The Spin Debate
If spins can kill, why aren't pilots trained to handle them?
- By Joseph Bourque
- Air & Space magazine, November 2003
NASA Langley Research Center
IMAGINE YOU'RE FLYING A LEFT-HAND APPROACH to the local airport. you're on the base leg, perpendicular to the runway, with its near end at your left front quarter as you bank into the left turn for the final leg. Halfway into the turn, you realize that a cross-wind is pushing you beyond the centerline, so you bank a little more. When it’s clear that won’t be enough to realign you properly with the runway, you kick in some extra left rudder to move the tail around, but that increases the bank angle. Your instructor has beaten into your head that you never make steep turns close to the ground, so you instinctively do what you always do to bring the left wing up: You turn the wheel to the right. To your surprise, the left wing dips further, so you turn the wheel still further to the right.
You have just made a classic mistake.
Suddenly the right wing flips up over the top, and the nose swings toward the ground as the airplane starts spinning. Since your altitude turning final is only 300 to 400 feet above ground level (AGL), do you have room to recover? I never asked myself that question when I was training for my private pilot’s license many years ago. My instructor, who believed in spin training even though it was not mandated by the Federal Aviation Administration, took me to a generous 4,000 feet AGL and demonstrated how to force the airplane into a spin and how to recover. Then he had me do two one-turn spins to the left and two more to the right. It was exhilarating! I was good at it! Patting myself on the back, I declared myself proficient. Unexpected spins at low altitude were a dimly recognized and easily dismissed possibility.
I’ve learned a lot since then.
I did a search of the National Transportation Safety Board’s records and found that since January 2001, there have been more than 80 stall/spin accidents in general aviation in the United States. And last year, Pat Veillette, an instructor in the personnel training department of a major air carrier, did a formal study of the NTSB’s records and found that between 1994 and 2000, there were 394 spin-related accidents in this country. Fatal accidents numbered 324, including one on May 25, 1997, when a Cessna 205 crashed in Homestead, Florida, during a skydiving outing, killing all but one of the seven persons on board. The NTSB accident report reads in part: “A passenger-parachutist stated she had exited the cabin and was on the jump platform preparing to jump from about 3,500 feet when the left wing and nose dropped and the aircraft entered a spin to the left. After an unknown number of revolutions she jumped from the aircraft and deployed her chute. She observed the aircraft continue in a spin until ground impact.”
The NTSB determined the probable cause of the accident: “The pilot-in-command’s failure to maintain airspeed as he slowed for a parachutist to jump from the aircraft, and his failure to apply spin recovery emergency procedures prior to ground impact. Contributing to the accident was the pilot-in-command’s lack of training in spin recovery emergency procedures in an aircraft.”
Accidents like this one further a debate that has divided the aviation community since 1949, when the Federal Aviation Administration eliminated from the syllabus for a private pilot’s license the requirement for spin training. John Wensel, manager of the FAA’s Certification Branch, General Aviation and Commercial Division, Flight Standards Services, recounts his agency’s reasoning: “We saw that 48 percent of the fatal accidents from that era involved stall/spin, and of those the majority were training-related. We were killing people in trying to eliminate the very thing that was happening to them.” A number of general aviation pilots, however, think that the requirement for spin training should be reinstated. Their reasoning: Everything about flying takes practice. How can a pilot possibly recover from something as disorienting as a spin if the first encounter is an unexpected one?
Inadvertent spins are dangerous because they are disorienting. Imagine you are in a car suspended by a rope around its rear bumper. The other end of the rope is attached to a flagpole jutting out from a very tall building, so you sit staring straight at the concrete far below. Someone starts the car moving in a circle while simultaneously turning on its own axis as the car’s front end starts pitching from side to side. Now someone cuts the rope. That’s what it feels like to be in a spin.
In the earliest days of flying, a spin was certain death, but beginning in 1912, a smattering of pilots somehow extricated themselves from spins. Mathematician F.A. Lindemann is most often named as the first to have developed an aerodynamic theory of spins and a procedure for recovery. He learned how to fly and tested both the theory and the procedure himself in 1916. The method of spin recovery now described in modern flight manuals, known as PARE, is no more than a mild refinement of Lindemann’s.
