Preventing Stall/Spin Accidents

Phantom arrested landing

I’ve touched on this subject before (see Aviation Myth #14), but for some reason the idea that limiting bank angle will prevent stall/spin accidents keeps rearing it’s ugly head.

It doesn’t. It can’t. It won’t.

Angle-of-bank limitations have been suggested by flight instructors, alphabet groups, pundits, and most recently by Richard Collins of all people. In an Air Facts article last month, he wrote:

The pilot of a Mooney stalled and spun in, apparently while making a steep turn to try to patch up an overshoot of the turn to final. This happens and is easily addressed by never exceeding 30 degrees of bank below 2,000 feet. When the decision is made to “bend” an airplane around at low altitude it is likely to be bent, literally. The moment the pilot decides to try to salvage a bad approach is when risk peaks.

I’m sure Collins is well aware that stalls and spins have no relation to bank angle. You can stall an aircraft in level flight. In fact, that’s how most intentional stalls and spins are performed. The only requirement is that the airfoil be made to exceed the critical angle-of-attack. The same is true with spins: they are not related to aircraft attitude whatsoever. It is only necessary that the aircraft be uncoordinated when the wing is stalled.

An arbitrary bank angle limitation does not make a stall/spin scenario less likely. It does the exact opposite, forcing a pilot to skid the aircraft rather than make a steeper (yet properly coordinated) turn when necessary.

And it will be necessary at some point, due in large part to that very same bank limitation. How’s that for a chicken-and-egg scenario? Lower bank angles mean larger radius turns. The larger the radius, the more skill and precision one must exhibit in order to intercept a specified ground track, as a pilot must do prior to landing. It would be like trying to fly the pattern on autopilot. Oh, you could probably do it, but it would be clumsy, difficult, and you’d be limited to one of those gargantuan, bomber-sized patterns which takes you far from the airport at low altitude — unsafe in its own right — while simultaneously annoying folks both on the ground and in the air.

Many pilots don't know the difference between a slip and a skid and lack an appreciation for the distinction.

Many pilots don’t know the difference between a slip and a skid and lack an appreciation for the distinction.

Some of these bank limits would make landing at certain airports nearly impossible. Kern Valley Airport (L05), with it’s tight downwind adjacent to steep terrain, comes to mind. Collins must know this; he’s been aviating almost since the airplane was invented. That’s what makes his stance so mystifying. When we encounter birds or a traffic conflict in the pattern, are we to stick with, say, a 20 degree bank and accept the collision? What about a moderate over- or undershoot on final? I know, “just go around”. But when bank angles are limited, even that may not be enough.

Two years ago, I recounted the story of what happens when these kinds of limits are placed on a student pilot. It’s something that would have fit right in with Collins’ “Risky Moments” article:

I was at an uncontrolled airport one day watching pilots do their thing, when a student pilot entered the pattern and announced her intention to land on runway 25. On her first attempt her Cherokee blew through the final approach course and she wisely went around. The next time she did the same thing. The third attempt was a larger pattern with an earlier turn to final which resulted in an undershoot. Trying to fix that, she allowed her glidepath to get too high. Another go-around.

By this point the student was pretty rattled and, I’m sure, more that a little embarrassed by her inability to land. You could hear it in her voice as she made various radio calls. After four or five attempts someone had to talk her down via the radio.

What the heck had happened, I wondered? Was there an abnormally high wind aloft just pushing her through the final? Was she turned loose by her instructor with insufficient training? Perhaps there was a mechanical problem with the airplane. Was the traffic on the CTAF too distracting? Maybe she was from a quiet country airport (as if we have any of those in Southern California…).

Further investigation revealed that her CFI had taught her not to exceed some arbitrary bank angle in the pattern. I don’t remember if it was 20 degrees or 30. Maybe it was 15. The exact figure is not important. This poor lady’s instructor had told her that the way to avoid an inadvertent spin in the pattern was to limit her bank angle.

