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nuckolls.bob(at)aeroelect
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 Posted: Fri Oct 16, 2009 9:50 am Post subject: Bells and Whistles |
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At 07:57 PM 10/15/2009, you wrote:
| Quote: | Bob,
Are you also opposed to the flap positioning systems that are available to set flaps to preselected positions? |
I am CAUTIOUS about any system that imparts motion
to flight control systems with motors.
| Quote: | And opposed to the trim speed adjustment devices that change the trim speed at a chosen airspeed?
Similar devices aren't used on certificated aircraft? |
Sure, they're called autopilots.
I've been to OSH about 14 times in the past 24
years. Many starry-eyed entrepreneurs in the OBAM
aircraft market have offered a host of capabilities for
any number of "accessories". It was interesting
to consider the market potential for these products
and probability that the hopeful seller could bring
it to market.
One question I always asked was, "In what ways
can your device INCREASE risk for an unhappy day
in the cockpit?" Most were surprised. Some had
considered failures but virtually none had explored
the question to the breadth and depth dictated by
lessons-learned in the TC aircraft world.
My first opportunity to control motors driving
flight surfaces was to craft a servoed, multi-speed
trim speed controller for the 50 and 30 series Lears.
Fortunately, this was a relatively simple task because
the basic manual system already had control protocols
in place that required TWO failures in of a manually
operated system to occur before un-commanded motion
could take place. Further, any single failure was
to be detectable by a pre-flight/in-flight operable
warning system.
That experience laid the ground work for future
projects where failure mode effects analysis
was perfected to insure that no single event
of worse than 10 to the minus 6 failure rate
could cause un-commanded motion. Pre-flight
testable monitoring system were put in place
to detect and sometimes prevent other failures
from proceeding too far. Increasing levels
of automation (sometimes involving software)
increases the levels of concern exponentially.
When I read that my brothers in the OBAM aircraft
venue are adding what appears to be purely
convenience features to controls for motor driven
flight surfaces, some well worn flags go up in
my head. There are time proven methodologies for
conceiving, developing, prototyping, testing,
manufacturing, installing and maintaining such
systems.
I cannot "object" to the incorporation of such
devices . . . the builder's design goals are
their own. I'm only warning that what might appear
to be a "really neat" thing to do can offer
un-expected and perhaps hazardous increase in
risk. The first question I always ask: "What's
the value added for this new electro-whizzy.
Does the value added more than offset the
cost of a prudent development program?"
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
[quote][b]
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Speedy11(at)aol.com
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| Posted: Sat Oct 17, 2009 6:16 pm Post subject: Bells and Whistles |
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Bob,
I understand and concur with your concern.
For example, I prefer manual flaps over electro-whizzy ones, but I can't argue that there are many applications where powered flaps (electric or hydraulic) are desirable. There are failure modes associated with powered flaps that may cause potentially unsafe situations. However, those failure modes are considered an acceptable risk when weighed against the convenience.
I have to then challenge you and suggest that having (as an example) airspeed sensors that can disable powered flap activation when IAS is excessive may be a convenience worth having despite it's potential failure modes. That is not to say that said sensor need not be robust - I would assume that robustness would be expected. I believe the application of such a sensor to a perceived need could be worthwhile.
The Vertical Power concept takes this discussion to a new level. While I prefer having manual activation of most of my switches and controls, the Vertical Power ideas are certainly viable.
Experimental aviation is where many (if not most) advances in aviation occur. I say lets continue to advance aviation by expanding ideas and concepts - including new electro-whizzys. We don't have to stay with wing-warping just because it resulted from a prudent development program. Although ... maybe we need to consider it once again in today's environment. Hmmm ... any experimental aviation nuts out there willing to rework the wing warp idea?
Stan Sutterfield
| Quote: | The first question I always ask: "What's
the value added for this new electro-whizzy.
Does the value added more than offset the
cost of a prudent development program?" |
[quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Mon Oct 19, 2009 5:24 am Post subject: Bells and Whistles |
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At 09:14 PM 10/17/2009, you wrote:
| Quote: | Bob,
I understand and concur with your concern.
For example, I prefer manual flaps over electro-whizzy ones, but I can't argue that there are many applications where powered flaps (electric or hydraulic) are desirable. There are failure modes associated with powered flaps that may cause potentially unsafe situations. However, those failure modes are considered an acceptable risk when weighed against the convenience.
I have to then challenge you and suggest that having (as an example) airspeed sensors that can disable powered flap activation when IAS is excessive may be a convenience worth having despite it's potential failure modes. That is not to say that said sensor need not be robust - I would assume that robustness would be expected. I believe the application of such a sensor to a perceived need could be worthwhile.
The Vertical Power concept takes this discussion to a new level. While I prefer having manual activation of most of my switches and controls, the Vertical Power ideas are certainly viable. |
All the above is non-quantifiable and subject to
comparison with business models as a "viable"
product and failure modes as a "low risk" product.
I don't think I offered anything as a recommendation
to be challenged. I was only suggesting that when
it comes to automated systems there is an increased
risk of pilot inattention and dependence on that
automation. There is also a common-sense observation
that hooking motors to flight surfaces has a long
history of lessons-learned that the majority of
OBAM aviation enthusiasts are unaware of.
| Quote: | | Experimental aviation is where many (if not most) advances in aviation occur. I say lets continue to advance aviation by expanding ideas and concepts - including new electro-whizzys. We don't have to stay with wing-warping just because it resulted from a prudent development program. Although .. maybe we need to consider it once again in today's environment. Hmmm ... any experimental aviation nuts out there willing to rework the wing warp idea? |
Not sure what this has to do with the conversation.
Indeed, the first time anything new is tried, the
investigator is an "amateur" at a particular
task. Experimental flight test USED to be the place
where new things were tried and developed before
loading those ideas to the production line. Reliability
is inversely proportional to parts count. Cost of
ownership goes up with parts count as does weight,
volume and sometimes - panel space. Flying an airplane
is not a complex or difficult task . . . "convenience"
just doesn't add performance or reduce cost.
Uncle Bert's design goals for Voyager was ALL performance
driven, convenience had little if any part in the task.
I've worked on biz jets where it was possible for a
flight to be totally button-pushed and knob-twisted
from wheels-up to touch-down. Now THAT's convenience
. . . but the airplane didn't get there any faster nor
did it carry more payload.
Airplane owners come in all flavors but I would hope
they are ALL cautious and strive for competence at
the implementation of their personal design goals.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
[quote][b]
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