When an Aircraft Goes Missing

By Mike Hodges, Air Safety Investigator, NTSB Office of Aviation Safety

On August 9, 2008, a privately-owned Cessna 182E airplane was reported overdue near Juneau, Alaska. The NTSB immediately started monitoring search efforts being conducted by the US Coast Guard, the Alaska State Troopers, the Civil Air Patrol, and a host of good Samaritans. The search area was expansive and included remote inland fjords, coastal waterways, and steep mountainous terrain. In an effort to start gathering information that was potentially relevant to the accident, we interviewed other pilots flying in the area, as well as Federal Aviation Administration (FAA) Flight Service Station personnel to better understand weather conditions at the time the airplane disappeared. After an extensive but unsuccessful search, search-and-rescue activities were suspended on August 20, 2008.

For all aviation accidents such as this one, when initial search-and-rescue activities are suspended and no wreckage is found, the NTSB issues a preliminary report, available to the public in an aviation accident database that can be accessed through our website. If the wreckage is not located within 180 days from the initial date of disappearance, we complete a final report with a probable cause statement of “undetermined.” The final report includes all pertinent information that was initially gathered at the time the aircraft was reported missing. If the wreckage is eventually located after the initial 180 days, we reopen and complete the investigation.

On October 25, 2017, I was the on-call air safety investigator for the NTSB Alaska Regional Office. Alaska State Troopers notified me that a deer hunter had discovered airplane wreckage on Admiralty Island, about 15 miles south of Juneau, Alaska. We eventually determined that it was the missing Cessna 182E. So, 9 years after the airplane went missing, we reopened the case.

In Juneau, I met with an aviation safety inspector from the FAA, an Alaska State Trooper, and members of Juneau Mountain Rescue. As with most remote aircraft accidents in Alaska, traveling to the scene requires an airplane or helicopter because there are no roads. The NTSB chartered a commercial, float-equipped Cessna 206 airplane, and we flew to Young Lake on Admiralty Island in the Tongass National Forest—the largest intact temperate rainforest in the world.

Flying to Young Lake near the accident site

As an air safety investigator working in Alaska, I often face unique challenges, whether it’s a hike to a remote area to reach an accident site or a wildlife encounter. In this case, after arriving at the northern end of Young Lake, we hiked nearly 2 miles to the accident site, each of us carrying either firearms or bear spray because of the large population of brown bears on the island. We also carried satellite phones because there’s no cell phone reception in the area. The wreckage was in densely‑forested, steep mountainous terrain a little over a mile northwest of the north end of Young Lake, at an elevation of about 1,075 ft. mean sea level. The average tree height at the accident site was about 100 ft.

Landing on Young Lake

When we arrived at the site, the FAA aviation safety inspector and I documented and examined the wreckage. The cockpit and fuselage were destroyed by a postimpact fire. The wreckage of the missing airplane was confirmed via the serial number located on the airframe data plate. Time and nature had taken their toll—the heavily corroded wreckage was covered with dirt, fungus, leaves, and branches. The Alaska State Trooper recovered the remains of the two occupants.

View of the wreckage

Once the investigative and recovery activities were completed, we hiked back to Young Lake, contacted the commercial aviation operator for pickup, and returned to Juneau. Because the location was so remote, the wreckage was not recovered.

Mike Hodges using a satellite phone at Young Lake to provide an update to NTSB leadership

On-scene activity is just one part of our investigative process. In each investigation, we look at the roles of the human, the machine, and the environment. By learning about the factors that cause an accident, we can make recommendations to prevent similar accidents in the future. In this investigation, I reviewed the airplane’s maintenance records, considered the pilot’s aviation training and medical records, and examined meteorological and topographical data for the accident area. As a result of the investigation, the NTSB determined that the probable cause of the accident was the pilot’s decision to continue visual flight into an area of instrument meteorological conditions, which resulted in the pilot experiencing a loss of visual reference and subsequent controlled flight into terrain. The pilot’s self‑induced pressure to complete the flight also contributed to the crash. The final accident report can be viewed here.

