Stall/spin myths exploded
Pilots who believe that
aerobatic training will enable a recovery from an inadvertent spin in the
traffic pattern are fooling themselves. That myth - and other misconceptions
about stalls and spins in GA aircraft - is exploded in this new ASF study. This
study is not intended to discount the value of properly conducted aerobatic and
spin training. Training in a controlled environment with a trained instructor is
beneficial. The most important aspect of the training should be recognition and
Stall/spin accidents tend to be
more deadly than other types of GA accidents, accounting for about 10 percent of
all accidents, but 13.7 percent of fatal accidents. Overall, around 20 percent
of all GA accidents result in fatalities, but stall/spin accidents have a
fatality rate of about 28 percent.
This study looked at 450 fatal
stall/spin accidents from 1993 to 2001 involving fixed wing aircraft weighing
less than 12,500 pounds. Stall/spin crashes accounted for 10% of all accidents
and 13.7% of all fatal accidents.
Why the constant reference to
"stalls/spins" instead of separating the two manoeuvres? A spin is an aggravated
stall but the aircraft behaviour, recovery procedure, and the altitude loss is
quite different between stalls and spins. However, many accident reports
conclude that the cause of an accident was a result of an 'inadvertent
stall/spin' with no additional clarification. Because most light GA aircraft do
not have flight data recorders, and there may be no reliable witnesses, it is
often impossible for the investigator to precisely determine the aircraft's
flight condition prior to impact.
These accidents are more likely
to be fatal (on average, 28 percent of stall/spin accidents are fatal compared
to other types of GA accidents (20 percent with fatalities). The higher
likelihood of fatalities in stall/spin accidents is due largely to crash
dynamics. If an aircraft strikes the ground in a normal landing attitude and can
dissipate the crash energy over even as little as 100 feet the chances of
fatality, assuming no fire, decrease significantly. However, if the impact
occurs nose down, at a high rate of descent which is typical of stall/spin
scenarios, the G forces tend to be much higher, the aircraft does not slide much
and there are resulting fatalities.
Aircraft type major factor in
Single engine fixed gear (SEFG)
aircraft are the types most often involved in stall/spin accidents, by a wide
margin. Pilots of such aircraft don't necessarily need to be alarmed, however;
the high number of stall/spin accidents in SEFG has less to do with the aircraft
type than the fact that SEFG aircraft are frequently used in training and are
likely to spend more time in manoeuvring flight and the traffic pattern.
Cross-country aircraft, such as single engine retractable gear aircraft (SERG)
and twins (Multi) are less likely to be involved in this type of accident.
Student pilots, ATPs least
likely to stall/spin
Student pilots are, by far, the
least likely to suffer stall/spin accidents, as a proportion of in the
pilot population. Pilots holding FAA Airline Transport Pilot (ATP) certificates
are also less likely to stall/spin.
That leaves pilots with FAA
private and commercial pilot certificates in the "most likely to suffer fatal
stall/spin accidents" category. In fact, commercial pilot certificate holders
are by far most likely to show up in the stall/spin accident statistics, again
based on the proportion of their representation in the pilot population. (See
So why do the least experienced
and most experienced pilots enjoy the best safety record, at least when it comes
to fatal stall/spin accidents, while the rest of us - the bulk of GA pilots - do
so poorly? Based on the number of certificates issued, it appears that ATPs are
generally the most experienced and knowledgeable pilots, while students are
under very close supervision to ensure their safety.
Some commercial and private
pilots, on the other hand, may have grown complacent in their skills, or lack
proficiency or understanding in aircraft operations at the corner of the flight
envelope. It may also be that a little knowledge is a dangerous thing.
Student pilots aren't usually
very far into the private pilot curriculum before stall training is started.
(Spins were deleted from the requirements for a private pilot certificate in
June 1949, and the accident rate from spins has been decreasing ever since. This
doesn't mean that you shouldn't receive spin training but understand that if an
inadvertent spin occurs at low altitude, recovery is unlikely, even with
Trouble in the pattern
Until 1949, private pilot
applicants were required to demonstrate spins, so spin training was a routine
part of the private pilot curriculum. In June of that year, the CAA (predecessor
of today's FAA) removed the requirement for spin training for private pilots,
substituting increased training in stall recognition and recovery, since spins
cannot occur without a stall. (A requirement for instructional proficiency in
spins remains today only for flight instructor candidates).
Officials at the time also
reasoned that if there was no spin requirement for private pilots, then aircraft
manufacturers would also be encouraged to produce aircraft with greater
Removal of a spin requirement
for private pilots created much dissent on the part of instructors and other
aviation professionals, who forecast an immediate and dramatic rise in the
number of spin accidents. It didn't happen. In fact, since elimination of the
spin requirement for private pilots, the incidence of stall/spin accidents has
actually decreased substantially.
Following the U.S. lead, Canada
and the United Kingdom dropped spin demonstrations for non-CFI check rides for
the same reasons.
