History of Flight

On January 2, 2013, at 0200, two Bell 206B-3s certified to 14 CFR part 27 (normal category), departed Delano Airport (KDLO) to perform frost eradication aerial applications over a vineyard southeast of Delano Airport. Frost eradication requires a helicopter to fly at a low altitude (below 50 feet above ground level (AGL). The intent is to pull down higher, warmer air from a temperature inversion, using rotor downwash to prevent frost damage to the plants. The accident pilot from the first helicopter had returned to the airport once for refueling and then proceeded again to the work site to continue performing aerial application of frost mitigation.

Just prior to 0600, dark night conditions prevailed and the pilot of the second helicopter, who was also performing frost mitigation, noticed the fog was starting to develop. The second pilot requested that the accident pilot climb and contact San Joaquin Helicopters, located at KDLO, to inquire about the weather and whether or not they should continue working. At approximately 0550, KDLO reported visibility as seven miles, so the accident pilot descended and they continued flying over the fields. After a few more passes, both pilots noticed an increase in fog formation and initiated a climb to 1,000 feet. They then began a return to KDLO on a 310 heading. The top of the fog was about 500 feet AGL and still forming.

The second pilot noted the accident helicopter began to make a right turn. He asked the accident pilot if she was lost, which she confirmed. The second pilot told her to turn left toward the airport and then he looked back toward the north edge of the city to re-acquire a visual reference through the fog. Shortly after, he observed a fire on the ground through the fog and attempted to contact the accident pilot but received no reply. The accident helicopter crashed about ten miles southeast of the destination airport, impacting the terrain in a steep right bank.

Neither the accident aircraft nor the pilot were certified for instrument flight rules (IFR) flight. Examinations of the helicopter and engine revealed no evidence of pre-impact mechanical malfunctions nor failures that would have precluded normal operation.

Investigators determined that the dark night conditions, sparsely lit terrain, and accumulating fog reduced the visual cues available for the pilot to maintain orientation. Under those conditions, the helicopter's external spotlights, which were switched on during the accident flight, could have further reduced visibility or provided misleading visual cues. These conditions were conducive to the development of spatial disorientation.

Pilot Experience

The pilot, age 62, held a commercial pilot certificate with rotorcraft-helicopter, airplane single-engine land, multi-engine land, and instrument airplane ratings. She was not instrument rated in a helicopter. She held a second-class airman medical certificate issued in March 2012, with no limitations. The pilot reported on her most recent FAA airmen medical certificate application that she had accumulated 1,300 total flight hours, with 250 hours in the previous six months.

As of December 18, 2012, according to the pilot's logbook, the pilot had accumulated 1,576 hours in all aircraft. She had flown 490.9 hours in helicopters and 424.3 hours in turbine helicopters, with 221.2 hours being night hours. She accomplished night currency on November 29, 2012 in an AS350, with the most recent night flight time logged in a Bell 206L on November 13, 2012. Her actual crop drying experience was recorded in a Bell 206B and totaled 12.6 hours, with the last flight being on April 26, 2012, over seven months prior to the accident flight. Her logbook entries showed recent flight experience referring solely to flight instruments included 67.5 hours of simulated and 2.7 hours of actual instrument meteorological conditions (IMC) flight in fixed-wing aircraft. According to the helicopter flight log, she had flown the accident helicopter two days prior to the accident. The first flight was for training and currency and was 0.6 hours in length. The second flight was for frost control work and was 4.5 hours in length. No other flight time was found with this operator in the previous six months. Even for instrument-rated helicopter pilots, flying in actual instrument conditions or unintended IMC is challenging.

Currency vs. Proficiency

Chapter 12 of the Helicopter Flying Handbook notes that many accidents can be blamed on the pilot's inability to recover an aircraft after entering IMC. The instinct to focus visually outside the aircraft while flying is very strong and can only be overcome through proper training and experience. A pilot flying in unfamiliar conditions, such as dark night, IMC, especially when flying a low altitude mission, experiences a much higher workload than a pilot who is used to these conditions and is proficient with transitioning to the instruments when in IMC.

