WPR13FA072

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.

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 adde

ATC Communications The first recorded contact by AMF3853 with any ATC facility occurred at 1811:26, when the pilot contacted ZAB for an IFR clearance to PHX. At 1814:35, after internally coordinating the handling of the flight, the controller cleared AMF3853 directly to "Phoenix," with an altitude crossing restriction of 10,000 feet 40 miles "north of Phoenix." The pilot questioned whether the clearance was for him; the controller then repeated the clearance, and the pilot read it back. No other communications occurred between ATC and AMF3853 until 1823:55, when the pilot requested "lower" due to some "heavy up- and downdrafts." The controller responded that he was unable to issue lower, that the radar was indicating that the airplane was 500 feet below the assigned altitude of 10,000 feet, and that the ATC minimum vectoring altitude for that area was 9,700 feet. At 1824:18, the pilot acknowledged that transmission with his flight number and "roger," which was the final transmission from the airplane. At 1825:17, the controller advised AMF3853 that radar contact had been lost. The controller attempted to contact the flight directly, without success. He also requested other aircraft in the vicinity to attempt to reach AMF3853 by radio, to listen for an emergency locator transmitter (ELT) signal, and to "keep an eye out for lights...or a fire" on the ground. At 1845:58, the controller asked another aircraft to make a slight track deviation to visually look for a fire. No aircraft reported any contact with, or indications of, AMF3853. At 1903:23, the controller began communicating on his land line with another controller about the missing flight, and at 1904, an ALNOT (alert notice) for the missing airplane was issued. Ameriflight Communications Provisions According to the Ameriflight General Operations Manual (GOM), the airline's primary means of communicating with its flights was via radio. The GOM stated that "Ameriflight is able to always be in contact with all of its aircraft" and provided the following ordered list of methods: "Company radio, ARINC [a commercial vendor], phone patch, Contract service handlers frequencies, [and] ATC." The GOM stated that all Ameriflight aircraft are equipped with a minimum of two VHF (very high frequency) communications transceivers, and mandated that, exclusive of "arrivals into high density terminal areas," operations in busy terminal areas, flight crews shall continually monitor an appropriate company frequency at all times during flight operations. The GOM specified that "Company radio-telephony is to be used for...company business only," including the relay of messages between Ameriflight airplanes. The GOM also stated that flight crews shall not initiate business related radio communications on company frequency during taxi, flight below 10,000 feet above mean sea level (msl), except in cruise, and other high cockpit workload periods. The GOM noted that the airline used two VHF frequencies for company communications, 131.9 MHz (megahertz) inside California, and 122.875 MHz for all other locations. Outside California, pilots could contact ARINC via the appropriate network frequency, which was depicted on a map stored in each airplane. According to FAA information, P14 was not equipped with an operating air traffic control tower (ATCT). The airport elevation was 5,262 feet msl. PAN was located about 72 miles southwest of P14. Maximum terrain elevation between the two airports was about 8,000 feet msl; that terrain was the Mogollon Plateau. South of the plateau, the terrain descended rapidly, and the southern edge of the plateau, which was oriented approximately east-west, was known as the Mogollon Rim. PAN was situated in the basin about 10 miles south of, and 3,000 feet below, the Mogollon Rim. PAN was equipped with a single paved runway designated 06-24. The runway measured 5,504 by 75 feet, and field elevation was reported as 5,157 feet. PAN was not equipped with an operating ATCT. There was only one published instrument approach procedure (IAP) for PAN. The IAP was an RNAV (GPS)-A approach, with category A and B minimum descent altitude minima of 5,720 feet msl, which was 563 feet above airport elevation, and 1 statute mile visibility. The nearest Victor Airway to PAN was V95. V95 was defined by the 197 degree radial of the Winslow VOR, had a minimum enroute altitude (MEA) of 10,000 feet msl, and passed about 3 miles to the west of PAN. Ameriflight Background Information Ameriflight was a FAR Part 135 operator, which almost exclusively transported cargo. The airline was headquartered in Burbank, California, but operated in, and had 12 bases across, the United States. The airline also operated into Canada and Mexico. The cargo fleet consisted of PA-31, BE-99/1900, SA-227, and EMB-120 airplanes. The airline did not have or utilize any PA-31 or BE-99 FAA-approved motion-based flight training devices. The airline had 12 assistant chief pilots (one per base), about 250 line pilots, and typically hired between 5 and 15 pilots per month. The airline had several senior dispatchers. One of them, who was based at Burbank, was also the hazmat program manager. In an NTSB interview, he stated that he spent about 30 percent of his time in the dispatch function, and the remainder in the hazmat function. The FAA certificate managers, including the principal operations inspector (POI), were based at the Van Nuys FSDO. The Phoenix base had about 20 pilots, and primarily operated PA-31 and BE-99 airplanes. Other base personnel included three dispatchers, a station manager, and an assistant chief pilot. Ameriflight guidance for flight operations was primarily contained in two airline-produced documents and one Piper-produced document. The two airline documents were the GOM and the Standard Operating Procedures (SOP) manual. The GOM was company-wide in its applicability. The SOP and the Piper POH/AFM were specific to the airplane type. Ameriflight Director of Safety Although the position was not required by FAR Part 135, Ameriflight had utilized a Director of Safety (DOS) for several years prior to the accident. The DOS was stationed at the airline's base in Oakland, California. He was also a "Division Manager" responsible for operations, sales, and maintenance services in central California and Nevada. The DOS stated that he spent about "5 to 10 percent" of his time on DOS duties, and had no safety subordinates or assistants, but could obtain support when necessary. The DOS stated that at the time of the accident, his position was still being defined. He had two basic safety tasks, which were analyzing safety issues as they arose, and developing an incident database. The DOS stated that neither his department nor the airline had a dedicated safety budget. His primary safety concerns included pilot experience levels in terms of time and variety, especially with IFR operations and weather, pilot decision making ability and judgment, and training-related issues. He noted that the company had observed that the Phoenix based pilots tended to have more difficulties and perform less well in IFR than Portland (Oregon) based pilots, and that this was likely a result of the typically more benign weather in Phoenix. Although the airline did have a telephonic "safety hotline" that was open to all employees, including pilots, as of the date of the accident, the hotline had received few inputs. The airline also had a non-punitive written event and hazard reporting system referred to as its "immunity-based Safety Reporting System." Employees, including pilots, could also email or telephone the DOS directly, or visit the Safety Department office in person. The scope of these reports was not limited to flight operations only; it included all safety-related aspects of all company operations. Employee reporting of events or hazards was not mandatory. The reporting system did not automatical