Measurement of Accelerations Experienced by Rough Stock Riders

Measurement of Head Acceleration
and Angular Rate Experienced by
Aerobatic Pilots
Leigh Lewis, M.D.
Internal & Aerospace Medicine Resident
Richard Jennings, M.D., M.S.
Director Aerospace Medicine UTMB
This research was supported by a
grant provided by:
The National Space Biomedical
Research Institute (NSBRI)
Outline
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Introduction
Problem
Specific Aims
Background
Methods
Results
Discussion
Conclusion
Introduction
• Automotive industry
utilizes accelerometer
technology in impact testing
• Plastic-molded ear plugs
• In-ear accelerometers measure accelerations at
head-level
• Recent research in race car drivers, football
players, boxers, and rodeo riders
Introduction
• Aerobatic pilots exposed
to wide range of G’s
• Non-impact acceleration,
but can cause neuro
-vestibular symptoms
• G-meter only records Gz values
• +Gz’s: gray-out, black-out, and G-induced loss of
consciousness
• - Gz’s: head fullness, headache, vision changes,
decreased heart rate, arrhythmias, and red-out
Problem
• No tri-axial accelerations
previously published
• Actual forces experienced at
head-level during aerobatic
flight have never been
characterized
• Vertigo or gait abnormalities
may represent G-induced
vestibular dysfunction (GIVD)
or “the wobblies”
• Thought to be associated with
high - G’s
• Sxs may lead to safety of flight
or career-limiting effects
Specific Aims
• 1) Measure the magnitude of linear accelerations
and angular rates experienced at head-level by
aerobatic pilots
• 2) Compare data obtained at head-level to that
of the plane
Background
• Muller: first case report of G-induced vestibular
dysfunction (GIVD) or “the wobblies”
• 41 year old aerobatic pilot
• Reported spinning sensation with nausea after -7 G
maneuver
• Pilot had unsteady gait and fine horizontal nystagmus
upon exiting the airplane
• Diagnosed with Benign Paroxysmal Positional Vertigo
(BPPV) and treated using the Epley maneuver
• Against medical advice, the pilot continued to fly and
completed the aerobatic competition without recurrence
Muller TU. G-induced vestibular dysfunction (‘the wobblies’) among aerobatic pilots: a case report and review.
Ear Nose Throat J. 2002; 81:269-72.
Background
• Authors proposed
GIVD similar to
post-traumatic BPPV
• Rather than a blunt force, G forces could
cause otoconia displacement
• May be related to head movements during
G exposure
• Complex area of study warrants further
investigation
Jia H, Cui G, Xie S, Tian D, Bi H, Guo S. Vestibular Function in Military Pilots Before and After 10 s at +9 Gz on a
Centrifuge. Aviat Space Environ Med. 2009; 80:20-3.
Background
• Muller: survey during the World Aerobatics
Championships in 1998
▫ “More than 75% of team members from the U.S.,
Britain, Australia, Russia, Switzerland, Hungary, and
Slovakia had experienced at least one episode of
GIVD”
▫ Only French team stated GIVD was infrequent
• Williams et al conducted a survey among a wide range of
civilian aerobatic pilots in 1996
▫ 12.7% of respondents (mean peak -8 Gz) reported
persistent vertigo after aerobatic flight with exposure
to negative G’s
• Doesn’t include pilots with vestibular problems early in
their careers/those involved in fatal mishaps
Muller TU. G-induced vestibular dysfunction (‘the wobblies’) among aerobatic pilots: a case report and review.
Ear Nose Throat J. 2002; 81:269-72.
Williams RS, Werchan PM, Fischer JR, Bauer DH. Adverse effects of Gz in civilian aerobatic pilots [abstract].
Aviat Space Environ Med. 1998; 69:201.