The FAA's Helicopter Flying Handbook, FAA-H-8083-21A, dated 2017, chapter 14, "Effective Aeronautical Decision-Making," states, "Another important part of managing workload is recognizing a work overload situation. The first effect of high workload is that a pilot begins to work faster. As workload increases, attention cannot be devoted to several tasks at one time, and a pilot may begin to focus on one item. When a pilot becomes task saturated, there is no awareness of additional inputs from various sources, so decisions may be made on incomplete information, and the possibility of error increases. A very good example of this is inadvertent IMC. Once entering into bad weather, work overload becomes immediate."

Mentally, the pilot must transition from flying with a visual reference outside of the aircraft to flying with reference only to the flight instruments inside the aircraft. Losing all visual references can cause sensory overload. Instead of trusting the aircraft's instruments, pilots may tend to focus on the few visual references they have and may disregard other surrounding factors. Chapter 14 goes on to say, "Instead of slowing the helicopter down, they increase airspeed. Because they are looking down for visual references, they forget about the hazards in front of them and finally, because they are not looking at the flight instruments, the aircraft is not level. All of this can be avoided by proper training and proper planning. If going inadvertent IMC is the only course of action, pilots must commit to it and fly the helicopter using only the flight instruments and not trying to follow what little visual references they have." Although in this accident the pilot was instrument rated in fixed-wing aircraft, the transfer of currency and proficiency from fixed wing to helicopter may not be assumed, is not permitted by regulations, and is unsafe.

Science of Fog

There are multiple types of fog that form in a variety of ways. Radiation fog, the most common type, occurs often throughout the United States and is most prevalent during the fall and winter. Radiation fog forms when the air near the ground cools and stabilizes at night. When the cool air reaches saturation, fog forms at or near the surface, thickening as the air continues to cool. The layer of fog also deepens and extends upward overnight as the air above the initial fog layer cools and becomes saturated. The most common areas for fog development are sheltered valleys where there is little-to-no wind and locations near bodies of water. Radiation fog is usually patchy, tends to stay in one place, and goes away the next day under the sun's rays. Thicker instances of radiation fog tend to form in valleys or over calm bodies of water.

A special kind of radiation fog, called "Tule" (TOO-lee) fog, occurs each winter in the California Central Valley, near the San Joaquin and Sacramento areas, where this accident occurred. The combination of a cool, moist layer of air from the Pacific, close to the surface, with clear skies above, and light winds, results in exceptionally thick fog on many nights from late winter through early spring.

Fog sometimes forms in walls or banks that are not level with the ground from above, which can provide a misleading reference of the ground's location. Fog, being a collection of floating droplets of vapor, captures and scatters light. As fog captures bright light, it scatters and absorbs it, making it more difficult to see and whiting out the pilot's vision.

According to the pilot of the second helicopter, the accident pilot had her external spotlights switched on. Investigators believed that the fog as well as the use of spotlights contributed to the accident pilot's loss of visual reference with the ground and enabled spatial disorientation to occur. This phenomenon is further discussed in Section 3(e) of AC 60-4A "Pilot's Spatial Disorientation."

Remaining in VMC

As stated in the Helicopter Flying Handbook, experience shows that continuing VFR flight in IMC is often fatal. Pilots get fixated on what they see below them and fail to see what is ahead of them, such as power lines, towers, and taller trees. By the time the pilot sees the obstacle, it is too close to avoid collision. Helicopter pilots should always remain aware of flight visibility by comparing how much can be seen ahead. As soon as the pilot notices a marked decrease in visibility, that pilot must reevaluate the flight plan and landing options. A suitable landing area can always be used to sit out bad weather and let conditions improve.

When planning for a night flight, pilots should carefully plan the flight over navigable routes with sufficient check points to ensure clearance from obstructions. Descents should be planned over known and easily identifiable areas. Deteriorating weather is even harder to detect at night; therefore, pilots should constantly evaluate the weather throughout the flight. Below are basic steps to help the pilot remain in VMC throughout the flight.

