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From page 61... ... 61 3 Crashworthiness and Other Safety Considerations With the exception of regulations governing school bus passenger transportation and crash protection,1 the federal government has not established safety standards that apply to wheelchair securement systems or wheelchairs used as seats in surface transportation vehicles or airplanes.2 Nevertheless, wheelchairs and securement systems that are designed and constructed according to voluntary industry standards intended to ensure safer transportation for people who must use their personal wheelchairs as seats in motor vehicles are currently in use. As explained in Chapter 2, the standards are issued by the Rehabilitation Engineering and Assistive Technology Society of North America (RESNA) Read the entire page →
From page 62... ... 62 WHEELCHAIR SECUREMENT CONCEPT FOR AIRLINE TRAVEL systems (WTORS) and for wheelchairs that may be used as seats in motor vehicles.3 Although it was created in 1979 and has been issuing wheelchair transportation safety standards since the 1990s, RESNA has not established standards for the safe securement and use of wheelchairs in passenger airplanes. Read the entire page →
From page 63... ... CRASHWORTHINESS AND OTHER SAFETY CONSIDERATIONS 63 be needed for a wheelchair to be positioned and secured in Chapter 4 and the summary assessment of the technical issues, challenges, and uncertainties associated with a wheelchair securement system concept in Chapter 5. FAA CABIN INTERIOR CRASHWORTHINESS REQUIREMENTS FAA's aviation safety regulations in 14 CFR are organized into more than 40 parts, each addressing a specific activity, such as the flight rules governing aircraft operation and the certification of pilots, aircraft, and aircraft technicians. Read the entire page →
From page 64... ... 64 WHEELCHAIR SECUREMENT CONCEPT FOR AIRLINE TRAVEL BOX 3-1 Crashworthiness Requirements for Cabin Inferiors of Transport Category Airplanes: Major Sections. Title 14 Part 25 of the Code of Federal Regulations (14 CFR 25) Read the entire page →
From page 65... ... CRASHWORTHINESS AND OTHER SAFETY CONSIDERATIONS 65 Note that several of the other Part 25 requirements for cabin crashworthiness that are listed in Box 3-1 do not pertain directly to passenger seats, but the airplane's seating can nevertheless play an important role in enabling compliance. For instance, Part 25 contains performance requirements for an emergency evacuation (§ 25.803) Read the entire page →
From page 66... ... 66 WHEELCHAIR SECUREMENT CONCEPT FOR AIRLINE TRAVEL must be capable of withstanding without structural failure is nine times the combined weight of the seat and a 170-lb occupant. In 1988, a new section, § 25.562, was added that includes dynamic force performance standards for seating systems intended to provide increased occupant protection in survivable crashes. Read the entire page →
From page 67... ... CRASHWORTHINESS AND OTHER SAFETY CONSIDERATIONS 67 head injury criterion (HIC) of 1,000 units is not exceeded.10 The maximum compressive load measured between the pelvis and the lumbar column of the ATD must not exceed 1,500 lb, as protection against a spinal column injury, and axial compressive loads on the femur must not exceed 2,250 lb, as protection against a debilitating leg injury such as through knee contact with seats or other structures in front of the passenger.11 Photos depicting sequences during both types of dynamic tests are shown in Figure 3-1.12 The dynamic testing process is significantly more complicated than the static testing process because the head and leg injury criteria can only be completely evaluated when the seat is considered in relationship to where it is installed in the airplane.13 For example, the testing will cause the upper torso and head to swing forward in an arcing motion because the ATD is constrained only at the pelvis by the safety belt. Read the entire page →
From page 68... ... 68 WHEELCHAIR SECUREMENT CONCEPT FOR AIRLINE TRAVEL Seating systems are also dynamically tested with regard to the integrity and strength of their attachment to the seat tracks and floor beams. When they are being tested in the longitudinal direction, seat tracks and seat attachments that hold the seats to the test fixture must be misaligned with respect to the adjacent set of tracks by at least 10 degrees vertically with one rolled 10 degrees. Read the entire page →
