| A thought provoking safety article. Read it. It introduces
Haddon's Matrix - an Accident
Investigation and Review Matrix which takes a single crash and divides
it into pre-crash, crash and post-crash phases.
This article is published and revised with the kind permission of
SOARING - the official magazine of the
Soaring Society of America, Inc.
Last Revised: Nov 12, 1999
AN ALTERNATE VIEW
We have a problem with soaring safety, I think we'll all agree.
And we are contributing to the problem by our single-minded
insistence that better flight training is the cure to the problem.
"Wait a minute." most of you are saying. "What kind of heresy
is this? The pilot is the one responsible for aircraft accidents,
so better flight training will prevent accidents by getting to the
source of the problem. Right? And all these wimps that want crash-survivable
cockpits should just realize that if they don't have the crash in
the first place they don't need a crash survivable cockpit. So, just
train them better!"
As you may have guessed, I don't agree with this philosophy, and
will try to show you why in the course of this article. But before
I leap into this any farther, I want to make one thing very clear.
I am in favor of improved flight instruction. I am a CFIG and am very
aware of the benefits of good flight instruction. This must continue
but we must not put all our safety eggs into any one basket. Whether
it be labeled "flight instruction" or "crash-survivable aircraft".
How did I get interested in all this? I had the good fortune to be
able to attend a CFI Revalidation course given last February by one
of the leading instructors in our sport. I would recommend it to anyone.
It was a full twenty-four hours of classroom instruction, and was
uniformly superb, with the exception of about two minutes.
Early on the first day, the instructor reviewed the accident data
for the previous couple of years, making occasional comments along
the way about how specific accidents occurred and could have been
prevented. When he finished, he sat back and said something to the
effect that better flight training was the only way to reduce the
accident rate in soaring, and that we as instructors, need to work
harder to make sure our students were better pilots.
The rest of the class murmured assent, but I raised my hand and made
a comment to the effect that flight instruction wasn't enough, and
that perhaps we need to consider doing other things. I specifically
mentioned launches and landing areas as areas that could be improved.
The instructor gave me a paternalistic smile, and asked me if I didn't
think that we wouldn't need safer launches and landing areas, if only
we had safer pilots.
I responded in a less-than-organized fashion, I'm afraid. He had
caught me off guard, because I thought that some of the ideas I am
about to explain to you were self-evident, and required no defense.
Consequently, I was not well prepared to defend those ideas to one
of our sport's leading flight instructors. I made a few statements
about the three phases of the crash sequence, and how there are things
which can be done in each to reduce the injury burden, but my classmates
did not appear to be very interested, so I let the issue drop.
What I had assumed to be the common wisdom about aviation safety
was not acknowledged as such in at least part of the soaring community.
Many in our sport, I now believe, have not considered some of the
ideas which I am presenting here.
What is it we're really trying to do with soaring safety programs?
If I went to a soaring convention and asked 100 people that question,
I'd be willing to bet that at least 90 would say "prevent accidents".
I do not believe that all accidents are preventable. People are just
too different from each other and too difficult to communicate with
to make sure everybody gets the message about how to prevent accidents.
Even if you could get the message to everyone, there are some people
who'll try something simply because they've been told not to. We all
know people like that.
I will submit to you that what we are really trying to do is prevent
injuries. (For the purpose of this article, "injuries" will also include
fatalities) I would much rather see a glider destroyed than to see
someone injured, even a little bit, or killed. I would not want to
share a thermal with someone who cares more about his ship than either
himself of me. Dr. Whitehead summed it up will in his October, 1987
letter to SOARING, when he quoted "Good judgment is based upon experience,
and experience is the result of bad judgments." Our goal should be
to protect people while they're gathering that experience.
Public health professionals who work in the safety field are now
using the term "injury control" to describe what they do, instead
of the previously popular "accident prevention" This term more accurately
describes the objectives that I believe are the true goals of soaring
Why do I say that more and more flight instruction is not the answer
to the problem? Economists have a concept that they call The Law of
Diminishing Marginal Returns. Simply put, it says that for each additional
unit of any given input (read "flight instruction") the amount of
output it generates (read "soaring safety") gets smaller. In the soaring
environment it can be assumed to mean that the first hour of flight
instruction is much more effective than the tenth which is much more
effective than the thirtieth, and so on. At some point the return
on the effort expended by the instructor is zero. If at this point
the pilot remains one with poor judgment or is unsafe in any other
way, further flight instruction is not going to help. If your goal
is to protect him from injury, you must do so some other way.
ANECDOTE When I was flying gliders out of Jack Frost's strip
in Robert Louisiana there was a middle-aged gentleman who flew there.