1. Come to a hover if able or begin very slow flight just above translational lift speeds and land at the nearest safe area.
2. Slowly turn around and proceed back to VMC weather or first safe landing area if the weather ahead becomes questionable.
3. Do not proceed farther on a course when the terrain ahead is not clearly discernable.
4. Always have a safe landing area in mind for every flight and always be aware of the safe landing area's location.
5. Study the route whenever possible before flying it and ensure to stay on course throughout the flight.

There are five basic steps that every pilot should be ultimately familiar with and should be executed immediately after inadvertently entering IMC.

1. Attitude - level the wings on the attitude indicator, both pitch and bank.
2. Heading - pick a heading that is known to be free of obstacles and maintain it. This may be 180° from your current heading.
3. Power - adjust to a climb power setting.
4. Airspeed - adjust to a climb airspeed.
5. Trim - maintain coordinated flight so that an unusual attitude will not develop.

Spatial Disorientation

Unintended instrument meteorological conditions (UIMC), sometimes referred to as inadvertent instrument meteorological conditions (IIMC) by some organizations, is one of the leading causes of fatal helicopter crashes in the United States. That being said, it is rarely the severity of the weather itself that directly causes these accidents, but rather the loss of visual reference in UMIC/IIMC conditions. Often the loss of visual reference with the horizon or the ground causes a phenomenon known as spatial disorientation.

Spatial disorientation, also called a vestibular illusion, is best explained by the question "Which way is up?" The inner ear, which controls balance, is tricked into believing that it is still moving when it is stationary, or that up is not truly up. The inner ear has three semicircular canals containing fluid and a tuft of hairs called the cupola. The fluid in the canals flows and deflects the hairs, granting the ability to sense pitch, yaw, and roll motions and control balance. 

Spatial disorientation can occur any time the pilot makes a sustained constant rate turn or moves their head while turning. The fluid in the inner ear canals flow past the hairs in the cupola, indicating a turn. When the fluid catches up with the speed of the wall of the canal, such as in a constant rate turn, the turning sensation stops. As the turn comes to a close, the fluid begins to deflect the hairs in the opposite direction, giving the feeling that the pilot is now turning or banking in the opposite direction. Therefore, the inner ear tricks the pilot into believing they are in a turn, when the pilot could be flying steady and level.

Conversely, the pilot could also sense they are flying in steady level flight, when in fact the pilot could be flying at a significant bank or pitch. The disorientation can be combatted by acquiring a visual reference with the horizon or by relying on the attitude instruments until the sensation fades. If the spatial disorientation is not noticed and quickly corrected, the end effect is inevitably flight into terrain.

As outlined in AC 60-4A, pilots need to understand the elements contributing to spatial disorientation so as to prevent loss of aircraft control if these conditions are inadvertently encountered. The following actions should be taken to assist in preventing spatial disorientation.

1. Before flying with less than three miles visibility, obtain training and maintain proficiency in aircraft control by reference to instruments.
2. When flying at night or in reduced visibility, use flight instruments in conjunction with visual references.
3. Maintain night currency if flight at night is intended. Include cross-country and local operations at different airports.
4. Study and become familiar with unique geographical conditions in areas in intended operating areas.
5. Check weather forecasts before departure, en route, and at destination. Be alert for weather deterioration.
6. Do not attempt visual flight rule flight when there is a possibility of getting trapped in deteriorating weather.
7. Rely on instrument indications unless the natural horizon or surface reference is clearly visible.