Although the total number of
stall/spin accidents has dropped dramatically since 1949, those that do still
occur tend to occur at fairly low altitudes. In fact, a 2001 ASF study on 465
fatal stall/spin accidents that occurred from 1991 through 2000 showed that at
least 80 percent (and probably more) of the accidents started from an altitude
of less 1000 feet agl, the usual traffic pattern altitude.
The study found that only 7.1
percent of the aircraft involved in the stall/spin accidents definitely started
the stall/spin from an altitude of greater than 1,000 feet agl. Just over 13
percent of the aircraft were reported at an "unknown" altitude at the beginning
of the accident, and so were given the benefit of the doubt by ASF.
Another study done earlier by
the FAA Small Aircraft Directorate, which included some 1,700 stall/spin
accidents dating from 1973, concluded that 93 percent of such accidents started
at or below pattern altitude (pattern altitude at many airports in the 1970's
was often 800 feet agl, adding emphasis to the study findings).
The altitude required for
recovery from stalls is minimal compared to that required for recovery from
spins, even when experienced aerobatic test pilots are on board and ready to
recover from the spin.
Pilot Operating Handbooks for
various typical GA aircraft estimate average altitude loss during stalls,
assuming proper recovery technique, as between 100 and 350 feet.
Altitude loss in spins is
But recovery from a spin is a
far different matter, and takes much more altitude, even with skilled pilots. A
NASA study done in the late 1970s proved that the average altitude loss in spins
done with a Grumman American AA-1 (Yankee) and a Piper PA-28R (Arrow), two
popular single-engine aircraft, was nearly 1,200 feet. (It should be noted that
neither aircraft is approved for spins, but NASA was testing them for possible
improvements in spin handling characteristics.)
In the Yankee, it took an
average of 210 feet for entry, 340 feet for stopping the turn, and another 550
feet for recovery, for a total of 1100 feet. In the Arrow, the figures were 140
feet for entry, 400 feet for stopping the rotation, and 620 for recovery, for a
total of 1160 feet.
In short, the average vertical
recovery distance was just short of 1200 feet. Pilots allowing a spin to develop
at or below traffic pattern altitude are nearly certain to crash, no matter how
quick their reflexes or skilful their recovery.
Stall/Spins mostly likely
during manoeuvring flight
Fatal stall/spin accidents
generally occur during manoeuvring flight (40.2%) or takeoff (28.8%).
Manoeuvring flight is loosely defined, but usually includes any type of flight
where a pilot is using the aircraft's flight controls to perform manoeuvres not
necessary for straight-and-level flight.
Many pilots commonly associate
manoeuvring flight with unauthorized low-level flight such as "buzzing," but
other types of manoeuvring flight might include low-level pipeline patrol,
banner-towing, aerobatics, or even normal air work in the practice area. The
NTSB defines manoeuvring flight to include all of the following: aerobatics, low
passes, buzzing, pull ups, aerial application manoeuvres, turns to reverse
direction (box canyon type manoeuvre), or engine failures after takeoff with the
pilot trying to return to the runway.
An instructor on board is no
In reviewing 44 fatal stall/spin
accidents from 1991 - 2000 and classified as instructional, ASF found that a
shocking 91%(40) of them occurred during dual instruction, with only 9% (4) solo
training flights. Of the fatal instructional accidents, 64.4% of them occurred
during manoeuvring, and 17.8% of them occurred during takeoff.
Obviously instructors must be
proficient in stall recovery, and if not current in spins, prevent the aircraft
from entering the spin regime. Many instructors have not practiced a spin
recovery since receiving their spin endorsement, which may have been many years
ago. On the other side of the cockpit, instructors should monitor students
closely when they are practicing stalls. If the student inadvertently spins the
aircraft, can they safely recover?
According to the 2002 ASF Nall
Report, takeoff accidents (including those that result in a stall/spin) are much
more likely to be fatal than landing accidents.
Aircraft are not created equal
Aircraft design is the primary
factor in how an aircraft will behave in a stall or spin. All aircraft must meet
FAA certification standards for stalls and in some cases, spin recovery. Not all
aircraft are approved for spins and may become unrecoverable if a spin is
allowed to develop.
The Piper PA-38 Tomahawk,
designed specifically for flight instruction, including easier demonstration
of spins, was involved in 50 stall/spin accidents from 1982 through 1990,
for a rate of 3.28 per 100 aircraft in the fleet. During the same period,
the Cessna 150/152 had 259 stall/spin accidents, for a rate of 1.31 per 100
aircraft, and the Beech 77 suffered only four such accidents, for a rate of
1.64 per 100 aircraft.
Tomahawks, therefore, were
involved in roughly double the number of stall/spin accidents per 100
aircraft as the Cessna 150/152 or the Beech 77. These are raw numbers where
the NTSB identified stall/spin as the primary causal factor.