He had lots of flight instruction, had his commercial rating, and
was talking about getting his CFI-G. He was also sponsoring the flight
instruction of a young boy who had just turned fourteen. The man seemed
to be something of a father figure to the boy, at least at the gliderport.
This boy had been flying with an instructor for about two years and
actually had been ready to solo for months. On his birthday, of course,
he was soloed and rapidly transitioned into the 1-26.
Soon the boy began to be slightly overconfident of his abilities
as many post-solo students will be. One Saturday he landed quite long
and brought the aircraft to a rapid, but not spectacular halt just
short of the barbed-wire fence at the end of the roll out area. He
seemed quite pleased with his ability to control the aircraft so well.
The middle-aged gentleman took him aside and counseled him about showing
off. He explained that we should all set good examples for each other.
It was a very reasonable discussion demonstrating good judgment on
the part of the middle-aged gentleman clearly setting a good example
for the boy.
I'll bet you can guess what happened next. The middle-aged gentleman
took the same 1-26 for a flight and when he landed, had to make a
screeching nose-skid-in-the-dirt stop in order to avoid running into
the same barbed-wire fence. When he got out, he was not embarrassed
by the series of bad decisions he had made to get himself into that
situation, but was proud of his ability to bring it off so masterfully.
He seemed particularly proud that he thought of doing a deliberate
ground loop, then realized it wasn't necessary. The middle-aged gentleman
obviously knew what proper judgment was, he had just explained it
to the boy. Whenever he flew with an instructor, he did an excellent
job and demonstrated good judgment. So would more training have resulted
in increased safety? I think not.
THE MORAL If you want to protect this pilot from injury, you
would have to do it with something other than more training. More
rides with an instructor just wouldn't have much effect on someone
We are today in soaring where the automotive
safety movement was about thirty years ago. During the 50's, virtually
all auto accidents were assumed to be "driver error". In fact, the
California Highway Patrol accident reports of that era listed 18 possible
causes for accidents 16 of which were some variation on "driver error".
So how did the improved automotive safety situation come about? Where
did collapsible steering columns, breakaway sign posts, guard rails
that work properly, and airbag technology come from?
During the 50's and 60's many people began to look at the problem
and realized that a lot of people were being injured on the highways
is spite of excellent education programs. They realized that no matter
how well you train people, somebody will do something stupid and get
into an accident. If you don't do something to protect them, then
you're saying that if they're dumb enough to get into an accident,
they deserve what they get.
Consequently, many of these people began to develop ways to limit
the number of injuries resulting from vehicle accidents, other than
by attempting to alter driver behavior. One of the tools they have
found useful to organize their thinking about possible ways to intervene
is to take a single crash and divide it into pre-crash, crash and
post-crash phases. The questions asked then revolve around what can
be done during each of those phases to reduce the injuries resulting
from the crash.
They borrowed a concept from public Health: an epidemic of an infectious
disease is often studied from the standpoint of the Agent (the bug),
the Host (the Human with the disease) and the Environment (which often
helps to transmit the disease). Aircraft accidents and the injuries
associated with them can be considered a type of disease, and therefore
can be approached in a similar manner. In this special case the three
factors are called the Human (the persons on board the glider), the
Vehicle (the glider itself) and the Environment (everything external
to the other two)
Combining these two approaches results in Haddon's Matrix,
named for the automotive injury specialist who devised the concept.
On the vertical axis are pre-crash, crash and post-crash phases. On
the horizontal axis are Human, Vehicle and Environmental factors (see
Figure) This produces a matrix with cells numbered from one to nine.
Each cell represents an approach to reducing the injury burden resulting
from a glider accident.
Filling in the cells is an excellent exercise for glider clubs to
perform at safety meetings, or for flight instructors to do with their
students. Doing so will start people thinking about what can be done,
and will allow the peculiarities of one's particular environment to
I'll give examples for each cell. These are not to be considered
complete in any way, and should be augmented by all who read this
Most people's old favorite, improved flight instruction, would belong
in Cell one. This is because the goal of improved flight instruction
is to alter human behavior ( the pilot's) in the pre-crash phase.
This leaves eight more areas in which the injury burden can be reduced,
which is why I say we need to think about other ways of approaching
An example of something else that might be done in Cell One would
be to ensure that we don't go flying unless we are physically prepared
for it: no drinking, and no flying while sick.
Cell Two opens up possibilities for interventions relating
to the human tolerance of crash forces. How might we intervene?
Discourage unpadded harnesses? Require flack jacket material
in the torso area of the harness? Demand harnesses with shoulder restraint
lines to reduce head down crash impacts? How else?