If you ever happen to come across aircraft wreckage—or what you think is aircraft wreckage—no matter how old it appears to be, please notify local law enforcement and the NTSB Response Operations Center in Washington, DC. If you’re able, please provide latitude and longitude coordinates of the wreckage location, along with photographs of what you found. The NTSB can then continue investigating what happened, which can help prevent future accidents from occurring. Also, importantly, family and friends of those who died in the accident may be interested in the new information. If you ever have the chance to visit the NTSB Training Center in Ashburn, Virginia, you will see an etched window on the front of the building that states the building is dedicated to the victims of transportation accidents and their families. The display also summarizes the NTSB’s crucial work of improving transportation safety for our great nation: “from tragedy we draw knowledge to improve the safety of us all.”

Don’t Turn A Blind Eye on Risky Pilot Behavior

By Leah Read

This is the seventh blog in a new series of posts about the NTSB’s general aviation investigative process. This series, written by NTSB staff, explores how medical, mechanical, and general safety issues are examined in our investigations.

 

“Turning a blind eye, makes nothing disappear.”  Anonymous

Leah Read, Senior Air Safety Investigator

When air safety investigators arrive at the scene of a fatal aircraft accident, we meet with law enforcement officers, witnesses, friends of the pilot, and family. During these critical interviews, we start to get a bigger picture of the circumstances surrounding the accident and those involved. It’s very common to hear almost immediately that the pilot was very “conscientious,” “thorough,” and an “excellent pilot.”

But there are also times when no one seems to be saying anything much at all about the pilot…until we dig deeper. That’s when we hear things such as, “The pilot never maintained his airplane right.” or “Everybody knew he was going to crash eventually.”

There are also times when the investigator will get a call via our communications center that a witness must talk to someone “right away.” The witness then tells us that the pilot had a LONG history of “maverick-like” behavior, was known to “buzz” a friend’s house, or used illegal drugs—as just some examples. In these situations, we will ask the witness if they had talked to the pilot about this behavior or contacted the Federal Aviation Administration (FAA). They sometimes tell us, “I tried to talk to him, but he wouldn’t listen. He was too prideful.”

But more often, they tell us that they didn’t say anything to the pilot or FAA. Sometimes, the pilot was a friend whom they didn’t want to embarrass or cause any trouble. Personally, as a fellow pilot, I can understand the concerns.

But what if you see something, and don’t step up and say something? The reality is that nonreporting can put people at risk.

Many don’t realize that there are actions the FAA can take if risky pilot behavior is reported. The FAA has established a hotline for confidential and anonymous reporting. As noted on the FAA website, “The FAA Hotline accepts reports concerning the safety of the National Airspace System, violation of a Federal Aviation Regulation (Title 14 CFR), aviation safety issues…. The FAA Hotline provides a single venue for…the aviation community and the public to file their reports.”

As one FAA inspector told me, “We can’t investigate what we don’t know.” If a complaint was made via the FAA Hotline, the FAA would be obligated to investigate. Remember, you may not only save the life of another pilot but also an innocent passenger or bystander.

The NTSB, unfortunately, has seen the tragic consequences of turning a blind eye to a known hazard. I have seen accidents that have occurred in someone’s front yard, skimmed the roof of an apartment building, or crashed near a school. If the airplane had impacted just a few yards in either direction, the damage and loss of life could have been so much worse. This was the case in an accident I investigated where the pilot lost control of the airplane, crashing into a front yard just feet from an occupied house. Thankfully, there was no fire, and no kids were playing in that front yard.

Within moments of arriving on scene and being debriefed by law enforcement, I was handed a witness statement. Very quickly, I realized the witness was quite credible—and what he had to say about the pilot was alarming. The pilot had a known history of reckless behavior. Further investigation revealed that people knew of the pilot’s behavior but didn’t want to report him for several of the reasons I mentioned above. Not surprisingly, the FAA had no negative history on the pilot. He had a clean record and was never on their radar.

Sadly, in this accident, the pilot and his innocent passenger died. But what if he had other passengers onboard? What would have happened if he had crashed into the house, or, worse, a crowd?

A colleague of mine investigated an accident where a pilot was flying an airplane he was not rated to fly, in instrument conditions without holding an instrument rating. The pilot had recorded numerous notes in his logbook that provided compelling evidence of his own unsafe flying, by his own admission. The pilot noted landing on a major highway and flying low over a crowd during parades. He was also known for unsafe low-level flights over airshows and having a general disregard for proper communication procedures. Yet nothing was done about his behavior; people turned a blind eye to it. Tragically, the pilot and three occupants died in the accident when the airplane encountered instrument meteorological conditions and impacted terrain.