Student pilots often demonstrate a lower (though still adequate) level of performance at cross country airfields than at their home airport due to higher workload. Unfamiliar surroundings, dealing with a CTAF instead of a controller (or vice-versa), different runway numbers and pattern altitudes, etc. That’s when mistakes are more likely to be made.

Saddling the student with a hard limit on bank angle is just asking for a stall/spin situation. That’s my real objection. It’s not simply that angle-of-bank limits don’t work. It’s that they create the very situation proponents claim they’ll prevent.

It would be far easier and safer for pilots to simply learn proper coordination and angle-of-attack awareness. Instead, we try to make due with one crutch after another: angle-of-attack computers, stall warning devices, mechanical rudder limiters, elimination of spin training, curtailing full-stall exposure. And now, of course, bank angle limits. It reaches the point where pilots get so wrapped around the axle about how load factors increase with bank angle that they forget this is only true while maintaining a constant altitude. It’s a rote response, the very lowest level of learning.

Sure, highly specialized flight operations might call for high-tech solutions. If you need to stop a 50,000 pound swept-wing fighter on a pitching carrier deck within 340 feet, flying an exacting angle-of-attack is, if you’ll pardon the pun, critical. By all means, use that AOA gauge. But most of us are putting an aircraft weighing 90% less on a runway that’s 1,500% longer. These programmed, mechanical solutions to basic flying scenarios are not an adequate substitute.

Angle-of-attack awareness and proper coordination are “Flying 101″ tasks which are literally taught in the first few lessons of a student pilot’s career. If anyone holding an airman certificate lacks these rudimentary skills, aren’t they acting as pilot-in-command without really knowing how to fly?

A Skosh of Paranoia

cirrus-wreckage

A fellow pilot and I got into a conversation recently about an AOPA accident reconstruction. A Cirrus SR-22 pilot was instructed to enter the pattern downwind at Melbourne, Florida, and then was simply cleared to land without being informed about another aircraft on a straight-in final for the same runway. By the time the Cirrus was on base, the tower tried to fix the conflict by urging the pilot to cut a hard right turn toward the runway. The result was a fatal stall/spin accident.

My friend wrote:

I can all but guarantee that controller had forgotten about the Cirrus on the straight-in when he cleared the accident aircraft to land. I don’t know of any controllers that would clear someone to land from the downwind with the intention of them following an aircraft that was on a straight-in.

Recovery should’ve been simple, have the accident aircraft just continue northbound and make a 270 to join the final for 9R, once clear of the arriving Cessna for 9L and the Cirrus for 9R. Or, a go-around.

Yelling “Cut it in tight” is quite possibly the dumbest thing you can tell a landing aircraft to do unless you’re trying to get them killed.

I agreed with him: the controller probably forgot about the Cirrus and his urgent-sounding instruction to “cut it in tight” was a poor move. AOPA concluded that the issue was a communication breakdown, and while that might be a contributing factor, it’s not the controller who is responsible for the flight. It’s the pilot.

Despite the stall/spin character of the accident, this wasn’t necessarily a stick & rudder flying problem per se. It seems to me that his error was trying to please the controller, that commanding, disembodied voice on the other side of the frequency who seemingly knows best. A better idea might have been for the pilot to simply add power and climb straight out. Or make a (more gentle) turn. Or anything else, as long as he didn’t stall the aircraft.

It’s a shame we pilots feel the compulsive need to follow the flying directions of people who don’t know how to fly. If you step back and look at it from that perspective, the folly of abdicating even the slightest bit of our PIC authority and decision-making power to another becomes evident. But for some reason, this deferral seems to be baked into our DNA, and we ignore that tendency at our peril. Skepticism and a skosh of paranoia are not always a bad thing.

In this case, the smarter move would have been to simply say “unable, I’m going to climb out to the north and circle back onto the downwind” and let ATC deal with it. I actively watch for moments like these when I’m instructing, because they present a vital learning experience for the student that might save their hide somewhere down the line long after I’ve left the cockpit.