From page 69... ... CRASHWORTHINESS AND OTHER SAFETY CONSIDERATIONS 69 section further states that each occupant of a seat must be protected from head injury by a safety belt (equipped with a metal-to-metal latch) and, as appropriate to the seat's type, location, and facing angle, by one or more of the following: (1) Read the entire page →
From page 70... ... 70 WHEELCHAIR SECUREMENT CONCEPT FOR AIRLINE TRAVEL items of mass is not explicitly mentioned in the § 25.562 requirement for dynamic testing, it is typically demonstrated for seating systems during these tests. Compartment Interiors Flammability (§ 25.853) Read the entire page →
From page 71... ... CRASHWORTHINESS AND OTHER SAFETY CONSIDERATIONS 71 throughout the crash event so that a properly positioned seat belt engages with the strong parts of the occupant's skeletal structure. Accordingly, the seat design should not interfere with proper placement of seat belts or cause failure of belt components during dynamic loading. Read the entire page →
From page 72... ... 72 WHEELCHAIR SECUREMENT CONCEPT FOR AIRLINE TRAVEL wheelchair occupied by a mid-size adult male ATD (approximately 170 lb) to dynamically load the wheelchair and WTORS, respectively. Read the entire page →
From page 73... ... CRASHWORTHINESS AND OTHER SAFETY CONSIDERATIONS 73 Using the same 30-mph, 20-g frontal impact dynamic force test conditions specified in WC18, WC19 requires that a wheelchair perform effectively in a moderate-to-severe frontal crash. The performance criteria are intended to ensure that the structural components of the wheelchair BOX 3-2 RESNA Transportation Requirements for Wheelchairs A wheelchair that complies with the RESNA transportation standard has the following features: • Four permanently labeled, easily accessible securement-point brackets with specific geometry that allows for one-hand attachment of one or two tiedown hooks from tiedown-strap assemblies by a driver or caregiver reaching from one side of the wheelchair; • A base frame and seating system that, along with the four securement points, have been successfully crash tested in a 30-mph, 20-g frontal impact when loaded by an appropriate-size crash test dummy with the wheelchair secured facing forward by a surrogate four-point, strap-type tiedown; • Tiedown strap–clear paths between the securement points on the wheelchair and typical anchor points on the vehicle floor, such that tiedown straps will not be in close proximity to sharp edges (on the wheelchair) Read the entire page →
From page 74... ... 74 WHEELCHAIR SECUREMENT CONCEPT FOR AIRLINE TRAVEL securement points do not fail, the points do not deform in a manner that prevents manual disengagement of the tiedown hook, the wheelchair remains in an upright position, and the occupant remains in a seated posture in the wheelchair seat. The dynamic loading reveals the strength of the wheelchair frame, belts, and securement points, as well as retention of wheelchair components, including the battery. Read the entire page →
From page 75... ... CRASHWORTHINESS AND OTHER SAFETY CONSIDERATIONS 75 considering FAA's concern about passenger seat cabin interior flammability. Because all wheelchairs must meet WC16 and other standards for everyday usage, wheelchairs labeled as compliant with WC19 will also comply with WC16, and WC19 includes this flammability testing requirement. Read the entire page →
From page 76... ... 76 WHEELCHAIR SECUREMENT CONCEPT FOR AIRLINE TRAVEL airplane seats and cabins, and of RESNA, with respect to wheelchairs used as seats in motor vehicles. COMPARISON OF FAA AND RESNA CRASHWORTHINESS CRITERIA As is clear from the discussion above, most FAA Part 25 regulations are performance based; for instance, § 25.561 and § 25.562 specify the forces or accelerations that a seating system must be capable of withstanding without excessive deformation (i.e., to the point where the seat could impede evacuation) Read the entire page →
From page 77... ... CRASHWORTHINESS AND OTHER SAFETY CONSIDERATIONS 77 not specify occupant injury criteria in the same manner as § 25.562.19 The WC18 and WC19 standards assume that sufficient clear space will be provided in front of the wheelchair so there is less risk of secondary head and leg injuries to a properly belted occupant. Thus, whereas head, torso, and leg injury measures are often collected from the ATD during WTORS and wheelchair testing, they are not used specifically for assessing compliance with WC18 and WC19. Read the entire page →