In the case of N828AC, the accident pilot lost visual reference when the fog rolled in and became lost and disoriented on the way back to the airport. This figure taken from Chapter 13 of the FAA Helicopter Flying Handbook shows how easy it is to lose visual reference at night. Fog and an activated external spotlight are thought to have further reduced the accident pilot's ability to acquire a visual reference. The pilot of the second helicopter, who witnessed the accident, stated that the accident pilot made a right turn away from the airport before being reminded to turn back to the left and resume the original heading. During either of those turns, if the accident pilot was not watching the artificial horizon, she could easily have become disoriented and "leveled off" the turn into a banked angle instead of being truly level. The NTSB report states that there was evidence of a steep right turn upon impact with the terrain. This suggests the pilot, upon turning, had not leveled off properly due to spatial disorientation. According to a study done by the US Helicopter Safety Team from 2009-2014, IIMC (and the accompanying spatial disorientation) comprised over 15% of all fatal helicopter accidents during that time. The Civil Aeromedical Institute (CAMI) has heavily researched spatial disorientation and published a series of videos on the phenomenon for pilots and airmen to stay aware. The videos go into detail about the workings of the inner ear and the cause of spatial disorientation, as well as different scenarios that can occur as a result. The best advice CAMI gives for pilots experiencing spatial disorientation or flying in IIMC is to trust the instruments and focus on flying the aircraft.

Conclusion 

The pilot failed to adequately control the helicopter, which was as a result of entering fog and subsequently becoming spatially disoriented and crashing the helicopter. The accident pilot did not take into consideration the disorienting effects of having an external spotlight on while flying in degraded conditions such as fog. In addition, neither the pilot nor the accident aircraft were certificated for IMC.

Back to top

The National Transportation Safety Board determined the probable cause of this accident to be the pilot's failure to maintain helicopter control due to spatial disorientation while maneuvering in low visibility, dark night conditions.

NTSB Report Number: WPR13FA080

Back to top

None.

Back to top

§91.155 Basic VFR Weather Minimums

Except as provided in paragraph (b) of this section and §91.157, no person may operate an aircraft under visual flight rules (VFR) when the flight visibility is less, or at a distance from clouds that is less, than that prescribed for the corresponding altitude and class of airspace in the table provided in the guidance.

The rule states that no person may operate a helicopter 1,200 feet or less above the surface under VFR rules unless the flight visibility at night is at least one statute mile and the pilot remains clear of clouds, which was not the case in this accident. 

Helicopter Flying Handbook FAA-H-8083-21

Chapter 12 - Attitude Instrument Flying

This chapter introduces basic instrument training. It is a building block toward basic instrument training, but it is not a substitute for the more detailed information found in the FAA Helicopter Flying Handbook FAA-H-8083-21.

As stated in the handbook, "Prior to any flight, day or night, an inadvertent IMC plan should be carefully planned and, if possible, rehearsed. Many aircraft mishaps can be blamed on the pilot's inability to recover an aircraft after inadvertently entering IMC. The desire to stay outside visually is very strong and can only be overcome through training. IMC-trained helicopter pilots should climb to a safe altitude free of obstacles and obtain an instrument clearance from ATC. However, for the nonrated pilot and, more importantly, a non-IFR-equipped helicopter, remaining VMC is critical. Pilots who are not trained in IMC have a tendency to try to chase favorable weather by flying just above the treetops or following roads. The thought process is that as long as they can see what is below them, then they can fly to their intended destination.

Also stated in the handbook, "The night flying environment and the techniques used when flying at night depend on outside conditions. Flying on a bright, clear, moonlit evening when the visibility is good, and the wind is calm is not much different from flying during the day. However, if flying on an overcast night over a sparsely populated area, with few or no outside lights on the ground, the situation is quite different. Visibility is restricted, so be more alert in steering clear of obstructions and low clouds. Options are also limited in the event of an emergency, as it is more difficult to find a place to land and determine wind direction and speed. At night, rely more heavily on the aircraft systems, such as lights, flight instruments, and navigation equipment. As a precaution, if visibility is limited or outside references are inadequate, strongly consider delaying the flight until conditions improve, unless proper instrument flight training has been received and the helicopter has the appropriate instrumentation and equipment."

