. Therefore, the pilot did not have any objective or immediate reason to refuse the ATC-assigned altitude of 10,000 ft. Ideally, based on both the AIRMET and the ambient temperatures, the pilot should have been aware of the likelihood of icing once he descended into clouds. That, particularly combined with his previously expressed lack of confidence in the airplane's capability in icing conditions, could have prompted him to request either an interim stepdown altitude of 12,000 ft or an outright delay in a direct descent to 10,000 ft, but, for undetermined reasons, the pilot did not make any such request of ATC. Based on the available evidence, if the ATC controller had not descended the airplane to 10,000 ft when he did, either by delaying or by assigning an interim altitude of 12,000 ft, it is likely that the airplane would not have encountered the icing conditions and the strong up- and downdrafts. In addition, if the presence of SLD and/or strong up- and downdrafts had been known or explicitly forecast and then communicated to the pilot either via his weather briefing, his onboard equipment, or by ATC, it is likely that the pilot would have opted to avoid those phenomena to the maximum extent possible. The flight's encounter with airframe icing and strong up-and downdrafts placed the pilot and airplane in an environment that either exacerbated or directly caused a situation that resulted in the loss of airplane control.
HISTORY OF FLIGHTOn December 18, 2012, about 1825 mountain standard time, a Piper PA-31-350, N62959, was lost from Federal Aviation Administration (FAA) radio and radar contact about 10 miles southwest of Payson, Arizona, during an instrument flight rules (IFR) flight to Phoenix Sky Harbor Airport (PHX), Phoenix, Arizona. The wreckage was located the following day; the pilot had received fatal injuries and the airplane was substantially damaged. The flight was being operated as Ameriflight 3853 (AMF3853) as a cargo flight for United Parcel Service (UPS), and was conducted under the provisions of Title 14 Code of Federal Regulations Part 135. Instrument meteorological conditions prevailed in the vicinity at the time contact with the airplane was lost. According to information from representatives of the airline and UPS, the flight departed Holbrook Municipal Airport (P14), Holbrook, Arizona, about its scheduled time of 1700, with a scheduled arrival time of 1730 at Payson Airport (PAN), Payson. According to the driver of the UPS truck who was at PAN and was scheduled to meet the flight, he never saw or heard the airplane. The driver left PAN about 20 minutes after the flight was due. According to FAA air traffic control (ATC) information, the flight's first ATC contact was with Albuquerque air route traffic control center (designated ZAB) about 1812, when the airplane was at an altitude of about 13,500 feet; the pilot requested a clearance to PHX. The flight was assigned a discrete transponder code, radar identified, and cleared direct to PHX, with an altitude crossing restriction that necessitated a descent. Shortly after the airplane reached the assigned altitude, the pilot requested a lower altitude; his request was denied due to ATC minimum vectoring altitude limitations. Shortly thereafter, radio and radar contact was lost. Weather conditions in the area precluded an aerial search until the following day. About 0950 on December 19, 2012, the wreckage was located at the same approximate latitude/longitude as the last radar target associated with the airplane, at an approximate elevation of 7,000 feet. The accident site was located about 12.4 miles, on a true bearing of about 213 degrees, from PAN. PERSONNEL INFORMATIONAccording to FAA information, the 28-year-old pilot held a commercial pilot certificate with airplane single- and multi-engine land, and instrument airplane ratings, as well as a flight instructor certificate with the same ratings. His most recent FAA first-class medical certificate was issued in August 2012. The pilot was an employee of Ameriflight. According to information provided by the airline, the pilot had a total flight experience of about 1,908 hours, including about 346 hours in the accident airplane make and model. His most recent flight review was completed in September 2012, in the BE-99 airplane. According to an airline representative, as of March 4, 2011 (which was prior to the pilot's employment by Ameriflight), the pilot had accumulated 1.4 actual and 84.4 simulated instrument hours. The airline did not track its pilots' actual or simulated instrument time, and the accident pilot's logbooks were not located, so no determination of his current instrument experience was able to be made. The pilot was hired by the airline in January 2012, and was initially assigned to the PA-31 airplane. In September 2012, he completed training for, and was assigned to, the BE-99 twin turboprop airplane. About a week before the accident, due to the airline's logistical requirements for the holiday season, the pilot was transferred back to the PA-31 airplane. When he became aware of that transfer, he told his father that he had received "some really bad news," and informed his father of the transfer back to the PA-31. The pilot told his father that the BE-99 is a "better" airplane, and that he did not "like or trust" the ice protection equipment on the PA-31. The pilot flew the PA-31 a total of about 11 hours between his transfer and the accident. Ameriflight pilots, dispatchers, and managers had very similar opinions about the pilot. In interviews or communications with multiple individuals, they consistently reported that the pilot was a quiet individual who did well in training, was competent, and did not cause or voice any problems with the airline. AIRCRAFT INFORMATIONFAA information indicated that the airplane was manufactured in 1976, and was registered to UAS Transervices Inc. of Pasadena, CA. It was equipped with two Lycoming TIO-540 series engines, and two three-blade Hartzell