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AOPA Stall/Spin Study -- Stowell's Review (8,000 words)



 
 
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Old August 31st 03, 11:38 PM
Rich Stowell
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Default AOPA Stall/Spin Study -- Stowell's Review (8,000 words)

All right! Can't a guy get away from civilization for a while, safely
out of e-mail range, without the world falling apart? Ok, ok, maybe
only that sliver of the world that cares about stalls and spins in
light airplanes. I come home after nearly three weeks traversing the
Pacific Northwest giving seminars and stalling, spinning, looping, and
rolling airplanes (what could be better than spinning an Aerobat along
side Orcas Island?) and what do I find? SPAM--lots and lots of Spam
thanks to the SoBig virus, which has wormed its way into aviation
address books. But sandwiched in between the layers of Spam,
legitimate e-mails from pilots troubled by the recent AOPA study on
stalls and spins. Naturally, I'm right in the middle of switching
ISP's too, so easy access to the Internet is cut off until the end of
the month...

Anyway, thanks to all for the heads up. I've read through the study
and have cobbled together my thoughts, opinions, and analysis. Much of
what appears below comes from various parts of the stall/spin book
I've been working on. I must also preface my remarks thusly:

1. I've been a member of AOPA since 1984.
2. I've supported AOPA on a number of issues over the years.
3. I believe AOPA provides a lot of useful information for pilots
through the Air Safety Foundation, its various publications, and
innovative programs such as Seminars-in-a-Box.
4. AOPA's Pilot and Flight Training magazines have been supportive of
my work over the years, for which I remain forever appreciative.
5. As in any long-term relationship, AOPA and I have respectfully
disagreed on a few subjects.
6. My opinions on the two central questions in the stall/spin debate:
Is spin training beneficial -- YES; Is it feasible to re-institute a
national spin training requirement for private pilot applicants -- NO.
Though beneficial, the infrastructure does not exist for spin training
to be conducted safely on a national scale.

It is with all due respect to AOPA as an organization that I offer the
following critique of the newly released stall/spin study. The intent
is to reinforce the valid points, clarify the ambiguous ones, debunk
the persistent stall/spin myths, and in the end, help to expand our
understanding of the stall/spin accident picture so that pilots can
take logical, informed steps to improve their stall/spin awareness.


------START------

REVIEW of NEW AOPA STALL/SPIN STUDY
Prepared by Rich Stowell
August 30, 2003


For the text of the AOPA study, see http://www.aopa.org/asf/ntsb/


Although AOPA's recently published study, "Stall/spin: Entry point for
crash and burn?" (hereafter referred to as "the AOPA study") provides
some useful information, it certainly does not explode any stall/spin
myths. In fact, the study's opening salvo, "Pilots who believe that
aerobatic training will enable a recovery from an inadvertent spin in
the traffic pattern are fooling themselves" is a myth I believe has
been fabricated solely for the purpose of the study. Surely pilots who
believe this--if any exist--must be part of a small minority indeed.

In the fifteen years that I've been involved in teaching pilots about
stalls and spins, including giving over 170 safety seminars across the
U.S., performing 24,000 spins, interacting with scores of other
professional spin and aerobatic instructors, and reading everything I
can get my hands on in this regard, I have yet to come across this
so-called myth. I have yet to come across any pilot whose motivation
to learn more about stall/spins was rooted in a belief that it would
enable him/her to recover from a spin in the traffic pattern. I have
yet to meet rational proponents of spin training who claim spin
training would allow a pilot to recover from a spin encountered in the
traffic pattern. Pilots certainly are smart enough to realize that if
a stall is allowed to progress into a spin at traffic pattern
altitudes, the probability of survival is slim regardless of prior
training. The primary reason proponents advocate, and pilots seek out,
additional stall and spin training is--surprise!--spin prevention. The
advertised objective of spin training is to expand a pilot's
knowledge, experience, and skill set to prevent an inadvertent spin
departure in the first place.

Another myth cited in the AOPA study is "watch your airspeed, or
you're going to stall this airplane!" The study claims that this myth
is largely propagated by flight instructors, yet it does not address
the reason why this might be so. This airspeed myth is deeply rooted
in general aviation. It has been propagated not only by generations of
under-trained and/or uninformed flight instructors, but also by
aviation textbooks and aviation publications. Case in point: A popular
and highly respected pilot/writer for a major aviation magazine (not
AOPA Pilot) wrote, "Just don't let airspeed get below a safe value and
stalls are not a problem." This nonsensical recommendation appeared in
print in the year 2002. As a point of clarification, I doubt you will
find this myth advanced by those who specialize in spin and aerobatic
training.

AOPA has been known to disseminate stall/spin mythology as well. Most
recently for example, page 56 in the August 2003 issue of Pilot
contains the following: "The FAA dropped the requirement to
demonstrate spins for the private pilot certificate in 1949.... It
seems many more pilots were killed in training than in nontraining
(real) emergencies..."

The notion that mandatory spin training was rescinded in 1949 because
"we were killing more pilots during spin training than the training
was saving" is a myth. In the many research papers I've read on the
subject from every decade of powered flight, I have yet to come across
evidence substantiating this claim. The reasons why mandatory spin
training for private pilots was deleted from the regulations in 1949
were spelled out in CAR Amendment 20-3, specifically:

"This amendment eliminates spins from the pilot certification
requirement and, in lieu thereof, provides for dual flight instruction
in the prevention of and recovery from power-on and power-off stalls
entered from all normally anticipated flight attitudes. It is believed
that the deletion of the spin requirement and the placing of greater
emphasis upon the prevention of and recovery from stalls will result
in greater air safety in two ways: (a) it will emphasize recognition
of and recovery from stalls which, on the basis of available accident
statistics, has proved to be the most dangerous maneuver to pilots;
and (b) elimination of the required spin maneuver will act as an
incentive for manufacturers to build, and operators of schools to use,
spin-resistant or spin-proof aircraft."

Neither of the two ways cited in CAR 20-3 for improving air safety
mentions spin accidents during instructional spin training flights. In
fact, cited reason (a) unequivocally states that the stall was the
most dangerous maneuver for pilots--not intentional spins performed as
part of required spin training. I believe it is reason (b), however,
that gets to the true motivation behind the deletion of mandatory spin
training--the FAA and airplane manufacturers (and no doubt those whose
primary allegiance was to the manufacturers) struck a deal: In
exchange for relaxing spin training and aircraft spin certification
requirements, manufacturers were to develop more spin resistant
designs. Manufacturers have largely failed to live up to their end of
the bargain.

