the 'aviation flight-reconfiguration' thing

kenneth Collins kpaulc at earthlink.net
Thu Feb 3 06:11:52 EST 2000


kenneth Collins wrote:

>[...]
 
> the MD-80 plane crash yesterday. the stabilizer problem is analogous to
> the nervous system 'lesion'. the pilots tried desperately to correct for
> the malfunction induced by the stabilizer failure, but because the
> failure of the stabilizer =separated= the stabilizer's functionality
> from the rest of the plane's controlable dynamics, the efforts of the
> pilots 'only' led to the deterioration of the functionality of the
> remaining control systems.
> 
> [an asside TO THE AVIATION AUTHORITIES: i've been analyzing plane crash
> dynamics for years, and have converged upon a 'core' set of things that
> might be of some use with respect to in-flight failure. this analysis
> focusses upon the alterations of flight configurations that 'surround'
> the instances of failure (such as this stabilizer failure). the
> underpinning rationale derives in the fact that it's relatively-obvious
> that in-flight reconfiguration, probably most-significantly power-down,
> as was apparently the case with this MD-80 yesterday, is a
> failure-precipitation factor. so, it =might= be possible, in some
> instances of in-flight failure, to 'reverse' the failure by reversing
> the in-flight reconfiguration. if the failure was precipitated by
> power-down, then power-up. of course, if there's a mechanical failure
> that 'locks-up' control mechanisms, it can be the case that reversing
> the failure-precipitating flight reconfiguration will be to no avail.
> but since these events are so catostrophic, why not explore the
> possibility, which is sort of like 'kicking a fender', while one's
> riding one's bike, to get the fender to stop rubbing on the tire. of
> course, reversing a power-down leaves the plane powered-up, which
> creates landing problems. these could be addressed via a carrier-type
> arresting apparatus that replaces the cable and hook with a net that's
> activated during landing emergencies. this setup would allow planes to
> touch-down at full-power, maximizing the functionality of control
> systems that remain effective. (before such safety apparatus could be
> installed, if reversing the failure-precipitating dynamics works, it
> would, at least, allow pilots to fly and 'ditch' closer to rescue.) i
> =understand= that this discussion, itself, has a lot of possible
> points-of-failure, but trying anything is better than 'abandoning' folks
> in the air, no? so why not, at least, explore the possibility of doing
> the 'reverse' thing? if it works, train pilots to attempt it when all
> else fails. sorry about having do do this, here. it's a long-shot, but
> it is a possibility, so i had to put it 'out-there' so that Engineers,
> and other folks responsible for flight safety, can consider it, explore,
> implement/reject it.]

of course, by 'full-power landing', i meant =until= the point of contact
with the ground. then, do everything possible to decrease the plane's
inertia. the whole idea of this, in and of itself, highly-undesireable
condition is to maintain some semblance of 'stable' in-flight trim after
flight-control 'failure'. (i understand that commercial aircraft are not
designed to handle the stress of such landings. but there's runway foam,
and the possibility of the proposed arresting apparatus, =iff= the
'disabled' aircraft can maintain sufficient flight trim to make it to a
landing site.

the control-surface failures are more like a consequence of an
overly-forceful, or overly-rapid in-flight system reconfiguration, which
is more like instances in which a bicycle's too-loose chain falls off
it's sprockets when one rides through a pot hole.

it's a bit 'alarming' to see it, but if in-flight reconfiguration is
done in less-'violent' ways, that would decrease the possibility of a
weakened control element's failure.

one routinely experiences the correlates of such in-flight
reconfigurations with respect to take-off's, take-off/level-flight
transitions, level-flight/landing transitions, and landings. there must
be some routinely-invoked rationale for such rapid flight-control
reconfigurations (perhaps less-rapid transitions are susceptible to
'instability'?), and that rationale would have to be weighed against the
opposing rationale of routinely minimizing stress on aircraft components
through more-gradual in-flight control reconfigurations.

what i'm talking about is the in-flight equivalent of riding one's
bicycle through a pot hole =gently= so that it's too-loose chain will
not be jarred into a disconnected-from-the-sprocket configuration.

in the in-flight circumstance, for the 'reversal' of the precipitating
conditions view that i wrote of earlier (quoted above) to be effective,
the pilots would have to have a keen sense for their aircrafts'
control-surface feedback, and 'reverse' the reconfiguration dynamics
=quickly= if it's to be successful.

i don't know whether such feed-back 'time' is, in fact, available. in
the case of a stabilizer, for instance, it's a long way from it to the
cockpit. feedback devices could be engineered into new aircraft designs
(at a cost of the added weight and flight-system complexity).

that's why, upon arising this morning, the strategy of =gentle=
control-surface reconfigurations, routinely applied, seems to be a
better overall strategy.

gentle transitions would also significantly increase the comfort
inherent in passengers' flight experiences, even as it minimized
in-flight wear-and-tear on the aircraft.

so, if, over the life times of commercial aircraft, all such transitions
were done more-gradually (less-forcefully), that would also tend to
lengthen the life-'times' of the control elements that are routinely
reconfigured.

which, all things considered, seems extremely-desirable, because control
components' receiving less mechanical stress last longer.

which reminds me of the rationale with which Jackie Stewart raced. he
won a =lot= of races, with his mind set on preserving the structural
integrity of his vehicle through the minimization of routine
acceleration and braking, etc., operations, and by driving a 'smooth'
line.

anyway, i wanted to address this stuff because there are obviously some
easy adjustments that, if applied, can make flying safer for all.

seeing such, there's Obligation, which i've fulfilled in these msgs.

ken (k. p. collins)

>[...]




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