[Vertebral injuries in aeronautical medicine with special reference to ejection in seat launching and descending by parachute].
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Acceleration↗
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Report of ejections in the Spanish Air Force, 1979-1995: an epidemiological and comparative study.
BACKGROUND: Ejection seats have saved many lives with more than 80% of pilots having survived an ejection. Nevertheless, ejection injuries are seen in all modern air forces. PURPOSE: An epidemiological study has been carried out on the 48 ejections made by the Spanish Air Force (SpAF) from 1979-1995. METHODS: From data facilitated by the Flight Safety Section of the SpAF Staff, by the Flight Safety Section of Squadrons, and from personal reports of pilots who survived ejections a form was created. Relationships between data concerning aeronautical parameters, pilot data and injuries have been found, and a comparative study was made between these results and data shown by air forces of other countries. RESULTS: Of 48 pilots who ejected, 7 died, 25 had severe injuries, 11 had minor injuries and 5 had no injuries. The reason for the ejections included 35 cases of technical failure, and 13 cases of human error. Of 43 surviving pilots, 23 were injured only at the egress phase, 1 1 only at landing, and 9 cases at both moments. None of the five pilots who ejected outside the ejection envelope were able to adopt the correct position. However, of 43 pilots who ejected within the envelope, 19 were seated in good position. Of 13 pilots who maintained control of the airplane, 9 were able to adopt a correct position. Of 35 pilots who effected the ejection without control of the aircraft, 25 were not able to achieve a correct seated position. CONCLUSIONS: The pilot position in the ejection seat, plane control, ejection inside the envelope, the pilot's training in how to assume the necessary body position at both egress and landing phases are determining factors for successful ejections.
Accidents, Aviation↗
Rocket plume burn hazard.
By use of miniature rocket engines, the burn hazard posed by exposure to ejection seat rocket plume flames was determined in the anaesthetized rat. A reference chart is provided for predicting equivalent effects in human skin based on extrapolation of earlier direct measurements of heat input for rat and human burns. The chart is intended to be used in conjunction with thermocouple temperature measurements of the plume environment for design and modification of escape seat system to avoid thermal injury on ejection from multiplace aircraft.
Accidents, Aviation↗
Case report: chronic sub-dural hematoma following high-speed ejection.
This paper reports a case of chronic sub-dural hematoma occurring in a pilot after a high-speed ejection that was within the survival envelope of the Mark 10 Martin Baker ejection seat. The events leading up to the ejection, his subsequent hospitalization for treatment of immediate injuries and late development of neurological signs, 6 weeks after the ejection, are presented. (A thorough search of literature has failed to reveal any previously published account of chronic sub-dural hematoma as a post-ejection complication.) His surgical treatment, recovery, and final assessment are discussed together with the possible causes of his sub-dural hematoma. Flight surgeons should take careful note of the events in this case. Sub-dural hematoma is frequently difficult to diagnose but it should not be discounted as a potential late complication from an ejection which is within the parameters of survivability and which yields, initially, only signs of relatively minor injury.
Accidents, Aviation↗
Aircrew ejections in the Republic of Bulgaria, 1953-93.
We reviewed the ejections of 60 pilots who ejected from 54 aircraft of Soviet production in the Republic of Bulgaria from 1953-93. The following factors were correlated with the degree of injury during ejection: the fliers' height, weight, and age; type of aircraft and ejection seat; altitude and speed of the aircraft at ejection; and the reason for ejection. The act of ejection can be a life-saving procedure when the aircraft gets into a non-recoverable situation, especially when carried out at an altitude above of 300 m, or at ground level. Survival rate of pilots in those cases is 95-100% respectively, compared to the general survival rate, which is 83%. Of the 60 ejectees, 10 (16.7%) were killed, 14 (23.3%) suffered major injuries, 17 (28.3%) suffered minor injuries, and 19 (31.7%) were uninjured.
Adult↗
The decision to eject: a receiver operating characteristic analysis.