In the big scheme of things, we need to ask ourselves, who are we really protecting by keeping quiet?  As active pilots, mechanics, airport personnel, friends, and family members, you are the eyes and ears to what’s going on out there. You know your airport and the people who use it. You know when your friend or family member seems risky or unsafe. If you identify a hazard, then speak up. Or, file a report with the FAA Hotline. Just remember, we all share the same airspace or may be nearby if their plane crashes.

Stay safe and don’t turn a blind eye!

For more information on submitting a report of a risky pilot via the FAA Hotline, visit: https://hotline.faa.gov/

Leah Read is a senior air safety investigator in the NTSB Office of Aviation Safety.

Inside the NTSB’s General Aviation Investigative Process

The Nuts and Bolts

By Aaron Sauer

This is the sixth blog in a new series of posts about the NTSB’s general aviation investigative process. This series, written by NTSB staff, explores how medical, mechanical, and general safety issues are examined in our investigations.

 

The public’s image of our agency is often based on the iconic blue and yellow NTSB jacket they see at accident scenes. What’s less well known is that examining and documenting on-scene evidence is just one step in an exhaustive process to gather all available information, determine a cause, and recommend any changes that can prevent similar accidents.

Since 2014, 12 percent of general aviation accidents—about three accidents every week—have involved a power plant malfunction. These malfunctions may include a fuel issue, component failure, or improper maintenance.  As an NTSB air safety investigator, I investigate such mechanical malfunctions, gather the facts of the investigation, and ultimately help determine the probable causes of accidents.

After the on-scene phase of the investigation is complete, the airplane wreckage is often recovered by professional recovery services and stored in a secure location until we determine if further NTSB investigation is needed. When circumstances, such as a large hole in the engine crankcase or the in-flight loss of a propeller, indicate that further examination is necessary, we work with the airframe, engine, and component manufacturers. These entities serve as parties to our investigation, providing technical expertise on their product. If required, we coordinate a follow-up plan to examine the aircraft wreckage in greater detail. At the accident scene or recovery facility, our investigators examining the machine determine the scope of follow-up based on any anomalies discovered.

In some accidents involving a reported loss of engine power, the initial examination (typically a 100-hour inspection) turns up no obvious anomalies. At this point, one of the best and most telling follow-up activities is to attempt an engine test run. Engine test runs may be performed at a recovery facility or at a manufacturer’s facility. A successful engine test run is a critical piece of information that may lead the investigation down another path.

When, upon initial examination, the investigator observes an engine issue consistent with an internal mechanical failure, it’s typical to disassemble the engine at the manufacturer’s facility or the recovery facility under NTSB supervision. Examining an engine at the manufacturing facility often provides the advantage of having available engineering staff, historical data and drawings, and proper test equipment for the engine components.

Once at the manufacturer’s facility, the investigation team (typically including NTSB, FAA, and airframe, engine, and component manufacturer personnel) determines the plan or approved test procedure for the detailed investigation. The scope of the investigation is determined based on the known facts and circumstances of the accident, the condition of the engine and components, and the work required to confirm the failure. It’s important to note that, although the parties work collaboratively, the NTSB has the final say if there is any disagreement in the investigation process.

Engine functional testing, partial disassembly, and full engine disassembly are the most common investigation techniques used to determine the cause of a failure or malfunction. Disassembly helps us identify fractured or broken parts, which are then documented and set aside for even further examination.

Most manufacturers have their own materials laboratory, metallurgists, and engineers. At this point and with the team present, our investigators may elect to use the manufacturer’s material laboratory for a preliminary examination to obtain a quick analysis of the failure mode, then forward the parts to our materials laboratory in Washington, DC, for a detailed metallurgical examination.

Even observers with a solid understanding of our processes beyond the on-scene images might not understand the many ways that NTSB investigations can improve safety. Even when all signs point to a mechanical malfunction, our investigative process still looks at two other factors: human and environment. When an accident involves reported loss of engine power, we gather information about the pilot and aircraft owner—documentation from the scene, aircraft records, and Federal Aviation Administration (FAA) records. We interview witnesses, visit and examine maintenance facilities, and meet with manufacturers. When necessary, we conduct follow-up examinations and interviews. If FAA inspectors handle the initial on-scene observations, we work hard to guarantee that our two agencies communicate effectively.

When the fact-gathering phase of the investigation is complete, our investigators compile all the relevant factual information, complete a detailed factual report, and create a public accident docket. For an engine failure accident, the docket may include engine reports, materials laboratory reports, aircraft records, and historical engine safety information in the form of service bulletins and airworthiness directives.