Methods
Diversified Technical Systems (DTS) designed and built tri-axial
accelerometers, angular rate sensors, data recorders, and software
Methods
Methods
Results
• Complete readings from both plane and
pilot for a 10-minute practice run were
successfully collected from five subjects
• Max pilot and plane linear accelerations
and angular velocities highly correlated
(correlation coefficients: 0.77, 0.91, 0.91,
0.90, 0.88)
Axis
Pilot (95% CI)
Plane (95% CI)
P-value
Positive linear x (G)
4.76 (3.2 to 6.3)
8.24 (3.8 to 12.7)
0.100
Negative linear x (G)
-6.90 (-8.1 to -5.7)
-7.86 (-13.1 to -2.7)
0.635
Positive linear y (G)
2.28 (1.9 to 2.6)
10.44 (2.0 to 18.9)
0.053
Negative linear y (G)
-4.80 (-11.1 to 1.45)
-9.82 (-20.3 to 0.6)
0.316
Positive linear z (G)
5.30 (3.4 to 7.2)
13.96 (1.6 to 26.4)
0.129
Negative linear z (G)
-5.88 (-9.9 to -1.9)
-19.4 (-39.5 to 0.7)
0.149
Positive angular x (deg/s)
277.42 (196.6 to 358.2)
460.66 (305.1 to 616.2)
0.013
Negative angular x (deg/s)
-384.66 (-404.6 to -364.7)
-425.64 (-649.3 to -201.9)
0.653
Positive angular y (deg/s)
255.98 (172.7 to 339.2)
190.46 (121.0 to259.9)
0.154
Negative angular y (deg/s)
-282.64 (-335.4 to -229.8)
-185.68 (-281.1 to -90.3)
0.058
Positive angular z (deg/s)
294.22 (184.0 to 404.4)
154.1 (111.4 to 196.8)
0.014
Negative angular z (deg/s)
-382.8 (-473.1 to -292.5)
-137.68 (-220.1 to -55.6)
0.004
Comparison of mean linear acceleration and angular velocity for pilot v plane
Example Plot: Resultant accelerations of pilot v plane for a test run.
Results
• Pilot accelerometer Gz’s highly correlated
to G-meter: 0.79 for +Gz and 0.76 for –Gz
• Plane accelerometer Gz’s correlated with
removal of test run 1: 0.70 for +Gz and
0.99 for -Gz
• No reported GIVD from 10 to -6 G’s as
recorded by each aircraft’s G-meter
Discussion
• First Aim
▫ Data successfully collected during five practice
runs at the 2009 US National Aerobatic
Championships
• Second aim
▫ Max and min parameter comparison
▫ Paired t-tests of mean value for each parameter
▫ G-meter comparison
 Test run 1 plane accelerometer recorded very
extreme values
 May have been valid, but could have been fleeting
 Increased sample size to see if values are plausible
Discussion
• No similar studies in aerobatic
pilots
• Dr. Watkins: peak resultant linear
acceleration for the bull rider was
26 G’s/bareback rider was 46 G’s
• Dr. Mathers: bareback riders
exposed to twice the level of
accelerations as bull riders
• Max G’s were 27.6, 17.5, and 24.9
while max angular rates were
2109.7, 2864.7, and 2228.7 deg/s
in the x, y, and z axis respectively
• Rough stock riders are exposed to
higher positive G’s and angular
velocities several orders of
magnitude higher than those of
the aerobatic pilots
• Aerobatic pilots represent unique
population to study negative G’s
Discussion: Limitations
• Small sample size
• Only males
• Subjects do not include air show performers who may
pull varying amounts of G’s
• Confidence intervals demonstrated wide ranges and
several included zero
• Test run one plane accelerometer values
• Flat surface not always available for airframe
accelerometer
• Equipment settings
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Less sampling
Only values for specified time collected
Angular acceleration
Could sync with video
• No comparison among pilots
Future Applications
• Experimental sensors are capable of measuring a
large array of forces that have not been routinely
captured from G-meter data
• Further data collection may capture values
associated with neurovestibular effects such as
GIVD
• Once values for neurovestibular effects are
quantified, clinical models can be devised to predict
adverse effects for certain non-impact head-level
accelerations and angular rates
• Mitigation strategies can then be developed and
employed to prevent such occurrences
Conclusion
• Head-level data can be
successfully collected and
correlated using tri-axial
accelerometers and angular
rate sensors
• Aerobatic pilots experience a
large range of linear
accelerations, which appear to
be well correlated to their
aircraft.
• Future work in this field may
involve clinical modeling of Geffects based on head-level
accelerations and angular
rates.
Acknowledgements
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NSBRI
James Vanderploeg, M.D., M.P.H
Jonathan Clark, M.D., M.P.H.
Debbie Rihn-Harvey
Sharmila Watkins, M.D., M.P.H.
Charles Mathers, M.D., M.P.H.
Kathleen Samsey, M. D.
Pat Puzzuto
Sherry Puzzuto
Daniel Freeman, Ph. D.
Laura Rudkin, Ph.D.
Tonya Groh, Diane Ellison,
Yvette Schultz
• The volunteer pilots who
participated
References
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