Proposal
for the establishment of a database for civilian and military aircraft
accident/incident due to spatial disorientation.
1
June 1994
Kaz
Shimada
Aerospace Medicine
Wright
State University
Introduction
Spatial
disorientation (including those terms such as Ôpilot vertigoÕ, spatial
misorientation) has been attributed for a cause of aircraft accident. It is frequently quoted in a crash
investigation of high-performance military aircrafts [Gardetto]. But it could be a cause in a accident
involving a large civilian jetliner.
In fact, there are some of the reports suggesting accidents happened due
to spacial disorientation [NTSB].
There
have been not much attention paid on spatial disorientation in FAR Part 121/135
airline/commuter mishaps.
Especially in large jets incidents, factors from spatial disorientation
were not clearly stated in accident reports [Veronneau].
It
is not easy to extract spatial disorientation issues from present accident
reports, but efforts are being commenced by Federal Aviation
Administration[Veronneau], US Navy[Patterson], US Air Force[Gardetto], and
Army[Durnford]. To join these
efforts and make a database available to researchers will be valuable for the
further safety of air travel.
Today, we have to begin with constructing such database of civilian
airliner accident cases.
Background
Spatial disorientation
To
an individual inside an aircraft, vestibular information can be misleading
because the body no longer has a mixed reference with which to orient against,
as the individual moves when the aircraft moves. Further, steady aircraft motion, or an accelerating or
decelerating aircraft, can produce vestibular sensations that are at odds with
the reality of the bodyÕs orientation.
Generally, visual information in an aircraft can counter misleading
vestibular information since either the horizon or aircraft instruments can
tell the individual the aircraftÕs and thus the individualÕs orientation
relative to the earth. However,
when such visual information is lacking or is not perceived, the individual can
be misled by incorrect vestibular information. That individual is spatially disoriented, or is perceiving
an orientation in space that is incorrect. A spatially disoriented pilot can believe that a straight
and level aircraft is in a turn, or is climbing or descending [NTSB].
IFR/IMC flying
Spatial
disorientation is likely to occur when external visual cues are lost due to
clouds (Instrument Meteological Condition, IMC) or at night. Pilots are trained to rely on aircraft
instruments which directly or indirectly indicates aircraftÕ attitude. When they are flying under IMC by
instrument flight method (Instrument Flight Rule, IFR), they are unable to rely
on outside horizon when they lose spatial orientation.
Autopilot
Use
of autopilot, not only to help the pilot recover from disorientation, but also
to help the pilot recover from disorientation, but also to help prevent the
disorientation in the first place, has a considerable potential for saving
lives [Gillingham].
Autopilots
are always used in large aircrafts.
When it is disengaged forcedly by a turbulence, such as wake turbulence,
pilots will have a hard time in transition from autopilot to his/her own
instrument attitude orientation.
This could lead to a disorientation incident.
Flight data recorder
Commuter
airliners are not required to install a flight data recorder (FDR). This makes post-accident analysis
difficult. For example,Beechcraft
1900C N811BE, operated by a commuter and crashed on 28 December 1991, was not
equipped with a FDR [NTSB]. None
is required by FAR135. Its flight
was analyzed with cockpit voice recording, air traffic control (ATC) communication
recording, and ATC radar data.
Probable cause of the crash was that both instructor and trainee was
disoriented by partial panel training low at night.
It
will be easier and less expensive to install a FDR onto a commuter aircraft
with the use of GPS and connecting it to digitized flight control. Then, number of cases of disorientation
of commuters and general aviation aircraft might increase.
Current literature
Because
of absence of FDR in general aviation and commuter airline aircraft, and a less
interest in disorientation factor in airline aircraft crash investigation, Some
of the military accident case analysis are available [Gardetto] but not
published as specialized regarding spatial disorientation. Thus, spatial disorientation study in
aircraft accidents is mostly observational and descriptive.
Objective
To
gather and organize civilian and military aircraft accident data and establish
a database for spatial disorientation accident analysis. Conduct cross-sectional study for
spatial disorientation, and do case-control study if possible, then prepare for
future historical cohort study.