Many people understand that we may make recommendations at any point during an investigation, but sometimes our investigations also result in other actions to improve safety. For example, depending on the nature of the material failure, an NTSB investigator may work with the FAA or the manufacturer to issue a manufacturer service bulletin, service letter, safety notice, or a potential airworthiness directive. The safety action taken by the FAA or manufacturer depends on the failure’s cause, fleet exposure, and the potential safety awareness benefit of each product.

Over my 17 years as an NTSB investigator, I’ve investigated numerous engine-failure–related accidents that resulted from human error and material failure. Despite the varied causes and outcomes of these accidents, one fact stands out: proper maintenance is the best way to avoid catastrophic consequences. Following manufacturer-recommended maintenance practices and procedures and adhering to basic maintenance principles can prevent accidents.

Remember: SAFETY is NO ACCIDENT!

All accident reports and public accident dockets are available on the NTSB website:  www.ntsb.gov.

 

Inside the NTSB’s General Aviation Investigative Process

An Aeromedical Mystery Solved

By: Clint Johnson, Chief, Alaska Region, Office of Aviation Safety

This is the fifth blog in a new series of posts about the NTSB’s general aviation investigative process. This series, written by NTSB staff, explores how medical, mechanical, and general safety issues are examined in our investigations.

Clint Johnson at industry event

After nearly 20 years of investigating hundreds of aviation accidents, I recently encountered an invisible killer.

I was enjoying a late summer Saturday afternoon with my wife in Anchorage, Alaska, when my phone rang. My wife – a 20-year-veteran NTSB spouse – knew from the look on my face that our quiet weekend at home had just ended.

An Anchorage Fire Department dispatcher was calling. She reported that rescue crews were on the scene of a fatal airplane crash in a residential neighborhood only 20 minutes away.

When I arrived, I was briefed by a small army of Anchorage Police and Fire Department

Hefty Polar Cub airplane crash site

crews. Behind the wall of fire trucks, police cars, stunned residents, and TV cameras, I caught a glimpse of the inverted and burned remains of what looked like a float-equipped Piper 11 in the middle of the residential roadway.

We continued to talk as we walked toward the wreckage site. The pungent smell of burned aircraft wreckage filled the air as we proceeded past the yellow police tape. Finally, I was close enough to see that only the welded steel-tube structure and engine remained, with the fuselage and wings barely recognizable. The postcrash fire had incinerated much of the wreckage.

Witnesses had told the police that just before the accident they watched in amazement as the airplane completed two, low-level, high-speed, 360° right turns over the neighborhood – the first 150-200 feet above ground level, and the second much lower. One homeowner stated that the airplane passed over his home about 50 feet above his roof.

Witnesses also reported that the airplane’s bank angle increased significantly on the second 360° right turn; one pilot-rated witness estimated the bank at more than 60°. Witnesses also reported hearing the airplane’s engine operating in a manner consistent with high power settings throughout both 360° turns.

One man was mowing his lawn as the airplane completed the second, steep, 360° right turn. He said that the airplane flew directly over his yard, then the nose of the airplane pitched down and it began to descend rapidly. The engine rpm then increased significantly, and the wings rolled level just before the airplane impacted a stand of tall trees adjacent to his home, severing its floats.

It crashed on a neighborhood road, coming to rest inverted. About 30 seconds after impact, a fire ensued, which engulfed the entire airplane before any of the witnesses made it to the wreckage.

Sadly, after the fire department crews extinguished the fire, they found the remains of the 75‑year-old pilot and his dog still inside the incinerated wreckage.

While we all waited for the medical examiner to arrive, I began interviewing witnesses. Most concluded, or were well on their way to concluding, that the pilot was “just showing off” to someone on the ground. But the NTSB sets a high bar for conclusions. It was way too early for me to go there.

At the scene, I met a family member, along with a close friend of the pilot. Understandably upset, both reported that it was highly unusual and uncharacteristic behavior for the pilot to be flying as the witnesses consistently described to me. They went on to say that to their knowledge, the pilot didn’t know anyone in the area, but that, given the pilot’s anticipated flight route, he would have been flying over the neighborhood while on the return flight home.

Then, as the pair was preparing to leave the scene, the pilot’s friend said something in passing – something about his longtime buddy’s history of cardiac problems, which, in his opinion, caused the pilot’s erratic flight maneuvers.

