Wasilla, AK, USA
N1839Z
CESSNA 210-5
N30CC
DEHAVILLAND DHC 2
The flight instructor and student pilot on board the Cessna were conducting practice takeoffs and landings using the airport's published right-turn traffic pattern. At the same time, the commercial pilot of a single-engine de Havilland airplane departed an airport 5 miles to the north, proceeded to the airport and turned onto the final leg of the traffic pattern for landing. The instructor on board the Cessna reported that, during their fourth landing, just as the student began the landing flare, there was a sudden loud noise, and the airplane abruptly nosed down and impacted the runway. The instructor reported that he did not hear or see the other airplane before the collision. The pilot of the de Havilland reported that neither he nor his passenger heard any radio transmissions from the Cessna, and they did not see the Cessna in the traffic pattern until impact. The pilot stated that, about 70 ft above the runway surface, the Cessna overtook the de Havilland from directly above, impacting the propeller. The pilot was able to maintain control and subsequently landed the airplane. A postaccident examination of both airplanes, revealed signatures consistent that the initial impact sequence was between the empennage of the Cessna and the propeller assembly of the de Havilland. The pilots for both airplanes reported no mechanical anomalies that would have prevented the airplanes from maneuvering to avoid an impact. Day visual meteorological conditions prevailed in the area, and neither airplane was in communication with air traffic control; the airport was not equipped with a control tower. A recording of transmissions made on the airport's common traffic advisory frequency (CTAF) revealed that, although the Cessna instructor made radio transmissions throughout the first three traffic patterns; no radio transmissions were heard from the Cessna pilots during the final (accident) traffic pattern. The de Havilland pilot stated his airplane's position before entering the traffic pattern and again on the final leg announcing his intent to land. Postaccident examination and testing of the two radios in the Cessna revealed no mechanical anomalies. Additionally, the radios in both airplanes were tuned to the correct frequency for the airport CTAF. The Cessna instructor reported the he made a radio transmission during the final traffic pattern. It was undetermined why no CTAF radio transmission from the Cessna was heard on the CTAF recording for the accident traffic pattern. Neither airplane was equipped with an Automatic Dependent Surveillance – Broadcast (ADS-B) system or cockpit display of traffic information. Had both airplanes been fully equipped with an ADS-B system capable of both transmitting and receiving position data and issuing traffic alerts via cockpit display, each pilot would have been alerted to the presence of the other airplane, and it is likely that the collision would have been avoided. 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. OpsVue track data showed the flights paths for both airplanes as coming from opposite directions for the landing. It is likely that the pilots had relaxed their vigilance in looking for traffic when operating in the airport environment. 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. See-and-Avoid Concept According to 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.
HISTORY OF FLIGHTOn August 5, 2016, about 1340 Alaska daylight time, a Cessna 210-5 airplane, N1839Z, and a turbine-powered, tailwheel/ski-equipped, de Havilland DHC-2T (Beaver) airplane, N30CC, collided midair while landing at Wasilla Airport (PAWS), Wasilla, Alaska. The certificated flight instructor and student pilot on board the Cessna sustained minor injuries, and the commercial pilot and passenger on board the de Havilland were not injured. Visual meteorological conditions prevailed in the area at the time of the accident. The Cessna was registered to Flying High, LLC, and it was operated by the student pilot under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91 as an instructional flight. The Cessna departed Merrill Field Airport (PAMR), Anchorage, Alaska, about 1230. The de Havilland was privately owned, and it was operated by the pilot under the provisions of 14 CFR Part 91 as a personal flight. The de Havilland departed Leisurewood Airstrip (9AK6), Wasilla, Alaska, about 1340. Neither airplane was operating on a flight plan. The instructor on board the Cessna stated that he and the student departed from PAMR to conduct basic instrument flight training before proceeding to PAWS to practice landings. He said that, after arriving at PAWS, the student completed three successful stop-and-go landings on runway 4 while using the published right traffic pattern. He added that he was using the airport's common traffic advisory frequency (CTAF) of 122.80 MHz to announce their positions and intentions throughout the series of stop-and-go landings. The Cessna had two communication radios installed and the instructor and student reported that they utilized the Narco COM IIA radio while at PAWS, due to the presence of static when the Garmin GNS 430 radio was operated. The instructor stated that, during the accident landing, just as the student began the landing flare, there was a sudden loud noise, and the airplane abruptly nosed down. The airplane's nose subsequently impacted the runway. The instructor reported that neither he nor the student heard or saw the other airplane before the collision. The instructor additionally reported that the airplane's landing and navigation lights were on at the time of the accident. The pilot of the de Havilland stated that he and his passenger were en route to PAWS to get fuel before continuing to Healy, Alaska. He stated that, after departing from 9AK6, which was located about 5 miles northwest of PAWS, he conducted a straight-in final approach for landing on runway 4. He further stated that, while on final