An estimated 43 of the
Tomahawk accidents occurred at a low altitude, where recovery, regardless of
aircraft type, was unlikely. In many cases, the stall was the final event
where an accident was already all-but-certain, such as buzzing, fuel
exhaustion, or strong surface winds. In some cases, it was not clear from
the narrative how high the aircraft was when the stall or spin began. ASF
was able to identify nine PA-38 accidents in which the NTSB cited spin as a
cause or a factor. The NTSB also coded one Beech 77 and 59 Cessna 150/1 52
accidents as spin-related. The accident narrative indicated that the
aircraft was spinning. Bottom line - the Tomahawk is involved in
proportionately more stall/spin accidents than comparable aircraft.
Does that make it unsafe?
No, it only means that the PA38 must be flown precisely in accordance with
the Pilot Operating Handbook and with instructors who are proficient in
stalls and spin recovery in that aircraft ...
Regardless of aircraft type,
in many cases a stall is only incidental to the accident. Considering fleet
size and hours flown, spin performance of the Cessna 150/152 and the Piper
PA-38 are worth comparing. Manufacturers of both recommend no fewer than
3,000 to 4,000 feet agl as a minimum altitude for recovery. Spin
entry altitude recommendations range from 6,000 in the Cessnas to 6,500 to
7,000 feet in the Piper. When proper recovery techniques are used, the
one-turn spin altitude loss for both the Cessna 150 and 152 is about 1,000
feet, taking between ¼ and ½ turn. For the PA-38, recovery may require up to
1-½ turns and between 1,000 to 1,500 feet.
No matter what aircraft is
flown, pilots must respect aerodynamics and operational differences. Especially
in high-performance aircraft, techniques vary, but when flown properly, they
pose no problems.
Watch your airspeed! (Or not)
Most of today's pilots have been
taught that stalls occur when the angle of attack of the wing reaches a critical
point. In the majority of GA single-engine aircraft, that critical AOA is around
16-18 degrees above the flight path. If the flight path is 18 degrees nose down,
a steep dive, the aircraft will stall as the attitude approaches level flight.
Less well understood is the
importance of the relative wind acting on the wing. Relative wind is always
opposite the direction of travel of the aircraft, so if an aircraft is
descending in a level attitude, the AOA is greater than if the aircraft was in
The diagram illustrates the
position of the wing in various flight attitudes. Attitude is only indirectly
related to angle of attack. The wing can be stalled when it is a near level
position, above the horizon or below.
Many pilots believe that an
airplane won't stall until it reaches the stall speed (Vs) published in the POH.
Stalls and spins both result from a disruption of airflow over the wing. It is
important for all pilots to know that a stall or spin can occur at ANY airspeed
and at any attitude. If the wing reaches its critical angle of attack, it will
stall. A spin will result when one wing has a lower coefficient of lift than the
other. A full explanation of relative wind, stalls and spins was carried in the
February 1997 issue of AOPA Flight Training magazine.
One safety device long available
in airline and turbine corporate aircraft is an angle of attack indicator, which
provides a real-time readout on the relationship between the chord line of the
wing and the flight path of the aircraft. One type of an angle of attack
indicator is shown here.
Very few typical GA aircraft
have such a device, so after passing the private pilot check ride, most pilots
revert to an overly simplistic concept of stalls and spins. This view is best
summarized in the words of flight instructors the world over: "Watch your
airspeed, or you're going to stall this airplane!"
Even after a gentle
demonstration of an accelerated stall (reaching critical angle of attack in a
steep turn at a higher airspeed than during level flight), the "watch your
airspeed" myth persists.
Although the POH is the primary
reference for recovery from a spin, the following can be used as a general
- Retard the throttle to idle. In most aircraft, power hampers the recovery.
- Ailerons neutral. Many pilots will attempt to recover from the spin using the
ailerons. This may actually make the problem worse.
- Apply full opposite rudder. Apply rudder opposite the rotation of the spin. If
you have trouble determining which way the airplane is spinning, look at your
turn coordinator or turn needle. It will indicate the direction of rotation.
- Apply forward elevator. Immediately after applying opposite rudder, apply a
quick forward motion on the control yoke and hold anti-spin controls until the
aircraft starts to recover.
- Recover from the dive. Once you have completed the four previous steps, and
the rotation stops, recover from the dive. The descent rate may be over 5000
feet per minute and the airspeed will rapidly exceed redline. Remember to
neutralize the rudder after the rotation stops.
remember that since the majority of fatal stall/spin accidents occur at low
altitudes, from which recovery is unlikely, prevention essential.
practice stalls or approaches to stalls at an appropriate and safe altitude
and only when you are competent. If it's been awhile, take an experienced CFI
practice spins only with an instructor who is current and only in a properly
maintained and approved aircraft. In some cases a parachute may be
fly at a safe altitude above the ground so that you won't be surprised by
terrain, wires, or towers that would require a quick pull up and a probable
remember that turns, vertical (pull ups) or horizontal, load the wings and
will increase the stall speed, sometimes dramatically.
explore the corners of the flight envelope close to the ground.
exceed 30 degrees of bank in the traffic pattern.
follow another aircraft in the pattern too closely. If you cannot maintain a
safe airspeed (safe AOA) - go around.
buzz or otherwise show off with any aircraft. You don't need to - as a pilot
you belong to a special group - less than one third of one percent of the U.S.
adult population is certificated to fly.