At the NTSB, we’ve investigated many tragic transportation accidents that could have been prevented with some planning, forethought, and good decision making. As we mark the beginning of the holiday travel season, we want to encourage all Americans to make it their goal to arrive safely at their destinations, so we’ve boiled down some lessons we’ve learned that the traveling public can use.
Fatigue, impairment by alcohol and other drugs, and distraction continue to play major roles in highway crashes. Here’s what you can do:
If your holiday celebrations involve alcohol, ask a friend or family member to be your designated driver, or call a taxi or ridesharing service.
In a crash, seat belts (and proper child restraints) are your best protection. Always make sure that you and all your passengers are buckled up or buckled in!
Don’t take or make calls while driving, even using a hands-free device. Set your navigation system before you start driving. If you’re traveling with others, ask them to navigate.
By Bus or Train
The NTSB has made recommendations to improve passenger rail and motorcoach operations and vehicle crashworthiness, but travelers should know what to do in an emergency.
Pay attention to safety briefings and know where the nearest emergency exit is. If it’s a window or roof hatch, make sure you know how to use it.
If you’re unsure of where the exits are or how to use them, or if you didn’t receive a safety briefing, ask your driver or the train conductor to brief you.
Always use restraints when they’re available!
By Air or Sea
Airline and water travel have become incredibly safe, but these tips can help keep you and your loved ones safe in an emergency.
When flying, make sure that you and your traveling companions have your own seats—even children under age 2.
Don’t forget your child’s car seat. The label will usually tell you whether your child car seat is certified for airplane use; the owner’s manual always has this information.
If you don’t know the rules for using a child’s car seat on your flight, call the airline and ask what you need to know.
Pay close attention to the safety briefing! Airline and marine accidents have become very rare, but you and your family can be safer by being prepared.
Whether you’re on an airplane or a boat, know where to find the nearest flotation device.
No matter how you travel, you deserve the benefits of the lessons we’ve learned through our investigations, but you need to play an active part to take advantage of them. This holiday season, make a commitment to put safety first.
I recently had the privilege of speaking in Manchester, England, at the National Safer Roads Partnerships Conference. The United Kingdom has some of the lowest road-user fatality rates in the world. While our annual vehicle miles traveled vary greatly, on a typical day, about 109 road users are killed on America’s roadways, while only 5 Britons lose their lives the same way. But, as I reminded the conference audience, even one fatality is still too many.
This was a unique opportunity to represent the NTSB because the audience was mainly British law enforcement officers, and the British tradition of “policing by consent” was tailor‑made for a prevention-focused discussion. Policing by consent means that, because most people want law and order, the goal should be to prevent crime rather than focus on punishing perpetrators. Our Safety Advocacy Division operates with much the same philosophy, working to prevent transportation accidents by encouraging stakeholders to implement the agency’s recommendations. We also explain road safety to vulnerable populations, such as young drivers, to bring lifesaving information to the traveling public, and we share our findings with colleagues.
We know that, as we face coming challenges in road safety, prevention opportunities abound. Our recent speeding study noted the value of a “safe system” approach, which depends on layers of safety in a given road environment and recognizes preventive uses of technology, such as automated speed enforcement. Our recent investigation into the fatal crash of a partially automated vehicle allowed us to consider the double-edged sword of automation. Our investigations have shown that, as vehicles rely more and more on automated sensors, they also collect more data, which should be gathered in a standard format and reported when vehicles with enabled control systems crash.
The world is changing, crash factors are changing, and our tools are changing. The data that cars themselves can provide about crashes is expanding. As I told the law enforcement officers in Manchester, the NTSB has learned that everything an accident can tell us is worth our attention. We are conscious that every safety lesson learned is worth retelling, both to spur acceptance of our recommendations and to prepare ourselves, our colleagues, and the public for the challenges of a fast-approaching future. By sharing lessons learned across borders, we improve our chances at reaching zero transportation fatalities worldwide.
Nicholas Worrell is Chief of the NTSB Safety Advocacy Division.
On September 19 and 20, the NTSB held a Runway Incursion Forum featuring some of the industry’s foremost runway safety experts. These experts came from far and wide, and from a variety of aviation associations, companies, research organizations, government agencies, and airports. It was a very thought‑provoking event, and I believe we had the right people at the table to address an increasing trend in the most significant (Levels A and B) runway incursion events.
The aviation industry has proven itself to be adept at tackling challenging safety issues. In the early 1990s, the fatal commercial aviation accident rate that had been declining for several decades began to plateau. Many safety experts concluded that further reduction in the rate was unlikely because the plateaued rate was already exemplary. Nonetheless, concerned that the volume of flying was projected to double in the next 15–20 years—and with it, if the rate remained flat, the number of airline crashes—the industry began an unprecedented voluntary collaborative safety improvement program to further reduce the accident rate. This program was called the Commercial Aviation Safety Team, or CAST. Amazingly, CAST reduced the flat fatality rate by more than 80 percent in only 10 years.