Perpetuating the more-pilots-die-in-spin-training myth in this day and
age completely, if not intentionally, ignores the facts about those
schools and instructors dedicated to the professional conduct of
broad-based stall/spin awareness education. Once again I cite the
results of a survey taken of well-known aerobatic schools in 1997
("well-known" subjectively meant those schools repeatedly listed in
the International Aerobatic Club Directory of Aerobatic Schools, those
frequently advertising in Sport Aerobatics magazine and other
publications, those with printed course outlines and good
word-of-mouth reputations, etc.). Twenty responses out of twenty-four
surveys mailed were returned completed, representing the following
cumulative experience:

1. The range of years engaged in formalized spin/aerobatic training: 5
to 29 years.
2. The estimated total number of hours of spin and aerobatic
instruction given: over 135,000 hours.
3. The estimated number of dual instructional spins entered: over
250,000 spins. This figure represents nearly 12,000 vertical miles
travelled while spinning with students.

All this exposure to stalls and spins while in a dual training
environment, and yet the sum total of stall/spin accidents involving
these schools during any phase of any instructional flight whose
primary purpose was spin or aerobatic training was ZERO. Six years and
no doubt many thousands of additional stall/spins since the survey,
this record still stands.

It seems the well-established schools specializing in comprehensive
stall/spin awareness training have a good handle on how to conduct
such training safely. These schools and their instructors have been
providing a relatively safe, useful service to the aviation community
for a long time, but readers wouldn't know it when the myth continues
to be spread by aviation organizations.

Perhaps I missed something in my research, but since the latest
example of this myth appeared in Pilot, I hereby challenge AOPA to
provide credible and properly cited references (or better yet, copies
of the text) dated circa 1949 supporting the claim that mandatory spin
training for private pilot applicants was deleted largely because of
the spin accident rate associated with the spin training required
prior to 1949.


PILOT GROUPS

The AOPA study also breaks down fatal stall/spin accidents by pilot
certificate level. Student pilots as a group have the lowest
stall/spin fatality rate with (4) percent, followed by the corps of
ATP's with about (10) percent. Of interest is AOPA's conclusion that
"it appears that ATP's are generally the most experienced and
knowledgeable pilots, while students are under very close supervision
to ensure their safety."

First, another look at the ATP group: An interesting study looked at
13,680 general aviation accidents for the period 1973-83. The
accidents had the following in common: they involved general aviation,
fixed-wing, single-engine airplanes flown for personal reasons only,
limited to either 1 or 2 people on board. The accident mix included
461 ATP's, all with professional flying jobs. ATP's made up 7.5
percent of the total pilot population, yet they were involved in only
3.5 percent of all fatal and less than 3 percent of all non-fatal
general aviation accidents. For the ATP, general aviation pleasure
flying posed no greater risk of death than flying professionally for
air carriers.

The ATP accidents typically did not involve alcohol, drug, or
medication abuse. ATP accidents less often involved a lack of skill
compared to private pilot accidents. However, overconfidence played a
role in nearly 60 percent of the pilot-induced, ATP accidents
(compared to 30 percent of pilot-induced, private pilot accidents).
ATP's were also over-represented in pilot-induced accidents involving
aerobatics: in all aerobatic accidents, 13.7 percent for ATP's versus
6.5 percent for private pilots; in fatal aerobatic accidents, 50
percent for ATP's versus around 20 percent for private pilots. And
compared to private pilots, ATP's were more likely to engage in
accident-causing aerobatics at an unsafe altitude.

The fatal stall/spin accident component for ATP's was equally
revealing. During non-aerobatic phases of flight, stall/spins were
responsible for 13 percent of the fatalities involving ATP's. During
the aerobatic phase, though, an alarming 38 percent of fatal
stall/spin accidents involved ATP's. Compared to the stall/spin
fatality rate for general aviation as a whole, ATP's appear to be
above average at avoiding fatal stall/spins when in the normal flight
environment. However, ATP's were below average when in the aerobatic
environment. The following considerations are likely driving this
discrepancy: overconfidence leading to unnecessary risk taking,
inadequate aerobatic training, and/or lack of experience in-type.

Again, keep in mind that ATP's have trained to the highest skill level
formally recognized by the FAA. Yet ATP's are still prone to the same
human failings as other pilots. And in the aerobatic regime,
deficiencies in judgment and stall/spin awareness skills are magnified
regardless of the level of certification attained. Moreover, the fact
that the best our group of "most experienced and knowledgeable pilots"
can do is a 10 percent stall/spin fatality rate--two and a half times
that of Student pilots--speaks volumes by itself.


STUDENT PILOTS & THEIR INSTRUCTORS

On now to Student pilots and the instructors who teach them: If the
reason Student pilots have a 4 percent stall/spin fatality rate is due
to "very close supervision to ensure their safety" as concluded in the
AOPA study, then wouldn't it follow that flight instructors would also
have a comparably low stall/spin fatality rate? Well, the AOPA study
notes that a "shocking" 91 percent of the fatal stall/spin accidents
they analyzed occurred during dual instructional flights. According to
another study, close to 20 percent of stall/spin accidents transpired
during instructional phases of flight. And in 60 percent of those
stall/spins, an FAA-certificated flight instructor was on board.
Student pilots actually have a better stall/spin record when they are
solo than when an instructor is with them. So what's up with the
instructors?

In 1993, the Transportation Research Record published a study
conducted by Dr. Patrick Veillette entitled, "Re-Examination of
Stall/Spin Prevention Training." This flight-line study assessed,
among other things, the stall/spin knowledge of general aviation
flight instructors. Questionnaires were distributed to CFI's at 43
flight schools in Tennessee, Mississippi, California, and Utah.
Questionnaires were also handed out to instructors in attendance at
seven FAA safety seminars and three Flight Instructor Refresher
Clinics (FIRC's). Five hundred thirteen civilian flight instructors
and 28 designated flight examiners participated. Five aviation
professionals--all flight instructors with college education in
aerodynamics--processed the surveys. NASA research, journal
literature, and the textbook, Aerodynamics for Naval Aviators were
used as references.

This study at long last quantified the shortage of stall/spin
expertise in our corps of FAA-certified flight instructors:
Ninety-four percent of the instructors relied primarily on popular
literature (i.e.: aviation magazines) for their stall/spin
information; ninety-six percent also relied heavily on their own
instructors. Unfortunately, ninety-five percent of the instructors
failed ever to receive training in either spin dynamics or the likely
conditions preceding an inadvertent spin. Ninety-four percent of the
instructors understood neither aircraft spin certification
requirements, nor the operating limitations imposed as a result.