I bet if you played this clip for a dozen pilots and ask them to identify the fatal flaw, most would either blame the controller for the poor direction or the pilot for stalling the airplane. Both made errors, no doubt about it. But if you look at it from a larger point of view, I think the issue was simply trying to comply with a controller directive when the correct action would have been to realize it was patently unsafe to do so.

This is all after-the-fact Monday-morning quarterbacking, of course. I can’t claim to know what the pilot was thinking when he cranked into that tight left turn. Perhaps he thought the other aircraft was about to hit him and turned away for that reason. Sometimes immediate action is called for.

Speaking of which, I was being coached in the aerobatic box at Borrego Springs a few years ago and while in the middle of a figure — a 45 degree up-line, no less — the guy coaching me called over the radio and said, “Traffic, turn right NOW” and I simply did it. Good thing too, because a Bonanza went right through our waivered and NOTAMed airspace, totally oblivious to what was going on just feet from his aircraft. If I’d delayed by another second I’d probably be dead.

On the other side of the coin, I was taxiing out from the ramp at São Paulo/Congonhas Airport in Brazil a couple of months ago and the ground controller gave us a taxi route which required crossing a runway, but didn’t include the runway crossing instruction in the route. That was odd, but in foreign countries it’s not uncommon for them to use slightly different words or phraseology. I asked the other pilot to confirm with the controller that we were, indeed, cleared to cross that runway. ATC replied in the affirmative. Whew!

Still, something didn’t feel right. We looked at each other, I set the parking brake, and we agreed that we weren’t going to go anywhere until we were fully convinced that the controller knew exactly where we were. Long story short, our inclinations were correct and ATC was completely confused about our location despite our specifying the exact intersection numerous times. A skosh of paranoia already accompanies most international flying, but this really put us on our toes for the rest of the trip.

You’ll hear all sorts of advice on emergent situations. Some say never rush into anything, others will tell you immediate, decisive action is invaluable. It would be lovely if there was a single “best strategy” for every situation, but like many things in the world of aviation, there are times when one of those responses can save your bacon… and just as many when it might get you killed. The real trick is knowing which is which.

The Key to Good IFR: More VFR

asiana-214

The Asiana 214 investigation has proven to be every bit as interesting and disturbing as I’d predicted.

Most of the reporting and commentary has been focused on the pilot’s interaction with — and understanding of — the aircraft’s automation system. It seems clear they were having trouble getting the aircraft to do what they wanted during the approach into San Francisco.

You won’t hear pilots bragging about this at cocktail parties, but “what’s it doing now?” is uttered far too often on the flight deck. I myself have been puzzled about why the airplane didn’t do what I thought I asked it to do. Usually it’s a programming issue, but not always.

The most recent issue of NASA’s Callback publication, issue 407, details the story of four professional flight crews who had automation confusion issues similar to that experienced by the Asiana crew. So this isn’t exactly uncommon.

Either way, pressing the wrong button is not a criminal offense.

“Cleared for the Visual.” Gulp!

What is criminal is putting a captain on the flight deck of a passenger airliner when he’s unable to comfortably hand-fly it, because when the electrons aren’t flowing the way you want ‘em to, flying the airplane by hand is often the best course of action… not to mention the most fun, too.

Well, most of the time anyway.

The Asiana Airlines training captain who crashed a Boeing 777 at San Francisco International Airport in July was anxious about the visual approach, which he described as “very stressful,” according to investigators.

Capt. Lee Kang Kuk, an eight-year employee of Asiana on his first extended trip flying the 777, also told investigators he was confused about the operation of the airplane’s automation controls, according to a report released by the National Transportation Safety Board on Wednesday as the board held a hearing into the crash.

The 777’s speed dropped dangerously low on the approach, made with assistance of the PAPI lights but without vertical guidance from the ILS glideslope, which was out of service at the time. Both Asiana 214 pilots said they were unsure about the automation mode with respect to the autothrottles, which should have been engaged on the approach. Instead, the autothrottles were set to idle, according to investigators.