PARE is an acronym developed by flight instructor Rich Stowell to help pilots remember the sequence of control inputs necessary for a spin recovery: Power (close the throttle), Ailerons (neutralize), Rudder (full deflection in direction opposite the spin), Elevator (first, stick forward to un-stall the wing). An alternative is the Muller-Beggs method, which is similar to PARE with one dramatic exception: for PARE’s “neutralize ailerons” phase of recovery it substitutes “take your hands off the stick.” Neither of these methods is guaranteed to work for every airplane in every situation.
I needed to refresh my memory about PARE, so I sought out aerobatics instructor Adam Cope, who flies a Super Decathlon out of tiny Potomac Airfield, just outside of Washington, D.C. Cope is a born teacher. He may look young, but he knows his aerodynamics and excels at clear and sensible presentation. We first review the basics with his dog-eared charts. Figure 1 illustrates the most basic principle: As long as air flows smoothly over the wing, the wing will produce lift. As the wing’s angle of attack increases, air flowing over the top of the wing begins to detach from the wing, and with each increase in the angle of attack, the point of detachment moves closer to the wing’s leading edge. At some stage, which is different for each airplane, lift will no longer be sufficient to sustain the weight of the aircraft: That configuration of the wing with respect to the relative wind is called the critical angle of attack. Figure 2 demonstrates that a wing moving through the air produces both lift and drag. As the angle of attack increases, lift and drag both increase proportionately. At the critical angle of attack, however, lift drops dramatically while drag continues to increase. The result is a stall. A spin occurs when one wing stalls more sharply than the other, generally as a consequence of exceeding the critical angle of attack in connection with yaw (movement around the aircraft’s vertical axis).
In the air in his Super Decathlon, Cope has me do a few aerobatic maneuvers to get me used to employing the rudder, which will help control the airplane during spin recovery. Cope has prepared me intellectually, but no ground school can prepare you for the abruptness with which an airplane flips over, nor did I retain a memory of that shock from my training years ago. We do only two turns on the first couple of tries and I am able to recover adequately, but then we graduate to four- and then six-turn spins. As the number of turns mounts, the spins get tighter and faster. At four turns, I’m experiencing nystagmus—the eyes rapidly oscillate from side to side as they attempt to establish a point of reference. Consequently, when Cope tells me to recover, I perform the PARE sequence, but I’m unable to distinguish when the rotation stops, so we nearly fall into a spin in the opposite direction. Though I am too busy to detect it, I suspect that Cope is nudging the stick to keep me from getting into too much trouble. It becomes clear to me that without regular practice, I would not likely survive a spin if I allowed it to develop into more than three or four turns.
But the debate centers on whether spin training would improve pilots’ chances of avoiding inadvertent spins in the first place, and, if a spin should occur, would spin recovery training improve the pilots’ chances of survival. To understand that debate, some background is necessary. When the FAA eliminated the requirement for spin training in 1949, it shifted the burden of responsibility to the aircraft manufacturers, to some degree, by stating that airplanes should be made more spin-resistant. But while the FAA wanted more spin resistance, customers demanded airplanes that could perform, and at the time, those were somewhat incompatible goals: Increasing spin resistance necessitated a loss in aircraft performance—generally losses in speed and fuel efficiency.
Whatever spin resistance was built into general aviation aircraft manufactured before the 1990s was largely an accidental byproduct of other design considerations. A few craft were quite spin-resistant, but most were not, and some had unrecoverable spin modes, even after the FAA began requiring manufacturers to demonstrate that their craft could recover from a one-turn spin. Additionally, we now know (though it was not common knowledge until the late 1980s) that anything you do to improve spin resistance has the unfortunate side effect of increasing the difficulty of recovering from a spin. Unless you could produce a spin-proof aircraft, the tradeoff was a risky one.