The most foreboding aspect of the Veillette study, however, involved
the hands-on spin experience of flight instructors. Ninety-eight
percent noted that their formal spin training consisted of no ground
instruction and a mere two spins--one in each direction. Nonetheless,
these instructors readily received logbook endorsements certifying
that they were competent to teach spins. We'd surely consider it
absurd, for example, if all it took to qualify to be an instrument
instructor (CFII) was a logbook entry showing that the applicant had
performed a grand total of two instrument approaches. On the contrary,
instrument training has evolved into a rigorous process involving
specially equipped airplanes and specially certified instructors. Just
as the instrument flight environment places unique demands on its
pilots and airplanes, so too does the spin environment place unique
demands--aerodynamically, physiologically, psychologically--on those
who enter its realm. It is equally unforgiving of incompetence as
well. Yet too many pilots remain nonchalant in their attitudes toward
spinning.

The changes made to FAR Part 61 in 1991 attempted to shore up our
sub-standard stall/spin awareness across all levels of flight
training, especially at the Flight Instructor Applicant level. But
just how successful has this program been? More than a year after
implementation of the enhanced stall/spin requirements, 97 percent of
the CFI's surveyed were still unaware of the regulatory changes. In
fact, 35 of the 513 instructors surveyed had been certified after the
changes went into effect, yet not a single one of them was aware of
the changes. Most instructors knew nothing about the FAA's
well-written Advisory Circular AC 61-67B, Stall and Spin Awareness
Training, issued on May 17, 1991 either.

The top-down effect of this continued ignorance was demonstrated
during an informal survey of pilots attending stall/spin safety
seminars in Minnesota, Florida, New Jersey, and California in 1998. On
the order of 300 pilots attended these seminars, of which
approximately 100 had earned Private, Commercial, or Flight Instructor
certificates after April 1991. An abysmal 10 percent of these pilots
had received a copy of AC 61-67B from their instructors as part of
their stall/spin awareness training, even though applicable
information in this circular superceded that of the FAA's old Flight
Training Handbook (AC 61-21A).

The Veillette Study further identified a generally marginal
understanding by CFI's of the following subjects: stall aerodynamics,
the effects of control deflection on the stall, airfoil stall
development, planform effects on stall behavior, spanwise flow
effects, stall warning signs, the secondary effects of flight
controls, and roll control at high angles of attack. Overall,
respondents demonstrated an unsatisfactory understanding of these
critical items: pro- and anti-spin forces, autorotation, the effects
of numerous variables on spinning, spin phases and spin modes, the
effects of the controls on spin motion and recovery, and common
student recovery errors and the effects on aircraft motion.

Although instructors and examiners rated their understanding of
stall/spin dynamics as "excellent," survey results clearly indicate
that those charged with the task of teaching and testing new pilots
possess a marginal understanding of stall/spin phenomena themselves.
As mentioned earlier, nearly 20 percent of stall/spin accidents
transpired during instructional phases of flight. On the order of 60
percent of these stall/spins occurred with FAA-certificated flight
instructors on board.

Student pilots should be forewarned that, compared to their solo
training sorties, they are nearly twice as likely to have a stall/spin
accident with the instructor in the airplane.

The relative stall/spin unawareness of flight instructors in general
is clear and disturbing. Evidence of how deeply rooted this
unawareness really is can be found in stall/spin accidents associated
with aerobatics. The aerobatic environment, after all, demands the
utmost in stall/spin awareness; deficiencies in a pilot's stall/spin
skills are magnified here. For example, NTSB analyzed 105
aerobatics-related accidents during the period 1972-1974. Stalls and
spins were cited as primary accident types in 49 of the cases--a 47
percent stall/spin accident rate. NTSB also noted that most of the
stall/spins were unintentional and were related to the performance of
other aerobatic maneuvers initiated at unsafe altitudes. But a number
of the stall/spins were intentional. And they were started at
altitudes from which recovery should have been possible. Following are
NTSB's observations about the accidents stemming from the intentional
stall/spins at altitude:

"persons involved in these types of accidents had some previous spin
instruction, but their overall knowledge and proficiency in spins is
believed to have been minimal.... they probably were not fully aware
of all of the adverse spin characteristics that could be induced
through improper use of the flight or power controls, or both, or of
the essential need to use a precise technique...in order to optimize
the recovery."

How did flight instructors fare within this accident population?
Twenty-four out of the 105 aerobatic accidents involved commercial
pilots with flight instructor certificates. The age ranges broke down
thus: 11 instructors were under 30 years old; 10 of them were between
30 and 50 years old; 3 were over 50 years old. Eight of the
instructors had logged over 3,000 hours total time; only 2 had logged
fewer than 600 hours total time. As for time in type, 14 instructors
had fewer than 300 hours in type, and 6 of those had fewer than 100
hours in type. Instructors made up 23 percent of the accident
population, but they were involved in 39 percent of the spin
accidents. And fifty-eight percent of the instructors who crashed
during aerobatic flight did so in a spin.

Based on all of the above, it is highly unlikely that Students pilots
have achieved their 4 percent stall/spin fatality rate because of
"close supervision." So what, then, could possibly explain the low
stall/spin fatality rate of Students? What is it about being a Student
pilot that the rest of us aviators, regardless of our certificate
level, need to know? I don't know the answer for sure, but I do have a
hypothesis:

According to the FAA, pilots as a whole spend a mere six percent of
their flight time in the critical phases associated with the traffic
pattern: takeoff, initial climb, approach, and landing. These phases,
however, account for a disproportionate fifty-seven percent of
aviation accidents. But the traffic pattern happens also to be the
domain of Student pilots--round and round they go, flight after
flight, up and down, full stops, touch and go's, go-arounds, flaps, no
flaps, turning, gliding, etc. Looking back in my own logbook, I
averaged more than 4.1 landings per hour all the way through to my
Private Pilot check ride.

Even though the stall/spin knowledge passed down from instructors to
students is largely inadequate, Student pilots nonetheless spend a lot
more of their flight time in and around the pattern than other pilots.
Through sheer repetition, Students eventually get good, real good, at
flying in the pattern. Perhaps it is the intimate familiarity Students
develop with traffic pattern operations (read that: slow flight) that
compensates for deficiencies in stall/spin and other flight
experience.

The ratio of landings-per-hour for the non-Student pilot groups
(Private through ATP) is probably far lower compared to the Student
group. Upon earning the Private certificate, cross-country flying
tends to become the new norm. Landings per hour--and along with it,
slow flight proficiency--might drop to as little as 1 per hour, even
less. In my case, over the 6,300 hours logged since being a Student
pilot, my average has dropped to 2.3 landings per hour. Perhaps a
better indicator of experience vis--vis stall/spin accidents might be
the landings-per-hour ratio (maybe a study could be commissioned to
investigate a possible link between traffic pattern stall/spin
accident frequency and landings per hour or a similar parameter). If
so, then Students undoubtedly would be the most experienced pilots in
the environment where the majority of stall/spin accidents occur.