BACKGROUND: Although the technology of ejection-seat systems is highly developed and automated, the decision about whether to eject still rests with the pilot. One factor thought to affect that decision is the height at which the decision must be made. For this reason the Royal New Zealand Air Force considered lowering its designated ejection decision height of 10,000 ft above ground level so that pilots had more time to make a correct decision. HYPOTHESIS: Lowering the ejection decision height will increase the accuracy of ejection decisions. METHODS: Thirty male Strike pilots each flew twenty simulated sorties. Half the sorties involved scenarios that required ejection and half did not. The pilots were divided into three equal groups which were randomly assigned to an ejection decision height of 10,000, 6,000, or 3,000 ft above ground level. After a sortie ended or was terminated by ejection, each pilot rated his confidence on a six-point scale that the scenario did or did not require ejection. RESULTS: Receiver operating characteristic analysis showed that the ejection decision height did not influence the accuracy of the decision to eject, but did affect the bias for ejecting. The bias in favor of ejecting increased as the height was lowered. Experienced pilots were more decisive in making their judgments than less experienced pilots. CONCLUSIONS: Lowering the ejection decision height did not affect the accuracy with which pilots could discriminate between flight scenarios that required ejection and ones that did not, but it did increase their bias to eject.
Aviation↗
Laser in situ keratomileusis flap stability during simulated aircraft ejection in a rabbit model.
PURPOSE: To determine the stability of the laser in situ keratomileusis (LASIK) flap in a rabbit model when subjected to vertical acceleration at nine times the force of gravity (+9 Gz) in an aircraft cockpit ejection simulator. METHODS: Thirty-six eyes from 25 New Zealand white rabbits underwent LASIK flap creation without laser photoablation. One month after surgery, the rabbits were sedated and harnessed in a cockpit ejection seat simulator used to train United States Air Force pilots. They then underwent a controlled rapid-sequence ejection at +9 Gz. Subsequently, the rabbits were euthanized and the corneas harvested for microscopic examination. Refractive measurements and corneal examination were made before LASIK flap creation and prior to and after the +9 Gz ejections. Determination of LASIK flap dislocation was based on clinical observation of flap slippage or a significant shift in pre-ejection to postejection cylinder axis. RESULTS: The average preoperative refraction of the rabbit eye was +1.83 D + 3.25 D x 086 degrees. The average change from pre-ejection to postejection was 0.04 D sphere, 0.02 D cylinder, 6.8 axis degrees, and 0.04 D spherical equivalent. The pre-ejection to postejection measurements were not statistically significantly different by a paired test. Laser in situ keratomileusis flap dislocation or ejection-induced corneal folds or striae were not clinically observed. Histologic examination revealed well-healed LASIK flaps but no reactive keratocytes at the central stromal-stromal interface. CONCLUSIONS: Healed LASIK flaps as created in this rabbit model without laser ablation are stable when subjected to a rapid vertical ejection at nine times the force of gravity.
Aerospace Medicine↗
[Mathematical modeling of the kinematics of a pilot's head while catapulting into an air stream].
The trajectories of head movements in the helmet and velocities of impact contact with the seat and anterior of the cockpit were calculated as applied to every stage of the catapulting process and mass-inertia parameters of helmets taken into account. Kinematic models were used to describe biomechanic parameters of the head-neck system. Special attention was given to the case of catapulting to the air flow. The effect upon the nod of aerodynamic forces acting on the human body and the catapult ejection seat at air flow velocities of 700-800 and 1300 km/hr was calculated.
Aerospace Medicine↗
Dynamic strength capabilities of small-stature females to eject and support added head weight.
BACKGROUND: Naval Air Warfare Center Aircraft Division investigated the abilities of small-stature females (< or = 120 lb) to fly under G-stress using the Dynamic Flight Simulator (DFS) and its tactical fight/attack cockpit, displays and controls. OBJECTIVES: Determine ability to exert NACES ejection seat actuation pull force under static, acceleration and simulated flight conditions; support up to 5 lb of added head weight (AHW) under catapult, arrestment, and aerial combat maneuver G-loads; and reach all controls. METHODS: Seven female subjects (six small and one medium stature) participated. The AHW task included three helmet weights, 3.5 lb (standard configuration), 4.25 lb and 5 lb and subjects were tasked to accurately read cockpit displays. Muscular exertion and fatigue (arm, shoulder, neck) assessment used electromyography (EMG). Limits in overall reach and throttle and stick movements were measured. RESULTS: Subjects successfully ejected using a two-hand grip under G-stress. Subjects read all displays supporting 5 lb under +6 Gz. Most small-stature subjects could not fully support their heads wearing 3.5 lb helmet during flat spin conditions. CONCLUSIONS: Within the scope of these tests, small-stature subjects demonstrated the strength to safely initiate ejection during severe physically-taxing dynamic conditions but had difficulty supporting AHW under -Gx stress. Human factors deficiencies were noted in the areas of torso harness fit, inertia reel placement relative to shoulder width, and the ability maintain a full range of stick motion.