From page 78... ... 78 WHEELCHAIR SECUREMENT CONCEPT FOR AIRLINE TRAVEL requirements but without testing or other evaluation data. All WC19compliant wheelchairs must meet WC16, which specifies performance tests for demonstrating the resistance of the wheelchair seating and upholstery materials to ignition by a cigarette and match. Read the entire page →
From page 79... ... CRASHWORTHINESS AND OTHER SAFETY CONSIDERATIONS 79 restraint system that includes both pelvic and upper torso safety belts; however, if such an installation is not possible, WC19 also prescribes a pelvic belt that can be anchored to the wheelchair. As described earlier, WC19compliant chairs have been crash tested with a wheelchair-anchored pelvic belt, and pelvic belts without shoulder belts are the norm for conventional airplane passenger seats. Read the entire page →
From page 80... ... 80 WHEELCHAIR SECUREMENT CONCEPT FOR AIRLINE TRAVEL The removal of these assemblies would also free up floor seat track attachment points, which would be needed to provide structural load bearing capacity for a secured wheelchair and securement system. The occupied weight of the wheelchair relevant to the occupied weight of the displaced seat assemblies is therefore an important consideration for assessing whether the removal of two seat assemblies for a securement zone would provide sufficient seat track connections for load bearing capacity. Read the entire page →
From page 81... ... CRASHWORTHINESS AND OTHER SAFETY CONSIDERATIONS 81 technical matter that would require more thorough engineering analysis to reach definitive conclusions about floor structural capacity and the viability of using typical systems for load distribution.24 24 In public information-gathering sessions, the committee heard from engineering and other experts from individual airlines, an airplane manufacturer, and airplane seat and cabin interior designers. Hans-Gerhard Giesa and Ralf Schliwa of Airbus stated that there would likely be "no need for changes in aircraft structure" to accommodate dynamic loads. Read the entire page →
From page 82... ... 82 WHEELCHAIR SECUREMENT CONCEPT FOR AIRLINE TRAVEL Finally, the issue of power wheelchair batteries and any hazards that they may create in the cabin will warrant attention, both with regard to a fire hazard and retention of items of mass during an emergency landing or crash. With regard to a fire hazard, most power wheelchairs use lead-acid sealed batteries but other battery types are in use, including nickel metal hydride and lithium ion batteries. Read the entire page →
From page 83... ... CRASHWORTHINESS AND OTHER SAFETY CONSIDERATIONS 83 wheelchair's battery does not become dislodged in a frontal motor vehicle crash. As noted above, WC19's 20-g frontal crash test bears a resemblance to FAA's 16-g longitudinal test for airplane seats. Read the entire page →
From page 84... ... 84 WHEELCHAIR SECUREMENT CONCEPT FOR AIRLINE TRAVEL attached to the airplane structure, do not deform to impede evacuation, and protect the occupant from serious injuries. They contain specific criteria for head, spinal, and leg injuries when tested according to the dynamic loading conditions intended to simulate airplane crash scenarios. Read the entire page →
From page 85... ... CRASHWORTHINESS AND OTHER SAFETY CONSIDERATIONS 85 including evaluations conducted for the purpose of strengthening their safety performance in an airplane environment and for supporting decisions by FAA about needed crashworthiness demonstration. Guidance in the WC18 standard for forward-facing wheelchair securements in a motor vehicle suggests that a 30- × 60-in. Read the entire page →

From page 61...

... 61 3 Crashworthiness and Other Safety Considerations With the exception of regulations governing school bus passenger transportation and crash protection,1 the federal government has not established safety standards that apply to wheelchair securement systems or wheelchairs used as seats in surface transportation vehicles or airplanes.2 Nevertheless, wheelchairs and securement systems that are designed and constructed according to voluntary industry standards intended to ensure safer transportation for people who must use their personal wheelchairs as seats in motor vehicles are currently in use. As explained in Chapter 2, the standards are issued by the Rehabilitation Engineering and Assistive Technology Society of North America (RESNA)