The training captain stated it was “very difficult to perform a visual approach with a heavy airplane,” according to the safety board summary of an interview with the pilot. Asked whether he was concerned about his ability to perform the visual approach, he said, “very concerned, yeah.”

An automation interaction problem — the so-called “FLCH trap” — I can understand. But inability to comfortably fly a visual approach? On the surface, that’s a major head-scratcher. When you dig a little deeper, however, it makes perfect sense.

The Key to Good IFR: More VFR

I don’t know how Asiana does it, but many foreign airlines hire their pilots “ab initio”, meaning they are trained by the airline as airline pilots from day one. They have no exposure to pleasure flying, aerobatics, or gliders because the concept of “general aviation” does not exist in most countries. Ab initio airline pilots receive only the minimum required VFR experience. As soon as they venture into instrument flying, the VFR world is left behind forever. They have no use for it! Or so they think.

I’d imagine many of them never fly under visual flight rules again for the rest of their lives. It’s sad. And it’s no wonder some of them are uncomfortable with the thought of flying a visual approach!

It’s not as if the weather was poor, the runway short, or the airfield surrounded by high terrain. There were no issues with density altitude, runway slope or width, or anything else. San Francisco International’s runway 28R is nearly 12,000 feet long. I’ve landed on it many times myself. The weather was clear, winds calm, and the airport is unmistakably large.

Sure, the controllers do tend to keep arriving aircraft quite high. But even from 10,000 feet on a tight downwind, it’s not rocket science to start slowing the airplane and adding drag. Unless you’re asleep at the wheel, you know what’s coming. And even if you don’t, you can ask. The controllers speak English, too. A visual approach in those conditions shouldn’t scare the pilot-in-command of any aircraft. In fact, if there’s an easier way to land an airplane, I’m not sure what it is.

Kids Can Do It — Why Can’t We?

To put this in perspective, consider a glider. It has no engine, and therefore cannot abort a landing attempt. Once you begin an approach to the runway, you are going to land, period. These aircraft have no instruments, no electronic guidance, and they fly in and out of airports without any visual landing aids whatsoever. The landing areas tend to be short, narrow, and rough. And here in the U.S., students as young as fourteen years old can fly them solo. Fourteen! They’re just kids, and apparently even with virtually no flight time, they have no trouble getting comfortable with something that a highly experienced major airline captain felt very uneasy attempting.

This begs the question of how Captain Kuk became so uncomfortable with a simple visual approach. I’d estimate that 75% of all approaches are visuals. I’d be shocked if Kuk hadn’t flown literally hundreds of them. As a scheduled airline pilot, he was required to undergo recurrent training every six months, and had been doing that for eight years.

So how did this level of discomfort with basic visual flying escape the schoolhouse? If Kuk’s training is anything like what we undergo in the Gulfstream, he may rarely have ever flown that kind of visual procedure in the simulator. Mostly what gets simulated are low-visibility conditions. The assumption that it’d almost be “cheating” to have visual references outside the aircraft might not have been correct. Visual approaches in the sim are typically combined with other anomalies: no-flap scenarios, windshear simulations, landing gear blow-downs, etc. But not the typical slam-dunk from a harried controller.

One wonders how many other airline pilots pale at the thought of flying a visual approach (or as the VFR pilots among us call it: landing). I know most airlines no longer allow circle-to-land procedures, but even the neophyte instrument pilot has to perform them to acceptable standards before being issued an instrument rating, and that’s infinitely more demanding than a visual approach. Instead of practicing an ILS PRM at San Francisco, perhaps we should be vectored in on one of those famously high downwinds and cleared for a visual approach from two miles up. Maybe we should train a little more like we fly.

And while we’re at it, taking a hint from that fourteen year old kid who just soloed a beat up Schweizer glider might not be so bad, either. Get out of the glass palace and into an actual airplane where there’s nothing to do except fly by looking out the window.

Mandated Spin Training

Mike Goulian - Extra 330SC

Unless you’re an instructor, practical spin training is not required by the FAA for any pilot. I’ve always been amazed by that. Even if you plan on performing spins intentionally, no training of any kind would be legally needed. Does that make sense to you?