I pressed him for more information, but it became clear that he wasn’t prepared to provide any additional information on the subject then and there, and I decided that this was neither the time or place to discuss it. As the pair got back into their car and slowly drove away, I knew that the following Monday morning I’d likely be attending the pilot’s autopsy.

For now, I needed to document and examine the wreckage before it was removed. This included determining control cable continuity to the flight control system, engine control continuity, and more.

The engine sustained significate impact damage, but only minimal fire damage. There were no mechanical problems that I could find on-scene that would explain what the witnesses reported. However, a much more detailed wreckage exam would be accomplished later, once the wreckage was moved to a more secure and suitable site.

On Monday morning, I found myself at the State medical examiner’s facility, meeting with the pathologist who would be working my case. I explained to her what I was looking for, and she started the exam.

The entire autopsy took over two hours to complete, and the pathologist found no conclusive evidence for medical incapacitation from an acute cardiac event. However, per standard protocol, the autopsy team took blood and tissue samples to send to the FAA’s Bioaeronautical Sciences Research Laboratory in Oklahoma City for a toxicological exam.

I knew I would not have the tox report for two to three months, but the autopsy yielded at least one more piece of valuable information: the pilot died from trauma, not the postcrash fire. Unbeknownst to me at the time, this would be an extremely important data point that would help solve the case in the end.

Over the next two weeks, I visited the wreckage two separate times at a local aircraft salvage yard. I looked for evidence that would support various theories, but nothing ever panned out. It was one dead end after another.

Then on a cold and snowy autumn afternoon, the FAA’s tox report on the pilot appeared in my e-mail. I opened it and scanned the results, and only then realized just what I had been missing all this time: Carbon Monoxide, an odorless, colorless and tasteless gas – and a silent killer of general aviation pilots.

The pilot’s carboxyhemoglobin (carbon monoxide) level was an extremely high 48%. To put these results in context, nonsmokers may normally have up to 3% carboxyhemoglobin in their blood, and heavy smokers may have levels of 10% to 15%. And according to family members, this pilot did not even smoke.

Since the pilot died of blunt-force trauma prior to the ensuing fire, it was not possible that this CO level was an effect of the fire. But it was possible that it was a cause of the crash.

I realized that over the last few months I had missed an important and somewhat elementary piece of evidence, the airplane’s exhaust system. I quickly reviewed my on-scene photos, and I could clearly see that the entire exhaust system sustained relatively minor damage in the accident.

Within 15 minutes of receiving the toxicology results, I was on my way back to the stored wreckage. I ended up bringing the entire exhaust system back to the office, muffler, heat exchanger/muff and all. Like the autopsy examiners I had met months earlier, I went to work on this simpler machinery, peeling back the heater shroud.

Accident muffler can assembly

Inside I found a severely degraded muffler with portions missing, which allowed raw exhaust gases to enter the main cabin through the airplane’s heater system.

Unfortunately, neither the family or any of the pilot’s friends could find any maintenance logbooks for the accident airplane, so I was unable to determine just when the last muffler inspection was done (if ever). However, after talking with several friends of the deceased pilot, many said that he did his own maintenance, and he was not an aviation mechanic.

They went on to say that the pilot, with the help of a few other friends, installed the more powerful Lycoming O-320 engine about 5 years earlier, but none could provide any additional information about how the pilot maintained his airplane.

However, I could report directly to the family what circumstances led up to the death of their loved one, and I was able to show them the physical evidence that I found.

The NTSB’s probable cause summed it all up: “The pilot’s severe impairment from carbon monoxide poisoning in flight, which resulted in a loss of control, and a subsequent inflight collision with trees and terrain.”

Often, it takes time, patience, and knowledge of the human operator, the machine, and the environment to solve an accident mystery to provide answers.

Inside the NTSB’s General Aviation Investigative Process

Do We See and Avoid or Avoid Seeing?

 By John O’Callaghan

This is the fourth blog in a new series of posts about the NTSB’s general aviation investigative process. This series, written by NTSB staff, explores how medical, mechanical, and general safety issues are examined in our investigations.

John O’Callaghan at a runway friction test in Conroe, TX.

As a National Resource Specialist for Aircraft Performance, which is government-speak for a technical expert in the aerodynamics and flight mechanics of aircraft, I work to determine and analyze the motion of aircraft and the physical forces that produce that motion. In particular, following an accident or incident, I attempt to define an aircraft’s position and orientation during the relevant portion of the flight, and determine its response to control inputs, external disturbances, ground forces, and other factors that could affect its trajectory.

