ANC16FA061

The failure of both pilots to see and avoid each other while in level cruise flight, which resulted in a midair collision.

The Cessna had departed about 3 minutes prior on a scheduled passenger flight and the Piper was en route to a remote hunting camp when the two airplanes collided at an altitude about 1,760 ft mean sea level over a remote area in day, visual meteorological conditions. The airline transport pilot and two passengers onboard the Cessna and the commercial pilot and the passenger onboard the Piper were fatally injured; both airplanes were destroyed. Postaccident examination revealed signatures consistent with the Cessna's outboard left wing initially impacting the Piper's right wing forward strut while in level cruise flight. Examination revealed no mechanical malfunctions or anomalies that would have precluded normal operation of either airplane. Neither pilot was in communication with an air traffic control facility and they were not required to be. A performance and visibility study indicated that each airplane would have remained a relatively small, slow-moving object in the other pilot's window (their fuselages spanning less than 0.5° of the field of view, equivalent to the diameter of a penny viewed from about 7 ft away) until about 10 seconds before the collision, at which time it would have appeared to grow in size suddenly (the "blossom" effect). From about 2 minutes before the collision, neither airplane would have been obscured from the other airplane pilot's (nominal) field of view by cockpit structure, although the Cessna would have appeared close to the bottom of the Piper's right wing and near the forward edge of its forward wing strut. The Cessna was Automatic Dependent Surveillance-Broadcast (ADS-B) Out equipped; the Piper was not ADS-B equipped, and neither airplane was equipped with any cockpit display of traffic information (CDTI). CDTI data would have presented visual information regarding the potential conflict to both pilots beginning about 2 minutes 39 seconds and auditory information beginning about 39 seconds before the collision, providing adequate time for the pilots to react. The see-and-avoid concept requires a pilot to look through the cockpit windows, identify other aircraft, decide if any aircraft are collision threats, and, if necessary, take the appropriate action to avert a collision. There are inherent limitations of this concept, including limitations of the human visual and information processing systems, pilot tasks that compete with the requirement to scan for traffic, the limited field of view from the cockpit, and environmental factors that could diminish the visibility of other aircraft. Given the remote area in which the airplanes were operating, it is likely that the pilots had relaxed their vigilance in looking for traffic. The circumstances of this accident underscore the difficultly in seeing airborne traffic by pilots; the foundation of the "see and avoid" concept in VMC, even when the cockpit visibility offers opportunities to do so, and particularly when the pilots have no warning of traffic in the vicinity. Due to the level of trauma sustained to the Cessna pilot, the autopsy was inconclusive for the presence of natural disease. It was undetermined if natural disease could have presented a significant hazard to flight safety. See-and-Avoid Concept According to Title 14 CFR 91.113, "Right-of-Way Rules," "when weather conditions permit, regardless of whether an operation is conducted under instrument flight rules or visual flight rules, vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft." In addition, FAA AC 90-48D, "Pilots' Role in Collision Avoidance," which was in effect at the time of the accident, stated that the see-and-avoid concept requires vigilance at all times by each pilot, regardless of whether the flight is conducted under instrument flight rules or VFR.

