Board Meeting, May 24, 2011

Collision into Mountainous Terrain. Aleknagik, AK, August 8, 2010

This is a synopsis from the Safety Board's report and does not include the Board's rationale for the conclusions, probable cause, and safety recommendations. Safety Board staff is currently making final revisions to the report from which the attached conclusions and safety recommendations have been extracted. The final report and pertinent safety recommendation letters will be distributed to recommendation recipients as soon as possible. The attached information is subject to further review and editing.

EXECUTIVE SUMMARY

On August 9, 2010, about 1442 Alaska daylight time, a single-engine, turbine-powered, amphibious float-equipped de Havilland DHC-3T airplane, N455A, impacted mountainous, tree-covered terrain about 10 nautical miles (nm) northeast of Aleknagik, Alaska. The airline transport pilot and four passengers received fatal injuries, and four passengers received serious injuries. The airplane sustained substantial damage, including deformation and breaching of the fuselage. The flight was operated by GCI Communication Corp. (GCI), of Anchorage, Alaska, under the provisions of 14 Code of Federal Regulations Part 91. About the time of the accident, meteorological conditions that met the criteria for marginal visual flight rules were reported at Dillingham Airport, Dillingham, Alaska, about 18 nm south of the accident site. No flight plan was filed. The flight departed about 1427 from a GCI-owned private lodge on the shore of Lake Nerka and was en route to a remote sport fishing camp about 52 nm southeast on the Nushagak River.

The accident pilot was highly experienced and familiar with the route from the lodge to the fishing camp. In addition, the accident airplane was equipped with a variety of avionics to assist the pilot with navigation, situational awareness, and terrain avoidance, including two global positioning system (GPS) units with moving map and terrain display capabilities and a radar altimeter with visual annunciator and aural tone capabilities. However, at some point during the final few minutes of the flight, the airplane turned east-northeast (away from its destination) towards mountainous terrain and crashed into the mountainous terrain. The investigation examined the accident pilot's potential for impairment resulting from pilot fatigue or from recent major life events, including his retirement and the sudden death of a family member. In addition, the accident pilot experienced an intracerebral hemorrhage (ICH) in March 2006; the investigation examined the accident pilot's medical history, the Federal Aviation Administration's (FAA) issuance of his unrestricted first-class airman medical certificate, and the potential for medical impairment, both related to and independent of his previous ICH.

No air traffic control communications or air traffic radar data were available for the accident flight, and the airplane was not equipped with a cockpit voice recorder, flight data recorder, or other crash-resistant flight recorder. Without such information, the accident sequence was determined by analyzing the sparse position reports (provided at 3-minute intervals) from the airplane's Sky Connect Tracking System, the limited data extracted from the nonvolatile memory of the digital engine instruments, the available weather information (which was limited because of the potential for localized variability and because the nearest weather reporting facility was 18 nm from the accident site), and the information from the two surviving passengers who were awake at the time of the accident (neither of whom were seated with a clear view of the pilot), ground impact evidence, and airplane crush damage. Based on examinations of the ground marks and the airplane's deformation, the investigation determined that the airplane was in a climbing left turn when it impacted terrain and that flight control inputs occurred shortly before terrain impact; however, the available information was insufficient for the investigation to ascertain the pilot's actions (or lack thereof) in the nearly 3-minute period between the airplane's last reported position and his last-moment control inputs.

The National Transportation Safety Board determines that the probable cause of this accident was the pilot's temporary unresponsiveness for reasons that could not be established from the available information. Contributing to the investigation's inability to determine exactly what occurred in the final minutes of the flight was the lack of a cockpit recorder system with the ability to capture audio, images, and parametric data.

The safety issues discussed in this report relate to the following: the lack of an FAA requirement for a crash-resistant flight recorder system, improperly designed or maintained emergency locator transmitter mounting and retention mechanisms, inadequate FAA guidance related to the medical certification of pilots who have had a cerebrovascular event, and the lack of passenger briefings related to survival and communications equipment. Further, although no weather data deficiencies were found to be related to this accident, the investigation identified areas in which continued enhancements could further improve aviation safety. These include correcting equipment deficiencies at Automated Weather Sensor System sites, developing a test program to evaluate the viability of the real-time transmission of weather information collected from aircraft with data-link equipment (such as Universal Access Transceivers), and providing incentives for data link-equipped aircraft operators to equip aircraft with weather-sensing equipment. Four new safety recommendations concerning these issues are addressed to the FAA, and one new safety recommendation is addressed to the Aircraft Owners and Pilots Association; two safety recommendations to the FAA are reclassified; and two safety recommendations to the FAA are reiterated in this report.

