This Time, Helo Fuselage Was Dropped Without The 'Airbag'

A second crash test of a small lightweight helicopter at NASA's Langley Research Center in Hampton, VA, produced the results that engineers expected ... the aircraft was badly damaged and the occupants would have suffered severe injuries.

NASA Photo

The helicopter fuselage was dropped from a height of 35 feet at a steep angle of descent. It smacked hard into the concrete, the skid gear collapsed, its windscreen cracked open and its occupants lurched forward violently, suffering potentially spine-crushing injuries according to internal data recorders. The crash test was all in the name of research to try to make helicopters safer.

"The goal of any research program that has an element of impact dynamics is to develop an understanding of the crash response of the vehicle," said Karen Jackson, an aerospace engineer who oversaw the test. "Once we understand that response we can look at ways to improve the crash performance."

NASA Photo

In December 2009 researchers dropped the same MD-500 fuselage at a similar angle from the same height. Inside were the same instruments that collected 160 channels of data and the same four crash test dummies. Three of the dummies were full bodies and one was a special torso model equipped with simulated internal organs. Technicians set up the same cameras to record the impact from inside and outside the helicopter. But in the first test, the MD-500 skidded to a stop, with very little damage to the helicopter or its silent occupants, because its underside was outfitted with an expandable honeycomb cushion called a deployable energy absorber.

"It's made of Kevlar and has a unique flexible hinge design that allows the honeycomb to be packaged and remain flat until needed," said Sotiris Kellas, the Langley engineer who created the idea as a way to cushion the next generation of astronaut-carrying space capsules, but realized it could be used in other ways.

The test conditions on both days were the same, simulating what would be a relatively severe but survivable helicopter crash. The flight path angle was about 33 degrees and the combined forward and vertical speeds were about 48 feet per second or 33 miles per hour.

NASA Photo

The more recent drop test on March 10 involved just the helicopter. No new technology was attached, and that was the point. Engineers wanted to determine exactly how efficient the deployable energy absorber had been in the earlier test and how much it might help reduce occupant injuries. So they dropped the same helicopter in the same way and measured and recorded the same conditions with the same instruments.

"We were fortunate enough that the helicopter survived so well the first time that we could use it again," said engineer Martin Annett.

There will be no third crash test for this helicopter. Researchers say the "g" forces the MD-500 experienced more than tripled those recorded in the previous test, and the aircraft was too badly damaged. But engineers still have gigabytes of data to analyze to confirm exactly what impact the new honeycomb cushion technology might have for helicopters in the future.

The drop tests were conducted by the Subsonic Rotary Wing Project of NASA's Fundamental Aeronautics Program, and funded by the agency's Aeronautics Research Mission Directorate in Washington.

FMI: www.nasa.gov