Study design
This is a retrospective study.
1) Extract
civilian spatial disorientation cases from NTSB reports. Search for keywords related to spatial
disorientation in FAA database, and look up probable cases (might be several
hundred), and assess the cause of the case.
2) Coordinate
with US Navy, US Air Force, and US Army and collect their cases of spatial
disorientation. Establish a
standard report format if possible.
It is expected that about a thousand possible spatial disorientation
cases and forty to fifty definite cases will be collected.
3) Assess
and standardize the quality of case description. Basically all cases of probable cases will be included. Exclusion of cases will be done
concurrently with cross-sectional analysis using database. The state of visual cues, the attitude
and motion of the aircraft when pilot commence correction, etc. will be
included.
4) Organize
the case description into computer database.
5) Conduct
a cross-sectional study.
Categorize described cases into VMC/IMC, single pilot/two pilot, type of
aircraft, type of autopilot, the attitude/motion of aircraft when pilots
commence control input, human factors such as previous wok hours, sleep,
experience of pilots etc. Possible
experimental hypotheses are such as:
\There is a threshold for current actual IFR time and rate of
accident.
\There is a significant number of reversal reading of attitude
indicator.
\There is a difference in rate of accident in different types of
autopilot.
etc. Detail of an
example study is to follow.
An example of a possible analysis after the establishment
of this database
Because
the status of the knowledge regarding spatial disorientation in aircraft
accedent is that there is no established database, numbers in this exapmle are
all assumed (indicated with *).
Null hypothesis: No
difference in outcome (aircraft damage/personal injury) whether pilot began to
input corrections to control, past 30 degrees* of roll or within 30 degrees* of
roll.
Experimental hypothesis: Significant
outcome difference if pilot began correction before or after 30 degrees* of
roll.
Subjects:
Inclusion
criteria: all
pilots in a incident suspected of disorientation
all
category of aircraft in database
Exlusion
criteria: no
evidence of control input to the aircraft
Study duration: all
cases in database
Outcome criteria: 1)
attained unusual attitude (either over 45 degrees* of roll, 30 degrees*
of pitch up, 45 degrees* of pitch down, or stall)
2)
excess G of over 67 %* of design limit
3)
aircraft damage
4)
personal injury including total crash
Data analysis: Assign
a coefficient of 0.1, 0.3, 0.7, and 1.0 to each outcome criteria* (accumulative
to a single case; 0 - 2.1) and make a score for a case (two cases if two pilots
tried a control); compare the over-30 deg group to within-30 deg group for the
difference in this score by a t-test.
Expect to have a necessary n =8* in each group, approximated by z test; a = 0.2, b =
0.5, m1 - m2 = 0.6, d = 0.6* (2[(1.28+0.7)0.6/0.4]**2). If this does not do, a comparison for
relative risk for personal injury will be compared.
References
1) DeHart
Rl, Beers KN. Arcraft accidents, survival, and rescue. In: DeHart RL ed.
Fundamentals of aerospace medicine. Philadelphia, Lea & Febiger, 1985:
862 - 887.
2) Durnford
SJ, Rosado NR, Crowley JS. Spatial disorientation - a review of U.S. Army
accidents. Aviat Space Environ Med; 65, 1994: 442.
3) Gardetto
P. Fighter/bomber aircraft impacted ground during a formation rejoin
loss of s/a, spacial misorientation.
Handout for WSU CMH721, 1994.
4) Gillingham
KK, Wolfe JW. Spatial orientation in flight. In: DeHart RL ed. Fundamentals
of aerospace medicine. Philadelphia, Lea & Febiger, 1985:
299 - 381.
5) National
Transportation Safety Board. Aircraft accident/incident summary report
- loss of control business express, Inc., Beechcraft 1900C N811BE near Block Island, Rhode Island December 28,
1991. PB93-910405, 1993.
6) Patterson
FR, Cacioppo AJ, Hinman GE, Nalepka JP. Aviation spatial orientation
in relationship to head position and attitude interpretation. Aviat
Space Environ Med; 65, 1994: 442.
7) Veronneau
S. personal communication.
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