The fatal stall/spin accident rate of the Student pilot group is also
interesting from an industrial accident prevention standpoint.
Industrial accident prevention postulates that the "absolute zero"
accident rate achievable is around 2 percent. In other words, 98
percent of all accidents are in some way preventable; only 2 percent
of accidents absolutely cannot be prevented. The Student pilot group
apparently has come very close to the theoretical minimum fatal
stall/spin accident rate--way to go Students! Maybe the rest of us
should strive to get ever closer to this ideal as well. Even ATP's are
two and a half times worse than Students in this regard, and a factor
of five greater than the theoretical minimum.


OTHER STALL/SPIN MYTHS

Phrases in the AOPA study such as, "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" and "since
elimination of the spin requirement for private pilots, the incidence
of stall/spin accidents has actually decreased substantially"
promulgate another persistent stall/spin myth. This myth attempts to
create a non-existent cause-and-effect relationship. First of all, we
cannot compare stall/spin accident rates from the period before 1949
directly with current stall/spin data without first normalizing the
numbers to the same standards. The art of accident investigation, and
the accuracy with which accidents are assigned into various
categories, is much better now than it was prior to 1949. Even the
level of damage required for an event to be classified as an accident
has been revised over the years. Depending on the era and the context,
so-called stall/spin accident statistics could represent one of
several groupings: stall, spin, spiral, and mush accidents lumped
together, stalls only, spins only, or only stalls and spins added
together. Hence a face-value comparison of these stats does not yield
any conclusive information.

Moreover, many variables have interacted to shape the general aviation
landscape since 1949--improved airplane designs, changes in training
and testing standards, improved training methodologies, etc. Any one
of which, or combination of which, could have influenced stall/spin
accident numbers for the better. Studies have been published
addressing the cumulative effect of these and other variables on the
stall/spin accident rate. The Society of Automotive Engineers (SAE)
published the most notable of these studies in 1976, entitled,
Statistical Analysis of General Aviation Stall Spin Accidents. Among
other things, researcher Brent W. Silver looked at the stall/spin
accident rate (meaning stalls plus spins and nothing else) for the
period 1965-1973. Within the database analyzed were 13 airplane
designs with type certificates issued prior to 1950. In addition,
these 13 designs had at least 500 registered aircraft during the
period covered by the study.

The fatal stalls-plus-spins accident rate for this subset of airplanes
was 42 percent. Twenty-odd years following the deletion of mandatory
spin training, the very same airplane designs that contributed to the
purported 48 percent stall/spin accident rate between 1945 and 1948
had a comparably high stall/spin accident rate. And remember: the 48
percent rate recorded prior to 1949 probably included more than just
the stall and spin accidents considered in the SAE study.

A look at kit plane accident statistics is equally revealing. One
researcher examined NTSB records available on the Internet for fatal
accidents involving experimental, amateur-built airplanes between 1983
and 1997 (excluding commercial aircraft, ultralights, and rotorcraft).
A total of 701 fatal accidents occurred during this period. Based on
available textual descriptions and probable causes, the researcher
concluded that an unintentional stall or spin preceded ground impact
in 45 percent of the fatal accident cases.

It can reasonably be concluded, therefore, that the deletion of spin
training in 1949 had little if any discernible effect on the
stall/spin accident rate. The most significant change in the
stall/spin accident rate came about as a result of the influx of newer
certificated designs introduced in the latter 1950's, throughout the
1960's, and into the 1970's. Another way to look at it is this: "spin
training" as it was conducted prior to 1949 was no better or no worse
a training strategy than the "stall avoidance" strategy that replaced
it. Once flight lines became populated with the newer designs, the
stall/spin accident rate declined. But just as flight lines today
retain essentially the same look and feel as in the 1970's, so too has
the stall/spin accident rate leveled off. The stall/spin accident rate
has stagnated along with the make up of our flight lines. Yet the myth
that attempts to link the deletion of private pilot spin training to
an improved stall/spin accident rate persists.


STALLS & SPINS, APPLES & ORANGES

The discussion of altitude losses during stalls and spins referenced
in the AOPA study lacks context; the information as provided,
therefore, is misleading. Simply reporting that POH's list average
altitude losses during stalls as between 100 and 350 feet, for
example, is meaningless without stating the relevant caveats.
Manufacturer-supplied altitude losses during stalls are based on the
following:

1. Intentional stall tests;
2. Performed at altitude;
3. Conducted under ideal conditions;
4. Using airplanes finely tuned to exact factory specifications;
5. With FAA-DER Test Pilots at the controls;
6. Without emotional duress.

These conditions are nothing like the real-life conditions under which
pilots are typically encountering inadvertent stalls. Even during
intentional stall practice at altitude, I routinely witness
certificated pilots who are not proficient in stalls losing as much as
twice the manufacturer-listed numbers. Now imagine those same
certificated pilots in a traffic pattern, under duress, accidentally
stalling while banked in a turn. The altitude actually required for
recovery under these realistic conditions is not "minimal" compared to
the limited altitude available.

The study's reporting of altitude losses during a spin is equally
misleading. It fails to provide the following context for those
numbers:

1. The spins were intentional;
2. Conducted at altitude;
3. Entered from a wings-level attitude;
4. Performed by experienced Test Pilots;
5. With pro-spin control inputs applied and held for one full turn
prior to applying spin recovery actions.

No doubt pilots who are not proficient in spins, but who attempt to
duplicate a one-turn spin under the above conditions (in
spins-approved airplanes) will typically lose more altitude than test
pilots. But the study's implication is that any stall can be recovered
in less altitude than any spin. This simply isn't true. All other
things being equal, of course the pilot who reacts instantly and
correctly to the onset of a stall will recover with more altitude to
spare than the pilot who enters a spin, holds pro-spin controls for
precisely one full rotation, and then initiates recovery actions.
Conversely, the pilot who freezes on the controls for several seconds
at the onset of a stall will lose more altitude than the pilot who
initiates correct recovery actions instantly upon spin departure.
Again, for a meaningful comparison, the conditions and assumptions
must be stated clearly.

Although the intentional, one-turn spin might be included as part of a
broader spin training program, it is merely one exercise used to
develop a specific skill set, just as performing holding patterns, or
S-turns across a road, or any other practice maneuver. Readers of the
AOPA study, though, are left with the impression that pilots who learn
how to perform a one-turn spin will apply what they've learned in an
emergency as follows: "I'm spinning in the pattern...ok, wait for one
full turn...start recovery now..." Does anyone really believe this to
be the desired response fostered during spin training?

