Colyn asks:
<<<
Brent,
Where does the lack of gyro come
in to play? are you saying a CFS doesn't know which way is up if the
pitot is blocked?
>>>
No. What I am saying is that the Pilot doesn't know which way is
up if the pitot is blocked. To appreciate why, you must understand the
underlying dynamics.
Reality is what our individual brains perceive it to be. That
perception is shaped by our experiences and the functional dynamics of
the human mind. Most (~90%) of the mind's processing occurs below the
cognitive level by what is commonly referred to as the subconscious or
"child" mind. If we needed to think about every action (heartbeat,
breath, walking, blinking) there would be no time to invent things like
airplanes. The conscious or "adult" mind is where reason, calculation
and other forms of abstract thinking occur. It is a thin veneer that
upon which all of human accomplishment is built. Our sapience,
however, is shaped by the subconscious it covers. Think paint. Now
DON'T think of a rainbow.
Thinking of a rainbow? Of course, that is your subconscious at work.
The relationship between the adult and child mind is poorly perceived
because the adult mind does all the high order thinking and is
predisposed to ignore the existence of the child mind. There are
protocols that regulate the interaction between the two minds. In most
cases the child mind relays an impulse, fear, desire to the adult mind
where it is rationally considered and weighed against present and
future factors. The child mind wants ice cream and cake for dinner but
the adult mind doesn't want to die of obesity and malnutrition. This is
why we eat broccoli.
The child mind is able to wrest control from the adult under certain
limited circumstances. We generally refer to this as "panic". If it is
perceived that a big rock is on a collision course with the cranium,
the command to "duck" bypasses adult consideration and is acted on
immediately.
Sometimes the adult abdicates control. If the tasks managed by the
adult mind are to numerous or too complex, the adult mind tends to
fixate on a single problem, leaving the balance to fate. This is why we
train. Training teaches us how to perform a task with a minimum of
cognitive bandwidth. The problem is that the adult mind has no idea
about the child's competence at a given task. The adult mind thinks
that everything is fine if a task can be accomplished successfully even
if it takes 99% of the adult mind's ability. The adult mind is one
distraction away from failure but it has no metric to quantify the
situation. Like the captain of a ship, the adult mind is confident in
it's own ability, even if that confidence is unfounded. We call this
"ego".
Ego is deadly to a pilot. Most Lancair accidents are ego related. The
outside observer wonders "How could he do something so stupid and ill
advised?" The answer is simple, ego. the pilot believed that his
ability was ample to the needs. Lancair pilots are already sorted for
an abundance of regard for their own ability. Who else would believe
that they can build a machine that will carry them safely five miles
above terra firma at half the speed of sound? I built this fantastic
airplane, do you think a little weather can stop me???
I never met Mr. Ainsworth but I would wager that his ego was
particularly corpulent. His panel shows someone who valued form over
function. He must have been convinced that his view was superior to all
others. In his world he was never wrong. It is what likely precipitated
his untimely death.
You have just finished a climb to FL200 and are penetrating cumulus
tops. You have forgotten pitot heat and the pitot tube has iced over.
Your airspeed indicator is showing a decay and you receive a stall
warning from the EFIS. Engine instruments are outside your scan and
you conclude that your actual airspeed has decayed. After all, you
cross checked the Dynon to the CFS and you got an aural warning, three
pieces of information that concur so you must be too slow so you nose
the airplane down. Oddly, the airplane resists even thought the
airspeed has not recovered. You trim the nose down. Now you
notice an unusual attitude indication. There must be something wrong
with the electrics as the Dynon has gone blank. As you troubleshoot the
problem you notice a slight shutter in the airplane. This is you last
thought because that shudder is the beginning of a torsional flutter
failure of the empennage. Upon empennage failure the nose drops with
such rapidity that the aircraft experiences an 11 G negative
acceleration, throwing you into the overhead and failing the right wing
at the root. If you are not dead now then you will be in 50 seconds
when what is left of the fuselage rejoins the earth.
So what happened? You thought you had three
indications that the airspeed was low when in fact all three depended
on a single source (pitot tube). You were so busy analyzing the
airspeed issue you
forgot that the airplane is trimmed for speed, not attitude and would
likely nose down by itself if the airspeed was really falling. You did
not have the engine instruments in your scan so you did not consider
that the engine was still making power. You did not have an independent
altimeter in your scan to show you that, miraculously, you were flying
at 90 KIAS in level attitude and holding altitude. You did not remember
that the airspeed measures the differential pressure between pitot and
static so as your static pressure climes in the dive the differential
pressure (indicated airspeed) drops. You did not have an independent
attitude indicator to verify that the unusual attitude indication was
due to an unusual attitude, not a electrical failure. That "blank"
Dynon was an accurate view of the earth "ahead".
The time elapsed from onset to failure was 35 seconds. Of that you
would have 20 to 25 seconds to recover. Thirty heartbeats. No time to
go hunting for the information you need that is scattered across
hectares of instrument panel whose configuration is an homage to
feng-shui. No time to scroll though pages of displayed information. The
information you need to cross check a spurious reading needs to be in
a narrow cone of vision NOW. BTW, reading this short paragraph used up
all of your recovery time. You are now dead.
Why rotating mass attitude as a standby? Two reasons. In the case of
the airspeed you had three sources of information that were reporting
on a single measurement. If the source fails they all fail. A better
plan is to have completely redundant systems. A better plan still is to
have redundant systems that rely on different principles of operation.
This way, if they agree, you can be confident you are seeing the truth.
The other reason has to do with training. Unless you did your
instrument training behind an EFIS you have and instinctive trust in a
attitude indicator. You were trained that a mantra of "trust your
instruments" will lead you from the confusion of spatial
disorientation. The voice of this trusted
friend will be clarion among the cacophony of a helmet fire. Besides, your subconscious, child mind likes that
spinning top thingamajig.
Arrange your instrument panel in a way that is familiar or risk
resetting your training clock to zero. Be sure that essential
instruments needed to deal with emergency situations are immediately
available directly in front of you. Make them your habit as those
habits will save your ass.
If you don't learn from the mistakes of others then others will learn
from you.
Regards
Brent Regan
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