Aircraft 1 Neither airplane carried, nor was required to carry, a crashworthy flight data recorder. Cessna Hageland Aviation Services, Inc., was a Title 14 CFR Part 135 certificated operator, providing both scheduled (commuter) and on-demand flights under the brand Ravn Connect. Company pilots were based at various airports throughout Alaska. All flights were planned and released from the Hageland OCC in Palmer. Hageland is a party to the NTSB investigation. Piper Renfro's Alaskan Adventures, Inc., was a Title 14 CFR Part 91 operator, providing both guided and unguided hunting packages, along with fishing packages. The company conducted operations throughout Alaska. All flights were planned and departed from company headquarters at PABE. Renfro's was originally a party to the NTSB investigation, but during the NTSB Party Member review process of the accident report, it was discovered that Renfro's had violated the NTSB Party Member process in accordance with Title 49 CFR Part 831.11 by improperly divulging privileged information it had received by virtue of its party status. Consequently, Renfro's party status was revoked on November 15, 2018. Refer to the Renfro's Alaskan Adventures, Inc. NTSB Party Member Removal Letter in the public docket. Due to the extensive damage sustained to the Cessna's cockpit components, no postaccident operational test of the transceiver was possible. Postaccident operational testing of the Piper's transceiver revealed a primary active radio frequency of 123.675 MHz, and a non-active secondary frequency of 122.90 MHz. The common traffic advisory frequency used at both PARS and PADM was 122.90 MHz. Neither airport was tower-controlled. Both airports were within Class G airspace with Class E airspace starting at 700 ft agl. The area between the two airports was classified as Class G airspace. For both Class E airspace and Class G airspace, there is no regulatory requirement for airplanes to be equipped with two-way radio communications. The location of the midair collision was located at a point-in-space in Class G airspace, right outside of the Class E airspace border of PARS. No FAA radar coverage existed in the accident area. Aircraft Performance and Cockpit Visibility Study An Aircraft Performance and Cockpit Visibility study was conducted. ADS-B data from the Cessna and onboard GPS data from the Piper were used to calculate the position and orientation of each airplane in the minutes preceding the collision. The visibility study indicated that the Cessna and the Piper would have initially appeared as relatively small, slow-moving objects in each pilot's windows (their fuselages spanning less than 0.5° of the pilot's potential field of view, which is equivalent to the diameter of a penny viewed from about 7 ft away). About 10 seconds before the collision, the airplanes would have begun to appear to grow in size suddenly (the "blossom" effect). From about 2 minutes before the collision, neither airplane would have been obscured from the other pilot's (nominal) field of view by cockpit structure, although the Cessna would have appeared close to the bottom of the Piper's right wing and near the forward edge of its forward wing strut. The ADS-B and GPS data were also used to determine the cockpit display of traffic information (CDTI) data that could have been presented to the pilots had both airplanes been equipped to both receive and provide this information. CDTI uses the ADS-B system to drive a traffic situation display in the cockpits of appropriately-equipped aircraft, and optionally to also provide an aural and visual alert of conflicting traffic. The FAA implemented ADS-B technology in Alaska, and the Cessna was equipped with ADS-B Out, which broadcast the airplane's GPS position and other data to ADS-B ground stations and to other aircraft (to receive this information, other aircraft would have to be equipped with ADS-B In; the Cessna was not so equipped, and so would not have been able to receive ADS-B Out messages broadcast from nearby aircraft). GPS data and avionics provide pilots with situational awareness by displaying the airplane's position over terrain; if their aircraft are also equipped with ADS-B In (and the appropriate displays), ADS-B Out messages from other aircraft can warn pilots of the presence of other ADS-B-equipped aircraft that may be present. For the ADS-B system to be able to provide the traffic information required to drive the CDTI displays and alerts of two aircraft that are in danger of a collision, both aircraft must have ADS-B Out and ADS-B In installed. ADS-B Out data from the Cessna was recorded by the FAA and provided to the NTSB. The Cessna had ADS-B Out, but it did not have ADS-B In or any cockpit display of CDTI data; it was not required to be ADS-B In or CDTI equipped at the time of the accident. The Piper was not ADS-B equipped at the time of the accident, nor was it required to be. Had the airplanes been equipped to display CDTI data, the system could have aurally alerted the pilots to the presence of the other airplane and presented precise bearing, range, and altitude information about each target up to 39 seconds before the collision. A CDTI display