(As an interesting side bar, every time we watch Sean D. Tucker and
Patty Wagstaff perform snap rolls, lomcevaks, and other tumbling
maneuvers during their airshow routines, we are witnessing experienced
pilots skillfully using their quick reflexes to enter and recover from
accelerated stall/spins at traffic pattern altitudes. Pilots have
recovered from accidental spins in the pattern as well. Perhaps the
most famous pilot to do this is former X-15 test pilot Scott
Crossfield, who as an instructor, recovered from a student-induced
spin departure in the pattern. These certainly are the rare
exceptions, and no one should be lulled into a false sense of security
about the prospect of recovering from a spin at pattern altitude.
Again, the point of spin training is to give pilots the depth of
experience to avoid an inadvertent spin in the first place.)


THE TOMAHAWK REFERENCE

The AOPA Study brings the controversial Piper Tomahawk into the mix to
illustrate how airplanes can vary in their stall/spin behavior.
Tabling the ongoing debate about this particular airplane for now, the
AOPA study concludes that "the Tomahawk is involved in proportionately
more stall/spin accidents than comparable aircraft.... 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..."

AOPA's own Safety Review: Piper Tomahawk PA-38-112 published in 1996
discusses this airplane in detail. The Safety Review also provides a
suggested Training Course Outline (TCO) for pilots and instructors who
might transition into a Tomahawk. The TCO includes four training
blocks totaling at least four hours of ground instruction and 4.5
hours of flight instruction. Given the stall/spin focus of the current
AOPA study and the admitted propensity for stall/spin accidents in the
Tomahawk compared to other trainers, the recommended TCO dedicates
surprisingly little flight time to stall practice. The TCO devotes
absolutely no flight time to the practice of spins, even though the
airplane is approved for intentional spins.

Here, too, the AOPA study misleads readers regarding so-called
significant differences between Tomahawk and Cessna 150/152 spin
behavior. Representative POH's for both airplanes state:

Tomahawk: "The ailerons must remain neutral throughout the spin and
recovery because aileron application may alter spin
characteristics..."
Cessna 152: "Careful attention should be taken to assure that the
aileron control is neutral during all phases of the spin because any
aileron deflection in the direction of the spin may alter the spin
characteristics..."

Tomahawk: "Apply and maintain full rudder opposite the direction of
rotation."
Cessna 152: "Apply and hold full rudder opposite to the direction of
rotation."

Tomahawk: "As the rudder hits the stop, rapidly move the control wheel
full forward and be ready to relax the forward pressure as the stall
is broken.... In all spin recoveries, the control column should be
moved forward briskly, continuing to the forward stop if necessary....
in most cases, spin recovery will occur before the control wheel
reaches the fully forward position."
Cessna 152: "Just after the rudder reaches the stop, move the control
wheel briskly forward far enough to break the stall. Full down
elevator may be required..."

Tomahawk: "Normal recoveries may take up to 1-1/2 turns when proper
technique is used...."
Cessna 152: "Up to 2 turns [in a spin].... Application of recovery
controls will produce prompt recoveries of from 1/4 to 1/2 of a turn.
If the spin is continued beyond the 2- to 3-turn range....
[recoveries] may take up to a full turn or more."

Pilots reading the manufacturer-supplied information for these two
designs clearly see that both the Tomahawk and the 152 should behave
quite similarly within their approved spin envelopes. Why the Tomahawk
may not behave as advertised, certified, and expected is an issue for
another time.


RECOMMENDED DO's & DON'Ts

I agree with and endorse most of the Do's and Don'ts suggested in the
AOPA study, with the following exceptions:

1. A glaring omission on the DO list should be the recommendation to
procure a copy of FAA AC 61-67C, Stall and Spin Awareness Training
coupled with the insistence that the appropriate training elements
described in that AC must be covered thoroughly by your flight
instructor as part of your training. Consider insisting on a review of
these stall/spin awareness elements during every flight review as
well.

The least we should do is demand--and strongly--that pilots receive
the minimum stall/spin awareness training mandated since 1991. We
should also demand of our Flight Instructor Applicants far more
practical spin experience than the usual two intentional spin entries
before being signed off as competent to teach stall/spin awareness to
others. And we should encourage pilots to consider enrolling in a
stall/spin program that includes hands-on experience with spins in a
controlled, dual environment, with qualified spin instructors.

2. AOPA's suggestion, "DON'T exceed 30 degrees of bank in the traffic
pattern" has been repeated often enough that it might as well be
considered an aviation myth. The logical question is, "How come?
What's different about a 30 degree bank at 300 feet AGL versus the
same bank angle at 3,000 feet AGL?" The answer: nothing whatsoever,
aerodynamically-speaking.

I believe arbitrarily restricting pilots to a specific maximum bank
angle in the pattern without citing the underlying reasons might
actually cause more pilots to skid their turns than the suggestion is
supposed to prevent. Consider that pilots have an instinctive aversion
to banking an airplane when close to the ground. Furthermore, they are
admonished, "don't ever exceed 30 degrees of bank in the pattern." So
what's the pilot who has overshot the turn from base to final to do?

The safest response to an overshoot is usually to level the wings and
execute a go-around. But the all-to-common reaction is this: "I've
overshot...I need to get back to the centerline...I can't exceed 30
degrees of bank, so I'll cheat the turn by applying some more
rudder..."

Pilots would be better served by giving them legitimate options rather
than unqualified limitations. If you've overshot the turn from base to
final, for example, here are a few options:

1. Level the wings and execute a go-around, then use better judgment
and planning on the next approach; or,

2. Simply continue the turn as is, describing a teardrop back to the
extended centerline. Maintain a constant bank angle and airspeed
throughout. And use power as required to control your altitude during
the turn; or,

3. Increase the bank angle to tighten the turn using a coordinated
application of aileron to bank the airplane and sufficient rudder to
cancel adverse yaw. Release rudder pressure once the new bank has been
estabilished. Be aware that if you elect to increase the bank angle,
the stall speed will also increase; therefore, you may need to lower
the nose simultaneously to stay comfortably ahead of the increasing
stall speed. You have to be willing to lower the nose even though you
are close to the ground. Use power as required to control your
altitude profile (i.e.: rate of descent) throughout. If you are at all
uncomfortable with increasing the bank angle AND lowering the nose to
make this happen, DO NOT ATTEMPT TO TIGHTEN THE TURN. Choose options 1
or 2 instead.

DO NOT attempt to tighten a turn by applying additional rudder either,
for the following reasons: The misapplied rudder input will cause the
nose of the airplane to slice downward through the horizon in yaw.
Close to the ground, the instinctive reaction to this movement will
invariably be to pull the elevator control farther aft. This input
will not correct the skid, but will cause airspeed to decay and angle
of attack to increase. If you pull enough to induce a stall with
excessive rudder applied, the airplane will have no choice but to
depart into a spin with insufficient altitude for recovery.