Perhaps the most difficult challenge that we are currently facing regarding runway incursions is pursuing additional remedies in the absence of an accident. The industry is frequently accused of having a “tombstone” mentality: attempting to improve safety only when there’s a major accident. I applaud the efforts of the FAA, the general aviation community, the commercial aviation industry, and the airports, along with the front-line vigilance of the pilots, air traffic controllers, and airport operators who live and breathe this issue every day, to proactively identify ways of driving down the numbers. It’s a sign of this vigilance that they came together out of our common concern about the apparent turnaround from the previous downward trend in A and B incursions.
So, what did we learn from our forum? First and foremost, the staff who organized this event recognized one of the major lessons learned from the CAST collaboration: that everyone who is involved in a problem should be involved in developing the solution. Hence, we invited pilots, air traffic controllers, airport operators, affected industry organizations, and the regulator (the FAA), as well as those who collect and analyze the data—in other words, everyone who is involved in the problem—to discuss their perspectives on the runway incursion problem.
Each participant emphasized the need for more and better data: data to help us identify the problems, determine what caused them, develop interventions, and determine whether the interventions are accomplishing the desired result. We need to determine how to collect better data, how to analyze the data more effectively, and, pursuing the collaboration concept, how to share the data more effectively, both with peers and with other participants in the system.
Perhaps the most challenging issues that warrant better data are the human factors issues regarding human limitations and vulnerabilities, and determining how humans can interact most effectively with rapidly advancing technologies. There has been considerable progress in understanding human factors in the cockpit, and it was interesting to hear in the forum about the development of a new program that also aims to enhance our understanding of human factors issues that affect air traffic controllers.
Participants at the forum also discussed several exciting new technologies—in the cockpit, in air traffic control facilities, at airports, and in airport ground vehicles—to help increase the situational awareness of pilots, controllers, and vehicle operators. We heard of many activities by the airport community to address “hot spots,” the places on the airport surface where runway incursions are occurring most frequently. These activities include changing procedures, improving training, adding new technologies, and making major capital improvements to modify airport geometry.
Runway incursions are increasing amidst a culture that, in the last 15–20 years, has become more sensitized to their potential danger. What is needed is both site‑specific remedies (due to the uniqueness of every airport) and systemic remedies that address the system’s commonalities. Through their presentations and active participation in our forum, it became clear to me that our forum participants refuse to wait for an accident to begin making improvements.
We heard from multiple participants that about 80 percent of runway incursions involve general aviation aircraft. Although the creation of new collaboration networks, such as the General Aviation Joint Steering Committee (GAJSC), is beginning to bring general aviation stakeholders more consistently into the runway incursion prevention conversation, we learned that the effort to bring all stakeholders to the table must continue, which is a challenge because the general aviation community is very broad and multifaceted.
I am optimistic that government, airlines, airports, and others will follow up on the most important directions that we collaboratively identified in the forum, and that they will continue to develop and deploy new solutions to the complex problem of runway incursions.
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.
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.
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
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.
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.
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.
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.”
“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.”
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.
This is the third 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.
I joined the NTSB in 2010 as a recorder investigator in the Vehicle Recorders Division. I work to recover “1s and 0s” from electronics, including cockpit voice and flight data recorders (aka “black boxes”) and video sources. As a recorder investigator, I work early in the investigative lifecycle to create factual reports of electronic data: if it might record something and has a green board or a little chip, we’re interested.
My formal training and experience is in aeronautical engineering, aviation, computer/database/iOs programming, and conversation analysis. I’m also a flight instructor, former regional airline captain, and aircraft owner. Through my work on more than 400 NTSB investigations and my 30 years as a flight instructor, I’ve had some incredible moments, but my most memorable is soloing my son in our tailwheel Maule on his 16th birthday. We enjoyed the usual fun so many pilots experience on soft fields, and it was a success. Now, about 10 years later, my son is a certified flight instructor-instrument (CFII) who has taught his own students.
Soft fields are fun, but they also carry risks that pilots have to manage. The FAA Airman Certification Standards (ACS) for private and commercial pilots include soft-field takeoffs and the separate (but arguably related) short-field takeoffs.
What do soft and short fields have to do with readouts of recorded data? Normally, nothing. When something goes wrong, however, the data can sometimes help piece together the story.
I recovered data from electronic devices in two soft-field investigations. Unfortunately, there were no survivors in either accident, but these fatal crashes highlight some of the risks noted in the ACS.
The first case involved a 1956 Cessna 172 in Veneta, Oregon, with four people on board. The airplane was just below gross weight and within center-of-gravity limits. According to other investigative information, the grass of the 3,200-foot runway was mowed to about 3 inches in height and was damp from a prior rain shower.