I recently reviewed a 2009 cockpit video taken while I was testing a video recording device in a Bellanca Citabria. The footage called to mind recent NTSB cases that highlight the fallacies inherent in one of aviation’s oldest mantras—“see and avoid.”

The video from the camera mounted over my left shoulder reveals a hazy blue sky above and the Potomac River winding lazily below the Citabria’s plexiglass windows. It shows my head dutifully swiveling as I scan the practice area for traffic in preparation for a series of aerobatic maneuvers intended to test a prototype “portable flight data recorder” developed by a friend of mine. I’m flying in the Washington, DC, Special Flight Rules Area so I’m in contact with Potomac Approach, which helpfully keeps a radar’s eye on me and nearby traffic and conveys what I fail to see.

Images captured on the cockpit video during the testing of a video recording device in a Bellanca Citabria.

“Citabria 758, traffic about a mile southwest of your position. A Cherokee is in the practice area, altitude indicates . . . I’m not showing an altitude right now.”

On the video, my head moves around a little more as I respond, “758 looking, thank you.”

The controller then alerts the Cherokee. “Cherokee [call sign], traffic seems to be about 1-mile orbiting, altitude indicates 3,600, a Citabria.”

I’m still looking with no success when Potomac advises that the Cherokee is at 2,200 ft. The controller lets me and the Cherokee pilot know that we are getting close to each other.

 “Cherokee [callsign], traffic just southeast of you, about less than 1 mile, Citabria in the practice area, altitude indicates 3,700.”

 “Roger, we’ll keep our eyes open for that Citabria in the practice area.”

“Citabria 758, that traffic is just northwest of you, less than a mile now, and his altitude still indicates 2,300, appears to be eastbound.”

“758 still looking, thank you.”

The video now shows me craning my neck left and right, leaning forward, scanning the entire symmetrical view offered by an airplane with its seats on the centerline. The airplane banks left and right in gentle turns as I maneuver, trying in vain to spot the Cherokee. A little over 3 minutes after Potomac’s initial advisory, I give up.

“Potomac, Citabria 758 still looking for that traffic . . . is he still a factor?”

“758, now he’s about 5 miles north of you, no factor.”

I don’t know if the Cherokee pilot ever saw me, but if he did, he didn’t announce it. I imagine that most general aviation pilots don’t need to accumulate too many hours before they have an experience much like mine, or its more unnerving inverse: suddenly seeing an airplane that you had no clue about whiz by close enough to read the N-number. Both situations point to the inherent limitations of the “see-and-avoid” concept: the foundation of collision avoidance in visual meteorological conditions (VMC) under visual flight rules (VFR).

My flight was a personal one, unrelated to my duties as an aircraft performance engineer at the NTSB. However, my fruitless search for the Cherokee was consistent with conclusions the NTSB has drawn from investigating a number of midair collisions, and which call to mind what can happen when traffic remains unnoticed.

As detailed in the NTSB reports concerning two midair collisions that occurred in 2015, described further below, the see-and-avoid concept relies on 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.

In a collision between an F-16 and a Cessna 150 near Moncks Corner, South Carolina, in July 2015, the F-16 pilot was unable to spot the C150, even though the Charleston Approach controller had alerted him to the presence of the airplane. The F-16, call sign “Death41,” was flying under instrument flight rules and communicating with air traffic control (ATC); the C150 was flying under VFR and not communicating with ATC.

“Death41, traffic 12 o’clock 2 miles opposite direction 1200 indicated type unknown.”

“Death41 looking.”

“41 turn left heading 180 if you don’t have that traffic in sight.”

“Confirm 2 miles?”

“Death41, if you don’t have that traffic in sight turn left heading 180 immediately.”

[unintelligible reply]

Even before the controller finished her last instruction, the F-16 had begun a standard-rate turn to the left. The F-16 was heavy and, at 240 knots, moving relatively slowly—for a fighter jet. Contrary to what one might think, it could not turn much faster in those conditions. Twenty-three seconds after the controller’s last instruction, the F-16 and the C150 collided at about 1,470 ft above the Cooper River. The crippled F-16 flew for another 2.5 minutes before the pilot ejected safely, and the jet subsequently crashed. The C150 crashed almost directly beneath the collision site, and both the pilot and his passenger died.

