Lift, camera, action! Dropping aircraft and crash test dummy development
Crash testing has come a long way from the early 1940s, when cadavers and volunteers were used in rapid deceleration tests on tracks designed for Nazi V-1 rocket testing. The modern Anthropomorphic Test Dummy (ATD) contains multiple load cells that record data on up to six force/torque axes. They are typically situated in the head and neck areas, the thorax, abdomen and legs.
Unfortunately, until recently, EuroNCAP and US equivalent crash test dummies only came in three sizes:
- 95th percentile male
- 50th percentile male
- 5th percentile female
Since the 1970s, the female crash test dummy, (the “5th percentile female) was just a scaled down version of the male test dummy, being 152cm tall and weighing just 50kg. That made the dummy the size of the average 12 year old girl. It therefore did not account for the different shapes of teenage and adult female bodies.
That all changed in October 2022 when a team of Swedish engineers designed the first crash test dummy that matched the size, weight and body shape of an average woman. This new female crash test dummy measures 162cm tall and weights 62kg.
According to an article in Ingenia, the Royal Academy of Engineering magazine (1):
“Although these dummies are not yet a legal requirement for user tests such as Euro NCAP, Humanetics has developed dummies that represent road users who are ‘elderly’, ‘large and obese’, children of different sizes, and a 5th percentile female dummy with an adult woman’s shape. … It is vital that engineers working in crash testing and vehicle safety policy are representative for the full spectrum of road users, to make everyone as safe as their ‘50th percentile male’ counterparts.”
Crash testing at NASA
NASA’s Landing and Impact Research Facility at Langley includes a massive steel gantry, originally used to train Apollo astronauts to land on the moon. In the 1970s, the massive 240ft high structure was used to establish aviation crash testing techniques.
Such is the importance of testing here that the gantry is a US national historic monument, and the data collected is the backbone of many aviation safety standards. As Dr Justin Littell, NASA’s lead researcher, explained in an article for Aerospace Testing International:
“One of the major developments that came out of here was the dynamic seat test. They carried out several full-scale crash tests here and with that data worked out the qualification standards for seats.”
Aviation crash testing: lift and drop
At its heart, a crash test from the gantry is pretty basic; they take a section of aircraft, hoist it up and then drop it 150 feet onto a bed of packed earth. What made their recent test of a Fokker F-28 jet was the installation of ultra-high-speed cameras, capable of half a million frames per second, to record every element of the plane during the drop.
This included the effect of the impact on the crash test dummies seated in the plane. The dummies were kitted out with load cells in the spinal column and neck, measuring force that would indicate compression in the spine or whiplash in the back.
In the NASA Fokker aircraft test, they used 50th Percentile dummies. NASA’s sophisticated dummies do not come cheap, and you wouldn’t get much change from US$500,0000 for one fully kitted out with sensors.
Sitting pretty: load cells and seat testing
The dummies also had cameras trained on them inside the cabin. Cameras were mounted using a gimbal system and were capable of withstanding high levels of g-force. These cameras enabled the test team to correlate their data from the sensors within the dummy with physical movements the dummies make during free fall and impact. As Dr Littel explained:
“The camera can show you that a dummy sunk in its seat and that’s why there’s a high load measurement on the load cell. It is able to give us a complete picture of what the dummies experience on board.”
The myriad of sensors inside the plane were supplemented with a digital image correlation (DIC) pattern painted on the exterior consisting of black dots. Cameras are set up to track the movements of the dots, and therefore researchers can see precisely how much the plane deforms and strains on impact.
The whole test took over a year to plan, and the data collected will inform the next generation of simulated flight testing, Which, ironically, might eventually make the NASA Langley gantry redundant.
A growth area of destructive testing
Impact testing using crash test dummies is an ever-developing area of destructive testing that includes road vehicles as well as rail, aircraft and even wheelchairs. The Global Vehicle Target for testing of autonomous emergency braking systems was introduced in 2014. However, as vehicle design move towards greater autonomy, testing will also need to include many more variables of passenger position than the standard seated facing forward we currently test for.
Impact testing stats
The Ingenia article also revealed some fascinating facts about modern crash testing including:
- It take 3-4 days to prepare for a single text
- A frontal impact test from 80metres must impact a barrier within a 20mm tolerance
- The average crash duration is just 200 milliseconds
- Data analysis from the multiple sensors can take several days
Load cells for all types of destructive testing
Our load cells are used extensively in materials testing from thin films to innovative composites and prototype products. Whatever you wish to test to destruction, our load cells can provide accurate, continual data throughout the testing process. Contact us to discuss your requirements, or browse our online shop.