approach, about 70 ft above ground level (agl) over the runway threshold, the Cessna overtook the de Havilland from directly above, impacting the propeller. Following the impact with the Cessna, the pilot continued the approach and landed on runway 4. The pilot was able to maintain control and maneuver the airplane off the runway to avoid impacting the Cessna. The de Havilland subsequently departed the left side of the runway and came to rest in about 5 ft high vegetation on sloping terrain. The pilot stated that he used the CTAF before and after entering the straight-in final for runway 4 at PAWS, announcing his positions and intentions. The pilot reported that neither himself nor the passenger heard or visually acquired the Cessna before impact. The pilot additionally reported that the airplane's landing and navigation lights were on at the time of the accident. AIRCRAFT INFORMATIONBoth airplanes were equipped with the required communication equipment for the airspace in which they were operating. Neither airplane was equipped with an automatic dependent surveillance – broadcast (ADS-B) system, nor was either airplane required to be equipped with such a system. Cessna The fixed-gear, high-wing, single-engine airplane was manufactured in 1962. The airplane was configured with seating for 2 pilots and no passengers. The airplane was powered by a Continental IO-470 reciprocating engine. The airplane was white with light blue and dark blue accent lines, white wings, a chrome propeller spinner, and a black 2-blade McCauley propeller. De Havilland The tailwheel/ski-equipped, high-wing, single-engine airplane was manufactured in 1964. The airplane was configured with seating for 1 pilot and 9 passengers. The airplane was powered by a Pratt & Whitney Canada PT6A-34 turbine engine. The airplane was beige with light blue and grey accent lines, beige wings, a beige propeller spinner, and a black 3-blade Hartzell propeller. AIRPORT INFORMATIONBoth airplanes were equipped with the required communication equipment for the airspace in which they were operating. Neither airplane was equipped with an automatic dependent surveillance – broadcast (ADS-B) system, nor was either airplane required to be equipped with such a system. Cessna The fixed-gear, high-wing, single-engine airplane was manufactured in 1962. The airplane was configured with seating for 2 pilots and no passengers. The airplane was powered by a Continental IO-470 reciprocating engine. The airplane was white with light blue and dark blue accent lines, white wings, a chrome propeller spinner, and a black 2-blade McCauley propeller. De Havilland The tailwheel/ski-equipped, high-wing, single-engine airplane was manufactured in 1964. The airplane was configured with seating for 1 pilot and 9 passengers. The airplane was powered by a Pratt & Whitney Canada PT6A-34 turbine engine. The airplane was beige with light blue and grey accent lines, beige wings, a beige propeller spinner, and a black 3-blade Hartzell propeller. WRECKAGE AND IMPACT INFORMATIONThe National Transportation Safety Board (NTSB) investigator-in-charge (IIC), three aviation safety inspectors (ASI) from the Federal Aviation Administration (FAA), along with a team of law enforcement officers from the Wasilla Police Department traveled to the accident scene on August 5. The NTSB IIC and the FAA ASIs performed accident site documentation, examined both airplanes, and interviewed the occupants of both airplanes. A postaccident examination of both airplanes, revealed signatures consistent that the initial impact sequence was between the empennage of the Cessna and the propeller assembly of the de Havilland. The substantial damage sustained to the empennage of the Cessna during the impact sequence rendered the airplane uncontrollable and impacted the runway. The de Havilland pilot was able to maintain control and maneuver the airplane off the runway to avoid impacting the Cessna; however, the de Havilland sustained substantial damage from the Cessna impacting its right wing. During the examination of both airplanes at the accident scene revealed that, when power was applied, the 122.80 MHz frequency was displayed for each radio selected in each airplane. The pilots of both airplanes stated that there were no preimpact mechanical failures or malfunctions that would have precluded normal operation of their respective airplanes. ADDITIONAL INFORMATIONOpsVue Track Data OpsVue track data was used to produce the flight tracks for the two airplanes. OpsVue is a commercially-available program that provides track data in a "mosaic" format, by taking all available surveillance data (ADS-B, radar track data, etc.) received from a transponder-equipped aircraft and applying "smoothing" to achieve the displayed flight track and overlaid onto satellite imagery. The track data showed a convergence of the two airplanes' flight paths about 0.80 miles southwest of the approach end of runway 04 at PAWS before the midair collision over runway 4. The precise altitudes captured for the two airplanes in the OpsVue track data could not be confirmed due to the way in which altitude information is corrected for barometric pressure within the OpsVue system. Non-Towered Airport Flight Operations FAA Advisory Circular 90-66B, "Non-Towered Airport Flight Operations," states in part: The pilot in command's primary responsibility is to see and avoid other aircraft and to help them see and avoid his or her aircraft. Keep lights and strobes on. The use of any traffic pattern procedure does not alter the responsibility of each pilot to see and avoid other aircraft. Pilots are encouraged to participate in "Operation Lights On," a voluntary pilot safety program described in the Aeronautical Information Manual that is designed to improve the "see-and-avoid" capabilities. It is recommended that airplanes observe a 1,000 ft agl traffic pattern altitude. Large and turbine-powered airplanes should enter the traffic pattern at an altitude of 1,500 ft agl or 500 ft above