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Rick writes: "Compression ratio and air will not
break an engine."
It would be more accurate to say that these elements alone
would not break an engine. Of course, you cant break, or run, an engine
without them either. If we apply this same logic to guns we can state
that a gun alone is safe. It is the bullet that is dangerous.
The simple fact is, as the data will show, the engine in question was
already most of the way back to bauxite before the crash. The
supercharger did not "cause" the engine to melt down and the engine
failure did not "cause" the crash. Many engines run with superchargers
for thousands of hours and there have been more successful dead stick
landings than fatal ones.
In this unfortunate instance the conditions of the operation of the
engine exceeded its endurance limit. This precipitated a situation
where the demands on the pilot exceeded his ability. These are the cold
facts.
The tendency is to reduce all accidents into a causative element or
elements. This frequently results in pointing to a mechanical element
that, for its inadequacy, induced the unfortunate event. In many cases
there is a common causative element that is not mechanical. It is the
decision chain of the pilot. In some cases pilots knowingly make a poor
decision thinking they will be able to recover through a good decision
or superior skills later. In other cases, pilots make a poor decision
based on incomplete or inaccurate information.
Some decisions are made hours, weeks or even years prior to when the
totality of circumstances culminate. If you start with the assumption
that we are all well trained and rational pilots who will make the
correct decisions given the opportunity then the real risk comes with
the introduction of ignorance to the equation. Ignorance of potential
consequences has resulted in decisions that catalyzed many of the fatal
accidents that have claimed members of our community. Our enemy is
therefore the unknown unknowns. How can we possibly armor against this
ignorance? The problem is exacerbated by the nature of homebuilt
aircraft where we are taught, by experience, that we have the
capability to build a machine that can hurtle our bodies through the
rarefied atmosphere five miles above terra firma at half the speed of
sound. Surely we have the wisdom to make ANY decision regarding the
operation, modification and maintain of what we built, damn it!
We must remind ourselves that there is a vast gulf between building
something per plans and fully understanding the design elements and
their interaction. Even among trained engineers there is a tendency to
evolve a design to failure. Human endeavors are punctuated by
engineering failures that are a consequence of engineers standing on
the shoulders of their predecessors thinking they can take just one
more step up. Indeed, this is the "Peter Principle" of engineering
where designs evolve to ultimate, and frequently catastrophic, failure.
We see this "evolution towards failure" in the ever increasing gross
weights, modification of structural elements (e.g. hinged access hatch
on the IV tail), power increases, stretching of the CG envelope and
others.
As a general rule, builders should not vary from the plans AT ALL
unless they are qualified to evaluate the full impact of the change or
they have consulted with someone who is qualified. In the end, it is
the builder / pilots responsibility to verify that the aircraft is
flight worthy within its operational envelope.
How does one determine if they are qualified to make design changes?
There is no way that a builder can answer the question "Have I thought
of and considered all of the important issues?" without asking someone
else who is qualified. I am often amazed at the scope of things I do
not know and use this knowledge of ignorance to humbly approach an
engineering problem.
Despite the fact that I designed my fist turbocharger installation when
I was but 17 years of age and that I had built and modified hundreds of
engines since, when it came time to design a turbocharger installation
for the Lycoming in my Lancair I accepted the fact that I knew nothing
about aircraft engine turbocharging. After researching
the problem and designing the fundamental system, I hired a retired
engineer from Garret to review my design and make recommendations.
Despite my best efforts I had designed a system that would experience
compressor stall (flame out) above FL190 if the engine RPM was reduced
below 2400 RPM. OOPS. The engineer recommended a different turbine
housing and controller that would allow the system to perform to
FL380+. Money well spent.
Back when I could tolerate having employees, from time to time I would
interview job applicants. Part of the interview was to have them
explain to me the meaning and importance of the following terms:
Resonate Frequency
Young's Modulus
Euler Buckling
Extreme Fiber (Hint: Not a breakfast cereal)
Section Moment of Inertia
Harmonic Frequency
Coefficient of Thermal Expansion
Tensile Strength
Yield Strength
Torsional Modulus
Centroid
Fatigue Limit
Spring Rate
Coefficient of Friction (dynamic and static)
Poisson's Ratio
I would also ask them the following: " Imagine there is a railroad
tract that girdles the Earth at the equator. Due to rising ocean levels
the track must be raised by 1 meter over the entire circumference
(assume a track length of 42 million meters). How much total track must
be added to accommodate the elevation change?" You have 30 seconds to
answer. (answer below)
To be considered for a position as a mechanical engineer they had to
know them all. Do you? If you don't (and even if you do) then I would
recommend that you seek a second, and third, opinion before deviating
from a "known good" design. In no way am I calling for the end of
innovation but rather I am emphasizing the importance of comprehensive
approach to innovation.
Remember that any component, certified or not, built to specification
or not, can be driven to failure by ignorance.
Regarding the unfortunate postings of the past days, I would remind the
contributors that this is a public forum and that your words can be
used against you in a court of law. Even a well meaning statement like
" I do know all the issues with supercharging and pass all the
information on to my customers. That is why
only people I know and trust can install my systems."
can be used by plaintiffs' attorney as a bludgeon. For example: "Would
it be fair to say, Mr. Defendant, that IF you knew ALL the issues and
the pilot burned up the engine because he misused it, then YOU must
have FAILED in communicating ALL the information to the customer?" This illustration is, of course, not my view but as
an engineer I must consider the worst that can happen. Pilots understand that it is the pilot's responsibility,
not the vendors, to properly operate his airplane, but how many juries
are composed of pilots?
As to what someone may or may not have said as relayed by a third
party, the courts typically do not allow hearsay testimony for good
reason. It is my experience that both parties are intelligent,
reasoned, articulate individuals who are quite capable of resolving
their personal grievances IN PRIVATE. Public attacks and counter
attacks only serve to diminish the respect and respectability's of all
parties regardless of the righteousness of any claim.
I should know as I am guilty of the same and have lived to regret it.
Regards
Brent Regan
2 Pi meters or about 22.4 feet. Most candidates guess a much larger
number.
BR
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