CONCLUSIONS

The investigation determined that the pilot was certificated and qualified in accordance with Federal regulations.
Examinations of the recovered engine, propeller, and airframe components revealed no evidence of any preimpact failures.
The weather conditions forecasted for and observed in the area on the day of the accident did not appear to be exceptional compared to the conditions that the pilot experienced on previous flights.
The airplane was in a climbing left turn when it collided with terrain, and flight control inputs occurred shortly before terrain impact.
The airplane's radar altimeter system provided both aural and visual altitude alerts about 4 to 6 seconds before impact, which likely prompted the pilot to take aggressive action on the flight controls, resulting in the airplane nose-up pitch and left-bank angles evident at the accident site.
Had the pilot not inhibited the terrain awareness and warning system's aural voice and pop-up text alerts, the system would have provided an aural and visual alert up to 30 seconds before the impending collision.
A deliberate execution of a left turn toward the rising terrain by the accident pilot in any weather condition would require a lack of situational awareness that is inconsistent with the pilot's reported level of proficiency, typical safety practices, and familiarity with the area.
A medical condition leading to transient incapacitation or impairment could explain the circumstances of this accident; however, it is not possible to determine whether such a scenario occurred.
Although the pilot had some precursors for the development of fatigue, and the accident circumstances are consistent with fatigue impairment or a sleep event, there is insufficient evidence to determine whether fatigue-related performance or alertness impairments played a role in the accident.
The accident pilot's recent major life events placed him at an elevated risk for stress at the time of the accident, but it is not possible to determine how, or to what extent, this stress may have affected his performance.
A crash-resistant flight recorder system that captures cockpit audio, images, and parametric data would have substantially aided investigators in determining the circumstances that led to this accident.
Had the emergency locator transmitter remained attached to its mounting tray, it would not have become separated from its antenna, and its signals likely would have been detected soon after impact; as a result, rescue personnel would have received timely notification of the accident and its location and could have reached the survivors hours earlier, when the weather and daylight were more conducive for their evacuation.
Had the pilot informed the passengers about the location and use of all survival and emergency communication equipment on board the airplane, particularly the satellite telephone, the passengers may have been able to find and use the telephone to expedite the initiation of search and rescue activities after the accident.
Based on the severity of the nonsurvivable traumatic injuries sustained by the pilot and the four passengers who died at the scene and the relative stability of the serious injuries of the surviving passengers, the delay in accident notification did not result in additional fatalities.
The activities of the volunteer rescuers and the emergency medical personnel aided in the comfort of the surviving passengers while they waited for rescue and may have prevented additional passenger fatalities due to hypothermia from environmental exposure.
The Alaska Regional Flight Surgeon's decision to issue the pilot an unrestricted first-class airman medical certificate, based largely on a local neurologist's in-office evaluation and without conferring with any other Federal Aviation Administration physicians or consultants or attempting to address the etiology of the hemorrhage, the likelihood of recurrence, or the extent of any remaining cognitive deficit, was inappropriate.
It is not clear that a sufficiently thorough aeromedical evaluation of the pilot would have denied the pilot eligibility for a first-class airman medical certificate; however, a more rigorous decision-making process for evaluating this pilot with a history of intracerebral hemorrhage would have decreased the potential for adverse consequences.
The Federal Aviation Administration's internal guidance for medical certification of pilots following stroke is inadequate because it is conflicting and unclear, does not specifically address the risk of recurrence associated with such an event, and does not specifically recommend a neuropsychological evaluation (formal cognitive testing) to evaluate potential subtle cognitive impairment.
The known, widespread Automated Weather Sensor System site deficiencies, if not corrected as expeditiously as possible, will continue to adversely affect the weather reporting network's ability to offer adequate coverage for providing National Weather Service forecasters and pilots with accurate ceiling and/or precipitation information.
The use of data link-equipped aircraft to collect meteorological data and to disseminate this information may provide National Weather Service forecast offices with a more widespread, reliable meteorological dataset to improve the quality of weather forecast products.