But it gets worse. Flying a massive airliner with hundreds of people on board? No spin training required; these days, the computers will take care of everything. Stall shakers, stick pushers, and AOA probes are infallible!

Even if you are an instructor, your spin training could have been as simple as a single flight, perhaps a spin entry, a half turn of rotation, and a recovery. Call me crazy, but that seems… inadequate. My flight training experience was rather old school, consisting of tailwheels, spins, and aerobatics in stone-simple aircraft which bear little resemblance to today’s glass-infested airplanes. With all due respect to those who think I sound eerily like an 80-year old complaining about how “things ain’t how they used to be”, let me say that even a broken clock is right twice a day, so stick with me for a moment and see if you don’t agree.

There was a time when practical spin training was required for even the most basic pilot certification. Unfortunately those were the early, wild west days of flying, and I can only imagine spins weren’t approached by barnstormers with the level of forethought and consideration we typically give to those things today. As I’ve previously noted, they had a appreciable tolerance for risk back then. By the late 1940’s, conventional wisdom was that the training itself was leading to more accidents than inadvertent spins occurring in the wild.

Mandated spin training was discontinued by the Feds in 1949.

So how has this policy been working out for us? Not well, in my opinion. I’m often asked where my zeal for spin training comes from. The answer is simple: decades of accident reports. A search of the NTSB database for the word “spin” reveals 4,019 accidents — most of them fatal. That’s approximately 4,019 too many. It’s also worth noting that the database only goes back to 1962, so we can’t compare the statistics to what came before. According to the Air Safety Foundation:

Stall and spin-related accidents are among the most deadly types of GA accidents, with a fatality rate of about 28 percent, and accounting for about 10 percent of all GA accidents.

To be fair, some of the 4,019 NTSB reports referencing spins were helicopter accidents and others did not involved an aerodynamic spin. For example, a recent RV-6A accident report involved a loss of directional control on landing, leading the aircraft to “spin” off the runway. Even so, I still count nearly 20 spin-related crashes in the past twelve months. That doesn’t sound too bad when compared to the 50 year average, but keep in mind GA flying activity is down sharply (22 million fixed-wing GA hours in 2000 vs only 12 million a decade later).

Empirical evidence suggests that spin training might help avoid some of these tragedies. Unfortunately the average GA pilot doesn’t necessarily look at spins very favorably. More than any other maneuver, spins come with a long litany of baggage. Horror stories from other pilots, tall tales of spins that swallow the aircraft whole like Moby Dick, apprehensiveness about motion sickness, and so on. This requires delicate handling by those who do provide such training. Unfortunately, some still approach this using blunt force. “Just do it”. That works about as well as exposing a GA neophyte to advanced aerobatics. They run away and never return, while the bad experience only grows with each retelling over the years.

Teaching spins is not rocket science, but it must be done methodically. It’s very tempting to skip items that a more experienced pilot “ought to know”, but 99% of pilots spend 99% of their time flying straight-and-level. As a result, I’ve seen some really weird explanations from spin students about basic aerodynamics. One of the most common errors is a belief that aircraft stall at a specific speed rather than a specific angle of attack. If you’re always wings-level at 1-G, that might seem like gospel after decades of uneventful flying. If only the laws of physics would abide such misconceptions!

That’s why my spin training always begins with a thorough review of basic aerodynamics: how lift is developed, stalls, coordination, wing drops, and finally the mechanics of the spin itself. When teaching spins, the best advice for a CFI is: assume nothing.

In the air, it’s vital that the spins are worked up to slowly, beginning with stalls of various types. Remember this is not only a new activity for most trainees, but the aircraft is unfamiliar and the instructor is an unknown quantity as well. Earning the student’s trust early on allows them to focus on the spins later rather than questioning whether they’ll survive the experience. I’ve found falling leaf stalls are particularly valuable because the student must be comfortable with high angles of attack. If they gain nothing permanent from the training beyond this, it is a success, because we all must fly at high angles of attack during landing.