How about helmets? Many Army aviator's lives have been saved in low-speed
crashes because they were wearing (impact) certified helmets.
The motorcycle experience is well known to be an emotional issue with
some but the evidence is clear: head injuries are less severe with
helmets. Since typical glider speeds are similar to motorcycle speeds
it follows that the forces involved are similar. Wearing (certified)
helmets is an idea worth considering. (Note: Wearing helmets is mandatory
under Transport Canada Regulations.)
In Cell Three the Crash is over so this one is concerned with
how to reduce the degree of damage done by the injuries already sustained.
First Aid training would be useful so a pilot could attempt to slow
or stop his own bleeding, or know what to do if he suspects that his
neck has been injured. Placing survival gear onboard the aircraft
during preflight is an example of how to reduce injury in the post-crash
Cell Four concerns itself with insuring that the glider is
ready to fly. The preflight inspection is crucial to this as well
as the annual inspection with a checklist, and an uninterrupted preflight,
In Cell Five would go all those things about the glider which
could cause or worsen injuries during the crash phase. Knobby instrument
panels and a non-crashworthy design are examples of points in this
cell. Interventions could include rounded nonprotrusive insturments,
airbags and energy absorbing keel extensions at the nose of the glider.
Cell Six relates to those aircraft factors which could make
injuries worse after the dust settles. The ability to get out of the
harness is important here. Are the edges of the fractured materials
sharp? Have the oxygen fittings broken away in a safe manner (without
leaks)? In a mid-air could the pilot clear the wreakage or would they
have difficulty getting their reserve parachute out? Was the accident
scene readily accessible to emergency vehicles?
Cell Seven concerns how the environment could be improved
during the pre-crash phase. Weather awareness, proper use of Flight
Service Station weather briefings are good examples. Airfield maintenance
is important here. Did that last big thunderstorm leave an erosion
ditch on the grass runway? Don't tell the tug pilot he should
try to miss it on his landing: simply repair the damage. What about
the obstacles on either end of the runway? Trimming back the trees
or placing telephone lines underground could help make the approaches
and takeoffs safer.
Cell eight refers to those aspects of the environment which
endanger the pilot during the crash phase itself. If obstacles are
not essential such as a fence, signs, or trees, why not remove them?
Trees can be replanted in other areas to provide asthetic appeal to
the landowner and still provide safe flight approaches.
Cell Nine is about how the environment responds during the
post-crash phase. How prompt and competent is the emergency medical
response system? Does anyone in the field have first aid training?
Even if someone has training, are adequate first aid supplies available?
As I said before, I did not attempt to make this chart complete:
that would be a good exercise for individual pilots, gliderport operators,
students and instructors, club safety meetings, contest pilot meetings,
convention seminars, and anywhere else people gather to discuss soaring
safety and how to improve our safety efforts.
ANECDOTE When I began flying at Stennis International Airport,
outside Bay St. Louis, Mississippi, we had a near-ideal field off
of which to fly. There was an 8000 foot long, 200 foot wide concrete
runway with a taxiway joining it at about the middle. There were wide,
flat, smooth, grassy areas on either side of the runway which were
used for the bulk of the soaring activity. Takeoffs, regardless of
direction, began at the taxiway and had long, clear areas without
obstruction for at least 4000 ft. Landings, by convention ,were ideally
to end up near the taxiway, to make positioning easier for the next
takeoff. All one had to do was to pull the aircraft across the taxiway
and you were ready to go.
There were no signs, lights or other obstructions near the taxiway,
so an inadvertently long landing merely involved rolling across the
taxiway. Even if there was an aircraft present, waiting to takeoff,
there was usually enough room to maneuver to one side without a problem.
Since there was nothing to run into, this was highly unlikely to result
in bodily injury (although you were guaranteed verbal injury from
Andy Ewing, the airport operator, if he saw you roll across the taxiway.)
Shortly before I left that part of the country, airport expansion
began. One of the first things the FAA required was a prominent sign
on the taxiway announcing that you were about to enter the only runway
on the airfield (or in the county, for that matter).
The specifications were rather rigid. Naturally, it had to be a certain
distance from the runway. Also, of course, it had to withstand the
hurricanes which frequent the area. This meant that it was firmly
planted in concrete, with thick support beams. That sign wasn't going
anywhere! The sign sat exactly in the middle of the roll out area
for a south landing (naturally, the most frequently needed on the
Gulf Coast) It was end-on to the landing gliders, sitting like a blunt
knife waiting to crumple some fiberglass of aluminum, and the softer
How did the glider operation respond to this threat? Surprisingly,
few people questioned the safety aspects of the sign's installation.