So while the general trend over the years was for aircraft to be somewhat more spin-resistant because engineers were learning to design better airplanes, the high accident rate from stall/spin accidents clearly demonstrated that aircraft built before the 1990s did not meet the FAA’s goal for spin resistance.
At this point, it must be said that nearly everyone is in favor of spin training, even the FAA, as long as it’s not required. Says the FAA’s Wensel: “The FAA doesn’t prohibit spin training. That’s why we require CFIs [certified flight instructors] to undergo spin training, so they can pass that on to their students if either the instructor or the students wish that training to take place.” Warren Morningstar, vice president of communications for the Aircraft Owners and Pilots Association, says his organization agrees with the FAA’s position.
When the online publication AvWeb (www.avweb.com) informally surveyed its readers two years ago, however, it found that of 1,186 responding to the question of whether spin training should be required for a private pilot’s license, 57 percent said yes and another 36 percent said it should be encouraged but not required. Only seven percent of respondents said spin training should not be required.
Aerobatic pilot Tom Alison, a retired U.S. Air Force SR-71 pilot and head of the National Air and Space Museum’s artifact restoration division, is an advocate of spin training for private pilots. “I believe that a pilot should understand and not fear the spin,” he says. Alison, who has witnessed even experienced pilots employ incorrect methods to get out of a spin, says: “Exposure to the spin maneuver and experience in all its aspects—entry, recognition of various spin modes, and appropriate recovery procedures—is the only way a pilot can really master this aspect of aviation.”
“A spin is a very dangerous situation to find oneself in,” says private pilot Bob Curran, who flies a Bellanca Citabria. “To the untrained pilot, what may seem the logical method of exiting a spin will instead result in perpetuating the condition, perhaps making it worse. There are few things in flying that can result in a more rapid loss of altitude or overwhelm the thought process of an unskilled pilot than entry into an inadvertent spin.”
When Curran went through spin training, his flight instructor had thoroughly briefed him on what to expect and had rehearsed the recovery procedure with him. Still, Curran’s first spin was a “shocking experience even though it was fully intentional,” he says. “To this day, I still practice spin recovery on a regular basis.”
In 1976, the FAA published the results of a study (FAA-RD-77-26: “General Aviation Pilot Stall Awareness Training Study”) that were the justification for its policy that teaching people to avoid spins in the first place is a better means of saving lives than teaching people to get out of them. That policy was further refined in 1991 (Advisory Circular 61-67B) and in 2000 (61-67C), but not fundamentally changed. Statistics seem to support the FAA’s judgment. The 1976 report states: “More fatal and serious injuries have occurred from stall/spin accidents involving general aviation aircraft than from any other single type of accident.”
In 1980, U.S. Congressman Jim Lloyd of California held three days of hearings before the House committee on science and technology, subcommittee on investigations and oversight. The topic was whether spin recovery training should be a requirement for a private pilot’s license. The FAA representative at the hearings, Bernard A. Geier, restated his agency’s case for teaching pilots spin avoidance, and emphasized the importance of altitude data. “As a matter of fact,” he testified, “analysis of stall/spin accident data indicates that only seven percent of stall/spin accidents occur at altitudes where a spin-proficient pilot could effect complete recovery.” William Stanberry, senior vice president of the Aircraft Owners and Pilots Association, agreed with the FAA, as did J. Lynn Helms, chairman of Piper Aircraft Corporation and chairman of the General Aviation Manufacturers Association. The hearing’s other 13 witnesses all testified in favor of spin training, including Elwood Driver, vice chairman of the National Transportation Safety Board; Verne Jobst, director of both the International Aerobatic Club and the Experimental Aircraft Association; James M. Patton, chief of flight operations at NASA’s Langley Research Center in Virginia; and former X-15 test pilot Scott Crossfield, serving as a technical consultant for the House. The committee recommended that spin training be required. The FAA refused.
