 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
Mark Sletten
Joined: 10 Jan 2006
Posts: 43
Location: St. Jacob, IL (Near St. Louis, MO)
|
 Posted: Sat Jun 24, 2006 7:42 am Post subject: Disorientation |
 |
|
GMCJetPilot said:
You CAN'T buy a new airliner or business plane w/ mechanical
gyros anymore. My guess is GA planes also will stop coming
w/ mech gyros and yes T&B's. Already all top end GA planes
have EFIS and no T&B. Cirrus / Lancair all EFIS and no T&B.
These top of line EIFS GA planes do come with backup
mechanical airspeed, altimeter and attitude indicator (AI)
but no T&B.
All true, and one of the prime reasons the FAA has recently started a new
training initiative (FAA/Industry Training Standard [FITS] for
Technologically Advanced Aircraft [TAA]) aimed at preparing general aviation
pilots for the rigors of flying with all the new technology. Many flight
schools offer this training; some refer to it as "glass panel transition"
training. Aircraft manufacturers offering glass panel technology in their
aircraft offer (strongly suggest) FITS even for their VFR pilot customers.
Note that this training is in addition to that required to attain your
private pilot certificate.
GMCJetPilot said:
Also the Regs allow you to omit a rate of turn indicator
altogether if you have AI's at each pilot station and one
back-up AI with independent power source. So you don't
see T&B's on Cirrus, Lancair or Jets but you will see two
or three AI's.
Your arguments about airliners (and other aircraft) that may dispense with
rate of turn instruments by installing attitude instruments at both pilot
stations is a good one -- as long as a trained, competent pilot occupies the
other seat. I'm not telling you anything new when I point out that two-pilot
operations is one of the primary factors behind the phenomenal safety record
of the airline industry. Using panel-design standards optimized for
two-pilot ops in a single-pilot aircraft might not yield the same result.
If your significant other has ever shared intimate knowledge of their past
significant others you may have thought to yourself "too much information."
I can easily see the TMI beast rearing it's ugly head in the cockpit
equipped not only with an EFIS (which will, like it or not, become your
PRIMARY attitude instrument) and artificial horizons all over the place.
You'd better carry several of those instrument suction cup thingies to cover
the ones that make you feel uncomfortable...
As to the relative value of the rate of turn instrument, I'd like to help
clarify what I believe to be Old Bob's point. If I'm speaking out of turn
here Old Bob, please feel free to slap me back to my place, but I believe
the point you are trying to make is "stop the turn." Yeah, I think I read
that!
In my youth I had occasion to attend USAF Physiological Training (otherwise
known as the Altitude Chamber). Aside from discussing the effects of high
altitude on human physiology, we were given the opportunity for a ride in a
device, the Vertigon, that demonstrates the effects of a discontinuity in
the motion perceived by your brain and the motion you are actually
experiencing, otherwise knows as vertigo. The individual is placed inside
the Vertigon, which is a mock up cockpit with no external visual cues. Once
inside and "flying" on instruments, ATC directs a climbing right turn, at
which point the Vertigon begins a slow spin around the vertical axis -- to
the occupant it feels just like a climbing right turn!
Contrary to popular misunderstanding, your vestibular system (that's your
body's seat-of-the-pants motion detection system) does not sense motion or
movement, it senses acceleration through the displacement of small hairs
disturbed by fluid in a tube in your ear. As your head is moved, the fluid
in the tube tries to remain stationary (a body at rest tends to remain at
rest...). The tube, attached to your head, moves "around" the stationary
fluid, and the sensing hairs are "bent" by the stationary fluid. The faster
the movement the greater the bending of the hairs, which is interpreted by
your brain as ever more violent movement, but is actually acceleration. If
you continue the movement, eventually the friction between the tube/sensing
hairs and the fluid will cause the fluid to accelerate to the same speed as
the movement -- your brain interprets this as continuing movement. If you
suddenly stop the movement, the fluid, due to it's momentum, continues to
move displacing the hairs in the opposite direction and, voila', VERTIGO!
(For a really good demonstration of this, get a friend [you trust] to spot
you while you spin around on your feet for about a minute or so with your
eyes closed in the back yard. If you suddenly stop spinning [keep your eyes
closed] I can almost guarantee you will have great difficulty remaining on
your feet -- that's why you want to do it in your back yard so if/when you
fall down and go boom you don't hurt yourself or the furniture.) Your brain
can "update" your vestibular inputs with visual stimuli. This is how figure
skaters are able to stand up after those violent spins; they've TRAINED
their brain to override vestibular sensation with visual sensation. And
that's how pilots are able to control their aircraft using only instruments.