Those who did were told not to hit the sign, make sure your landings
are short enough to avoid it. An alteration of pilot behavior was
proposed as a cure for an environmental problem which could have been
solved in other, better ways.
What could have been done? Mounting the sign on breakaway supports
would have helped, but moving it a few feet farther from the
main runway (off the glider runway entirely) would have been even
CONCLUSIONS When one is discussing how to make something safer,
one has to consider the question of active versus passive safety measures.
An active measure is one that the person being protected must take
it upon himself to do, such as buckle a seat belt. You must actively
do this, or you won't be protected. A passive measure is one which
will operate whether you want it to or not, such as an automatically
inflating airbag. It just sits there unnoticed until you have a car
wreck, then if inflates and prevents injury. Obviously, a passive
measure is better than an active one.
Let me draw an analogy which I hope will make this clear. Suppose
your concern was to prevent people from getting sick from drinking
contaminated water. If you go the active route of trying to alter
the people's behavior, you could teach people what bad water looks
and smells like, and give them test kits to check the water before
they drink. I would guess that you would still have people drinking
bad water, and getting sick because of it. It is simply human nature
to do things like that.
On the other hand, you could take a passive approach to preventing
this kind of illness. You could, as a municipality, provide a water
treatment plant to purify the drinking water for your town. People
don't have to know anything other than how to turn on the tap, and
they'll be protected from the diseases associated with bad water.
The sign at Stennis Field is an example of this. The passive approach
of altering the sign would have been better than the active approach
of trying to alter the behavior of every pilot flying there. Only
one pilot would have to make a mistake and a disaster would occur.
Moving the sign would eliminate the problem, in a passive manner.
Soaring safety is a lot more than good flight instruction. It involves
looking at the pilots, the aircraft we fly, and the environment in
which we fly them. It involves reducing the risk in ways other than
by saying, "Don't do this!" and "Don't do that!" It involves
looking at our operations, and seeing if they can be altered in such
a way so that it is impossible to do "this" or "that". It involves
making sure that, if "this" or "that" happens anyway, nobody gets
hurt as a result of it.
Changes in the environment have an effect on soaring safety, and
we need to consider them when we evaluate the "big picture". Attempting
to alter pilot behavior is a possible cure for an environmental problem,
but it is not necessarily the best one. Mostly soaring safety involves
the willingness to spend some time thinking about things from a safety
standpoint, and then being willing to act on the ideas which are generated.
Soaring safety is in our hands. Let's not botch the job, just because
we're not looking at all the possibilities.
ABOUT THE AUTHOR Bob Weien first soloed a glider in
1975 but has done most of his soaring since he got back into the sport
in 1981. He holds the ratings of Commercial Pilot, Helicopter and
Glider, and is a CFI-G. He got his start flying helicopters for the
US Army, and is now an Army Flight Surgeon. He is a graduate of the
Aircraft Crash Survival Investigators School in Tempe, Arizona and
well as USC's Aircraft Mishap Investigation Course. He has a Doctor
of Medicine from LSU, and a Master of Public Health from Harvard University.
Currently, he is a Resident in Aerospace Medicine at the US Air Force
School of Aerospace Medicine at Brooks AFB, Texas.
Another proactive OCHS Matrixes (investigative
techniques) which coincidently also completely ignores the
accident in itself is the Risk Matrix:
This matrix is used to determine whether or not there is a need for
an investigation (since it is not possible or practicable to investigate
all incidents) or what depth that investigation needs to go to.
It is also a very useful tool for evaluating all factors leading
up to an accident in order to determine root causes.
* Scenario: You are a happily married man. All of us
at one time or another have faced the hissy fit when we leave the
toilet seat up. A wife who stumbles into the bathroom in the middle
of the night, only to sit on a dirty toilet bowl is not a happy camper.
The risk of that happening is not that high. We have all learned
the concequences only too well. But the concequences of a memory lapse
can be quite high.Correct? Lets say a "9" on our risk matrix - none
of us relish the prospect of sleeping on the living room couch!
Now introduce a young boy into the family, and Junior, well, his
aim during toilet training is not too good right now.
It is a fairly simple matter to explain to the wife that her quality
of life is going to improve dramatically if we make a policy that
the bathroom toilet seat is left up from now on... and just like that,
the result is a complete turnover in our safety culture - and a delightful
return to a male-dominated society.
This therefore was an incident that was worth while to investigate,
and which obviously resulted in several benefits and reduced "costs"
(in this case, marital.)
The benefit accrued from assessing the risk and issues from not
one, not two - but three different vantage points. That is
the lesson, and the message of Risk Assessment. Look at the hazard
from all possilbe points of view.
* Thanks to Canada's Armed Forces, Aviation Safety.