Chapter 13 - Night Operations

Knowledge of the basic anatomy and physiology of the eye is helpful in the study of helicopter night operations. Adding to this the study of visual illusions gives the pilot ways to overcome those illusions. For example, atmospheric illusions - rain on the windscreen can create the illusion of greater height, and atmospheric haze can create the illusion of being at a greater distance from an object. The pilot who does not recognize these illusions flies lower. Penetration of fog can create the illusion of pitching up. The pilot who does not recognize this illusion pushes the nose forward, often quite abruptly. Techniques for preflight, engine start-up, collision avoidance, and night approaches and landings help teach pilots safer ways to conduct flights at night.

While ceiling and visibility significantly affect safety in night VFR operations, lighting conditions also have a profound effect on safety. Even in conditions in which visibility and ceiling are determined to be VMC, the ability to discern unlit or low contrast objects and terrain at night may be compromised. An understanding of "seeing conditions" aides pilots as they gain night flying experience in a particular area. This knowledge helps them plan and accomplish flights in this area. If the normal area of operations changes, the experience gained helps the pilot to identify hazards and determine acceptable levels of future risk.

The Pilots Handbook of Aeronautical Knowledge Chapter 16 pages 16-20 provides additional night operations information.

Chapter 14 - Effective Aeronautical Decision-Making

Helicopters have the unique capability to fly and land in more diverse situations than fixed-wing aircraft. Pilots attempting to fly the helicopter beyond their abilities or beyond the capabilities of the helicopter are many reasons for accidents. Instructors should incorporate single-pilot resource management (SRM) and risk management into flight training instruction of aeronautical decision-making (ADM).

SRM is the art of managing all resources, inside and outside of the aircraft, before and during the flight. SRM is key component of ADM.

FAA-H-8083-15 Instrument Flying Handbook

Chapter 6 - Helicopter Attitude Instrument Flying

Controlling the aircraft by reference to the instruments rather than outside visual cues.

AC 60-4A "Pilot's Spatial Disorientation" Section 3(d)(e)4(a)(b)

As stated in the AC:

3. Discussion

3(d) "Surface references and the natural horizon may at times become obscured, although visibility may be above visual flight rule minimums. Lack of natural horizon or surface reference is common on overwater flights, at night, and especially at night in extremely sparsely populated areas, or in low visibility conditions. A sloping cloud formation, an obscured horizon, a dark scene spread with ground lights and stars, and certain geometric patterns of ground lights can provide inaccurate visual information for aligning the aircraft correctly with the actual horizon. The disoriented pilot may place the aircraft in a dangerous attitude. Other factors which contribute to disorientation are reflections from outside lights, sunlight shining through clouds, and reflected light from the anti-collision rotating beacon."

3(e) "Another condition creating restrictions to both horizontal and vertical visibility is commonly called "white-out." "White-out" is generally caused by fog, haze, or falling snow blending with the snow-covered earth surface which may obscure all outside references. Therefore, the use of flight instruments is essential to maintain proper attitude when encountering any of the elements which may result in spatial disorientation."

Night Flying

While the pilot was qualified to fly at night, the aircraft, while not rated for IFR operation, was equipped with basic ADI and HSI information. However, without a natural horizon the pilot was forced to fly with only the basic set of flight instruments, utilizing the turn and bank and pitot-static instruments to maintain control. This was a difficult task and as the accident report detailed, resulted in the pilot's disorientation and loss of control.

A rotorcraft private pilot has no regulatory requirement for training flight solely by reference to instruments (14 CFR 61.109c). Further there is no checking requirement under the current Practical Test Standard (PTS).

A rotorcraft commercial pilot requires five hours of training flight solely by reference to instruments (14CFR61.129c). There is no checking requirement under the current PTS.

A helicopter 135 competency check under 14CFR135.293c addresses a requirement for a pilot to be able to recover from UIMC/IIMC only if the helicopter is IFR certified. "For non-IFR-certified rotorcraft, the pilot must perform such maneuvers as are appropriate to the rotorcrafts installed equipment, the certificate holder's operations specifications, and the operating environment."