propellers. The left engine rotated clockwise, and the right engine rotated counter-clockwise, as viewed from the rear. The tricycle-style landing gear was retractable. Review of Ameriflight-provided information indicated that the airplane was within its weight and balance limits, and that there was sufficient fuel onboard for the planned flight legs. Maintenance records information indicated that the airplane had about 19,200 hours total time in service, and had accumulated about 23,400 flight cycles. The left engine had accumulated about 1,300 hours since its most recent overhaul, and the right engine had accumulated about 59 hours since its most recent overhaul. Review of the maintenance records did not reveal any significant items or trends. The airplane had several unscheduled maintenance items related to the ice protection systems accomplished in April and May 2012. In September 2012, some de-ice boot patches were replaced, and in October 2012 a pneumatic pump was replaced. No records of any subsequent discrepancies associated with the ice protection systems were located, nor were any records of any uncorrected maintenance items located. According to airline representatives, the airplane was equipped with VOR (very high frequency omni-range) and glide slope equipment for navigation. The airplane was not equipped with weather radar, or any system to receive and display ground-based weather radar information. The airplane was not equipped with a GPS receiver, and no evidence to suggest that the pilot had any personal or hand-held GPS units was obtained. The airplane was equipped with a Century Altimatic IIIC autopilot, which was capable of controlling aircraft in the roll, pitch, heading, and altitude hold modes. The Ameriflight Standard Operating Procedures (SOP), General Operations Manual (GOM), and the applicable Limitations section of the PA-31 Pilots Operating Handbook/Airplane Flight Manual (POH/AFM) did not contain any information regarding autopilot usage in turbulence or icing conditions. The autopilot did not have any automatic disconnect capability, but could be readily deactivated by the pilot. A "CAUTION" in the PA-31 POH/AFM stated "Do not overpower Autopilot pitch axis for periods longer than 3 seconds because the Autotrim System will operate in a direction to oppose the pilot and will, thereby, cause an increase in the pitch overpower forces." In addition, Paragraph 3.15 (Rough Air Operation) of Section 3(Emergency Procedures) of the PA-31 POH/AFM stated that "when flying in extreme turbulence or strong vertical currents and using the autopilot, the altitude-hold mode should not be used." The airplane was approved for flight into light to moderate icing when equipped with wing and empennage deicing boots, electric propeller deicers, electrically heated windshield, and an ice detection light. Ameriflight representatives and guidance indicated that the airplane was equipped with all four systems. The airplane was not equipped with the manufacturer-supplied supplemental oxygen system. Ameriflight representatives and guidance indicated that the airplane was equipped with a portable supplemental oxygen system. In May 2008, the FAA published a SAFO (Safety Alert for Operators notice) that advised pilots and operators about unexpected in-flight openings of PA-31 nose baggage doors. The SAFO reported that such occurrences "could adversely affect the flight characteristics of the airplane." The SAFO contained a reference to an FAA supplement delineating FAA-recommended actions regarding the doors and door opening events. That supplement was primarily focused on actions to prevent inadvertent door openings. Although the supplement also stated that the "operator's pilot training program should include emergency procedures training on how to react" and "what to expect [including]...handling," the FAA did not include any specific information, guidance, or references regarding those aspects. The FAA did not, either during airplane certification or after issuance of the SAFO, require the airplane manufacturer to develop or provide any such information. The reasons for the incongruity between the FAA recommendation for such information and training, and the lack of any FAA follow-up to ensure the development and promulgation of the same, could not be determined. In November 2008, Piper published mandatory Service Bulletin 1194A, which required certain nose baggage door inspections, and placed life limits on certain nose baggage door components. Effective July 2009, FAA Airworthiness Directive (AD) 2009-13-06 mandated compliance with Piper Service Bulletin (SB) 1194A. Ameriflight representatives indicated that the airplane was in compliance with the SB and AD. According to airline representatives, the airline "incorporated the recommendations of SAFO 08013 [in] the summer of 2008." The airline's response included references to the mechanical and inspection aspects of the supplement. The airline subsequently clarified that it "adopted [SAFO] recommendations 1-4," and correctly noted that it "could not locate any flight procedures" in the FAA or Piper guidance. METEOROLOGICAL INFORMATIONPAN Automated Weather Observations The 1615 automated weather observation at PAN included winds from 180 degrees at 7 knots, visibility 10 miles, broken cloud layers at 2,800 and 3,000 feet above ground level (agl), temperature 6 degrees C, dew point 2 degrees C, and an altimeter setting of 29.82 inches of mercury. The 1635 observation was similar, but with a broken cloud layer at 3,000 feet agl, and an overcast layer at 5,000 feet agl. The 1655 observation, which was about 5 minutes before the flight's departure from P14, was similar, with broken cloud layers at 2,700 and 3,400 feet agl, and an overcast layer at 4,400 feet agl. The 1715 observation, which was about 15 to 20 minutes prior to the flight's estimated arrival at PAN, was similar, with broken cloud layers at 3,100 and 3,500 feet agl, an overcast layer at 4,200 feet agl, and an altimeter