But if a motion is allowed to continue long enough, and the pilot is
unpracticed in dealing with the resulting conflicting vestibular/visual data
presented, disaster...
Back to Physiological Training. The unsuspecting occupant has been spinning
slowly in the Vertigon (it doesn't take much, maybe 10 RPM) for some time
when he/she is asked to change the squawk -- the control panel for which
happens to be between the pilot's legs. The movement of tilting the head
forward from vertical to look down between your legs wreaks all kinds of
havoc with the vestibular system, and is enough to create an almost
overwhelming feeling of vertigo. Spectators standing around the Vertigon can
usually tell exactly when vertigo has occurred from the sometimes violent
noises made by the victim's flailing limbs as he/she tries desperately to
keep from falling out of his/her seat. It's truly a remarkable experience, a
sickening-frightening-disorienting feeling which is almost impossible to
describe with words. So what's my point?
Well, it's the same point Old Bob has been trying to make. Airplanes don't
spin around the lateral or longitudinal axis, they spin around the vertical
axis. If an un-commanded turn develops in IMC and is allowed to continue,
eventually the fluid in the tubes of your vestibular system will accelerate
to the same speed as the spin about the vertical axis. As you now know, when
you try to stop the motion, you WILL experience vertigo -- the more violent
the spin, the more violent the vertigo. Obviously, this greatly compounds
the pilot's task of recovery. What's the best way to avoid this? STOP THE
TURN IMMEDIATELY!
What Bob has been trying to impress on everyone is that controlling the turn
makes all other aircraft control tasks possible. If you loose control of the
vertical axis then your chances of VERTIGO go up exponentially. The T&B/TC
instrument is designed for one purpose, controlling the turn. Controlling an
aircraft solely by means of instruments is tricky enough without having also
to contend with vertigo. The best method of avoiding vertigo is to stop the
turn.
Next time you IFR pilots (VFR pilots might consider bringing your CFII along
for this one) are flying about boring holes in the air with nothing better
to do try this: slow and trim the aircraft to best-glide speed, close the
throttle, take your hands off the control yoke (put them in your lap), and
use the rudder to keep the ball & needle centered if you have a T&B, or keep
the ball centered and the small aircraft level if you have a TC. You will
now be in a 1000' - 1200' foot/min descent with the wings level at a
relatively slow airspeed. In fact, if you experiment you'll find you can
start/stop shallow (standard-rate) turns in this configuration quite easily
using only the rudder. By adding throttle you can slow/stop the descent, and
now you're safely flying the aircraft with only the rudder and throttle, by
reference to only the rate of turn instrument and the altimeter. The T&B/TC
is the only instrument you can do this with easily -- it's almost a
no-brainer. And it's all possible by CONTROLLING THE TURN!
DISCLAIMER: The last-ditch maneuver described above should only be used
under the hood while training with a competent CFII or in the case of
EMERGENCY. If you find yourself in IMC accidentally with no clear idea which
way to turn to get back out you might use this maneuver to get yourself
down. The intent is that you pop out the bottom of the cloud with enough
altitude to continue flying and find a good spot to put it down safely, but
if you hit level ground in this attitude you'll probably survive unless you
fly directly into an obstacle. The VFR pilot should NOT PLAN to use this
maneuver as a method to descend through an overcast. If you find yourself on
top of an overcast you should turn around and fly back to IMC IMMEDIATELY.
You definitely don't want to attempt this maneuver for the first time in
actual IMC -- PRACTICE WITH YOUR INSTRUCTOR!
Mark Sletten
Legacy FG N828LM
http://www.legecyfgbuilder.com
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
_________________
Mark Sletten
Legacy FG N828LM
http://www.legacyfgbuilder.com |
|
| Back to top |
|
 |
BobsV35B(at)aol.com
Guest
|
| Posted: Sat Jun 24, 2006 8:52 am Post subject: Disorientation |
|
|
In a message dated 6/24/2006 10:48:15 A.M. Central Standard Time, marknlisa(at)hometel.com writes:
| Quote: | As to the relative value of the rate of turn instrument, I'd like to help
clarify what I believe to be Old Bob's point. If I'm speaking out of turn
here Old Bob, please feel free to slap me back to my place, but I believe
the point you are trying to make is "stop the turn." Yeah, I think I read
that!
|
Good Morning Mark,
I only wish I were educated and eloquent enough to state it as you have so graciously and effectively done!
Thank you very much!!
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Air Park LL22
Downers Grove, IL 60516
630 985-8503
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