Adult↗
John Paul Stapp and Deceleration Research Part II: Windblast and Deceleration Tests at Holloman Air Force Base.
After WW II, the development of ejection seats for escape from high speed, high altitude aircraft posed a number of new problems regarding human tolerance to linear deceleration, windblast and tumbling. The research conducted by Colonel John Stapp at Edwards AFB under Project MX-981 was limited by the capacity of the 2000 ft deceleration track, prompting a relocation of the research to make use of the 3500 ft track at Holloman AFB to address those problems. This paper reviews the factors that led up to this move and the tests conducted on the Holloman Track.
Journal Article↗
Evaluation of the disposable absorption containment trunk for female U-2 and TR-1 pilots.
Female U-2 and TR-1 pilots needed a urine collection device as part of their high flight pressure suit ensembles. The Disposable Absorption Containment Trunk (DACT) had been designed for short term use with the NASA Space Shuttle Program. This study evaluated the DACT for the extended and repetitive use required for integration into the U-2 and TR-1 aircraft. Six female subjects were tested wearing a custom-fit DACT and the 1030 full pressure suit ensemble with torso harness. They were strapped into the U-2 ejection seat with parachute and seat kit for 10 h and 45 min every 3 d for a total of 5 sessions. The DACT was evaluated for absorptive capability and comfort. Subjects were monitored for dermatitis, vaginitis, and urinary tract infections. The DACT reliably absorbed menstrual flow and urinary outputs to 950 cc. Higher urinary outputs resulted in minimal leakage. Dermatitis in the form of mild erythema and chafing was present, but cleared between sessions without medical intervention. Complaints concerning comfort were minor and limited to fit problems. One case of vaginitis developed. There were no cases of urinary tract infection. The DACT was found to be an acceptable method of urine collection for female U-2 and TR-1 pilots. Minor changes in design will enhance the comfort and performance of the DACT.
Adult↗
Massive retroperitoneal hemorrhage from an asymptomatic adrenal cortical adenoma. Report of a case.
A 52-year-old man was admitted to the General Surgical Service, with acute onset of left back and flank pain. Two weeks prior to admission he had been subjected to a 3G to 4G acceleration in an ejection seat training simulator. On the day of admission, he had performed a 100 yard swim in flight gear following a seven foot jump into water. He denied any injury during the above exercises or any other trauma. A falling hematocrit was demonstrated by serial determinations and a computerized tomography scan revealed a left retroperitoneal hematoma with normal bilateral renal function and no obvious renal injury. Continued hemorrhage resulted in laparotomy, which showed an 11 cm left adrenal tumor with massive hemorrhage into the retroperitoneum. Histologically the tumor was a benign non-functioning adrenal cortical adenoma.
Adenoma↗
Bone scintigraphy in the evaluation of ejection injuries.
The Royal Air Force (RAF) experience on local back injury with all ejection seats is that 50% have vertebral fractures on radiographic examination, with or without symptoms. These aviators are placed under the care of an orthopedic specialist and restricted from flying duties for 3 months or more. About half of the remainder demonstrate positive bone scans. Until recently, RAF policy was to treat these individuals the same as those with radiographically defined fractures. The author recommends this group of pilots be examined by orthopedic surgeons, and reviewed annually to assess long-term sequelae. Meanwhile, if asymptomatic, they are allowed to return to flying duties. The RAF recently incorporated most of these recommendations into a policy change.
Aerospace Medicine↗
A review of Army Air Corps helicopter accidents, 1971-1982.
A comprehensive review of helicopter accident data from ACC sources is presented for the period 1971-1982. Accident and fatality rates have declined from the high values quoted in earlier studies in the 1960's and are now similar to those of fixed wing aircraft equipped with ejection seats. This improvement is related to the replacement of older reciprocating engined helicopters by turbine powered units and parallel progress in helicopter design, aircraft servicing, and pilot training. AAC accident rates now compare extremely favourably with information from civilian sources, though fatality rates are similar. Pilot error remains the main cause of accidents (75%). Particular attention is paid to subsidiary aetiologies such as tail rotor strikes, disorientation, and ground accidents. Helicopter accidents involving fatalities on Operation Corporate are mentioned briefly. Methods whereby occupant protection and aircraft crashworthiness can be improved are covered and it is concluded that assisted escape, although an ideal solution, is by no means an urgent requirement for helicopters, in view of the dramatic reduction in accident and fatality rates.