WHAT PILOTS WANT & NEED

The tone set by the AOPA study seems to be out of synch with the real
fears, needs, and desires of general aviation pilots. I also suspect
that AOPA harbors an antiquated view of "spin training." Although many
may still believe that pilots who have performed one or two
intentional spins are "spin trained," nothing could be farther from
the truth. Just as it would be illogical to consider a pilot who has
done a holding pattern or two to be "instrument trained," it is
equally illogical to consider a pilot who has done an intentional spin
or two "spin trained."

Modern-day "spin training"--training provided by professionals well
versed in the theory and practice of high angle of attack flight--is
part of a continuum more accurately described now by the FAA as
"stall/spin awareness training." Unfortunately, the research conducted
by Dr. Patrick Veillette revealed that pilots and instructors alike
have not been receiving the minimum stall/spin awareness training
mandated since 1991 and spelled out in Advisory Circulars 61-67B and
61-67C. Using the Advisory Circular as a guide, the stall/spin
awareness continuum progresses as follows:

Stall/spin effects and definitions; weight & balance considerations;
airworthiness and certification standards; wing contamination effects;
distractions, human factors, and vestibulo-ocular illusions; typical
stall/spin accident scenarios and warning signs; stall recognition;
types of stalls; stall recovery; secondary stalls; spins; primary
causes; types of spins; spin recovery; typical recovery errors; spiral
recovery.

The stall training branch includes stall avoidance practice at slow
airspeeds; power-on stalls; engine failure while in a climb followed
by a gliding turn; cross controlled stalls in gliding turns; power-off
stalls; stalls during go-arounds; elevator trim stalls.

The spin training branch includes power-on and power-off stalls,
turning stalls, spin avoidance training using realistic distractions;
intentional incipient spins; spin entry, spin, and spin recovery;
spin-to-spiral transitions; aggravated spins; inadvertent stall and
spin departures from unusual attitudes.

The majority of pilots and instructors alike desire more and better
information regarding stalls and spins. As the following surveys show,
general aviation pilots historically have not been opposed to the idea
of hands-on spin training--not to be able to recover from a spin in
the traffic pattern, but rather to expand their comfort levels as well
as to develop additional awareness to prevent a stall/spin departure
close to the ground:

I. General Aviation Pilot Stall Awareness Training Study, Report No.
FAA-RD-77-26, September 1976, from an informal sampling of
approximately (75) instructors attending a flight instructor refresher
clinic:

Percentage believing spins should be required -- 65%

II. A Study to Determine Basic Aerobatics as a Requirement for the
Commercial Pilot Certificate, Graduate Research Project by David Lee
Bagby, Embry-Riddle Aeronautical University Extended Campus, Sky
Harbor Resident Center, August 1997, from a survey of (49) instructors
employed by ERAU:

"Spin awareness training is more effective than spin flight training"
-- 82% either disagreed or strongly disagreed with this statement.

"I consider aerobatic training [including spins] safe" -- 86% either
agreed or strongly agreed with this statement.

"Aerobatic training [including spins] would benefit my flying skills"
-- 98% either agreed or strongly agreed with this statement.

"Aerobatic training [including spins] would increase confidence in my
flying ability" -- 98% either agreed or strongly agreed with this
statement.

"Aerobatic training [including spins] would improve safety" -- 96%
either agreed or strongly agreed with this statement.

"Basic aerobatic training [including spins] should be mandated into
commercial pilot training" -- 82% either agreed or strongly agreed
with this statement.

III. AVweb's Question of the Week: Spin Training. [Online] Available
http://www.avweb.com, downloaded January 25, 2001:

"What, if any, benefits did you get if you received spin training?" --
956 responses
a. Increased knowledge of what an airplane can and cannot do. (6%)
b. Increased confidence in my skills. (5%)
c. Increased awareness of the need for precision during critical
phases of flight. (5%)
d. All of the above. (82%)
e. Other (3%)

"Do you feel spin training should be required to become a certificated
pilot?" -- 1181 responses
a. Yes. (57%)
b. No. (7%)
c. Encouraged, but not required. (36%)

Anecdotally, I've traversed the U.S. from Alaska to Florida,
California to Massachusetts, averaging nearly a seminar a month every
year for the last fifteen years. The majority of seminars have dealt
with stalls and spins. The subject matter remains as popular among
pilots today as it did fifteen years ago. My sense is that stall/spin
articles appearing in aviation magazines continue to be well received
by readers, too. And the demand for stall/spin training at established
aerobatic schools is as strong as ever. The facts remain:

One-third of stall/spin accidents in an NTSB study involved pilots
with more than 1,000 hours of flight time. The median pilot experience
of those involved in stall/spins was 400 hours (just as many
stall/spin victims had more than 400 hours as had less than 400
hours). We can profile who is most at risk of an accidental stall/spin
as follows: it's the pilot who has logged fewer than 1,000 hours; who
is on a daytime pleasure flight in good weather; who is in the traffic
pattern; and who is either turning or climbing. Leading up to the
inadvertent stall/spin, the pilot will be distracted into making a
critical error in judgment. Fixation on the unfolding accident will
effectively render (1) in (3) pilots deaf to a blaring stall warning
horn. And pilots with fewer than either 500 hours total time, or 100
hours in type, are more likely to encounter an inadvertent stall/spin
than to have a genuine engine failure (i.e.: a random-event engine
failure, not one attributed to such pilot errors as fuel
mismanagement).

And how does this compare, for instance, to the mid-air collision
potential? Let's put the comparative threats into perspective: During
the period 1977-1986, the number of mid-air collisions involving
general aviation aircraft averaged 27 per year. Forty percent of these
ended without injury. And those involved in mid-air accidents were
typically high-time pilots, averaging slightly more than 3,000 hours.

Consider the following 1987 statistics as well: the U.S. boasted
699,653 active pilots who collectively logged an estimated 47.9
million flight hours. Amortized, U.S. pilots averaged 68 hours each
that year (unfortunately, this average decreased to less than 50 hours
per pilot per year during the 1990's). Consider, too, that the average
active flying career of a general aviation pilot is estimated to be 17
years. Hence, the typical light airplane pilot will accumulate close
to 1,200 hours total time. Pilots with 3,000 hours--those usually
involved in mid-airs--are undoubtedly high time pilots by comparison.
Once again we find that it is the majority of pilots--students,
private pilots, CFI's--who remain squarely in the bull's-eye of the
stall/spin accident zone throughout their aviation careers. Though
important, mid-airs are statistically a lesser concern compared to the
inadvertent stall/spin.