We determined the probable cause of this accident was the approach controller’s failure to provide an appropriate resolution to the conflict between the F-16 and the Cessna. Contributing to the accident were the inherent limitations of the see-and-avoid concept, resulting in both pilots’ inability to take evasive action in time to avert the collision.

Midair collisions can happen even when both aircraft are in communication with ATC. A month after the Moncks Corner midair collision, a North American Rockwell Sabreliner collided with a Cessna 172 in the busy traffic pattern at Brown Field in San Diego. Both aircraft were under Brown Tower’s control and on a right downwind for runway 26R, with the Sabreliner outside of and overtaking the C172. The tower controller intended to instruct the C172 to perform a right, 360-degree turn to position him behind the Sabreliner; however, he mistakenly instructed a different C172 to perform the maneuver, and immediately after instructed the Sabreliner to turn right base.

The Sabreliner and C172 subsequently collided, and all five people on the two aircraft died. The cockpit voice recorder on the Sabreliner indicated that both Sabreliner pilots were aware of and concerned about the busy traffic pattern, pointing out other aircraft to each other. One of the nonflying crew in the back of the plane is even heard asking, “see him right there?” presumably referring to traffic. Yet the collision still occurred.

We determined the probable cause of the accident was the local controller’s failure to properly identify the aircraft in the pattern and to ensure control instructions provided to the intended Cessna on downwind were being performed before turning [the Sabreliner] into its path for landing. Contributing to the accident were the inherent limitations of the see-and-avoid concept, resulting in the inability of the pilots involved to take evasive action in time to avert the collision.

My role in the investigations of the Moncks Corner and San Diego collisions was to reconstruct the motion of the airplanes based on radar data and other information, and to evaluate the resulting visibility of each aircraft from the cockpit of the other. In addition, it was my job to evaluate how new collision avoidance technology—such as cockpit displays that provide a radar‑like view of surrounding traffic based on automatic dependent surveillance-broadcast (ADS-B) information—could have averted each accident.

One objective of these visibility studies was to determine whether either of the airplanes involved in the collision were obstructed from the other pilot’s field of view by cockpit structures, or whether the pilots had an unobstructed view of each other but simply failed to see one another (because seeing other traffic from the cockpit is hard!). To find out, we measured the geometries of the window and other structures of exemplar airplanes with laser-scanning equipment, and the resulting measurements were used to determine where the windows were in each pilot’s field of view and whether the other airplane appeared within the windows or not. The results were most intuitively presented by creating computer animations of the collision from the point of view of each pilot using flight simulation software (Microsoft Flight Simulator X) to create the outside scenery and airplane models.

Readers can watch the animations we created for the Moncks Corner and San Diego collisions on our YouTube channel and judge the visibility results for themselves. The performance studies for these accidents provide technical details about the reconstructions, and they note that periods when airplanes are obscured from a pilot’s nominal field of view “underscore the importance of moving one’s head (and occasionally lifting and dipping the wings) so as to see around structural obstacles when searching for traffic.”

Readers can also watch animations of cockpit display of traffic information (CDTI) displays for each of the airplanes involved in these midair collisions. The animations depict the information that these radar-like displays, fed by ADS-B, could have presented to the pilots involved. Had the airplanes been equipped with CDTI, the pilots could have been made aware of the presence and relative locations of the conflicting traffic minutes before the collisions.

In general, the timely and information-rich traffic picture offered by a CDTI can greatly improve a pilot’s ability to detect traffic threats and avoid a collision without aggressive maneuvering. We issued a safety alert, titled, “Prevent Midair Collisions: Don’t Depend on Vision Alone,” to encourage pilots to learn about the benefits of flying an aircraft equipped with technologies that aid in collision avoidance.

Much of flying is an exercise in mitigating or engineering out risk. Pilots are trained, examined, and reviewed; aircraft are certified and maintained; checklists are used; flights are planned; weather is studied. Great effort is made to leave little to chance. However, when it comes to collision avoidance in VMC, we wink at risk management (“see-and-avoid!” “Keep your head on a swivel!”), when the reality is that we rely in great measure on luck. It’s a big sky, and it would be hard to hit somebody if you tried. The odds are against a collision, but on occasion, disaster strikes.

Technologies such as CDTI provide rational risk reduction for the VMC collision avoidance problem. Guardian angels will never lack for work, but tools such as CDTI can help us to make their jobs a little easier.