A quality spin training syllabus will include many things that even those who’ve got spin experience might not be familiar with: demonstrations of the difference between spins and spiral dives, drills to build confidence, techniques for assisting apprehensive students, advanced spin modes for those who take to it with greater ease, and so on.

One of the most common misconceptions about spin training is that its primary purpose is to help you recover from a spin. The truth is you aren’t terribly likely to encountering one inadvertently. If proper coordination is maintained (and it’s often not — that is why we have these stall-spin accidents), few pilots will encounter one in the heat of battle. No, the best reason for teaching spins is to eliminate fear of the unknown. Such fears can be debilitating at a moment when the pilot can least afford to be indecisive. The same can be said of upset recovery courses.

I’ll take it a step further and state that many landing accidents are caused by a lack of spin training. What does one have to do with the other? Students who are afraid of spins will be afraid of deep stalls. It’s only natural to fear the unknown. Those wing drops can be scary if you don’t understand what’s causing them, what will happen if you don’t correct properly, and how the resulting spin entry should be handled. A fear of stalls means they’ll be apprehensive about high angles of attack and low airspeeds. So they approach the runway with too much energy just to be on the safe side, with predictable results.

With all that in mind, it astounds me that the FAA proclaims spin training as unnecessary. I see people every day who have had no spin training and their flying is often marked by poor rudder skills, limited understanding of the related aerodynamics, and a lack of appreciation for the importance of coordination.

That’s the benefit of spins, and the reason I feel strongly it should be mandated as a central part of primary training. The stick-and-rudder skill deficiencies in today’s pilots didn’t start today. It began years ago when they were learning how to fly. Fixing it will require a journey into the past. It’s time to get back to basics, and you won’t cover all the bases unless spin training is a central part of the mix.

See & Avoid: Does It Work?

midair

Contemplate the worst scenario that might confront a pilot during a flight. What comes to mind? Fire? Flight control failure? Engine failure? Perhaps it’s flight crew incapacitation, explosive decompression or severe structural damage.

No doubt about it, those all fall into the Very Bad Day category. But there’s one that can be even worse: a mid-air collision. That’s because it can involve all the problems listed above — at the same time. And since the parties involved aren’t aware of the impending crunch until it’s too late, the mid-air is usually accompanied by a violent element of surprise, confusion, and initial denial.

You might think fatal mid-airs are rare events, and from a purely statistical standpoint I’d have to agree. According to the 2010 Nall Report, a fatal mid-air occurs about once every 8 million flight hours. Think of it as the roughly the same odds as winning the lottery or being struck by lighting. Doesn’t sound so bad, does it? A typical GA pilot might accumulate but thousand or so hours over a full lifetime of flying.

So what’s there to worry about? Plenty. The “big sky” theory may sound good, but it doesn’t hold up very well under close scrutiny. It’s true that the navigable atmosphere over the United States alone is massive — about 20 million cubic miles — and there are relatively few airplanes in the sky. Even on those occasions where a collision is possible, modern tools such as radar, TCAS, VHF communication, and anywhere between two and four sets of eyeballs almost always succeed in averting the disaster. If aircraft were equally distributed throughout the atmosphere, the “big sky” idea would be pretty comforting.

But airplanes cluster near airports, large cities, and on thin slices of the sky known as “airways”. For the VFR types, airspace and terrain often crowd planes into small swaths of the air in places like the Santa Ana Canyon or Banning Pass. The sky is much like the ground: vehicles stick to relatively confined spaces and that makes collisions a serious hazard.

Mid-airs are nothing new.  This B-17 collided with a German fighter over Tunisia in 1943.

Mid-airs are nothing new. This B-17 collided with a German fighter over Tunisia in 1943.

Since we’re on the topic of statistics, let me give you a few of my own: I personally know two people who have been struck by lightning, and a winning lottery ticket was recently sold not 300 feet from my front door. Hey, crazy stuff happens. But unlike lighting strikes and golden tickets, we’re not all facing the same odds. The risk profile varies widely depending on the type of flying you’re doing.

