曝光台 注意防骗
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controls,” I assumed the role of student and expected/
relied on the other CFI to assume all responsibility...
I feel, that when two CFIs are flying together the
responsibilities HAVE to be spelled out so that there
are no assumptions, second guessing, missed items/
procedures and missed traffic.
It is truly scary when two CFIs fly together.
Wheel
spacer
same direction and was now
much closer. After another
brief moment, we realized that what we were looking at was
the landing lights of two separate aircraft approaching from
the west and that we were experiencing a visual illusion. It
was not until the aircraft finally got close enough to see the
position lights that we were able to distinguish one aircraft
from the other…
The reporter noted that contributors to the event were a
very dark night with no moonlight, and the aircraft’s
proximity to the ocean with its lack of surface lights and
features. Awareness of the flight conditions conducive to the
parallax effect can help keep pilots from falling victim to
this illusion.
A Monthly Safety Bulletin
from
The Office of the NASA
Aviation Safety Reporting
System,
P.O. Box 189,
Moffett Field, CA
94035-0189
http://olias.arc.nasa.gov/asrs
Number 246 December 1999
ASRS Recently Issued Alerts On…
LR-25 dive attributed to autopilot malfunction
DME outage in a Central American circling approach
B-737 uncommanded roll during ILS coupled approach
Password protection for Terminal Doppler radar systems
B-727 loss of engine power after fuel crossfeed termination
October 1999 Report Intake
Air Carrier / Air Taxi Pilots 1912
General Aviation Pilots 675
Controllers 69
Cabin/Mechanics/Military/Other 100
TOTAL 2756
The Parallax Effect
The “parallax effect” describes a type of visual illusion
in which the position of an object in 3-dimensional space
appears to change, due to a shift in the position of the
observer. The parallax effect can make distant fixed objects,
such as a planet or star, appear to be close and in motion.
The twinkling planet Venus is a well-known example in
aviation. Tower controllers have often cleared Venus to land,
while pilots have mistaken the planet for nearby aircraft
position lights.
The parallax effect is especially apt to occur during night
operations when there may be few, or no, visible references to
the horizon as an aircraft moves through space. Several
ASRS reports illustrate, beginning with a First Officer’s
account of a nighttime evasive maneuver that startled crew
and passengers:
I observed what I believed to be an imminent traffic
conflict. I manually overrode the autopilot and started an
immediate left turn. The perceived conflict was a result of
slight parallax of green and red wingtip lights of another
aircraft. A bright white star also appeared as one of the
running lights on the perceived conflict. The maneuver was a
gut reaction on my part, as I perceived the aircraft to be within
a few thousand feet from us. Passengers and flight attendants
who were not seated with their belts fastened were upended in
the cabin. One passenger received an abrasion to a knee and
one complained of a neck injury… After landing…[no
passengers] required medical attention… The aircraft was
inspected for overstress and no discrepancies were found.
A conservative approach, followed by the First Officer in this
instance, is to avoid the perceived hazard first, and verify the
nature of the hazard afterwards. Although this report didn’t
mention crew fatigue as a factor, fatigue is known to be
associated with susceptibility to the parallax illusion. U.S. Air
Force research has shown that a few minutes of breathing
100% oxygen will help to refocus pilots’ thinking–and
eyesight.
When To Their Wondering Eyes
Should Appear…
The parallax effect also can be experienced by several
observers at the same time, as reported by a general aviation
pilot who described a night flight with companions:
There were 3 of us in the cockpit, including 1 non-pilot.
We were heading northbound over the peninsula… All 3 of us
looked off to the 9 o’clock position and saw 2 landing lights
which appeared to be a single large aircraft approaching at a
very rapid rate… We banked to the right and pulled the
throttle to idle in an attempt to avoid what appeared to be an
imminent collision course. We then returned to level flight to
see that the perceived aircraft was still approaching from the
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