the established pattern altitude. A pilot may vary the size of the traffic pattern depending on the aircraft's performance characteristics. The FAA encourages pilots to use the standard traffic pattern when arriving or departing a non-towered airport or a part-time-towered airport when the control tower is not operating, particularly when other traffic is observed or when operating from an unfamiliar airport. However, there are occasions where a pilot can choose to execute a straight-in approach for landing when not intending to enter the traffic pattern, such as a visual approach executed as part of the termination of an instrument approach. Pilots should clearly communicate on the CTAF and coordinate maneuvering for and execution of the landing with other traffic so as not to disrupt the flow of other aircraft. Therefore, pilots operating in the traffic pattern should be alert at all times to aircraft executing straight-in landings, particularly when flying a base leg prior to turning final. Automatic Dependent Surveillance – Broadcast (ADS-B) The FAA implemented national ADS-B technology in Alaska. Formerly known as Capstone, the joint industry/FAA program (which includes ground-based stations, satellites, and airplane avionics) currently provides pilots with situational awareness by displaying the airplane's position over terrain and warns pilots of the presence of other ADS-B-equipped aircraft that may be present, while using global positioning system technology coupled with an instrument panel mounted moving map display. Right-of-Way Rules 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 attempting to make way for an aircraft on final approach. When two or more aircraft are approaching an airport for the purpose of landing, the aircraft at the lower altitude has the right-of-way, but it shall not take advantage of this rule to cut in front of another which is on final approach to land or to overtake that aircraft. Vigilant Lookout FAA Advisory Circular 90-48D, "Pilots' Role in Collision Avoidance," states in part: Pilots should also keep in mind their responsibility for continuously maintaining a vigilant lookout regardless of the type of aircraft being flow. Remember that most midair collision accidents and reported near midair collision incidents occurred during good VFR weather conditions and during the hours of daylight. Pilot Profiles FAA P-8740-51, "How to Avoid a Midair Collision," states in part: There is no way to say whether the inexperienced pilot or the older, more experienced pilot is more likely to be involved in an in-flight collision. A beginning pilot has so much to think about he may forget to look around. On the other hand, the older pilot, having sat through many hours of boring flight without spotting any hazardous traffic, may grow complacent and forget to scan. No pilot is invulnerable. The See-and-Avoid Concept In 1991, the Australian Transport Safety Bureau published a research report titled "Limitations of the See-and-Avoid Principle." The report discusses the role of the see-and-avoid concept in preventing collisions and some of its inherent limitations and states in part: Cockpit workload and other factors reduce the time that pilots spend in traffic scans. However, even when pilots are looking out, there is no guarantee that other aircraft will be sighted. Most cockpit windscreen configurations severely limit the view available to the pilot. The available view is frequently interrupted by obstructions such as window-posts which totally obscure some parts of the view and make other areas visible to only one eye....Visual scanning involves moving the eyes in order to bring successive areas of the visual field onto the small area of sharp vision in the centre of the eye. The process is frequently unsystematic and may leave large areas of the field of view unsearched….The physical limitations of the human eye are such that even the most careful search does not guarantee that traffic will be sighted….An object which is smaller than the eye's acuity threshold is unlikely to be detected and even less likely to be identified as an approaching aircraft….The human visual system is better at detecting moving targets than stationary targets, yet in most cases, an aircraft on a collision course appears as a stationary target in the pilot's visual field. The contrast between an aircraft and its background can be significantly reduced by atmospheric effects, even in conditions of good visibility. An approaching aircraft, in many cases, presents a very small visual angle until a short time before impact. In addition, complex backgrounds such as ground features or clouds hamper the identification of aircraft via a visual effect known as 'contour interaction'. This occurs when background contours interact with the form of the aircraft, producing a less distinct image. Even when an approaching aircraft has been sighted, there is no guarantee that evasive action will be successful. Midair Collison Avoidance Technology The NTSB has published Safety Alert SA-058 Prevent Midair Collisions: Don't Depend on Vision Alone. This document discusses the benefits of utilize technologies in the cockpit to prevent midair collisions and states in part: The "see-and-avoid" concept has long been the foundation of midair collision prevention. However, the inherent limitations of this concept, including human limitations, environmental conditions, aircraft blind spots, and operational distractions, leave even the most diligent pilot vulnerable to the threat of a midair collision with an unseen aircraft. Technologies in the cockpit that display or alert of traffic confl
The failure of both pilots to see and avoid each other while landing at a non-tower-controlled airport, which resulted in a midair collision. Contributing to the accident was the absence of radio calls from the Cessna during the traffic pattern preceding the accident.
Source: NTSB Aviation Accident Database
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