As a result of those hearings, retired test pilot Tony LeVier, with Crossfield’s help, started S.A.F.E. (Safe Action in Flight Emergencies), a program to promote spin and emergency maneuvers training. Today Crossfield recalls: “Tony and [former U.S. senator and military pilot] Barry Goldwater and I, and Sammy Mason and Bob Finch started an organization called S.A.F.E. We gave scholarships from donations given by other aviators.” Mason did the flight instruction while LeVier and Crossfield raised the money.
Rich Stowell and CP Aviation restructured Mason’s program into their emergency maneuvers training program, giving instruction out of Santa Paula Airport in California, where, over the years, Mason had taught about 800 S.A.F.E. students. Stowell was the first person that the National Association of Flight Instructors ever designated a Master Certified Flight Instructor—Aerobatic, and in his career he has performed more than 23,000 spins. He is a firm believer in the benefits of spin recovery training. However, he warns that student pilots shouldn’t overestimate the training that CFIs normally get: two or three entries in each direction. Not enough for proficiency, he says.
In an article published in the May 2002 issue of Aviation Safety, Pat Veillette wrote: “Almost one fifth of the spin accidents [in Veillette’s 2002 study] involved a flight instructor. More than a decade ago, I did a study of stall/spin accidents that was published by the National Research Council. Among its findings were the lack of standardization and quality control of flight instructor candidate preparation, particularly in regard to stall/spin knowledge and preparation.”
Veillette’s study also shows that many of the stall/spin accidents in his sample were due to errors by highly experienced fliers. Of the pilots involved in accidents, 13 percent were certified aerobatic competition pilots, 27 percent had previous spin training, and nearly a fifth were CFIs. Clearly, extensive experience far from guarantees success in the confusion of an unexpected spin, but a significant number of spin accidents still befall less experienced pilots.
When are spins likely to occur? Many happen around airports—when aircraft are accelerating or slowing. On February 14, 1997, a pilot carrying four passengers in a single-engine Piper PA-24-250 Comanche took off from the airport in Farmington, New Mexico, at night. During the initial climb, observers saw the Piper stall, enter a spin, and hit the ground in a nose-down attitude; all aboard were killed. And on May 31, 2000, a recently certificated flight instructor and his passenger/student were turning to final approach at Palm Springs, California, in a Cessna 152. The air traffic control tower requested that the Cessna make a series of S-turns to maintain proper spacing between it and an aircraft waiting to start its takeoff roll. Witnesses observed the Cessna’s wings rock right and left before the craft stalled and spun to the ground from 250 feet; both pilot and student were killed. The NTSB determined probable cause to be the failure of the pilot/flight instructor to maintain sufficient airspeed.
Some pilots disagree with the FAA’s contention that the altitudes typical of takeoff and landing are too low to allow for spin recoveries. Says Scott Crossfield: “When I was an instructor in the Navy, I had a student in an SNV who put me on my back on final approach. I was half asleep back there, but because I’d had good spin training, I managed to roll that thing all the way around just before it landed and
didn’t even hurt it.” Though few of us can aspire to Crossfield’s skill, many of us believe that a properly spin-trained pilot could recognize the problem quickly enough to recover in a quarter-turn or half-turn, perhaps making the difference between death and survival. Says Crossfield: “It should become almost instinctive that you pump in rudder against the spin, and most of the time that will catch that wing.”
Verne Jobst is still a director at the Experimental Aircraft Association and was inducted into the Flight Instructors Hall of Fame in 1999. He is also a pilot examiner. He has not changed his mind a bit since he testified before Congress in 1980. Jobst believes that many certified flight instructors are not qualified to teach spins. “Instructors mostly get their three entries to the left and three entries to the right, and that’s it,” he says. “There are many instructors who—though I doubt they would admit it—don’t even get the minimum required. Their instructors just sign them off.” Jobst says that in his career as an examiner, he has encountered several.
Jobst tells a story about one of his students: “He was sort of manhandling the airplane and slowing it up and slowing it up. And sure enough it let go. He threw his right hand up past my head. Luckily I ducked or I wouldn’t be here talking to you today. His hand flung out and he yelled, ‘You got it!’ So when I recovered he said, ‘What was that?’ I said, ‘It’s a spin.’ That convinced him to get spin training. Had he been alone with that first spin, he would likely be dead.”
