NASA crashes 172s to improve ELTs

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A Cessna 172 has been dropped from 100ft to test the crashworthiness of emergency locator transmitters.

The crash test, performed at NASA’s Landing and Impact Research Facility, was the second time in just a few weeks that a 172 had been sacrificed to collect data to be used in improving the reliability of emergency locator transmitters (ELTs).

Designed to be automatically activated in the event of a crash, ELTs alert search and rescue authorities and provide the location of the downed aircraft. However, ELTs are often so damaged they sometimes fail to transmit as intended, making it harder for search teams to reach the crash site quickly.

The first test in the series dropped the Cessna from a lesser height, 82ft, on to concrete instead of soil, but with vastly different results, as the video below shows.

Intuition might lead you to think that dirt would provide a softer landing than concrete, but according to Chad Stimson, NASA’s project manager, that’s not the case. ‘It’s actually worse,’ he said. ‘On concrete, an aircraft is more apt to skid forward, dissipating some of the energy.’

But on soil, the aircraft is forced to stop more suddenly, ‘so all that force is absorbed by the airframe and the occupants’, Stimson said. ‘This was clearly more severe than the first test. No one would have walked away from this. They might be alive, but they’d need help right away. In that sense, it’s the perfect search and rescue case.’

Data gathered from the tests will lead to better guidance on how to install the systems so they’re more likely to work after a crash.

‘Too often they fail to work as expected; in part, because of inadequate performance specifications in several areas including vibration, fire survivability, automatic activation, crash safety and system installation,’ says Stimson.

Colliding with the soil at nearly 55 miles per hour, the crash was recorded across 64 data channels with 40 cameras capturing images and video footage.

You can read more about the Emergency Locator Transmitter Survivability and Reliability (ELTSAR) project via the NASA website.

2 COMMENTS

  1. When spoke with an air services guy some time back he professed no knowledge of the problems with ELTs not working as advertised and thus not transmitting a signal. Now the FAA has come out and said what whispers have said for some time.
    Good to see that the FAA is trying to ensure that future ELTs are designed such that they work on a crash impact but not in just a heavy landing. A grey area.

  2. These two tests reveal more about the importance of the angle of incidence as the aircraft struck the ground, than they do about the surface being struck. For whatever reason, the “concrete” aircraft reached the ground almost “flat’ – in cruise attitude – taking all the force on the (much stronger and shock-absorbing) back wheels.
    The “sand” aircraft was already in nose-down attitude on arrival, taking the full force of impact on the (much weaker) nose wheel, which collapsed immediately and the aircraft remained nose-down.
    I suspect that if both aircraft had identical angles of incidence on touchdown, the nose wheel would still collapse for both aircraft, the sand aircraft would still flip over, but a lot of the force would be taken by those back wheels and the occupants would have survived – perhaps with less back trouble than the concrete aircraft, due to the cushioning of the sand!
    What do you think?

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