PROBABLE CAUSE

RECOMMENDATIONS

New Recommendations

The National Transportation Safety Board makes the following recommendations to the Federal Aviation Administration:

Consult with appropriate specialists and revise the current internal Federal Aviation Administration guidance on issuance of medical certification subsequent to ischemic stroke or intracerebral hemorrhage to ensure that it is clear and that it includes specific requirements for a neuropsychological evaluation and the appropriate assessment of the risk of recurrence or other adverse consequences subsequent to such events.
Correct the deficiencies with the in-service Automated Weather Sensor System (AWSS) stations, specifically the known problems with present weather sensors and ceilometers, to ensure that the AWSS stations provide accurate information as soon as practical.
Implement a collaborative test program in Alaska between the Federal Aviation Administration, the National Weather Service (NWS), the local academic community and private entities to establish the viability of relaying weather information collected from airborne aircraft equipped with existing data-link technology, such as Universal Access Transceivers, to the NWS Alaska Aviation Weather Unit in real time.
If the Federal Aviation Administration's test program recommended in Safety Recommendation [3] establishes that the use of existing data-link technology, such as Universal Access Transceivers, is a viable means of relaying collected information in real time from an airborne platform, encourage and provide incentives to data link-equipped aircraft operators in Alaska to outfit their aircraft with weather-sensing equipment for real-time data relay.

The National Transportation Safety Board makes the following recommendation to the Aircraft Owners and Pilots Association:

Educate pilots of 14 Code of Federal Regulations Part 91 flight operations about the benefits of notifying passengers about the location and operation of survival and emergency communication equipment on board their airplanes.

Previously Issued Recommendations Resulting from this Accident Investigation and Reclassified in this Report

The NTSB issued the following safety recommendations to the Federal Aviation Administration on January 5, 2011:

Require a detailed inspection, during annual inspections, of all emergency locator transmitters installed in general aviation aircraft to ensure that the emergency locator transmitters are mounted and retained in accordance with the manufacturer's specifications. (A-10-169)

The NTSB reclassified Safety Recommendation A-10-169 "Open—Unacceptable Response" in section 2.5.2 of this report.

Determine if the emergency locator transmitter (ELT) mounting requirements and retention tests specified by Technical Standard Order (TSO) C91a and TSO C126 are adequate to assess retention capabilities in ELT designs. Based on the results of this determination, revise, as necessary, TSO requirements to ensure proper retention of ELTs during airplane accidents. (A-10-170)

The NTSB reclassified Safety Recommendation A-10-170 "Open—Acceptable Response" in section 2.5.2 of this report.

Previously Issued Recommendations Reiterated in this Report

The NTSB reiterates Safety Recommendations A-09-10 and -11 to the Federal Aviation Administration, as follows:

Require all existing turbine-powered, nonexperimental, nonrestricted-category aircraft that are not equipped with a cockpit voice recorder and are operating under 14 Code of Federal Regulations Parts 91, 121, or 135 to be retrofitted with a crash-resistant flight recorder system. The crash-resistant flight recorder system should record cockpit audio, a view of the cockpit environment to include as much of the outside view as possible, and parametric data per aircraft and system installation, all to be specified in European Organization for Civil Aviation Equipment document ED-155, “Minimum Operational Performance Specification for Lightweight Flight Recorder Systems,” when the document is finalized and issued. (A-09-10)

Require all existing turbine-powered, nonexperimental, nonrestricted-category aircraft that are not equipped with a flight data recorder and are operating under 14 Code of Federal Regulations Parts 91, 121, or 135 to be retrofitted with a crash-resistant flight recorder system. The crash-resistant flight recorder system should record cockpit audio (if a cockpit voice recorder is not installed), a view of the cockpit environment to include as much of the outside view as possible, and parametric data per aircraft and system installation, all to be specified in European Organization for Civil Aviation Equipment document ED-155, “Minimum Operational Performance Specification for Lightweight Flight Recorder Systems,” when the document is finalized and issued. (A-09-11)