would have presented the relative positions of the two airplanes visually to each pilot as early as when the Cessna became airborne: about 2 minutes 39 seconds before the collision. For more information, refer to the Aircraft Performance and Cockpit Visibility Study and the ADS-B data in the public docket. Cessna The Alaska State Medical Examiner, Anchorage, Alaska, conducted an autopsy of the Cessna pilot. The cause of death was attributed to blunt impacts and multiple injuries. Due to the level of trauma, the autopsy was inconclusive for the presence of natural disease. The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicology tests on specimens from the pilot. Carbon monoxide and cyanide tests were not performed. Ethanol was detected in muscle at 0.01 mg%, and no drugs were detected in muscle. It could not be determined if some or all of the ethanol was from sources other than ingestion. Piper The Alaska State Medical Examiner, Anchorage, Alaska, conducted an autopsy of the Piper pilot. The cause of death was attributed to multiple blunt force injuries. The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicology tests on specimens from the pilot that were negative for carbon monoxide and ethanol. Cyanide tests were not performed. Naproxen was detected in urine. It is unknown if the pilot was prescribed naproxen by a medical doctor. Naproxen is a medication available in two formulations, prescription and over-the-counter (OTC). Prescription naproxen is used to relieve pain, tenderness, swelling, and stiffness caused by osteoarthritis, rheumatoid arthritis, ankylosing spondylitis and other similar conditions. OTC naproxen is used to reduce fever and to relieve mild pain from headaches, muscle aches, mild arthritis, the common cold, toothaches, and backaches. Naproxen is in a class of medications called non-steroidal anti-inflammatory drug. The National Transportation Safety Board (NTSB) investigator-in-charge (IIC) and two air safety investigators from the NTSB, along with a team of Alaska State Troopers (AST) traveled to the accident site on September 1, 2016. The team members flew in on an AST helicopter and hiked into the locations for both wreckage sites. Two FAA aviation safety inspectors (ASI) conducted aerial surveys of the two wreckage sites via a commercial helicopter. Both wreckage sites were located in areas of rolling hills with heavy vegetation about 10 ft tall and populated with various alder trees, spruce trees, and birch trees. The main wreckage of the Cessna came to rest about 1/2 mile west of the Piper. Cessna The airplane's initial impact point, located at an elevation --- Aircraft 2 On August 31, 2016, about 1001 Alaska daylight time, a turbine-powered Cessna 208B (Grand Caravan) airplane, N752RV, and a Piper PA-18-150 (Super Cub) airplane, N82452, were destroyed when they collided in midair near Russian Mission, Alaska. The airline transport pilot and the two passengers onboard the Cessna and the commercial pilot and the passenger onboard the Piper sustained fatal injuries. The Cessna was registered to N752RV, LLC, Fairbanks, Alaska, and operated by Hageland Aviation Services, Inc., dba Ravn Connect, Anchorage, Alaska, flight number 3190, a visual flight rules (VFR) scheduled passenger flight, under the provisions of Title 14 Code of Federal Regulations (CFR) Part 135. Company flight following procedures were in effect for the scheduled passenger flight, which departed Russian Mission Airport (PARS), Russian Mission, Alaska, about 0958 and was destined for Marshall Don Hunter Senior Airport (PADM), Marshall, Alaska. The Piper was registered to DioAir, LLC, Bethel, Alaska, and operated by Renfro's Alaskan Adventures, Inc., Bethel, as a VFR guided hunting operation flight, under the provisions of Title 14 CFR Part 91. Company flight following procedures were in effect for the flight, which departed Bethel Airport (PABE), Bethel, Alaska, about 0907, and was transporting the passenger to a remote hunting camp about 20 miles northwest of Russian Mission. Visual meteorological conditions (VMC) prevailed in the area at the time of the accident. The operator of the Cessna reported that the flight was scheduled to arrive at PADM at 1017. In addition to the pilot, onboard the airplane was a company employee (non-pilot) and a private individual traveling to Marshall. When the airplane did not arrive as scheduled, the company village agent at PADM notified the Ravn Connect operational control center (OCC) in Palmer, Alaska, which initiated overdue airplane procedures. The OCC contacted two company airplanes near Russian Mission and provided the last latitude and longitude coordinates from the Cessna's Automatic Dependent Surveillance-Broadcast (ADS-B) system. The two company airplanes then flew to the area of the last coordinates and located the accident site. The pilots of the two company airplanes reported their findings back to the OCC. The owner and master guide-outfitter of the hunting/fishing expedition company that operated the Piper reported that the purpose of the flight was to drop off a guide, who was a company employee, along with hunting and field gear at a hunting camp. He reported that he also was