Commercial air travel remains the safest mode of transport available in OECD countries. Commercial airlines in Australia do not require infants under the age of 24 months to occupy their own seats during flight. However, the children carried in the arms of adult passengers must be restrained during taxi, take-off, landing and turbulence.
The aims of this project were to review the developments in safe transport of children in aircraft and to conduct a test program based on current Australian child restraint systems (CRS). This initial program was later extended to include the assessment of infant carrier systems (commonly referred to as baby slings) for use as infant restraints in aircraft.
A US Civil Aerospace Medical Institute (CAMI) study found that lap-held restraint systems allowed excessive forward body excursion of the test dummies, resulting in severe head impact with the seat back directly in front. The tests showed how a lap-held infant could be crushed between the forward seat back and the accompanying adult during impact (Gowdy & De Weese 1994). Following the CAMI study, the US Federal Aviation Administration (FAA) banned the use of booster seats and all lap-held restraint devices in aircraft during take-off, landing and taxi. This has resulted in lap-held children travelling wholly unrestrained in aircraft.
The travelling public is likely to expect that the level of safety offered to child passengers in commercial aircraft is equivalent to that of adult passengers restrained by lap belts. The use of an appropriate child restraint system can offer the highest level of safety for young children travelling in aircraft, both in turbulence and in crash situations. However, the compatibility of current Australian automotive CRS with aircraft seating has not been investigated and their performance in aircraft emergency situations is unknown.
There are very few preventable child deaths in aircraft crashes. Newman, Johnston and Grossman (2003) found that the use of CRS would prevent 0.4 child air-crash deaths per year. They concluded that making infant air-seats compulsory would raise air travel costs which could result in a net increase in deaths and injuries as families opt for automobile travel - a higher-risk mode of transport per kilometre of travel.
Child restraint testing
A selection of automotive CRS available in Australia was chosen for testing in this study to cover the range of common child restraint types. The DME Corporation PlaneSeat, certified for use in both motor vehicles and aircraft in the United States, was also examined. The testing was completed in three stages:
The CRS were fitted to an economy class aircraft seat row to check for compatibility. Twenty Australian standard CRS were fitted to the aircraft seat according to the manufacturer's instructions. Fourteen of the CRS models had problems in this test. Either they did not fit within the 31-inch seat pitch or they were difficult to fit due to interference with the latching mechanism of the aircraft seat lap belt. One restraint was designed for use only with a top tether strap requiring an anchorage system not available in commercial aircraft.
Turbulence (inversion) test
The CRS were subjected to the FAA seat inversion test for turbulence. This test caused no difficulty for the Australian CRS, which have 6-point harnesses for the child. Booster seats were not tested in this series.
- Dynamic sled test
The Australian automotive CRS were subjected to the requirements of the dynamic FAA aircraft seat test, without the top tether normally required in motor vehicle installation. The CRS were installed on a single aircraft seat row by the lap belt and subjected to a 16G longitudinal test with a velocity change of more than 45 km/h. Forty-two sled tests were conducted involving 11 models of Australian CRS together with tests where dummies were restrained only by the aircraft seat lap belt. The average sled deceleration for the tests was 18.9G and the mean entry velocity was 47.6 km/h.
The dummies were retained in the CRS in all sled tests. However, all the CRS exhibited significant forward motion, rotation, and rebound motion. This less controlled movement, in comparison with typical automotive testing of CRS, was due to the following:
- the upper tether could not be installed;
- the more vertical geometry of the aircraft seat lap belt;
- the poor compatibility of the aircraft seat lap belt design and the CRS belt paths;
- the poor interaction of the CRS with the aircraft seat base cushion and frame;
- a rebound phase that was poorly controlled due to the more extensive forward motion of the CRS.
In tests where the child dummies were restrained only by the aircraft seat lap belt, excessive forward motion of the dummy head and torso occurred due to the lack of upper body restraint and the folding over of the aircraft seat back. This motion is likely to result in impact with the forward seat back.
Infant carrier testing
Four commercially available infant carriers were chosen as representative and were tested to evaluate their performance with respect to retention of the child, forward excursion, and crushing by the adult. Two samples of the standard 'supplementary loop belts' (or belly belts) were included for comparative testing. The testing was conducted in two stages:
Turbulence (inversion) test
The infant carriers were subjected to an inversion test to simulate turbulent conditions. An infant dummy was placed in the carrier and fitted to an adult dummy restrained by a lap belt in an aircraft seat. The tests demonstrated that infants could be adequately restrained when exposed to 1G of vertical acceleration provided the carrier was securely fastened.
A lap-belt restrained adult dummy in an aircraft seat, with an infant dummy in a carrier, was subjected to a 9G dynamic sled test. The severity of the pulse was based on the results of a static load test. The commercially available infant carriers tested were not able to restrain infants under crash situations.
The infant carriers could be redesigned to ensure that the infant was restrained in dynamic loads equivalent to the test pulse. If this was done, then an infant carrier would form an alternative to the supplementary loop belt.
The following suggestions are made based on the findings of this study and the principle that infants and young children are entitled to the same level of protection, both in flight and during emergency landing situations, that is afforded to adults.
The use of CRS by infants and young children on flights in Australia is to be encouraged. The CRS used could be either designed specifically for use in aircraft, or, Australian automotive CRS approved for use in aircraft as per suggestion number 3.
Testing should be conducted of the system of an upper tether strap for Australian automotive CRS with a non-breakover aircraft seat back, as currently used by Qantas.
An approval system should be established to ensure that any Australian automotive CRS to be used in aircraft fits in the aircraft seat and is compatible with the aircraft lap belt. The approval could be in the form of an extra test added to the existing motor vehicle requirements similar to the FAA approval system.
Improvements in the crash performance of Australian automotive CRS in aircraft could be achieved by making changes to the seating systems in the aircraft to minimise forward excursion of the CRS in the seat. In order of priority, these suggested improvements are:
Supply a properly mounted upper tether, either as used by Qantas should testing show that this is effective or, by supplying attachment points in the aircraft for CRS use. This could be achieved by restricting CRS use to the seats forward of a bulkhead and by requiring a modified bulkhead design with appropriate attachment points built in for the tether.
Change lap belt geometry (angled at 45 to 60 degrees instead of vertical) for use with a CRS to reduce the initial forward excursion of the base. However, such seat belt geometry may not be appropriate for other users of the belt.
Make changes to the seat base cushion to ensure its retention under CRS dynamic loads.
- Improvements in the crash protection offered in aircraft to an infant seated on the lap of an adult could be achieved if some seats were fitted with lap sash or harness type seat belts for use by parents holding infants. These seats, possibly adjacent to a bulkhead could be forward- or rearward-facing. Controlling the upper torso motion of the adult has the potential to reduce crash loading to an infant seated on the lap of an adult.
If suggestion 5 was implemented, then an approval system for infant carriers (slings) for use in aircraft should be put in place. A sling system could be designed and developed as a replacement for the belly belt. This type of infant carrier could offer improved retention and comfort in turbulent conditions; in conjunction with appropriate seating fitted with a lap/sash or harness for the parent, it could offer improved safety for the infant in a crash.
The changes resulting from the incorporation of ISO rigid anchorage systems (ISO-fix or latch systems), which are becoming mandatory worldwide, need to be studied and accommodated for use in aircraft.
|Type:||Research and Analysis Report|
|Author(s):||Gibson, T, Thai, K and Lumley, M|
|Publication date:||21 March 2006|