Accidents, Aviation↗
Human error in the seventies--reviewed and projected through the eighties.
The USAF has had an impressive record of improvement in its accident experience during the past three decades. This has been reflected in markedly lower rates in accident experience, aircraft destroyed, and fatal accidents. As the historic experience line comes closer to the ultimate zero goal, improvement becomes more difficult. The trends during the 1970s suggest that a bottom, at least temporarily, was reached so that, unless additional effort is exerted, an actual increase rather than a continuing decline will occur. Experience does show that, regardless of future overall accident trends, the proportion of the accidents which result in fatalities will almost certainly increase. There is also a clear indication that, unless crewmen in ejection-seat-equipped aircraft improve their emergency perception and decision-making abilities, the proportion of successes in airborne escape may not increase but could well decline still further. Accidents will almost certainly maintain the trend of being associated with in-flight rather than takeoff or landing activities. One kind of flight mishap of particular concern remains that of USAF planes with civilian aircraft. On the basis of past experience, these kinds of accidents can continue to be anticipated. Their prevention represents a focal point of real concern. One feature of future mishaps which will become increasingly prominent will be the involvement of women crewmembers. Both a distressing and heartening feature of the review of mishaps is that even a cursory review indicates that most, if not all, are preventable by the use of well-known and well-established principles of accident prevention. Improvement in the selection, training, and use of people, and improvements in hardware, both in terms of reliability and man/machine compatibility, can all lead to increased efficiency and a continuation of the historic down trend in accident losses. This defines the direction for the eighties.
Accidents, Aviation↗
[Spinal and spinal cord injuries in aviation medicine].
The causes of vertebral lesions in the course of flying are listed. An account is given of the dynamic forces required to bring about vertebral fracture and their mechanism. Reference is made to the most common sites of vertebral injury in crashes, particularly in the case of helicopters, and during catapulted seat ejection. Lastly, sites of vertebral fracture in parachutists are discussed.
Accidents, Aviation↗
Injury risk for research subjects with spina bifida occulta in a repeated impact study: a case review.
Spina bifida occulta (SBO) occurs in 18-34% of the normal U.S. population. Recently, 16.5% of normal, asymptomatic male soldier volunteer candidates in a U.S. Army Aeromedical Research Laboratory ride motion study were excluded from the study because they had SBO at one vertebral level. Disqualifying this percentage of screened research subject candidates threatened the timely completion of the schedule-intense protocol. Although one study suggests that SBO at spinal level S1 has a higher incidence of posterior disc herniation, the preponderance of clinical literature reports that spina bifida occulta is not a medical problem. The impact literature indicates that lumbosacral vertebral bodies fracture at 7.14 kN in static compression and 20+ G during dynamic vertical impacts. In this paper, we examined the human data observed in ejection seat incidents, the rationale for excluding volunteers with single level SBO and the path of axial load transmission through the lumboscral spine. Based on the findings, we concluded that research volunteers with single level SBO are not at increased risk for injury and recommended inclusion of these volunteers in future studies involving repeated axial impacts due to ride motion.
Adolescent↗
Comparison of acceleration subjects to other populations: spinal anomaly distribution.
Two Armstrong Laboratory (AL) human volunteer subject panels (sustained and impact acceleration) at Wright Patterson AFB, OH, were compared to each other and to other samples of different populations in terms of spinal anomalies. These sample populations were obtained from the scientific literature: French, Norwegian, Netherlands, and U.S. pilots; U.S. Air Force (AF) and Navy subjects, and from representative "normal" civilian populations, and then compared using the proportion parameters for various spinal anomalies. There were only a few common parameters between the two panels and between each panel compared with the foreign military, human subjects, and "normal" population. However, there were two to six times as many similar spinal anomaly incidence rates between the AL panels and the U.S. pilot sample. It was reassuring that the AL subject panels used in AF acceleration research have more in common with AF pilots than other populations in regards to spinal anomalies, even though the pilot sample may not be representative of the true pilot population. Recommendations are to establish a common reference point in nomenclature and description of spinal anomalies (modeled after the French) and to start collecting spinal radiographs on all U.S. pilots. These radiographs would not be for screening but for establishing a database following the occupational pathology of flying. This data would also facilitate comparisons with research acceleration panels, as well as with foreign air forces. Informed decisions can then be made regarding screening criteria for the future as aircraft and ejection seat performance envelopes continue to expand.
Acceleration↗