The stall/spin problem is neither insignificant nor indiscriminant. No
segment of the pilot population is immune to it. Not CFI's, not even
ATP's. Typical pilots on typical flights fit the typical stall/spin
profile. Once encountered, the prospect for survival is bleak: one out
of four fatalities tied to stall/spins, an 80 percent chance of
serious or fatal injury, a greater than 90 percent chance that
insufficient altitude exists in which to recover. Add to this the
realization that 19 percent of stall/spin accidents are associated
with the flight training process. And a CFI is present in 11 percent
of the cases.

Those pushing the anti spin training agenda always attempt to measure
the benefits of spin training against an unreasonable hypothesis,
namely: "Even a spin trained pilot cannot recover a spin entered while
in the pattern." To prove their case, opponents of spin training ask
us to imagine an airplane in a spin a couple hundred feet above the
ground. Next, a so-called spin trained pilot is miraculously
transported into the cockpit to see if he/she can recover in time.
This litmus test is disingenuous at best. Pilots don't suddenly wake
up to find themselves spinning in the pattern. Stall/spin accidents do
not occur in a vacuum. It is the pilot who, through an incomplete
understanding of stall/spin dynamics and improper manipulation of the
flight controls, actively participates to cause an airplane to stall
and spin. Hence, the true test of the value of spin training should
be, "how likely is a stall/spin aware and properly spin trained pilot
to encounter an inadvertent spin departure in the traffic pattern?"

The FAA attempted to address this issue during their 1976 General
Aviation Pilot Stall Awareness Training Study, Report No.
FAA-RD-77-26. The bottom line: pilots who received better stall/spin
awareness training--without hands-on spin training--were 1/3 less
likely to progress into a spin after encountering an inadvertent
stall. On the other hand, pilots who received better stall/spin
awareness training AND exposure to intentional spins prevented spin
departure following an inadvertent stall every single time. This FAA
study, by the way, has driven all of the changes made to the training
requirements regarding stall/spin awareness since 1976. Those who
oppose spin training, or at least oppose further research into the
possible benefits of such training, steer well clear of any reference
to this FAA study.

The new AOPA study neither explodes stall/spin myths, nor makes the
case against spin training. The study does, however, reinforce the
critical importance stall/spin awareness and prevention must play if
pilots are to avoid fatal stall/spin accidents in the pattern. If
anything, genuine spin training should improve a pilot's ability to
thwart spinning tendencies following an encounter with an accidental
stall. Hands-on spin training, properly conducted, will leave no doubt
in the pilot's mind that spin prevention is crucial when in the
pattern. But equally important is the practical knowledge gained
regarding the mechanisms behind spinning, the importance of adhering
to published operating limitations, and the role misapplied control
inputs play in inadvertent stall/spin departures.

Armed with solid information presented in the proper context, it's
then up to every pilot-in-command to decide whether spin training
should be part of their continuing aviation education.

------END------
Ads
  #2  
Old September 1st 03, 04:03 AM
Chris Hoffmann
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The first thing that jumped out at me from your report is this:

Another myth cited in the AOPA study is "watch your airspeed, or
you're going to stall this airplane!"


Pardon me, but if your airspeed gets below stall speed, you ARE going to
stall. Further, if your airspeed is below the usual 1.3 Vso safety cushion,
you are getting to the point where all it takes is a turn too steep, or a
bit of tailwind, or a yank back on the yoke, and you are LIKELY to stall.
This is not "myth".

On the other hand, this:

"Just don't let airspeed get below a safe value and
stalls are not a problem."


is not an axiom to fly by. Students *should* know/be taught that a stall can
occur at any speed, any attitude, of course. But I see nothing wrong with
training students to keep their airspeed where it's supposed to be in the
pattern and on approach, which, I believe, is the context from which those
two quoted remarks were taken.

--
Chris Hoffmann
Student Pilot @ UES
30 hours


  #3  
Old September 1st 03, 06:49 AM
ShawnD2112
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Chris,

It IS a myth. Stall is related to critical angle of attack and has
absolutely nothing to do with airspeed. The quoted stall speeds are based
on very important assumptions of configuration and power setting. Typically
when people talk about the stall speed of an airplane, they mean V0, which
is clean, flaps up, power off.

You can stall the airplane at Vne if you pull hard enough. There are enough
warbird accidents where the pilot stalled at the bottom of the loop and
flopped flat into the ground to prove the theory.

Shawn
"Chris Hoffmann" wrote in message
...
The first thing that jumped out at me from your report is this:

Another myth cited in the AOPA study is "watch your airspeed, or
you're going to stall this airplane!"


Pardon me, but if your airspeed gets below stall speed, you ARE going to
stall. Further, if your airspeed is below the usual 1.3 Vso safety

cushion,
you are getting to the point where all it takes is a turn too steep, or a
bit of tailwind, or a yank back on the yoke, and you are LIKELY to stall.
This is not "myth".

On the other hand, this:

"Just don't let airspeed get below a safe value and
stalls are not a problem."


is not an axiom to fly by. Students *should* know/be taught that a stall

can
occur at any speed, any attitude, of course. But I see nothing wrong with
training students to keep their airspeed where it's supposed to be in the
pattern and on approach, which, I believe, is the context from which those
two quoted remarks were taken.

--
Chris Hoffmann
Student Pilot @ UES
30 hours




  #4  
Old September 1st 03, 06:54 AM
John Harper
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What's more, it is possible, though difficult, to fly slower than Vs and NOT
stall. Trivially, when the plane is standing on the ground, it is not
stalled.
If you botch a loop you can easily end up inverted at the top of a loop
with almost zero airspeed, and not be stalled. Of course in normal
flight it's very hard to lose speed without stalling, but if you
pull vertical you can do it. It's true that if you're below Vs and
not stalled, you won't have much lift either and you'll be
falling. But the airflow is still attached to the wing, and hence you are
not stalled.

John

"ShawnD2112" wrote in message
...
Chris,

It IS a myth. Stall is related to critical angle of attack and has
absolutely nothing to do with airspeed. The quoted stall speeds are based
on very important assumptions of configuration and power setting.

Typically
when people talk about the stall speed of an airplane, they mean V0, which
is clean, flaps up, power off.

You can stall the airplane at Vne if you pull hard enough. There are

enough
warbird accidents where the pilot stalled at the bottom of the loop and
flopped flat into the ground to prove the theory.

Shawn
"Chris Hoffmann" wrote in message
...
The first thing that jumped out at me from your report is this:

Another myth cited in the AOPA study is "watch your airspeed, or
you're going to stall this airplane!"


Pardon me, but if your airspeed gets below stall speed, you ARE going to
stall. Further, if your airspeed is below the usual 1.3 Vso safety

cushion,
you are getting to the point where all it takes is a turn too steep, or

a
bit of tailwind, or a yank back on the yoke, and you are LIKELY to

stall.
This is not "myth".