Jim Patton is unequivocal, as he was in his 1980 testimony. “Certainly pilots should know how to recover from a spin,” he says. “Like buying an insurance policy. If the first time you go into a spin is inadvertent, especially if you’re at pattern altitude, then it’s too damned bad because you’re not going to do the right thing. The problem is that instructors are given only a once-in-a-lifetime exposure to spins. They should have to remain current in spin recovery.” Patton has a unique perspective on spins: He was chief pilot for a stall/spin research program conducted at NASA’s Langley Research Center from 1977 to 1987. Before that he had been an FAA test pilot, testing, among others, two aircraft known to have unrecoverable spin modes. The original intent of the FAA study was to examine the aerodynamics of a spin. By the time the study ended, Patton and his investigators had progressed to developing efficient methods of building spin resistance into general aviation aircraft.
For the NASA experiments his group acquired four general aviation aircraft that they modified radically to examine how changes to the standard airframe would affect spin characteristics. “The goal was to determine what was happening with spins, at least at first,” Patton says. His test flights with various aircraft modifications soon indicated that very small changes to the wing would produce huge differences in performance. “With simple changes to the wing we could change an airplane that flew like a kiddie car into a tiger that would eat you up,” he recalls. Thus came the realization that, with slight modifications, an airplane could be produced that was even more resistant to spins. The experimenters could say: “Hey, this is a very safe airplane. Not spin-proof, but it gives plenty of warning, lots of buffet, very little roll-off laterally—a long period of telling the pilot ‘Hey, you’re doing something wrong.’ ” In fact, a new generation of aircraft, particularly Lancair and Cirrus, use wing leading edge cuffs that were pioneered in Patton’s program. The cuffs, which improve the stall characteristics of an aircraft with only a negligible reduction in its performance, increase the radius of the wing’s leading edge and are attached so that there is a disruptive edge between the cuff and the wing itself. The effect of the cuff is to keep a stall from progressing from the inboard section of the wing to the outboard section.
Both the General Aviation Manufacturers Association and the FAA also believe in the importance of increasing the spin resistance of aircraft. In fact, the FAA argues that newer airplanes are less spin-prone, so there is less need for spin training. For that reason, Russell Lee, a private pilot and aeronautics curator at the National Air and Space Museum, thinks that obtaining a private pilot’s license should not require spin recovery training. He feels that many modern training-level and entry-level aircraft behave so well when operated according to the flight handbook that spin training to fly these airplanes is not necessary. “I think that in the vast majority of mainstream aircraft to which private pilots have access, there are simply too many clues designed into the aircraft to tell the pilot that he is headed for a spin,” says Lee. “Decaying airspeed is signalled not only by several instruments, but by a drop in wind noise and a drop in control pressures. Then there is pitch attitude change and stall warning—and all this happens before the airplane actually stalls. Most [modern training aircraft] types must then be held in the stall for some seconds to even fall off on a wing. To enter a genuine, full-rotation spin requires, in my experience with entry-level aircraft, aggressive use of pro-spin control movements such that the pilot has to purposely force the aircraft to spin.”
Lee has himself gone through spin training, and he says that it has made him a “better pilot, more prepared for unusual attitudes due to turbulence.” Though he doesn’t think spin training is necessary for beginning pilots, he does believe that once pilots graduate from entry-level aircraft to high-performance ones, they should get full spin training, or else they are putting themselves and those around them at risk.
Though new aircraft designs improve spin resistance, there are pilots still flying thousands of aircraft with less spin resistance, and some of them are going to find themselves in deadly spins. The real question is whether any of these lives might be saved by spin entry and recovery training. The FAA’s 1976 study sends a mixed message, so perhaps it’s time for a new study with a larger, more statistically valid sample. In the meantime, I’ll go spin every now and then, learn all I can, and try to avoid being the one who makes that fatal mistake.