SAFO 17008, 25 May 2017 Attitude Indicator Pitch Limitations

Purpose: This SAFO serves to notify aircraft operators of potential operational limitations of some attitude indicators in the event of unusual attitude recovery as recommended by National Transportation Safety Board (NTSB) Safety Recommendation A-14-108.

View SAFO 17008.

Back to top

Task-Focused Pressure

Job Completion

Due to job pressures to perform and complete a task, pilots may disregard flight planning, weather conditions, and other technical or environmental hazards. Frequently the pilot continues VFR flight into dark night conditions and/or IMC, as they do not regard these conditions as dangerous. Chapter 14 of the Helicopter Flying Handbook emphasizes the importance of smart aeronautical decision making. Chapter 12 of the Helicopter Flying Handbook also speaks to planning ahead in case of inadvertent IMC.

Return to Base

Due to the desire to return the aircraft to base, pilots, especially when flying with a task in mind, tend to not see the flight as complete until they have landed back home with the job accomplished. Similarly, some pilots tend to fixate on "what happens next" and feel embarrassed or trapped if they cannot make it to where they are supposed to be. For this reason, the "Land and Live" safety initiative encourages helicopter pilots to put the aircraft down in a safe landing zone instead of taking unnecessary risks just to get to back to home base.

Back to top

• Continued flight in a degraded visual environment which leads to unintended or inadvertent flight into IMC should be avoided
• Spatial disorientation results from a loss of visual reference in IMC and without a rotorcraft instrument rating it would be difficult to transition to instruments

Back to top

VFR pilots are equipped with a strategy that provides for an exit strategy should they encounter IMC conditions.

• In this accident, the pilot was operating in marginal VFR conditions when the fog intensified, but the pilot did not exit the instrument conditions.

Weather briefings to include forecasts of the intended path of flight are critical to safe operations.

• Tule fog is a common weather phenomenon in this area during the winter season, yet investigators were unable to determine if the pilots obtained an adequate weather briefing.

Back to top

None identified.

Back to top

While there were no safety initiatives taken as a direct result of this particular accident, initiatives have been taken by both industry and the FAA to mitigate this type of accident.

On February 21, 2014, the FAA enacted a rule entitled "Helicopter Air Ambulance, Commercial Helicopter and Part 91" 2120-AJ53, Document Number: 2014-03689. This rule increased the weather minimums for all general aviation helicopter operations. Weather Minimums for Helicopters Flying Under Visual Flight Rules in Class G Airspace (§ 91.155). The rule revised § 91.155 Class G airspace weather minimums for part 91 helicopter operations. This rule provides a greater margin of safety for operators because pilots are required to maintain a fixed amount of visibility and would be less likely to suddenly encounter instrument meteorological conditions (IMC).

91.155 - Basic VFR Weather Minimums

SAFO17008 (ADI limitations)

SAFO17008 was published "to notify aircraft operators of potential operational limitations of some attitude indicators in the event of unusual attitude recovery as recommended by National Transportation Safety Board (NTSB) Safety Recommendation A-14-108." The SAFO cites accident report NTSB/AAR-14/03 in which a Eurocopter AS350 operating in Alaska had an ADI that only met the minimum performance standards. Additionally, it recommends that all aircraft operators be aware of the limitations of older ADIs that may only meet the minimum standards.

FAA Pilot Proficiency Program/WINGS

Of the flying programs that exist for pilots, one of the official FAA recommendations is the FAA's Pilot Proficiency Program. Newly redesigned, this program has been in service since 1977 and is known as the Wings program. The program has resulted in a lower accident rate in addition to a benefit of lower insurance rates. A 1985 FAA report showed one accident for every 555 pilots participating in the Wings program, versus one accident for every 247 pilots not participating.

New Technology

In modern aircraft, technology has an increased presence in the cockpit. ADS-B is a relatively new technology that allows pilots access to real-time traffic, weather, and flight-information data. This information being readily available in real time could reduce accidents due to in-flight collisions and provide better awareness of weather conditions.