I was given an iPhone recovered from the passenger in the right front seat. It yielded some photos of the pilot and passengers before boarding and a video of the first 23 seconds of the accident flight. Below is a picture taken before boarding, showing the accident airplane with the runway environment behind. The tall grass immediately apparent in the photo obscures the runway, which is further in the background. This photo was useful to corroborate the weather conditions at the time of the accident.
The 23-second video also helped. It began when the aircraft was on its takeoff roll. We worked with the raw video as recorded, rather than subject it to labor-intensive postprocessing, which is sometimes necessary to stabilize the constantly shifting camera angle of an iPhone video. One significant feature of the video was that from the 15-second mark until the end of the recording, we could hear a sound similar to the stall warning. Some partial views of the instruments supported other evidence indicating that the engine was operating properly.
When combined with other investigative evidence, the NTSB determined the probable cause of this accident was “The pilot’s failure to maintain adequate airspeed and altitude to clear trees during takeoff initial climb.” (You can access the detailed factual reports here: https://go.usa.gov/xRGGe.) I often use this case while teaching students about soft- and short‑field takeoffs to emphasize the ACS risks of collision hazards, including aircraft, terrain, obstacles, and wires; low altitude maneuvering, stall, and spin; and runway surface conditions.
The second soft-field/short-field case that rested (in part) on my work with recorded data was the crash of a 1977 Cessna T210M in Challis, Idaho, also with four people on board, loaded to 3,551 pounds (maximum gross weight for this plane was 3,800 pounds) and within center-of-gravity limits.
According to other investigative information, the 5,500-feet mean sea level airport had a 2,500‑foot turf/dirt runway, with an estimated density altitude during the accident of 6,046 feet. Because of terrain features, pilots generally landed on runway 22 and departed on runway 4. The accident flight was departing on runway 4.
Two significant electronic devices were recovered from this accident: a JPI EDM-700 engine monitor and a Garmin GPSMAP 496 portable GPS device. Both have recording capabilities, but each sustained impact and postimpact fire damage requiring chip-level data recovery. The figures below show the JPI EDM-700 and Garmin 496 chips that were recovered.
Using tools in our lab, we removed the chips and cleaned them up. We then “imaged” the chips (that is, created a file of all the 1s and 0s on the chip) using a commercially available chip programming device. Our frequent experience with the JPI EDM-700 and Garmin 496 contributed to our efficient data extraction from the binary image to produce useful engineering data.
In this case, the JPI EDM-700 recorded the takeoff and supported other investigative information showing that the engine was functioning properly. As you can imagine, when working with recovered avionics, data can be confusing; in this case, the end of the recording had unchanging data. By comparing the accident takeoff data with a prior takeoff, combined with our prior knowledge of the EDM-700 recording logic, we were able to attribute the unchanging data to invalid data after the aircraft had crashed.
The Garmin 496 recorded the accident flight and 49 prior flights. Although the accident flight was undoubtedly helpful to the investigation, we also decided to compare the accident takeoff to nine prior takeoffs on the same runway, considering groundspeed and lateral path. The accident flight differed from all prior flights in that prior flights proceeded to the right of the accident flight’s trajectory near the departure end of runway 4.
Investigators worked with Cessna to calculate the takeoff performance. With no wind, to clear a 50-foot obstacle, the airplane would need 2,231 feet of runway. With a 5-knot tailwind, the airplane would need 2,677 feet. The actual distance from the start of the takeoff roll to the point at which the aircraft struck the first 50-foot tree was 2,625 feet.
Our report noted, “In the takeoff configuration, with the nose-high pitch, it is possible that the pilot’s windscreen view of the terrain would be limited.” We determined the probable cause was “The pilot’s attempt to depart in conditions that resulted in the airplane having insufficient performance capability, which resulted in a collision with a tree.” (You can access the detailed factual reports here: https://go.usa.gov/xRGGd.)
I often use this accident to teach my students the ACS short-field knowledge areas of the “effects of atmospheric conditions, including wind, on takeoff and climb performance,” as well as risk management regarding the “selection of runway based on pilot capability, aircraft performance and limitations, available distance, and wind.”
As Mike Hart wrote in AVweb, “If the calculated length of the field is less than the number calculated from the POH, don’t even think about turning your prop. An obvious accident is avoided.” He goes on to add, if the calculated distance is at all close, check your math and your assumptions. Pilot technique and aircraft condition are just two factors that can make a world of difference.
The electronic devices you use when you fly can increase your situational awareness and enjoyment. Some devices empower you to check historical engine trends and identify mechanical issues early. And, in the relatively rare cases when things go wrong, we can use this electronic information—all those 1s and 0s—to dig deeply into what went wrong and how, and help avoid a similar outcome in the future.