For example, flight instruction is frequently a factor; thirty-seven percent of mid-airs occur with a CFI on board. Many instructional flights happen near airports, and as previously mentioned, that’s where other airplanes tend to congregate. On the other hand, if you fly airliners, your risk of a mid-air is rather low because the aircraft itself is large and easy to see, you’re always flying IFR, and the most sophisticated traffic avoidance hardware available is always installed. Airliners also spend most of their time in cruise and are in constant radar contact with ATC.

Think it can’t happen to you? Think again. Some very talented, capable, and well-respected pilots have been involved in mid-air collisions. I know a guy who was involved in one while flying a large-cabin, TCAS-equipped business jet under Instrument Flight Rules. Alan Klapmeier, the founder of Cirrus Aircraft, was in one too. Richard Collins, famed Flying columnist, was in a mid-air. Speaking of Flying, the current Editor-in-Chief owns a very nice Cirrus SR-22 which was recently in a mid-air. And lastly, a decade ago I was in a mid-air collision myself.

I’ll save the blow-by-blow (no pun intended) on that for another day. The point I’m trying to make is that the odds of a mid-air are probably greater than you think, especially if you live in a populated metropolitan area and fly VFR. If you’ve ever had a close encounter with another airplane in flight, you were only separated from “those who have” by nothing more than a miniscule sliver of plain old luck.

Think about that for a moment.

This may be hard to believe, but there is some good news. For one thing, mid-airs are not always fatal. It seems intuitive that most collisions would involve fatalities, but all the people I cited above survived, including (obviously) myself. Also, technology is rapidly advancing, from cheap TCAD boxes to airframe parachutes to super-bright LED exterior lighting.

It can happen anywhere.  These two aircraft, an Arrow and a TriPacer, collided in Idaho recently.

It can happen anywhere. These two aircraft, an Arrow and a TriPacer, collided in Idaho recently.

The question we should all be asking ourselves is how we avoid ending up in a mid-air, fatal or otherwise. If you refer to official guidance from the FAA, the answer is to simply look out the window and spot the other airplane before it hits you. This technique, referred to as “see and avoid”, is still considered adequate for preventing collisions. Here are a couple of passages from Chapter 1 of the Airplane Flying Handbook:

The “See and Avoid” concept relies on knowledge of the limitations of the human eye, and the use of proper visual scanning techniques to help compensate for these limitations. The importance of, and the proper techniques for, visual scanning should be taught to a student pilot at the very beginning of flight training.

Proper clearing procedures, combined with proper visual scanning techniques, are the most
effective strategy for collision avoidance.

Other FAA publications, ranging from the Aeronautical Information Manual, to Advisory Circulars like AC-90-48 (“Pilot’s Role in Collision Avoidance”) will give you the same spiel: “see and avoid will keep you safe”. And it will! Until it doesn’t.

From my perspective as someone who’s been in a mid-air and who was using proper clearing and scanning techniques at the time, I take it as gospel that “see & avoid” won’t always do the trick. I’m just one guy, of course. But many others — some institutional in nature — just happen to agree with me.

For example, Canada’s Transportation Safety Board recently issued an accident report on a mid-air collision between a Beech V-35B Bonanza and a PA-28 Cherokee over northern Virginia. Canada was tasked with performing the investigation because the pilots of the Bonanza were employees of the NTSB while the Cherokee was piloted by an employee of the FAA.

I won’t keep you in suspense. The conclusion from the TSB was that the “see and avoid” concept was inadequate. They even quoted a 1991 report produced by the Australian Transport Safety Bureau which provides an overview of the major factors that limit the effectiveness of the see-and-avoid principle in preventing mid-air collisions, as well as a 2005 scientific study published in Aviation, Space, and Environmental Medicine which came to the same conclusions.