"Land & LIVE"

The "Land & LIVE" initiative is a program endorsed by Helicopter Association International that encourages helicopter pilots to land instead of continuing to fly in dangerous conditions. Helicopters have a unique ability to land anywhere and do not require a suitable runway like fixed-wing aircraft. If meteorological conditions degrade or a pilot discovers they are unfit to continue flight, "Land & LIVE" urges pilots to consider a precautionary landing instead of risking the lives of themselves and their passengers.

Back to top

None.

Back to top

Rotorcraft Life Cycle:

• Operational

Accident Threats:

• Controlled Flight Into or Toward Terrain (CFIT) 
• Unintended Flight in IMC (UIMC)
• Low Altitude Operations (LALT)

Industries:

• Aerial Application

Accident Common Themes:

• Human Error

Back to top

Human Error

The accident pilot failed to maintain visual reference with the ground due to the dark night and fog. Investigators determined she left her external spotlight switched on, possibly impairing her vision, contributing to the loss of visual reference. As a VFR pilot, she failed to transition from visual flying to instrument flying and eventually succumbed to spatial disorientation.

The pilot had the option to return to base sooner when she noticed the weather starting to deteriorate. Delaying the decision to return had profound consequences in this accident.

Back to top

The NTSB database has many examples of UIMC related accidents. The following accident is similar to this Bell 206 accident:

NTSB Identification: CHI90MA244
Aircraft: Bell 206, registration: N16933
Accident Occurred: August 27, 1990, in Elkhorn, WI
Injuries: 4 Fatal

Four helicopters were transporting a concert group from a golf course near Elkhorn, WI, to Chicago, IL. As the third helicopter (N16933) departed, it remained at a lower altitude than the others and the pilot turned southeasterly toward rising terrain. Subsequently, the helicopter crashed on hilly terrain about 3/5 mile from that takeoff point. Elevation of the crash site was about 100 feet above the golf course and 50 feet below the summit of the hill. Pilots of the other helicopters reported VFR flight conditions with some fog. A ground witness near the crash site reported haze and ground fog of varying intensity with patches of low clouds but said stars could be seen through the fog.

The National Transportation Safety Board determined the probable cause of this accident to be improper planning by the pilot and his failure to attain an adequate altitude over rising terrain. Factors related to the accident were darkness, fog, haze, rising terrain, and a lack of visual cues.

Back to top

Technical Related Lessons

Flight using visual flight rules (VFR) requires a continuous awareness of the horizon. Loss of an external horizon reference, for even a few seconds, can often result in spatial disorientation and correspondingly incorrect control inputs. This can rapidly lead to aircraft attitudes from which recovery is difficult or impossible. (Threat Category: Unintended flight in IMC)

• Due to dark night conditions and accumulating fog, the VFR-rated pilot needed to transition from flying with reference to outside the cockpit, to flying with reference to instruments only. The pilot did not have a helicopter instrument rating and had little time flying with sole reference to instruments in helicopters and airplanes combined.
• With no external attitude reference, spatial disorientation overcame the pilot. Shortly after entering the fog, the pilot admitted over the radio that she felt lost, and quickly after, lost control of the helicopter, resulting in the accident.

Common Theme Related Lessons

Effective aeronautical decision-making is equally important in single-pilot general aviation operations as it is in multi-crewmember large commercial operations. Single Pilot Resource Management (SRM) is critical to safe operations as a pilot manages all available resources to ensure a safe flight. Pilots must be aware of their own limitations, plan ahead, and act decisively to minimize risk. (Common Theme: Human Error)

• Making the decision to continue flying in a degrading visual environment made it more difficult for the pilot to return home safely.
• Prior to entering UIMC the pilot did not consider taking advantage of the helicopter's ability to land and did not execute a precautionary landing.
• Investigators concluded that using a spotlight in fog that scattered and reflected light could lead to a further loss of visual reference, resulting in spatial disorientation.

Back to top