setting of 29.80 inches of mercury. By 1735, which was about the flight's initial estimated arrival time into PAN, the observation included similar conditions, but with scattered clouds at 2,600 feet agl, and an overcast layer at 3,300 feet agl. Weather Forecasts The National Weather Service (NWS) area forecast for the flight and accident region, issued at 1345, called for an overcast ceiling at 7,000 feet, with tops at FL180, visibilities between 3 and 5 miles, and mist. After 1700 the forecast called for scattered light snow showers, mist, and visibilities around 3 miles. Sierra, Tango, and Zulu AIRMETs issued between 1345 and 1419, and valid for the flight and accident region for the period of the flight, warned of IFR conditions with ceilings below 1,000 feet, and visibility below 3 miles in precipitation and mist, mountains obscured by precipitation and clouds, moderate turbulence below 14,000 feet, and moderate icing between 7,000 feet and FL250. Review of observed meteorological data indicated that all of those conditions were present at the accident site at the time of the accident. No SIGMET, Center Weather Service Unit (CWSU) Advisory, or CWSU Meteorological Impact Statements were active for the flight and accident region for the period of the flight. No PIREPs for severe icing or severe turbulence were received by ATC. Supercooled liquid water droplets (SLD) is the term for the airborne phenomenon of liquid precipitation at or below freezing temperatures, and SLD can become freezing drizzle or freezing rain when it strikes a suitably cold surface, such as the ground or an aircraft. For any official NWS weather products, a weather forecaster would only issue a weather product that contained the terms "freezing drizzle" or "freezing rain" for the surface forecast; such forecasts are indicative of SLD aloft. By design, AIRMETs will include forecasts for moderate icing if applicable, but will not include either the type of icing expected, or any SLD prognoses. Some National Weather Service products do provide SLD and other icing information, but those products remain "supplemental," meaning that they are not automatically included in any official aviation weather briefings, and must be specifically sought or requested by the persons or agencies obtaining the briefing. None of the forecasts or AIRMETs applicable to the flight contained any references to freezing drizzle, freezing rain, or SLD. Sunset occurred at 1719, and civil twilight ended at 1746 at PAN. The moon was a waxing crescent of 35 percent, and was at its peak elevation at 1724. Weather Observations and Weather Models The NWS 1700 Surface Analysis Chart depicted a cold front from southern Nevada southward off the west coast of Mexico, and a stationary front from southern Nevada eastward into central Colorado. The station models around the accident site depicted air temperatures between about 0 and 8 degrees C, with temperature-dew point spreads of 10 degrees C or less, a southwest to south wind between 10 and 20 knots, cloudy skies, and light rain and/or light snow. The NWS 1700 Constant Pressure Charts depicted a mid-level trough just to the west of the accident site, with southwest to west-southwest winds above the accident site increasing from 30 to 80 knots. The accident site was located in the region of an upper-level jet streak that is typically conducive to precipitation, and vertical motion in clouds. Upper air data indicated that the freezing level was located at an altitude of about 7,400 feet. Rime and mixed icing was likely in a cloud layer between 8,000 and 13,000 feet. Low-level wind shear was indicated from the surface through 9,000 feet, with several layers of possible clear-air turbulence from the surface through 30,000 feet. Infrared data from the Geostationary Operational Environmental 15 (GOES-15) Satellite indicated an abundance of cloud cover over and around the accident site at the accident time, with approximate cloud-top heights of about 26,000 feet. Sounding data and data from the Weather Surveillance Radar-1988, Doppler (WSR-88D) indicated that SLD was likely at the flight's altitude at the time of the accident, and that it was likely that AMF3853 encountered the SLD several minutes before the accident time. Although several PIREPs of light to moderate icing for central Arizona were issued prior the accident, none reported SLD conditions. The standard format for PIREPS specifies only the "type and intensity" of icing. In contrast, while SLD can result in icing, it is neither a type nor intensity of icing. SLD is a meteorological condition that is not necessarily directly detectable by pilots, and would not be included in a PIREP. There were no lightning strikes near the accident site around the accident time. A simulation program was run to model the three-dimensional air movements near the accident site at the accident time. The program indicated that mountain wave activity, as well as updrafts and downdrafts, were likely near the accident site. Up- and downdraft velocities of just over 1,000 feet per minute (fpm) were likely, and the largest and most rapid transitions from up- to downdrafts occurred near the accident site. According to the model, the last AMF3853 radar target was located in a downdraft with a velocity between 600 and 1,000 fpm. Air Traffic Controller Weather Information According to the information provided by the FAA, the ZAB controllers working the flight had access to the METARs, TAFs, AIRMETs, and PIREPs that were current for the route of the flight. The Weather and Radar Processor (WARP) was the syst
The airplane’s inadvertent encounter, in night instrument meteorological conditions, with unforecast strong up- and downdrafts and possibly severe airframe icing conditions (which likely included supercooled large droplets that the airplane was not certificated to fly in) that led to the pilot's loss of airplane control.
Source: NTSB Aviation Accident Database
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