On the other hand, this:

"Just don't let airspeed get below a safe value and
stalls are not a problem."


is not an axiom to fly by. Students *should* know/be taught that a stall

can
occur at any speed, any attitude, of course. But I see nothing wrong

with
training students to keep their airspeed where it's supposed to be in

the
pattern and on approach, which, I believe, is the context from which

those
two quoted remarks were taken.

--
Chris Hoffmann
Student Pilot @ UES
30 hours






  #5  
Old September 1st 03, 07:54 AM
Chris Hoffmann
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John - Just to be clear, I'm only referring to approaches. I thought that's
what that part of the original post was about - a student learning to land.

Sean-
How can you say that stalls are unrelated to airspeed, when airspeed is
related to your angle of attack? (and John, at the top of a loop at zero
airspeed, where is the relative wind coming from, or at least about to come
from? Good thing a cliff doesn't magically appear under you at that point.)

You aren't (hopefully) coming in to land at Vne. Yes, you can stall an
airplane at any speed, but the point is you don't want to let your airspeed
drop too low on approach. Period.

Maybe I'm seeing this as two seperate training issues, whereas others are
seeing it as one and the same?

--
Chris Hoffmann
Student Pilot @ UES
30 hours


  #6  
Old September 1st 03, 02:47 PM
john smith
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Chris Hoffmann wrote:
On the other hand, this:
"Just don't let airspeed get below a safe value and stalls are not a problem."
is not an axiom to fly by. Students *should* know/be taught that a stall can
occur at any speed, any attitude, of course. But I see nothing wrong with
training students to keep their airspeed where it's supposed to be in the
pattern and on approach, which, I believe, is the context from which those
two quoted remarks were taken.


And do not forget that stall speed increases with angle of bank and
G-loading.
Look at the POH for the aircraft you fly and find the charts that list
the stall speed at various angles of bank and flaps.
Remember that the listed stalls speeds are for max gross weight, unless
your POH specifically list stall at other weights. Reduce the aircraft
weight and the stall speeds reduce linearly.
If you increase the G-load (positive) you generally increase the stall
speed. Similarly, if you decrease G-load (negative or less than one) you
reduce stall speed.
  #7  
Old September 1st 03, 06:25 PM
Rich Stowell
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"Chris Hoffmann" wrote in message ...
The first thing that jumped out at me from your report is this:

Another myth cited in the AOPA study is "watch your airspeed, or
you're going to stall this airplane!"


Pardon me, but if your airspeed gets below stall speed, you ARE going to
stall. Further, if your airspeed is below the usual 1.3 Vso safety cushion,
you are getting to the point where all it takes is a turn too steep, or a
bit of tailwind, or a yank back on the yoke, and you are LIKELY to stall.
This is not "myth".



Ah, but therein lies the rub! Within the ability of the structure to
withstand G-load without deforming/breaking, the airplane can be
stalled at ANY airspeed. In that context, every airspeed is a
potential "stall speed" provided the G's applied are sufficient to
exceed critical angle of attack. "Getting below stall speed" is only
meaningful if the instantaneous G-load is specified.

For example, if I pull 3.8 G's while at Maneuvering speed, Va, the
airlane will stall (Va = 1.95Vso). If I am in wings-level flight (1
G), then the stall speed is Vso. An infinite number of G and speed
combinations exists in between Va and Vso that will result in a stall,
even 1.3Vso is a stall speed at the appropriate G-load (G can also be
interpreted as bank angle).

Airspeed alone means nothing with regard to when or whether the
airplane will stall. We need to think in terms of airspeed AND G-load
-- these are the two parameters that will give us a clue as to our
margin to the stall, or whether or not we are moving closer to, or
farther from, critical angle of attack.

To reduce the likelihood of stalling: If airspeed is decreasing,
G-load MUST also decrease; if airspeed is increasing, then the
airplane can tolerate an increase in G's. We need to develop a sense
of changes in both speed and G to have any reasonable chance of
sensing our proximity to stall.

Also, even the AOPA study correctly identifies the "watch your
airspeed" statement as a myth. I was just expanding on it...



On the other hand, this:

"Just don't let airspeed get below a safe value and
stalls are not a problem."


is not an axiom to fly by. Students *should* know/be taught that a stall can
occur at any speed, any attitude, of course. But I see nothing wrong with
training students to keep their airspeed where it's supposed to be in the
pattern and on approach, which, I believe, is the context from which those
two quoted remarks were taken.


Sensing airspeed AND G-load trends are critical, not airspeed alone.
The V-G diagram is the best illustration of the interaction of speed,
G, stall, and structural damage.

Be Safe,

Rich
http://www.richstowell.com
  #9  
Old September 1st 03, 08:30 PM
Wayne
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Since the airspeed indicator (pitot tube) is pointed the same as the
wing, then "indicated airspeed" does mean something. For instance, if you
were to put the wing at a 90 degree AOA to the relative wind, then the
airspeed would also read nothing or almost nothing correct?

So I agree that airspeed doesn't matter, but indicated airspeed does.

Wayne



Remove "bra" and "panties" to reply

Airspeed alone means nothing with regard to when or whether the
airplane will stall. We need to think in terms of airspeed AND G-load
-- these are the two parameters that will give us a clue as to our
margin to the stall, or whether or not we are moving closer to, or
farther from, critical angle of attack



  #10  
Old September 1st 03, 09:18 PM
Chris Hoffmann
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Airspeed alone means nothing with regard to when or whether the
airplane will stall. We need to think in terms of airspeed AND G-load
-- these are the two parameters that will give us a clue as to our
margin to the stall, or whether or not we are moving closer to, or
farther from, critical angle of attack.


......But won't airspeed alone change the "cushion" that you have to maneuver
with? A steep turn at 90 kts isn't usually a problem. Doing something like
that near Vso on final will almost certainly be one. As you point out, at
lower airspeeds the aircraft will stall with less of a load.

I don't dispute that there's more to stalls than airspeed. I just think
you're all putting too fine a point on this. If the hypothetical instructor
said, "Watch your airspeed, or you'll reduce the amount of G-load that the
airplane can handle and may invoke a stall if you decide to maneuver
drastically", then you probably wouldn't have a problem with it, but in the
time it took to say all that, the instructor and student would be hitting
the ground! Proper instruction of what causes a stall is one thing. Not
letting your student get out of control on an approach is another.

Let's "approach" this another way: You're the instructor in this case. Do
you want your student to maintain a certain airspeed on approach? If so,
why? And if they allow the plane to get below that speed, what are you going
to say to them?

--
Chris Hoffmann
Student Pilot @ UES
30 hours


 




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