The main points:

  • Cockpit workload and other factors reduce the time that pilots spend in traffic scans, and even when pilots are looking out, there is no guarantee that other aircraft will be sighted.
  • Visual scanning involves moving the eyes in order to bring successive areas of the visual field onto the small area of sharp vision in the center of the eye. The process is frequently unsystematic and may leave large areas of the field of view unsearched.
  • A thorough, systematic search is not a solution as in most cases it would take an impractical amount of time.
  • The physical limitations of the human eye are such that even the most careful search does not guarantee that traffic will be sighted.
  • The pilot’s functional visual field contracts under conditions of stress or increased workload. The resulting ‘tunnel vision’ reduces the chance that an approaching aircraft will be seen in peripheral vision.
  • The human visual system is better at detecting moving targets than stationary targets, yet in most cases, an aircraft on a collision course appears as a stationary target in the pilot’s visual field.
  • An approaching aircraft, in many cases, presents a very small visual angle until a short time before impact.
  • Complex backgrounds such as ground features or clouds hamper the identification of aircraft via a visual effect known as ‘contour interaction’. This occurs when background contours interact with the form of the aircraft, producing a less distinct image.
  • Even when an approaching aircraft has been sighted, there is no guarantee that evasive action will be successful.
  • Because of its many limitations, the see-and-avoid concept should not be expected to fulfill a significant role in future air traffic systems.
  • Transportation Safety Board of Canada aviation investigation report A06O0206 identified that there is a high risk of mid-air collisions in congested airspace when aircraft are not alerted to the presence of other aircraft and rely solely on the see‑and-avoid principle.

There’s one more area of the TSB report which is worth of quotation. In it, they reference a British Royal Air Force study into mid-air collisions. If you’re keeping score, that’s the third sovereign agency to reach the conclusion that “see and avoid” is inadequate. Yet our own FAA, which oversees about 80% of the world’s aircraft and almost all of the high traffic density airspace, still officially proclaims that one can look out the window and see everything that needs to be seen.

This accident has demonstrated yet again that relying solely on the see-and-avoid principle to avoid collisions between aircraft operating under visual flight rules (VFR) in congested airspace is inadequate.

A number of international studies have addressed the overall issue of the effectiveness of the see-and-avoid principle, as well as the risks of collision associated with this principle. All acknowledged the underlying physiological limitations at play and that, when mid-air collisions occur, “failure to see-and-avoid is due almost entirely to the failure to see.”

One study stated that “our data suggest that the relatively low (though unacceptable) rate of mid-air collisions in general aviation aircraft not equipped with TCAS [traffic alert and collision avoidance system] is as much a function of the ‘big sky’ as it is of effective visual scanning.”

A British Royal Air Force study into mid-air collisions, which were deemed to be random, found that the probability of conflict is proportional to the square of the traffic density, and recommended avoiding altitude restrictions that concentrate traffic.

Measures such as improving aircraft conspicuity, pilot scanning techniques, and pilot traffic awareness can reduce risks, but they do not overcome the underlying physiological limitations that create the residual risk associated with a see-and-avoid method.

It’s obvious that “see and avoid” cannot, by itself, ensure our safety. If it could, there’d be no need for TCAS or most of our controlled airspace (both of which came about because of high-profile mid-air collisions, I might add!). I’m not necessarily in favor of mandating any additional equipment, airspace, or restrictions, especially on general aviation. But it’s clear that serious changes are needed in how collision avoidance is taught, especially as it concerns “see and avoid”. The concept has serious limitations which must be understood so the pilot-in-command can make educated decisions about how — or even if — they want to mitigate those risks.

Unfortunately, we cannot turn back the hands of time. The fatal collision between the NTSB and FAA employee aircraft is now part of the past. Those involved will think about it almost every day for the rest of their lives. Want to guess how I know that?

I sincerely hope our nation’s regulatory and safety organizations will finally learn the lesson of that sad day by officially acknowledging what we all know to be true: “see and avoid”, while a good start and certainly a vital part of collision avoidance, is simply not sufficient to ensure traffic separation.