flying another company guide to a different hunting camp in another airplane, and that he departed from PABE about 15 minutes after the Piper. The owner reported that he delivered the guide to the hunting camp about 1030, then overflew the Piper's intended destination and saw that the Piper was not present. The owner radioed the company headquarters at PABE for a status update on the Piper and was provided the Piper's last latitude and longitude coordinates from the company's flight following system. The owner then flew to the area of the last coordinates and located the accident site. The owner reported his findings back to the company headquarters. Flight track information recovered from the ADS-B system on the Cessna and a Garmin GPSMAP 296 GPS device on the Piper indicated that the Cessna departed runway 17 at PARS about 09:58:50. At that time, the Piper was about 5.1 nautical miles (nm) west and 1.3 nm south of the Cessna, flying northbound (about 003°) in level flight between 1,700 and 1,800 ft above mean sea level (msl), at an airspeed about 70 knots (kts). Shortly after takeoff, the Cessna entered a climbing right turn to the northwest, rolling onto a heading of 300° at 09:59:41, while climbing through 850 ft msl and accelerating through about 120 kts. The Cessna continued climbing and leveled about 1,760 ft msl at 10:01:00, while accelerating through 138 kts. At that time, the airplanes were 1.1 nm apart and converging. The airplanes continued to converge without further maneuvering until they collided at 10:01:28 at an altitude of 1,760 ft msl. The closure rate at the time of collision was about 145 kts, with the Piper approaching the Cessna from ahead and to the left and the Cessna approaching the Piper from the right. Both operators reported that there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation for each airplane. Cessna The fixed-gear, high-wing, single-engine Cessna airplane was manufactured in 2014 and was configured with seating for the pilot, a co-pilot, and 9 passengers; it also had a belly cargo pod. The airplane was powered by a Pratt & Whitney Canada PT6A-140 turbine engine. The airplane's primary base color was white with red and black accent lines, white wings, a black belly cargo pod, a chrome propeller spinner, and a grey Hartzell propeller. The airplane had 811 hours in service at the time of its most recent approved aircraft inspection program inspection, which was completed on July 18, 2016. Review of the airplane's maintenance records indicated no mechanical discrepancies with the airframe, engine, or propeller. Piper The tailwheel-equipped, high-wing, single-engine Piper airplane was manufactured in 1978 and was configured with tandem seating for the pilot and a passenger; it also had a belly cargo pod. The airplane was powered by a Lycoming O-320 reciprocating engine. The airplane's primary base color was white with blue accent lines, white wings with blue leading edges, a white belly cargo pod, a blue propeller spinner, and a black McCauley propeller. The airplane had 3,559 hours in service at the time of its most recent annual inspection, which was completed on May 26, 2016. Review of the airplane's maintenance records indicated no mechanical discrepancies with the airframe, engine, or propeller. Right-of-Way Rules Title 14 CFR 91.113 lists the right-of-way rules for aircraft, and states: (a) Inapplicability. This section does not apply to the operation of an aircraft on water. (b) General. When weather conditions permit, regardless of whether an operation is conducted under instrument flight rules or visual flight rules, vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft. When a rule of this section gives another aircraft the right-of-way, the pilot shall give way to that aircraft and may not pass over, under, or ahead of it unless well clear. (c) In distress. An aircraft in distress has the right-of-way over all other air traffic. (d) Converging. When aircraft of the same category are converging at approximately the same altitude (except head-on, or nearly so), the aircraft to the other's right has the right-of-way. If the aircraft are of different categories - (1) A balloon has the right-of-way over any other category of aircraft; (2) A glider has the right-of-way over an airship, powered parachute, weight-shift-control aircraft, airplane, or rotorcraft. (3) An airship has the right-of-way over a powered parachute, weight-shift-control aircraft, airplane, or rotorcraft. However, an aircraft towing or refueling other aircraft has the right-of-way over all other engine-driven aircraft. (e) Approaching head-on. When aircraft are approaching each other head-on, or nearly so, each pilot of each aircraft shall alter course to the right. (f) Overtaking. Each aircraft that is being overtaken has the right-of-way and each pilot of an overtaking aircraft shall alter course to the right to pass well clear. (g) Landing. Aircraft, while on final approach to land or while landing, have the right-of-way over other aircraft in flight or operating on the surface, except that they shall not take advantage of this rule to force an aircraft off the runway surface which has already landed and is a